Comparison of winter wheat yield sensitivity to climate variables under irrigated and rain-fed conditions

NASA Astrophysics Data System (ADS)

Xiao, Dengpan; Shen, Yanjun; Zhang, He; Moiwo, Juana P.; Qi, Yongqing; Wang, Rende; Pei, Hongwei; Zhang, Yucui; Shen, Huitao

2016-09-01

Crop simulation models provide alternative, less time-consuming, and cost-effective means of determining the sensitivity of crop yield to climate change. In this study, two dynamic mechanistic models, CERES (Crop Environment Resource Synthesis) and APSIM (Agricultural Production Systems Simulator), were used to simulate the yield of wheat ( Triticum aestivum L.) under well irrigated (CFG) and rain-fed (YY) conditions in relation to different climate variables in the North China Plain (NCP). The study tested winter wheat yield sensitivity to different levels of temperature, radiation, precipitation, and atmospheric carbon dioxide (CO2) concentration under CFG and YY conditions at Luancheng Agro-ecosystem Experimental Stations in the NCP. The results from the CERES and APSIM wheat crop models were largely consistent and suggested that changes in climate variables influenced wheat grain yield in the NCP. There was also significant variation in the sensitivity of winter wheat yield to climate variables under different water (CFG and YY) conditions. While a temperature increase of 2°C was the threshold beyond which temperature negatively influenced wheat yield under CFG, a temperature rise exceeding 1°C decreased winter wheat grain yield under YY. A decrease in solar radiation decreased wheat grain yield under both CFG and YY conditions. Although the sensitivity of winter wheat yield to precipitation was small under the CFG, yield decreased significantly with decreasing precipitation under the rainfed YY treatment. The results also suggest that wheat yield under CFG linearly increased by ≈3.5% per 60 ppm (parts per million) increase in CO2 concentration from 380 to 560 ppm, and yield under YY increased linearly by ≈7.0% for the same increase in CO2 concentration.

Sensitivity of the regional climate in the Middle East and North Africa to volcanic perturbations

NASA Astrophysics Data System (ADS)

Dogar, Muhammad Mubashar; Stenchikov, Georgiy; Osipov, Sergey; Wyman, Bruce; Zhao, Ming

2017-08-01

The Middle East and North Africa (MENA) regional climate appears to be extremely sensitive to volcanic eruptions. Winter cooling after the 1991 Pinatubo eruption far exceeded the mean hemispheric temperature anomaly, even causing snowfall in Israel. To better understand MENA climate variability, the climate responses to the El Chichón and Pinatubo volcanic eruptions are analyzed using observations, NOAA/National Centers for Environmental Prediction Climate Forecast System Reanalysis, and output from the Geophysical Fluid Dynamics Laboratory's High-Resolution Atmospheric Model. A multiple regression analysis both for the observations and the model output is performed on seasonal summer and winter composites to separate out the contributions from climate trends, El Niño-Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Indian summer monsoon, and volcanic aerosols. Strong regional temperature and precipitation responses over the MENA region are found in both winter and summer. The model and the observations both show that a positive NAO amplifies the MENA volcanic winter cooling. In boreal summer, the patterns of changing temperature and precipitation suggest a weakening and southward shift of the Intertropical Convergence Zone, caused by volcanic surface cooling and weakening of the Indian and West African monsoons. The model captures the main features of the climate response; however, it underestimates the total cooling, especially in winter, and exhibits a different spatial pattern of the NAO climate response in MENA compared to the observations. The conducted analysis sheds light on the internal mechanisms of MENA climate variability and helps to selectively diagnose the model deficiencies.

Winter Ecology.

ERIC Educational Resources Information Center

Birkeland, Karl W.; Halfpenny, James C.

1987-01-01

Discusses some of the ecological variables involved with plant and animal survival during the winter months. Addresses the effects of changing climatic conditions on habitats, foot-loading indexes, and the overall concept of adaptation. Provides some simple teaching activities dealing with winter survival. (TW)

Internal Variability-Generated Uncertainty in East Asian Climate Projections Estimated with 40 CCSM3 Ensembles.

PubMed

Yao, Shuai-Lei; Luo, Jing-Jia; Huang, Gang

2016-01-01

Regional climate projections are challenging because of large uncertainty particularly stemming from unpredictable, internal variability of the climate system. Here, we examine the internal variability-induced uncertainty in precipitation and surface air temperature (SAT) trends during 2005-2055 over East Asia based on 40 member ensemble projections of the Community Climate System Model Version 3 (CCSM3). The model ensembles are generated from a suite of different atmospheric initial conditions using the same SRES A1B greenhouse gas scenario. We find that projected precipitation trends are subject to considerably larger internal uncertainty and hence have lower confidence, compared to the projected SAT trends in both the boreal winter and summer. Projected SAT trends in winter have relatively higher uncertainty than those in summer. Besides, the lower-level atmospheric circulation has larger uncertainty than that in the mid-level. Based on k-means cluster analysis, we demonstrate that a substantial portion of internally-induced precipitation and SAT trends arises from internal large-scale atmospheric circulation variability. These results highlight the importance of internal climate variability in affecting regional climate projections on multi-decadal timescales.

Characteristics of the East Asian Winter Climate Associated with the Westerly Jet Stream and ENSO

NASA Technical Reports Server (NTRS)

Yang, Song; Lau, K.-M.; Kim, K.-M.; Einaudi, Franco (Technical Monitor)

2000-01-01

In this study, the influences of the East Asian jet stream (EAJS) and El Nino/Southern Oscillation (ENSO) on the interannual variability of the East Asian winter climate are examined with a focus on the relative climate impacts of the two phenomena. Although the variations of the East Asian winter monsoon and the temperature and precipitation of China, Japan, and Korea are emphasized, the associated changes in the broad-scale atmospheric circulation patterns over Asia and the Pacific and in the extratropical North Pacific sea surface temperature (SST) are also investigated. It is demonstrated that there is no apparent relationship between ENSO and the interannual variability of EAJS core. The EAJS and ENSO are associated with distinctly different patterns of atmospheric circulation and SST in the Asian-Pacific regions. While ENSO causes major climate signals in the Tropics and over the North Pacific east of the dateline, the EAJS produces significant changes in the atmospheric circulation over East Asia and western Pacific. In particular, the EAJS explains larger variance of the interannual signals of the East Asian trough, the Asian continental high, the Aleutian low, and the East Asian winter monsoon. When the EAJS is strong, all these atmospheric systems intensify significantly. The response of surface temperature and precipitation to EAJS variability and ENSO is more complex. In general, the East Asian winter climate is cold (warm) and dry (wet) when the EAJS is strong (weak) and it is warm during El Nino years. However, different climate signals are found during different La Nina years. In terms of linear correlation, both the temperature and precipitation of northern China, Korea, and central Japan are more significantly associated with the EAJS than with ENSO.

Climate variability from the Florida Bay sedimentary record: Possible teleconnections to ENSO, PNA and CNP

USGS Publications Warehouse

Cronin, T. M.; Dwyer, Gary S.; Schwede, S.B.; Vann, C.D.; Dowsett, H.

2002-01-01

We analyzed decadal and interannual climate variability in South Florida since 1880 using geochemical and faunal paleosalinity indicators from isotopically dated sediment cores at Russell Bank in Florida Bay (FB). Using the relative abundance of 2 ostracode species and the Mg/Ca ratios in Loxoconcha matagordensis shells to reconstruct paleosalinity, we found evidence for cyclic oscillations in the salinity of central FB. During this time salinity fluctuated from as low as ~18 parts per thousand (ppt) to as high as ~57 ppt. Time series analyses suggest, in addition to a 5.6 yr Mg/Ca based salinity periodicity, there are 3 other modes of variability in paleosalinity indicators: 6-7, 8-9, and 13-14 yr periods which occur in all paleo-proxies. To search for factors that might cause salinity to vary in FB, we compared the Russell Bank paleosalinity record to South Florida winter rainfall, the Southern Oscillation Index (SOI), winter North Atlantic Oscillation (NAO), and the winter Pacific North American (PNA) index, and a surrogate for the PNA in the winter season, the Central North Pacific (CNP) index. SOI and PNA/CNP appear to be associated with South Florida winter precipitation. Time series analyses of SOI and winter rainfall for the period 1910-1999 suggest ~5, 6-7, 8-9 and 13-14 yr cycles. The 6-7 yr and 13-14 yr cycles correspond to those observed in the faunal and geochemical time series from Russell Bank. The main periods of the CNP index are 5-6 and 13-15 yr, which are similar to those observed in FB paleosalinity. Cross-spectral analyses show that winter rainfall and salinity are coherent at 5.6 yr with a salinity lag of ~1.6 mo. These results suggest that regional rainfall variability influences FB salinity over interannual and decadal timescales and that much of this variability may have its origin in climate variability in the Pacific Ocean/atmosphere system.

Importance of climatological downscaling and plant phenology for red deer in heterogeneous landscapes

PubMed Central

Pettorelli, Nathalie; Mysterud, Atle; Yoccoz, Nigel G; Langvatn, Rolf; Stenseth, Nils Chr

2005-01-01

Understanding how climate influences ecosystems represents a challenge in ecology and natural resource management. Although we know that climate affects plant phenology and herbivore performances at any single site, no study has directly coupled the topography–climate interaction (i.e. the climatological downscaling process) with large-scale vegetation dynamics and animal performances. Here we show how climatic variability (measured by the North Atlantic oscillation ‘NAO’) interacts with local topography in determining the vegetative greenness (as measured by the normalized difference vegetation index ‘NDVI’) and the body masses and seasonal movements of red deer (Cervus elaphus) in Norway. Warm springs induced an earlier onset of vegetation, resulting in earlier migration and higher body masses. Increasing values of the winter-NAO corresponded to less snow at low altitude (warmer, more precipitation results in more rain), but more snow at high altitude (colder, more precipitation corresponds to more snow) relative to winters with low winter-NAO. An increasing NAO thus results in a spatially more variable phenology, offering migrating deer an extended period with access to high-quality forage leading to increased body mass. Our results emphasize the importance of incorporating spring as well as the interaction between winter climate and topography when aiming at understanding how plant and animal respond to climate change. PMID:16243701

Faithful or not: direct and indirect effects of climate on extra-pair paternities in a population of Alpine marmots

PubMed Central

Allainé, Dominique; Sauzet, Sandrine; Cohas, Aurélie

2016-01-01

Despite being identified an area that is poorly understood regarding the effects of climate change, behavioural responses to climatic variability are seldom explored. Climatic variability is likely to cause large inter-annual variation in the frequency of extra-pair litters produced, a widespread alternative mating tactic to help prevent, correct or minimize the negative consequences of sub-optimal mate choice. In this study, we investigated how climatic variability affects the inter-annual variation in the proportion of extra-pair litters in a wild population of Alpine marmots. During 22 years of monitoring, the annual proportion of extra-pair litters directly increased with the onset of earlier springs and indirectly with increased snow in winters. Snowier winters resulted in a higher proportion of families with sexually mature male subordinates and thus, created a social context within which extra-pair paternity was favoured. Earlier spring snowmelt could create this pattern by relaxing energetic, movement and time constraints. Further, deeper snow in winter could also contribute by increasing litter size and juvenile survival. Optimal mate choice is particularly relevant to generate adaptive genetic diversity. Understanding the influence of environmental conditions and the capacity of the individuals to cope with them is crucial within the context of rapid climate change. PMID:28003452

Faithful or not: direct and indirect effects of climate on extra-pair paternities in a population of Alpine marmots.

PubMed

Bichet, Coraline; Allainé, Dominique; Sauzet, Sandrine; Cohas, Aurélie

2016-12-28

Despite being identified an area that is poorly understood regarding the effects of climate change, behavioural responses to climatic variability are seldom explored. Climatic variability is likely to cause large inter-annual variation in the frequency of extra-pair litters produced, a widespread alternative mating tactic to help prevent, correct or minimize the negative consequences of sub-optimal mate choice. In this study, we investigated how climatic variability affects the inter-annual variation in the proportion of extra-pair litters in a wild population of Alpine marmots. During 22 years of monitoring, the annual proportion of extra-pair litters directly increased with the onset of earlier springs and indirectly with increased snow in winters. Snowier winters resulted in a higher proportion of families with sexually mature male subordinates and thus, created a social context within which extra-pair paternity was favoured. Earlier spring snowmelt could create this pattern by relaxing energetic, movement and time constraints. Further, deeper snow in winter could also contribute by increasing litter size and juvenile survival. Optimal mate choice is particularly relevant to generate adaptive genetic diversity. Understanding the influence of environmental conditions and the capacity of the individuals to cope with them is crucial within the context of rapid climate change. © 2016 The Author(s).

Climate change. Six centuries of variability and extremes in a coupled marine-terrestrial ecosystem.

PubMed

Black, Bryan A; Sydeman, William J; Frank, David C; Griffin, Daniel; Stahle, David W; García-Reyes, Marisol; Rykaczewski, Ryan R; Bograd, Steven J; Peterson, William T

2014-09-19

Reported trends in the mean and variability of coastal upwelling in eastern boundary currents have raised concerns about the future of these highly productive and biodiverse marine ecosystems. However, the instrumental records on which these estimates are based are insufficiently long to determine whether such trends exceed preindustrial limits. In the California Current, a 576-year reconstruction of climate variables associated with winter upwelling indicates that variability increased over the latter 20th century to levels equaled only twice during the past 600 years. This modern trend in variance may be unique, because it appears to be driven by an unprecedented succession of extreme, downwelling-favorable, winter climate conditions that profoundly reduce productivity for marine predators of commercial and conservation interest. Copyright © 2014, American Association for the Advancement of Science.

A chrysophyte-based quantitative reconstruction of winter severity from varved lake sediments in NE Poland during the past millennium and its relationship to natural climate variability

NASA Astrophysics Data System (ADS)

Hernández-Almeida, I.; Grosjean, M.; Przybylak, R.; Tylmann, W.

2015-08-01

Chrysophyte cysts are recognized as powerful proxies of cold-season temperatures. In this paper we use the relationship between chrysophyte assemblages and the number of days below 4 °C (DB4 °C) in the epilimnion of a lake in northern Poland to develop a transfer function and to reconstruct winter severity in Poland for the last millennium. DB4 °C is a climate variable related to the length of the winter. Multivariate ordination techniques were used to study the distribution of chrysophytes from sediment traps of 37 low-land lakes distributed along a variety of environmental and climatic gradients in northern Poland. Of all the environmental variables measured, stepwise variable selection and individual Redundancy analyses (RDA) identified DB4 °C as the most important variable for chrysophytes, explaining a portion of variance independent of variables related to water chemistry (conductivity, chlorides, K, sulfates), which were also important. A quantitative transfer function was created to estimate DB4 °C from sedimentary assemblages using partial least square regression (PLS). The two-component model (PLS-2) had a coefficient of determination of Rcross2 = 0.58, with root mean squared error of prediction (RMSEP, based on leave-one-out) of 3.41 days. The resulting transfer function was applied to an annually-varved sediment core from Lake Żabińskie, providing a new sub-decadal quantitative reconstruction of DB4 °C with high chronological accuracy for the period AD 1000-2010. During Medieval Times (AD 1180-1440) winters were generally shorter (warmer) except for a decade with very long and severe winters around AD 1260-1270 (following the AD 1258 volcanic eruption). The 16th and 17th centuries and the beginning of the 19th century experienced very long severe winters. Comparison with other European cold-season reconstructions and atmospheric indices for this region indicates that large parts of the winter variability (reconstructed DB4 °C) is due to the interplay between the oscillations of the zonal flow controlled by the North Atlantic Oscillation (NAO) and the influence of continental anticyclonic systems (Siberian High, East Atlantic/Western Russia pattern). Differences with other European records are attributed to geographic climatological differences between Poland and Western Europe (Low Countries, Alps). Striking correspondence between the combined volcanic and solar forcing and the DB4 °C reconstruction prior to the 20th century suggests that winter climate in Poland responds mostly to natural forced variability (volcanic and solar) and the influence of unforced variability is low.

European seasonal mortality and influenza incidence due to winter temperature variability

NASA Astrophysics Data System (ADS)

Rodó, X.; Ballester, J.; Robine, J. M.; Herrmann, F. R.

2017-12-01

Recent studies have vividly emphasized the lack of consensus on the degree of vulnerability (sensu IPCC) of European societies to current and future winter temperatures. Here we consider several climate factors, influenza incidence and daily numbers of deaths to characterize the relationship between winter temperature and mortality in a very large ensemble of European regions representing more than 400 million people. Analyses highlight the strong association between the year-to-year fluctuations in winter mean temperature and mortality, with higher seasonal cases during harsh winters, in all of the countries except the United Kingdom, the Netherlands and Belgium. This spatial distribution contrasts with the well-documented latitudinal orientation of the dependency between daily temperature and mortality within the season. A theoretical framework is proposed to reconcile the apparent contradictions between recent studies, offering an interpretation to regional differences in the vulnerability to daily, seasonal and long-term winter temperature variability. Despite the lack of a strong year-to-year association between winter mean values in some countries, it can be concluded that warmer winters will contribute to the decrease in winter mortality everywhere in Europe. More information in Ballester J, et al. (2016) Nature Climate Change 6, 927-930, doi:10.1038/NCLIMATE3070.

Socio-climatic Exposure of an Afghan Poppy Farmer

NASA Astrophysics Data System (ADS)

Mankin, J. S.; Diffenbaugh, N. S.

2011-12-01

Many posit that climate impacts from anthropogenic greenhouse gas emissions will have consequences for the natural and agricultural systems on which humans rely for food, energy, and livelihoods, and therefore, on stability and human security. However, many of the potential mechanisms of action in climate impacts and human systems response, as well as the differential vulnerabilities of such systems, remain underexplored and unquantified. Here I present two initial steps necessary to characterize and quantify the consequences of climate change for farmer livelihood in Afghanistan, given both climate impacts and farmer vulnerabilities. The first is a conceptual model mapping the potential relationships between Afghanistan's climate, the winter agricultural season, and the country's political economy of violence and instability. The second is a utility-based decision model for assessing farmer response sensitivity to various climate impacts based on crop sensitivities. A farmer's winter planting decision can be modeled roughly as a tradeoff between cultivating the two crops that dominate the winter growing season-opium poppy (a climate tolerant cash crop) and wheat (a climatically vulnerable crop grown for household consumption). Early sensitivity analysis results suggest that wheat yield dominates farmer decision making variability; however, such initial results may dependent on the relative parameter ranges of wheat and poppy yields. Importantly though, the variance in Afghanistan's winter harvest yields of poppy and wheat is tightly linked to household livelihood and thus, is indirectly connected to the wider instability and insecurity within the country. This initial analysis motivates my focused research on the sensitivity of these crops to climate variability in order to project farmer well-being and decision sensitivity in a warmer world.

Norwegian fjord sediments reveal NAO related winter temperature and precipitation changes of the past 2800 years

NASA Astrophysics Data System (ADS)

Faust, Johan C.; Fabian, Karl; Milzer, Gesa; Giraudeau, Jacques; Knies, Jochen

2016-02-01

The North Atlantic Oscillation (NAO) is the leading mode of atmospheric circulation variability in the North Atlantic region. Associated shifts of storm tracks, precipitation and temperature patterns affect energy supply and demand, fisheries and agricultural, as well as marine and terrestrial ecological dynamics. Long-term NAO records are crucial to better understand its response to climate forcing factors, and assess predictability and shifts associated with ongoing climate change. A recent study of instrumental time series revealed NAO as main factor for a strong relation between winter temperature, precipitation and river discharge in central Norway over the past 50 years. Here we compare geochemical measurements with instrumental data and show that primary productivity recorded in central Norwegian fjord sediments is sensitive to NAO variability. This observation is used to calibrate paleoproductivity changes to a 500-year reconstruction of winter NAO (Luterbacher et al., 2001). Conditioned on a stationary relation between our climate proxy and the NAO we establish a first high resolution NAO proxy record (NAOTFJ) from marine sediments covering the past 2800 years. The NAOTFJ shows distinct co-variability with climate changes over Greenland, solar activity and Northern Hemisphere glacier dynamics as well as climatically associated paleo-demographic trends. The here presented climate record shows that fjord sediments provide crucial information for an improved understanding of the linkages between atmospheric circulation, solar and oceanic forcing factors.

Impacts of Changing Climate on Agricultural Variability: Implications for Smallholder Farmers in India

NASA Astrophysics Data System (ADS)

Mondal, P.; Jain, M.; DeFries, R. S.; Galford, G. L.; Small, C.

2013-12-01

Agriculture is the largest employment sector in India, where food productivity, and thus food security, is highly dependent on seasonal rainfall and temperature. Projected increase in temperature, along with less frequent but intense rainfall events, will have a negative impact on crop productivity in India in the coming decades. These changes, along with continued ground water depletion, could have serious implications for Indian smallholder farmers, who are among some of the most vulnerable communities to climatic and economic changes. Hence baseline information on agricultural sensitivity to climate variability is important for strategies and policies that promote adaptation to climate variability. This study examines how cropping patterns in different agro-ecological zones in India respond to variations in precipitation and temperature. We specifically examine: a) which climate variables most influence crop cover for monsoon and winter crops? and b) how does the sensitivity of crop cover to climate variability vary in different agro-ecological regions with diverse socio-economic factors? We use remote sensing data (2000-01 - 2012-13) for cropping patterns (developed using MODIS satellite data), climate parameters (derived from MODIS and TRMM satellite data) and agricultural census data. We initially assessed the importance of these climate variables in two agro-ecoregions: a predominantly groundwater irrigated, cash crop region in western India, and a region in central India primarily comprised of rain-fed or surface water irrigated subsistence crops. Seasonal crop cover anomaly varied between -25% and 25% of the 13-year mean in these two regions. Predominantly climate-dependent region in central India showed high anomalies up to 200% of the 13-year crop cover mean, especially during winter season. Winter daytime mean temperature is overwhelmingly the most important climate variable for winter crops irrespective of the varied biophysical and socio-economic conditions across the study regions. Despite access to groundwater irrigation, crop cover in the western Indian study region showed substantial fluctuations during monsoon, probably due to changing planting strategies. This region is less sensitive to precipitation compared to the central Indian study region with predominantly climate-dependent irrigation from surface water. In western Indian study region a greater number of rainy days, increased intensity of rainfall, and cooler daytime and nighttime temperatures lead to increased crop cover during monsoon season, compared to in the central Indian study region where monsoon timing and amount of total rainfall are the most important factors of crop cover. Our findings indicate that different regions respond differently to climate, since socio-economic factors, such as irrigation access, market influences, demography, and policies play critical role in agricultural production. In the wake of projected precipitation and temperature changes, better access to irrigation and heat-tolerant high-yielding crop varieties will be crucial for future food production.

Interannual and spatial variability of maple syrup yield as related to climatic factors

PubMed Central

Houle, Daniel

2014-01-01

Sugar maple syrup production is an important economic activity for eastern Canada and the northeastern United States. Since annual variations in syrup yield have been related to climate, there are concerns about the impacts of climatic change on the industry in the upcoming decades. Although the temporal variability of syrup yield has been studied for specific sites on different time scales or for large regions, a model capable of accounting for both temporal and regional differences in yield is still lacking. In the present study, we studied the factors responsible for interregional and interannual variability in maple syrup yield over the 2001–2012 period, by combining the data from 8 Quebec regions (Canada) and 10 U.S. states. The resulting model explained 44.5% of the variability in yield. It includes the effect of climatic conditions that precede the sapflow season (variables from the previous growing season and winter), the effect of climatic conditions during the current sapflow season, and terms accounting for intercountry and temporal variability. Optimal conditions for maple syrup production appear to be spatially restricted by less favourable climate conditions occurring during the growing season in the north, and in the south, by the warmer winter and earlier spring conditions. This suggests that climate change may favor maple syrup production northwards, while southern regions are more likely to be negatively affected by adverse spring conditions. PMID:24949244

A multi-model ensemble view of winter heat flux dynamics and the dipole mode in the Mediterranean Sea

NASA Astrophysics Data System (ADS)

Liguori, Giovanni; Di Lorenzo, Emanuele; Cabos, William

2017-02-01

Changes in surface heat fluxes affect several climate processes controlling the Mediterranean climate. These include the winter formation of deep waters, which is the primary driver of the Mediterranean Sea overturning circulation. Previous studies that characterize the spatial and temporal variability of surface heat flux anomalies over the basin reveal the existence of two statistically dominant patterns of variability: a monopole of uniform sign and an east-west dipole of opposite signs. In this work, we use the 12 regional climate model ensemble from the EU-FP6 ENSEMBLES project to diagnose the large-scale atmospheric processes that control the variability of heat fluxes over the Mediterranean Sea from interannual to decadal timescales (here defined as timescales > 6 year). Our findings suggest that while the monopole structure captures variability in the winter-to-winter domain-average net heat flux, the dipole pattern tracks changes in the Mediterranean climate that are connected to the East Atlantic/Western Russia (EA/WR) atmospheric teleconnection pattern. Furthermore, while the monopole exhibits significant differences in the spatial structure across the multi-model ensemble, the dipole pattern is very robust and more clearly identifiable in the anomaly maps of individual years. A heat budget analysis of the dipole pattern reveals that changes in winds associated with the EA/WR pattern exert dominant control through both a direct effect on the latent heat flux (i.e., wind speed) and an indirect effect through specific humidity (e.g., wind advection). A simple reconstruction of the heat flux variability over the deep-water formation regions of the Gulf of Lion and the Aegean Sea reveals that the combination of the monopole and dipole time series explains over 90 % of the heat flux variance in these regions. Given the important role that surface heat flux anomalies play in deep-water formation and the regional climate, improving our knowledge on the dynamics controlling the leading modes of heat flux variability may enhance our predictability of the climate of the Mediterranean area.

On the discrepancy between observed and CMIP5 multi-model simulated Barents Sea winter sea ice decline

NASA Astrophysics Data System (ADS)

Li, Dawei; Zhang, Rong; Knutson, Thomas R.

2017-04-01

This study aims to understand the relative roles of external forcing versus internal climate variability in causing the observed Barents Sea winter sea ice extent (SIE) decline since 1979. We identify major discrepancies in the spatial patterns of winter Northern Hemisphere sea ice concentration trends over the satellite period between observations and CMIP5 multi-model mean externally forced response. The CMIP5 externally forced decline in Barents Sea winter SIE is much weaker than that observed. Across CMIP5 ensemble members, March Barents Sea SIE trends have little correlation with global mean surface air temperature trends, but are strongly anti-correlated with trends in Atlantic heat transport across the Barents Sea Opening (BSO). Further comparison with control simulations from coupled climate models suggests that enhanced Atlantic heat transport across the BSO associated with regional internal variability may have played a leading role in the observed decline in winter Barents Sea SIE since 1979.

Coupled Effects of Climatic and Socio-economic Factors on Winter Cropping in India

NASA Astrophysics Data System (ADS)

Jain, M.; Mondal, P.; Galford, G. L.; DeFries, R. S.

2015-12-01

India is predicted to be one of the most vulnerable regions in terms of agricultural sensitivity to future climate changes. Approximately 69% of India's population is rural, and over 55% of the working population relies on agriculture for sustenance and livelihoods. Indian smallholder farmers who own less than 2 ha of farmland represent 78% of the total Indian farmers and produce 41% of the country's food crops. These smallholder farmers are among some of the most vulnerable communities to climatic and economic changes due to limited access to technology, infrastructure, markets, and institutional or financial support in the case of adverse climatic events. Baseline information on agricultural sensitivity to climate variability will provide useful information for regional-level, and eventually state- and national-level, strategies and policies that promote adaption to climate variability. We use a decade of remote sensing analysis of cropping patterns and climatic factors along with census data for irrigation and demographic factors to understand winter cropping trajectories across agro-ecological zones in India. Findings from multiple agro-ecological zones indicate that there are three primary trajectories in winter cropping in India - increasing, fluctuating, and decreasing. In the Central Indian Highlands, for example, the most dominant trend is that of fluctuating cropped area, ranging between ~37,300 km2 in 2010 and ~21,100 km2 in 2013, which is associated with village-level access to irrigation and local labor dynamics. Clay soil type and increasing irrigation coverage were associated with intensification. Yet, suitable soil type and access to irrigation do not reduce vulnerability to high daytime temperatures that is negatively associated with winter crop cover. With pronounced winter warming projected in the coming decades, effective adaptation by smallholder farmers would require additional strategies, such as access to fine-scale temperature forecasts ahead of the planting season and heat-tolerant winter crop varieties.

Local weather, regional climate, and annual survival of the northern spotted owl

USGS Publications Warehouse

Glenn, E.M.; Anthony, R.G.; Forsman, E.D.; Olson, G.S.

2011-01-01

We used an information-theoretical approach and Cormack-Jolly-Seber models for open populations in program MARK to examine relationships between survival rates of Northern Spotted Owls and a variety of local weather variables and long-term climate variables. In four of the six populations examined, survival was positively associated with wetter than normal conditions during the growing season or high summer temperatures. At the three study areas located at the highest elevations, survival was positively associated with winter temperature but also had a negative or quadratic relation with the number of storms and winter precipitation. A metaanalysis of all six areas combined indicated that annual survival was most strongly associated with phase shifts in the Southern Oscillation and Pacific Decadal Oscillation, which reflect large-scale temperature and precipitation patterns in this region. Climate accounted for a variable amount (1-41%) of the total process variation in annual survival but for more year-to-year variation (3-66%) than did spatial variation among owl territories (0-7%). Negative associations between survival and cold, wet winters and nesting seasons were similar to those found in other studies of the Spotted Owl. The relationships between survival and growing-season precipitation and regional climate patterns, however, had not been reported for this species previously. Climate-change models for the first half of the 21st century predict warmer, wetter winters and hotter, drier summers for the Pacific Northwest. Our results indicate that these conditions could decrease Spotted Owl survival in some areas. Copyright ?? The Cooper Ornithological Society 2011.

Is "Warm Arctic, Cold Continent" A Fingerprint Pattern of Climate Change?

NASA Astrophysics Data System (ADS)

Hoerling, M. P.; Sun, L.; Perlwitz, J.

2015-12-01

Cold winters and cold waves have recently occurred in Europe, central Asia and the Midwest to eastern United States, even as global mean temperatures set record highs and Arctic amplification of surface warming continued. Since 1979, Central Asia winter temperatures have in fact declined. Conjecture has it that more cold extremes over the mid-latitude continents should occur due to global warming and the impacts of Arctic sea ice loss. A Northern Hemisphere temperature signal termed the "Warm Arctic, Cold Continent" pattern has thus been surmised. Here we use a multi-model approach to test the hypothesis that such a pattern is indeed symptomatic of climate change. Diagnosis of a large model ensemble of historical climate simulations shows some individual realizations to yield cooling trends over Central Asia, but importantly the vast majority show warming. The observed cooling has thus likely been a low probability state of internal variability, not a fingerprint of forced climate change. We show that daily temperature variations over continents decline in winter due to global warming, and cold waves become less likely. This is partly related to diminution of Arctic cold air reservoirs due to warming-induced sea ice loss. Nonetheless, we find some evidence and present a physical basis that Arctic sea ice loss alone can induce a winter cooling over Central Asia, though with a magnitude that is appreciably smaller than the overall radiative-forced warming signal. Our results support the argument that recent cooling trends over central Asia, and cold extreme events over the winter continents, have principally resulted from atmospheric internal variability and have been neither a forced response to Arctic seas ice loss nor a symptom of global warming. The paradigm of climate change is thus better expressed as "Warm Arctic, Warm Continent" for the NH winter.

Skillful prediction of northern climate provided by the ocean

NASA Astrophysics Data System (ADS)

Årthun, Marius; Eldevik, Tor; Viste, Ellen; Drange, Helge; Furevik, Tore; Johnson, Helen L.; Keenlyside, Noel S.

2017-06-01

It is commonly understood that a potential for skillful climate prediction resides in the ocean. It nevertheless remains unresolved to what extent variable ocean heat is imprinted on the atmosphere to realize its predictive potential over land. Here we assess from observations whether anomalous heat in the Gulf Stream's northern extension provides predictability of northwestern European and Arctic climate. We show that variations in ocean temperature in the high latitude North Atlantic and Nordic Seas are reflected in the climate of northwestern Europe and in winter Arctic sea ice extent. Statistical regression models show that a significant part of northern climate variability thus can be skillfully predicted up to a decade in advance based on the state of the ocean. Particularly, we predict that Norwegian air temperature will decrease over the coming years, although staying above the long-term (1981-2010) average. Winter Arctic sea ice extent will remain low but with a general increase towards 2020.

Climate variables explain neutral and adaptive variation within salmonid metapopulations: The importance of replication in landscape genetics

USGS Publications Warehouse

Hand, Brian K.; Muhlfeld, Clint C.; Wade, Alisa A.; Kovach, Ryan; Whited, Diane C.; Narum, Shawn R.; Matala, Andrew P.; Ackerman, Michael W.; Garner, B. A.; Kimball, John S; Stanford, Jack A.; Luikart, Gordon

2016-01-01

Understanding how environmental variation influences population genetic structure is important for conservation management because it can reveal how human stressors influence population connectivity, genetic diversity and persistence. We used riverscape genetics modelling to assess whether climatic and habitat variables were related to neutral and adaptive patterns of genetic differentiation (population-specific and pairwise FST) within five metapopulations (79 populations, 4583 individuals) of steelhead trout (Oncorhynchus mykiss) in the Columbia River Basin, USA. Using 151 putatively neutral and 29 candidate adaptive SNP loci, we found that climate-related variables (winter precipitation, summer maximum temperature, winter highest 5% flow events and summer mean flow) best explained neutral and adaptive patterns of genetic differentiation within metapopulations, suggesting that climatic variation likely influences both demography (neutral variation) and local adaptation (adaptive variation). However, we did not observe consistent relationships between climate variables and FST across all metapopulations, underscoring the need for replication when extrapolating results from one scale to another (e.g. basin-wide to the metapopulation scale). Sensitivity analysis (leave-one-population-out) revealed consistent relationships between climate variables and FST within three metapopulations; however, these patterns were not consistent in two metapopulations likely due to small sample sizes (N = 10). These results provide correlative evidence that climatic variation has shaped the genetic structure of steelhead populations and highlight the need for replication and sensitivity analyses in land and riverscape genetics.

Use of ENSO forecasts to select nitrogen fertilizer application strategies for winter

USDA-ARS?s Scientific Manuscript database

El Niño Southern Oscillation (ENSO) has a strong impact on winter crops in Alabama (AL). Wheat is basically grown during winter as cash crop and sometimes also as fodder or grain crop in AL. Thus, it is very necessary to understand the impact of variability in climate factors due to the different ph...

Multi-scale linkages of winter drought variability to ENSO and the Arctic Oscillation: A case study in Shaanxi, North China

NASA Astrophysics Data System (ADS)

Liu, Zhiyong; Zhang, Xin; Fang, Ruihong

2018-02-01

Understanding the potential connections between climate indices such as the El Niño-Southern Oscillation (ENSO) and Arctic Oscillation (AO) and drought variability will be beneficial for making reasonable predictions or assumptions about future regional droughts, and provide valuable information to improve water resources planning and design for specific regions of interest. This study is to examine the multi-scale relationships between winter drought variability over Shaanxi (North China) and both ENSO and AO during the period 1960-2009. To accomplish this, we first estimated winter dryness/wetness conditions over Shaanxi based on the self-calibrating Palmer drought severity index (PDSI). Then, we identified the spatiotemporal variability of winter dryness/wetness conditions in the study area by using the empirical orthogonal function (EOF). Two primary sub-regions of winter dryness/wetness conditions across Shaanxi were identified. We further examined the periodical oscillations of dryness/wetness conditions and the multi-scale relationships between dryness/wetness conditions and both ENSO and AO in winter using wavelet analysis. The results indicate that there are inverse multi-scale relations between winter dryness/wetness conditions and ENSO (according to the wavelet coherence) for most of the study area. Moreover, positive multi-scale relations between winter dryness/wetness conditions and AO are mainly observed. The results could be beneficial for making reasonable predictions or assumptions about future regional droughts and provide valuable information to improve water resources planning and design within this study area. In addition to the current study area, this study may also offer a useful reference for other regions worldwide with similar climate conditions.

Quantifying the risks of winter damage on overwintering crops under future climates: Will low-temperature damage be more likely in warmer climates?

NASA Astrophysics Data System (ADS)

Vico, G.; Weih, M.

2014-12-01

Autumn-sown crops act as winter cover crop, reducing soil erosion and nutrient leaching, while potentially providing higher yields than spring varieties in many environments. Nevertheless, overwintering crops are exposed for longer periods to the vagaries of weather conditions. Adverse winter conditions, in particular, may negatively affect the final yield, by reducing crop survival or its vigor. The net effect of the projected shifts in climate is unclear. On the one hand, warmer temperatures may reduce the frequency of low temperatures, thereby reducing damage risk. On the other hand, warmer temperatures, by reducing plant acclimation level and the amount and duration of snow cover, may increase the likelihood of damage. Thus, warmer climates may paradoxically result in more extensive low temperature damage and reduced viability for overwintering plants. The net effect of a shift in climate is explored by means of a parsimonious probabilistic model, based on a coupled description of air temperature, snow cover, and crop tolerable temperature. Exploiting an extensive dataset of winter wheat responses to low temperature exposure, the risk of winter damage occurrence is quantified under conditions typical of northern temperate latitudes. The full spectrum of variations expected with climate change is explored, quantifying the joint effects of alterations in temperature averages and their variability as well as shifts in precipitation. The key features affecting winter wheat vulnerability to low temperature damage under future climates are singled out.

Climate envelope predictions indicate an enlarged suitable wintering distribution for Great Bustards (Otis tarda dybowskii) in China for the 21st century

PubMed Central

Mi, Chunrong; Falk, Huettmann

2016-01-01

The rapidly changing climate makes humans realize that there is a critical need to incorporate climate change adaptation into conservation planning. Whether the wintering habitats of Great Bustards (Otis tarda dybowskii), a globally endangered migratory subspecies whose population is approximately 1,500–2,200 individuals in China, would be still suitable in a changing climate environment, and where this could be found, is an important protection issue. In this study, we selected the most suitable species distribution model for bustards using climate envelopes from four machine learning models, combining two modelling approaches (TreeNet and Random Forest) with two sets of variables (correlated variables removed or not). We used common evaluation methods area under the receiver operating characteristic curves (AUC) and the True Skill Statistic (TSS) as well as independent test data to identify the most suitable model. As often found elsewhere, we found Random Forest with all environmental variables outperformed in all assessment methods. When we projected the best model to the latest IPCC-CMIP5 climate scenarios (Representative Concentration Pathways (RCPs) 2.6, 4.5 and 8.5 in three Global Circulation Models (GCMs)), and averaged the project results of the three models, we found that suitable wintering habitats in the current bustard distribution would increase during the 21st century. The Northeast Plain and the south of North China were projected to become two major wintering areas for bustards. However, the models suggest that some currently suitable habitats will experience a reduction, such as Dongting Lake and Poyang Lake in the Middle and Lower Yangtze River Basin. Although our results suggested that suitable habitats in China would widen with climate change, greater efforts should be undertaken to assess and mitigate unstudied human disturbance, such as pollution, hunting, agricultural development, infrastructure construction, habitat fragmentation, and oil and mine exploitation. All of these are negatively and intensely linked with global change. PMID:26855870

Climate envelope predictions indicate an enlarged suitable wintering distribution for Great Bustards (Otis tarda dybowskii) in China for the 21st century.

PubMed

Mi, Chunrong; Falk, Huettmann; Guo, Yumin

2016-01-01

The rapidly changing climate makes humans realize that there is a critical need to incorporate climate change adaptation into conservation planning. Whether the wintering habitats of Great Bustards (Otis tarda dybowskii), a globally endangered migratory subspecies whose population is approximately 1,500-2,200 individuals in China, would be still suitable in a changing climate environment, and where this could be found, is an important protection issue. In this study, we selected the most suitable species distribution model for bustards using climate envelopes from four machine learning models, combining two modelling approaches (TreeNet and Random Forest) with two sets of variables (correlated variables removed or not). We used common evaluation methods area under the receiver operating characteristic curves (AUC) and the True Skill Statistic (TSS) as well as independent test data to identify the most suitable model. As often found elsewhere, we found Random Forest with all environmental variables outperformed in all assessment methods. When we projected the best model to the latest IPCC-CMIP5 climate scenarios (Representative Concentration Pathways (RCPs) 2.6, 4.5 and 8.5 in three Global Circulation Models (GCMs)), and averaged the project results of the three models, we found that suitable wintering habitats in the current bustard distribution would increase during the 21st century. The Northeast Plain and the south of North China were projected to become two major wintering areas for bustards. However, the models suggest that some currently suitable habitats will experience a reduction, such as Dongting Lake and Poyang Lake in the Middle and Lower Yangtze River Basin. Although our results suggested that suitable habitats in China would widen with climate change, greater efforts should be undertaken to assess and mitigate unstudied human disturbance, such as pollution, hunting, agricultural development, infrastructure construction, habitat fragmentation, and oil and mine exploitation. All of these are negatively and intensely linked with global change.

Tracking of climatic niche boundaries under recent climate change.

PubMed

La Sorte, Frank A; Jetz, Walter

2012-07-01

1. Global climate has changed significantly during the past 30 years and especially in northern temperate regions which have experienced poleward shifts in temperature regimes. While there is evidence that some species have responded by moving their distributions to higher latitudes, the efficiency of this response in tracking species' climatic niche boundaries over time has yet to be addressed. 2. Here, we provide a continental assessment of the temporal structure of species responses to recent spatial shifts in climatic conditions. We examined geographic associations with minimum winter temperature for 59 species of winter avifauna at 476 Christmas Bird Count circles in North America from 1975 to 2009 under three sampling schemes that account for spatial and temporal sampling effects. 3. Minimum winter temperature associated with species occurrences showed an overall increase with a weakening trend after 1998. Species displayed highly variable responses that, on average and across sampling schemes, contained a strong lag effect that weakened in strength over time. In general, the conservation of minimum winter temperature was relevant when all species were considered together but only after an initial lag period (c. 35 years) was overcome. The delayed niche tracking observed at the combined species level was likely supported by the post1998 lull in the warming trend. 4. There are limited geographic and ecological explanations for the observed variability, suggesting that the efficiency of species' responses under climate change is likely to be highly idiosyncratic and difficult to predict. This outcome is likely to be even more pronounced and time lags more persistent for less vagile taxa, particularly during the periods of consistent or accelerating warming. Current modelling efforts and conservation strategies need to better appreciate the variation, strength and duration of lag effects and their association with climatic variability. Conservation strategies in particular will benefit through identifying and maintaining dispersal corridors that accommodate diverging dispersal strategies and timetables. © 2012 The Authors. Journal of Animal Ecology © 2012 British Ecological Society.

Framework for a U.S. Geological Survey Hydrologic Climate-Response Program in Maine

USGS Publications Warehouse

Hodgkins, Glenn A.; Lent, Robert M.; Dudley, Robert W.; Schalk, Charles W.

2009-01-01

This report presents a framework for a U.S. Geological Survey (USGS) hydrologic climate-response program designed to provide early warning of changes in the seasonal water cycle of Maine. Climate-related hydrologic changes on Maine's rivers and lakes in the winter and spring during the last century are well documented, and several river and lake variables have been shown to be sensitive to air-temperature changes. Monitoring of relevant hydrologic data would provide important baseline information against which future climate change can be measured. The framework of the hydrologic climate-response program presented here consists of four major parts: (1) identifying homogeneous climate-response regions; (2) identifying hydrologic components and key variables of those components that would be included in a hydrologic climate-response data network - as an example, streamflow has been identified as a primary component, with a key variable of streamflow being winter-spring streamflow timing; the data network would be created by maintaining existing USGS data-collection stations and establishing new ones to fill data gaps; (3) regularly updating historical trends of hydrologic data network variables; and (4) establishing basins for process-based studies. Components proposed for inclusion in the hydrologic climate-response data network have at least one key variable for which substantial historical data are available. The proposed components are streamflow, lake ice, river ice, snowpack, and groundwater. The proposed key variables of each component have extensive historical data at multiple sites and are expected to be responsive to climate change in the next few decades. These variables are also important for human water use and (or) ecosystem function. Maine would be divided into seven climate-response regions that follow major river-basin boundaries (basins subdivided to hydrologic units with 8-digit codes or larger) and have relatively homogeneous climates. Key hydrologic variables within each climate-response region would be analyzed regularly to maintain up-to-date analyses of year-to-year variability, decadal variability, and longer term trends. Finally, one basin in each climate-response region would be identified for process-based hydrologic and ecological studies.

Contingency in the Direction and Mechanics of Soil Organic Matter Responses to Increased Rainfall

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berhe, Asmeret A.; Suttle, K. Blake; Burton, Sarah D.

2012-09-03

Shifts in regional precipitation patterns will be a major component of global climate change. Rainfall will show greater and more variable changes in response to rising earth surface temperatures than most other climatic variables, and will be a major driver of ecosystem change. We studied the consequences of predicted changes in California’s rainy season for storage and stabilization mechanisms of soil organic matter (SOM). In a controlled and replicated experiment, we amended rainfall over large plots of natural grassland in accordance with alternative scenarios of future climate change. Results show that increases in annual rainfall have important consequences for soilmore » C storage, but that the strength and even direction of these effects depend entirely on seasonal timing. Rainfall increases during the winter rainy season led to pronounced C loss from soil while rainfall increases after the typical rainy season increased soil C stocks. Analysis of mineral-OM associations reveals a powerful mechanism underlying this difference: increased winter rainfall vastly diminished the role of Fe and Al oxides in SOM stabilization. Dithionite extractable crystalline Fe oxides explained more than 35 percent of the variability in C storage in ambient control and spring-addition treatments, compared to less than 0.01 percent in the winter-addition treatment. Likewise, poorly crystalline Fe and Al oxides explained more than 25 and 40 percent of the variability in C storage, respectively, in the control and spring-addition treatments compared to less than 5 percent in the -winter-addition treatment. Increases in annual precipitation identical in amount but at three-month offsets produced opposite effects on soil C storage. These results highlight the complexity inherent in biospheric feedbacks to the climate system, and the way that careful experimentation can penetrate that complexity to improve predictions of ecosystem and climatic change.« less

Winter Season Mortality: Will Climate Warming Bring Benefits?

PubMed

Kinney, Patrick L; Schwartz, Joel; Pascal, Mathilde; Petkova, Elisaveta; Tertre, Alain Le; Medina, Sylvia; Vautard, Robert

2015-06-01

Extreme heat events are associated with spikes in mortality, yet death rates are on average highest during the coldest months of the year. Under the assumption that most winter excess mortality is due to cold temperature, many previous studies have concluded that winter mortality will substantially decline in a warming climate. We analyzed whether and to what extent cold temperatures are associated with excess winter mortality across multiple cities and over multiple years within individual cities, using daily temperature and mortality data from 36 US cities (1985-2006) and 3 French cities (1971-2007). Comparing across cities, we found that excess winter mortality did not depend on seasonal temperature range, and was no lower in warmer vs. colder cities, suggesting that temperature is not a key driver of winter excess mortality. Using regression models within monthly strata, we found that variability in daily mortality within cities was not strongly influenced by winter temperature. Finally we found that inadequate control for seasonality in analyses of the effects of cold temperatures led to spuriously large assumed cold effects, and erroneous attribution of winter mortality to cold temperatures. Our findings suggest that reductions in cold-related mortality under warming climate may be much smaller than some have assumed. This should be of interest to researchers and policy makers concerned with projecting future health effects of climate change and developing relevant adaptation strategies.

Winter season mortality: will climate warming bring benefits?

NASA Astrophysics Data System (ADS)

Kinney, Patrick L.; Schwartz, Joel; Pascal, Mathilde; Petkova, Elisaveta; Le Tertre, Alain; Medina, Sylvia; Vautard, Robert

2015-06-01

Extreme heat events are associated with spikes in mortality, yet death rates are on average highest during the coldest months of the year. Under the assumption that most winter excess mortality is due to cold temperature, many previous studies have concluded that winter mortality will substantially decline in a warming climate. We analyzed whether and to what extent cold temperatures are associated with excess winter mortality across multiple cities and over multiple years within individual cities, using daily temperature and mortality data from 36 US cities (1985-2006) and 3 French cities (1971-2007). Comparing across cities, we found that excess winter mortality did not depend on seasonal temperature range, and was no lower in warmer vs. colder cities, suggesting that temperature is not a key driver of winter excess mortality. Using regression models within monthly strata, we found that variability in daily mortality within cities was not strongly influenced by winter temperature. Finally we found that inadequate control for seasonality in analyses of the effects of cold temperatures led to spuriously large assumed cold effects, and erroneous attribution of winter mortality to cold temperatures. Our findings suggest that reductions in cold-related mortality under warming climate may be much smaller than some have assumed. This should be of interest to researchers and policy makers concerned with projecting future health effects of climate change and developing relevant adaptation strategies.

What Is a Mild Winter? Regional Differences in Within-Species Responses to Climate Change.

PubMed

Vetter, Sebastian G; Ruf, Thomas; Bieber, Claudia; Arnold, Walter

2015-01-01

Climate change is known to affect ecosystems globally, but our knowledge of its impact on large and widespread mammals, and possibly population-specific responses is still sparse. We investigated large-scale and long-term effects of climate change on local population dynamics using the wild boar (Sus scrofa L.) as a model species. Our results show that population increases across Europe are strongly associated with increasingly mild winters, yet with region-specific threshold temperatures for the onset of exponential growth. Additionally, we found that abundant availability of critical food resources, e.g. beech nuts, can outweigh the negative effects of cold winters on population growth of wild boar. Availability of beech nuts is highly variable and highest in years of beech mast which increased in frequency since 1980, according to our data. We conclude that climate change drives population growth of wild boar directly by relaxing the negative effect of cold winters on survival and reproduction, and indirectly by increasing food availability. However, region-specific responses need to be considered in order to fully understand a species' demographic response to climate change.

Preventing cold-related morbidity and mortality in a changing climate

PubMed Central

Conlon, Kathryn C; Rajkovich, Nicholas B; White-Newsome, Jalonne L; Larsen, Larissa; Neill, Marie S O

2011-01-01

Winter weather patterns are anticipated to become more variable with increasing average global temperatures. Research shows that excess morbidity and mortality occurs during cold weather periods. We critically reviewed evidence relating temperature variability, health outcomes, and adaptation strategies to cold weather. Health outcomes included cardiovascular-, respiratory-, cerebrovascular-, and all-cause morbidity and mortality. Individual and contextual risk factors were assessed to highlight associations between individual- and neighborhood- level characteristics that contribute to a person’s vulnerability to variability in cold weather events. Epidemiologic studies indicate that the populations most vulnerable to variations in cold winter weather are the elderly, rural and, generally, populations living in moderate winter climates. Fortunately, cold-related morbidity and mortality are preventable and strategies exist for protecting populations from these adverse health outcomes. We present a range of adaptation strategies that can be implemented at the individual, building, and neighborhood level to protect vulnerable populations from cold-related morbidity and mortality. The existing research justifies the need for increased outreach to individuals and communities for education on protective adaptations in cold weather. We propose that future climate change adaptation research couple building energy and thermal comfort models with epidemiological data to evaluate and quantify the impacts of adaptation strategies. PMID:21592693

A modern plant-climate research dataset for modelling eastern North American plant taxa.

NASA Astrophysics Data System (ADS)

Gonzales, L. M.; Grimm, E. C.; Williams, J. W.; Nordheim, E. V.

2008-12-01

Continental-scale modern pollen-climate data repositories are a primary data source for paleoclimate reconstructions. However, these repositories can contain artifacts, such as records from different depositional environment and replicate records, that can influence the observed pollen-climate relationships as well as the paleoclimate reconstructions derived from these relationships. In this paper, we address the issues related to these artifacts as we define the methods used to create a research dataset from the North American Modern Pollen Database (Whitmore et al., 2005). Additionally, we define the methods used to select the environmental variables that are best for modeling regional pollen-climate relationships from the research dataset. Because the depositional environment determines the relative strengths of the local and regional pollen signals, combining data from different depositional environments results in pollen abundances that can be influenced by the local pollen signal. Replicate records in pollen-climate datasets can skew pollen-climate relationships by causing an over- or under- representation of pollen abundances in climate space. When these two artifacts are combined, the errors introduced into pollen-climate relationship modeling are compounded. The research dataset we present consists of 2,613 records in eastern North America, of which 70.9% are lacustrine sites. We demonstrate that this new research database improves upon the modeling of regional pollen-climate relationships for eastern North American taxa. The research dataset encompasses the majority of the temperature and mean summer precipitation ranges of the NAMPD's climatic range and 40% of its mean winter precipitation range. NAMPD sites with higher winter precipitation are located along the northwestern coast of North America where a rainshadow effect produces abundant winter precipitation. We present our analysis of the research dataset for use in paleoclimate reconstructions, and recommend that mean winter and summer temperature and precipitation variables be used for pollen-climate relationship modeling.

Change in abundance of pacific brant wintering in alaska: evidence of a climate warming effect?

USGS Publications Warehouse

Ward, David H.; Dau, Christian P.; Tibbitts, T. Lee; Sedinger, James S.; Anderson, Betty A.; Hines, James E.

2009-01-01

Winter distribution of Pacific Flyway brant (Branta bernicla nigricans) has shifted northward from lowtemperate areas to sub-Arctic areas over the last 42 years. We assessed the winter abundance and distribution of brant in Alaska to evaluate whether climate warming may be contributing to positive trends in the most northern of the wintering populations. Mean surface air temperatures during winter at the end of the Alaska Peninsula increased about 1??C between 1963 and 2004, resulting in a 23% reduction in freezing degree days and a 34% decline in the number of days when ice cover prevents birds from accessing food resources. Trends in the wintering population fluctuated with states of the Pacific Decadal Oscillation, increasing during positive (warm) phases and decreasing during negative (cold) phases, and this correlation provides support for the hypothesis that growth in the wintering population of brant in Alaska is linked to climate warming. The size of the wintering population was negatively correlated with the number of days of strong northwesterly winds in November, which suggests that the occurrence of tailwinds favorable for migration before the onset of winter was a key factor in whether brant migrated from Alaska or remained there during winter. Winter distribution of brant on the Alaska Peninsula was highly variable and influenced by ice cover, particularly at the heavily used Izembek Lagoon. Observations of previously marked brant indicated that the Alaska wintering population was composed primarily of birds originating from Arctic breeding colonies that appear to be growing. Numbers of brant in Alaska during winter will likely increase as temperatures rise and ice cover decreases at high latitudes in response to climate warming. ?? The Arctic Institute of North America.

Assessing performance and seasonal bias of pollen-based climate reconstructions in a perfect model world

NASA Astrophysics Data System (ADS)

Trachsel, M.; Rehfeld, K.; Telford, R.; Laepple, T.

2017-12-01

Reconstructions of summer, winter or annual mean temperatures based on the species composition of bio-indicators such as pollen are routinely used in climate model-proxy data comparison studies. Most reconstruction algorithms exploit the joint distribution of modern spatial climate and species distribution for the development of the reconstructions. They rely on the space-for-time substitution and the specific assumption that environmental variables other than those reconstructed are not important or that their relationship with the reconstructed variable(s) should be the same in the past as in the modern spatial calibration dataset. Here we test the implications of this "correlative uniformitarianism" assumption on climate reconstructions in an ideal model world, in which climate and vegetation are known at all times. The alternate reality is a climate simulation of the last 6000 years with dynamic vegetation. Transient changes of plant functional types are considered as surrogate pollen counts and allow us to establish, apply and evaluate transfer functions in the modeled world. We find that the transfer function cross validation r2 is of limited use to identify reconstructible climate variables, as it only relies on the modern spatial climate-vegetation relationship. However, ordination approaches that assess the amount of fossil vegetation variance explained by the reconstructions are promising. We show that correlations between climate variables in the modern climate-vegetation relationship are systematically extended into the reconstructions. Summer temperatures, the most prominent driving variable for modeled vegetation change in the Northern Hemisphere, are accurately reconstructed. However, the amplitude of the model winter and mean annual temperature cooling between the mid-Holocene and present day is overestimated and similar to the summer trend in magnitude. This effect occurs because temporal changes of a dominant climate variable are imprinted on a less important variable, leading to reconstructions biased towards the dominant variable's trends. Our results, although based on a model vegetation that is inevitably simpler than reality, indicate that reconstructions of multiple climate variables based on modern spatial bio-indicator datasets should be treated with caution.

Application of regional climate models to the Indian winter monsoon over the western Himalayas.

PubMed

Dimri, A P; Yasunari, T; Wiltshire, A; Kumar, P; Mathison, C; Ridley, J; Jacob, D

2013-12-01

The Himalayan region is characterized by pronounced topographic heterogeneity and land use variability from west to east, with a large variation in regional climate patterns. Over the western part of the region, almost one-third of the annual precipitation is received in winter during cyclonic storms embedded in westerlies, known locally as the western disturbance. In the present paper, the regional winter climate over the western Himalayas is analyzed from simulations produced by two regional climate models (RCMs) forced with large-scale fields from ERA-Interim. The analysis was conducted by the composition of contrasting (wet and dry) winter precipitation years. The findings showed that RCMs could simulate the regional climate of the western Himalayas and represent the atmospheric circulation during extreme precipitation years in accordance with observations. The results suggest the important role of topography in moisture fluxes, transport and vertical flows. Dynamical downscaling with RCMs represented regional climates at the mountain or even event scale. However, uncertainties of precipitation scale and liquid-solid precipitation ratios within RCMs are still large for the purposes of hydrological and glaciological studies. Copyright © 2013 Elsevier B.V. All rights reserved.

Impacts of the EA and SCA patterns on the 20th century NAO-winter precipitation relationship in Europe

NASA Astrophysics Data System (ADS)

Comas-Bru, Laia; McDermott, Frank

2013-04-01

Much of the 20th century multi-decadal variability in the NAO-winter precipitation relationship over the N. Atlantic / European sector can be ascribed to the combined effects of the North Atlantic Oscillation (NAO) and either the East Atlantic pattern (EA) or the Scandinavian pattern (SCA). The NAO, EA and SCA indices employed here are defined as the three leading vectors of the cross-correlation matrix calculated from monthly sea-level pressure anomalies for 138 complete winters from the 20CRv2 dataset (Compo et al., 2011). Winter precipitation data over Europe for the entire 20th century is derived from the high resolution CRU-TS3.1 climate dataset (Mitchell and Jones, 2005). Here we document for the first time, that different NAO/EA and NAO/SCA combinations systematically influence winter precipitation conditions in Europe as a consequence of NAO dipole migrations. We find that the zero-correlated line of the NAO-winter precipitation relationship migrates southwards when the EA is in the opposite phase to the NAO. This can be related to a south-westwards migration of the NAO dipole under these conditions, as shown by teleconnectivity maps. Similarly, a clockwise movement of the NAO-winter climate correlated areas occurs when the phase of the SCA is opposite to that of the NAO, reflecting a clockwise movement of the NAO dipole under these conditions. An important implication of these migrations is that they influence the spatial and temporal stationarity of climate-NAO relationships. As a result, the link between winter precipitation patterns and the NAO is not straightforward in some regions such as the southern UK, Ireland and France. For instance, much of the inter-annual variability in the N-S winter precipitation gradient in the UK, originally attributed to inter-annual and inter-decadal variability of the NAO, reflects the migration of the NAO dipole, linked to linear combinations of the NAO and the EA. Our results indicate that when the N-S winter precipitation gradient is accentuated by the occurrence of a positive EA during positive NAO winters, drier conditions than normal are found in the southern UK. This is consistent, for example, with the severe winter drought of 1976, when computed NAO and EA indices were both positive (0.97 and 1.87, respectively), illustrating the modulating effect of NAO/EA combinations on winter precipitation patterns in the southern UK. References: Compo GP et al. 2011. The Twentieth Century Reanalysis Project. Quarterly Journal of the Royal Meteorological Society, 137 (654), 1-28. Mitchell TD, Jones PD. 2005. An improved method for constructing a database of monthly climate observations and associated high-resolution grids. International Journal of Climatology, 25, 693-712.

Changes in rainfed and irrigated crop yield response to climate in the western US

NASA Astrophysics Data System (ADS)

Li, X.; Troy, T. J.

2018-06-01

As the global population increases and the climate changes, ensuring a secure food supply is increasingly important. One strategy is irrigation, which allows for crops to be grown outside their optimal climate growing regions and which buffers against climate variability. Although irrigation is a positive climate adaptation mechanism for agriculture, it has a potentially negative effect on water resources as it can lead to groundwater depletion and diminished surface water supplies. This study quantifies how crop yields are affected by climate variability and extremes and the impact of irrigation on crop yield increases under various growing-season climate conditions. To do this, we use historical climate data and county-level rainfed and irrigated crop yields for maize, soybean, winter and spring wheat over the US to analyze the relationship between climate, crop yields, and irrigation. We find that there are optimal climates, specific to each crop, where irrigation provides a benefit and other conditions where irrigation proves to have marginal, if any, benefits. Furthermore, the relationship between crop yields and climate has changed over the last decades, with a changing sensitivity in the relationship of soybean and winter wheat yields to certain climate variables, like crop reference evapotranspiration. These two conclusions have important implications for agricultural and water resource system planning, as it implies there are more optimal climate conditions where irrigation is particularly productive and regions where irrigation should be reconsidered as there is not a significant agricultural benefit and the water could be used more productively.

Arctic vs. Tropical Influence and Over the Period of Arctic Amplification including Winter 2015/16

NASA Astrophysics Data System (ADS)

Cohen, J. L.; Francis, J. A.; Pfeiffer, K.

2016-12-01

The tropics in general and El Niño/Southern Oscillation (ENSO) in particular are almost exclusively relied upon for seasonal forecasting. Much less considered and certainly more controversial is the idea that Arctic variability is influencing mid-latitude weather. However, since the late 1980s and early 1990s the Arctic has undergone the most rapid warming observed globally, referred to as Arctic amplification (AA), which has coincided with an observed increase in extreme weather. Analysis of observed trends in hemispheric circulation over the period of AA more closely resembles variability associated with Arctic boundary forcings than with tropical forcing. Furthermore, analysis of intra-seasonal temperature variability shows that the cooling in mid-latitude winter temperatures has been accompanied by an increase in temperature variability and not a decrease, popularly referred to as "weather whiplash." When a record El Niño occurred this past winter, it should have been an opportunity to showcase decades of research and resources dedicated to the study of the ENSO phenomenon and its global impacts. However the dynamical forecasts performed poorly this past winter. Instead we will show that many of the significant circulation anomalies of this past winter are related to high latitude processes. We believe that the failed forecasts of this past winter will serve as a watershed moment and an inflection point in climate science. Climate science requires a paradigm shift in order to improve long-range forecasts. Less reliance on the tropics and exploration of new regions of predictability, including the Arctic, are required.

Skillful prediction of northern climate provided by the ocean

PubMed Central

Årthun, Marius; Eldevik, Tor; Viste, Ellen; Drange, Helge; Furevik, Tore; Johnson, Helen L.; Keenlyside, Noel S.

2017-01-01

It is commonly understood that a potential for skillful climate prediction resides in the ocean. It nevertheless remains unresolved to what extent variable ocean heat is imprinted on the atmosphere to realize its predictive potential over land. Here we assess from observations whether anomalous heat in the Gulf Stream's northern extension provides predictability of northwestern European and Arctic climate. We show that variations in ocean temperature in the high latitude North Atlantic and Nordic Seas are reflected in the climate of northwestern Europe and in winter Arctic sea ice extent. Statistical regression models show that a significant part of northern climate variability thus can be skillfully predicted up to a decade in advance based on the state of the ocean. Particularly, we predict that Norwegian air temperature will decrease over the coming years, although staying above the long-term (1981–2010) average. Winter Arctic sea ice extent will remain low but with a general increase towards 2020. PMID:28631732

Dynamical adjustment of Scandinavian glacier mass-balance time series

NASA Astrophysics Data System (ADS)

Bonan, D.; Christian, J. E.; Christianson, K. A.

2017-12-01

Glacier mass wastage is often cited as one of the most visible manifestations of anthropogenic climate change. Annual glacier mass-balance is related to local climate and atmospheric circulation, as it is defined as the yearly sum of accumulation and ablation—processes that are strongly influenced by year-to-year fluctuations in precipitation and temperature. Glacier response to a climatic trend can, however, be masked by internal variability in atmospheric circulation, and by non-climatic factors (such as topographic control, wind deposition, and incident solar radiation). Thus, unambiguous attribution of a negative glacier mass-balance trend to anthropogenic forcing remains challenging. Maritime glacier mass-balance records may be especially difficult to interpret due to the high winter balances from decadal-scale climate oscillations and the relatively short time series. Here we examine the influence of climate and atmospheric circulation variability on 14 Norwegian glaciers that span 20° of latitude, from southern Norway to Svalbard. We use dynamical adjustment—a statistical method based on partial least squares regression—to identify the components of variability within the mass-balance records that are associated with the time-varying sea level pressure (SLP) and sea surface temperature (SST) fields. We find that 30-50% of the variance in the winter mass-balance records of the glaciers in southern Norway is explained by using sea level pressure as a predictor. The leading SLP predictor pattern mimics the spatial signature of the North Atlantic Oscillation (NAO), indicating that winter balance is strongly influenced by the NAO. Moreover, the adjusted mass-balance records indicate a geographic trend: the southern Norwegian glaciers have significant negative trends in the summer balance that remain negative after adjustment, while the more northern glaciers have negative winter balance trends that only become significant after adjustment. We look into anthropogenic warming to explain the trends after dynamical adjustment.

Trends in Cold Extremes and Winter Weather for the SPTC Region

DOT National Transportation Integrated Search

2017-05-31

Extreme weather poses multifaceted hazards to transportation. There is now increased awareness of the threats of climate variability and change on transportation safety and state of good repair. In particular, a non-stationary climate will potentiall...

Comparative Evaluation of Performances of Two Versions of NCEP Climate Forecast System in Predicting Winter Precipitation over India

NASA Astrophysics Data System (ADS)

Nageswararao, M. M.; Mohanty, U. C.; Nair, Archana; Ramakrishna, S. S. V. S.

2016-06-01

The precipitation during winter (December through February) over India is highly variable in terms of time and space. Maximum precipitation occurs over the Himalaya region, which is important for water resources and agriculture sectors over the region and also for the economy of the country. Therefore, in the present global warming era, the realistic prediction of winter precipitation over India is important for planning and implementing agriculture and water management strategies. The National Centers for Environmental Prediction (NCEP) issued the operational prediction of climatic variables in monthly to seasonal scale since 2004 using their first version of fully coupled global climate model known as Climate Forecast System (CFSv1). In 2011, a new version of CFS (CFSv2) was introduced with the incorporation of significant changes in older version of CFS (CFSv1). The new version of CFS is required to compare in detail with the older version in the context of simulating the winter precipitation over India. Therefore, the current study presents a detailed analysis on the performance of CFSv2 as compared to CFSv1 for the winter precipitation over India. The hindcast runs of both CFS versions from 1982 to 2008 with November initial conditions are used and the model's precipitation is evaluated with that of India Meteorological Department (IMD). The models simulated wind and geopotential height against the National Center for Atmospheric Research (NCEP-NCAR) reanalysis-2 (NNRP2) and remote response patterns of SST against Extended Reconstructed Sea Surface Temperatures version 3b (ERSSTv3b) are examined for the same period. The analyses of winter precipitation revealed that both the models are able to replicate the patterns of observed climatology; interannual variability and coefficient of variation. However, the magnitude is lesser than IMD observation that can be attributed to the model's inability to simulate the observed remote response of sea surface temperatures to all India winter precipitation. Of the two, CFSv1 is appreciable in capturing year-to-year variations in observed winter precipitation while CFSv2 failed in simulating the same. CFSv1 has accounted for less mean bias and RMSE errors along with good correlations and index of agreements than CFSv2 for predicting winter precipitation over India. In addition, the CFSv1 is also having a high probability of detection in predicting different categories (normal, excess and deficit) of observed winter precipitation over India.

Sensitivity of crop cover to climate variability: insights from two Indian agro-ecoregions.

PubMed

Mondal, Pinki; Jain, Meha; DeFries, Ruth S; Galford, Gillian L; Small, Christopher

2015-01-15

Crop productivity in India varies greatly with inter-annual climate variability and is highly dependent on monsoon rainfall and temperature. The sensitivity of yields to future climate variability varies with crop type, access to irrigation and other biophysical and socio-economic factors. To better understand sensitivities to future climate, this study focuses on agro-ecological subregions in Central and Western India that span a range of crops, irrigation, biophysical conditions and socioeconomic characteristics. Climate variability is derived from remotely-sensed data products, Tropical Rainfall Measuring Mission (TRMM - precipitation) and Moderate Resolution Imaging Spectroradiometer (MODIS - temperature). We examined green-leaf phenologies as proxy for crop productivity using the MODIS Enhanced Vegetation Index (EVI) from 2000 to 2012. Using both monsoon and winter growing seasons, we assessed phenological sensitivity to inter-annual variability in precipitation and temperature patterns. Inter-annual EVI phenology anomalies ranged from -25% to 25%, with some highly anomalous values up to 200%. Monsoon crop phenology in the Central India site is highly sensitive to climate, especially the timing of the start and end of the monsoon and intensity of precipitation. In the Western India site, monsoon crop phenology is less sensitive to precipitation variability, yet shows considerable fluctuations in monsoon crop productivity across the years. Temperature is critically important for winter productivity across a range of crop and management types, such that irrigation might not provide a sufficient buffer against projected temperature increases. Better access to weather information and usage of climate-resilient crop types would play pivotal role in maintaining future productivity. Effective strategies to adapt to projected climate changes in the coming decades would also need to be tailored to regional biophysical and socio-economic conditions. Copyright © 2014 Elsevier Ltd. All rights reserved.

NATURAL AND ATHROPOGENIC FACTORS AFFECTING GLOBAL AND REGIONAL CLIMATE

EPA Science Inventory

New England weather is highly variable for a number of
reasons. Our regional climate is also quite variable. The
winters of the past decade are milder than they were in the
1960s and 1970s but as the ice-out and snowfall data show
(Figs 2.5 and 2.6), the patterns of c...

Montane ecosystem productivity responds more to global circulation patterns than climatic trends.

PubMed

Desai, A R; Wohlfahrt, G; Zeeman, M J; Katata, G; Eugster, W; Montagnani, L; Gianelle, D; Mauder, M; Schmid, H-P

2016-02-01

Regional ecosystem productivity is highly sensitive to inter-annual climate variability, both within and outside the primary carbon uptake period. However, Earth system models lack sufficient spatial scales and ecosystem processes to resolve how these processes may change in a warming climate. Here, we show, how for the European Alps, mid-latitude Atlantic ocean winter circulation anomalies drive high-altitude summer forest and grassland productivity, through feedbacks among orographic wind circulation patterns, snowfall, winter and spring temperatures, and vegetation activity. Therefore, to understand future global climate change influence to regional ecosystem productivity, Earth systems models need to focus on improvements towards topographic downscaling of changes in regional atmospheric circulation patterns and to lagged responses in vegetation dynamics to non-growing season climate anomalies.

Montane ecosystem productivity responds more to global circulation patterns than climatic trends

NASA Astrophysics Data System (ADS)

Desai, A. R.; Wohlfahrt, G.; Zeeman, M. J.; Katata, G.; Eugster, W.; Montagnani, L.; Gianelle, D.; Mauder, M.; Schmid, H.-P.

2016-02-01

Regional ecosystem productivity is highly sensitive to inter-annual climate variability, both within and outside the primary carbon uptake period. However, Earth system models lack sufficient spatial scales and ecosystem processes to resolve how these processes may change in a warming climate. Here, we show, how for the European Alps, mid-latitude Atlantic ocean winter circulation anomalies drive high-altitude summer forest and grassland productivity, through feedbacks among orographic wind circulation patterns, snowfall, winter and spring temperatures, and vegetation activity. Therefore, to understand future global climate change influence to regional ecosystem productivity, Earth systems models need to focus on improvements towards topographic downscaling of changes in regional atmospheric circulation patterns and to lagged responses in vegetation dynamics to non-growing season climate anomalies.

Distant Influence of Kuroshio Eddies on North Pacific Weather Patterns?

PubMed

Ma, Xiaohui; Chang, Ping; Saravanan, R; Montuoro, Raffaele; Hsieh, Jen-Shan; Wu, Dexing; Lin, Xiaopei; Wu, Lixin; Jing, Zhao

2015-12-04

High-resolution satellite measurements of surface winds and sea-surface temperature (SST) reveal strong coupling between meso-scale ocean eddies and near-surface atmospheric flow over eddy-rich oceanic regions, such as the Kuroshio and Gulf Stream, highlighting the importance of meso-scale oceanic features in forcing the atmospheric planetary boundary layer (PBL). Here, we present high-resolution regional climate modeling results, supported by observational analyses, demonstrating that meso-scale SST variability, largely confined in the Kuroshio-Oyashio confluence region (KOCR), can further exert a significant distant influence on winter rainfall variability along the U.S. Northern Pacific coast. The presence of meso-scale SST anomalies enhances the diabatic conversion of latent heat energy to transient eddy energy, intensifying winter cyclogenesis via moist baroclinic instability, which in turn leads to an equivalent barotropic downstream anticyclone anomaly with reduced rainfall. The finding points to the potential of improving forecasts of extratropical winter cyclones and storm systems and projections of their response to future climate change, which are known to have major social and economic impacts, by improving the representation of ocean eddy-atmosphere interaction in forecast and climate models.

Performance evaluation of NCEP climate forecast system for the prediction of winter temperatures over India

NASA Astrophysics Data System (ADS)

Nageswararao, M. M.; Mohanty, U. C.; Kiran Prasad, S.; Osuri, Krishna K.; Ramakrishna, S. S. V. S.

2016-11-01

The surface air temperature during the winter season (December-February) in India adversely affects agriculture as well as day-to-day life. Therefore, the accurate prediction of winter temperature in extended range is of utmost importance. The National Center for Environmental Prediction (NCEP) has been providing climatic variables from the fully coupled global climate model, known as Climate Forecast System version 1 (CFSv1) on monthly to seasonal scale since 2004, and it has been upgraded to CFSv2 subsequently in 2011. In the present study, the performance of CFSv1 and CFSv2 in simulating the winter 2 m maximum, minimum, and mean temperatures ( T max, T min, and T mean, respectively) over India is evaluated with respect to India Meteorological Department (IMD) 1° × 1° observations. The hindcast data obtained from both versions of CFS from 1982 to 2009 (27 years) with November initial conditions (lead-1) are used. The analyses of winter ( T max, T min, and T mean) temperatures revealed that CFSv1 and CFSv2 are able to replicate the patterns of observed climatology, interannual variability, and coefficient of variation with a slight negative bias. Of the two, CFSv2 is appreciable in capturing increasing trends of winter temperatures like observed. The T max, T min, and T mean correlations from CFSv2 is significantly high (0.35, 0.53, and 0.51, respectively), while CFSv1 correlations are less (0.29, 0.15, and 0.12) and insignificant. This performance of CFSv2 may be due to the better estimation of surface heat budget terms and realistic CO2 concentration, which were absent in CFSv1. CFSv2 proved to have a high probability of detection in predicting different categories (below, near, and above normal) for winter T min, which are required for crop yield and public utility services, over north India.

Should anthropogenic warming lead to more frequent cold air outbreaks over the northeastern U.S.?

NASA Astrophysics Data System (ADS)

Nicholas, R.

2014-12-01

For the northeastern United States, Winter 2013-14 was the coldest winter since the late 1970s and perhaps the coldest on record relative to prevailing climatic conditions. Frequent snowstorms and cold air outbreaks led to considerable press coverage and heated scholarly debate over the possible role of anthropogenic climate change in modulating wintertime variability in the northern hemisphere polar jet. While mechanisms have been proposed, to date, the observational record offers no definitive evidence for such a relationship, nor does it conclusively exclude one. To further explore this question, we employ a large, initial conditions ensemble of the Community Earth System Model forced with historical and RCP8.5 emissions. The ensemble effectively samples internal variability in the climate system and is used to assess the potential for forced changes in polar jet variability and the frequency of cold air outbreaks over the northeastern U.S. with projected increases in global mean temperature during the 21st century.

Arctic Sea Ice, Eurasia Snow, and Extreme Winter Haze in China

NASA Astrophysics Data System (ADS)

Zou, Y.; Wang, Y.; Xie, Z.; Zhang, Y.; Koo, J. H.

2017-12-01

Eastern China is experiencing more severe haze pollution in winter during recent years. Though the environmental deterioration in this region is usually attributed to the high intensity of anthropogenic emissions and large contributions from secondary aerosol formation, the impact of climate variability is also indispensable given its significant influence on regional weather systems and pollution ventilation. Here we analyzed the air quality related winter meteorological conditions over Eastern China in the last four decades and showed a worsening trend in poor regional air pollutant ventilation. Such variations increased the probability of extreme air pollution events, which is in good agreement with aerosol observations of recent years. We further identified the key circulation pattern that is conducive to the weakening ventilation and investigated the relationship between synoptic circulation changes and multiple climate forcing variables. Both statistical analysis and numerical sensitivity experiments suggested that the poor ventilation condition is linked to boreal cryosphere changes including Arctic sea ice in preceding autumn and Eurasia snowfall in earlier winter. We conducted comprehensive dynamic diagnosis and proposed a physical mechanism to explain the observed and simulated circulation changes. At last, we examined future projections of winter extreme stagnation events based on the CMIP5 projection data.

Climate impact of idealized winter polar mesospheric and stratospheric ozone losses as caused by energetic particle precipitation

NASA Astrophysics Data System (ADS)

Meraner, Katharina; Schmidt, Hauke

2018-01-01

Energetic particles enter the polar atmosphere and enhance the production of nitrogen oxides and hydrogen oxides in the winter stratosphere and mesosphere. Both components are powerful ozone destroyers. Recently, it has been inferred from observations that the direct effect of energetic particle precipitation (EPP) causes significant long-term mesospheric ozone variability. Satellites observe a decrease in mesospheric ozone up to 34 % between EPP maximum and EPP minimum. Stratospheric ozone decreases due to the indirect effect of EPP by about 10-15 % observed by satellite instruments. Here, we analyze the climate impact of winter boreal idealized polar mesospheric and polar stratospheric ozone losses as caused by EPP in the coupled Max Planck Institute Earth System Model (MPI-ESM). Using radiative transfer modeling, we find that the radiative forcing of mesospheric ozone loss during polar night is small. Hence, climate effects of mesospheric ozone loss due to energetic particles seem unlikely. Stratospheric ozone loss due to energetic particles warms the winter polar stratosphere and subsequently weakens the polar vortex. However, those changes are small, and few statistically significant changes in surface climate are found.

Comparative glacio-climatological analysis of mass balance variability along the geographical margin of Europe

NASA Astrophysics Data System (ADS)

Lehoczky, Annamária; Kern, Zoltán; Pongrácz, Rita

2014-05-01

Glacio-climatological studies recognise glacier mass balance changes as high-confident climate indicators. The climatic sensitivity of a glacier does not simply depend on regional climate variability but also influenced via large- and mesoscale atmospheric circulation patterns. This study focuses on recent changes in the mass balance using records from three border regions of Europe, and investigates the relationships between the seasonal mass balance components, regional climatic conditions, and distant atmospheric forcing. Since glaciers in different macro-climatological conditions (i.e., mid-latitudes or high-latitudes, dry-continental or maritime regions) may present strongly diverse mass balance characteristics, the three analysed regions were selected from different glacierised macroregions (using the database of the World Glacier Monitoring Service). These regions belong to the Caucasus Mountains (Central Europe macroregion), the Polar Ural (Northern Asia macroregion), and Svalbard (Arctic Islands macroregion). The analysis focuses on winter, summer, and annual mass balance series of eight glaciers. The climatic variables (atmospheric pressure, air temperature, precipitation) and indices of teleconnection patterns (e.g., North Atlantic Oscillation, Pacific Decadal Oscillation) are used from the gridded databases of the University of East Anglia, Climatic Research Unit and the National Oceanic and Atmospheric Administration, National Center for Environmental Prediction. However, the period and length of available mass balance data in the selected regions vary greatly (the first full record is in 1958, Polar Ural; the last is in 2010, Caucasus Mountains), a comparative analysis can be carried out for the period of 1968-1981. Since glaciers from different regions respond to large- and mesoscale climatic forcings differently, and because the mass balance of glaciers within a region often co-vary, our specific objectives are (i) to examine the variability and the integrative climatic signal in the averaged mass balance records of the selected regions; (ii) to analyse the possible coupling between the mass balance and climatic variables, including the dominant patterns of Northern Hemisphere climate variability; and (iii) to compare the main characteristics of the three regions. Furthermore, (iv) a short discussion is given considering the significant decreasing trend of the cumulative annual mass balances in every region under the detected climatic changes in the second half of the 20th century. Preliminary results suggest that the strongest teleconnection links could be between winter mass balance and winter NAO for the Polar Ural (r=0.46, p<0.05), and between annual mass balance and PDO for Svalbard (r=-0.43, p<0.05). Neither seasonal, nor annual mass balance records showed significant correlation with any of the examined circulation indices for the Caucasus.

Sensitivity of intermittent streams to climate variations in the United States

NASA Astrophysics Data System (ADS)

Eng, K.

2015-12-01

There is growing interest in the effects of climate change on streamflows because of the potential negative effects on aquatic biota and water supplies. Previous studies of climate controls on flows have primarily focused on perennial streams, and few studies have examined the effect of climate variability on intermittent streams. Our objectives in this study were to (1) identify regions showing similar patterns of intermittency, and (2) evaluate the sensitivity of intermittent streams to historical variability in climate in the United States. This study was carried out at 265 intermittent streams by evaluating: (1) correlations among time series of flow metrics (number of zero-flow events, the average of the central 50% and largest 10% of flows) with precipitation (magnitudes, durations and intensity) and temperature, and (2) decadal changes in the seasonality and long-term trends of these flow metrics. Results identified five distinct seasonal patterns of flow intermittency: fall, fall-to-winter, non-seasonal, summer, and summer-to-winter intermittent streams. In addition, strong associations between the low-flow metrics and historical climate variability were found. However, the lack of trends in historical variations in precipitation results in no significant seasonal shifts or decade-to-decade trends in the low-flow metrics over the period of record (1950 to 2013).

Interannual Variability of Regional Hadley Circulation Intensity Over Western Pacific During Boreal Winter and Its Climatic Impact Over Asia-Australia Region

NASA Astrophysics Data System (ADS)

Huang, Ruping; Chen, Shangfeng; Chen, Wen; Hu, Peng

2018-01-01

This study investigates interannual variability of boreal winter regional Hadley circulation over western Pacific (WPHC) and its climatic impacts. A WPHC intensity index (WPHCI) is defined as the vertical shear of the divergent meridional winds. It shows that WPHCI correlates well with the El Niño-Southern Oscillation (ENSO). To investigate roles of the ENSO-unrelated part of WPHCI (WPHCIres), variables that are linearly related to the Niño-3 index have been removed. It reveals that meridional sea surface temperature gradient over the western Pacific plays an essential role in modulating the WPHCIres. The climatic impacts of WPHCIres are further investigated. Below-normal (above-normal) precipitation appears over south China (North Australia) when WPHCIres is stronger. This is due to the marked convergence (divergence) anomalies at the upper troposphere, divergence (convergence) at the lower troposphere, and the accompanied downward (upward) motion over south China (North Australia), which suppresses (enhances) precipitation there. In addition, a pronounced increase in surface air temperature (SAT) appears over south and central China when WPHCIres is stronger. A temperature diagnostic analysis suggests that the increase in SAT tendency over central China is primarily due to the warm zonal temperature advection and subsidence-induced adiabatic heating. In addition, the increase in SAT tendency over south China is primarily contributed by the warm meridional temperature advection. Further analysis shows that the correlation of WPHCIres with the East Asian winter monsoon (EAWM) is weak. Thus, this study may provide additional sources besides EAWM and ENSO to improve understanding of the Asia-Australia climate variability.

North Atlantic storm track variability and its association to the North Atlantic oscillation and climate variability of northern Europe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rogers, J.C.

The primary mode of North Atlantic track variability is identified using rotated principal component analysis (RPCA) on monthly fields of root-mean-squares of daily high-pass filtered (2-8-day periods) sea level pressures (SLP) for winters (December-February) 1900-92. It is examined in terms of its association with (1) monthly mean SLP fields, (2) regional low-frequency teleconnections, and (3) the seesaw in winter temperatures between Greenland and northern Europe. 32 refs., 9 figs.

Mid-latitude shrub steppe plant communities: Climate change consequences for soil water resources

USGS Publications Warehouse

Palmquist, Kyle A.; Schlaepfer, Daniel R.; Bradford, John B.; Lauenroth, Willliam K.

2016-01-01

In the coming century, climate change is projected to impact precipitation and temperature regimes worldwide, with especially large effects in drylands. We use big sagebrush ecosystems as a model dryland ecosystem to explore the impacts of altered climate on ecohydrology and the implications of those changes for big sagebrush plant communities using output from 10 Global Circulation Models (GCMs) for two representative concentration pathways (RCPs). We ask: 1) What is the magnitude of variability in future temperature and precipitation regimes among GCMs and RCPs for big sagebrush ecosystems and 2) How will altered climate and uncertainty in climate forecasts influence key aspects of big sagebrush water balance? We explored these questions across 1980-2010, 2030-2060, and 2070-2100 to determine how changes in water balance might develop through the 21st century. We assessed ecohydrological variables at 898 sagebrush sites across the western US using a process-based soil water model, SOILWAT to model all components of daily water balance using site-specific vegetation parameters and site-specific soil properties for multiple soil layers. Our modeling approach allowed for changes in vegetation based on climate. Temperature increased across all GCMs and RCPs, while changes in precipitation were more variable across GCMs. Winter and spring precipitation was predicted to increase in the future (7% by 2030-2060, 12% by 2070-2100), resulting in slight increases in soil water potential (SWP) in winter. Despite wetter winter soil conditions, SWP decreased in late spring and summer due to increased evapotranspiration (6% by 2030-2060, 10% by 2070-2100) and groundwater recharge (26% and 30% increase by 2030-2060 and 2070-2100). Thus, despite increased precipitation in the cold season, soils may dry out earlier in the year, resulting in potentially longer drier summer conditions. If winter precipitation cannot offset drier summer conditions in the future, we expect big sagebrush regeneration and survival will be negatively impacted, potentially resulting in shifts in the relative abundance of big sagebrush plant functional groups. Our results also highlight the importance of assessing multiple GCMs to understand the range of climate change outcomes on ecohydrology, which was contingent on the GCM chosen.

Impacts of Future Climate and Emission Changes on U.S. Air Quality

DOE Office of Scientific and Technical Information (OSTI.GOV)

Penrod, Ashley; Zhang, Yang; Wang, K.

2014-06-01

Changes in climate and emissions will affect future air quality. In this work, simulations of present (2001-2005) and future (2026-2030) regional air quality are conducted with the newly released CMAQ version 5.0 to examine the individual and combined impacts of simulated future climate and anthropogenic emission projections on air quality over the U.S. Current (2001-2005) meteorological and chemical predictions are evaluated against observational data to assess the model’s capability in reproducing the seasonal differences. Overall, WRF and CMAQ perform reasonably well. Increased temperatures (up to 3.18 °C) and decreased ventilation (up to 157 m in planetary boundary layer height) aremore » found in both future winter and summer, with more prominent changes in winter. Increases in future temperatures result in increased isoprene and terpene emissions in winter and summer, driving the increase in maximum 8-h average O3 (up to 5.0 ppb) over the eastern U.S. in winter while decreases in NOx emissions drive the decrease in O3 over most of the U.S. in summer. Future concentrations of PM2.5 in winter and summer and many of its components including organic matter in winter, ammonium and nitrate in summer, and sulfate in winter and summer, decrease due to decreases in primary anthropogenic emissions and the concentrations of secondary anthropogenic pollutants and increased precipitation in winter. Future winter and summer dry and wet deposition fluxes are spatially variable and increase with increasing surface resistance and precipitation (e.g., NH4+ and NO3- dry and wet deposition fluxes increase in winter over much of the U.S.), respectively, and decrease with a decrease in ambient particulate concentrations (e.g., SO42- dry and wet deposition fluxes decrease over the eastern U.S. in summer and winter). Sensitivity simulations show that anthropogenic emission projections dominate over changes in climate in their impacts on the U.S. air quality in the near future. Changes in some regions/species, however, are dominated by climate and/or both climate and anthropogenic emissions, especially in future years that are marked by meteorological conditions conducive to poor air quality.« less

The role of internal variability in prolonging the California drought

NASA Astrophysics Data System (ADS)

Buenning, N. H.; Stott, L. D.

2015-12-01

The current drought in California has been one of the driest on record. Using atmospheric general circulation models (AGCMs), recent studies have demonstrated that the low precipitation anomalies observed during the first three winters of the current drought are mostly attributable to changes in sea surface temperature (SST) and sea ice forcing. Here we show through AGCM simulations that the fourth and latest winter of the current drought is not attributable to SST and sea ice forcing, but instead a consequence of higher internal variability. Using the Global Spectral Model (GSM) we demonstrate how the surface forcing reproduces dry conditions over California for the first three winters of the current drought, similar to what other models produced. However, when forced with the SST and sea ice conditions for the winter of 2014-2015, GSM robustly simulates high precipitation conditions over California. This significantly differs with observed precipitation anomalies, which suggests a model deficiency or large influence of internal variability within the climate system during the winter of 2014-2015. Ensemble simulations with 234 realizations reveal that the surface forcing created a broader range of precipitation possibilities over California. Thus, the surface forcing caused a greater degree of internal variations, which was driven by a reduced latitudinal temperature gradient and amplified planetary waves over the Pacific. Similar amplified waves are also seen in 21st century climate projections of upper-level geopotential heights, suggesting that 21st century precipitation over California will become more variable and increasingly difficult to predict on seasonal timescales. When an El Nino pattern is applied to the surface forcing the precipitation further increases and the variance amongst model realizations is reduced, which indicates a strong likelihood of an anomalously wet 2015-2016 winter season.

Decreased winter severity increases viability of a montane frog population

PubMed Central

McCaffery, Rebecca M.; Maxell, Bryce A.

2010-01-01

Many proximate causes of global amphibian declines have been well documented, but the role that climate change has played and will play in this crisis remains ambiguous for many species. Breeding phenology and disease outbreaks have been associated with warming temperatures, but, to date, few studies have evaluated effects of climate change on individual vital rates and subsequent population dynamics of amphibians. We evaluated relationships among local climate variables, annual survival and fecundity, and population growth rates from a 9-year demographic study of Columbia spotted frogs (Rana luteiventris) in the Bitterroot Mountains of Montana. We documented an increase in survival and breeding probability as severity of winter decreased. Therefore, a warming climate with less severe winters is likely to promote population viability in this montane frog population. More generally, amphibians and other ectotherms inhabiting alpine or boreal habitats at or near their thermal ecological limits may benefit from the milder winters provided by a warming climate as long as suitable habitats remain intact. A more thorough understanding of how climate change is expected to benefit or harm amphibian populations at different latitudes and elevations is essential for determining the best strategies to conserve viable populations and allow for gene flow and shifts in geographic range. PMID:20421473

Windowpane flounder (Scophthalmus aquosus) and winter flounder (Pseudopleuronectes americanus) responses to cold temperature extremes in a Northwest Atlantic estuary

NASA Astrophysics Data System (ADS)

Wilber, Dara H.; Clarke, Douglas G.; Alcoba, Catherine M.; Gallo, Jenine

2016-01-01

The effect of climate variability on flatfish includes not only the effects of warming on sensitive life history stages, but also impacts from more frequent or unseasonal extreme cold temperatures. Cold weather events can affect the overwintering capabilities of flatfish near their low temperature range limits. We examined the responses of two flatfish species, the thin-bodied windowpane (Scophthalmus aquosus) and cold-tolerant winter flounder (Pseudopleuronectes americanus), to variable winter temperatures in a Northwest Atlantic estuary using abundance and size data collected during a monitoring study, the Aquatic Biological Survey, conducted from 2002 to 2010. Winter and spring abundances of small (50 to 120 mm total length) juvenile windowpane were positively correlated with adult densities (spawning stock) and fall temperatures (thermal conditions experienced during post-settlement development for the fall-spawned cohort) of the previous year. Windowpane abundances in the estuary were significantly reduced and the smallest size class was nearly absent after several consecutive years with cold (minimum temperatures < 1 °C) winters. Interannual variation in winter flounder abundances was unrelated to the severity of winter temperatures. A Paulik diagram illustrates strong positive correlations between annual abundances of sequential winter flounder life history stages (egg, larval, Age-1 juvenile, and adult male) within the estuary, reflecting residency within the estuary through their first year of life. Temperature variables representing conditions during winter flounder larval and post-settlement development were not significant factors in multiple regression models exploring factors that affect juvenile abundances. Likewise, densities of predators known to consume winter flounder eggs and/or post-settlement juveniles were not significantly related to interannual variation in winter flounder juvenile abundances. Colder estuarine temperatures through the first year of life were associated with smaller Age-1 winter flounder body size. For example, Age-1 winter flounder developing under conditions that differed by 1.9 °C in mean daily water temperature, averaged 98.7 mm total length (TL) and 123.1 mm TL, for the relatively cold vs. moderate years, respectively. More frequent cold temperature extremes associated with climate variability may negatively impact the overwintering capabilities of some flatfish near their cold temperature range limits, whereas cold-tolerant species may experience reduced growth, which imparts the ecological challenges associated with smaller body size.

A Multi-sensor Approach to Identify Crop Sensitivity Related to Climate Variability in Central India

NASA Astrophysics Data System (ADS)

Mondal, P.; DeFries, R. S.; Jain, M.; Robertson, A. W.; Galford, G. L.; Small, C.

2012-12-01

Agriculture is a primary source of livelihood for over 70% of India's population, with staple crops (e.g. winter wheat) playing a pivotal role in satisfying an ever-increasing food-demand of a growing population. Agricultural yield in India has been reported to be highly correlated with the timing and total amount of monsoon rainfall and/or temperature depending on crop type. With expected change in future climate (temperature and precipitation), significant fluctuations in crop yields are projected for near future. To date, little work has identified the sensitivity of cropping intensity, or the number of crops planted in a given year, to climate variability. The objective of this study is to shed light on relative importance of different climate parameters through a statistical analysis of inter-annual variations in cropping intensity at a regional scale, which may help identify adaptive strategies in response to future climate anomalies. Our study focuses on a highly human-modified landscape in central India, and uses a multi-sensor approach to determine the sensitivity of agriculture to climate variability. First, we assembled the 16-day time-series of 250m Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI), and applied a spline function-based smoothing algorithm to develop maps of monsoon and winter crops in Central India for a decadal time-span. A hierarchical model involving moderate resolution Landsat (30m) data was used to estimate the heterogeneity of the spectral signature within the MODIS dataset (250m). We then compared the season-specific cropping patterns with spatio-temporal variability in climate parameters derived from the Tropical Rainfall Measuring Mission (TRMM) data. Initial data indicates that the existence of a monsoon crop has moderate to strong correlation with wet season end date (ρ = .522), wet season length (ρ = .522), and the number of rainy days during wet season (ρ = .829). Existence of a winter crop, however, has a moderately strong correlation with wet season start date (ρ = .577). In addition, winter crop yield (ton/ha) has a moderate correlation with wet season end date (ρ = .624), number of rainy days during the wet season (ρ = .492), and during the dry season (ρ = .410). Future work will assess which other factors influence cropping intensity (e.g. access to irrigation among many other), since a complex interplay of bio-physical and socio-economic factors governs the decision-making at the farm-level, ultimately leading to inter-annual variability in cropping intensity and/or yield.

Atmospheric teleconnections between the Arctic and the Baltic Sea regions

NASA Astrophysics Data System (ADS)

Jakobson, L.; Jakobson, E.

2017-12-01

The observed enhanced warming of the Arctic, referred to as the AA, is expected to be related to further changes that impact mid-latitudes and the rest of the world. Our aim is to clarify how the climatic parameters in the Baltic Sea and Arctic regions are associated. Knowledge of such connections helps to define regions in the Arctic that could be with higher extent associated with the Baltic Sea region climate change. We used monthly mean reanalysis data from NCEP-CFSR and ERA-Interim. The strongest teleconnections between the same parameter (temperature, SLP, specific humidity, wind speed) at the Baltic Sea region and the Arctic are found in winter, but they are clearly affected by the Arctic Oscillation (AO) index. After removal of the AO index variability, correlations in winter were everywhere below ±0.5, while in other seasons there remained regions with strong (|R|>0.5, p<0.002) correlations. Strong correlations are also present between different climate variables at the Baltic Sea region and different regions of the Arctic. Temperature from 1000 to 500 hPa level at the Baltic Sea region have a strong negative correlation with the Greenland sector (the region between 20 - 80W and 55 - 80N) during all seasons except summer. The positive temperature anomaly of mild winter at the Greenland sector shifts towards east during the next seasons, reaching to Scandinavia/Baltic Sea region in summer. The Greenland sector is the region which gives the most significant correlations with the climatic parameters (temperature, wind speed, specific humidity, SLP) of the Baltic Sea region. These relationships can be explained by the AO index variability only in winter. In other seasons there has to be other influencing factors. The results of this study are valuable for selecting regions in the Arctic that have statistically the largest effect on climate in the Baltic Sea region.

Global meteorological influences on the record UK rainfall of winter 2013-14

NASA Astrophysics Data System (ADS)

Knight, Jeff R.; Maidens, Anna; Watson, Peter A. G.; Andrews, Martin; Belcher, Stephen; Brunet, Gilbert; Fereday, David; Folland, Chris K.; Scaife, Adam A.; Slingo, Julia

2017-07-01

The UK experienced record average rainfall in winter 2013-14, leading to widespread and prolonged flooding. The immediate cause of this exceptional rainfall was a very strong and persistent cyclonic atmospheric circulation over the North East Atlantic Ocean. This was related to a very strong North Atlantic jet stream which resulted in numerous damaging wind storms. These exceptional meteorological conditions have led to renewed questions about whether anthropogenic climate change is noticeably influencing extreme weather. The regional weather pattern responsible for the extreme UK winter coincided with highly anomalous conditions across the globe. We assess the contributions from various possible remote forcing regions using sets of ocean-atmosphere model relaxation experiments, where winds and temperatures are constrained to be similar to those observed in winter 2013-14 within specified atmospheric domains. We find that influences from the tropics were likely to have played a significant role in the development of the unusual extra-tropical circulation, including a role for the tropical Atlantic sector. Additionally, a stronger and more stable stratospheric polar vortex, likely associated with a strong westerly phase of the stratospheric Quasi-Biennial Oscillation (QBO), appears to have contributed to the extreme conditions. While intrinsic climatic variability clearly has the largest effect on the generation of extremes, results from an analysis which segregates circulation-related and residual rainfall variability suggest that emerging climate change signals made a secondary contribution to extreme rainfall in winter 2013-14.

Assessing performance and seasonal bias of pollen-based climate reconstructions in a perfect model world

NASA Astrophysics Data System (ADS)

Rehfeld, Kira; Trachsel, Mathias; Telford, Richard J.; Laepple, Thomas

2016-12-01

Reconstructions of summer, winter or annual mean temperatures based on the species composition of bio-indicators such as pollen, foraminifera or chironomids are routinely used in climate model-proxy data comparison studies. Most reconstruction algorithms exploit the joint distribution of modern spatial climate and species distribution for the development of the reconstructions. They rely on the space-for-time substitution and the specific assumption that environmental variables other than those reconstructed are not important or that their relationship with the reconstructed variable(s) should be the same in the past as in the modern spatial calibration dataset. Here we test the implications of this "correlative uniformitarianism" assumption on climate reconstructions in an ideal model world, in which climate and vegetation are known at all times. The alternate reality is a climate simulation of the last 6000 years with dynamic vegetation. Transient changes of plant functional types are considered as surrogate pollen counts and allow us to establish, apply and evaluate transfer functions in the modeled world. We find that in our model experiments the transfer function cross validation r2 is of limited use to identify reconstructible climate variables, as it only relies on the modern spatial climate-vegetation relationship. However, ordination approaches that assess the amount of fossil vegetation variance explained by the reconstructions are promising. We furthermore show that correlations between climate variables in the modern climate-vegetation relationship are systematically extended into the reconstructions. Summer temperatures, the most prominent driving variable for modeled vegetation change in the Northern Hemisphere, are accurately reconstructed. However, the amplitude of the model winter and mean annual temperature cooling between the mid-Holocene and present day is overestimated and similar to the summer trend in magnitude. This effect occurs because temporal changes of a dominant climate variable, such as summer temperatures in the model's Arctic, are imprinted on a less important variable, leading to reconstructions biased towards the dominant variable's trends. Our results, although based on a model vegetation that is inevitably simpler than reality, indicate that reconstructions of multiple climate variables based on modern spatial bio-indicator datasets should be treated with caution. Expert knowledge on the ecophysiological drivers of the proxies, as well as statistical methods that go beyond the cross validation on modern calibration datasets, are crucial to avoid misinterpretation.

Marine Climate Archives across the Medieval Climate Anomaly-Little Ice Age Transition from Viking and Medieval Age Shells, Orkney, Scotland

NASA Astrophysics Data System (ADS)

Surge, D. M.; Barrett, J. H.

2013-12-01

Proxy records reconstructing marine climatic conditions across the transition between the Medieval Climate Anomaly (MCA; ~900-1350 AD) and Little Ice Age (LIA; ~1350-1850) are strongly biased towards decadal to annual resolution and summer/growing seasons. Here we present new archives of seasonal variability in North Atlantic sea surface temperature (SST) from shells of the European limpet, Patella vulgata, which accumulated in Viking and medieval shell and fish middens at Quoygrew on Westray, Orkney. SST was reconstructed at submonthly resolution using oxygen isotope ratios preserved in shells from the 12th and mid 15th centuries (MCA and LIA, respectively). MCA shells recorded warmer summers and colder winters by ~2 degrees C relative to the late 20th Century (1961-1990). Therefore, seasonality was higher during the MCA relative to the late 20th century. Without the benefit of seasonal resolution, SST averaged from shell time series would be weighted toward the fast-growing summer season, resulting in the conclusion that the early MCA was warmer than the late 20th century by ~1°C. This conclusion is broadly true for the summer season, but not true for the winter season. Higher seasonality and cooler winters during early medieval times may result from a weakened North Atlantic Oscillation index. In contrast, the LIA shells have a more a variable inter-annual pattern. Some years record cooler summers and winters relative to the MCA shells and late 20th century, whereas other years record warmer summers and cooler winters similar to the MCA shells. Our findings provide a new test for the accuracy of seasonal amplitudes resulting from paleoclimate model experiments.

Paleoclimate of the Neoglacial and Roman Warm Period Reconstructed from Oxygen Isotope Ratios of Limpet Shells (Patella vulgata), Northwest Scotland

NASA Astrophysics Data System (ADS)

Wang, T.; Surge, D. M.; Mithen, S.

2010-12-01

Paleoclimate reconstructions from different regions have reported abrupt climate change around 2800-2700 cal yr B.P. The timing of this abrupt climate change is close to the boundary between the Neoglacial (3300-2500 cal yr B.P.) and Roman Warm Period (2500-1600 cal yr B.P.). However, temporal and spatial variability observed in this climate change event raises controversies about the forcing factors driving it and why it has regional variability. Scotland lies in the North Atlantic Ocean, which responds sensitively to climate change. Therefore, even in the case of subtle climate change, the climate variability of Scotland should be able to capture such change. In this study, we expect that paleoclimate reconstructions of the Neoglacial and Roman Warm Period in Scotland will help improve our knowledge of abrupt climate change at 2800-2700 cal yr B.P. Archaeological shell deposits provide a rich source of climate proxy data preserved as oxygen isotope ratios in shell carbonate. Croig Cave on the Isle of Mull, Scotland, contains a nearly continuous accumulation of shells ranging from 800 BC-500 AD and possibly older. This range represents a broad chronology of human use from the late Bronze to Iron Ages and spans the Neoglacial through Roman Warm Period climate episodes. Here, we present seasonal temperature variability of the two climate episodes based on oxygen isotope ratios of ten limpet shells (Patella vulgata) from Croig Cave. Based on AMS dating (2 sigma calibration), the oldest shell was from 3480-3330 cal yr B.P. and the youngest shell was from 2060-1870 cal yr B.P. Our results indicated that estimated temperatures from the Neoglacial limpets average 6.44±0.56°C for coldest winters and 15.06±0.67°C for warmest summers. For the Roman Warm Period limpets, the average is 5.68±0.36°C for coldest winters and 14.14±0.81°C for warmest summers. We compared our estimated temperatures to the present sea surface temperature (SST) from 1961 to 1990 near our study area, which averages 7.40±0.35°C for coldest month and 14.12±0.54°C for warmest month. Our reconstructed temperatures from the Neoglacial limpets showed slightly (0-1°C) colder winters, similar or warmer (1-1.8°C) summers compared to present SST record. One shell captured a year without a summer likely resulting from an eruption of the Katla volcanic system in Iceland. The reconstructed temperatures from the Roman Warm Period limpets showed colder winters (up to 2°C) and similar summers compared with present SST record. Our findings represent the first insights of SST variability at seasonal time scales for these two climate episodes in northwest Scotland.

Maritime climate influence on chaparral composition and diversity in the coast range of central California.

PubMed

Vasey, Michael C; Parker, V Thomas; Holl, Karen D; Loik, Michael E; Hiatt, Seth

2014-09-01

We investigated the hypothesis that maritime climatic factors associated with summer fog and low cloud stratus (summer marine layer) help explain the compositional diversity of chaparral in the coast range of central California. We randomly sampled chaparral species composition in 0.1-hectare plots along a coast-to-interior gradient. For each plot, climatic variables were estimated and soil samples were analyzed. We used Cluster Analysis and Principle Components Analysis to objectively categorize plots into climate zone groups. Climate variables, vegetation composition and various diversity measures were compared across climate zone groups using ANOVA and nonmetric multidimensional scaling. Differences in climatic variables that relate to summer moisture availability and winter freeze events explained the majority of variance in measured conditions and coincided with three chaparral assemblages: maritime (lowland coast where the summer marine layer was strongest), transition (upland coast with mild summer marine layer influence and greater winter precipitation), and interior sites that generally lacked late summer water availability from either source. Species turnover (β-diversity) was higher among maritime and transition sites than interior sites. Coastal chaparral differs from interior chaparral in having a higher obligate seeder to facultative seeder (resprouter) ratio and by being dominated by various Arctostaphylos species as opposed to the interior dominant, Adenostoma fasciculatum. The maritime climate influence along the California central coast is associated with patterns of woody plant composition and β-diversity among sites. Summer fog in coastal lowlands and higher winter precipitation in coastal uplands combine to lower late dry season water deficit in coastal chaparral and contribute to longer fire return intervals that are associated with obligate seeders and more local endemism. Soil nutrients are comparatively less important in explaining plant community composition, but heterogeneous azonal soils contribute to local endemism and promote isolated chaparral patches within the dominant forest vegetation along the coast.

Analysis of rainfall and temperature time series to detect long-term climatic trends and variability over semi-arid Botswana

NASA Astrophysics Data System (ADS)

Byakatonda, Jimmy; Parida, B. P.; Kenabatho, Piet K.; Moalafhi, D. B.

2018-03-01

Arid and semi-arid environments have been identified with locations prone to impacts of climate variability and change. Investigating long-term trends is one way of tracing climate change impacts. This study investigates variability through annual and seasonal meteorological time series. Possible inhomogeneities and years of intervention are analysed using four absolute homogeneity tests. Trends in the climatic variables were determined using Mann-Kendall and Sen's Slope estimator statistics. Association of El Niño Southern Oscillation (ENSO) with local climate is also investigated through multivariate analysis. Results from the study show that rainfall time series are fully homogeneous with 78.6 and 50% of the stations for maximum and minimum temperature, respectively, showing homogeneity. Trends also indicate a general decrease of 5.8, 7.4 and 18.1% in annual, summer and winter rainfall, respectively. Warming trends are observed in annual and winter temperature at 0.3 and 1.5% for maximum temperature and 1.7 and 6.5% for minimum temperature, respectively. Rainfall reported a positive correlation with Southern Oscillation Index (SOI) and at the same time negative association with Sea Surface Temperatures (SSTs). Strong relationships between SSTs and maximum temperature are observed during the El Niño and La Niña years. These study findings could facilitate planning and management of agricultural and water resources in Botswana.

Seasonal climate variability in Medieval Europe (1000 to 1499)

NASA Astrophysics Data System (ADS)

Pfister, C.

2009-04-01

In his fundamental work on medieval climate Alexandre (1987) highlighted the significance of dealing with contemporary sources. Recently, long series of temperature indices for "summer" and "winter" were set up by Shabalova and van Engelen (2003) for the Low Countries, but the time resolution is not strictly seasonal. This paper worked out within the EU 6th Framework Project "Millennium" draws on critically reviewed documentary evidence from a spatially extensive area of Western and Central Europe (basically England, France, BENELUX, Western Germany, Switzerland, Austria, Poland, Hungary and todays Czech Republic. The narrative evidence is complemented with dendro-climatic series from the Alps (Büntgen et al. 2006). Each "climate observation" is georeferenced which allows producing spatial displays of the data for selected spaces and time-frames. The spatial distribution of the information charts can be used as a tool for the climatological verification of the underlying data. Reconstructions for winter (DJF) and summer (JJA) are presented in the form of time series and charts. Cold winters were frequent from 1205 to 1235 i.e. in the "Medieval Warm Period" and in the Little Ice Age (1306-1330; 1390-1470). Dry and warm summers prevailed in Western and Central Europe in the first half of the 13th century. During the Little Ice Age cold-wet summers (triggered by volcanic explosions in the tropics) were more frequent, though summer climate remained highly variable. Results are discussed with regard to the "Greenhouse Debate" and the relationship to glacier fluctuations in the Alps is explored. References -Alexandre, Pierre, 1987: Le Climat en Europe au Moyen Age. Contribution à l'histoire des variations climatiques de 1000 à 1425. Paris. -Büntgen, Ulf et al. 2006: Summer Temperature Variation in the European Alps, AD. 755-2004, J. of Climate 19 5606-5623. - Pfister, Christian et al. 1998: Winter air temperature variations in Central Europe during the Early and Highe Middle Ages. The Holocene 8/1: 547-564. -Rohr, Christian, 2007: Extreme Naturereignisse im Ostalpenraum, Köln. -Shabalova, Marina ; van Engelen, Aryan, 2003: Evaluation of Reconstruction of Winter and Summer Temperatures in the Low Countries, AD 764-1998, Clim. Change 58 1-2, 219-242.

Effect of climate change on the irrigation and discharge scheme for winter wheat in Huaibei Plain, China

NASA Astrophysics Data System (ADS)

Zhu, Y.; Ren, L.; Lü, H.

2017-12-01

On the Huaibei Plain of Anhui Province, China, winter wheat (WW) is the most prominent crop. The study area belongs to transitional climate, with shallow water table. The original climate change is complex, in addition, global warming make the climate change more complex. The winter wheat growth period is from October to June, just during the rainless season, the WW growth always depends on part of irrigation water. Under such complex climate change, the rainfall varies during the growing seasons, and water table elevations also vary. Thus, water tables supply variable moisture change between soil water and groundwater, which impact the irrigation and discharge scheme for plant growth and yield. In Huaibei plain, the environmental pollution is very serious because of agricultural use of chemical fertilizer, pesticide, herbicide and etc. In order to protect river water and groundwater from pollution, the irrigation and discharge scheme should be estimated accurately. Therefore, determining the irrigation and discharge scheme for winter wheat under climate change is important for the plant growth management decision-making. Based on field observations and local weather data of 2004-2005 and 2005-2006, the numerical model HYDRUS-1D was validated and calibrated by comparing simulated and measured root-zone soil water contents. The validated model was used to estimate the irrigation and discharge scheme in 2010-2090 under the scenarios described by HadCM3 (1970 to 2000 climate states are taken as baselines) with winter wheat growth in an optimum state indicated by growth height and LAI.

Inter-annual Variability of Snowfall in the Lower Peninsula of Michigan, USA

NASA Astrophysics Data System (ADS)

Meng, L.

2016-12-01

Winter snowfall, particularly lake-effect snowfall, impacts all aspects of Michigan life in the wintertime, from motorsports and tourism to impacting the day-to-day lives of residents. Understanding the inter-annual variability of winter snowfall will provide sound basis for local community safety management and improve weather forecasting. This study attempts to understand the trend in winter snowfall and the influencing factors of winter snowfall variability in the Lower Peninsula of Michigan (LPM) using station snowfall measurements and statistical analysis. Our study demonstrates that snowfall has significantly increased from 1932 to 2015. Correlation analysis suggests that regionally average air temperatures have a strong negative relationship with snowfall in LPM. On average, approximately 27% of inter-annual variability in snowfall can be explained by regionally average air temperatures. ENSO events are also negatively related to snowfall in LPM and can explain 8% of inter-annual variability. North Atlantic Oscillation (NAO) does not have strong influence on snowfall. Composite analysis demonstrates that on annual basis, more winter snowfall occurs during the years with higher maximum ice cover (MIC) than during the years with lower MIC in Lake Michigan. Higher MIC is often associated with lower air temperatures which are negatively related to winter snowfall. This study could provide insight on future snow related climate model improvement and weather forecasting.

The subtle role of climate change on population genetic structure in Canada lynx.

PubMed

Row, Jeffrey R; Wilson, Paul J; Gomez, Celine; Koen, Erin L; Bowman, Jeff; Thornton, Daniel; Murray, Dennis L

2014-07-01

Anthropogenically driven climatic change is expected to reshape global patterns of species distribution and abundance. Given recent links between genetic variation and environmental patterns, climate change may similarly impact genetic population structure, but we lack information on the spatial and mechanistic underpinnings of genetic-climate associations. Here, we show that current genetic variability of Canada lynx (Lynx canadensis) is strongly correlated with a winter climate gradient (i.e. increasing snow depth and winter precipitation from west-to-east) across the Pacific-North American (PNO) to North Atlantic Oscillation (NAO) climatic systems. This relationship was stronger than isolation by distance and not explained by landscape variables or changes in abundance. Thus, these patterns suggest that individuals restricted dispersal across the climate boundary, likely in the absence of changes in habitat quality. We propose habitat imprinting on snow conditions as one possible explanation for this unusual phenomenon. Coupling historical climate data with future projections, we also found increasingly diverging snow conditions between the two climate systems. Based on genetic simulations using projected climate data (2041-2070), we predicted that this divergence could lead to a threefold increase in genetic differentiation, potentially leading to isolated east-west populations of lynx in North America. Our results imply that subtle genetic structure can be governed by current climate and that substantive genetic differentiation and related ecological divergence may arise from changing climate patterns. © 2014 John Wiley & Sons Ltd.

Climate Variability and Oceanographic Settings Associated with Interannual Variability in the Initiation of Dinophysis acuminata Blooms

PubMed Central

Díaz, Patricio A.; Reguera, Beatriz; Ruiz-Villarreal, Manuel; Pazos, Yolanda; Velo-Suárez, Lourdes; Berger, Henrick; Sourisseau, Marc

2013-01-01

In 2012, there were exceptional blooms of D. acuminata in early spring in what appeared to be a mesoscale event affecting Western Iberia and the Bay of Biscay. The objective of this work was to identify common climatic patterns to explain the observed anomalies in two important aquaculture sites, the Galician Rías Baixas (NW Spain) and Arcachon Bay (SW France). Here, we examine climate variability through physical-biological couplings, Sea Surface Temperature (SST) anomalies and time of initiation of the upwelling season and its intensity over several decades. In 2012, the mesoscale features common to the two sites were positive anomalies in SST and unusual wind patterns. These led to an atypical predominance of upwelling in winter in the Galician Rías, and increased haline stratification associated with a southward advection of the Gironde plume in Arcachon Bay. Both scenarios promoted an early phytoplankton growth season and increased stability that enhanced D. acuminata growth. Therefore, a common climate anomaly caused exceptional blooms of D. acuminata in two distant regions through different triggering mechanisms. These results increase our capability to predict intense diarrhetic shellfish poisoning outbreaks in the early spring from observations in the preceding winter. PMID:23959151

Tracing the effects of the Little Ice Age in the tropical lowlands of eastern Mesoamerica

PubMed Central

del Socorro Lozano-García, Ma.; Caballero, Margarita; Ortega, Beatriz; Rodríguez, Alejandro; Sosa, Susana

2007-01-01

The causes of late-Holocene centennial to millennial scale climatic variability and the impact that such variability had on tropical ecosystems are still poorly understood. Here, we present a high-resolution, multiproxy record from lowland eastern Mesoamerica, studied to reconstruct climate and vegetation history during the last 2,000 years, in particular to evaluate the response of tropical vegetation to the cooling event of the Little Ice Age (LIA). Our data provide evidence that the densest tropical forest cover and the deepest lake of the last two millennia were coeval with the LIA, with two deep lake phases that follow the Spörer and Maunder minima in solar activity. The high tropical pollen accumulation rates limit LIA's winter cooling to a maximum of 2°C. Tropical vegetation expansion during the LIA is best explained by a reduction in the extent of the dry season as a consequence of increased meridional flow leading to higher winter precipitation. These results highlight the importance of seasonal responses to climatic variability, a factor that could be of relevance when evaluating the impact of recent climate change. PMID:17913875

European seasonal mortality and influenza incidence due to winter temperature variability

NASA Astrophysics Data System (ADS)

Ballester, Joan; Rodó, Xavier; Robine, Jean-Marie; Herrmann, François Richard

2016-10-01

Recent studies have vividly emphasized the lack of consensus on the degree of vulnerability (see ref. ) of European societies to current and future winter temperatures. Here we consider several climate factors, influenza incidence and daily numbers of deaths to characterize the relationship between winter temperature and mortality in a very large ensemble of European regions representing more than 400 million people. Analyses highlight the strong association between the year-to-year fluctuations in winter mean temperature and mortality, with higher seasonal cases during harsh winters, in all of the countries except the United Kingdom, the Netherlands and Belgium. This spatial distribution contrasts with the well-documented latitudinal orientation of the dependency between daily temperature and mortality within the season. A theoretical framework is proposed to reconcile the apparent contradictions between recent studies, offering an interpretation to regional differences in the vulnerability to daily, seasonal and long-term winter temperature variability. Despite the lack of a strong year-to-year association between winter mean values in some countries, it can be concluded that warmer winters will contribute to the decrease in winter mortality everywhere in Europe.

1,500 year quantitative reconstruction of winter precipitation in the Pacific Northwest

PubMed Central

Steinman, Byron A.; Abbott, Mark B.; Mann, Michael E.; Stansell, Nathan D.; Finney, Bruce P.

2012-01-01

Multiple paleoclimate proxies are required for robust assessment of past hydroclimatic conditions. Currently, estimates of drought variability over the past several thousand years are based largely on tree-ring records. We produced a 1,500-y record of winter precipitation in the Pacific Northwest using a physical model-based analysis of lake sediment oxygen isotope data. Our results indicate that during the Medieval Climate Anomaly (MCA) (900–1300 AD) the Pacific Northwest experienced exceptional wetness in winter and that during the Little Ice Age (LIA) (1450–1850 AD) conditions were drier, contrasting with hydroclimatic anomalies in the desert Southwest and consistent with climate dynamics related to the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). These findings are somewhat discordant with drought records from tree rings, suggesting that differences in seasonal sensitivity between the two proxies allow a more compete understanding of the climate system and likely explain disparities in inferred climate trends over centennial timescales. PMID:22753510

Climate-driven diversity change in annual grasslands: Drought plus deluge does not equal normal.

PubMed

Harrison, Susan P; LaForgia, Marina L; Latimer, Andrew M

2018-04-01

Climate forecasts agree that increased variability and extremes will tend to reduce the availability of water in many terrestrial ecosystems. Increasingly severe droughts may be exacerbated both by warmer temperatures and by the relative unavailability of water that arrives in more sporadic and intense rainfall events. Using long-term data and an experimental water manipulation, we examined the resilience of a heterogeneous annual grassland community to a prolonged series of dry winters that led to a decline in plant species richness (2000-2014), followed by a near-record wet winter (2016-2017), a climatic sequence that broadly resembles the predicted future in its high variability. In our 80, 5-m 2 observational plots, species richness did not recover in response to the wet winter, and the positive relationship of richness to annual winter rainfall thus showed a significant weakening trend over the 18-year time period. In experiments on 100, 1-m 2 plots, wintertime water supplementation increased and drought shelters decreased the seedling survival and final individual biomass of native annual forbs, the main functional group contributing to the observed long-term decline in richness. Water supplementation also increased the total cover of native annual forbs, but only increased richness within nested subplots to which seeds were also added. We conclude that prolonged dry winters, by increasing seedling mortality and reducing growth of native forbs, may have diminished the seedbank and thus the recovery potential of diversity in this community. However, the wet winter and the watering treatment did cause recovery of the community mean values of a key functional trait (specific leaf area, an indicator of drought intolerance), suggesting that some aggregate community properties may be stabilized by functional redundancy among species. © 2017 John Wiley & Sons Ltd.

Distant Influence of Kuroshio Eddies on North Pacific Weather Patterns?

PubMed Central

Ma, Xiaohui; Chang, Ping; Saravanan, R.; Montuoro, Raffaele; Hsieh, Jen-Shan; Wu, Dexing; Lin, Xiaopei; Wu, Lixin; Jing, Zhao

2015-01-01

High-resolution satellite measurements of surface winds and sea-surface temperature (SST) reveal strong coupling between meso-scale ocean eddies and near-surface atmospheric flow over eddy-rich oceanic regions, such as the Kuroshio and Gulf Stream, highlighting the importance of meso-scale oceanic features in forcing the atmospheric planetary boundary layer (PBL). Here, we present high-resolution regional climate modeling results, supported by observational analyses, demonstrating that meso-scale SST variability, largely confined in the Kuroshio-Oyashio confluence region (KOCR), can further exert a significant distant influence on winter rainfall variability along the U.S. Northern Pacific coast. The presence of meso-scale SST anomalies enhances the diabatic conversion of latent heat energy to transient eddy energy, intensifying winter cyclogenesis via moist baroclinic instability, which in turn leads to an equivalent barotropic downstream anticyclone anomaly with reduced rainfall. The finding points to the potential of improving forecasts of extratropical winter cyclones and storm systems and projections of their response to future climate change, which are known to have major social and economic impacts, by improving the representation of ocean eddy–atmosphere interaction in forecast and climate models. PMID:26635077

Soil water improvements with the long-term use of a winter rye cover crop

USDA-ARS?s Scientific Manuscript database

The Midwestern United States, a region that produces one-third of maize and one-quarter of soybeans globally, is projected to experience increasing rainfall variability with future climate change. One approach to mitigate climate impacts is to utilize crop and soil management practices that enhance ...

Climatic Influences on Southern Makassar Strait Salinity Over the Past Century

NASA Astrophysics Data System (ADS)

Murty, S. A.; Goodkin, N. F.; Halide, H.; Natawidjaja, D.; Suwargadi, B.; Suprihanto, I.; Prayudi, D.; Switzer, A. D.; Gordon, A. L.

2017-12-01

The Indonesian Throughflow (ITF) is a globally important ocean current that fuels heat and buoyancy fluxes throughout the Indo-Pacific and is known to covary in strength with the El Niño Southern Oscillation at interannual time scales. A climate system with a less well-quantified impact on the ITF is the East Asian Winter Monsoon (EAWM), which drives less saline surface waters from the South China Sea (SCS) into the Makassar Strait, obstructing surface ITF flow. We present a subannually resolved record of sea surface salinity (SSS) from 1927 to 2011 based on coral δ18O from the Makassar Strait that reveals variability in the relative contributions of different source waters to the surface waters of the Makassar Strait during the boreal winter monsoon. We find that the EAWM (January-March) strongly influences interannual SSS variability during boreal winter over the twentieth century (r = 0.54, p << 0.0001), impacting surface water circulation in the SCS and Indonesian Seas.

Relations between winter climatic variables and April streamflows in New England and implications for summer streamflows

USGS Publications Warehouse

Hodgkins, Glenn A.; Dudley, Robert W.; Schalk, Luther F.

2012-01-01

A period of much below normal streamflow in southern New England during April 2012 raised concerns that a long-term period of drought could evolve through late spring and summer, leading to potential water availability issues. To understand better the relations between winter climatic variables and April streamflows, April streamflows from 31 streamflow gages in New England that drain relatively natural watersheds were tested for year-to-year correlation with winter precipitation and air temperature from nearby meteorological sites. Higher winter (December through March) precipitation is associated with higher April streamflows at many gages in northern and central New England. This implies that snowpack accumulation is an important mechanism for winter water storage and subsequently important for spring streamflows in this area. Higher March air temperatures are associated with lower April streamflows at many gages in central and southern New England, likely because the majority of snowmelt runoff occurs before April in warm years. A warm March 2012 contributed to early snowmelt runoff in New England and to much below normal April streamflows in southern New England. However, no strong relation was found between historical April streamflows and late-spring or summer streamflows in New England. The lack of a strong relation implies that summer precipitation, rather than spring conditions, controls summer streamflows.

Winter Precipitation in North America and the Pacific-North America Pattern in GEOS-S2Sv2 Seasonal Hindcast

NASA Technical Reports Server (NTRS)

Li, Zhao; Molod, Andrea; Schubert, Siegfried

2018-01-01

Reliable prediction of precipitation remains one of the most pivotal and complex challenges in seasonal forecasting. Previous studies show that various large-scale climate modes, such as ENSO, PNA and NAO play significant role in winter precipitation variability over the Northern America. The influences are most pronounced in years of strong indices of such climate modes. This study evaluates model bias, predictability and forecast skills of monthly winter precipitation in GEOS5-S2S 2.0 retrospective forecast from 1981 to 2016, with emphasis on the forecast skill of precipitation over North America during the extreme events of ENSO, PNA and NAO by applying EOF and composite analysis.

Spatial Analysis of the Effects of the Anomalous Winter of 2014/15 on 157 Ski Resorts Located in Western North America

NASA Astrophysics Data System (ADS)

Bahbahani, K. M.; Pidwirny, M. J.

2017-12-01

The winter of 2014/2015 was one of the warmest in recent history for many locations in western North America. The cause of this climate irregularity was the development of extremely warm ocean surface waters (The Blob) over much of the eastern North Pacific Ocean. During this winter season, many ski resorts in western Canada and the United States either did not open or were forced to close their ski season early. Here, we examine climate data from 157 ski resorts to develop a picture of where the effected locations were in western North America. Using the climate database software ClimateBC and ClimateNA, high quality downscaled historical data was generated for the winter season (December, January, and February) for the variables mean temperature, snowfall, and rainfall. Values for winter of 2014/15 were statistically compared to the 30-year normal period from 1981-2010. Z-scores were calculated for 2014/15 relative to the selected 30-year normal period. These Z-score values were then mapped using ArcGIS. From the mean winter temperature map, it is apparent that abnormally warm temperatures influenced many ski resorts in California, Nevada, western Oregon, Washington, Arizona, Utah, southern Idaho, and parts of southern British Columbia. The winter snowfall map shows anomalous below normal conditions only at two resorts in south-central British Columbia and a single above normal situation at one site in central Colorado. The winter rainfall map displays that many ski resorts in New Mexico, Arizona, southern Utah, Colorado, Wyoming, Montana, Idaho, western Washington, and southwestern British Columbia experienced exceptional above normal winter season rainfalls. It is highly likely that the next Blob will be forecasted many months in advance of its occurrence. The results of this study have identified which ski resorts could be climatically influenced by such an event. This information may help reduce potential financial losses to ski resorts and their associated stakeholders when the next Blob shows up.

A robust empirical seasonal prediction of winter NAO and surface climate.

PubMed

Wang, L; Ting, M; Kushner, P J

2017-03-21

A key determinant of winter weather and climate in Europe and North America is the North Atlantic Oscillation (NAO), the dominant mode of atmospheric variability in the Atlantic domain. Skilful seasonal forecasting of the surface climate in both Europe and North America is reflected largely in how accurately models can predict the NAO. Most dynamical models, however, have limited skill in seasonal forecasts of the winter NAO. A new empirical model is proposed for the seasonal forecast of the winter NAO that exhibits higher skill than current dynamical models. The empirical model provides robust and skilful prediction of the December-January-February (DJF) mean NAO index using a multiple linear regression (MLR) technique with autumn conditions of sea-ice concentration, stratospheric circulation, and sea-surface temperature. The predictability is, for the most part, derived from the relatively long persistence of sea ice in the autumn. The lower stratospheric circulation and sea-surface temperature appear to play more indirect roles through a series of feedbacks among systems driving NAO evolution. This MLR model also provides skilful seasonal outlooks of winter surface temperature and precipitation over many regions of Eurasia and eastern North America.

Precipitation, temperature, and teleconnection signals across the combined North American, Monsoon Asia, and Old World Drought Atlases

NASA Astrophysics Data System (ADS)

Smerdon, J. E.; Baek, S. H.; Coats, S.; Williams, P.; Cook, B.; Cook, E. R.; Seager, R.

2017-12-01

The tree-ring-based North American Drought Atlas (NADA), Monsoon Asia Drought Atlas (MADA), and Old World Drought Atlas (OWDA) collectively yield a near-hemispheric gridded reconstruction of hydroclimate variability over the last millennium. To test the robustness of the large-scale representation of hydroclimate variability across the drought atlases, the joint expression of seasonal climate variability and teleconnections in the NADA, MADA, and OWDA are compared against two global, observation-based PDSI products. Predominantly positive (negative) correlations are determined between seasonal precipitation (surface air temperature) and collocated tree-ring-based PDSI, with average Pearson's correlation coefficients increasing in magnitude from boreal winter to summer. For precipitation, these correlations tend to be stronger in the boreal winter and summer when calculated for the observed PDSI record, while remaining similar for temperature. Notwithstanding these differences, the drought atlases robustly express teleconnection patterns associated with the El Niño-Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO). These expressions exist in the drought atlas estimates of boreal summer PDSI despite the fact that these modes of climate variability are dominant in boreal winter, with the exception of the Atlantic Multidecadal Oscillation. ENSO and NAO teleconnection patterns in the drought atlases are particularly consistent with their well-known dominant expressions in boreal winter and over the OWDA domain, respectively. Collectively, our findings confirm that the joint Northern Hemisphere drought atlases robustly reflect large-scale patterns of hydroclimate variability on seasonal to multidecadal timescales over the 20th century and are likely to provide similarly robust estimates of hydroclimate variability prior to the existence of widespread instrumental data.

Migratory connectivity and effects of winter temperatures on migratory behaviour of the European robin Erithacus rubecula: a continent-wide analysis.

PubMed

Ambrosini, Roberto; Cuervo, José Javier; du Feu, Chris; Fiedler, Wolfgang; Musitelli, Federica; Rubolini, Diego; Sicurella, Beatrice; Spina, Fernando; Saino, Nicola; Møller, Anders Pape

2016-05-01

Many partially migratory species show phenotypically divergent populations in terms of migratory behaviour, with climate hypothesized to be a major driver of such variability through its differential effects on sedentary and migratory individuals. Based on long-term (1947-2011) bird ringing data, we analysed phenotypic differentiation of migratory behaviour among populations of the European robin Erithacus rubecula across Europe. We showed that clusters of populations sharing breeding and wintering ranges varied from partial (British Isles and Western Europe, NW cluster) to completely migratory (Scandinavia and north-eastern Europe, NE cluster). Distance migrated by birds of the NE (but not of the NW) cluster decreased through time because of a north-eastwards shift in the wintering grounds. Moreover, when winter temperatures in the breeding areas were cold, individuals from the NE cluster also migrated longer distances, while those of the NW cluster moved over shorter distances. Climatic conditions may therefore affect migratory behaviour of robins, although large geographical variation in response to climate seems to exist. © 2016 The Authors. Journal of Animal Ecology © 2016 British Ecological Society.

Influence of winter season climate variability on snow-precipitation ratio in the western United States

Treesearch

Mohammad Safeeq; Shraddhanand Shukla; Ivan Arismendi; Gordon E. Grant; Sarah L. Lewis; Anne Nolin

2015-01-01

In the western United States, climate warming poses a unique threat to water and snow hydrology because much of the snowpack accumulates at temperatures near 0 °C. As the climate continues to warm, much of the region's precipitation is expected to switch from snow to rain, causing flashier hydrographs, earlier inflow to reservoirs, and reduced spring and summer...

The East Asian Jet Stream and Asian-Pacific-American Climate

NASA Technical Reports Server (NTRS)

Yang, Song; Lau, K.-M.; Kim, K.-M.

2000-01-01

The upper-tropospheric westerly jet stream over subtropical East Asia and western Pacific, often referred to as East Asian Jet (EAJ), is an important atmospheric circulation system in the Asian-Pacific-American (APA) region during winter. It is characterized by variabilities on a wide range of time scales and exerts a strong impact on the weather and climate of the region. On the synoptic scale, the jet stream is closely linked to many phenomena such as cyclogenesis, frontogenesis, blocking, storm track activity, and the development of other atmospheric disturbances. On the seasonal time scale, the variation of the EAJ determines many characteristics of the seasonal transition of the atmospheric circulation especially over East Asia. The variabilities of the EAJ on these time scales have been relatively well documented. It has also been understood since decades ago that the interannual. variability of the EAJ is associated with many climate signals in the APA region. These signals include the persistent anomalies of the East Asian winter monsoon and the changes in diabatic heating and in the Hadley circulation. However, many questions remain for the year-to-year variabilities of the EAJ and their relation to the APA climate. For example, what is the relationship between the EAJ and El Nino/Southern Oscillation (ENSO)? Will the EAJ and ENSO play different roles in modulating the APA climate? How is the jet stream linked to the non-ENSO-related sea surface temperature (SST) anomalies and to the Pacific/North American (PNA) teleconnection pattern?

Mid-latitude shrub steppe plant communities: climate change consequences for soil water resources.

PubMed

Palmquist, Kyle A; Schlaepfer, Daniel R; Bradford, John B; Lauenroth, William K

2016-09-01

In the coming century, climate change is projected to impact precipitation and temperature regimes worldwide, with especially large effects in drylands. We use big sagebrush ecosystems as a model dryland ecosystem to explore the impacts of altered climate on ecohydrology and the implications of those changes for big sagebrush plant communities using output from 10 Global Circulation Models (GCMs) for two representative concentration pathways (RCPs). We ask: (1) What is the magnitude of variability in future temperature and precipitation regimes among GCMs and RCPs for big sagebrush ecosystems, and (2) How will altered climate and uncertainty in climate forecasts influence key aspects of big sagebrush water balance? We explored these questions across 1980-2010, 2030-2060, and 2070-2100 to determine how changes in water balance might develop through the 21st century. We assessed ecohydrological variables at 898 sagebrush sites across the western US using a process-based soil water model, SOILWAT, to model all components of daily water balance using site-specific vegetation parameters and site-specific soil properties for multiple soil layers. Our modeling approach allowed for changes in vegetation based on climate. Temperature increased across all GCMs and RCPs, whereas changes in precipitation were more variable across GCMs. Winter and spring precipitation was predicted to increase in the future (7% by 2030-2060, 12% by 2070-2100), resulting in slight increases in soil water potential (SWP) in winter. Despite wetter winter soil conditions, SWP decreased in late spring and summer due to increased evapotranspiration (6% by 2030-2060, 10% by 2070-2100) and groundwater recharge (26% and 30% increase by 2030-2060 and 2070-2100). Thus, despite increased precipitation in the cold season, soils may dry out earlier in the year, resulting in potentially longer, drier summer conditions. If winter precipitation cannot offset drier summer conditions in the future, we expect big sagebrush regeneration and survival will be negatively impacted, potentially resulting in shifts in the relative abundance of big sagebrush plant functional groups. Our results also highlight the importance of assessing multiple GCMs to understand the range of climate change outcomes on ecohydrology, which was contingent on the GCM chosen. © 2016 by the Ecological Society of America.

Late Holocene SST and primary productivity variations in the northeastern Arabian Sea as a recorder for winter monsoon variability

NASA Astrophysics Data System (ADS)

Böll, Anna; Gaye, Birgit; Lückge, Andreas

2014-05-01

Variability in the oceanic environment of the Arabian Sea region is strongly influenced by the seasonal monsoon cycle of alternating wind directions. Strong south-westerly winds during the summer monsoon induce upwelling of nutrient rich waters along the coast off Somalia, Oman and southwest India, which result in high rates of primary production. In the northeastern Arabian Sea off Pakistan on the other hand, primary production and sea surface temperatures are linked to northeast monsoonal winds that cool the sea surface and drive convective mixing and high surface ocean productivity during the winter season. In this study, we analyzed alkenone-derived sea surface temperature (SST) variations and proxies of primary productivity (organic carbon and δ15N) in a well-laminated sediment core from the Pakistan continental margin to establish the first high-resolution record of winter monsoon variability for the late Holocene. Over the last 2400 years reconstructed SST in the northeastern Arabian Sea decreased whereas productivity increased, imaging a long-term trend of northeast monsoon strengthening in response to insolation-induced southward migration of the Intertropical Convergence Zone. The comparison of our winter monsoon record with records of summer monsoon intensity suggests that summer and winter monsoon strength was essentially anti-correlated over the late Holocene throughout the Asian monsoon system. In addition, SST variations recorded off Pakistan match very well with Northern Hemisphere temperature records supporting the growing body of evidence that Asian climate is linked to Northern Hemisphere climate change. It reveals a consistent pattern of increased summer monsoon activity in the northeastern Arabian Sea during northern hemispheric warm periods (Medieval Warm Period, Roman Warm Period) and strengthened winter monsoon activity during hemispheric colder periods (Little Ice Age).

Impact of climate change adaptation strategies on winter wheat and cropping system performance across precipitation gradients in the inland Pacific Northwest, USA

USDA-ARS?s Scientific Manuscript database

Ecological instability and low resource use efficiencies are concerns for the long-term productivity of conventional cereal monoculture systems, particularly those threatened by projected climate change. Crop intensification, diversification, reduced tillage, and variable N management are among str...

SENSITIVITY OF WINTER WHEAT YIELDS IN THE MIDWESTERN UNITED STATES TO FUTURE CHANGES IN CLIMATE, CLIMATE VARIABILITY, AND CO2 FERTILIZATION. (R824996)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

Climate variability in Andalusia (southern Spain) during the period 1701-1850 AD from documentary sources: evaluation and comparison with climate model simulations

NASA Astrophysics Data System (ADS)

Rodrigo, F. S.; Gómez-Navarro, J. J.; Montávez Gómez, J. P.

2011-07-01

In this work, a reconstruction of climatic conditions in Andalusia (southern Iberia Peninsula) during the period 1701-1850, as well as an evaluation of its associated uncertainties, is presented. This period is interesting because it is characterized by a minimum in the solar irradiance (Dalton Minimum, around 1800), as well as intense volcanic activity (for instance, the eruption of the Tambora in 1815), when the increasing atmospheric CO2 concentrations were of minor importance. The reconstruction is based on the analysis of a wide variety of documentary data. The reconstruction methodology is based on accounting the number of extreme events in past, and inferring mean value and standard deviation using the assumption of normal distribution for the seasonal means of climate variables. This reconstruction methodology is tested within the pseudoreality of a high-resolution paleoclimate simulation performed with the regional climate model MM5 coupled to the global model ECHO-G. Results show that the reconstructions are influenced by the reference period chosen and the threshold values used to define extreme values. This creates uncertainties which are assesed within the context of the climate simulation. An ensemble of reconstructions was obtained using two different reference periods and two pairs of percentiles as threshold values. Results correspond to winter temperature, and winter, spring, and autumn rainfall, and they are compared with simulations of the climate model for the considered period. The comparison of the distribution functions corresponding to 1790-1820 and 1960-1990 periods indicates that during the Dalton Minimum the frequency of dry and warm (wet and cold) winters was lesser (higher) than during the reference period. In spring and autumn it was detected an increase (decrease) in the frequency of wet (dry) seasons. Future research challenges are outlined.

Winter chilling speeds spring development of temperate butterflies.

PubMed

Stålhandske, Sandra; Gotthard, Karl; Leimar, Olof

2017-07-01

Understanding and predicting phenology has become more important with ongoing climate change and has brought about great research efforts in the recent decades. The majority of studies examining spring phenology of insects have focussed on the effects of spring temperatures alone. Here we use citizen-collected observation data to show that winter cold duration, in addition to spring temperature, can affect the spring emergence of butterflies. Using spatial mixed models, we disentangle the effects of climate variables and reveal impacts of both spring and winter conditions for five butterfly species that overwinter as pupae across the UK, with data from 1976 to 2013 and one butterfly species in Sweden, with data from 2001 to 2013. Warmer springs lead to earlier emergence in all species and milder winters lead to statistically significant delays in three of the five investigated species. We also find that the delaying effect of winter warmth has become more pronounced in the last decade, during which time winter durations have become shorter. For one of the studied species, Anthocharis cardamines (orange tip butterfly), we also make use of parameters determined from previous experiments on pupal development to model the spring phenology. Using daily temperatures in the UK and Sweden, we show that recent variation in spring temperature corresponds to 10-15 day changes in emergence time over UK and Sweden, whereas variation in winter duration corresponds to 20 days variation in the south of the UK versus only 3 days in the south of Sweden. In summary, we show that short winters delay phenology. The effect is most prominent in areas with particularly mild winters, emphasising the importance of winter for the response of ectothermic animals to climate change. With climate change, these effects may become even stronger and apply also at higher latitudes. © 2017 The Authors. Journal of Animal Ecology © 2017 British Ecological Society.

A tree-ring based reconstruction of North Pacific Jet variability and its influence on Sierra Nevada fire regimes

NASA Astrophysics Data System (ADS)

Trouet, V.; Babst, F.; Betancourt, J. L.

2013-12-01

Over the last decade, the northern hemisphere polar jet stream - the fast-flowing, high-altitude westerly air current that flows over mid and northern latitudes - has experienced a more meridional (north-south) and slower wave progression. This anomalous behavior contributed to extreme mid-latitude weather events across the globe, including drought and forest fires in the American Southwest (2012), summer heatwaves in Russia (2010), and floods in central and western Europe (2007). The position of the North Pacific Jet (NPJ) strongly modulates winter hydroclimatology in the Sierra Nevada and the Central Rocky Mountains; moreover, a persistent southerly (northerly) trajectory can offset (reinforce) losses in regional snowpack predicted with greenhouse warming . Snowpack variability has a fundamental impact on water resources and ecosystem disturbances. An increase in wildfire activity in the American West since the mid-1980s, for instance, has been related to decreasing snowpacks and earlier and faster snowmelt. Recent anomalous, high-amplitude, jet stream fluctuations are consistent with model projections forced by greenhouse gases. By weakening the pole-equator temperature gradient, enhanced Arctic warming in particular may cause the jet to slow and extreme weather patterns (e.g., blocking high pressure cells) to persist. Questions exist about the ability of climate models to simulate jet stream dynamics, however, and the instrumental record is still too short to fully evaluate the natural range of jet stream variability. We developed a reconstruction of winter NPJ variability from tree-ring data at two locations where climate is strongly influenced by the latitudinal NPJ position. We combined Blue Oak (Quercus douglasii) data from central California with climate-sensitive tree-ring series from multiple species in the northern Rockies in a nested PCA model that explained up to 41% of the variance in the instrumental NPJ target. The resulting reconstruction (1409-1990) demonstrates interannual to decadal-scale variability in the latitudinal position of the winter NPJ, and shows that its southern diplacement in recent decades (1991-2010) is unusual for the last 600 years. Furthermore, we found a strong relationship between reconstructed NPJ position and historical (1700-1850) fire activity in the Sierra Nevada, with increased (decreased) fire activity occurring after winters with an anomalously northerly (southerly) NPJ position. This relationship between winter climate and the normal fire season (July to October) is linked to the seasonal snowpack amounts and the timing of snowmelt and leafout, and is important in the prediction of problematic fire seasons.

Winter and spring climatic conditions influence timing and synchrony of calving in reindeer.

PubMed

Paoli, Amélie; Weladji, Robert B; Holand, Øystein; Kumpula, Jouko

2018-01-01

In a context of climate change, a mismatch has been shown to occur between some species' reproductive phenology and their environment. So far, few studies have either documented temporal trends in calving phenology or assessed which climatic variables influence the calving phenology in ungulate species, yet the phenology of ungulates' births affects offspring survival and population's recruitment rate. Using a long-term dataset (45 years) of birth dates of a semi-domesticated reindeer population in Kaamanen, North Finland, we show that calving season has advanced by ~ 7 days between 1970 and 2016. Advanced birth dates were associated with lower precipitation and a reduced snow cover in April and warmer temperatures in April-May. Improved females' physical condition in late gestation due to warmer temperatures in April-May and reduced snow conditions in April probably accounted for such advance in calving date. On the other hand, a lengthening of the calving season was reported following a warmer temperature in January, a higher number of days when mean temperature exceeds 0°C in October-November and a decreasing snow cover from October to November. By affecting the inter-individual heterogeneity in the plastic response of females' calving date to better climatic conditions in fall and winter, climatic variability contributed to weaken the calving synchrony in this herd. Whether variability in climatic conditions form environmental cues for the adaptation of calving phenology by females to climate change is however uncertain, but it is likely. As such this study enhances our understanding on how reproductive phenology of ungulate species would be affected by climate change.

Winter and spring climatic conditions influence timing and synchrony of calving in reindeer

PubMed Central

Paoli, Amélie; Holand, Øystein; Kumpula, Jouko

2018-01-01

In a context of climate change, a mismatch has been shown to occur between some species’ reproductive phenology and their environment. So far, few studies have either documented temporal trends in calving phenology or assessed which climatic variables influence the calving phenology in ungulate species, yet the phenology of ungulates’ births affects offspring survival and population’s recruitment rate. Using a long-term dataset (45 years) of birth dates of a semi-domesticated reindeer population in Kaamanen, North Finland, we show that calving season has advanced by ~ 7 days between 1970 and 2016. Advanced birth dates were associated with lower precipitation and a reduced snow cover in April and warmer temperatures in April-May. Improved females’ physical condition in late gestation due to warmer temperatures in April-May and reduced snow conditions in April probably accounted for such advance in calving date. On the other hand, a lengthening of the calving season was reported following a warmer temperature in January, a higher number of days when mean temperature exceeds 0°C in October-November and a decreasing snow cover from October to November. By affecting the inter-individual heterogeneity in the plastic response of females’ calving date to better climatic conditions in fall and winter, climatic variability contributed to weaken the calving synchrony in this herd. Whether variability in climatic conditions form environmental cues for the adaptation of calving phenology by females to climate change is however uncertain, but it is likely. As such this study enhances our understanding on how reproductive phenology of ungulate species would be affected by climate change. PMID:29694410

Northern Hemisphere Winter Climate Response to Greenhouse Gas, Ozone, Solar and Volcanic Forcing

NASA Technical Reports Server (NTRS)

Shindell, Drew T.; Schmidt, Gavin A.; Miller, Ron L.; Rind, David; Hansen, James E. (Technical Monitor)

2001-01-01

The Goddard Institute for Space Studies (GISS) climate/middle atmosphere model has been used to study the impacts of increasing greenhouse gases, polar ozone depletion, volcanic eruptions, and solar cycle variability. We focus on the projection of the induced responses onto Northern Hemisphere winter surface climate. Changes in the model's surface climate take place largely through enhancement of existing variability patterns, with greenhouse gases, polar ozone depletion and volcanic eruptions primarily affecting the Arctic Oscillation (AO) pattern. Perturbations descend from the stratosphere to the surface in the model by altering the propagation of planetary waves coming up from the surface, in accord with observational evidence. Models lacking realistic stratospheric dynamics fail to capture these wave flux changes. The results support the conclusion that the stratosphere plays a crucial role in recent AO trends. We show that in our climate model, while ozone depletion has a significant effect, greenhouse gas forcing is the only one capable of causing the large, sustained increase in the AO observed over recent decades. This suggests that the AO trend, and a concurrent strengthening of the stratospheric vortex over the Arctic, are very likely anthropogenic in origin.

East Asian winter monsoon forecasting schemes based on the NCEP's climate forecast system

NASA Astrophysics Data System (ADS)

Tian, Baoqiang; Fan, Ke; Yang, Hongqing

2017-12-01

The East Asian winter monsoon (EAWM) is the major climate system in the Northern Hemisphere during boreal winter. In this study, we developed two schemes to improve the forecasting skill of the interannual variability of the EAWM index (EAWMI) using the interannual increment prediction method, also known as the DY method. First, we found that version 2 of the NCEP's Climate Forecast System (CFSv2) showed higher skill in predicting the EAWMI in DY form than not. So, based on the advantage of the DY method, Scheme-I was obtained by adding the EAWMI DY predicted by CFSv2 to the observed EAWMI in the previous year. This scheme showed higher forecasting skill than CFSv2. Specifically, during 1983-2016, the temporal correlation coefficient between the Scheme-I-predicted and observed EAWMI was 0.47, exceeding the 99% significance level, with the root-mean-square error (RMSE) decreased by 12%. The autumn Arctic sea ice and North Pacific sea surface temperature (SST) are two important external forcing factors for the interannual variability of the EAWM. Therefore, a second (hybrid) prediction scheme, Scheme-II, was also developed. This scheme not only involved the EAWMI DY of CFSv2, but also the sea-ice concentration (SIC) observed the previous autumn in the Laptev and East Siberian seas and the temporal coefficients of the third mode of the North Pacific SST in DY form. We found that a negative SIC anomaly in the preceding autumn over the Laptev and the East Siberian seas could lead to a significant enhancement of the Aleutian low and East Asian westerly jet in the following winter. However, the intensity of the winter Siberian high was mainly affected by the third mode of the North Pacific autumn SST. Scheme-I and Scheme-II also showed higher predictive ability for the EAWMI in negative anomaly years compared to CFSv2. More importantly, the improvement in the prediction skill of the EAWMI by the new schemes, especially for Scheme-II, could enhance the forecasting skill of the winter 2-m air temperature (T-2m) in most parts of China, as well as the intensity of the Aleutian low and Siberian high in winter. The new schemes provide a theoretical basis for improving the prediction of winter climate in China.

Day length unlikely to constrain climate-driven shifts in leaf-out times of northern woody plants

NASA Astrophysics Data System (ADS)

Zohner, Constantin M.; Benito, Blas M.; Svenning, Jens-Christian; Renner, Susanne S.

2016-12-01

The relative roles of temperature and day length in driving spring leaf unfolding are known for few species, limiting our ability to predict phenology under climate warming. Using experimental data, we assess the importance of photoperiod as a leaf-out regulator in 173 woody species from throughout the Northern Hemisphere, and we also infer the influence of winter duration, temperature seasonality, and inter-annual temperature variability. We combine results from climate- and light-controlled chambers with species’ native climate niches inferred from georeferenced occurrences and range maps. Of the 173 species, only 35% relied on spring photoperiod as a leaf-out signal. Contrary to previous suggestions, these species come from lower latitudes, whereas species from high latitudes with long winters leafed out independent of photoperiod. The strong effect of species’ geographic-climatic history on phenological strategies complicates the prediction of community-wide phenological change.

Using Empirical Orthogonal Teleconnections to Analyze Interannual Precipitation Variability in China

NASA Astrophysics Data System (ADS)

Stephan, C.; Klingaman, N. P.; Vidale, P. L.; Turner, A. G.; Demory, M. E.; Guo, L.

2017-12-01

Interannual rainfall variability in China affects agriculture, infrastructure and water resource management. A consistent and objective method, Empirical Orthogonal Teleconnection (EOT) analysis, is applied to precipitation observations over China in all seasons. Instead of maximizing the explained space-time variance, the method identifies regions in China that best explain the temporal variability in domain-averaged rainfall. It produces known teleconnections, that include high positive correlations with ENSO in eastern China in winter, along the Yangtze River in summer, and in southeast China during spring. New findings include that variability along the southeast coast in winter, in the Yangtze valley in spring, and in eastern China in autumn, are associated with extratropical Rossby wave trains. The same analysis is applied to six climate simulations of the Met Office Unified Model with and without air-sea coupling and at various horizontal resolutions of 40, 90 and 200 km. All simulations reproduce the observed patterns of interannual rainfall variability in winter, spring and autumn; the leading pattern in summer is present in all but one simulation. However, only in two simulations are all patterns associated with the observed physical mechanism. Coupled simulations capture more observed patterns of variability and associate more of them with the correct physical mechanism, compared to atmosphere-only simulations at the same resolution. Finer resolution does not improve the fidelity of these patterns or their associated mechanisms. Evaluating climate models by only geographical distribution of mean precipitation and its interannual variance is insufficient; attention must be paid to associated mechanisms.

Climate variability in Andalusia (southern Spain) during the period 1701-1850 based on documentary sources: evaluation and comparison with climate model simulations

NASA Astrophysics Data System (ADS)

Rodrigo, F. S.; Gómez-Navarro, J. J.; Montávez Gómez, J. P.

2012-01-01

In this work, a reconstruction of climatic conditions in Andalusia (southern Iberian Peninsula) during the period 1701-1850, as well as an evaluation of its associated uncertainties, is presented. This period is interesting because it is characterized by a minimum in solar irradiance (Dalton Minimum, around 1800), as well as intense volcanic activity (for instance, the eruption of Tambora in 1815), at a time when any increase in atmospheric CO2 concentrations was of minor importance. The reconstruction is based on the analysis of a wide variety of documentary data. The reconstruction methodology is based on counting the number of extreme events in the past, and inferring mean value and standard deviation using the assumption of normal distribution for the seasonal means of climate variables. This reconstruction methodology is tested within the pseudoreality of a high-resolution paleoclimate simulation performed with the regional climate model MM5 coupled to the global model ECHO-G. The results show that the reconstructions are influenced by the reference period chosen and the threshold values used to define extreme values. This creates uncertainties which are assessed within the context of climate simulation. An ensemble of reconstructions was obtained using two different reference periods (1885-1915 and 1960-1990) and two pairs of percentiles as threshold values (10-90 and 25-75). The results correspond to winter temperature, and winter, spring and autumn rainfall, and they are compared with simulations of the climate model for the considered period. The mean value of winter temperature for the period 1781-1850 was 10.6 ± 0.1 °C (11.0 °C for the reference period 1960-1990). The mean value of winter rainfall for the period 1701-1850 was 267 ± 18 mm (224 mm for 1960-1990). The mean values of spring and autumn rainfall were 164 ± 11 and 194 ± 16 mm (129 and 162 mm for 1960-1990, respectively). Comparison of the distribution functions corresponding to 1790-1820 and 1960-1990 indicates that during the Dalton Minimum the frequency of dry and warm (wet and cold) winters was lower (higher) than during the reference period: temperatures were up to 0.5 °C lower than the 1960-1990 value, and rainfall was 4% higher.

Climate model assessment of changes in winter-spring streamflow timing over North America

USGS Publications Warehouse

Kam, Jonghun; Knutson, Thomas R.; Milly, Paul C. D.

2018-01-01

Over regions where snow-melt runoff substantially contributes to winter-spring streamflows, warming can accelerate snow melt and reduce dry-season streamflows. However, conclusive detection of changes and attribution to anthropogenic forcing is hindered by brevity of observational records, model uncertainty, and uncertainty concerning internal variability. In this study, a detection/attribution of changes in mid-latitude North American winter-spring streamflow timing is examined using nine global climate models under multiple forcing scenarios. In this study, robustness across models, start/end dates for trends, and assumptions about internal variability is evaluated. Marginal evidence for an emerging detectable anthropogenic influence (according to four or five of nine models) is found in the north-central U.S., where winter-spring streamflows have been coming earlier. Weaker indications of detectable anthropogenic influence (three of nine models) are found in the mountainous western U.S./southwestern Canada and in extreme northeastern U.S./Canadian Maritimes. In the former region, a recent shift toward later streamflows has rendered the full-record trend toward earlier streamflows only marginally significant, with possible implications for previously published climate change detection findings for streamflow timing in this region. In the latter region, no forced model shows as large a shift toward earlier streamflow timing as the detectable observed shift. In other (including warm, snow-free) regions, observed trends are typically not detectable, although in the U.S. central plains we find detectable delays in streamflow, which are inconsistent with forced model experiments.

East Asia winter climate changes under RCP scenarios in terms of East Asian winter monsoon indices

NASA Astrophysics Data System (ADS)

Ahn, J. B.; Hong, J. Y.

2016-12-01

The changes in the winter climatology and variability of the East Asian winter monsoon (EAWM) for the late 21st century (2070-2099) under the Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios are projected in terms of EAWM indices (EAWMIs). Firstly, the capability of the climate models participating in the Coupled Model Intercomparison Project phase 5 (CMIP5) in simulating the boreal winter climatology and the interannual variability of the EAWM for the late 20th century (1971-2000) is examined. Nine of twenty-three climate models are selected based on the pattern correlations with observation and a multi-model ensemble is applied to the nine model data. Three of twelve EAWMIs that show the most significant temporal correlations between the observation and CMIP5 surface air temperatures are utilized. The ensemble CMIP5 is capable of reproducing the overall features of the EAWM in spite of some biases in the region. The negative correlations between the EAWMIs and boreal winter temperature are well reproduced and 3-5 years of the major interannual variation observed in this region are also well simulated according to power spectral analyses of the simulated indices. The regressed fields of sea level pressure, surface air temperature, 500-hPa geopotential height, and 300-hPa zonal wind are well established with pattern correlations above 0.83 between CMIP5 and observation data. The differences between RCPs and Historical indicate strong warming, which increases with latitude, ranging from 1°C to 5°C under RCP4.5 and from 3°C to 7°C under RCP8.5 in the East Asian region. The anomalous southerly winds generally become stronger, implying weaker EAWMs in both scenarios. These features are also identified with fields regressed onto the indices in RCPs. The future projections reveal that the interannual variability of the indices will be maintained with intensity similar to that of the present. AcknowledgmentsThis work was carried out with the support of "Cooperative Research Program for Agriculture Science & Technology Development (Project No. PJ012293)" Rural Development Administration, Republic of Korea.

Norwegian fjord sediments reveal NAO related winter temperature and precipitation changes of the past 2800 years

NASA Astrophysics Data System (ADS)

Faust, Johan; Fabian, Karl; Giraudeau, Jacques; Knies, Jochen

2016-04-01

The North Atlantic Oscillation (NAO) is the leading mode of atmospheric circulation variability in the North Atlantic region. Associated shifts of storm tracks, precipitation and temperature patterns affect energy supply and demand, fisheries and agricultural, as well as marine and terrestrial ecological dynamics. Long-term NAO reconstructions are crucial to better understand NAO variability in its response to climate forcing factors, and assess predictability and possible shifts associated with ongoing climate change. Fjord deposits have a great potential for providing high-resolution sedimentary records that reflect local terrestrial and marine processes and, therefore, offer unique opportunities for the investigation of sedimentological and geochemical climatically induced processes. A recent study of instrumental time series revealed NAO as main factor for a strong relation between winter temperature, precipitation and river discharge in central Norway over the past 50 years. Here we use the gained knowledge to establish the first high resolution NAO proxy record from marine sediments. By comparing geochemical measurements from a short sediment core with instrumental data we show that marine primary productivity proxies are sensitive to NAO changes. Conditioned on a stationary relation between our climate proxy and the NAO we establish the first high resolution NAO proxy record (NAO-TFJ) from marine sediments covering the past 2,800 years. The NAO-TFJ shows distinct co-variability with climate changes over Greenland, solar activity and Northern Hemisphere glacier dynamics as well as climatically associated paleo-demographic trends.

The role of climatic variables in winter cereal yields: a retrospective analysis.

PubMed

Luo, Qunying; Wen, Li

2015-02-01

This study examined the effects of observed climate including [CO2] on winter cereal [winter wheat (Triticum aestivum), barley (Hordeum vulgare) and oat (Avena sativa)] yields by adopting robust statistical analysis/modelling approaches (i.e. autoregressive fractionally integrated moving average, generalised addition model) based on long time series of historical climate data and cereal yield data at three locations (Moree, Dubbo and Wagga Wagga) in New South Wales, Australia. Research results show that (1) growing season rainfall was significantly, positively and non-linearly correlated with crop yield at all locations considered; (2) [CO2] was significantly, positively and non-linearly correlated with crop yields in all cases except wheat and barley yields at Wagga Wagga; (3) growing season maximum temperature was significantly, negatively and non-linearly correlated with crop yields at Dubbo and Moree (except for barley); and (4) radiation was only significantly correlated with oat yield at Wagga Wagga. This information will help to identify appropriate management adaptation options in dealing with the risk and in taking the opportunities of climate change.

Seasonality of Groundwater Recharge in the Basin and Range Province, Western North America

NASA Astrophysics Data System (ADS)

Neff, K. L.; Meixner, T.; Ajami, H.; De La Cruz, L.

2015-12-01

For water-scarce communities in the western U.S., it is critical to understand groundwater recharge regimes and how those regimes might shift in the face of climate change and impact groundwater resources. Watersheds in the Basin and Range Geological Province are characterized by a variable precipitation regime of wet winters and variable summer precipitation. The relative contributions to groundwater recharge by summer and winter precipitation vary throughout the province, with winter precipitation recharge dominant in the northern parts of the region, and recharge from summer monsoonal precipitation playing a more significant role in the south, where the North American Monsoon (NAM) extends its influence. Stable water isotope data of groundwater and seasonal precipitation from sites in Sonora, Mexico and the U.S. states of California, Nevada, Utah, Arizona, Colorado, New Mexico, and Texas were examined to estimate and compare groundwater recharge seasonality throughout the region. Contributions of winter precipitation to annual recharge vary from 69% ± 41% in the southernmost Río San Miguel Basin in Sonora, Mexico, to 100% ± 36% in the westernmost Mojave Desert of California. The Normalized Seasonal Wetness Index (NSWI), a simple water budget method for estimating recharge seasonality from climatic data, was shown to approximate recharge seasonality well in several winter precipitation-dominated systems, but less well in basins with significant summer precipitation.

March-June temperature reconstruction in the Czech Lands based on cereal harvest dates in the 1501-2008 period

NASA Astrophysics Data System (ADS)

Brázdil, Rudolf; Možný, Martin; Dobrovolný, Petr; Trnka, Mirek

2010-05-01

Cereal crop harvests reflect the weather patterns of the period immediately preceding them, and thus the dates at which they begin may be used as a source of proxy data on regional climate. Using systematic phenological observations in the Czech Lands (now known as the Czech Republic) after 1848, together with exploration of further surviving documentary evidence (chronicles, diaries, financial accounts etc.), it has proved possible to create series of winter wheat harvest dates for the period 1501-2008. Employing linear regression, the harvesting dates of the main cereal species (wheat, rye, barley, oats) were first converted to winter wheat harvest days and then normalised to the same altitude above sea level. The next step consisted of using series of winter wheat harvest dates to reconstruct mean March-June temperatures in the Czech Lands, applying standard palaeoclimatological methods. Series reconstructed by linear regression explain 70% of temperature variability. A profound cold period corresponding with late winter wheat harvests was noted between 1659 and 1705. In contrast, warm periods (i.e. early winter wheat harvests) were found for the periods of 1517-1542, 1788-1834 and 1946-2008. The period after 1951 is the warmest of all throughout the entire 1501-2008 period. Comparisons with other European temperature reconstructions derived from documentary sources (including grape harvest dates), tree-ring and instrumental data reveal generally close agreement, with significant correlations. Lower correlations around A.D. 1650 and 1750 may be partly related to deterioration of socio-economic conditions in the Czech Lands resulting from prolonged wars. The results obtained demonstrate that it is possible to use widely-available cereal harvest data for climate analysis and also that such data constitute an independent proxy data series for the region of Central Europe crucial to further studies of the potential impact of climatic variability and climate change on agriculture. (The paper was supported by Grant Agency of the Czech Republic, project No. 521/08/1682.)

Prospects for seasonal forecasting of summer drought and low river flow anomalies in England and Wales

NASA Astrophysics Data System (ADS)

Wedgbrow, C. S.; Wilby, R. L.; Fox, H. R.; O'Hare, G.

2002-02-01

Future climate change scenarios suggest enhanced temporal and spatial gradients in water resources across the UK. Provision of seasonal forecast statistics for surface climate variables could alleviate some negative effects of climate change on water resource infrastructure. This paper presents a preliminary investigation of spatial and temporal relationships between large-scale North Atlantic climatic indices, drought severity and river flow anomalies in England and Wales. Potentially useful predictive relationships are explored between winter indices of the Polar-Eurasian (POL) teleconnection pattern, the North Atlantic oscillation (NAO), North Atlantic sea surface temperature anomalies (SSTAs), and the summer Palmer drought severity index (PDSI) and reconstructed river flows in England and Wales. Correlation analyses, coherence testing and an index of forecast potential, demonstrate that preceding winter values of the POL index, SSTA (and to a lesser extent the NAO), provide indications of summer and early autumn drought severity and river flow anomalies in parts of northwest, southwest and southeast England. Correlation analyses demonstrate that positive winter anomalies of T1, POL index and NAO index are associated with negative PDSI (i.e. drought) across eastern parts of the British Isles in summer (r < 0.51). Coherence tests show that a positive winter SSTA (1871-1995) and POL index (1950-95) have preceded below-average summer river flows in the northwest and southwest of England and Wales in 70 to 100% of summers. The same rivers have also experienced below-average flows during autumn following negative winter phases of the NAO index in 64 to 93% of summers (1865-1995). Possible explanations for the predictor-predictand relationships are considered, including the memory of groundwater, and ocean-atmosphere coupling, and regional manifestations of synoptic rainfall processes. However, further research is necessary to increase the number of years and predictor variables from which it is possible to derive rules that may be useful for forecasting.

How Will Climate Warming Affect Non-Native Pumpkinseed Lepomis gibbosus Populations in the U.K.?

PubMed

Zięba, Grzegorz; Fox, Michael G; Copp, Gordon H

2015-01-01

Of the non-native fishes introduced to the U.K., the pumpkinseed is one of six species predicted to benefit from the forecasted climate warming conditions. To demonstrate the potential response of adults and their progeny to a water temperature increase, investigations of parental pumpkinseed acclimatization, reproduction and YOY over-wintering were carried out in outdoor experimental ponds under ambient and elevated water temperature regimes. No temperature effects were observed on either adult survivorship and growth, and none of the assessed reproductive activity variables (total spawning time, spawning season length, number of spawning bouts) appeared to be responsible for the large differences observed in progeny number and biomass. However, it was demonstrated in a previous study [Zięba G. et al., 2010] that adults in the heated ponds began spawning earlier than those of the ambient ponds. Ambient ponds produced 2.8× more progeny than the heated ponds, but these progeny were significantly smaller, probably due to their late hatching date, and subsequently suffered very high mortality over the first winter. Pumpkinseed in the U.K. will clearly benefit from climate warming through earlier seasonal reproduction, resulting in larger progeny going into winter, and as a result, higher over-winter survivorship would be expected relative to that which occurs under the present climatic regime.

The East Asian Jet Stream and Asian-Pacific Climate

NASA Technical Reports Server (NTRS)

Yang, Song; Lau, K.-M.; Kim, K.-M.

1999-01-01

In this study, the NASA GEOS and NCEP/NCAR reanalyses and GPCP rainfall data have been used to study the variability of the East Asian westerly jet stream and its impact on the Asian-Pacific climate, with a focus on interannual time scales. Results indicate that external forcings such as sea surface temperature (SST) and land surface processes also play an important role in the variability of the jet although this variability is strongly governed by internal dynamics. There is a close link between the jet and Asian-Pacific climate including the Asian winter monsoon and tropical convection. The atmospheric teleconnection pattern associated with the jet is different from the ENSO-related pattern. The influence of the jet on eastern Pacific and North American climate is also discussed.

Long-term observations of CO2 exchange over agricultural crops in two regional climates of Southwest Germany

NASA Astrophysics Data System (ADS)

Poyda, Arne; Wizemann, Hans-Dieter; Ingwersen, Joachim; Wulfmeyer, Volker; Streck, Thilo

2017-04-01

The impact of agricultural land use on soil organic carbon (SOC) dynamics has been widely studied in the past few decades, particularly in context of the SOC forcing or mitigation potential of global climate change. Grassland utilization can increase or maintain SOC stocks. Arable cropping tends to decrease SOC stocks, at least for some time after land use change (SMITH, 2008). In the long run, it can be assumed that SOC reaches a steady state where the production of roots and aboveground crop residues and possibly organic fertilization level out soil respiration. To study the effects of crop type, year and regional site conditions on CO2 exchange and C budgets of arable cropping systems in Southwest Germany, eddy covariance measurements were conducted on a total of six sites in the two climatically contrasting regions of Kraichgau and Swabian Alb since 2009. Main crops were winter wheat, silage maize and winter rapeseed but also winter barley, summer barley and spelt were cultivated on the Swabian Alb sites. Cover crops were grown between winter and summer crops on all sites. Net ecosystem exchange (NEE) data were gap-filled following REICHSTEIN et al. (2005) and partitioned into ecosystem respiration (RECO) and gross primary production (GPP) using seasonally differing temperature response functions of nighttime NEE. Furthermore, different approaches for filling long data gaps of several months in winter were evaluated. Considering C inputs by organic fertilizers and C removals by harvest, C budgets were calculated per site and year. First results indicate that the variability of NEE fluxes between different crops is much higher compared to the variability between different years of a certain crop. However, regional differences in soil and weather conditions significantly influence plant growth dynamics and thus CO2 exchange.

Climate change impacts on northwestern and intermountain United States rangelands

Treesearch

Jeanne C. Chambers; Mike Pellant

2008-01-01

Our focus is on the Pacific Northwest and Intermountain Region including the Great Basin, Columbia Plateau, Colorado Plateau, and surrounding areas. The climate of this large, arid to semiarid region is defined by generally low and highly variable precipitation. Much of the yearly precipitation arrives as winter snow because most of the moisture comes as frontal storms...

Impacts of temperature and its variability on mortality in New England

NASA Astrophysics Data System (ADS)

Shi, Liuhua; Kloog, Itai; Zanobetti, Antonella; Liu, Pengfei; Schwartz, Joel D.

2015-11-01

Rapid build-up of greenhouse gases is expected to increase Earth’s mean surface temperature, with unclear effects on temperature variability. This makes understanding the direct effects of a changing climate on human health more urgent. However, the effects of prolonged exposures to variable temperatures, which are important for understanding the public health burden, are unclear. Here we demonstrate that long-term survival was significantly associated with both seasonal mean values and standard deviations of temperature among the Medicare population (aged 65+) in New England, and break that down into long-term contrasts between ZIP codes and annual anomalies. A rise in summer mean temperature of 1 °C was associated with a 1.0% higher death rate, whereas an increase in winter mean temperature corresponded to a 0.6% decrease in mortality. Increases in standard deviations of temperature for both summer and winter were harmful. The increased mortality in warmer summers was entirely due to anomalies, whereas it was long-term average differences in the standard deviation of summer temperatures across ZIP codes that drove the increased risk. For future climate scenarios, seasonal mean temperatures may in part account for the public health burden, but the excess public health risk of climate change may also stem from changes of within-season temperature variability.

Analysis of monthly, winter, and annual temperatures in Zagreb, Croatia, from 1864 to 2010: the 7.7-year cycle and the North Atlantic Oscillation

NASA Astrophysics Data System (ADS)

Sen, Asok K.; Ogrin, Darko

2016-02-01

Long instrumental records of meteorological variables such as temperature and precipitation are very useful for studying regional climate in the past, present, and future. They can also be useful for understanding the influence of large-scale atmospheric circulation processes on the regional climate. This paper investigates the monthly, winter, and annual temperature time series obtained from the instrumental records in Zagreb, Croatia, for the period 1864-2010. Using wavelet analysis, the dominant modes of variability in these temperature series are identified, and the time intervals over which these modes may persist are delineated. The results reveal that all three temperature records exhibit low-frequency variability with a dominant periodicity at around 7.7 years. The 7.7-year cycle has also been observed in the temperature data recorded at several other stations in Europe, especially in Northern and Western Europe, and may be linked to the North Atlantic Oscillation (NAO) and/or solar/geomagnetic activity.

Climate Change Impact Assessment in Pacific North West Using Copula based Coupling of Temperature and Precipitation variables

NASA Astrophysics Data System (ADS)

Qin, Y.; Rana, A.; Moradkhani, H.

2014-12-01

The multi downscaled-scenario products allow us to better assess the uncertainty of the changes/variations of precipitation and temperature in the current and future periods. Joint Probability distribution functions (PDFs), of both the climatic variables, might help better understand the interdependence of the two, and thus in-turn help in accessing the future with confidence. Using the joint distribution of temperature and precipitation is also of significant importance in hydrological applications and climate change studies. In the present study, we have used multi-modelled statistically downscaled-scenario ensemble of precipitation and temperature variables using 2 different statistically downscaled climate dataset. The datasets used are, 10 Global Climate Models (GCMs) downscaled products from CMIP5 daily dataset, namely, those from the Bias Correction and Spatial Downscaling (BCSD) technique generated at Portland State University and from the Multivariate Adaptive Constructed Analogs (MACA) technique, generated at University of Idaho, leading to 2 ensemble time series from 20 GCM products. Thereafter the ensemble PDFs of both precipitation and temperature is evaluated for summer, winter, and yearly periods for all the 10 sub-basins across Columbia River Basin (CRB). Eventually, Copula is applied to establish the joint distribution of two variables enabling users to model the joint behavior of the variables with any level of correlation and dependency. Moreover, the probabilistic distribution helps remove the limitations on marginal distributions of variables in question. The joint distribution is then used to estimate the change trends of the joint precipitation and temperature in the current and future, along with estimation of the probabilities of the given change. Results have indicated towards varied change trends of the joint distribution of, summer, winter, and yearly time scale, respectively in all 10 sub-basins. Probabilities of changes, as estimated by the joint precipitation and temperature, will provide useful information/insights for hydrological and climate change predictions.

Variability of the atmospheric energy flux across 70°N computed from the GFDL data set

NASA Astrophysics Data System (ADS)

Overland, James E.; Turet, Philip

The primary energy balance for the arctic atmosphere is through northward advection of moist static energy—sensible heat, potential energy, and latent heat—balanced by long wave radiation to space. Energy flux from sea ice and marginal seas contributes perhaps 20-30% of the outgoing radiation north of 70°N in winter and absorbs a nearly equal amount during summer. Thorndike's toy model shows that extreme climate states with no ice growth or melt can occur by changing the latitudinal energy flux by ±20-30% out of an annual mean flux of 100 W m-2. We extend the previous work on latitudinal energy flux by Nakamura and Oort (NO) to a 25-year record and investigate temporal variability. Our annual latitudinal energy flux was 103 W m-2 compared to the NO value of 98 W m-2 this difference was from greater fluxes during the winter. We found that mean winter (NDJFM) energy flux was 121 W m-2 with a standard deviation of 11 W m-2. There were no large outliers in any year. An analysis of variance showed that interannual variability does not contribute towards explaining monthly variability of northward energy transport for the winter, summer or annual periods. Transient eddy flux of sensible heat into the arctic basin was the largest component of the total energy flux and is concentrated near the longitudes of the Greenland Sea (˜10°W) and the Bering and Chukchi Seas (180°). There is a minimum in atmospheric heating north of Greenland, a known region of thick ice. While there was little interannual variability of energy flux across 70°N, there was considerable month-to-month variability and regional variability in poleward energy flux. Sea ice may playa role in storage and redistribution of energy in the arctic climate.

A new climate index controlling winter wave activity along the Atlantic coast of Europe: The West Europe Pressure Anomaly

NASA Astrophysics Data System (ADS)

Castelle, Bruno; Dodet, Guillaume; Masselink, Gerd; Scott, Tim

2017-02-01

A pioneering and replicable method based on a 66-year numerical weather and wave hindcast is developed to optimize a climate index based on the sea level pressure (SLP) that best explains winter wave height variability along the coast of western Europe, from Portugal to UK (36-52°N). The resulting so-called Western Europe Pressure Anomaly (WEPA) is based on the sea level pressure gradient between the stations Valentia (Ireland) and Santa Cruz de Tenerife (Canary Islands). The WEPA positive phase reflects an intensified and southward shifted SLP difference between the Icelandic low and the Azores high, driving severe storms that funnel high-energy waves toward western Europe southward of 52°N. WEPA outscores by 25-150% the other leading atmospheric modes in explaining winter-averaged significant wave height, and even by a largest amount the winter-averaged extreme wave heights. WEPA is also the only index capturing the 2013/2014 extreme winter that caused widespread coastal erosion and flooding in western Europe.

Use of a scenario-neutral approach to identify the key hydro-meteorological attributes that impact runoff from a natural catchment

NASA Astrophysics Data System (ADS)

Guo, Danlu; Westra, Seth; Maier, Holger R.

2017-11-01

Scenario-neutral approaches are being used increasingly for assessing the potential impact of climate change on water resource systems, as these approaches allow the performance of these systems to be evaluated independently of climate change projections. However, practical implementations of these approaches are still scarce, with a key limitation being the difficulty of generating a range of plausible future time series of hydro-meteorological data. In this study we apply a recently developed inverse stochastic generation approach to support the scenario-neutral analysis, and thus identify the key hydro-meteorological variables to which the system is most sensitive. The stochastic generator simulates synthetic hydro-meteorological time series that represent plausible future changes in (1) the average, extremes and seasonal patterns of rainfall; and (2) the average values of temperature (Ta), relative humidity (RH) and wind speed (uz) as variables that drive PET. These hydro-meteorological time series are then fed through a conceptual rainfall-runoff model to simulate the potential changes in runoff as a function of changes in the hydro-meteorological variables, and runoff sensitivity is assessed with both correlation and Sobol' sensitivity analyses. The method was applied to a case study catchment in South Australia, and the results showed that the most important hydro-meteorological attributes for runoff were winter rainfall followed by the annual average rainfall, while the PET-related meteorological variables had comparatively little impact. The high importance of winter rainfall can be related to the winter-dominated nature of both the rainfall and runoff regimes in this catchment. The approach illustrated in this study can greatly enhance our understanding of the key hydro-meteorological attributes and processes that are likely to drive catchment runoff under a changing climate, thus enabling the design of tailored climate impact assessments to specific water resource systems.

Ecological controls on water-cycle response to climate variability in deserts.

PubMed

Scanlon, B R; Levitt, D G; Reedy, R C; Keese, K E; Sully, M J

2005-04-26

The impact of climate variability on the water cycle in desert ecosystems is controlled by biospheric feedback at interannual to millennial timescales. This paper describes a unique field dataset from weighing lysimeters beneath nonvegetated and vegetated systems that unequivocally demonstrates the role of vegetation dynamics in controlling water cycle response to interannual climate variability related to El Nino southern oscillation in the Mojave Desert. Extreme El Nino winter precipitation (2.3-2.5 times normal) typical of the U.S. Southwest would be expected to increase groundwater recharge, which is critical for water resources in semiarid and arid regions. However, lysimeter data indicate that rapid increases in vegetation productivity in response to elevated winter precipitation reduced soil water storage to half of that in a nonvegetated lysimeter, thereby precluding deep drainage below the root zone that would otherwise result in groundwater recharge. Vegetation dynamics have been controlling the water cycle in interdrainage desert areas throughout the U.S. Southwest, maintaining dry soil conditions and upward soil water flow since the last glacial period (10,000-15,000 yr ago), as shown by soil water chloride accumulations. Although measurements are specific to the U.S. Southwest, correlations between satellite-based vegetation productivity and elevated precipitation related to El Nino southern oscillation indicate this model may be applicable to desert basins globally. Understanding the two-way coupling between vegetation dynamics and the water cycle is critical for predicting how climate variability influences hydrology and water resources in water-limited landscapes.

[Winter wheat yield gap between field blocks based on comparative performance analysis].

PubMed

Chen, Jian; Wang, Zhong-Yi; Li, Liang-Tao; Zhang, Ke-Feng; Yu, Zhen-Rong

2008-09-01

Based on a two-year household survey data, the yield gap of winter wheat in Quzhou County of Hebei Province, China in 2003-2004 was studied through comparative performance analysis (CPA). The results showed that there was a greater yield gap (from 4.2 to 7.9 t x hm(-2)) between field blocks, with a variation coefficient of 0.14. Through stepwise forward linear multiple regression, it was found that the yield model with 8 selected variables could explain 63% variability of winter wheat yield. Among the variables selected, soil salinity, soil fertility, and irrigation water quality were the most important limiting factors, accounting for 52% of the total yield gap. Crop variety was another important limiting factor, accounting for 14%; while planting date, fertilizer type, disease and pest, and water press accounted for 7%, 14%, 10%, and 3%, respectively. Therefore, besides soil and climate conditions, management practices occupied the majority of yield variability in Quzhou County, suggesting that the yield gap could be reduced significantly through optimum field management.

Tolerance to multiple climate stressors: A case study of Douglas-fir drought and cold hardiness

USGS Publications Warehouse

Bansal, Sheel; Harrington, Constance A; St. Clair, John Bradley

2016-01-01

Summary: 1. Drought and freeze events are two of the most common forms of climate extremes which result in tree damage or death, and the frequency and intensity of both stressors may increase with climate change. Few studies have examined natural covariation in stress tolerance traits to cope with multiple stressors among wild plant populations. 2. We assessed the capacity of coastal Douglas-fir (Pseudotsuga menziesii var. menziesii), an ecologically and economically important species in the northwestern USA, to tolerate both drought and cold stress on 35 populations grown in common gardens. We used principal components analysis to combine drought and cold hardiness trait data into generalized stress hardiness traits to model geographic variation in hardiness as a function of climate across the Douglas-fir range. 3. Drought and cold hardiness converged among populations along winter temperature gradients and diverged along summer precipitation gradients. Populations originating in regions with cold winters had relatively high tolerance to both drought and cold stress, which is likely due to overlapping adaptations for coping with winter desiccation. Populations from regions with dry summers had increased drought hardiness but reduced cold hardiness, suggesting a trade-off in tolerance mechanisms. 4. Our findings highlight the necessity to look beyond bivariate trait–climate relationships and instead consider multiple traits and climate variables to effectively model and manage for the impacts of climate change on widespread species.

Response of ice cover on shallow Arctic lakes to contemporary climate conditions: Numerical modeling and remote sensing data analysis

NASA Astrophysics Data System (ADS)

Duguay, C.; Surdu, C.; Brown, L.; Samuelsson, P.

2012-04-01

Lake ice cover has been shown to be a robust indicator of climate variability and change. Recent studies have demonstrated that break-up dates, in particular, have been occurring earlier in many parts of the Northern Hemisphere over the last 50 years in response to warmer climatic conditions in the winter and spring seasons. The impacts of trends in air temperature and winter precipitation over the last five decades and those projected by global climate models will affect the timing and duration of ice cover (and ice thickness) on Arctic lakes. This will likely, in turn, have an important feedback effect on energy, water, and biogeochemical cycling in various regions of the Arctic. In the case of shallow tundra lakes, many of which are less than 3-m deep, warmer climate conditions could result in a smaller fraction of lakes that freeze to their bed in winter since thinner ice covers are expected to develop. Shallow lakes of the coastal plain of northern Alaska, and other similar regions of the Arctic, have likely been experiencing changes in seasonal ice thickness (and phenology) over the last few decades but these have not yet been documented. This paper presents results from a numerical lake ice modeling experiment and the analysis of ERS-1/2 synthetic aperture radar (SAR) data to elucidate the response of ice cover (thickness, freezing to bed, and phenology) on shallow lakes of the North Slope of Alaska (NSA)to climate conditions over the last three decades. New downscaled data specific for the Arctic domain (at a resolution of 0.44 degrees using ERA Interim Reanalysis as boundary condition) produced by the Rossby Centre regional atmospheric model (RCA4) was used to force the Canadian Lake Ice Model (CLIMo) for the period 1979-2010. Output from CLIMo included freeze-up and break-up dates as well as ice thickness on a daily basis. ERS-1/2 data was used to map areas of shallow lakes that freeze to bed and when this happens (timing) in winter for the period 1991-2010. Preliminary results from a sub-region of the NSA show that the interannual variability in ice thickness simulated with CLIMo match well that of the fraction of lakes that freeze to their bed in winter as determined from the analysis of SAR data.

Satellite-based Monotoring of mitiple natural disasters in Mongolian socio-ecological system

NASA Astrophysics Data System (ADS)

Kang, Sinkyu

2016-04-01

In this presentation, a conceptual mechanisms how multiple natural hazards (i.e. drought, dust storm, land degradation, and Dzud) in Mongolia are linked with each other and how satellite earth observation (EO) data can be utilized to analyze cause-and results relations and to predict the natural hazards. Massive loss of livestock and wildlife animal during winter seasons (dzud) is an endemic climatic disaster in the Central Asia grasslands but the mechanisms are not well understood yet. Recent national-wide sever Dzud occurred during 2009-2010 winter in Mongolia. Whereas, high stocking rate of livestock may give negative effects on sustainable use of pastureland. Dzud is a natural mechanism reducing grazing pressure when stocking rate is high enough to cause the negative effect. Both Dzud and land degradation were directly linked with drought phenomena, which is associated with dust storm occurrence because those conditions can cause sparse vegetation and increase of sensible heat generating strong vertical wind. At a lower level of administration (i.e., soum), stepwise multiple regression analysis was conducted to find significant factors of inter-annual livestock change. For a period from 2003 to 2010, various datasets were prepared from national census and satellite data (summer and winter temperature and precipitation, and summer dryness and vegetation index, NDVI). As results, linear regression models were successfully produced at 70% of soums studied. Summer and winter variables appeared equally important in controlling livestock dynamics. Single-factor models were predominant. The primary factor of each soum showed certain regional patterns incident well with climate severity and foraging resource availability (e.g. temperature in north, dryness in south, and NDVI in middle). Our results indicate that Mongolian pastoral livelihood is highly vulnerable to extreme variability of endemic regional climate factors and hence, there are still rooms for enhancing socio-ecological adaptive capacity such as herder's preparedness and governance. We illustrate the seasonal climate-vegetation-livestock interactions with a simplified schematic mechanism model. Our schematic model refined it to give better process-oriented relationships among key variables. Seasonal temperature and precipitation are the primary forcing variables to determine vegetation growth and livestock accessibility to food resources and dryness. Summer standing biomass and winter dry biomass (i.e. residue) were separated and associated with seasonal livestock foraging, respectively. By its mechanistic nature, the schematic model can be applied to test statistical significance of factors associated with annual livestock change or to provide logical grounds on developing a dynamic numerical model in future.

Hydroclimatic variability in the Lake Mondsee region and its relationships with large-scale climate anomaly patterns

NASA Astrophysics Data System (ADS)

Rimbu, Norel; Ionita, Monica; Swierczynski, Tina; Brauer, Achim; Kämpf, Lucas; Czymzik, Markus

2017-04-01

Flood triggered detrital layers in varved sediments of Lake Mondsee, located at the northern fringe of the European Alps (47°48'N,13°23'E), provide an important archive of regional hydroclimatic variability during the mid- to late Holocene. To improve the interpretation of the flood layer record in terms of large-scale climate variability, we investigate the relationships between observational hydrological records from the region, like the Mondsee lake level, the runoff of the lake's main inflow Griesler Ache, with observed precipitation and global climate patterns. The lake level shows a strong positive linear trend during the observational period in all seasons. Additionally, lake level presents important interannual to multidecadal variations. These variations are associated with distinct seasonal atmospheric circulation patterns. A pronounced anomalous anticyclonic center over the Iberian Peninsula is associated with high lake levels values during winter. This center moves southwestward during spring, summer and autumn. In the same time, a cyclonic anomaly center is recorded over central and western Europe. This anomalous circulation extends southwestward from winter to autumn. Similar atmospheric circulation patterns are associated with river runoff and precipitation variability from the region. High lake levels are associated with positive local precipitation anomalies in all seasons as well as with negative local temperature anomalies during spring, summer and autumn. A correlation analysis reveals that lake level, runoff and precipitation variability is related to large-scale sea surface temperature anomaly patterns in all seasons suggesting a possible impact of large-scale climatic modes, like the North Atlantic Oscillation and Atlantic Multidecadal Oscillation on hydroclimatic variability in the Lake Mondsee region. The results presented in this study can be used for a more robust interpretation of the long flood layer record from Lake Mondsee sediments in terms of regional and large-scale climate variability during the past.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chavas, Daniel R.; Izaurralde, Roberto C.; Thomson, Allison M.

Increasing atmospheric greenhouse gas concentrations are expected to induce significant climate change over the next century and beyond, but the impacts on society remain highly uncertain. This work examines potential climate change impacts on the productivity of five major crops in northeastern China: canola, corn, potato, rice, and winter wheat. In addition to determining domain-wide trends, the objective is to identify vulnerable and emergent regions under future climate conditions, defined as having a greater than 10% decrease and increase in productivity, respectively. Data from the ICTP RegCM3 regional climate model for baseline (1961-1990) and future (2071-2100) periods under A2 scenariomore » conditions are used as input in the EPIC agro-ecosystem simulation model in the domain [30ºN, 108ºE] to [42ºN, 123ºE]. Simulations are performed with and without the enhanced CO2 fertilization effect. Results indicate that aggregate potential productivity (i.e. if the crop is grown everywhere) increases 6.5% for rice, 8.3% for canola, 18.6% for corn, 22.9% for potato, and 24.9% for winter wheat, although with significant spatial variability for each crop. However, absent the enhanced CO2 fertilization effect, potential productivity declines in all cases ranging from 2.5-12%. Interannual yield variability remains constant or declines in all cases except rice. Climate variables are found to be more significant drivers of simulated yield changes than changes in soil properties, except in the case of potato production in the northwest where the effects of wind erosion are more significant. Overall, in the future period corn and winter wheat benefit significantly in the North China Plain, rice remains dominant in the southeast and emerges in the northeast, potato and corn yields become viable in the northwest, and potato yields suffer in the southwest with no other crop emerging as a clear beneficiary from among those simulated in this study.« less

Climate variability in SE Europe since 1450 AD based on a varved sediment record from Etoliko Lagoon (Western Greece)

NASA Astrophysics Data System (ADS)

Koutsodendris, Andreas; Brauer, Achim; Reed, Jane M.; Plessen, Birgit; Friedrich, Oliver; Hennrich, Barbara; Zacharias, Ierotheos; Pross, Jörg

2017-03-01

To achieve deeper understanding of climate variability during the last millennium in SE Europe, we report new sedimentological and paleoecological data from Etoliko Lagoon, Western Greece. The record represents the southernmost annually laminated (i.e., varved) archive from the Balkan Peninsula spanning the Little Ice Age, allowing insights into critical time intervals of climate instability such as during the Maunder and Dalton solar minima. After developing a continuous, ca. 500-year-long varve chronology, high-resolution μ-XRF counts, stable-isotope data measured on ostracod shells, palynological (including pollen and dinoflagellate cysts), and diatom data are used to decipher the season-specific climate and ecosystem evolution at Etoliko Lagoon since 1450 AD. Our results show that the Etoliko varve record became more sensitive to climate change from 1740 AD onwards. We attribute this shift to the enhancement of primary productivity within the lagoon, which is documented by an up to threefold increase in varve thickness. This marked change in the lagoon's ecosystem was caused by: (i) increased terrestrial input of nutrients, (ii) a closer connection to the sea and human eutrophication particularly from 1850 AD onwards, and (iii) increasing summer temperatures. Integration of our data with those of previously published paleolake sediment records, tree-ring-based precipitation reconstructions, simulations of atmospheric circulation and instrumental precipitation data suggests that wet conditions in winter prevailed during 1740-1790 AD, whereas dry winters marked the periods 1790-1830 AD (Dalton Minimum) and 1830-1930 AD, the latter being sporadically interrupted by wet winters. This variability in precipitation can be explained by shifts in the large-scale atmospheric circulation patterns over the European continent that affected the Balkan Peninsula (e.g., North Atlantic Oscillation). The transition between dry and wet phases at Etoliko points to longitudinal shifts of the precipitation pattern in the Balkan Peninsula during the Little Ice Age.

Pollen-based continental climate reconstructions at 6 and 21 ka: a global synthesis

USGS Publications Warehouse

Bartlein, P.J.; Harrison, S.P.; Brewer, Sandra; Connor, S.; Davis, B.A.S.; Gajewski, K.; Guiot, J.; Harrison-Prentice, T. I.; Henderson, A.; Peyron, O.; Prentice, I.C.; Scholze, M.; Seppa, H.; Shuman, B.; Sugita, S.; Thompson, R.S.; Viau, A.E.; Williams, J.; Wu, H.

2010-01-01

Subfossil pollen and plant macrofossil data derived from 14C-dated sediment profiles can provide quantitative information on glacial and interglacial climates. The data allow climate variables related to growing-season warmth, winter cold, and plant-available moisture to be reconstructed. Continental-scale reconstructions have been made for the mid-Holocene (MH, around 6 ka) and Last Glacial Maximum (LGM, around 21 ka), allowing comparison with palaeoclimate simulations currently being carried out as part of the fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change. The synthesis of the available MH and LGM climate reconstructions and their uncertainties, obtained using modern-analogue, regression and model-inversion techniques, is presented for four temperature variables and two moisture variables. Reconstructions of the same variables based on surface-pollen assemblages are shown to be accurate and unbiased. Reconstructed LGM and MH climate anomaly patterns are coherent, consistent between variables, and robust with respect to the choice of technique. They support a conceptual model of the controls of Late Quaternary climate change whereby the first-order effects of orbital variations and greenhouse forcing on the seasonal cycle of temperature are predictably modified by responses of the atmospheric circulation and surface energy balance.

Winter precipitation effect in a mid-latitude temperature-limited environment: the case of common juniper at high elevation in the Alps

NASA Astrophysics Data System (ADS)

Pellizzari, Elena; Pividori, Mario; Carrer, Marco

2014-10-01

Common juniper (Juniperus communis L.) is by far the most widespread conifer in the world. However, tree-ring research dealing with this species is still scarce, mainly due to the difficulty in crossdating associated with the irregular stem shape with strip-bark growth form in older individuals and the high number of missing and wedging rings. Given that many different species of the same genus have been successfully used in tree-ring investigations and proved to be reliable climate proxies, this study aims to (i) test the possibility to successfully apply dendrochronological techniques on common juniper growing above the treeline and (ii) verify the climate sensitivity of the species with special regard to winter precipitation, a climatic factor that generally does not affect tree-ring growth in all Alpine high-elevation tree species. Almost 90 samples have been collected in three sites in the central and eastern Alps, all between 2100 and 2400 m in elevation. Despite cross-dating difficulties, we were able to build a reliable chronology for each site, each spanning over 200 years. Climate-growth relationships computed over the last century highlight that juniper growth is mainly controlled by the amount of winter precipitation. The high variability of the climate-growth associations among sites, corresponds well to the low spatial dependence of this meteorological factor. Fairly long chronologies and the presence of a significant precipitation signal open up the possibility to reconstruct past winter precipitation.

Stratosphere-Troposphere Coupling in the Northern Hemisphere analyzed with climate network measures

NASA Astrophysics Data System (ADS)

Kirsch, C.; Donner, R. V.

2017-12-01

The Stratosphere-Troposphere Coupling (STC) is a climate phenomenon providing additional predictive skills for extended-range weather forecasting. The variability of the winter stratospheric polar vortex can particularly influence the tropospheric circulation and, hence, mid-to-high latitude weather for a few weeks or months by strong or weak vortex signals propagating downward with time. This study investigates the STC with climate networks. For this purpose, we use the geopotential height field between 20°N and 90°N at 37 vertical levels from the ERA-Interim reanalysis data from 1979 until 2016. There are two main research questions: (i) Is it possible to define a new, more robust index of the variability of the polar vortex than the currently used NAM index by exploiting climate network properties? (ii) What additional information on STC is provided by climate networks? By calculating the transitivity of evolving climate networks at 10 hPa height, we obtain a new characteristic measure for tracing evolving patterns in stratospheric variability. A higher value than the baseline transitivity indicates an anomalous (strong or weak) polar vortex. Displayed for all vertical levels, the transitivity also exhibits the downward propagation of pressure anomalies into the troposphere. Beyond these findings, we observe additional peaks in the transitivity that does not coincide with weak and strong vortex events. These peaks could be used for identifying the change between winter and summer circulation, also called final warming. We will discuss how these results could potentially affect the predictability of tropospheric weather during boreal spring.

Range-wide effects of breeding- and nonbreeding-season climate on the abundance of a Neotropical migrant songbird.

PubMed

Wilson, Scott; LaDeau, Shannon L; Tøttrup, Anders P; Marra, Peter P

2011-09-01

Geographic variation in the population dynamics of a species can result from regional variability in climate and how it affects reproduction and survival. Identifying such effects for migratory birds requires the integration of population models with knowledge of migratory connectivity between breeding and nonbreeding areas. We used Bayesian hierarchical models with 26 years of Breeding Bird Survey data (1982-2007) to investigate the impacts of breeding- and nonbreeding-season climate on abundance of American Redstarts (Setophaga ruticilla) across the species range. We focused on 15 populations defined by Bird Conservation Regions, and we included variation across routes and observers as well as temporal trends and climate effects. American Redstart populations that breed in eastern North America showed increased abundance following winters with higher plant productivity in the Caribbean where they are expected to overwinter. In contrast, western breeding populations showed little response to conditions in their expected wintering areas in west Mexico, perhaps reflecting lower migratory connectivity or differential effects of winter rainfall on individuals across the species range. Unlike the case with winter climate, we found few effects of temperature prior to arrival in spring (March-April) or during the nesting period (May-June) on abundance the following year. Eight populations showed significant changes in abundance, with the steepest declines in the Atlantic Northern Forest (-3.4%/yr) and the greatest increases in the Prairie Hardwood Transition (4%/yr). This study emphasizes how the effects of climate on populations of migratory birds are context dependent and can vary depending on geographic location and the period of the annual cycle. Such knowledge is essential for predicting regional variation in how populations of a species might vary in their response to climate change.

How Will Climate Warming Affect Non-Native Pumpkinseed Lepomis gibbosus Populations in the U.K.?

PubMed Central

Zięba, Grzegorz; Fox, Michael G.; Copp, Gordon H.

2015-01-01

Of the non-native fishes introduced to the U.K., the pumpkinseed is one of six species predicted to benefit from the forecasted climate warming conditions. To demonstrate the potential response of adults and their progeny to a water temperature increase, investigations of parental pumpkinseed acclimatization, reproduction and YOY over-wintering were carried out in outdoor experimental ponds under ambient and elevated water temperature regimes. No temperature effects were observed on either adult survivorship and growth, and none of the assessed reproductive activity variables (total spawning time, spawning season length, number of spawning bouts) appeared to be responsible for the large differences observed in progeny number and biomass. However, it was demonstrated in a previous study [Zięba G. et al., 2010] that adults in the heated ponds began spawning earlier than those of the ambient ponds. Ambient ponds produced 2.8× more progeny than the heated ponds, but these progeny were significantly smaller, probably due to their late hatching date, and subsequently suffered very high mortality over the first winter. Pumpkinseed in the U.K. will clearly benefit from climate warming through earlier seasonal reproduction, resulting in larger progeny going into winter, and as a result, higher over-winter survivorship would be expected relative to that which occurs under the present climatic regime. PMID:26302021

Climate Prediction Center - ENSO FAQ

Science.gov Websites

Weather Service NWS logo - Click to go to the NWS home page Climate Prediction Center Home Site Map News Additional Links General Questions about El Niño and La Niña What is climate variability? What are El Niño . Impacts How do El Niño and La Niña influence the U.S. Winter weather patterns? How do El Niño and La

Hindcasting and forecasting of climatology for Gilbert Bay, Labrador: A marine protected area

NASA Astrophysics Data System (ADS)

Best, Sara J.

Gilbert Bay is a marine protected area (MPA) on the southeastern coast of Labrador, Canada. The MPA was created to conserve a genetically distinctive population of Atlantic cod, Gadus morhua. Future climate change in the region is expected to have an impact on the coastal marine environment and local communities in the future. This thesis presents results from a hindcast and forecasts study of physical oceanographic conditions for Gilbert Bay. The first section of this thesis examines the interannual variability in atmospheric and physical oceanographic characteristics of Gilbert Bay over the period 1949-2006. The seasonal and interannual variability of the near surface atmospheric parameters are described. Seawater temperature, salinity and sea-ice thickness in winter are simulated with a physical ocean model, the General Ocean Turbulence Model (GOTM). The results of the hindcast model suggest that the atmospheric interannual variability of the Gilbert Bay region is linked to the North Atlantic Oscillation (NAO). A warming trend observed in the subpolar North Atlantic was influenced by the local climate of coastal Labrador during the recent decade of 1995-2005. The second section of this thesis presents a model forecast of the impact of climate change on the physical conditions within Gilbert Bay over the next century. Climate scenarios from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment and the US Climate Change Science Program Project (US CCSP), specifically the Special Report on Emission Scenarios (SRES), were used. Atmospheric parameters and related changes in seawater temperature, salinity and sea-ice thickness in winter for three SRES are simulated with the GOTM, and are then compared to the hindcast study results. The results suggest that the water column during future winters will become warmer in the second half of the 21st century. In the summer the atmosphere will be warmer and more humid. Cloudiness and precipitation are expected to increase. This will have an impact on the vertical stratification of the water column. The surface mixed layer is expected to become warmer, fresher and much shallower than seen in the past. The stratification below the seasonal thermocline will weaken and vertical mixing will intensify. A significant change in surface sea-ice coverage is also suggested by the forecast. Continuing reduction in sea-ice formation during the winter months as highlighted by the hindcast study is expected to affect living conditions of the neighbouring coastal communities around the bay, specifically by increasing the danger of travelling across the bay. A warming Gilbert Bay ecosystem may be favourable for cod growth, but reduced sea-ice formation during the winter months increases the danger of travelling across the bay by snowmobile.

Atlantic forcing of Western Mediterranean winter rain minima during the last 12,000 years

NASA Astrophysics Data System (ADS)

Zielhofer, Christoph; Fletcher, William J.; Mischke, Steffen; De Batist, Marc; Campbell, Jennifer F. E.; Joannin, Sebastien; Tjallingii, Rik; El Hamouti, Najib; Junginger, Annett; Stele, Andreas; Bussmann, Jens; Schneider, Birgit; Lauer, Tobias; Spitzer, Katrin; Strupler, Michael; Brachert, Thomas; Mikdad, Abdeslam

2017-02-01

The limited availability of high-resolution continuous archives, insufficient chronological control, and complex hydro-climatic forcing mechanisms lead to many uncertainties in palaeo-hydrological reconstructions for the Western Mediterranean. In this study we present a newly recovered 19.63 m long core from Lake Sidi Ali in the North African Middle Atlas, a transition zone of Atlantic, Western Mediterranean and Saharan air mass trajectories. With a multi-proxy approach based on magnetic susceptibility, carbonate and total organic C content, core-scanning and quantitative XRF, stable isotopes of ostracod shells, charcoal counts, Cedrus pollen abundance, and a first set of diatom data, we reconstruct Western Mediterranean hydro-climatic variability, seasonality and forcing mechanisms during the last 12,000 yr. A robust chronological model based on AMS 14C dated pollen concentrates supports our high-resolution multi-proxy study. Long-term trends reveal low lake levels at the end of the Younger Dryas, during the mid-Holocene interval 6.6 to 5.4 cal ka BP, and during the last 3000 years. In contrast, lake levels are mostly high during the Early and Mid-Holocene. The record also shows sub-millennial- to centennial-scale decreases in Western Mediterranean winter rain at 11.4, 10.3, 9.2, 8.2, 7.2, 6.6, 6.0, 5.4, 5.0, 4.4, 3.5, 2.9, 2.2, 1.9, 1.7, 1.5, 1.0, 0.7, and 0.2 cal ka BP. Early Holocene winter rain minima are in phase with cooling events and millennial-scale meltwater discharges in the sub-polar North Atlantic. Our proxy parameters do not show so far a clear impact of Saharan air masses on Mediterranean hydro-climate in North Africa. However, a significant hydro-climatic shift at the end of the African Humid Period (∼5 ka) indicates a change in climate forcing mechanisms. The Late Holocene climate variability in the Middle Atlas features a multi-centennial-scale NAO-type pattern, with Atlantic cooling and Western Mediterranean winter rain maxima generally associated with solar minima.

Wave climate simulation for southern region of the South China Sea

NASA Astrophysics Data System (ADS)

Mirzaei, Ali; Tangang, Fredolin; Juneng, Liew; Mustapha, Muzneena Ahmad; Husain, Mohd Lokman; Akhir, Mohd Fadzil

2013-08-01

This study investigates long-term variability and wave characteristic trends in the southern region of the South China Sea (SCS). We implemented the state-of-the art WAVEWATCH III spectral wave model to simulate a 31-year wave hindcast. The simulation results were used to assess the inter-annual variability and long-term changes in the SCS wave climate for the period 1979 to 2009. The model was forced with Climate Forecast System Reanalysis winds and validated against altimeter data and limited available measurements from an Acoustic Wave and Current recorder located offshore of Terengganu, Malaysia. The mean annual significant wave height and peak wave period indicate the occurrence of higher wave heights and wave periods in the central SCS and lower in the Sunda shelf region. Consistent with wind patterns, the wave direction also shows southeasterly (northwesterly) waves during the summer (winter) monsoon. This detailed hindcast demonstrates strong inter-annual variability of wave heights, especially during the winter months in the SCS. Significant wave height correlated negatively with Niño3.4 index during winter, spring and autumn seasons but became positive in the summer monsoon. Such correlations correspond well with surface wind anomalies over the SCS during El Nino events. During El Niño Modoki, the summer time positive correlation extends northeastwards to cover the entire domain. Although significant positive trends were found at 95 % confidence levels during May, July and September, there is significant negative trend in December covering the Sunda shelf region. However, the trend appears to be largely influenced by large El Niño signals.

The predicted influence of climate change on lesser prairie-chicken reproductive parameters

USGS Publications Warehouse

Grisham, Blake A.; Boal, Clint W.; Haukos, David A.; Davis, D.; Boydston, Kathy K.; Dixon, Charles; Heck, Willard R.

2013-01-01

The Southern High Plains is anticipated to experience significant changes in temperature and precipitation due to climate change. These changes may influence the lesser prairie-chicken (Tympanuchus pallidicinctus) in positive or negative ways. We assessed the potential changes in clutch size, incubation start date, and nest survival for lesser prairie-chickens for the years 2050 and 2080 based on modeled predictions of climate change and reproductive data for lesser prairie-chickens from 2001-2011 on the Southern High Plains of Texas and New Mexico. We developed 9 a priori models to assess the relationship between reproductive parameters and biologically relevant weather conditions. We selected weather variable(s) with the most model support and then obtained future predicted values from climatewizard.org. We conducted 1,000 simulations using each reproductive parameter's linear equation obtained from regression calculations, and the future predicted value for each weather variable to predict future reproductive parameter values for lesser prairie-chickens. There was a high degree of model uncertainty for each reproductive value. Winter temperature had the greatest effect size for all three parameters, suggesting a negative relationship between above-average winter temperature and reproductive output. The above-average winter temperatures are correlated to La Nina events, which negatively affect lesser prairie-chickens through resulting drought conditions. By 2050 and 2080, nest survival was predicted to be below levels considered viable for population persistence; however, our assessment did not consider annual survival of adults, chick survival, or the positive benefit of habitat management and conservation, which may ultimately offset the potentially negative effect of drought on nest survival.

The predicted influence of climate change on lesser prairie-chicken reproductive parameters.

PubMed

Grisham, Blake A; Boal, Clint W; Haukos, David A; Davis, Dawn M; Boydston, Kathy K; Dixon, Charles; Heck, Willard R

2013-01-01

The Southern High Plains is anticipated to experience significant changes in temperature and precipitation due to climate change. These changes may influence the lesser prairie-chicken (Tympanuchus pallidicinctus) in positive or negative ways. We assessed the potential changes in clutch size, incubation start date, and nest survival for lesser prairie-chickens for the years 2050 and 2080 based on modeled predictions of climate change and reproductive data for lesser prairie-chickens from 2001-2011 on the Southern High Plains of Texas and New Mexico. We developed 9 a priori models to assess the relationship between reproductive parameters and biologically relevant weather conditions. We selected weather variable(s) with the most model support and then obtained future predicted values from climatewizard.org. We conducted 1,000 simulations using each reproductive parameter's linear equation obtained from regression calculations, and the future predicted value for each weather variable to predict future reproductive parameter values for lesser prairie-chickens. There was a high degree of model uncertainty for each reproductive value. Winter temperature had the greatest effect size for all three parameters, suggesting a negative relationship between above-average winter temperature and reproductive output. The above-average winter temperatures are correlated to La Niña events, which negatively affect lesser prairie-chickens through resulting drought conditions. By 2050 and 2080, nest survival was predicted to be below levels considered viable for population persistence; however, our assessment did not consider annual survival of adults, chick survival, or the positive benefit of habitat management and conservation, which may ultimately offset the potentially negative effect of drought on nest survival.

Impact of Climate Change on Potential, Attainable, and Actual Wheat Yield in Oklahoma

NASA Astrophysics Data System (ADS)

Dhakal, K.; Linde, E.; Kakani, V. G.; Alderman, P. D.; Brunson, D.; Ochsner, T. E.; Carver, B.

2017-12-01

Gradually developing climatic and weather anomalies due to increasing atmospheric greenhouse gases concentration can pose threat to farmers and resource managers. This study was aimed at investigating the effects of climate change on winter wheat (Triticum aestivum L.) under the Representative Concentration Pathways 6.0 and 8.5 using downscaled climate projections from different models and their ensembles. Daily data of maximum and minimum air temperature, rainfall, and solar radiation for, four General Circulation Models (MRIOC5, MRI-CGCM3, HadGEM2-ES, CSRIO-Mk3.6.0), ensemble of four models and ensemble of 17 GCMs, at 800 m resolution, were developed for two RCPs using Marksim. We describe a methodology for rapid synthesis of GCM-based, spatially explicit, high resolution future weather data inputs for the DSSAT crop model, for cropland area across wheat growing regions of Oklahoma for the future period 2040-2060. The potential impacts of climate change and variability on potential, attainable, and actual winter wheat yield in Oklahoma is discussed.

Effect of Climate Change on Mediterranean Winter Ranges of Two Migratory Passerines.

PubMed

Tellería, José L; Fernández-López, Javier; Fandos, Guillermo

2016-01-01

We studied the effect of climate change on the distribution of two insectivorous passerines (the meadow pipit Anthus pratensis and the chiffchaff Phylloscopus collybita) in wintering grounds of the Western Mediterranean basin. In this region, precipitation and temperature can affect the distribution of these birds through direct (thermoregulation costs) or indirect effects (primary productivity). Thus, it can be postulated that projected climate changes in the region will affect the extent and suitability of their wintering grounds. We studied pipit and chiffchaff abundance in several hundred localities along a belt crossing Spain and Morocco and assessed the effects of climate and other geographical and habitat predictors on bird distribution. Multivariate analyses reported a positive effect of temperature on the present distribution of the two species, with an additional effect of precipitation on the meadow pipit. These climate variables were used with Maxent to model the occurrence probabilities of species using ring recoveries as presence data. Abundance and occupancy of the two species in the study localities adjusted to the distribution models, with more birds in sectors of high climate suitability. After validation, these models were used to forecast the distribution of climate suitability according to climate projections for 2050-2070 (temperature increase and precipitation reduction). Results show an expansion of climatically suitable sectors into the highlands by the effect of warming on the two species, and a retreat of the meadow pipit from southern sectors related to rain reduction. The predicted patterns show a mean increase in climate suitability for the two species due to the warming of the large highland expanses typical of the western Mediterranean.

Ensembles modeling approach to study Climate Change impacts on Wheat

NASA Astrophysics Data System (ADS)

Ahmed, Mukhtar; Claudio, Stöckle O.; Nelson, Roger; Higgins, Stewart

2017-04-01

Simulations of crop yield under climate variability are subject to uncertainties, and quantification of such uncertainties is essential for effective use of projected results in adaptation and mitigation strategies. In this study we evaluated the uncertainties related to crop-climate models using five crop growth simulation models (CropSyst, APSIM, DSSAT, STICS and EPIC) and 14 general circulation models (GCMs) for 2 representative concentration pathways (RCP) of atmospheric CO2 (4.5 and 8.5 W m-2) in the Pacific Northwest (PNW), USA. The aim was to assess how different process-based crop models could be used accurately for estimation of winter wheat growth, development and yield. Firstly, all models were calibrated for high rainfall, medium rainfall, low rainfall and irrigated sites in the PNW using 1979-2010 as the baseline period. Response variables were related to farm management and soil properties, and included crop phenology, leaf area index (LAI), biomass and grain yield of winter wheat. All five models were run from 2000 to 2100 using the 14 GCMs and 2 RCPs to evaluate the effect of future climate (rainfall, temperature and CO2) on winter wheat phenology, LAI, biomass, grain yield and harvest index. Simulated time to flowering and maturity was reduced in all models except EPIC with some level of uncertainty. All models generally predicted an increase in biomass and grain yield under elevated CO2 but this effect was more prominent under rainfed conditions than irrigation. However, there was uncertainty in the simulation of crop phenology, biomass and grain yield under 14 GCMs during three prediction periods (2030, 2050 and 2070). We concluded that to improve accuracy and consistency in simulating wheat growth dynamics and yield under a changing climate, a multimodel ensemble approach should be used.

Uncertainties in Hydrologic and Climate Change Impact Analysis in Major Watersheds in British Columbia, Canada

NASA Astrophysics Data System (ADS)

Bennett, K. E.; Schnorbus, M.; Werner, A. T.; Music, B.; Caya, D.; Rodenhuis, D. R.

2009-12-01

Uncertainties in the projections of future hydrologic change can be assessed using a suite of tools, thereby allowing researchers to focus on improvement to identifiable sources of uncertainty. A pareto set of optimal hydrologic parameterizations was run for three BC watersheds (Fraser, Peace and Columbia) for a range of downscaled Global Climate Model (GCM) emission scenarios to illustrate the uncertainty in hydrologic response to climate change. Results show varying responses of hydrologic regimes across geographic landscapes. Uncertainties in streamflow and water balance (runoff, evapo-transpiration, snow water equivalent, soil moisture) were analysed by forcing the Variable Infiltration Capacity (VIC) hydrologic model, run under twenty-five optimal parameter solution sets using six Bias-Corrected Statistically Downscaled (BCSD) GCM emission scenario projections for the 2050s and the 2080s. Projected changes by the 2050s include increased winter flows, increases and decreases in freshet magnitude depending on the scenario, and decreases in summer flows persisting until September. Winter runoff had the greatest range between GCM emission scenarios, while the hydrologic parameters within individual GCM emission scenarios had a winter runoff range an order of magnitude smaller. Evapo-transpiration, snow water equivalent and soil moisture exhibited a spread of ~10% or less. Streamflow changes by the 2080s lie outside the natural range of historic variability over the winter and spring. Results indicate that the changes projected between GCM emission scenarios are greater than the differences between the hydrologic model parameterizations. An alternate tool, the Canadian Regional Climate Model (CRCM) has been set up for these watersheds and various runs have been analysed to determine the range and variability present and to examine these results in comparison to the hydrologic model projections. The CRCM range and variability is an improvement over the Canadian GCM and thus requires less bias correction. However, without downscaling the CRCM results are still coarser than what is required to drive macroscale hydrologic models, such as VIC. Applying these tools has illustrated the importance of focusing on improved downscaling efforts, including downscaling CRCM results rather than CGCM data. Tools for decision-making in the face of uncertainty are emerging as a priority for the climate change impacts community, and there is a need to focus on incorporating uncertainty information along with the projection of impacts. Assessing uncertainty across a range of regimes and geographic regions can assist to identify the main sources of uncertainty and allow researchers to focus on improving those sources using more robust methodological approaches and tools.

Snow-atmosphere coupling and its impact on temperature variability and extremes over North America

NASA Astrophysics Data System (ADS)

Diro, G. T.; Sushama, L.; Huziy, O.

2018-04-01

The impact of snow-atmosphere coupling on climate variability and extremes over North America is investigated using modeling experiments with the fifth generation Canadian Regional Climate Model (CRCM5). To this end, two CRCM5 simulations driven by ERA-Interim reanalysis for the 1981-2010 period are performed, where snow cover and depth are prescribed (uncoupled) in one simulation while they evolve interactively (coupled) during model integration in the second one. Results indicate systematic influence of snow cover and snow depth variability on the inter-annual variability of soil and air temperatures during winter and spring seasons. Inter-annual variability of air temperature is larger in the coupled simulation, with snow cover and depth variability accounting for 40-60% of winter temperature variability over the Mid-west, Northern Great Plains and over the Canadian Prairies. The contribution of snow variability reaches even more than 70% during spring and the regions of high snow-temperature coupling extend north of the boreal forests. The dominant process contributing to the snow-atmosphere coupling is the albedo effect in winter, while the hydrological effect controls the coupling in spring. Snow cover/depth variability at different locations is also found to affect extremes. For instance, variability of cold-spell characteristics is sensitive to snow cover/depth variation over the Mid-west and Northern Great Plains, whereas, warm-spell variability is sensitive to snow variation primarily in regions with climatologically extensive snow cover such as northeast Canada and the Rockies. Furthermore, snow-atmosphere interactions appear to have contributed to enhancing the number of cold spell days during the 2002 spring, which is the coldest recorded during the study period, by over 50%, over western North America. Additional results also provide useful information on the importance of the interactions of snow with large-scale mode of variability in modulating temperature extreme characteristics.

Snow-Cover Variability in North America in the 2000-2001 Winter as Determined from MODIS Snow Products

NASA Technical Reports Server (NTRS)

Hall, Dorothy K.; Salomonson, Vincent V.; Riggs, George A.; Chien, Janet Y. L.; Houser, Paul R. (Technical Monitor)

2001-01-01

Moderate Resolution Imaging Spectroradiometer (MODIS) snow-cover maps have been available since September 13, 2000. These products, at 500 m spatial resolution, are available through the National Snow and Ice Data Center Distributed Active Archive Center in Boulder, Colorado. By the 2001-02 winter, 5 km climate-modeling grid (CMG) products will be available for presentation of global views of snow cover and for use in climate models. All MODIS snow-cover products are produced from automated algorithms that map snow in an objective manner. In this paper, we describe the MODIS snow products, and show snow maps from the fall of 2000 in North America.

Snow-Cover Variability in North America in the 2000-2001 Winter as Determined from MODIS Snow Products

NASA Technical Reports Server (NTRS)

Hall, Dorothy K.; Salomonson, Vincent V.; Riggs, George A.; Chien, Y. L.; Houser, Paul R. (Technical Monitor)

2001-01-01

Moderate Resolution Imaging Spectroradiometer (MODIS) snow-cover maps have been available since September 13, 2000. These products, at 500-m spatial resolution, are available through the National Snow and Ice Data Center Distributed Active Archive Center in Boulder, Colorado. By the 2001-02 winter, 5-km climate-modeling grid (CMG) products will be available for presentation of global views of snow cover and for use in climate models. All MODIS snow-cover products are produced from automated algorithms that map snow in an objective manner. In this paper, we describe the MODIS snow products, and show snow maps from the fall of 2000 in North America.

Demographic consequences of climate change and land cover help explain a history of extirpations and range contraction in a declining snake species.

PubMed

Pomara, Lars Y; LeDee, Olivia E; Martin, Karl J; Zuckerberg, Benjamin

2014-07-01

Developing conservation strategies for threatened species increasingly requires understanding vulnerabilities to climate change, in terms of both demographic sensitivities to climatic and other environmental factors, and exposure to variability in those factors over time and space. We conducted a range-wide, spatially explicit climate change vulnerability assessment for Eastern Massasauga (Sistrurus catenatus), a declining endemic species in a region showing strong environmental change. Using active season and winter adult survival estimates derived from 17 data sets throughout the species' range, we identified demographic sensitivities to winter drought, maximum precipitation during the summer, and the proportion of the surrounding landscape dominated by agricultural and urban land cover. Each of these factors was negatively associated with active season adult survival rates in binomial generalized linear models. We then used these relationships to back-cast adult survival with dynamic climate variables from 1950 to 2008 using spatially explicit demographic models. Demographic models for 189 population locations predicted known extant and extirpated populations well (AUC = 0.75), and models based on climate and land cover variables were superior to models incorporating either of those effects independently. These results suggest that increasing frequencies and severities of extreme events, including drought and flooding, have been important drivers of the long-term spatiotemporal variation in a demographic rate. We provide evidence that this variation reflects nonadaptive sensitivity to climatic stressors, which are contributing to long-term demographic decline and range contraction for a species of high-conservation concern. Range-wide demographic modeling facilitated an understanding of spatial shifts in climatic suitability and exposure, allowing the identification of important climate refugia for a dispersal-limited species. Climate change vulnerability assessment provides a framework for linking demographic and distributional dynamics to environmental change, and can thereby provide unique information for conservation planning and management. © 2013 John Wiley & Sons Ltd.

Covariability of seasonal temperature and precipitation over the Iberian Peninsula in high-resolution regional climate simulations (1001-2099)

NASA Astrophysics Data System (ADS)

Fernández-Montes, S.; Gómez-Navarro, J. J.; Rodrigo, F. S.; García-Valero, J. A.; Montávez, J. P.

2017-04-01

Precipitation and surface temperature are interdependent variables, both as a response to atmospheric dynamics and due to intrinsic thermodynamic relationships and feedbacks between them. This study analyzes the covariability of seasonal temperature (T) and precipitation (P) across the Iberian Peninsula (IP) using regional climate paleosimulations for the period 1001-1990, driven by reconstructions of external forcings. Future climate (1990-2099) was simulated according to SRES scenarios A2 and B2. These simulations enable exploring, at high spatial resolution, robust and physically consistent relationships. In winter, positive P-T correlations dominate west-central IP (Pearson correlation coefficient ρ = + 0.43, for 1001-1990), due to prevalent cold-dry and warm-wet conditions, while this relationship weakens and become negative towards mountainous, northern and eastern regions. In autumn, negative correlations appear in similar regions as in winter, whereas for summer they extend also to the N/NW of the IP. In spring, the whole IP depicts significant negative correlations, strongest for eastern regions (ρ = - 0.51). This is due to prevalent frequency of warm-dry and cold-wet modes in these regions and seasons. At the temporal scale, regional correlation series between seasonal anomalies of temperature and precipitation (assessed in 31 years running windows in 1001-1990) show very large multidecadal variability. For winter and spring, periodicities of about 50-60 years arise. The frequency of warm-dry and cold-wet modes appears correlated with the North Atlantic Oscillation (NAO), explaining mainly co-variability changes in spring. For winter and some regions in autumn, maximum and minimum P-T correlations appear in periods with enhanced meridional or easterly circulation (low or high pressure anomalies in the Mediterranean and Europe). In spring and summer, the Atlantic Multidecadal Oscillation shows some fingerprint on the frequency of warm/cold modes. For future scenarios, an intensification of the negative P-T relationship is generally found, as a result of an increased frequency of the warm-dry mode.

The influence of land cover on surface energy partitioning and evaporative fraction regimes in the U.S. Southern Great Plains

NASA Astrophysics Data System (ADS)

Bagley, Justin E.; Kueppers, Lara M.; Billesbach, Dave P.; Williams, Ian N.; Biraud, Sébastien C.; Torn, Margaret S.

2017-06-01

Land-atmosphere interactions are important to climate prediction, but the underlying effects of surface forcing of the atmosphere are not well understood. In the U.S. Southern Great Plains, grassland/pasture and winter wheat are the dominant land covers but have distinct growing periods that may differently influence land-atmosphere coupling during spring and summer. Variables that influence surface flux partitioning can change seasonally, depending on the state of local vegetation. Here we use surface observations from multiple sites in the U.S. Department of Energy Atmospheric Radiation Measurement Southern Great Plains Climate Research Facility and statistical modeling at a paired grassland/agricultural site within this facility to quantify land cover influence on surface energy balance and variables controlling evaporative fraction (latent heat flux normalized by the sum of sensible and latent heat fluxes). We demonstrate that the radiative balance and evaporative fraction are closely related to green leaf area at both winter wheat and grassland/pasture sites and that the early summer harvest of winter wheat abruptly shifts the relationship between evaporative fraction and surface state variables. Prior to harvest, evaporative fraction of winter wheat is strongly influenced by leaf area and soil-atmosphere temperature differences. After harvest, variations in soil moisture have a stronger effect on evaporative fraction. This is in contrast with grassland/pasture sites, where variation in green leaf area has a large influence on evaporative fraction throughout spring and summer, and changes in soil-atmosphere temperature difference and soil moisture are of relatively minor importance.

Climate variations and changes in mass of three glaciers in western North America

USGS Publications Warehouse

Hodge, S.M.; Trabant, D.C.; Krimmel, R.M.; Heinrichs, T.A.; March, R.S.; Josberger, E.G.

1998-01-01

Time series of net and seasonal mass balances for three glaciers in western North America, one in the Pacific Northwest and two in Alaska, show various relationships to Pacific hemisphere climate indexes. During the winter season the two coastal, maritime-regime glaciers, over 2000 km apart, are affected almost identically, albeit inversely, by atmospheric and oceanic conditions in both the tropical and North Pacific. The two Alaska glaciers, only 350 km apart, have almost no coherence. Lag correlations show that in winter the maritime glaciers are influenced by concurrent conditions in the North Pacific, but by conditions in the tropical Pacific in August-September of the prior northern summer. The winter balance variations contain interannual El Nino-Southern Oscillation variability superimposed on North Pacific interdecadal variability; the interdecadal 1976-77 climate regime shift is clearly evident. The summer balances and the continental-regime glacier have a general lack of correlations, with no clear, strong, consistent patterns, probably a result of being influenced more by local processes or by circulation patterns outside the Pacific Ocean basin. The results show the Pacific Northwest is strongly influenced by conditions in the tropical Pacific, but that this teleconnection has broken down in recent years, starting in 1989. During the seven years since then (1989-95), all three glaciers have shown, for the first time, coherent signals, which were net mass loss at the highest rate in the entire record. The authors' results agree with those of other recent studies that suggest these recent years are unusual and may be a signature of climate warming.

Climate change and dissolved organic carbon export to the Gulf of Maine

USGS Publications Warehouse

Huntington, Thomas G.; Balch, William M.; Aiken, George R.; Sheffield, Justin; Luo, Lifeng; Roesler, Collin S.; Camill, Philip

2016-01-01

Ongoing climate change is affecting the concentration, export (flux), and timing of dissolved organic carbon (DOC) exported to the Gulf of Maine (GoM) through changes in hydrologic regime. DOC export was calculated for water years 1950 through 2013 for 20 rivers and for water years 1930 through 2013 for 14 rivers draining to the GoM. DOC export was also estimated for the 21st century based on climate and hydrologic modeling in a previously published study. DOC export was calculated by using the regression model LOADEST to fit seasonally adjusted concentration discharge (C-Q) relations. Our results are an analysis of the sensitivity of DOC export to changes in hydrologic conditions over time since land cover and vegetation were held constant over time. Despite large interannual variability, all rivers had increasing DOC export during winter and these trends were significant (p < 0.05) in 10 out of 20 rivers for 1950 to 2013 and in 13 out of 14 rivers for 1930 to 2013. All rivers also had increasing annual export of DOC although fewer trends were statistically significant than for winter export. Projections for DOC export during the 21st century were variable depending on the climate model and greenhouse gas emission scenario that affected future river discharge through effects on precipitation and evapotranspiration. The most consistent result was a significant increase in DOC export in winter in all model-by-emission scenarios. DOC export was projected to decrease during the summer in all model-by-emission scenarios, with statistically significant decreases in half of the scenarios.

Evolution of a genetic polymorphism with climate change in a Mediterranean landscape

PubMed Central

Thompson, John; Charpentier, Anne; Bouguet, Guillaume; Charmasson, Faustine; Roset, Stephanie; Buatois, Bruno; Vernet, Philippe; Gouyon, Pierre-Henri

2013-01-01

Many species show changes in distribution and phenotypic trait variation in response to climatic warming. Evidence of genetically based trait responses to climate change is, however, less common. Here, we detected evolutionary variation in the landscape-scale distribution of a genetically based chemical polymorphism in Mediterranean wild thyme (Thymus vulgaris) in association with modified extreme winter freezing events. By comparing current data on morph distribution with that observed in the early 1970s, we detected a significant increase in the proportion of morphs that are sensitive to winter freezing. This increase in frequency was observed in 17 of the 24 populations in which, since the 1970s, annual extreme winter freezing temperatures have risen above the thresholds that cause mortality of freezing-sensitive morphs. Our results provide an original example of rapid ongoing evolutionary change associated with relaxed selection (less extreme freezing events) on a local landscape scale. In species whose distribution and genetic variability are shaped by strong selection gradients, there may be little time lag associated with their ecological and evolutionary response to long-term environmental change. PMID:23382198

Correlation between asthma and climate in the European Community Respiratory Health Survey.

PubMed

Verlato, Giuseppe; Calabrese, Rolando; De Marco, Roberto

2002-01-01

The European Community Respiratory Health Survey, performed during 1991-1993, found a remarkable geographical variability in the prevalence of asthma and asthma-like symptoms in individuals aged 20-44 yr. The highest values occurred in the English-speaking centers. In the present investigation, the ecological relationship between climate and symptom prevalence was evaluated in the 48 centers of the European Community Respiratory Health Survey. Meteorological variables were derived from the Global Historical Climatology Network and were averaged over an 11-yr period (i.e., 1980-1990). Respiratory symptom prevalence was directly related to temperature in the coldest month and was related inversely to the temperature in the hottest month. Warm winters and cool summers are features of oceanic climate found in most English-speaking centers of the European Community Respiratory Health Survey (i.e., England, New Zealand, and Oregon). In conclusion, climate can account for significant geographic variability in respiratory symptom prevalence.

Effects of harvest and climate on population dynamics of northern bobwhites in south Florida

USGS Publications Warehouse

Rolland, V.; Hostetler, J.A.; Hines, T.C.; Johnson, F.A.; Percival, H.F.; Oli, M.K.

2011-01-01

Context Hunting-related (hereafter harvest) mortality is assumed to be compensatory in many exploited species. However, when harvest mortality is additive, hunting can lead to population declines, especially on public land where hunting pressure can be intense. Recent studies indicate that excessive hunting may have contributed to the decline of a northern bobwhite (Colinus virginianus) population in south Florida. Aims This study aimed to estimate population growth rates to determine potential and actual contribution of vital rates to annual changes in population growth rates, and to evaluate the role of harvest and climatic variables on bobwhite population decline. Methods We used demographic parameters estimated from a six-year study to parameterise population matrix models and conduct prospective and retrospective perturbation analyses. Key results The stochastic population growth rate (?? S=0.144) was proportionally more sensitive to adult winter survival and survival of fledglings, nests and broods from first nesting attempts; the same variables were primarily responsible for annual changes in population growth rate. Demographic parameters associated with second nesting attempts made virtually no contribution to population growth rate. All harvest scenarios consistently revealed a substantial impact of harvest on bobwhite population dynamics. If the lowest harvest level recorded in the study period (i.e. 0.08 birds harvested per day per km2 in 2008) was applied, S would increase by 32.1%. Winter temperatures and precipitation negatively affected winter survival, and precipitation acted synergistically with harvest in affecting winter survival. Conclusions Our results suggest that reduction in winter survival due to overharvest has been an important cause of the decline in our study population, but that climatic factors might have also played a role. Thus, for management actions to be effective, assessing the contribution of primary (e.g. harvesting) but also secondary factors (e.g. climate) to population decline may be necessary. Implications Reducing hunting pressure would be necessary for the recovery of the bobwhite population at our study site. In addition, an adaptive harvest management strategy that considers weather conditions in setting harvest quota would help reverse the population decline further. ?? 2011 CSIRO.

A Winter Distribution Model for Bicknell’s Thrush (Catharus bicknelli), a Conservation Tool for a Threatened Migratory Songbird

PubMed Central

McFarland, Kent P.; Rimmer, Christopher C.; Goetz, James E.; Aubry, Yves; Wunderle, Joseph M.; Sutton, Anne; Townsend, Jason M.; Sosa, Alejandro Llanes; Kirkconnell, Arturo

2013-01-01

Conservation planning and implementation require identifying pertinent habitats and locations where protection and management may improve viability of targeted species. The winter range of Bicknell’s Thrush (Catharus bicknelli), a threatened Nearctic-Neotropical migratory songbird, is restricted to the Greater Antilles. We analyzed winter records from the mid-1970s to 2009 to quantitatively evaluate winter distribution and habitat selection. Additionally, we conducted targeted surveys in Jamaica (n = 433), Cuba (n = 363), Dominican Republic (n = 1,000), Haiti (n = 131) and Puerto Rico (n = 242) yielding 179 sites with thrush presence. We modeled Bicknell’s Thrush winter habitat selection and distribution in the Greater Antilles in Maxent version 3.3.1. using environmental predictors represented in 30 arc second study area rasters. These included nine landform, land cover and climatic variables that were thought a priori to have potentially high predictive power. We used the average training gain from ten model runs to select the best subset of predictors. Total winter precipitation, aspect and land cover, particularly broadleaf forests, emerged as important variables. A five-variable model that contained land cover, winter precipitation, aspect, slope, and elevation was the most parsimonious and not significantly different than the models with more variables. We used the best fitting model to depict potential winter habitat. Using the 10 percentile threshold (>0.25), we estimated winter habitat to cover 33,170 km2, nearly 10% of the study area. The Dominican Republic contained half of all potential habitat (51%), followed by Cuba (15.1%), Jamaica (13.5%), Haiti (10.6%), and Puerto Rico (9.9%). Nearly one-third of the range was found to be in protected areas. By providing the first detailed predictive map of Bicknell’s Thrush winter distribution, our study provides a useful tool to prioritize and direct conservation planning for this and other wet, broadleaf forest specialists in the Greater Antilles. PMID:23326554

Determining the spatial variability of crop yields of two different climatic regions in Southwest Germany

NASA Astrophysics Data System (ADS)

Eshonkulov, Ravshan; Poyda, Arne; Ingwersen, Joachim; Streck, Thilo

2017-04-01

Assessing the spatial variability of soil physical properties is crucial for agricultural land management. We determined the spatial variability within two agricultural fields in the regions of Kraichgau and Swabian Jura in Southwest Germany. We determined soil physical properties and recorded the temporal development of soil mineral nitrogen (N) and water content as well as that of plant variables (phenology, biomass, leaf area index (LAI), N content, green vegetation fraction (GVF). The work was conducted during the vegetation periods of 2015 and 2016 in winter wheat, and winter rapeseed in Kraichgau and winter barley and silage maize on Swabian Jura. Measurements were taken in three-weekly intervals. On each field, we identified three plots with reduced plant development using high-resolution (RapidEye) satellite images ("cold spots"). Measurements taken on these cold spots were compared to those from five established (long-term) reference plots representing the average field variability. The software EXPERT-N was used to simulate the soil crop system at both cold spots and reference plots. Sensitivity analyses were conducted to identify the most important parameters for the determination of spatial variability in crop growth dynamics.

Contributions of dynamic environmental signals during life-cycle transitions to early life-history traits in lodgepole pine (Pinus contorta Dougl.)

NASA Astrophysics Data System (ADS)

Liu, Y.; Wang, T.; El-Kassaby, Y. A.

2015-08-01

Environmental signals are important triggers in the life-cycle transitions and play a crucial role in the life-history evolution. Yet, very little is known about the leading ecological factors contributing to the variations of life-history traits in perennial plants. This paper explores both the causes and consequences for the evolution of life-history traits (i.e., seed dormancy and size) in lodgepole pine (Pinus contorta Dougl.) across British Columbia (B.C.), Canada. We selected 83 logepole pine populations covering 22 ecosystem zones of B.C. and through their geographic coordinate, 197 climatic variables were generated accordingly for the reference (1961-1990) and future (2041-2070) periods. We found that dynamic climatic variables rather than constant geographic variables are the true environmental driving forces in seed dormancy and size variations and thus provide reliable predictors in response to global climate change. Evapotranspiration and precipitation in the plant-to-seed chronology are the most critical climate variables for seed dormancy and size variations, respectively. Hence, we predicted that levels of seed dormancy in lodgepole pine would increase across large tracts of B.C. in 2050s. Winter-chilling is able to increase the magnitude of life-history plasticity and lower the bet-hedge strategy in the seed-to-plant transition; however, winter-chilling is likely to be insufficient in the north of 49° N in 2050s, which may delay germination while unfavourable conditions during dry summers may result in adverse consequences in the survival of seedlings owing to extended germination span.

Ecological controls on water-cycle response to climate variability in deserts

PubMed Central

Scanlon, B. R.; Levitt, D. G.; Reedy, R. C.; Keese, K. E.; Sully, M. J.

2005-01-01

The impact of climate variability on the water cycle in desert ecosystems is controlled by biospheric feedback at interannual to millennial timescales. This paper describes a unique field dataset from weighing lysimeters beneath nonvegetated and vegetated systems that unequivocally demonstrates the role of vegetation dynamics in controlling water cycle response to interannual climate variability related to El Niño southern oscillation in the Mojave Desert. Extreme El Niño winter precipitation (2.3-2.5 times normal) typical of the U.S. Southwest would be expected to increase groundwater recharge, which is critical for water resources in semiarid and arid regions. However, lysimeter data indicate that rapid increases in vegetation productivity in response to elevated winter precipitation reduced soil water storage to half of that in a nonvegetated lysimeter, thereby precluding deep drainage below the root zone that would otherwise result in groundwater recharge. Vegetation dynamics have been controlling the water cycle in interdrainage desert areas throughout the U.S. Southwest, maintaining dry soil conditions and upward soil water flow since the last glacial period (10,000-15,000 yr ago), as shown by soil water chloride accumulations. Although measurements are specific to the U.S. Southwest, correlations between satellite-based vegetation productivity and elevated precipitation related to El Niño southern oscillation indicate this model may be applicable to desert basins globally. Understanding the two-way coupling between vegetation dynamics and the water cycle is critical for predicting how climate variability influences hydrology and water resources in water-limited landscapes. PMID:15837922

Comparison of the Impact of the Arctic Oscillation and East Atlantic - West Russia Teleconnection on Interannual Variation in East Asian Winter Temperatures and Monsoon

NASA Technical Reports Server (NTRS)

Lim, Young-Kwon; Kim, Hae-Dong

2014-01-01

The large-scale impacts of the Arctic Oscillation (AO) and the East Atlantic/West Russia (EA/WR) teleconnection on the East Asian winter climate anomalies are compared for the past 34 winters focusing on 1) interannual monthly to seasonal temperature variability, 2) East Asian winter monsoon (EAWM), and 3) the Siberian high (SH) and cold surge. Regression analysis reveals warming by AO and EA/WR over mid-latitude East Asia during their positive phase and vice versa. The EA/WR impact is found to be comparable to the AO impact in affecting the East Asian temperature and monsoon. For example, warm (cold) months over mid-latitude East Asia during the positive (negative) AO are clearly seen when the AO and EA/WR are in the same phase. Near zero correlation is found between temperature and the AO phase when both teleconnections are in an opposite phase. The well-known negative relationship between SH and the AO phase is observed significantly more often when the AO is in the same phase with the EA/WR. Also, the indices of EAWM, cold surge, and SH are found to be more highly negative-correlated with the EA/WR rather than with the AO. The advective temperature change and associated circulation demonstrate that the anomalous large-scale field including the SH over the mid-latitude Asian inland is better represented by the EA/WR, influencing the East Asian winter climates. These results suggest that the impact of EA/WR should be considered more important than previously thought for a better understanding of East Asian winter temperature and monsoon variability.

Remote sensing of ecosystem vulnerability: Assessing climate-vegetation-livestock interactions in Mongolia

NASA Astrophysics Data System (ADS)

Kang, S.; Hong, S. Y.

2015-12-01

Stock breeding is a major economic sector of Mongolia, supporting unique cultural and social identity. In spite of its long history, contemporary pastoralism increases interventions on climate-vegetation interactions substantially, which results in negative feedbacks to livestock sector. This presentation draws an attention how natural processes of climate and vegetation interact with livestock dynamics. Massive loss of livestock and wildlife animal during winter seasons (dzud) is an endemic climatic disaster in the Central Asia grasslands but the mechanisms are not well understood yet. Recent national-wide sever Dzud occurred during 2009-2010 winter in Mongolia. The dzud mechanisms were investigated by developing a schematic mechanism model on climate-vegetation-livestock interactions and applying it for quantitative statistical analysis. Various remote sensing products were integrated to prepare the status and process variables of the schematic model, including daily temperature, precipitation, evapotranspiration, and primary production and biomass for a period from 2003 to 2010. At a lower level of administration (i.e., 'soum' generally larger than 1000 km2), stepwise multiple regression analysis was conducted to find significant factors of inter-annual livestock change. As results, linear regression models were successfully produced at 70% of soums. Summer and winter variables appeared equally important in controlling livestock dynamics. The primary factor of each soum showed certain regional patterns incident well with climate severity and foraging resource availability (e.g. temperature in north, dryness in south, and NDVI in middle). Regional pattern of herbaceous biodiversity depends on both climate and disturbance (i.e. fire and grazing) gradients but the livestock grazing effect appeared localized normally within 1.5 km from livestock shelter or wells. At a local-scale (i.e. family level smaller than 100 km2), species composition seems to provide useful indicator of grazing pressure, while climate and fire disturbance determined regional pattern of vegetation biodiversity. The results provide a useful premise to devise a satellite-based assessment tool for foraging resource availability and biological regime shift by grazing and climate change in future study.

Long Term Decline in Eastern US Winter Temperature Extremes.

NASA Astrophysics Data System (ADS)

Trenary, L. L.; DelSole, T. M.; Tippett, M. K.; Doty, B.

2016-12-01

States along the US eastern seaboard have experienced successively harsh winter conditions in recent years. This has prompted speculation that climate change is leading to more extreme winter conditions. In this study we quantify changes in the observed winter extremes over the period 1950-2015, by examining year-to-year differences in intensity, frequency and likelihood of daily cold temperature extremes in the north, mid, and south Atlantic states along the US east coast. Analyzing station data for these three regions, we find that while the north and mid-Atlantic regions experienced record-breaking cold temperatures in 2015, there is no long-term increase in the intensity of cold extremes anywhere along the eastern seaboard. Likewise, despite the record number of cold days in these two regions during 2014 and 2015, there is no systematic increase in the frequency of cold extremes. To determine whether the observed changes are natural or human-forced, we repeat our analysis using a suite of climate simulations, with and without external forcing. Generally, model simulations suggest that human-induced forcing does not significantly influence the range of daily winter temperature. Combining this result with the fact that the observed winter temperatures are becoming warmer and less variable, we conclude that the recent intensification of eastern US cold extremes is only temporary.

Geographic variation in winter adaptations of snowshoe hares (Lepus americanus)

USGS Publications Warehouse

Gigliotti, Laura C.; Diefenbach, Duane R.; Sheriff, M.J.

2017-01-01

Understanding adaptations of nonhibernating northern endotherms to cope with extreme cold is important because climate-induced changes in winter temperatures and snow cover are predicted to impact these species the most. We compared winter pelage characteristics and heat production of snowshoe hares (Lepus americanus Erxleben, 1777) on the southern edge of their range, in Pennsylvania (USA), to a northern population, in the Yukon (Canada), to investigate how hares might respond to changing environmental conditions. We also investigated how hares in Pennsylvania altered movement rates and resting spot selection to cope with variable winter temperatures. Hares from Pennsylvania had shorter, less dense, and less white winter coats than their northern counterparts, suggesting lower coat insulation. Hares in the southern population had lower pelage temperatures, indicating that they produced less heat than those in the northern population. In addition, hares in Pennsylvania did not select for resting spots that offered thermal advantages, but selected locations offering visual obstruction from predators. Movement rates were associated with ambient temperature, with the smallest movements occurring at the lower and upper range of observed ambient temperatures. Our results indicate that snowshoe hares may be able to adapt to future climate conditions via changes in pelage characteristics, metabolism, and behavior.

Impact of Climate Change on Food Security in Kenya

NASA Astrophysics Data System (ADS)

Yator, J. J.

2016-12-01

This study sought to address the existing gap on the impact of climate change on food security in support of policy measures to avert famine catastrophes. Fixed and random effects regressions for crop food security were estimated. The study simulated the expected impact of future climate change on food insecurity based on the Representative Concentration Pathways scenario (RCPs). The study makes use of county-level yields estimates (beans, maize, millet and sorghum) and daily climate data (1971 to 2010). Climate variability affects food security irrespective of how food security is defined. Rainfall during October-November-December (OND), as well as during March-April-May (MAM) exhibit an inverted U-shaped relationship with most food crops; the effects are most pronounced for maize and sorghum. Beans and Millet are found to be largely unresponsive to climate variability and also to time-invariant factors. OND rains and fall and summer temperature exhibit a U-shaped relationship with yields for most crops, while MAM rains temperature exhibits an inverted U-shaped relationship. However, winter temperatures exhibit a hill-shaped relationship with most crops. Project future climate change scenarios on crop productivity show that climate change will adversely affect food security, with up to 69% decline in yields by the year 2100. Climate variables have a non-linear relationship with food insecurity. Temperature exhibits an inverted U-shaped relationship with food insecurity, suggesting that increased temperatures will increase crop food insecurity. However, maize and millet, benefit from increased summer and winter temperatures. The simulated effects of different climate change scenarios on food insecurity suggest that adverse climate change will increase food insecurity in Kenya. The largest increases in food insecurity are predicted for the RCP 8.5Wm2, compared to RCP 4.5Wm2. Climate change is likely to have the greatest effects on maize insecurity, which is likely to increase by between 8.56% and 21% by the year 2100. There exists a need for policies that safeguard agriculture against the adverse effects of climate change to alleviate food insecurity in Kenya. Therefore, it is important that climate change mitigation is given much more priority in policy planning and also implementation.

Temporal variability in the importance of hydrologic, biotic, and climatic descriptors of dissolved oxygen dynamics in a shallow tidal-marsh creek

NASA Astrophysics Data System (ADS)

Nelson, N.; Munoz-Carpena, R.; Neale, P.; Tzortziou, M.; Megonigal, P.

2017-12-01

Due to strong abiotic forcing, dissolved oxygen (DO) in shallow tidal creeks often disobeys the conventional explanation of general aquatic DO cycling as biologically-regulated. In the present work, we seek to quantify the relative importance of abiotic (hydrologic and climatic), and biotic (primary productivity as represented by chlorophyll-a) descriptors of tidal creek DO. By fitting multiple linear regression models of DO to hourly chlorophyll-a, water quality, hydrology, and weather data collected in a tidal creek of a Chesapeake Bay marsh (Maryland, USA), temporal shifts (summer - early winter) in the relative importance of tidal creek DO descriptors were uncovered. Moreover, this analysis identified an alternative approach to evaluating tidal stage as a driver of DO by dividing stage into two DO-relevant variables: stage above and below bankfull depth. Within the hydrologic variable class, stage below bankfull depth dominated as an important descriptor, thus highlighting the role of pore water drainage and mixing as influential processes forcing tidal creek DO. Study findings suggest that tidal creek DO dynamics are explained by a balance of hydrologic, climatic, and biotic descriptors during warmer seasons due to many of these variables (i.e., chlorophyll-a, water temperature) acting as tracers of estuarine-marsh water mixing; conversely, in early winter months when estuarine and marsh waters differ less distinctly, hydrologic variables increase in relative importance as descriptors of tidal creek DO. These findings underline important distinctions in the underlying mechanisms dictating DO variability in shallow tidal marsh-creek environments relative to open water estuarine systems.

Temporal variability in the importance of hydrologic, biotic, and climatic descriptors of dissolved oxygen dynamics in a shallow tidal-marsh creek

NASA Astrophysics Data System (ADS)

Nelson, Natalie G.; Muñoz-Carpena, Rafael; Neale, Patrick J.; Tzortziou, Maria; Megonigal, J. Patrick

2017-08-01

Due to strong abiotic forcing, dissolved oxygen (DO) in shallow tidal creeks often disobeys the conventional explanation of general aquatic DO cycling as biologically regulated. In the present work, we seek to quantify the relative importance of abiotic (hydrologic and climatic), and biotic (primary productivity as represented by chlorophyll-a) descriptors of tidal creek DO. By fitting multiple linear regression models of DO to hourly chlorophyll-a, water quality, hydrology, and weather data collected in a tidal creek of a Chesapeake Bay marsh (Maryland, USA), temporal shifts (summer-early winter) in the relative importance of tidal creek DO descriptors were uncovered. Moreover, this analysis identified an alternative approach to evaluating tidal stage as a driver of DO by dividing stage into two DO-relevant variables: stage above and below bankfull depth. Within the hydrologic variable class, stage below bankfull depth dominated as an important descriptor, thus highlighting the role of pore water drainage and mixing as influential processes forcing tidal creek DO. Study findings suggest that tidal creek DO dynamics are explained by a balance of hydrologic, climatic, and biotic descriptors during warmer seasons due to many of these variables (i.e., chlorophyll-a, water temperature) acting as tracers of estuarine-marsh water mixing; conversely, in early winter months when estuarine and marsh waters differ less distinctly, hydrologic variables increase in relative importance as descriptors of tidal creek DO. These findings underline important distinctions in the underlying mechanisms dictating DO variability in shallow tidal marsh-creek environments relative to open water estuarine systems.

Pollen-based continental climate reconstructions at 6 and 21 ka: A global synthesis

USGS Publications Warehouse

Bartlein, P.J.; Harrison, S.P.; Brewer, Sandra; Connor, S.; Davis, B.A.S.; Gajewski, K.; Guiot, J.; Harrison-Prentice, T. I.; Henderson, A.; Peyron, O.; Prentice, I.C.; Scholze, M.; Seppa, H.; Shuman, B.; Sugita, S.; Thompson, R.S.; Viau, A.E.; Williams, J.; Wu, H.

2011-01-01

Subfossil pollen and plant macrofossil data derived from 14C-dated sediment profiles can provide quantitative information on glacial and interglacial climates. The data allow climate variables related to growing-season warmth, winter cold, and plant-available moisture to be reconstructed. Continental-scale reconstructions have been made for the mid-Holocene (MH, around 6 ka) and Last Glacial Maximum (LGM, around 21 ka), allowing comparison with palaeoclimate simulations currently being carried out as part of the fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change. The synthesis of the available MH and LGM climate reconstructions and their uncertainties, obtained using modern-analogue, regression and model-inversion techniques, is presented for four temperature variables and two moisture variables. Reconstructions of the same variables based on surface-pollen assemblages are shown to be accurate and unbiased. Reconstructed LGM and MH climate anomaly patterns are coherent, consistent between variables, and robust with respect to the choice of technique. They support a conceptual model of the controls of Late Quaternary climate change whereby the first-order effects of orbital variations and greenhouse forcing on the seasonal cycle of temperature are predictably modified by responses of the atmospheric circulation and surface energy balance. ?? 2010 The Author(s).

Influence of finite-time Lyapunov exponents on winter precipitation over the Iberian Peninsula

NASA Astrophysics Data System (ADS)

Garaboa-Paz, Daniel; Lorenzo, Nieves; Pérez-Muñuzuri, Vicente

2017-05-01

Seasonal forecasts have improved during the last decades, mostly due to an increase in understanding of the coupled ocean-atmosphere dynamics, and the development of models able to predict the atmosphere variability. Correlations between different teleconnection patterns and severe weather in different parts of the world are constantly evolving and changing. This paper evaluates the connection between winter precipitation over the Iberian Peninsula and the large-scale tropospheric mixing over the eastern Atlantic Ocean. Finite-time Lyapunov exponents (FTLEs) have been calculated from 1979 to 2008 to evaluate this mixing. Our study suggests that significant negative correlations exist between summer FTLE anomalies and winter precipitation over Portugal and Spain. To understand the mechanisms behind this correlation, summer anomalies of the FTLE have also been correlated with other climatic variables such as the sea surface temperature (SST), the sea level pressure (SLP) or the geopotential. The East Atlantic (EA) teleconnection index correlates with the summer FTLE anomalies, confirming their role as a seasonal predictor for winter precipitation over the Iberian Peninsula.

West Pacific Forcing of Atmospheric River Events in the North Pacific and the End of California's Recent Drought

NASA Astrophysics Data System (ADS)

Mitchell, J.; Ding, Q.

2017-12-01

The prolonged drought in California has by now largely subsided due to the large number of land-falling atmospheric rivers in the 2016-2017 winter season. Here we explore intraseasonal, interannual and decadal variabilities in winter AR activity along the California coast, especially in Southern California, with a special focus on the leading modes of covariance between tropical SSTs and the 200-hPa geopotential height in the Northern Hemisphere and an understanding of how the tropical related teleconnections modulate the AR activity in the North Pacific. This new approach explores a path towards improved intra-seasonal to seasonal predictions of climate variability in Southern California and may help explain how the most recent winter, which is not the anomalously strong el Niño as that in the last winter, brought California out of drought. Finally, we will suggest a way forward to better understand the causes of the recent drought over Southern California and how we may improve projections of its future change.

Resilience, rapid transitions and regime shifts: fingerprinting the responses of Lake Żabińskie (NE Poland) to climate variability and human disturbance since 1000 AD

NASA Astrophysics Data System (ADS)

Tylmann, Wojciech; Hernández-Almeida, Iván; Grosjean, Martin; José Gómez Navarro, Juan; Larocque-Tobler, Isabelle; Bonk, Alicja; Enters, Dirk; Ustrzycka, Alicja; Piotrowska, Natalia; Przybylak, Rajmund; Wacnik, Agnieszka; Witak, Małgorzata

2016-04-01

Rapid ecosystem transitions and adverse effects on ecosystem services as responses to combined climate and human impacts are of major concern. Yet few quantitative observational data exist, particularly for ecosystems that have a long history of human intervention. Here, we combine quantitative summer and winter climate reconstructions, climate model simulations and proxies for three major environmental pressures (land use, nutrients and erosion) to explore the system dynamics, resilience, and the role of disturbance regimes in varved eutrophic Lake Żabińskie since AD 1000. Comparison between regional and global climate simulations and quantitative climate reconstructions indicate that proxy data capture noticeably natural forced climate variability, while internal variability appears as the dominant source of climate variability in the climate model simulations during most parts of the last millennium. Using different multivariate analyses and change point detection techniques, we identify ecosystem changes through time and shifts between rather stable states and highly variable ones, as expressed by the proxies for land-use, erosion and productivity in the lake. Prior to AD 1600, the lake ecosystem was characterized by a high stability and resilience against considerable observed natural climate variability. In contrast, lake-ecosystem conditions started to fluctuate at high frequency across a broad range of states after AD 1600. The period AD 1748-1868 represents the phase with the strongest human disturbance of the ecosystem. Analyses of the frequency of change points in the multi-proxy dataset suggests that the last 400 years were highly variable and flickering with increasing vulnerability of the ecosystem to the combined effects of climate variability and anthropogenic disturbances. This led to significant rapid ecosystem transformations.

Assessment of mid-latitude atmospheric variability in CMIP5 models using a process oriented-metric

NASA Astrophysics Data System (ADS)

Di Biagio, Valeria; Calmanti, Sandro; Dell'Aquila, Alessandro; Ruti, Paolo

2013-04-01

We compare, for the period 1962-2000, an estimate of the northern hemisphere mid-latitude winter atmospheric variability according several global climate models included in the fifth phase of the Climate Model Intercomparison Project (CMIP5) with the results of the models belonging to the previous CMIP3 and with the NCEP-NCAR reanalysis. We use the space-time Hayashi spectra of the 500hPa geopotential height fields to characterize the variability of atmospheric circulation regimes and we introduce an ad hoc integral measure of the variability observed in the Northern Hemisphere on different spectral sub-domains. The overall performance of each model is evaluated by considering the total wave variability as a global scalar measure of the statistical properties of different types of atmospheric disturbances. The variability associated to eastward propagating baroclinic waves and to planetary waves is instead used to describe the performance of each model in terms of specific physical processes. We find that the two model ensembles (CMIP3 and CMIP5) do not show substantial differences in the description of northern hemisphere winter mid-latitude atmospheric variability, although some CMIP5 models display performances superior to their previous versions implemented in CMIP3. Preliminary results for the 21th century RCP 4.5 scenario will be also discussed for the CMIP5 models.

Evaluation of reanalysis datasets against observational soil temperature data over China

NASA Astrophysics Data System (ADS)

Yang, Kai; Zhang, Jingyong

2018-01-01

Soil temperature is a key land surface variable, and is a potential predictor for seasonal climate anomalies and extremes. Using observational soil temperature data in China for 1981-2005, we evaluate four reanalysis datasets, the land surface reanalysis of the European Centre for Medium-Range Weather Forecasts (ERA-Interim/Land), the second modern-era retrospective analysis for research and applications (MERRA-2), the National Center for Environmental Prediction Climate Forecast System Reanalysis (NCEP-CFSR), and version 2 of the Global Land Data Assimilation System (GLDAS-2.0), with a focus on 40 cm soil layer. The results show that reanalysis data can mainly reproduce the spatial distributions of soil temperature in summer and winter, especially over the east of China, but generally underestimate their magnitudes. Owing to the influence of precipitation on soil temperature, the four datasets perform better in winter than in summer. The ERA-Interim/Land and GLDAS-2.0 produce spatial characteristics of the climatological mean that are similar to observations. The interannual variability of soil temperature is well reproduced by the ERA-Interim/Land dataset in summer and by the CFSR dataset in winter. The linear trend of soil temperature in summer is well rebuilt by reanalysis datasets. We demonstrate that soil heat fluxes in April-June and in winter are highly correlated with the soil temperature in summer and winter, respectively. Different estimations of surface energy balance components can contribute to different behaviors in reanalysis products in terms of estimating soil temperature. In addition, reanalysis datasets can mainly rebuild the northwest-southeast gradient of soil temperature memory over China.

Winter climatic condictions in Andalusia (southern Spain) during the Dalton Minimum from documentary sources.

NASA Astrophysics Data System (ADS)

Rodrigo, Fernando S.

2010-05-01

In this work, a reconstruction of winter rainfall and temperature in Andalusia (southern Iberia Peninsula) during the period 1750-1850 is presented. The reconstruction is based on the analysis of a wide variety of documentary data. This period is interesting because it is characterized by a minimum in the solar irradiance (Dalton Minimum, around 1800), as well as intense volcanic activity (for instance, the eruption of the Tambora in 1815), when the increasing atmospheric CO2 concentrations were of minor importance. The reconstruction methodology is based on accounting the number of extreme events in past, and inferring mean value and standard deviation using the assumption of normal distribution for the climate variables. Results are compared with the behaviour of regional series for the reference period 1960-1990. The comparison of the distribution functions corresponding to 1790-1820 and 1960-1990 periods indicates that during the Dalton Minimum the frequency of droughts and warm winters was lesser than during the reference period, while the frequencies of wet and cold winters were similar. Future research work is outlined.

Effect of Climate Change on Mediterranean Winter Ranges of Two Migratory Passerines

PubMed Central

Tellería, José L.; Fernández-López, Javier; Fandos, Guillermo

2016-01-01

We studied the effect of climate change on the distribution of two insectivorous passerines (the meadow pipit Anthus pratensis and the chiffchaff Phylloscopus collybita) in wintering grounds of the Western Mediterranean basin. In this region, precipitation and temperature can affect the distribution of these birds through direct (thermoregulation costs) or indirect effects (primary productivity). Thus, it can be postulated that projected climate changes in the region will affect the extent and suitability of their wintering grounds. We studied pipit and chiffchaff abundance in several hundred localities along a belt crossing Spain and Morocco and assessed the effects of climate and other geographical and habitat predictors on bird distribution. Multivariate analyses reported a positive effect of temperature on the present distribution of the two species, with an additional effect of precipitation on the meadow pipit. These climate variables were used with Maxent to model the occurrence probabilities of species using ring recoveries as presence data. Abundance and occupancy of the two species in the study localities adjusted to the distribution models, with more birds in sectors of high climate suitability. After validation, these models were used to forecast the distribution of climate suitability according to climate projections for 2050–2070 (temperature increase and precipitation reduction). Results show an expansion of climatically suitable sectors into the highlands by the effect of warming on the two species, and a retreat of the meadow pipit from southern sectors related to rain reduction. The predicted patterns show a mean increase in climate suitability for the two species due to the warming of the large highland expanses typical of the western Mediterranean. PMID:26761791

The Predicted Influence of Climate Change on Lesser Prairie-Chicken Reproductive Parameters

PubMed Central

Grisham, Blake A.; Boal, Clint W.; Haukos, David A.; Davis, Dawn M.; Boydston, Kathy K.; Dixon, Charles; Heck, Willard R.

2013-01-01

The Southern High Plains is anticipated to experience significant changes in temperature and precipitation due to climate change. These changes may influence the lesser prairie-chicken (Tympanuchus pallidicinctus) in positive or negative ways. We assessed the potential changes in clutch size, incubation start date, and nest survival for lesser prairie-chickens for the years 2050 and 2080 based on modeled predictions of climate change and reproductive data for lesser prairie-chickens from 2001–2011 on the Southern High Plains of Texas and New Mexico. We developed 9 a priori models to assess the relationship between reproductive parameters and biologically relevant weather conditions. We selected weather variable(s) with the most model support and then obtained future predicted values from climatewizard.org. We conducted 1,000 simulations using each reproductive parameter’s linear equation obtained from regression calculations, and the future predicted value for each weather variable to predict future reproductive parameter values for lesser prairie-chickens. There was a high degree of model uncertainty for each reproductive value. Winter temperature had the greatest effect size for all three parameters, suggesting a negative relationship between above-average winter temperature and reproductive output. The above-average winter temperatures are correlated to La Niña events, which negatively affect lesser prairie-chickens through resulting drought conditions. By 2050 and 2080, nest survival was predicted to be below levels considered viable for population persistence; however, our assessment did not consider annual survival of adults, chick survival, or the positive benefit of habitat management and conservation, which may ultimately offset the potentially negative effect of drought on nest survival. PMID:23874549

Quantification of spatial temporal variability of snow cover and hydro-climatic variables based on multi-source remote sensing data in the Swat watershed, Hindukush Mountains, Pakistan

NASA Astrophysics Data System (ADS)

Anjum, Muhammad Naveed; Ding, Yongjian; Shangguan, Donghui; Liu, Junguo; Ahmad, Ijaz; Ijaz, Muhammad Wajid; Khan, Muhammad Imran

2018-02-01

The northern part of Hindukush Mountains has a perplexing environment due to the influence of adjacent mountains of Himalaya, Karakoram, and Tibetan Plateau. Although reliable evidences of climate change are available; however, a clear knowledge of snow cover dynamics in the context of climate change is missing for this region. In this study, we used various remotely sensed (TRMM precipitation product, while MODIS temperature and snow cover products) and gauge-based datasets to quantify the spatiotemporal variability of climatic variables and their turn effects over the snow cover area (SCA) and river discharge in the Swat watershed, northern Hindukush Mountains, Pakistan. The Mann-Kendall method and Sen's slope estimator were used to estimate the trends in SCA and hydro-climatic variables, at 5% significant level (P = 0.05). Results show that the winter and springs temperatures have increased (at the rate of 0.079 and 0.059 °C year-1, respectively), while decreasing in the summer and autumn (at the rate of 0.049 and 0.070 °C year-1, respectively). Basin-wide increasing tendency of precipitation was identified with a highest increasing rate of 3.563 mm year-1 in the spring season. A decreasing trend in the winter SCA (at the rate of -0.275% year-1) and increasing trends in other seasons were identified. An increasing tendency of river discharge on annual and seasonal scales was also witnessed. The seasonal variations in discharge showed significant positive and negative relationships with temperature and SCA, respectively. We conclude that the future variations in the temperature and SCA in the higher altitudes of the Swat watershed could substantially affect the seasonality of the river discharge. Moreover, it implies that the effect of ongoing global warming on the SCA in the snowmelt-dominated river basins needs to be considered for sustainable regional planning and management of water resources, hydropower production, and downstream irrigation scheduling.

A 13,500 Year Record of Holocene Climate, Fire and Vegetation from Swan Lake, Idaho, USA

NASA Astrophysics Data System (ADS)

Wahl, D.; Anderson, L.; Miller, D. M.; Rosario, J. J.; Starratt, S.; McGeehin, J. P.; Bright, J. E.

2015-12-01

Modern climate dynamics in the western US are largely determined by a combination of two factors: 1) the strength and position of midlatitude pressure systems, which, in turn, are responsible for the generation and trajectory of winter storms, and 2) the strength of the North America Monsoon (NAM) which brings summer precipitation northward in response to northern hemisphere warming. Paleoclimate records from the Great Basin of the western US suggest some coherence in the timing of major climatic shifts during the Holocene. However, knowledge of the timing and magnitude of these changes at local scales, which can help explain the relative contribution of midlatitude winter storms vs. NAM, is lacking in many places. Here we present new data that constrain the timing and magnitude of late glacial and Holocene climate variability in the northeastern Great Basin, provide insight into past spatial variability of precipitation patterns in the western US, and improve our understanding of regional scale influences on Great Basin climate. In 2011, a 7.65 m sediment core was raised from Swan Lake, a small wetland located in southeastern Idaho that was formed in the spillway channel created by the catastrophic flooding of Lake Bonneville ~18 ka BP. Pollen, charcoal, clumped isotope, diatom, ostracod, and sedimentological data are used to reconstruct vegetation, fire history, and lake level/groundwater flux over the last 13,500 years. Age control is provided by 19 AMS radiocarbon determinations, which are reported as thousands of calibrated years before present (ka BP). This effort builds on earlier work by Bright (1966) who reported on pollen, macrofossils, and sediment type from Swan Lake. Our data suggest cool and wet conditions prevailed until around 12.3 ka BP, after which a drying trend begins. The early Holocene was marked by a warmer, drier climate, which persisted until around 6.2 ka BP. Moister conditions after 6.2 ka BP likely resulted from a combination of enhanced NAM and increased winter storm activity. The period from 4.6-1.1 ka BP is characterized by increased variability, although it appears to have been relatively dry compared to the preceding two millennia. Data suggest that climate in the area was relatively wet from 1.1 ka BP to the present.

Two centuries of observed atmospheric variability and change over the North Sea region

NASA Astrophysics Data System (ADS)

Stendel, Martin; van den Besselaar, Else; Hannachi, Abdel; Kent, Elizabeth; Lefebvre, Christiana; van Oldenborgh, Geert Jan; Rosenhagen, Gudrun; Schenk, Frederik; van der Schrier, Gerard

2015-04-01

Situated in northwestern Europe, the North Sea region is under influence of air masses from subtropical to arctic origin, and thus exhibits significant natural climate variability. As the land areas surrounding the North Sea are densely populated, climate change is an important issue in terms of e.g. coastal protection, fishery and trade. This study is part of the NOSCCA initiative (North Sea Region Climate Change Assessment) and presents observed variability and changes in atmospheric parameters during the last roughly 200 years. Circulation patterns show considerable decadal variability. In recent decades, a northward shift of storm tracks and increased cyclonic activity has been observed. There is also an indication of increased persistence of weather types. The wind climate is dominated by large multidecadal variability, and no robust long-term trends can be identified in the available datasets. There is a clear positive trend in near-surface temperatures, in particular during spring and winter. Over the region as a whole, no clear long-term precipitation trends are visible, although regional indications exist for an increased risk of extreme precipitation events.

The Extremely Warm Early Winter 2000 in Europe: What is the Forcing

NASA Technical Reports Server (NTRS)

Otterman, J.; Angell, J. K.; Atlas, R.; Ardizzone, J.; Demaree, G.; Jusem, J. C.; Koslowsky, D.; Terry, J.; Einaudi, Franco (Technical Monitor)

2001-01-01

High variability characterizes the winter climate of central Europe: interannual fluctuations in the surface-air temperature as large as 18 C over large areas are fairly common. The extraordinary early-winter 2000 in Europe appears to be a departure to an unprecedented extreme of the existing climate patterns. Such anomalous events affect agriculture, forestry, fuel consumption, etc., and thus deserve in-depth analysis. Our analysis indicates that the high anomalies of the surface-air temperature are predominantly due to the southwesterly flow from the eastern North Atlantic, with a weak contribution by southerly flow from the western Mediterranean. Backward trajectories based on the SSM/I and NCEP Reanalysis datasets traced from west-central Europe indicate that the warm air masses flowing into Europe originate in the southern North Atlantic, where the surface-air temperatures exceed by 15c or more the climatic norms in Europe for late-November or early-December. Because such large ocean-to-continent temperature differences characterize the winter conditions, we refer to this episode which started in late November as occurring in the early winter. In this season, with the sun low over the horizon in Europe, absorption of insolation by the surface has little significance. The effect of cloudiness, a corollary to the low-level maritime-air advection, is a warming by a reduction of heat loss (greenhouse effect). In contrast, in the summer, clouds, by reducing absorption of insolation, produce a cooling, effect at the surface.

Demographic consequences of increased winter births in a large aseasonally breeding mammal (Bos taurus) in response to climate change.

PubMed

Burthe, Sarah; Butler, Adam; Searle, Kate R; Hall, Stephen J G; Thackeray, Stephen J; Wanless, Sarah

2011-11-01

1. Studies examining changes in the scheduling of breeding in response to climate change have focused on species with well-defined breeding seasons. Species exhibiting year-round breeding have received little attention and the magnitudes of any responses are unknown. 2. We investigated phenological data for an enclosed feral population of cattle (Bos taurus L.) in northern England exhibiting year-round breeding. This population is relatively free of human interference. 3. We assessed whether the timing of births had changed over the last 60 years, in response to increasing winter and spring temperatures, changes in herd density, and a regime of lime fertilisation. 4. Median birth date became earlier by 1·0 days per year. Analyses of the seasonal distribution of calving dates showed that significantly fewer calves were born in summer (decline from 44% of total births to 20%) and significantly more in winter (increase from 12% to 30%) over the study period. The most pronounced changes occurred in winter, with significant increases in both the proportion and number of births. Winter births arise from conceptions in the previous spring, and we considered models that investigated climate and weather variables associated with the winter preceding and the spring of conceptions. 5. The proportion of winter births was higher when the onset of the plant growing season was earlier during the spring of conceptions. This relationship was much weaker during years when the site had been fertilised with lime, suggesting that increased forage biomass was over-riding the impacts of changing plant phenology. When the onset of the growing season was late, winter births increased with female density. 6. Recruitment estimates from a stage-structured state-space population model were significantly negatively correlated with the proportion of births in the preceding winter, suggesting that calves born in winter are less likely to survive than those born in other seasons. 7. This is one of the first studies to document changes in the phenology of a year-round breeder, suggesting that the impact of climate on the scheduling of biological events may be more extensive than previously thought and that impacts may be negative, even for species with relatively flexible breeding strategies. © 2011 The Authors. Journal of Animal Ecology © 2011 British Ecological Society.

Chemistry and dynamics of the Arctic winter 2015/2016: Simulations with the Chemistry-Climate Model EMAC

NASA Astrophysics Data System (ADS)

Khosrawi, Farahnaz; Kirner, Ole; Sinnhuber, Bjoern-Martin; Ruhnke, Roland; Hoepfner, Michael; Woiwode, Wolfgang; Oelhaf, Hermann; Santee, Michelle L.; Manney, Gloria L.; Froidevaux, Lucien; Murtagh, Donal; Braesicke, Peter

2016-04-01

Model simulations of the Arctic winter 2015/2016 were performed with the atmospheric chemistry-climate model ECHAM5/MESSy Atmospheric Chemistry (EMAC) for the POLSTRACC (Polar Stratosphere in a Changing Climate) project. The POLSTRACC project is a HALO mission (High Altitude and LOng Range Research Aircraft) that aims to investigate the structure, composition and evolution of the Arctic Upper Troposphere Lower Stratosphere (UTLS) in a changing climate. Especially, the chemical and physical processes involved in Arctic stratospheric ozone depletion, transport and mixing processes in the UTLS at high latitudes, polar stratospheric clouds as well as cirrus clouds are investigated. The model simulations were performed with a resolution of T42L90, corresponding to a quadratic Gaussian grid of approximately 2.8°× 2.8° degrees in latitude and longitude, and 90 vertical layers from the surface up to 0.01 hPa (approx. 80 km). A Newtonian relaxation technique of the prognostic variables temperature, vorticity, divergence and surface pressure towards ECMWF data was applied above the boundary layer and below 10 hPa, in order to nudge the model dynamics towards the observed meteorology. During the Arctic winter 2015/2016 a stable vortex formed in early December, with a cold pool where temperatures reached below the Nitric Acid Trihydrate (NAT) existence temperature of 195 K, thus allowing Polar Stratospheric Clouds (PSCs) to form. The early winter has been exceptionally cold and satellite observations indicate that sedimenting PSC particles have lead to denitrification as well as dehydration of stratospheric layers. In this presentation an overview of the chemistry and dynamics of the Arctic winter 2015/2016 as simulated with EMAC will be given and comparisons to satellite observations such as e.g. Aura/MLS and Odin/SMR will be shown.

Impact of large-scale circulation changes in the North Atlantic sector on the current and future Mediterranean winter hydroclimate

NASA Astrophysics Data System (ADS)

Barcikowska, Monika J.; Kapnick, Sarah B.; Feser, Frauke

2018-03-01

The Mediterranean region, located in the transition zone between the dry subtropical and wet European mid-latitude climate, is very sensitive to changes in the global mean climate state. Projecting future changes of the Mediterranean hydroclimate under global warming therefore requires dynamic climate models to reproduce the main mechanisms controlling regional hydroclimate with sufficiently high resolution to realistically simulate climate extremes. To assess future winter precipitation changes in the Mediterranean region we use the Geophysical Fluid Dynamics Laboratory high-resolution general circulation model for control simulations with pre-industrial greenhouse gas and aerosol concentrations which are compared to future scenario simulations. Here we show that the coupled model is able to reliably simulate the large-scale winter circulation, including the North Atlantic Oscillation and Eastern Atlantic patterns of variability, and its associated impacts on the mean Mediterranean hydroclimate. The model also realistically reproduces the regional features of daily heavy rainfall, which are absent in lower-resolution simulations. A five-member future projection ensemble, which assumes comparatively high greenhouse gas emissions (RCP8.5) until 2100, indicates a strong winter decline in Mediterranean precipitation for the coming decades. Consistent with dynamical and thermodynamical consequences of a warming atmosphere, derived changes feature a distinct bipolar behavior, i.e. wetting in the north—and drying in the south. Changes are most pronounced over the northwest African coast, where the projected winter precipitation decline reaches 40% of present values. Despite a decrease in mean precipitation, heavy rainfall indices show drastic increases across most of the Mediterranean, except the North African coast, which is under the strong influence of the cold Canary Current.

Climate change impacts on potential recruitment in an ecosystem engineer

PubMed Central

Morgan, Emer; O' Riordan, Ruth M; Culloty, Sarah C

2013-01-01

Climate variability and the rapid warming of seas undoubtedly have huge ramifications for biological processes such as reproduction. As such, gametogenesis and spawning were investigated at two sites over 200 km apart on the south coast of Ireland in an ecosystem engineer, the common cockle, Cerastoderma edule. Both sites are classed as Special Areas of Conservation (SACs), but are of different water quality. Cerastoderma edule plays a significant biological role by recycling nutrients and affecting sediment structure, with impacts upon assemblage biomass and functional diversity. It plays a key role in food webs, being a common foodstuff for a number of marine birds including the oystercatcher. Both before and during the study (early 2010–mid 2011), Ireland experienced its two coldest winters for 50 years. As the research demonstrated only slight variation in the spawning period between sites, despite site differences in water and environmental quality, temperature and variable climatic conditions were the dominant factor controlling gametogenesis. The most significant finding was that the spawning period in the cockle extended over a greater number of months compared with previous studies and that gametogenesis commenced over winter rather than in spring. Extremely cold winters may impact on the cockle by accelerating and extending the onset and development of gametogenesis. Whether this impact is positive or negative would depend on the associated events occurring on which the cockle depends, that is, presence of primary producers and spring blooms, which would facilitate conversion of this extended gametogenesis into successful recruitment. PMID:23532482

Influence of climate variability on acute myocardial infarction mortality in Havana, 2001-2012.

PubMed

Rivero, Alina; Bolufé, Javier; Ortiz, Paulo L; Rodríguez, Yunisleydi; Reyes, María C

2015-04-01

Death from acute myocardial infarction is due to many factors; influences on risk to the individual include habits, lifestyle and behavior, as well as weather, climate and other environmental components. Changing climate patterns make it especially important to understand how climatic variability may influence acute myocardial infarction mortality. Describe the relationship between climate variability and acute myocardial infarction mortality during the period 2001-2012 in Havana. An ecological time-series study was conducted. The universe comprised 23,744 deaths from acute myocardial infarction (ICD-10: I21-I22) in Havana residents from 2001 to 2012. Climate variability and seasonal anomalies were described using the Bultó-1 bioclimatic index (comprising variables of temperature, humidity, precipitation, and atmospheric pressure), along with series analysis to determine different seasonal-to-interannual climate variation signals. The role played by climate variables in acute myocardial infarction mortality was determined using factor analysis. The Mann-Kendall and Pettitt statistical tests were used for trend analysis with a significance level of 5%. The strong association between climate variability conditions described using the Bultó-1 bioclimatic index and acute myocardial infarctions accounts for the marked seasonal pattern in AMI mortality. The highest mortality rate occurred during the dry season, i.e., the winter months in Cuba (November-April), with peak numbers in January, December and March. The lowest mortality coincided with the rainy season, i.e., the summer months (May-October). A downward trend in total number of deaths can be seen starting with the change point in April 2009. Climate variability is inversely associated with an increase in acute myocardial infarction mortality as is shown by the Bultó-1 index. This inverse relationship accounts for acute myocardial infarction mortality's seasonal pattern.

Estimating inter-annual variability in winter wheat sowing dates from satellite time series in Camargue, France

NASA Astrophysics Data System (ADS)

Manfron, Giacinto; Delmotte, Sylvestre; Busetto, Lorenzo; Hossard, Laure; Ranghetti, Luigi; Brivio, Pietro Alessandro; Boschetti, Mirco

2017-05-01

Crop simulation models are commonly used to forecast the performance of cropping systems under different hypotheses of change. Their use on a regional scale is generally constrained, however, by a lack of information on the spatial and temporal variability of environment-related input variables (e.g., soil) and agricultural practices (e.g., sowing dates) that influence crop yields. Satellite remote sensing data can shed light on such variability by providing timely information on crop dynamics and conditions over large areas. This paper proposes a method for analyzing time series of MODIS satellite data in order to estimate the inter-annual variability of winter wheat sowing dates. A rule-based method was developed to automatically identify a reliable sample of winter wheat field time series, and to infer the corresponding sowing dates. The method was designed for a case study in the Camargue region (France), where winter wheat is characterized by vernalization, as in other temperate regions. The detection criteria were chosen on the grounds of agronomic expertise and by analyzing high-confidence time-series vegetation index profiles for winter wheat. This automatic method identified the target crop on more than 56% (four-year average) of the cultivated areas, with low commission errors (11%). It also captured the seasonal variability in sowing dates with errors of ±8 and ±16 days in 46% and 66% of cases, respectively. Extending the analysis to the years 2002-2012 showed that sowing in the Camargue was usually done on or around November 1st (±4 days). Comparing inter-annual sowing date variability with the main local agro-climatic drivers showed that the type of preceding crop and the weather conditions during the summer season before the wheat sowing had a prominent role in influencing winter wheat sowing dates.

Interannual drivers of the seasonal cycle of CO2 in the Southern Ocean

NASA Astrophysics Data System (ADS)

Gregor, Luke; Kok, Schalk; Monteiro, Pedro M. S.

2018-04-01

Resolving and understanding the drivers of variability of CO2 in the Southern Ocean and its potential climate feedback is one of the major scientific challenges of the ocean-climate community. Here we use a regional approach on empirical estimates of pCO2 to understand the role that seasonal variability has in long-term CO2 changes in the Southern Ocean. Machine learning has become the preferred empirical modelling tool to interpolate time- and location-restricted ship measurements of pCO2. In this study we use an ensemble of three machine-learning products: support vector regression (SVR) and random forest regression (RFR) from Gregor et al. (2017), and the self-organising-map feed-forward neural network (SOM-FFN) method from Landschützer et al. (2016). The interpolated estimates of ΔpCO2 are separated into nine regions in the Southern Ocean defined by basin (Indian, Pacific, and Atlantic) and biomes (as defined by Fay and McKinley, 2014a). The regional approach shows that, while there is good agreement in the overall trend of the products, there are periods and regions where the confidence in estimated ΔpCO2 is low due to disagreement between the products. The regional breakdown of the data highlighted the seasonal decoupling of the modes for summer and winter interannual variability. Winter interannual variability had a longer mode of variability compared to summer, which varied on a 4-6-year timescale. We separate the analysis of the ΔpCO2 and its drivers into summer and winter. We find that understanding the variability of ΔpCO2 and its drivers on shorter timescales is critical to resolving the long-term variability of ΔpCO2. Results show that ΔpCO2 is rarely driven by thermodynamics during winter, but rather by mixing and stratification due to the stronger correlation of ΔpCO2 variability with mixed layer depth. Summer pCO2 variability is consistent with chlorophyll a variability, where higher concentrations of chlorophyll a correspond with lower pCO2 concentrations. In regions of low chlorophyll a concentrations, wind stress and sea surface temperature emerged as stronger drivers of ΔpCO2. In summary we propose that sub-decadal variability is explained by summer drivers, while winter variability contributes to the long-term changes associated with the SAM. This approach is a useful framework to assess the drivers of ΔpCO2 but would greatly benefit from improved estimates of ΔpCO2 and a longer time series.

Sensitivity of bud burst in key tree species in the UK to recent climate variability and change

NASA Astrophysics Data System (ADS)

Abernethy, Rachel; Cook, Sally; Hemming, Deborah; McCarthy, Mark

2017-04-01

Analysing the relationship between the changing climate of the UK and the spatial and temporal distribution of spring bud burst plays an important role in understanding ecosystem functionality and predicting future phenological trends. The location and timing of bud burst of eleven species of trees alongside climatic factors such as, temperature, precipitation and hours of sunshine (photoperiod) were used to investigate: i. which species' bud burst timing experiences the greatest impact from a changing climate, ii. which climatic factor has the greatest influence on the timing of bud burst, and iii. whether the location of bud burst is influenced by climate variability. Winter heatwave duration was also analysed as part of an investigation into the relationship between temperature trends of a specific winter period and the following spring events. Geographic Information Systems (GIS) and statistical analysis tools were used to visualise spatial patterns and to analyse the phenological and climate data through regression and analysis of variance (ANOVA) tests. Where there were areas that showed a strong positive or negative relationship between phenology and climate, satellite imagery was used to calculate a Normalised Difference Vegetation Index (NDVI) and a Leaf Area Index (LAI) to further investigate the relationships found. It was expected that in the north of the UK, where bud burst tends to occur later in the year than in the south, that the bud bursts would begin to occur earlier due to increasing temperatures and increased hours of sunshine. However, initial results show that for some species, the bud burst timing tends to remain or become later in the year. Interesting results will be found when investigating the statistical significance between the changing location of the bud bursts and each climatic factor.

An 'Observational Large Ensemble' to compare observed and modeled temperature trend uncertainty due to internal variability.

NASA Astrophysics Data System (ADS)

Poppick, A. N.; McKinnon, K. A.; Dunn-Sigouin, E.; Deser, C.

2017-12-01

Initial condition climate model ensembles suggest that regional temperature trends can be highly variable on decadal timescales due to characteristics of internal climate variability. Accounting for trend uncertainty due to internal variability is therefore necessary to contextualize recent observed temperature changes. However, while the variability of trends in a climate model ensemble can be evaluated directly (as the spread across ensemble members), internal variability simulated by a climate model may be inconsistent with observations. Observation-based methods for assessing the role of internal variability on trend uncertainty are therefore required. Here, we use a statistical resampling approach to assess trend uncertainty due to internal variability in historical 50-year (1966-2015) winter near-surface air temperature trends over North America. We compare this estimate of trend uncertainty to simulated trend variability in the NCAR CESM1 Large Ensemble (LENS), finding that uncertainty in wintertime temperature trends over North America due to internal variability is largely overestimated by CESM1, on average by a factor of 32%. Our observation-based resampling approach is combined with the forced signal from LENS to produce an 'Observational Large Ensemble' (OLENS). The members of OLENS indicate a range of spatially coherent fields of temperature trends resulting from different sequences of internal variability consistent with observations. The smaller trend variability in OLENS suggests that uncertainty in the historical climate change signal in observations due to internal variability is less than suggested by LENS.

A methodological critique on using temperature-conditioned resampling for climate projections as in the paper of Gerstengarbe et al. (2013) winter storm- and summer thunderstorm-related loss events in Theoretical and Applied Climatology (TAC)

NASA Astrophysics Data System (ADS)

Wechsung, Frank; Wechsung, Maximilian

2016-11-01

The STatistical Analogue Resampling Scheme (STARS) statistical approach was recently used to project changes of climate variables in Germany corresponding to a supposed degree of warming. We show by theoretical and empirical analysis that STARS simply transforms interannual gradients between warmer and cooler seasons into climate trends. According to STARS projections, summers in Germany will inevitably become dryer and winters wetter under global warming. Due to the dominance of negative interannual correlations between precipitation and temperature during the year, STARS has a tendency to generate a net annual decrease in precipitation under mean German conditions. Furthermore, according to STARS, the annual level of global radiation would increase in Germany. STARS can be still used, e.g., for generating scenarios in vulnerability and uncertainty studies. However, it is not suitable as a climate downscaling tool to access risks following from changing climate for a finer than general circulation model (GCM) spatial scale.

Continuous and discrete extreme climatic events affecting the dynamics of a high-arctic reindeer population.

PubMed

Chan, Kung-Sik; Mysterud, Atle; Øritsland, Nils Are; Severinsen, Torbjørn; Stenseth, Nils Chr

2005-10-01

Climate at northern latitudes are currently changing both with regard to the mean and the temporal variability at any given site, increasing the frequency of extreme events such as cold and warm spells. Here we use a conceptually new modelling approach with two different dynamic terms of the climatic effects on a Svalbard reindeer population (the Brøggerhalvøya population) which underwent an extreme icing event ("locked pastures") with 80% reduction in population size during one winter (1993/94). One term captures the continuous and linear effect depending upon the Arctic Oscillation and another the discrete (rare) "event" process. The introduction of an "event" parameter describing the discrete extreme winter resulted in a more parsimonious model. Such an approach may be useful in strongly age-structured ungulate populations, with young and very old individuals being particularly prone to mortality factors during adverse conditions (resulting in a population structure that differs before and after extreme climatic events). A simulation study demonstrates that our approach is able to properly detect the ecological effects of such extreme climate events.

Come rain or shine: Multi-model Projections of Climate Hazards affecting Transportation in the South Central United States

NASA Astrophysics Data System (ADS)

Mullens, E.; Mcpherson, R. A.

2016-12-01

This work develops detailed trends in climate hazards affecting the Department of Transportation's Region 6, in the South Central U.S. Firstly, a survey was developed to gather information regarding weather and climate hazards in the region from the transportation community, identifying key phenomena and thresholds to evaluate. Statistically downscaled datasets were obtained from the Multivariate Adaptive Constructed Analogues (MACA) project, and the Asynchronous Regional Regression Model (ARRM), for a total of 21 model projections, two coupled model intercomparisons (CMIP3, and CMIP5), and four emissions pathways (A1Fi, B1, RCP8.5, RCP4.5). Specific hazards investigated include winter weather, freeze-thaw cycles, hot and cold extremes, and heavy precipitation. Projections for each of these variables were calculated for the region, utilizing spatial mapping, and time series analysis at the climate division level. The results indicate that cold-season phenomena such as winter weather, freeze-thaw, and cold extremes, decrease in intensity and frequency, particularly with the higher emissions pathways. Nonetheless, specific model and downscaling method yields variability in magnitudes, with the most notable decreasing trends late in the 21st century. Hot days show a pronounced increase, particularly with greater emissions, producing annual mean 100oF day frequencies by late 21st century analogous to the 2011 heatwave over the central Southern Plains. Heavy precipitation, evidenced by return period estimates and counts-over-thresholds, also show notable increasing trends, particularly between the recent past through mid-21st Century. Conversely, mean precipitation does not show significant trends and is regionally variable. Precipitation hazards (e.g., winter weather, extremes) diverge between downscaling methods and their associated model samples much more substantially than temperature, suggesting that the choice of global model and downscaled data is particularly important when considering region-specific impacts for precipitation. These results are intended to inform region transportation professionals of the susceptibility of the area to climate extremes, and to be a resource for assessing and incorporating changing risk probabilities into their planning processes.

Relating Regional Arctic Sea Ice and climate extremes over Europe

NASA Astrophysics Data System (ADS)

Ionita-Scholz, Monica; Grosfeld, Klaus; Lohmann, Gerrit; Scholz, Patrick

2016-04-01

The potential increase of temperature extremes under climate change is a major threat to society, as temperature extremes have a deep impact on environment, hydrology, agriculture, society and economy. Hence, the analysis of the mechanisms underlying their occurrence, including their relationships with the large-scale atmospheric circulation and sea ice concentration, is of major importance. At the same time, the decline in Arctic sea ice cover during the last 30 years has been widely documented and it is clear that this change is having profound impacts at regional as well as planetary scale. As such, this study aims to investigate the relation between the autumn regional sea ice concentration variability and cold winters in Europe, as identified by the numbers of cold nights (TN10p), cold days (TX10p), ice days (ID) and consecutive frost days (CFD). We analyze the relationship between Arctic sea ice variation in autumn (September-October-November) averaged over eight different Arctic regions (Barents/Kara Seas, Beaufort Sea, Chukchi/Bering Seas, Central Arctic, Greenland Sea, Labrador Sea/Baffin Bay, Laptev/East Siberian Seas and Northern Hemisphere) and variations in atmospheric circulation and climate extreme indices in the following winter season over Europe using composite map analysis. Based on the composite map analysis it is shown that the response of the winter extreme temperatures over Europe is highly correlated/connected to changes in Arctic sea ice variability. However, this signal is not symmetrical for the case of high and low sea ice years. Moreover, the response of temperatures extreme over Europe to sea ice variability over the different Arctic regions differs substantially. The regions which have the strongest impact on the extreme winter temperature over Europe are: Barents/Kara Seas, Beaufort Sea, Central Arctic and the Northern Hemisphere. For the years of high sea ice concentration in the Barents/Kara Seas there is a reduction in the number of cold nights, cold days, ice days and consecutive frost days over the western part of Europe. In the opposite case of low sea ice concentration over the Barents/Kara Seas an increase of up to 8 days/winter of cold nights and days is observed over the whole Europe and an increase of up to 4 days/winter in the number of ID and CFD is observed over the same regions. The cold winters over Europe (low sea ice years) are associated with anomalous anticyclone and the downstream development of a mid-latitude trough, which in turn favours the advection of cold air from the north, providing favourable conditions for severe winters over Europe. We suggest that these results can help to improve the seasonal predictions of winter extreme events over Europe. Due to the non-linear response to high vs. low sea ice years, the skill of the predictions might depend on the sign and amplitude of the anomalies.

Influence of the Scandinavian climate pattern on the UK asthma mortality: a time series and geospatial study.

PubMed

Majeed, Haris; Moore, G W K

2018-04-13

It is well known that climate variability and trends have an impact on human morbidity and mortality, especially during the winter. However, there are only a handful of studies that have undertaken quantitative investigations into this impact. We evaluate the association between the UK winter asthma mortality data to a well-established feature of the climate system, the Scandinavian (SCA) pattern. Time series analysis of monthly asthma mortality through the period of January 2001 to December 2015 was conducted, where the data were acquired from the UK's Office for National Statistics. The correlations between indices of important modes of climate variability impacting the UK such as the North Atlantic Oscillation as well as the SCA and the asthma mortality time series were computed. A grid point correlation analysis was also conducted with the asthma data with sea level pressure, surface wind and temperature data acquired from the European Centre for Medium-Range Weather Forecasts. We find that sea level pressure and temperature fluctuations associated with the SCA explain ~20% (>95% CL) of variance in the UK asthma mortality through a period of 2001-2015. Furthermore, the highest winter peak in asthma mortality occurred in the year 2015, during which there were strong northwesterly winds over the UK that were the result of a sea level pressure pattern similar to that associated with the SCA. Our study emphasises the importance of incorporating large-scale geospatial analyses into future research of understanding diseases and its environmental impact on human health. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Effect of climate variability and change on winter haze over eastern China in recent decades

NASA Astrophysics Data System (ADS)

Liao, Hong; Yang, Yang

2017-04-01

In recent years, eastern China has frequently experienced persistent and severe winter haze pollution episodes with high aerosol concentrations, which have affected half of the 1.3 billion people in China. In this work, the increases in wintertime aerosol concentrations and severe haze events in eastern China over 1985-2015 were quantified by using observed atmospheric visibility from the National Climatic Data Center Global Summary of Day database, observed PM2.5 concentrations from the network of China National Environmental Monitoring Centre (CNEMC), and simulated PM2.5 concentrations from the Goddard Earth-Observing System (GEOS) chemical transport model (GEOS-Chem). Observed winter haze days (defined as days with atmospheric visibility less than 10 km and relative humidity less than 80%) averaged over eastern China (105-122.5°E, 20-45°N) increased from 21 days in 1980 to 42 days in 2014. Observed severe haze days (defined as days with PM2.5 >150 μg m-3) occurred mainly over Northern China. Considering variations in both anthropogenic emissions and meteorological parameters, the GEOS-Chem model simulated an increasing trend in wintertime surface-layer PM2.5 concentrations of 10.5 (±6.2) μg m-3 decade-1 over eastern China in the past decades. Sensitivity studies showed that changes in anthropogenic emissions and in climate contributed 87% and 17% to this increasing trend, respectively. Wintertime severe haze events over eastern China showed large interannual variations, driven by climate variability. Process analyses were performed to identify the key meteorological parameters that determined the interannual variations of wintertime severe haze events.

Satellite view of seasonal greenness trends and controls in South Asia

NASA Astrophysics Data System (ADS)

Sarmah, Sangeeta; Jia, Gensuo; Zhang, Anzhi

2018-03-01

South Asia (SA) has been considered one of the most remarkable regions for changing vegetation greenness, accompanying its major expansion of agricultural activities, especially irrigated farming. The influence of the monsoon climate on the seasonal trends and anomalies of vegetation greenness is poorly understood in this area. Herein, we used the satellite-based Normalized Difference Vegetation Index (NDVI) to investigate various spatiotemporal patterns in vegetation activity during summer and winter monsoon (SM and WM) seasons and among irrigated croplands (IC), rainfed croplands (RC), and natural vegetation (NV) areas during 1982–2013. Seasonal NDVI variations with climatic factors (precipitation and temperature) and land use and cover changes (LUCC) have also been investigated. This study demonstrates that the seasonal dynamics of vegetation could improve the detailed understanding of vegetation productivity over the region. We found distinct greenness trends between two monsoon seasons and among the major land use/cover classes. Winter monsoons contributed greater variability to the overall vegetation dynamics of SA. Major greening occurred due to the increased productivity over irrigated croplands during the winter monsoon season; meanwhile, browning trends were prominent over NV areas during the same season. Maximum temperatures had been increasing tremendously during the WM season; however, the precipitation trend was not significant over SA. Both the climate variability and LUCC revealed coupled effects on the long term NDVI trends in NV areas, especially in the hilly regions, whereas anthropogenic activities (agricultural advancements) played a pivotal role in the rest of the area. Until now, advanced cultivation techniques have proven to be beneficial for the region in terms of the productivity of croplands. However, the crop productivity is at risk under climate change.

North Atlantic variability and its links to European climate over the last 3000 years.

PubMed

Moffa-Sánchez, Paola; Hall, Ian R

2017-11-23

The subpolar North Atlantic is a key location for the Earth's climate system. In the Labrador Sea, intense winter air-sea heat exchange drives the formation of deep waters and the surface circulation of warm waters around the subpolar gyre. This process therefore has the ability to modulate the oceanic northward heat transport. Recent studies reveal decadal variability in the formation of Labrador Sea Water. Yet, crucially, its longer-term history and links with European climate remain limited. Here we present new decadally resolved marine proxy reconstructions, which suggest weakened Labrador Sea Water formation and gyre strength with similar timing to the centennial cold periods recorded in terrestrial climate archives and historical records over the last 3000 years. These new data support that subpolar North Atlantic circulation changes, likely forced by increased southward flow of Arctic waters, contributed to modulating the climate of Europe with important societal impacts as revealed in European history.

Quantitative summer and winter temperature reconstructions from pollen and chironomid data in the Baltic-Belarus area

NASA Astrophysics Data System (ADS)

Veski, Siim; Seppä, Heikki; Stančikaitė, Migle; Zernitskaya, Valentina; Reitalu, Triin; Gryguc, Gražyna; Heinsalu, Atko; Stivrins, Normunds; Amon, Leeli; Vassiljev, Jüri; Heiri, Oliver

2015-04-01

Quantitative reconstructions based on fossil pollen and chironomids are widely used and useful for long-term climate variability estimations. The Lateglacial and early Holocene period (15-8 ka BP) in the Baltic-Belarus (BB) area between 60°-51° N was characterized by sudden shifts in climate due to various climate forcings affecting the climate of the northern hemisphere and North Atlantic, including the proximity of receding ice sheets. Climate variations in BB during the LG were eminent as the southern part of the region was ice free during the Last Glacial Maximum over 19 ka BP, whereas northern Estonia became ice free no sooner than 13 ka BP. New pollen based reconstructions of summer (May-to-August) and winter (December-to-February) temperatures between 15-8 ka BP along a S-N transect in the BB area display trends in temporal and spatial changes in climate variability. These results are completed by two chironomid-based July mean temperature reconstructions (Heiri et al. 2014). The magnitude of change compared with modern temperatures was more prominent in the northern part of BB area than in the southern part. The 4 °C winter and 2 °C summer warming at the start of GI-1 was delayed in the BB area and Lateglacial maximum temperatures were reached at ca 13.6 ka BP, being 4 °C colder than the modern mean. The Younger Dryas cooling in the area was 5 °C colder than present as inferred by all proxies (Veski et al. in press). In addition, our analyses show an early Holocene divergence in winter temperature trends with modern values reaching 1 ka earlier (10 ka BP) in southern BB compared to the northern part of the region (9 ka BP). Heiri, O., Brooks, S.J., Renssen, H., Bedford, A., Hazekamp, M., Ilyashuk, B., Jeffers, E.S., Lang, B., Kirilova, E., Kuiper, S., Millet, L., Samartin, S., Toth, M., Verbruggen, F., Watson, J.E., van Asch, N., Lammertsma, E., Amon, L., Birks, H.H., Birks, J.B., Mortensen, M.F., Hoek, W.Z., Magyari, E., Muñoz Sobrino, C., Seppä, H., Tinner, W., Tonkov, S., Veski, S., Lotter, A.F., 2014. Validation of climate model-inferred regional temperature change for late-glacial Europe. Nature Communications 5:4914, doi: 10.1038/ncomms5914 Veski, S., Seppä, H., Stančikaitė, M., Zernitskaya, V., Reitalu, T., Gryguc, G., Heinsalu, A., Stivrins, N., Amon, L., Vassiljev, J., Heiri, O. (in press). Quantitative summer and winter temperature reconstructions from pollen and chironomid data between 15 and 8 ka BP in the Baltic-Belarus area. Quaternary International. doi: 10.1016/j.quaint.2014.10.059

Climate change projections for winter precipitation over Tropical America using statistical downscaling

NASA Astrophysics Data System (ADS)

Palomino-Lemus, Reiner; Córdoba-Machado, Samir; Quishpe-Vásquez, César; García-Valdecasas-Ojeda, Matilde; Raquel Gámiz-Fortis, Sonia; Castro-Díez, Yolanda; Jesús Esteban-Parra, María

2017-04-01

In this study the Principal Component Regression (PCR) method has been used as statistical downscaling technique for simulating boreal winter precipitation in Tropical America during the period 1950-2010, and then for generating climate change projections for 2071-2100 period. The study uses the Global Precipitation Climatology Centre (GPCC, version 6) data set over the Tropical America region [30°N-30°S, 120°W-30°W] as predictand variable in the downscaling model. The mean monthly sea level pressure (SLP) from the National Center for Environmental Prediction - National Center for Atmospheric Research (NCEP-NCAR reanalysis project), has been used as predictor variable, covering a more extended area [30°N-30°S, 180°W-30°W]. Also, the SLP outputs from 20 GCMs, taken from the Coupled Model Intercomparison Project (CMIP5) have been used. The model data include simulations with historical atmospheric concentrations and future projections for the representative concentration pathways RCP2.6, RCP4.5, and RCP8.5. The ability of the different GCMs to simulate the winter precipitation in the study area for present climate (1971-2000) was analyzed by calculating the differences between the simulated and observed precipitation values. Additionally, the statistical significance at 95% confidence level of these differences has been estimated by means of the bilateral rank sum test of Wilcoxon-Mann-Whitney. Finally, to project winter precipitation in the area for the period 2071-2100, the downscaling model, recalibrated for the total period 1950-2010, was applied to the SLP outputs of the GCMs under the RCP2.6, RCP4.5, and RCP8.5 scenarios. The results show that, generally, for present climate the statistical downscaling shows a high ability to faithfully reproduce the precipitation field, while the simulations performed directly by using not downscaled outputs of GCMs strongly distort the precipitation field. For future climate, the projected predictions under the RCP4.5 and RCP8.5 scenarios show large areas with significant changes. For the RCP2.6 scenario, projected results present a predominance of very moderate decreases in rainfall, although significant in some models. Keywords: climate change projections, precipitation, Tropical America, statistical downscaling. Acknowledgements: This work has been financed by the projects P11-RNM-7941 (Junta de Andalucía-Spain) and CGL2013-48539-R (MINECO-Spain, FEDER).

Future road salt use in Switzerland: an example of an effective climate service

NASA Astrophysics Data System (ADS)

Zubler, Elias M.; Fischer, Andreas M.; Schlegel, Thomas H.; Liniger, Mark A.

2015-04-01

The application of salt is the predominant measure taken to enhance road safety in Switzerland by clearing the roads from snow or preventing frozen surfaces during winter. The need for road salt exhibits a strong interannual variability, according to Schweizer Salinen AG - the Swiss monopolist for production and distribution of road salt. These fluctuations are to a large extent a direct consequence of the year-to-year variability in winter climate. In the course of the 21st century, Swiss climate is projected to depart significantly from present and past conditions. By the end of the century, winter temperatures over Switzerland are expected to rise by about 2-4°C relative to the mean over the period 1980-2009, while winter precipitation may either increase or decrease based on ENSEMBLES regional climate model projections under the SRES-scenario A1B. Faced with these changes, Schweizer Salinen AG asked for an estimate of the expected future road salt use for designing their long-term business strategy. The study is based on climate change projections from the CH2011 initiative and later extensions thereof as well as monthly sales data of road salt from Schweizer Salinen AG. For the period 1997-2013, a linear relationship was derived between the average number of days with snowfall and the road salt amount sold over "saltation years" defined from October 1st to September 30th in the 26 cantons (provinces) of Switzerland. The ad-hoc linear relationship was applied to the climate change projections to obtain future salt use information in three future periods for the greenhouse gas emission scenarios A1B, A2 and RCP3PD. We find that the expected future salt use is likely to be reduced by about 50% in 2045-2074 under the scenario A1B. Currently, the countrywide mean annual road salt use corresponds to about 220'000 tons. In a particularly snow-rich year, the company sells up to 400'000 tons. At the end of the century, following a pessimistic scenario such as A1B or A2, the long-term mean salt use may even drop below today's annual minimum of 70'000 tons.

Linkages Between Terrestrial Carbon Uptake and Interannual Climate Variability over the Texas-northern Mexico High Plains

NASA Astrophysics Data System (ADS)

Parazoo, N.; Barnes, E. A.; Worden, J.; Harper, A. B.; Bowman, K. W.; Frankenberg, C.

2014-12-01

The Texas-northern Mexico high plains experienced record drought conditions in 2011 during strong negative phases of ENSO and the NAO. Given predictions of increased frequency and severity of drought under projected climate change [e.g., Reichstein et al., 2013] and recent findings of CO2 growth rate sensitivity to interannual variability of carbon uptake in semi-arid ecosystems [Poulter et al., 2014], we investigate the response of carbon uptake in the Texas high plains to interannual climate variability with the goal of improved mechanistic understanding of climate-carbon cycle links. Specifically, we examine (1) observed tendencies in regional scale carbon uptake and soil moisture from 2010 to 2011 using satellite observations of gross primary production (GPP) (from plant fluorescence) from GOSAT and soil moisture from SMOS, and (2) the interannual relationship between GPP and ENSO & NAO variability using terrestrial biosphere simulations from 1950-2012. Observations reveal widespread decline of GPP in 2011 (0.42 +/- 0.04 Pg C yr-1) correlated with negative soil moisture tendencies (r = 0.85 +/- 0.21) which leads to corresponding declines in net carbon uptake and transpiration (according to model simulations). Further examination of model results over the period 1950-2012 indicates that negative GPP anomalies are linked systematically to winter and spring precipitation deficits associated with overlapping negative phases of winter NAO and ENSO, with increasing magnitude of negative anomalies in strong La Niña years. Furthermore, the strongest decline of GPP, carbon uptake, and transpiration on record occurred during the 2011 drought and were associated with extreme negative phases of ENSO and NAO, with 2011 being the only year since 1950 that both indices exceeded 1 σ standard deviation.

Seasonal Predictability in a Model Atmosphere.

NASA Astrophysics Data System (ADS)

Lin, Hai

2001-07-01

The predictability of atmospheric mean-seasonal conditions in the absence of externally varying forcing is examined. A perfect-model approach is adopted, in which a global T21 three-level quasigeostrophic atmospheric model is integrated over 21 000 days to obtain a reference atmospheric orbit. The model is driven by a time-independent forcing, so that the only source of time variability is the internal dynamics. The forcing is set to perpetual winter conditions in the Northern Hemisphere (NH) and perpetual summer in the Southern Hemisphere.A significant temporal variability in the NH 90-day mean states is observed. The component of that variability associated with the higher-frequency motions, or climate noise, is estimated using a method developed by Madden. In the polar region, and to a lesser extent in the midlatitudes, the temporal variance of the winter means is significantly greater than the climate noise, suggesting some potential predictability in those regions.Forecast experiments are performed to see whether the presence of variance in the 90-day mean states that is in excess of the climate noise leads to some skill in the prediction of these states. Ensemble forecast experiments with nine members starting from slightly different initial conditions are performed for 200 different 90-day means along the reference atmospheric orbit. The serial correlation between the ensemble means and the reference orbit shows that there is skill in the 90-day mean predictions. The skill is concentrated in those regions of the NH that have the largest variance in excess of the climate noise. An EOF analysis shows that nearly all the predictive skill in the seasonal means is associated with one mode of variability with a strong axisymmetric component.

Large and local-scale influences on physical and chemical characteristics of coastal waters of Western Europe during winter

NASA Astrophysics Data System (ADS)

Tréguer, Paul; Goberville, Eric; Barrier, Nicolas; L'Helguen, Stéphane; Morin, Pascal; Bozec, Yann; Rimmelin-Maury, Peggy; Czamanski, Marie; Grossteffan, Emilie; Cariou, Thierry; Répécaud, Michel; Quéméner, Loic

2014-11-01

There is now a strong scientific consensus that coastal marine systems of Western Europe are highly sensitive to the combined effects of natural climate variability and anthropogenic climate change. However, it still remains challenging to assess the spatial and temporal scales at which climate influence operates. While large-scale hydro-climatic indices, such as the North Atlantic Oscillation (NAO) or the East Atlantic Pattern (EAP) and the weather regimes such as the Atlantic Ridge (AR), are known to be relevant predictors of physical processes, changes in coastal waters can also be related to local hydro-meteorological and geochemical forcing. Here, we study the temporal variability of physical and chemical characteristics of coastal waters located at about 48°N over the period 1998-2013 using (1) sea surface temperature, (2) sea surface salinity and (3) nutrient concentration observations for two coastal sites located at the outlet of the Bay of Brest and off Roscoff, (4) river discharges of the major tributaries close to these two sites and (5) regional and local precipitation data over the region of interest. Focusing on the winter months, we characterize the physical and chemical variability of these coastal waters and document changes in both precipitation and river runoffs. Our study reveals that variability in coastal waters is connected to the large-scale North Atlantic atmospheric circulation but is also partly explained by local river influences. Indeed, while the NAO is strongly related to changes in sea surface temperature at the Brest and Roscoff sites, the EAP and the AR have a major influence on precipitations, which in turn modulate river discharges that impact sea surface salinity at the scale of the two coastal stations.

Rising climate variability and synchrony in North Pacific ecosystems

NASA Astrophysics Data System (ADS)

Black, Bryan

2017-04-01

Rising climate variability and synchrony in North Pacific ecosystems Evidence is growing that climate variability of the northeast Pacific Ocean has increased over the last century, culminating in such events as the record-breaking El Niño years 1983, 1998, and 2016 and the unusually persistent 2014/15 North Pacific Ocean heat wave known as "The Blob." Of particular concern is that rising variability could increase synchrony within and among North Pacific ecosystems, which could reduce the diversity of biological responses to climate (i.e. the "portfolio effect"), diminish resilience, and leave populations more prone to extirpation. To test this phenomenon, we use a network of multidecadal fish otolith growth-increment chronologies that were strongly correlated to records of winter (Jan-Mar) sea level. These biological and physical datasets spanned the California Current through the Gulf of Alaska. Synchrony was quantified as directional changes in running (31-year window) mean pairwise correlation within sea level and then within otolith time series. Synchrony in winter sea level at the nine stations with the longest records has increased by more than 40% over the 1950-2015 interval. Likewise, synchrony among the eight longest otolith chronologies has increased more than 100% over a comparable time period. These directional changes in synchrony are highly unlikely due to chance alone, as confirmed by comparing trends in observed data to those in simulated data (n = 10,000 iterations) with time series of identical number, length, and autocorrelation. Ultimately, this trend in rising synchrony may be linked to increased impacts of the El Niño Southern Oscillation (ENSO) on mid-latitude ecosystems of North America, and may therefore reflect a much broader, global-scale signature.

Contributions of dynamic environmental signals during life-cycle transitions to early life-history traits in lodgepole pine (Pinus contorta Dougl.)

NASA Astrophysics Data System (ADS)

Liu, Yang; Wang, Tongli; El-Kassaby, Yousry A.

2016-05-01

Environmental signals are important triggers in the life-cycle transitions and play a crucial role in the life-history evolution. Yet very little is known about the leading ecological factors contributing to the variations of life-history traits in perennial plants. This paper explores both the causes and consequences for the evolution of life-history traits (i.e., seed dormancy and size) in lodgepole pine (Pinus contorta Dougl.) across British Columbia (B.C.), Canada. We selected 83 logepole pine populations covering 22 ecosystem zones of B.C. and through their geographic coordinate, 197 climatic variables were generated accordingly for the reference (1961-1990) and future (2041-2070) periods. We found that dynamic climatic variables rather than constant geographic variables are the true environmental driving forces in seed dormancy and size variations and thus provide reliable predictors in response to global climate change. Evapotranspiration and precipitation in the plant-to-seed chronology are the most critical climate variables for seed dormancy and size variations, respectively. Hence, we predicted that levels of seed dormancy in lodgepole pine would increase across large tracts of B.C. in 2050s. Winter-chilling is able to increase the magnitude of life-history plasticity and lower the bet-hedge strategy in the seed-to-plant transition; however, winter-chilling is likely to be insufficient in the north of 49° N in 2050s, which may delay germination while unfavorable conditions during dry summers may result in adverse consequences in the survival of seedlings owing to extended germination span. These findings provide useful information to studies related to assessments of seed transfer and tree adaptation.

Effects of winter temperature and summer drought on net ecosystem exchange of CO2 in a temperate peatland

NASA Astrophysics Data System (ADS)

Helfter, Carole; Campbell, Claire; Dinsmore, Kerry; Drewer, Julia; Coyle, Mhairi; Anderson, Margaret; Skiba, Ute; Nemitz, Eiko; Billett, Michael; Sutton, Mark

2014-05-01

Northern peatlands are one of the most important global sinks of atmospheric carbon dioxide (CO2); their ability to sequester C is a natural feedback mechanism controlled by climatic variables such as precipitation, temperature, length of growing season and period of snow cover. In the UK it has been predicted that peatlands could become a net source of carbon in response to climate change with climate models predicting a rise in global temperature of ca. 3oC between 1961-1990 and 2100. Land-atmosphere exchange of CO2in peatlands exhibits marked seasonal and inter-annual variations, which have significant short- and long-term effects on carbon sink strength. Net ecosystem exchange (NEE) of CO2 has been measured continuously by eddy-covariance (EC) at Auchencorth Moss (55° 47'32 N, 3° 14'35 W, 267 m a.s.l.), a temperate peatland in central Scotland, since 2002. Auchencorth Moss is a low-lying, ombrotrophic peatland situated ca. 20 km south-west of Edinburgh. Peat depth ranges from 5 m and the site has a mean annual precipitation of 1155 mm. The vegetation present within the flux measurement footprint comprises mixed grass species, heather and substantial areas of moss species (Sphagnum spp. and Polytrichum spp.). The EC system consists of a LiCOR 7000 closed-path infrared gas analyser for the simultaneous measurement of CO2 and water vapour and of a Gill Windmaster Pro ultrasonic anemometer. Over the 10 year period, the site was a consistent yet variable sink of CO2 ranging from -34.1 to -135.9 g CO2-C m-2 yr-1 (mean of -69.1 ± 33.6 g CO2-C m-2 yr-1). Inter-annual variability in NEE was positively correlated to the length of the growing seasons and mean winter air temperature explained 93% of the variability in summertime sink strength, indicating a phenological memory-effect. Plant development and productivity were stunted by colder winters causing a net reduction in the annual carbon sink strength of this peatland where autotrophic processes are thought to be dominant. The site is wet throughout most of the year (water table depth < 5 cm below the peat surface), but there are indications that drought enhanced heterotrophic respiration and depressed gross primary productivity (GPP); a sustained drought during the summer of 2010 (maximum water table depth 36 cm below surface) was accompanied by a two-fold increase in total respiration and a 30% decrease in GPP. The cold preceding winter could also have contributed to lowering GPP, and disentangling the confounding adverse effects of drought and winter climate on GPP is thus not straightforward. Whilst 2010 had the smallest NEE in the 2002-2012 period, the largest values were found for years with warm winters and relatively wet growing seasons. A simple parameterisation of the effects of PAR on GPP of and air temperature on ecosystem respiration, suggest that a rise in air temperature of 1° C between 2012 and 2065 could lead to a 73% increase in the carbon sink strength of the peatland, provided hydrological conditions remain unchanged. This demonstrates that climate change is not likely to change this peatland into a carbon source by 2100.

Arctic sea ice trends, variability and implications for seasonal ice forecasting

PubMed Central

Serreze, Mark C.; Stroeve, Julienne

2015-01-01

September Arctic sea ice extent over the period of satellite observations has a strong downward trend, accompanied by pronounced interannual variability with a detrended 1 year lag autocorrelation of essentially zero. We argue that through a combination of thinning and associated processes related to a warming climate (a stronger albedo feedback, a longer melt season, the lack of especially cold winters) the downward trend itself is steepening. The lack of autocorrelation manifests both the inherent large variability in summer atmospheric circulation patterns and that oceanic heat loss in winter acts as a negative (stabilizing) feedback, albeit insufficient to counter the steepening trend. These findings have implications for seasonal ice forecasting. In particular, while advances in observing sea ice thickness and assimilating thickness into coupled forecast systems have improved forecast skill, there remains an inherent limit to predictability owing to the largely chaotic nature of atmospheric variability. PMID:26032315

Subseasonal Reversal of East Asian Surface Temperature Variability in Winter 2014/15

NASA Astrophysics Data System (ADS)

Xu, Xinping; Li, Fei; He, Shengping; Wang, Huijun

2018-06-01

Although there has been a considerable amount of research conducted on the East Asian winter-mean climate, subseasonal surface air temperature (SAT) variability reversals in the early and late winter remain poorly understood. In this study, we focused on the recent winter of 2014/15, in which warmer anomalies dominated in January and February but colder conditions prevailed in December. Moreover, Arctic sea-ice cover (ASIC) in September-October 2014 was lower than normal, and warmer sea surface temperature (SST) anomalies occurred in the Niño4 region in winter, together with a positive Pacific Decadal Oscillation (PDO|+) phase. Using observational data and CMIP5 historical simulations, we investigated the PDO|+ phase modulation upon the winter warm Niño4 phase (autumn ASIC reduction) influence on the subseasonal SAT variability of East Asian winter. The results show that, under a PDO|+ phase modulation, warm Niño4 SST anomalies are associated with a subseasonal delay of tropical surface heating and subsequent Hadley cell and Ferrel cell intensification in January-February, linking the tropical and midlatitude regions. Consistently, the East Asian jet stream (EAJS) is significantly decelerated in January-February and hence promotes the warm anomalies over East Asia. Under the PDO|+ phase, the decrease in ASIC is related to cold SST anomalies in the western North Pacific, which increase the meridional temperature gradient and generate an accelerated and westward-shifted EAJS in December. The westward extension of the EAJS is responsible for the eastward-propagating Rossby waves triggered by declining ASIC and thereby favors the connection between ASIC and cold conditions over East Asia.

Evaluating interannual variability in speleothem records of North American monsoon rainfall

NASA Astrophysics Data System (ADS)

Truebe, S. A.; Cole, J. E.; Ault, T. R.; Kimbrough, A.; Henderson, G. M.; Barmett, H.; Hlohowskyj, S.

2013-12-01

Speleothems can produce long, high resolution, absolutely-dated records of past climate. They are especially useful for past climate reconstruction in areas such as the southwestern United States, where traditional sources of past climate information (corals, lake or ocean sediments, ice cores) are absent. Here we present two records of Holocene rainfall variability from two Arizona caves less than 40km apart: Cave of the Bells (COB) and Fort Huachuca Cave (FHC), spanning 7000 and 4000 years respectively. Both records show a trend towards more negative oxygen isotope values into the modern era. Extensive monthly monitoring suggests that speleothem oxygen isotope composition is an average of the oxygen isotope composition of the summer North American monsoon (NAM) and winter frontal storms, with a bias towards winter likely due to lack of infiltration of intense monsoon rainfall. This bias is stronger in COB than in FHC. Winter rainfall has had an increasing influence at both sites from the mid-Holocene until the present; in other words, the NAM has been weakening over the past few thousand years, in step with changes in other monsoon systems and Northern Hemisphere insolation. Although the records are similar in overall trend, short-term variability is inconsistent. When providing information to water managers about future rainfall availability in the Southwest, having only millennial-scale information does not help much! To investigate the differences between the two records, we use a combination of approaches, including assessing age model uncertainty and modern climate heterogeneity, and monitoring cave-specific processes that may be overprinting the climate signal. We assess age model uncertainty using a statistical age-modeling program, which allows us to develop many physically plausible time series for the same age-depth data. With this age modeling tool, we critically assess whether particular isotope excursions correspond between speleothems and if they are temporally related to global climate events. However, even correlation and coherence analyses across the suites of time series for each speleothem do not elicit a common high-frequency climate story. We further investigate the discrepancy between cave records by assessing modern climate heterogeneity using historical observations. Climate in the arid Southwest is spatially heterogeneous, especially during the summer monsoon, contributing to the mismatch between these two climate records. Finally, after a decade of monitoring at COB, we recognize that storage and mixing in the epikarst above the cave affect what parts (if any) of the seasonal signal are recorded in a speleothem. In addition to new insights about North American monsoon behavior during the Holocene, the important lesson from these speleothem records is that in caves, because of underlying (overlying?) climate heterogeneity, replication of a common climate signal using oxygen isotopes may be an unattainable goal. The COB and FHC records may record very local climate at their respective locations, overprinted by water storage and mixing in the epikarst. Very local-scale reconstructions of past rainfall variability from speleothems can still be useful and important, if interpreted for what they are.

Errors and uncertainties in regional climate simulations of rainfall variability over Tunisia: a multi-model and multi-member approach

NASA Astrophysics Data System (ADS)

Fathalli, Bilel; Pohl, Benjamin; Castel, Thierry; Safi, Mohamed Jomâa

2018-02-01

Temporal and spatial variability of rainfall over Tunisia (at 12 km spatial resolution) is analyzed in a multi-year (1992-2011) ten-member ensemble simulation performed using the WRF model, and a sample of regional climate hindcast simulations from Euro-CORDEX. RCM errors and skills are evaluated against a dense network of local rain gauges. Uncertainties arising, on the one hand, from the different model configurations and, on the other hand, from internal variability are furthermore quantified and ranked at different timescales using simple spread metrics. Overall, the WRF simulation shows good skill for simulating spatial patterns of rainfall amounts over Tunisia, marked by strong altitudinal and latitudinal gradients, as well as the rainfall interannual variability, in spite of systematic errors. Mean rainfall biases are wet in both DJF and JJA seasons for the WRF ensemble, while they are dry in winter and wet in summer for most of the used Euro-CORDEX models. The sign of mean annual rainfall biases over Tunisia can also change from one member of the WRF ensemble to another. Skills in regionalizing precipitation over Tunisia are season dependent, with better correlations and weaker biases in winter. Larger inter-member spreads are observed in summer, likely because of (1) an attenuated large-scale control on Mediterranean and Tunisian climate, and (2) a larger contribution of local convective rainfall to the seasonal amounts. Inter-model uncertainties are globally stronger than those attributed to model's internal variability. However, inter-member spreads can be of the same magnitude in summer, emphasizing the important stochastic nature of the summertime rainfall variability over Tunisia.

Disruption of the European climate seasonal clock in a warming world

NASA Astrophysics Data System (ADS)

Cattiaux, J.; Cassou, C.

2015-12-01

Strength and inland penetration of the oceanic westerly flow over Europe control a large part of the temperature variability over most of the continent. Reduced westerlies, linked to high-pressure anomalies over Scandinavia, induce cold conditions in winter and warm conditions in summer. Here we propose to define the onset of these two seasons as the calendar day where the daily circulation/temperature relationship over Western Europe switches sign. According to this meteorologically-based metrics assessed from several observational datasets, we provide robust evidence for an earlier summer onset by ~10 days between the 1960s and 2000s. Results from model ensemble simulations dedicated to detection-attribution show that this calendar advance is incompatible with the sole internal climate variability and can be attributed to anthropogenic forcings. Late winter snow disappearance over Eastern Europe affects cold air intrusion to the West when easterlies blow, and is mainly responsible for the observed present-day and near-future summer advance. Our findings agree with phenological-based trends (earlier spring events) reported for many living species over Europe, for which they provide a novel dynamical interpretation beyond the traditionally evoked global warming effect. Based on business-as-usual scenario, a seasonal shift of ~25 days is expected by 2100 for summer onset, while no clear signal arises for winter onset.

Exceptional Arctic warmth of early winter 2016 and attribution to global warming

NASA Astrophysics Data System (ADS)

van Oldenborgh, Geert Jan; Macias-Fauria, Marc; King, Andrew; Uhe, Peter; Philip, Sjoukje; Kew, Sarah; Karoly, David; Otto, Friederike; Allen, Myles; Cullen, Heidi

2017-04-01

The dark polar winters usually sport the coldest extremes on Earth, however this winter, the North Pole and the surrounding Arctic region have experienced record high temperatures in November and December, with daily means reaching 15 °C (27 °F) above normal and a November monthly mean that was 13 °C (23 °F) above normal on the pole. November also saw a brief retreat of sea-ice that was virtually unprecedented in nearly 40 years of satellite records, followed by a record low in November sea ice area since 1850. Unlike the Antarctic, Arctic lands are inhabited and their socio-economic systems are greatly affected by the impacts of extreme and unprecedented sea ice dynamics and temperatures, such as for example, the timing of marine mammal migrations, and refreezing rain on snow that prevents reindeer from feeding. Here we report on our multi-method rapid attribution analysis of North Pole November-December temperatures. To quantify the rarity of the event, we computed the November-December averaged temperature around the North Pole (80-90 °N) in the (short but North-pole covering) ERA-interim reanalysis. To put the event in context of natural variability, we use a longer and closely related time series based on the northern most meteorological observations on land (70-80 °N). This allows for a reconstruction of Arctic temperatures back to about 1900. We also perform a multi-method analysis of North Pole temperatures with two sets of climate models: the CMIP5 multi-model ensemble, and a large ensemble of model runs in the so-called Weather@Home project. Physical mechanisms that are responsible for temperature and sea ice variability in the North Pole region are also discussed. The observations and the bias-corrected CMIP5 ensemble point to a return period of about 50 to 200 years in the present climate, i.e., the probability of such an extreme is about 0.5% to 2% every year, with a large uncertainty. The observations show that November-December temperatures have risen on the North Pole, modulated by decadal North Atlantic variability. For all phases of this variability, a warm event like the one of this winter would have been extremely unlikely in the climate of a century ago. Both sets of models also give very comparable results and show that the bulk of the arctic temperature increase is due to anthropogenic emissions. This also holds for the warm extremes caused by the type of circulation present in the early winter of 2016.

North Atlantic summers have warmed more than winters since 1353, and the response of marine zooplankton.

PubMed

Kamenos, Nicholas A

2010-12-28

Modeling and measurements show that Atlantic marine temperatures are rising; however, the low temporal resolution of models and restricted spatial resolution of measurements (i) mask regional details critical for determining the rate and extent of climate variability, and (ii) prevent robust determination of climatic impacts on marine ecosystems. To address both issues for the North East Atlantic, a fortnightly resolution marine climate record from 1353-2006 was constructed for shallow inshore waters and compared to changes in marine zooplankton abundance. For the first time summer marine temperatures are shown to have increased nearly twice as much as winter temperatures since 1353. Additional climatic instability began in 1700 characterized by ∼5-65 year climate oscillations that appear to be a recent phenomenon. Enhanced summer-specific warming reduced the abundance of the copepod Calanus finmarchicus, a key food item of cod, and led to significantly lower projected abundances by 2040 than at present. The faster increase of summer marine temperatures has implications for climate projections and affects abundance, and thus biomass, near the base of the marine food web with potentially significant feedback effects for marine food security.

Regulation of stream water dissolved organic carbon concentrations ([DOC]) during snowmelt in forest streams; the role of discharge, winter climate and memory effects

NASA Astrophysics Data System (ADS)

Ågren, A.; Haei, M.; Öquist, M.; Buffam, I.; Ottosson-Löfvenius, M.; Kohler, S.; Bishop, K.; Blomkvist, P.; Laudon, H.

2011-12-01

Using 15 year stream records from two forested northern boreal catchments, coupled with soil frost experiments in the riparian zone, we demonstrate the complex inter-annual control on [DOC] and export during snowmelt. Stream [DOC] varied by a factor of 2 during those 15 years with no consistent trend. Based on our long-term analysis, we demonstrate, for the first time, that stream water [DOC] is strongly linked to the climatic conditions during the preceding winter, but that there is also a long-term memory effect in the catchment soils, related to the extent of the previous export from the catchment. Hydrology had a first order control on the inter-annual variation in concentrations, and the length of the winter was more important than the memory effect. By removing the effect of discharge on [DOC], using a conceptual hydrological model, we could detect processes that would otherwise have been overshadowed. A short and intense snowmelt gave higher [DOC] in the stream. During a prolonged snowmelt, one soil layer at the time might have been "flushed" from easily exported DOC, resulting in slightly lower stream [DOC] during such years. We found that longer and colder winters resulted in higher [DOC] during the subsequent snowmelt. A soil frost manipulation experiment in the riparian soils of the study catchment showed that the DOC concentrations in the soil water increased with the duration of the soil frost. A high antecedent DOC export during the preceding summer and autumn resulted in lower concentrations during the following spring, indicating a long-term "memory effect" of the catchment soils. In a nearby stream draining mire, we found a different response to hydrology but similar response to climate and memory effect. The inter-annual variation in snowmelt DOC exports was mostly controlled by the amount of runoff, but the variability in [DOC] also exerted a significant control on the exports, accounting for 15% of the variance in exports. We conclude that winter climatic conditions can play a substantial role in controlling stream [DOC] in ways not previously understood. These findings are especially important for northern latitude regions expected to be most affected by climate change. It's difficult to directly translate this to a future climate change prediction. If warmer winters with less insulating snow cover increase the soil frost, the results from the soil frost manipulation experiment then suggest increasing [DOC] in a future climate. At the same time the statistical analysis of the stream records suggest that a shorter and warmer winter would decrease the [DOC]. Our results do, however, highlight the role of winter climate for regulating DOC in areas with seasonally frozen soils which should be considered when resolving the sensitivity of stream [DOC] to global environmental change.

Modeling Dynamics of South American Rangelands to Climate Variability and Human Impact

NASA Astrophysics Data System (ADS)

Stanimirova, R.; Arevalo, P. A.; Kaufmann, R.; Maus, V.; Lesiv, M.; Havlik, P.; Friedl, M. A.

2017-12-01

The combined pressures of climate change and shifting dietary preferences are creating an urgent need to improve understanding of how climate and land management are jointly affecting the sustainability of rangelands. In particular, our ability to effectively manage rangelands in a manner that satisfies increasing demand for meat and dairy while reducing environmental impact depends on the sensitivity of rangelands to perturbations from both climate (e.g., drought) and land use (e.g., grazing). To characterize the sensitivity of rangeland vegetation to variation in climate, we analyzed gridded time series of satellite and climate data at 0.5-degree spatial resolution from 2003 to 2016 for rangeland ecosystems in South America. We used panel regression and canonical correlation to analyze the relationship between time series of enhanced vegetation index (EVI) derived from NASA's Moderate Spatial Resolution Imaging Spectroradiometer (MODIS) and gridded precipitation and air temperature data from the University of East Anglia's Climate Research Unit. To quantify the degree to which livestock management explains geographic variation of EVI, we used global livestock distribution (FAO) and feed requirements data from the Global Biosphere Management Model (GLOBIOM). Because rangeland ecosystems are sensitive to changes in meteorological variables at different time scales, we evaluated the strength of coupling between anomalies in EVI and anomalies in temperature and standardized precipitation index (SPI) data at 1-6 month lags. Our results show statistically significant relationships between EVI and precipitation during summer, fall, and winter in both tropical and subtropical agroecological zones of South America. Further, lagged precipitation effects, which reflect memory in the system, explain significant variance in winter EVI anomalies. While precipitation emerges as the dominant driver of variability in rangeland greenness, we find evidence of a management-induced signal as well. Our modeling framework integrates satellite observation, meteorological data sets, and land use/cover change information to improve our capability to monitor and manage the long-term sustainability of rangelands.

Natural climate variability and teleconnections to precipitation over the Pacific-North American region in CMIP3 and CMIP5 models

NASA Astrophysics Data System (ADS)

Polade, Suraj D.; Gershunov, Alexander; Cayan, Daniel R.; Dettinger, Michael D.; Pierce, David W.

2013-05-01

climate variability will continue to be an important aspect of future regional climate even in the midst of long-term secular changes. Consequently, the ability of climate models to simulate major natural modes of variability and their teleconnections provides important context for the interpretation and use of climate change projections. Comparisons reported here indicate that the CMIP5 generation of global climate models shows significant improvements in simulations of key Pacific climate mode and their teleconnections to North America compared to earlier CMIP3 simulations. The performance of 14 models with simulations in both the CMIP3 and CMIP5 archives are assessed using singular value decomposition analysis of simulated and observed winter Pacific sea surface temperatures (SSTs) and concurrent precipitation over the contiguous United States and northwestern Mexico. Most of the models reproduce basic features of the key natural mode and their teleconnections, albeit with notable regional deviations from observations in both SST and precipitation. Increasing horizontal resolution in the CMIP5 simulations is an important, but not a necessary, factor in the improvement from CMIP3 to CMIP5.

Natural climate variability and teleconnections to precipitation over the Pacific-North American region in CMIP3 and CMIP5 models

USGS Publications Warehouse

Polade, Suraj D.; Gershunov, Alexander; Cayan, Daniel R.; Dettinger, Michael D.; Pierce, David W.

2013-01-01

Natural climate variability will continue to be an important aspect of future regional climate even in the midst of long-term secular changes. Consequently, the ability of climate models to simulate major natural modes of variability and their teleconnections provides important context for the interpretation and use of climate change projections. Comparisons reported here indicate that the CMIP5 generation of global climate models shows significant improvements in simulations of key Pacific climate mode and their teleconnections to North America compared to earlier CMIP3 simulations. The performance of 14 models with simulations in both the CMIP3 and CMIP5 archives are assessed using singular value decomposition analysis of simulated and observed winter Pacific sea surface temperatures (SSTs) and concurrent precipitation over the contiguous United States and northwestern Mexico. Most of the models reproduce basic features of the key natural mode and their teleconnections, albeit with notable regional deviations from observations in both SST and precipitation. Increasing horizontal resolution in the CMIP5 simulations is an important, but not a necessary, factor in the improvement from CMIP3 to CMIP5.

Development of the Wintertime Sr/Ca-SST Record from Red Sea Corals as a Proxy for the North Atlantic Oscillation

NASA Astrophysics Data System (ADS)

Bernstein, W. N.; Hughen, K. A.

2009-12-01

The North Atlantic Oscillation (NAO) is one of the most pronounced and influential patterns in winter atmospheric circulation variability. This meridional redistribution of atmospheric mass across the Atlantic Ocean produces large changes in the intensity, number and direction of storms generated within the basin, and the regional climate of surrounding continents. The NAO exerts a significant impact on society, through influences on agriculture, fisheries, water management, energy generation and coastal development. NAO effects on climate extend from eastern North America across Europe to the eastern Mediterranean and Middle East. Changes in NAO behavior during the late 20th century have been linked to global warming; yet despite its importance, the causes and long-term patterns of NAO variability in the past remain poorly understood. In order to better predict the influence of the NAO on climate in the future, it is critical to examine multi-century NAO variability. The Red Sea is an excellent location from which to generate long NAO records for two reasons. First, patterns of wintertime sea surface temperature (SST) and salinity (SSS) in the Red Sea are highly correlated with NAO variability (Visbeck et al. 2001; Hurrell et al. 2003). Second, the tropical/subtropical Red Sea region contains fast growing long-lived massive Porites spp. corals with annually banded skeletons. These corals are ideal for generating well-dated high-resolution paleoclimatic records that extend well beyond the instrumental period. Here we present a study of winter SST and NAO variability in the Red sea region based on coral Sr/Ca data. In 2008, we collected multiple drill cores ranging in length from 1 to 4.1 meters from Porites corals at six sites spanning a large SST gradient. Sr/Ca measurements from multiple corals will be regressed against 23 years of satellite SST data, expanding the SST range over which we calibrate. A sampling resolution of 0.5mm will yield greater than bi-weekly temporal resolution for downcore SST reconstructions over the past 140 years, which will be used to evaluate the ability of the coral proxies to capture instrumental NAO variability. We expect that this winter Sr/Ca record will exhibit coherence with the NAO similar to that evident between Red Sea instrumental SST and the NAO index. Future work will involve construction of an NAO record back ~400 years, using the multi-core Sr/Ca-SST calibration applied to a combination of new records from modern and fossil coral material. This record will be examined to identify changes in NAO behavior as a function of frequency, and to compare frequency-dependent NAO variability between periods of relatively warm and cold hemispheric climate. This analysis will allow us to test the hypothesized link between NAO behavior and mean climate conditions, and if confirmed, improve predictions regarding the role of the NAO in impending climate change. References Hurrell, J. et al., 2003, in The North Atlantic Oscillation: Climatic Significance and Environmental Impact, 1-36 (A.G.U., Washington, D.C.). Visbeck, M. et al., 2001, Proc. Nat. Acad. Sci. 98, 12876-12877.

The absence of an Atlantic imprint on the multidecadal variability of wintertime European temperature.

PubMed

Yamamoto, Ayako; Palter, Jaime B

2016-03-15

Northern Hemisphere climate responds sensitively to multidecadal variability in North Atlantic sea surface temperature (SST). It is therefore surprising that an imprint of such variability is conspicuously absent in wintertime western European temperature, despite that Europe's climate is strongly influenced by its neighbouring ocean, where multidecadal variability in basin-average SST persists in all seasons. Here we trace the cause of this missing imprint to a dynamic anomaly of the atmospheric circulation that masks its thermodynamic response to SST anomalies. Specifically, differences in the pathways Lagrangian particles take to Europe during anomalous SST winters suppress the expected fluctuations in air-sea heat exchange accumulated along those trajectories. Because decadal variability in North Atlantic-average SST may be driven partly by the Atlantic Meridional Overturning Circulation (AMOC), the atmosphere's dynamical adjustment to this mode of variability may have important implications for the European wintertime temperature response to a projected twenty-first century AMOC decline.

Linkages Between Multiscale Global Sea Surface Temperature Change and Precipitation Variabilities in the US

NASA Technical Reports Server (NTRS)

Lau, K. M.; Weng, Heng-Yi

1999-01-01

A growing number of evidence indicates that there are coherent patterns of variability in sea surface temperature (SST) anomaly not only at interannual timescales, but also at decadal-to-inter-decadal timescale and beyond. The multi-scale variabilities of SST anomaly have shown great impacts on climate. In this work, we analyze multiple timescales contained in the globally averaged SST anomaly with and their possible relationship with the summer and winter rainfall in the United States over the past four decades.

Soil water improvements with the long-term use of a winter rye cover crop

USDA-ARS?s Scientific Manuscript database

The Midwestern United States is projected to experience increasing rainfall variability. One approach to mitigate climate impacts is to utilize crop and soil management practices that enhance soil water storage, reducing the risks of flooding as well as drought-induced crop water stress. While some ...

Synoptic moisture pathways associated with mean and extreme precipitation over Canada for winter and spring

NASA Astrophysics Data System (ADS)

Tan, X.; Gan, T. Y. Y.; Chen, Y. D.

2017-12-01

Dominant synoptic moisture pathway patterns of vertically integrated water vapor transport (IVT) in winter and spring over Canada West and East were identified using the self-organizing map method. Large-scale meteorological patterns (LSMPs) were related to the variability in seasonal precipitation totals and occurrences of precipitation extremes. Changes in both occurrences of LSMPs and seasonal precipitation occurred under those LSMPs were evaluated to attribute observed changes in seasonal precipitation totals and occurrences of precipitation extremes. Effects of large-scale climate anomalies on occurrences of LSMPs were also examined. Results show that synoptic moisture pathways and LSMPs exhibit the propagation of jet streams as the location and direction of ridges and troughs, and the strength and center of pressure lows and highs varied considerably between LSMPs. Significant decreases in occurrences of synoptic moisture pathway patterns that are favorable with positive precipitation anomalies and more precipitation extremes in winter over Canada West resulted in decreases in seasonal precipitation and occurrences of precipitation extremes. LSMPs resulting in a hot and dry climate and less (more) frequent precipitation extremes over the Canadian Prairies in winter and northwestern Canada in spring are more likely to occur in years with a negative phase of PNA. Occurrences of LSMPs for a wet climate and frequent occurrences of extreme precipitation events over southeastern Canada are associated with a positive phase of NAO. In El Niño years or negative PDO years, LSMPs associated with a dry climate and less frequent precipitation extremes over western Canada tend to occur.

Relation between climatic factors, diet and reproductive parameters of Little Terns over a decade

NASA Astrophysics Data System (ADS)

Ramos, Jaime A.; Pedro, Patrícia; Matos, Antonio; Paiva, Vitor H.

2013-11-01

We used 10 years of data on clutch size, egg size and diet, and 8 years of data on timing of laying on Little Terns (Sternula albifrons) breeding in Ria Formosa lagoon system, Algarve, Portugal to assess whether diet acts as an important intermediary between climatic conditions and breeding parameters. We used Generalized Linear Models to relate (1) the relative occurrence and size of the main prey species, sand smelts (Atherina spp.), with environmental variables, a large-scale climate variable, the North Atlantic Oscillation (NAO) index, and a local scale variable, the sea-surface temperature (SST), and (2) the respective effects of sand smelts relative occurrence, NAO index and SST on Little Tern breeding parameters. The diet of Little Terns was dominated by sand smelts, with a frequency occurrence of over 60% in all years. The winter SST (February) was negatively associated with the relative occurrence of sand smelts in the diet of Little Terns during the breeding season which, in turn, was positively associated with Little Tern clutch size. Our results suggest that negative NAO conditions in the Atlantic Ocean, often associated with rougher sea conditions (greater vertical mixing, stronger winds and lower SST) were related with earlier breeding, and lower SST in the surroundings of the colony during winter-spring favour the abundance of prey fish for Little Terns as well as their reproductive parameters. Climate patterns at both large and local scales are likely to change in the future, which may have important implications for estuarine seabirds in Southern Europe.

Influence of seasonal climatic variability on shallow infiltration at Yucca Mountain

USGS Publications Warehouse

Hevesi, Joseph A.; Flint, Alan L.

1993-01-01

To analyze infiltration and the redistribution of moisture in alluvial deposits at Yucca Mountain, water content profiles at a 13.5 m deep borehole were measured at monthly intervals using a neutron moisture probe. Increases in water content to a maximum depth of 1.8 m in response to winter season precipitation were noted. Below a depth of 1.8 m, a gradual drying trend was indicated. A simulation study showed that, although small amounts of water may be percolating through the deep nonwetted ones of the profile, the influence of climatic variability on infiltration through thick alluvial deposits at Yucca Mountain is greatly mitigated by evapotranspiration.

Decadal-to-centennial-scale climate variability: Insights into the rise and fall of the Great Salt Lake

NASA Technical Reports Server (NTRS)

Mann, Michael E.; Lall, Upmanu; Saltzman, Barry

1995-01-01

We demonstrate connections between decadal and secular global climatic variations, and historical variations in the volume of the Great Salt Lake. The decadal variations correspond to a low-frequency shifting of storm tracks which influence winter precipitation and explain nearly 18% of the interannual and longer-term variance in the record of monthly volume change. The secular trend accounts for a more modest approximately 1.5% of the variance.

Controlling Factors of the Surface Energy and Water Balances in cities located in cold climate regions

NASA Astrophysics Data System (ADS)

Järvi, L.; Grimmond, S. B.; Christen, A.; McFadden, J. P.; Strachan, I. B.

2016-12-01

Urban effects on climate are often pronounced in winter due to large anthropogenic heat releases and differences in snow cover between urban and surrounding rural areas. In this study, we simulate energy and water balances in cities characterized by cold winter climates with snow. Eleven urban sites from Helsinki (Finland), Basel (Switzerland), Montreal (Canada) and Minneapolis (USA) are analysed. The sites were selected based on the availability of either measured turbulent fluxes (from eddy covariance) or surface runoff to be used for model evaluation. The sites vary with respect to land cover fractions, irrigation habits and population densities. For example, the plan area fraction of impervious surface varies from 5% in Minneapolis to 84% in Basel. To simulate urban energy and water balances, we use the Surface Urban Energy and Water balance Scheme (SUEWS) model, which has been designed to minimize the number of required input variables and model parameters. For each site, the model is run in an offline mode using measured hourly meteorological data with a time step of 5-min. As the modelled time periods range from one (Basel) to 7.5 years (Helsinki), a wide range of meteorological conditions occur. Our results show how both evaporation and surface runoff are highly dependent on the fraction of impervious surface cover (r > |0.8|) during snow-free periods. However, high year-to-year variability in simulated evaporation and runoff indicates that climatological factors are also important. In winter, the amount and duration of snow cover become import controlling factor in determining the two components of water balance. The shorter the snow cover period is, the larger the cumulative runoff tends to be. Thus, our results suggest that warmer winters with less snow will increase the stress on drainage systems and modify the urban ecosystem via changes in evaporation and Bowen ratio. Also, our results indicate that simply using the fraction of impervious or pervious surfaces when estimating the surface runoff at different sites is not sufficient, but rather inter-annual variability in climatology also needs to be considered.

A 305-year continuous monthly rainfall series for the island of Ireland (1711-2016)

NASA Astrophysics Data System (ADS)

Murphy, Conor; Broderick, Ciaran; Burt, Timothy P.; Curley, Mary; Duffy, Catriona; Hall, Julia; Harrigan, Shaun; Matthews, Tom K. R.; Macdonald, Neil; McCarthy, Gerard; McCarthy, Mark P.; Mullan, Donal; Noone, Simon; Osborn, Timothy J.; Ryan, Ciara; Sweeney, John; Thorne, Peter W.; Walsh, Seamus; Wilby, Robert L.

2018-03-01

A continuous 305-year (1711-2016) monthly rainfall series (IoI_1711) is created for the Island of Ireland. The post 1850 series draws on an existing quality assured rainfall network for Ireland, while pre-1850 values come from instrumental and documentary series compiled, but not published by the UK Met Office. The series is evaluated by comparison with independent long-term observations and reconstructions of precipitation, temperature and circulation indices from across the British-Irish Isles. Strong decadal consistency of IoI_1711 with other long-term observations is evident throughout the annual, boreal spring and autumn series. Annually, the most recent decade (2006-2015) is found to be the wettest in over 300 years. The winter series is probably too dry between the 1740s and 1780s, but strong consistency with other long-term observations strengthens confidence from 1790 onwards. The IoI_1711 series has remarkably wet winters during the 1730s, concurrent with a period of strong westerly airflow, glacial advance throughout Scandinavia and near unprecedented warmth in the Central England Temperature record - all consistent with a strongly positive phase of the North Atlantic Oscillation. Unusually wet summers occurred in the 1750s, consistent with proxy (tree-ring) reconstructions of summer precipitation in the region. Our analysis shows that inter-decadal variability of precipitation is much larger than previously thought, while relationships with key modes of climate variability are time-variant. The IoI_1711 series reveals statistically significant multi-centennial trends in winter (increasing) and summer (decreasing) seasonal precipitation. However, given uncertainties in the early winter record, the former finding should be regarded as tentative. The derived record, one of the longest continuous series in Europe, offers valuable insights for understanding multi-decadal and centennial rainfall variability in Ireland, and provides a firm basis for benchmarking other long-term records and reconstructions of past climate. Correlation of Irish rainfall with other parts of Europe increases the utility of the series for understanding historical climate in further regions.

Nonlinear effects of climate and density in the dynamics of a fluctuating population of reindeer.

PubMed

Tyler, Nicholas J C; Forchhammer, Mads C; Øritsland, Nils Are

2008-06-01

Nonlinear and irregular population dynamics may arise as a result of phase dependence and coexistence of multiple attractors. Here we explore effects of climate and density in the dynamics of a highly fluctuating population of wild reindeer (Rangifer tarandus platyrhynchus) on Svalbard observed over a period of 29 years. Time series analyses revealed that density dependence and the effects of local climate (measured as the degree of ablation [melting] of snow during winter) on numbers were both highly nonlinear: direct negative density dependence was found when the population was growing (Rt > 0) and during phases of the North Atlantic Oscillation (NAO) characterized by winters with generally high (1979-1995) and low (1996-2007) indices, respectively. A growth-phase-dependent model explained the dynamics of the population best and revealed the influence of density-independent processes on numbers that a linear autoregressive model missed altogether. In particular, the abundance of reindeer was enhanced by ablation during phases of growth (Rt > 0), an observation that contrasts with the view that periods of mild weather in winter are normally deleterious for reindeer owing to icing of the snowpack. Analyses of vital rates corroborated the nonlinearity described in the population time series and showed that both starvation mortality in winter and fecundity were nonlinearly related to fluctuations in density and the level of ablation. The erratic pattern of growth of the population of reindeer in Adventdalen seems, therefore, to result from a combination of the effects of nonlinear density dependence, strong density-dependent mortality, and variable density independence related to ablation in winter.

Measurement of inter- and intra-annual variability of landscape fire activity at a continental scale: the Australian case

NASA Astrophysics Data System (ADS)

Williamson, Grant J.; Prior, Lynda D.; Jolly, W. Matt; Cochrane, Mark A.; Murphy, Brett P.; Bowman, David M. J. S.

2016-03-01

Climate dynamics at diurnal, seasonal and inter-annual scales shape global fire activity, although difficulties of assembling reliable fire and meteorological data with sufficient spatio-temporal resolution have frustrated quantification of this variability. Using Australia as a case study, we combine data from 4760 meteorological stations with 12 years of satellite-derived active fire detections to determine day and night time fire activity, fire season start and end dates, and inter-annual variability, across 61 objectively defined climate regions in three climate zones (monsoon tropics, arid and temperate). We show that geographic patterns of landscape burning (onset and duration) are related to fire weather, resulting in a latitudinal gradient from the monsoon tropics in winter, through the arid zone in all seasons except winter, and then to the temperate zone in summer and autumn. Peak fire activity precedes maximum lightning activity by several months in all regions, signalling the importance of human ignitions in shaping fire seasons. We determined median daily McArthur forest fire danger index (FFDI50) for days and nights when fires were detected: FFDI50 varied substantially between climate zones, reflecting effects of fire management in the temperate zone, fuel limitation in the arid zone and abundance of flammable grasses in the monsoon tropical zone. We found correlations between the proportion of days when FFDI exceeds FFDI50 and the Southern Oscillation index across the arid zone during spring and summer, and Indian Ocean dipole mode index across south-eastern Australia during summer. Our study demonstrates that Australia has a long fire weather season with high inter-annual variability relative to all other continents, making it difficult to detect long term trends. It also provides a way of establishing robust baselines to track changes to fire seasons, and supports a previous conceptual model highlighting multi-temporal scale effects of climate in shaping continental-scale pyrogeography.

The influence of tropical heating displacements on the extratropical climate

NASA Technical Reports Server (NTRS)

Hou, Arthur Y.

1993-01-01

The hypothesis is advanced that a latitudinal shift in the tropical convective heating pattern can significantly alter temperatures in the extratropics. Results of a simplified general circulation model (GCM) show that the shift of a prescribed tropical heating toward the summer pole, on time scales longer than a few weeks, leads to a more intense cross-equatorial 'winter' Hadley circulation, enhanced upper-level tropical easterlies, and a slightly stronger subtropical winter jet, accompanied by warming at the winter middle and high latitudes as a result of increased dynamical heating. The indications are that there is a robust connection between the net dynamic heating in the extratropics and the implied changes in the subtropical wind shear resulting from adjustments in the Hadley circulation associated with convective heating displacements in the tropics. The implications are that (1) the low-frequency temporal variability in the Hadley circulation may play an important role in modulating wave transport in the winter extratropics, (2) the global climate may be sensitive to those processes that control deep cumulus convection in the tropics, and (3) systematic temperature biases in GCMs may be reduced by improving the tropical rainfall simulation.

Global climate change and reindeer: effects of winter weather on the autumn weight and growth of calves.

PubMed

Weladji, Robert B; Holand, Øystein

2003-07-01

Reindeer/caribou (Rangifer tarandus), which constitute a biological resource of vital importance for the physical and cultural survival of Arctic residents, and inhabit extremely seasonal environments, have received little attention in the global change debate. We investigated how body weight and growth rate of reindeer calves were affected by large-scale climatic variability [measured by the North Atlantic Oscillation (NAO) winter index] and density in one population in central Norway. Body weights of calves in summer and early winter, as well as their growth rate (summer to early winter), were significantly influenced by density and the NAO index when cohorts were in utero. Males were heavier and had higher absolute growth than females, but there was no evidence that preweaning condition of male and female calves were influenced differently by the NAO winter index. Increasing NAO index had a negative effect on calves' body weight and growth rate. Increasing density significantly reduced body weight and growth rate of calves, and accentuated the effect of the NAO winter index. Winters with a higher NAO index are thus severe for reindeer calves in this area and their effects are associated with nutritional stress experienced by the dams during pregnancy or immediately after calving. Moreover, increased density may enhance intra-specific competition and limits food available at the individual level within cohorts. We conclude that if the current pattern of global warming continues, with greater change occurring in northern latitudes and during winter as is predicted, reduced body weight of reindeer calves may be a consequence in areas where winters with a high NAO index are severe. This will likely have an effect on the livelihood of many northern indigenous peoples, both economically and culturally.

Climate change impacts on the conservation outlook of populations on the poleward periphery of species ranges: A case study of Canadian black-tailed prairie dogs (Cynomys ludovicianus).

PubMed

Stephens, Tara; Wilson, Sian C; Cassidy, Ffion; Bender, Darren; Gummer, David; Smith, Des H V; Lloyd, Natasha; McPherson, Jana M; Moehrenschlager, Axel

2018-02-01

Given climate change, species' climatically suitable habitats are increasingly expected to shift poleward. Some imperilled populations towards the poleward edge of their species' range might therefore conceivably benefit from climate change. Interactions between climate and population dynamics may be complex, however, with climate exerting effects both indirectly via influence over food availability and more directly, via effects on physiology and its implications for survival and reproduction. A thorough understanding of these interactions is critical for effective conservation management. We therefore examine the relationship between climate, survival and reproduction in Canadian black-tailed prairie dogs, a threatened keystone species in an imperilled ecosystem at the northern edge of the species' range. Our analyses considered 8 years of annual mark-recapture data (2007-2014) in relation to growing degree days, precipitation, drought status and winter severity, as well as year, sex, age and body mass. Survival was strongly influenced by the interaction of drought and body mass class, and winter temperature severity. Female reproductive status was associated with the interaction of growing degree days and growing season precipitation, with spring precipitation and with winter temperature severity. Results related to body mass suggested that climatic variables exerted their effects via regulation of food availability with potential linked effects of food quality, immunological and behavioural implications, and predation risk. Predictions of future increases in drought conditions in North America's grassland ecosystems have raised concerns for the outlook of Canadian black-tailed prairie dogs. Insights gained from the analyses, however, point to mitigating species management options targeted at decoupling the mechanisms by which climate exerts its negative influence. Our approach highlights the importance of understanding the interaction between climate and population dynamics in peripheral populations whose viability might ultimately determine their species' ability to track climatically suitable space. © 2017 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.

30,000 years of hydroclimatic variability in the coastal southwest United States: regional synthesis and forcings analysis.

NASA Astrophysics Data System (ADS)

Kirby, M. E.

2015-12-01

The coastal southwest United States is characterized by a winter dominated hydroclimate. Far from dependable, this region's supply of winter precipitation is highly variable and often characterized by hydrologic opposites - droughts and floods. Predicting future precipitation and hydrologic dynamics requires a paleoperspective. Here, we present an up-to-date synthesis of hydroclimatic variability over the past 30,000 years. A variety of terrestrial-based studies are examined and compared to understand patterns of regional hydroclimatic change. This comparison is extended into the San Joaquin Basin of California where future climate change will impact the region's agricultural stability and economy. Particularly interesting is the apparent role that Pacific sea surface temperatures (SSTs) play in modulating the region's hydroclimate over a variety of timescales. Are past periods of above average Pacific SSTs analogs for future global warming? If yes, the region might expect an increase in winter precipitation as SSTs rise in response to global warming. However, how this potential precipitation increase is manifest is unknown. For example, will the intensity of precipitation events increase and thus present increased flood hazards and diminished freshwater capture? Finally, we present evidence for changes in the source of winter precipitation over time as well as ecological responses to past hydrologic change.

Are winter and summer dormancy symmetrical seasonal adaptive strategies? The case of temperate herbaceous perennials

PubMed Central

Gillespie, Lauren M.; Volaire, Florence A.

2017-01-01

Background Dormancy in higher plants is an adaptive response enabling plant survival during the harshest seasons and has been more explored in woody species than in herbaceous species. Nevertheless, winter and summer shoot meristem dormancy are adaptive strategies that could play a major role in enhancing seasonal stress tolerance and resilience of widespread herbaceous plant communities. Scope This review outlines the symmetrical aspects of winter and summer dormancy in order to better understand plant adaptation to severe stress, and highlight research priorities in a changing climate. Seasonal dormancy is a good model to explore the growth–stress survival trade-off and unravel the relationships between growth potential and stress hardiness. Although photoperiod and temperature are known to play a crucial, though reversed, role in the induction and release of both types of dormancy, the thresholds and combined effects of these environmental factors remain to be identified. The biochemical compounds involved in induction or release in winter dormancy (abscisic acid, ethylene, sugars, cytokinins and gibberellins) could be a priority research focus for summer dormancy. To address these research priorities, herbaceous species, being more tractable than woody species, are excellent model plants for which both summer and winter dormancy have been clearly identified. Conclusions Summer and winter dormancy, although responding to inverse conditions, share many characteristics. This analogous nature can facilitate research as well as lead to insight into plant adaptations to extreme conditions and the evolution of phenological patterns of species and communities under climate change. The development of phenotypes showing reduced winter and/or enhanced summer dormancy may be expected and could improve adaptation to less predictable environmental stresses correlated with future climates. To this end, it is suggested to explore the inter- and intraspecific genotypic variability of dormancy and its plasticity according to environmental conditions to contribute to predicting and mitigating global warming. PMID:28087658

Statistical downscaling for winter streamflow in Douro River

NASA Astrophysics Data System (ADS)

Jesús Esteban Parra, María; Hidalgo Muñoz, José Manuel; García-Valdecasas-Ojeda, Matilde; Raquel Gámiz Fortis, Sonia; Castro Díez, Yolanda

2015-04-01

In this paper we have obtained climate change projections for winter flow of the Douro River in the period 2071-2100 by applying the technique of Partial Regression and various General Circulation Models of CMIP5. The streamflow data base used has been provided by the Center for Studies and Experimentation of Public Works, CEDEX. Series from gauing stations and reservoirs with less than 10% of missing data (filled by regression with well correlated neighboring stations) have been considered. The homogeneity of these series has been evaluated through the Pettit test and degree of human alteration by the Common Area Index. The application of these criteria led to the selection of 42 streamflow time series homogeneously distributed over the basin, covering the period 1951-2011. For these streamflow data, winter seasonal values were obtained by averaging the monthly values from January to March. Statistical downscaling models for the streamflow have been fitted using as predictors the main atmospheric modes of variability over the North Atlantic region. These modes have been obtained using winter sea level pressure data of the NCEP reanalysis, averaged for the months from December to February. Period 1951-1995 was used for calibration, while 1996-2011 period was used in validating the adjusted models. In general, these models are able to reproduce about 70% of the variability of the winter streamflow of the Douro River. Finally, the obtained statistical models have been applied to obtain projections for 2071-2100 period, using outputs from different CMIP5 models under the RPC8.5 scenario. The results for the end of the century show modest declines of winter streamflow in this river for most of the models. Keywords: Statistical downscaling, streamflow, Douro River, climate change. ACKNOWLEDGEMENTS This work has been financed by the projects P11-RNM-7941 (Junta de Andalucía-Spain) and CGL2013-48539-R (MINECO-Spain, FEDER).

Observed Differences between North American Snow Extent and Snow Depth Variability

NASA Astrophysics Data System (ADS)

Ge, Y.; Gong, G.

2006-12-01

Snow extent and snow depth are two related characteristics of a snowpack, but they need not be mutually consistent. Differences between these two variables at local scales are readily apparent. However at larger scales which interact with atmospheric circulation and climate, snow extent is typically the variable used, while snow depth is often assumed to be minor and/or mutually consistent compared to snow extent, though this is rarely verified. In this study, a new regional/continental-scale gridded dataset derived from field observations is utilized to quantitatively evaluate the relationship between snow extent and snow depth over North America. Various statistical methods are applied to assess the mutual consistency of monthly snow depth vs. snow extent, including correlations, composites and principal components. Results indicate that snow depth variations are significant in their own rights, and that depth and extent anomalies are largely unrelated, especially over broad high latitude regions north of the snowline. In the vicinity of the snowline, where precipitation and ablation can affect both snow extent and snow depth, the two variables vary concurrently, especially in autumn and spring. It is also found that deeper winter snow translates into larger snow-covered area in the subsequent spring/summer season, which suggests a possible influence of winter snow depth on summer climate. The observed lack of mutual consistency at continental/regional scales suggests that snowpack depth variations may be of sufficiently large magnitude, spatial scope and temporal duration to influence regional-hemispheric climate, in a manner unrelated to the more extensively studied snow extent variations.

Variability in lateral carbon export from four major tributaries in the Upper Mississippi River Basin

NASA Astrophysics Data System (ADS)

Stanimirova, R.; Arevalo, P. A.; Kaufmann, R.; Maus, V.; Lesiv, M.; Havlik, P.; Friedl, M. A.

2016-12-01

The combined pressures of climate change and shifting dietary preferences are creating an urgent need to improve understanding of how climate and land management are jointly affecting the sustainability of rangelands. In particular, our ability to effectively manage rangelands in a manner that satisfies increasing demand for meat and dairy while reducing environmental impact depends on the sensitivity of rangelands to perturbations from both climate (e.g., drought) and land use (e.g., grazing). To characterize the sensitivity of rangeland vegetation to variation in climate, we analyzed gridded time series of satellite and climate data at 0.5-degree spatial resolution from 2003 to 2016 for rangeland ecosystems in South America. We used panel regression and canonical correlation to analyze the relationship between time series of enhanced vegetation index (EVI) derived from NASA's Moderate Spatial Resolution Imaging Spectroradiometer (MODIS) and gridded precipitation and air temperature data from the University of East Anglia's Climate Research Unit. To quantify the degree to which livestock management explains geographic variation of EVI, we used global livestock distribution (FAO) and feed requirements data from the Global Biosphere Management Model (GLOBIOM). Because rangeland ecosystems are sensitive to changes in meteorological variables at different time scales, we evaluated the strength of coupling between anomalies in EVI and anomalies in temperature and standardized precipitation index (SPI) data at 1-6 month lags. Our results show statistically significant relationships between EVI and precipitation during summer, fall, and winter in both tropical and subtropical agroecological zones of South America. Further, lagged precipitation effects, which reflect memory in the system, explain significant variance in winter EVI anomalies. While precipitation emerges as the dominant driver of variability in rangeland greenness, we find evidence of a management-induced signal as well. Our modeling framework integrates satellite observation, meteorological data sets, and land use/cover change information to improve our capability to monitor and manage the long-term sustainability of rangelands.

Climate Drivers of Spatiotemporal Variability of Precipitation in the Source Region of Yangtze River

NASA Astrophysics Data System (ADS)

Du, Y.; Berndtsson, R.; An, D.; Yuan, F.

2017-12-01

Variability of precipitation regime has significant influence on the environment sustainability in the source region of Yangtze River, especially when the vegetation degradation and biodiversity reduction have already occurred. Understanding the linkage between variability of local precipitation and global teleconnection patterns is essential for water resources management. Based on physical reasoning, indices of the climate drivers can provide a practical way of predicting precipitation. Due to high seasonal variability of precipitation, climate drivers of the seasonal precipitation also varies. However, few reports have gone through the teleconnections between large scale patterns with seasonal precipitation in the source region of Yangtze River. The objectives of this study are therefore (1) assessment of temporal trend and spatial variability of precipitation in the source region of Yangtze River; (2) identification of climate indices with strong influence on seasonal precipitation anomalies; (3) prediction of seasonal precipitation based on revealed climate indices. Principal component analysis and Spearman rank correlation were used to detect significant relationships. A feed-forward artificial neural network(ANN) was developed to predict seasonal precipitation using significant correlated climate indices. Different influencing climate indices were revealed for precipitation in each season, with significant level and lag times. Significant influencing factors were selected to be the predictors for ANN model. With correlation coefficients between observed and simulated precipitation over 0.5, the results were eligible to predict the precipitation of spring, summer and winter using teleconnections, which can improve integrated water resources management in the source region of Yangtze River.

Northern pintail body condition during wet and dry winters in the Sacramento Valley, California

USGS Publications Warehouse

Miller, M.R.

1986-01-01

Body weights and carcass composition of male and female adult northern pintails (Anas acuta) were investigated in the Sacramento Valley, California, from August to March 1979-82. Pintails were lightweight, lean, and had reduced breast, leg, and heart muscles during August-September. Ducks steadily gained weight after arrival; and body, carcass (body wt minus feathers and gastrointestinal content), fat protein, and muscle weights peaked in October-November. Fat-free dry weight remained high but variable the rest of the winter, whereas body and carcass weight and fat content declined to lows in December or January, then increased again in February or March. Gizzard weights declined from early fall to March. Males were always heavier than females, but females were fatter (percentage) than males during mid-winter. Mid-winter body weight, carcass fat, and protein content were significantly (P < 0.01) lower in the dry winter of 1980-81 than in 2 wet winters (1979-80 and 1981-82). Changes in pintail body weight and composition during winter are probably adaptations to mild climate, predictable food supplies, and requirements for pair formation and molt.

Projecting the impact of climate change on phenology of winter wheat in northern Lithuania

NASA Astrophysics Data System (ADS)

Juknys, Romualdas; Velička, Rimantas; Kanapickas, Arvydas; Kriaučiūnienė, Zita; Masilionytė, Laura; Vagusevičienė, Ilona; Pupalienė, Rita; Klepeckas, Martynas; Sujetovienė, Gintarė

2017-10-01

Climate warming and a shift in the timing of phenological phases, which lead to changes in the duration of the vegetation period may have an essential impact on the productivity of winter crops. The main purpose of this study is to examine climate change-related long-term (1961-2015) changes in the duration of both initial (pre-winter) and main (post-winter) winter wheat vegetation seasons and to present the projection of future phenological changes until the end of this century. Delay and shortening of pre-winter vegetation period, as well as the advancement and slight extension of the post-winter vegetation period, resulted in the reduction of whole winter wheat vegetation period by more than 1 week over the investigated 55 years. Projected changes in the timing of phenological phases which define limits of a main vegetation period differ essentially from the observed period. According to pessimistic (Representative Concentration Pathways 8.5) scenario, the advancement of winter wheat maturity phase by almost 30 days and the shortening of post-winter vegetation season by 15 days are foreseen for a far (2071-2100) projection. An increase in the available chilling amount is specific not only to the investigated historical period (1960-2015) but also to the projected period according to the climate change scenarios of climate warming for all three projection periods. Consequently, the projected climate warming does not pose a threat of plant vernalization shortage in the investigated geographical latitudes.

Impacts of Model Bias on the Climate Change Signal and Effects of Weighted Ensembles of Regional Climate Model Simulations: A Case Study over Southern Québec, Canada

DOE PAGES

Eum, Hyung-Il; Gachon, Philippe; Laprise, René

2016-01-01

This study examined the impact of model biases on climate change signals for daily precipitation and for minimum and maximum temperatures. Through the use of multiple climate scenarios from 12 regional climate model simulations, the ensemble mean, and three synthetic simulations generated by a weighting procedure, we investigated intermodel seasonal climate change signals between current and future periods, for both median and extreme precipitation/temperature values. A significant dependence of seasonal climate change signals on the model biases over southern Québec in Canada was detected for temperatures, but not for precipitation. This suggests that the regional temperature change signal is affectedmore » by local processes. Seasonally, model bias affects future mean and extreme values in winter and summer. In addition, potentially large increases in future extremes of temperature and precipitation values were projected. For three synthetic scenarios, systematically less bias and a narrow range of mean change for all variables were projected compared to those of climate model simulations. In addition, synthetic scenarios were found to better capture the spatial variability of extreme cold temperatures than the ensemble mean scenario. Finally, these results indicate that the synthetic scenarios have greater potential to reduce the uncertainty of future climate projections and capture the spatial variability of extreme climate events.« less

Impacts of Model Bias on the Climate Change Signal and Effects of Weighted Ensembles of Regional Climate Model Simulations: A Case Study over Southern Québec, Canada

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eum, Hyung-Il; Gachon, Philippe; Laprise, René

This study examined the impact of model biases on climate change signals for daily precipitation and for minimum and maximum temperatures. Through the use of multiple climate scenarios from 12 regional climate model simulations, the ensemble mean, and three synthetic simulations generated by a weighting procedure, we investigated intermodel seasonal climate change signals between current and future periods, for both median and extreme precipitation/temperature values. A significant dependence of seasonal climate change signals on the model biases over southern Québec in Canada was detected for temperatures, but not for precipitation. This suggests that the regional temperature change signal is affectedmore » by local processes. Seasonally, model bias affects future mean and extreme values in winter and summer. In addition, potentially large increases in future extremes of temperature and precipitation values were projected. For three synthetic scenarios, systematically less bias and a narrow range of mean change for all variables were projected compared to those of climate model simulations. In addition, synthetic scenarios were found to better capture the spatial variability of extreme cold temperatures than the ensemble mean scenario. Finally, these results indicate that the synthetic scenarios have greater potential to reduce the uncertainty of future climate projections and capture the spatial variability of extreme climate events.« less

Dynamics of the Disrupted 2015-16 Quasi-Biennial Oscillation.

PubMed

Coy, Lawrence; Newman, Paul A; Pawson, Steven; Lait, Leslie R

2017-08-01

A significant disruption of the Quasi-Biennial Oscillation (QBO) occurred during the Northern Hemisphere (NH) winter of 2015-16. Since the QBO is the major wind variability source in the tropical lower stratosphere and influences the rate of ascent of air entering the stratosphere, understanding the cause of this singular disruption may provide new insights into the variability and sensitivity of the global climate system. Here we examine this disruptive event using global reanalysis winds and temperatures from 1980-2016. Results reveal record maxima in tropical horizontal momentum fluxes and wave forcing of the tropical zonal mean zonal wind over the NH 2015-16 winter. The Rossby waves responsible for these record tropical values appear to originate in the NH and were focused strongly into the tropics at the 40 hPa level. Two additional NH winters, 1987-88 and 2010-11 were also found to have large, tropical lower stratosphere, momentum flux divergences; however, the QBO westerlies did not change to easterlies in those cases.

North Atlantic sub-decadal variability in climate models

NASA Astrophysics Data System (ADS)

Reintges, Annika; Martin, Thomas; Latif, Mojib; Park, Wonsun

2017-04-01

The North Atlantic Oscillation (NAO) is the dominant variability mode for the winter climate of the North Atlantic sector. During a positive (negative) NAO phase, the sea level pressure (SLP) difference between the subtropical Azores high and the subpolar Icelandic low is anomalously strong (weak). This affects, for example, temperature, precipitation, wind, and surface heat flux over the North Atlantic, and over large parts of Europe. In observations we find enhanced sub-decadal variability of the NAO index that goes along with a dipolar sea surface temperature (SST) pattern. The corresponding SLP and SST patterns are reproduced in a control experiment of the Kiel Climate Model (KCM). Large-scale air-sea interaction is suggested to be essential for the North Atlantic sub-decadal variability in the KCM. The Atlantic Meridional Overturning Circulation (AMOC) plays a key role, setting the timescale of the variability by providing a delayed negative feedback to the NAO. The interplay of the NAO and the AMOC on the sub-decadal timescale is further investigated in the CMIP5 model ensemble. For example, the average CMIP5 model AMOC pattern associated with sub-decadal variability is characterized by a deep-reaching dipolar structure, similar to the KCM's sub-decadal AMOC variability pattern. The results suggest that dynamical air-sea interactions are crucial to generate enhanced sub-decadal variability in the North Atlantic climate.

Effects of climate change on soil moisture over China from 1960-2006

USGS Publications Warehouse

Zhu, Q.; Jiang, H.; Liu, J.

2009-01-01

Soil moisture is an important variable in the climate system and it has sensitive impact on the global climate. Obviously it is one of essential components in the climate change study. The Integrated Biosphere Simulator (IBIS) is used to evaluate the spatial and temporal patterns of soil moisture across China under the climate change conditions for the period 1960-2006. Results show that the model performed better in warm season than in cold season. Mean errors (ME) are within 10% for all the months and root mean squared errors (RMSE) are within 10% except winter season. The model captured the spatial variability higher than 50% in warm seasons. Trend analysis based on the Mann-Kendall method indicated that soil moisture in most area of China is decreased especially in the northern China. The areas with significant increasing trends in soil moisture mainly locate at northwestern China and small areas in southeastern China and eastern Tibet plateau. ?? 2009 IEEE.

Effects of adjusting cropping systems on utilization efficiency of climatic resources in Northeast China under future climate scenarios

NASA Astrophysics Data System (ADS)

Guo, Jianping; Zhao, Junfang; Xu, Yanhong; Chu, Zheng; Mu, Jia; Zhao, Qian

Quantitatively evaluating the effects of adjusting cropping systems on the utilization efficiency of climatic resources under climate change is an important task for assessing food security in China. To understand these effects, we used daily climate variables obtained from the regional climate model RegCM3 from 1981 to 2100 under the A1B scenario and crop observations from 53 agro-meteorological experimental stations from 1981 to 2010 in Northeast China. Three one-grade zones of cropping systems were divided by heat, water, topography and crop-type, including the semi-arid areas of the northeast and northwest (III), the one crop area of warm-cool plants in semi-humid plain or hilly regions of the northeast (IV), and the two crop area in irrigated farmland in the Huanghuaihai Plain (VI). An agro-ecological zone model was used to calculate climatic potential productivities. The effects of adjusting cropping systems on climate resource utilization in Northeast China under the A1B scenario were assessed. The results indicated that from 1981 to 2100 in the III, IV and VI areas, the planting boundaries of different cropping systems in Northeast China obviously shifted toward the north and the east based on comprehensively considering the heat and precipitation resources. However, due to high temperature stress, the climatic potential productivity of spring maize was reduced in the future. Therefore, adjusting the cropping system is an effective way to improve the climatic potential productivity and climate resource utilization. Replacing the one crop in one year model (spring maize) by the two crops in one year model (winter wheat and summer maize) significantly increased the total climatic potential productivity and average utilization efficiencies. During the periods of 2011-2040, 2041-2070 and 2071-2100, the average total climatic potential productivities of winter wheat and summer maize increased by 9.36%, 11.88% and 12.13% compared to that of spring maize, respectively. Additionally, compared with spring maize, the average utilization efficiencies of thermal resources of winter wheat and summer maize dramatically increased by 9.2%, 12.1% and 12.0%, respectively. The increases in the average utilization efficiencies of precipitation resources of winter wheat and summer maize were 1.78 kg hm-2 mm-1, 2.07 kg hm-2 mm-1 and 1.92 kg hm-2 mm-1 during 2011-2040, 2041-2070 and 2071-2100, respectively. Our findings highlight that adjusting cropping systems can dominantly contribute to utilization efficiency increases of agricultural climatic resources in Northeast China in the future.

Understanding the Seasonal Greenness Trends and Controls in South Asia Using Satellite Based Observations

NASA Astrophysics Data System (ADS)

Sarmah, S.; Jia, G.; Zhang, A.; Singha, M.

2017-12-01

South Asia (SA) is one of the most remarkable regions in changing vegetation greenness along with its major expansion of agricultural activity, especially irrigated farming. However, SA is predicted to be a vulnerable agricultural regions to future climate changes. The influence of monsoon climate on the seasonal trends and anomalies of vegetation greenness are not well understood in the region which can provide valuable information about climate-ecosystem interaction. This study analyzed the spatio-temporal patterns of seasonal vegetation trends and variability using satellite vegetation indices (VI) including AVHRR Normalized Difference Vegetation Index (NDVI) (1982-2013) and MODIS Enhanced Vegetation Index (EVI) (2000-2013) in summer monsoon (SM) (June-Sept) and winter monsoon (WM) (Dec-Apr) seasons among irrigated cropland (IC), rainfed cropland (RC) and natural vegetation (NV). Seasonal VI variations with climatic factors (precipitation and temperature) and LULC changes have been investigated to identify the forcings behind the vegetation trends and variability. We found that major greening occurred in the last three decades due to the increase in IC productivity noticeably in WM, however, recent (2000-2013) greening trends were lower than the previous decades (1982-1999) in both the IC and RC indicating the stresses on them. The browning trends, mainly concentrated in NV areas were prominent during WM and rigorous since 2000, confirmed from the moderate resolution EVI and LULC datasets. Winter time maximal temperature had been increasing tremendously whereas precipitation trend was not significant over SA. Both the climate variability and LULC changes had integrated effects on the vegetation changes in NV areas specifically in hilly regions. However, LULC impact was intensified since 2000, mostly in north east India. This study also revealed a distinct seasonal variation in spatial distribution of correlation between VI's and climate anomalies over SA. Concluding, so far SA has managed to get a decent productivity over croplands due to the advanced cultivation techniques which likely to be at risk under future warming climate. Also NV areas of SA are in constant threat from the anthropogenic activities and climate changes.

Historical trend in river ice thickness and coherence in hydroclimatological trends in Maine

USGS Publications Warehouse

Huntington, T.G.; Hodgkins, G.A.; Dudley, R.W.

2003-01-01

We analyzed long-term records of ice thickness on the Piscataquis River in central Maine and air temperature in Maine to determine whether there were temporal trends that were associated with climate warming. The trend in ice thickness was compared and correlated with regional time series of winter air temperature, heating degree days (HDD), date of river ice-out, seasonal center-of-volume date (SCVD) (date on which half of the stream runoff volume during the period 1 Jan. to 31 May has occurred), water temperature, and lake ice-out date. All of these variables except lake ice-out date showed significant temporal trends during the 20th century. Average ice thickness around 28 February decreased by about 23 cm from 1912 to 2001. Over the period 1900 to 1999, winter air temperature increased by 1.7??C and HDD decreased by about 7.5%. Final ice-out date on the Piscataquis River occurred earlier (advanced), by 0.21 days yr-1 over the period 1931 to 2002, and the SCVD advanced by 0.11 days yr-1 over the period 1903 to 2001. Ice thickness was significantly correlated (P-value < 0.01) with winter air temperature, HDD, river ice-out, and SCVD. These systematic temporal trends in multiple hydrologic indicator variables indicate a coherent response to climate forcing.

Potential Influence of Arctic Sea Ice to the Inter-annual Variations of East Asian Spring Precipitation

NASA Astrophysics Data System (ADS)

Li, Xinxin; Wu, Zhiwei; Li, Yanjie

2016-04-01

Arctic sea ice (ASI) and its potential climatic impacts have received increasing attention during the past decades, yet the relevant mechanisms are far from being understood, particularly on how anomalous ASI affects climate in midlatitudes. The spring precipitation takes up as much as 30% of the annual total and has significant influences to agriculture in East Asia. Here, observed evidence and numerical experiment results manifest that the ASI variability in the Norwegian Sea and the Barents Sea in preceding winter is intimately connected with interannual variations of the East Asian spring precipitation (EAP). The former can explain about 14% of the total variances of the latter. The ASI anomalies persist from winter through the ensuing spring and excite downstream tele-connections of a distinct Rossby wave train prevailing over the Eurasian continent. For the reduced ASI, such a wave train pattern is usually associated with an anomalous low pressure center over Mongolian Plateau, which accelerates the East Asian subtropical westerly jet. The intensified subtropical westerly jet, concurrent with lower-level convergence and upper-level divergence, enhances the local convection and consequently favors rich spring precipitation over East Asia. For the excessive ASI, the situation tends to be opposite. Given that seasonal prediction of the EAP remains a challenging issue, the winter ASI variability may provide another potential predictability source besides El Niño-Southern Oscillation.

Seasonal and interannual variability of the Mid-Holocene East Asian monsoon in coral δ18O records from the South China Sea

NASA Astrophysics Data System (ADS)

Sun, Donghuai; Gagan, Michael K.; Cheng, Hai; Scott-Gagan, Heather; Dykoski, Carolyn A.; Edwards, R. Lawrence; Su, Ruixia

2005-08-01

Understanding the full range of past monsoon variability, with reference to specific monsoon seasons, is essential to test coupled climate models and improve their predictive capabilities. We present a 54-year long, high-resolution skeletal oxygen isotope (δ18O) record extracted from a well-preserved, massive Porites sp. coral at Hainan Island, South China Sea, to investigate East Asian monsoon variability during summer and winter ∼4400 calendar yr ago. Analysis of modern coral δ18O confirms that Porites from Hainan Island are well positioned to record winter monsoon forcing of sea surface temperature (SST), as well as the influence of summer monsoon rainfall on sea surface salinity (SSS). The coral record for ∼4400 yr ago shows ∼9% amplification of the annual cycle of δ18O, in good agreement with coupled ocean-atmosphere models showing higher summer rainfall (lower coral δ18O) and cooler winter SSTs (higher coral δ18O) in response to greater Northern Hemisphere insolation seasonality during the Middle Holocene. Mean SSTs in the South China Sea during the Mid-Holocene were within 0.5 °C of modern values, yet the mean δ18O for the fossil coral is ∼0.6‰ higher than that for the modern coral, suggesting that the δ18O of surface seawater was higher by at least ∼0.5‰, relative to modern values. The 18O-enrichment is likely to be driven by greater advection of moisture towards the Asian landmass, enhanced monsoon wind-induced evaporation and vertical mixing, and/or invigorated advection of saltier 18O-enriched Pacific water into the relatively fresh South China Sea. The 18O-enrichment of the northern South China Sea ∼4400 yr ago contributes to mounting evidence for recent freshening of the tropical Western Pacific. Today, winter SST and summer SSS variability in the South China Sea reflect the interannual influence of ENSO and the biennial variability inherent to monsoon precipitation. Spectral analysis of winter SSTs ∼4400 yr ago reveals a strong ENSO cycle at 6.7 y, which is significantly longer than the average 3.6 y cycle observed since 1970. The results suggest that the influence of ENSO on winter SSTs in the South China Sea was well established by ∼4400 yr ago. However, spectral analysis of summer SSS ∼4400 yr ago shows no significant ENSO cycle, suggesting that teleconnections between ENSO and summer monsoon rainfall were restricted. Taken together, the results indicate marked differences in ENSO-monsoon interactions during the winter and summer monsoon seasons in the past. The fossil coral δ18O record also shows that the amplitude of interannual SST and SSS variability was stronger ∼4400 yr ago, despite ENSO variability being significantly weaker in the Pacific region. Thus it appears that the strengthened Mid-Holocene monsoon was sensitive to forces, other than ENSO, that acted as alternative drivers of interannual monsoon variability. If this is the case, greater interannual climate variability could accompany the strengthening of the Asian monsoon predicted to occur during the 21st century as transient greenhouse warming preferentially warms Eurasia, even if ENSO perturbations remain relatively stable.

Combined Spatio-Temporal Impacts of Climate and Longline Fisheries on the Survival of a Trans-Equatorial Marine Migrant

PubMed Central

Ramos, Raül; Granadeiro, José Pedro; Nevoux, Marie; Mougin, Jean-Louis; Dias, Maria Peixe; Catry, Paulo

2012-01-01

Predicting the impact of human activities and their derivable consequences, such as global warming or direct wildlife mortality, is increasingly relevant in our changing world. Due to their particular life history traits, long-lived migrants are amongst the most endangered and sensitive group of animals to these harming effects. Our ability to identify and quantify such anthropogenic threats in both breeding and wintering grounds is, therefore, of key importance in the field of conservation biology. Using long-term capture-recapture data (34 years, 4557 individuals) and year-round tracking data (4 years, 100 individuals) of a trans-equatorial migrant, the Cory’s shearwater (Calonectris diomedea), we investigated the impact of longline fisheries and climatic variables in both breeding and wintering areas on the most important demographic trait of this seabird, i.e. adult survival. Annual adult survival probability was estimated at 0.914±0.022 on average, declining throughout 1978–1999 but recovering during the last decade (2005–2011). Our results suggest that both the incidental bycatch associated with longline fisheries and high sea surface temperatures (indirectly linked to food availability; SST) increased mortality rates during the long breeding season (March-October). Shearwater survival was also negatively affected during the short non-breeding season (December-February) by positive episodes of the Southern Oscillation Index (SOI). Indirect negative effects of climate at both breeding (SST) and wintering grounds (SOI) had a greater impact on survival than longliner activity, and indeed these climatic factors are those which are expected to present more unfavourable trends in the future. Our work underlines the importance of considering both breeding and wintering habitats as well as precise schedules/phenology when assessing the global role of the local impacts on the dynamics of migratory species. PMID:22815833

A New Inter-Hemispheric Teleconnection Increases Predictability of Winter Precipitation in Southwestern US

NASA Astrophysics Data System (ADS)

Mamalakis, A.; Yu, J. Y.; Randerson, J. T.; AghaKouchak, A.; Foufoula-Georgiou, E.

2017-12-01

Early and reliable prediction of seasonal precipitation in the southwestern US (SWUS) remains a challenge with significant implications for the economy, water security and ecosystem management of the region. Traditional drivers of winter precipitation in the SWUS have been linked to the El Niño-Southern Oscillation (ENSO), decadal/multidecadal oscillations of the sea surface temperature in northern Pacific and Atlantic oceans, and persistent high-pressure ridges over the Gulf of Alaska. However, ENSO as well as other climate modes exhibit weak statistical relationships with precipitation and low predictability as lead time increases. Grounded on the hypothesis that still undiscovered relationships between large-scale atmosphere-ocean dynamics and SWUS precipitation might exist, here we followed a diagnostic approach by which instead of restricting ourselves to the established teleconnections, we analyzed systematically the correlation of global sea surface temperature (SST) and geopotential height (GPH) with winter precipitation amounts in all climatic divisions in the SWUS, for 1950-2015. Our results show that late-summer persistent SST and GPH anomalies in the subtropical southwestern Pacific are strongly connected with winter precipitation in most climatic divisions, exhibiting higher correlation values than ENSO, and thus increasing the potential for earlier and more accurate precipitation prediction. Cross validation and 30-year running average analysis starting in 1950 suggest an amplification of the detected teleconnections over the past three to four decades. The latter is most likely a result of the reported expansion of the tropics, which has started after the 1980s, and allows SST or GPH variability at lower latitudes to affect the meridional atmospheric circulation. Our work highlights the need to understand the dynamic nature of the coupled atmosphere-ocean system in a changing climate for improving future predictions of regional precipitation.

Winter climate change and coastal wetland foundation species: salt marshes vs. mangrove forests in the southeastern United States

USGS Publications Warehouse

Osland, Michael J.; Day, Richard H.; Doyle, Thomas W.; Enwright, Nicholas

2013-01-01

We live in an era of unprecedented ecological change in which ecologists and natural resource managers are increasingly challenged to anticipate and prepare for the ecological effects of future global change. In this study, we investigated the potential effect of winter climate change upon salt marsh and mangrove forest foundation species in the southeastern United States. Our research addresses the following three questions: (1) What is the relationship between winter climate and the presence and abundance of mangrove forests relative to salt marshes; (2) How vulnerable are salt marshes to winter climate change-induced mangrove forest range expansion; and (3) What is the potential future distribution and relative abundance of mangrove forests under alternative winter climate change scenarios? We developed simple winter climate-based models to predict mangrove forest distribution and relative abundance using observed winter temperature data (1970–2000) and mangrove forest and salt marsh habitat data. Our results identify winter climate thresholds for salt marsh–mangrove forest interactions and highlight coastal areas in the southeastern United States (e.g., Texas, Louisiana, and parts of Florida) where relatively small changes in the intensity and frequency of extreme winter events could cause relatively dramatic landscape-scale ecosystem structural and functional change in the form of poleward mangrove forest migration and salt marsh displacement. The ecological implications of these marsh-to-mangrove forest conversions are poorly understood, but would likely include changes for associated fish and wildlife populations and for the supply of some ecosystem goods and services.

North Atlantic climate variability: The role of the North Atlantic Oscillation

NASA Astrophysics Data System (ADS)

Hurrell, James W.; Deser, Clara

2009-08-01

Marine ecosystems are undergoing rapid change at local and global scales. To understand these changes, including the relative roles of natural variability and anthropogenic effects, and to predict the future state of marine ecosystems requires quantitative understanding of the physics, biogeochemistry and ecology of oceanic systems at mechanistic levels. Central to this understanding is the role played by dominant patterns or "modes" of atmospheric and oceanic variability, which orchestrate coherent variations in climate over large regions with profound impacts on ecosystems. We review the spatial structure of extratropical climate variability over the Northern Hemisphere and, specifically, focus on modes of climate variability over the extratropical North Atlantic. A leading pattern of weather and climate variability over the Northern Hemisphere is the North Atlantic Oscillation (NAO). The NAO refers to a redistribution of atmospheric mass between the Arctic and the subtropical Atlantic, and swings from one phase to another producing large changes in surface air temperature, winds, storminess and precipitation over the Atlantic as well as the adjacent continents. The NAO also affects the ocean through changes in heat content, gyre circulations, mixed layer depth, salinity, high latitude deep water formation and sea ice cover. Thus, indices of the NAO have become widely used to document and understand how this mode of variability alters the structure and functioning of marine ecosystems. There is no unique way, however, to define the NAO. Several approaches are discussed including both linear (e.g., principal component analysis) and nonlinear (e.g., cluster analysis) techniques. The former, which have been most widely used, assume preferred atmospheric circulation states come in pairs, in which anomalies of opposite polarity have the same spatial structure. In contrast, nonlinear techniques search for recurrent patterns of a specific amplitude and sign. They reveal, for instance, spatial asymmetries between different phases of the NAO that are likely important for ecological studies. It also follows that there is no universally accepted index to describe the temporal evolution of the NAO. Several of the most common measures are presented and compared. All reveal that there is no preferred time scale of variability for the NAO: large changes occur from one winter to the next and from one decade to the next. There is also a large amount of within-season variability in the patterns of atmospheric circulation of the North Atlantic, so that most winters cannot be characterized solely by a canonical NAO structure. A better understanding of how the NAO responds to external forcing, including sea surface temperature changes in the tropics, stratospheric influences, and increasing greenhouse gas concentrations, is crucial to the current debate on climate variability and change.

North Atlantic climate variability: The role of the North Atlantic Oscillation

NASA Astrophysics Data System (ADS)

Hurrell, James W.; Deser, Clara

2010-02-01

Marine ecosystems are undergoing rapid change at local and global scales. To understand these changes, including the relative roles of natural variability and anthropogenic effects, and to predict the future state of marine ecosystems requires quantitative understanding of the physics, biogeochemistry and ecology of oceanic systems at mechanistic levels. Central to this understanding is the role played by dominant patterns or "modes" of atmospheric and oceanic variability, which orchestrate coherent variations in climate over large regions with profound impacts on ecosystems. We review the spatial structure of extratropical climate variability over the Northern Hemisphere and, specifically, focus on modes of climate variability over the extratropical North Atlantic. A leading pattern of weather and climate variability over the Northern Hemisphere is the North Atlantic Oscillation (NAO). The NAO refers to a redistribution of atmospheric mass between the Arctic and the subtropical Atlantic, and swings from one phase to another producing large changes in surface air temperature, winds, storminess and precipitation over the Atlantic as well as the adjacent continents. The NAO also affects the ocean through changes in heat content, gyre circulations, mixed layer depth, salinity, high latitude deep water formation and sea ice cover. Thus, indices of the NAO have become widely used to document and understand how this mode of variability alters the structure and functioning of marine ecosystems. There is no unique way, however, to define the NAO. Several approaches are discussed including both linear (e.g., principal component analysis) and nonlinear (e.g., cluster analysis) techniques. The former, which have been most widely used, assume preferred atmospheric circulation states come in pairs, in which anomalies of opposite polarity have the same spatial structure. In contrast, nonlinear techniques search for recurrent patterns of a specific amplitude and sign. They reveal, for instance, spatial asymmetries between different phases of the NAO that are likely important for ecological studies. It also follows that there is no universally accepted index to describe the temporal evolution of the NAO. Several of the most common measures are presented and compared. All reveal that there is no preferred time scale of variability for the NAO: large changes occur from one winter to the next and from one decade to the next. There is also a large amount of within-season variability in the patterns of atmospheric circulation of the North Atlantic, so that most winters cannot be characterized solely by a canonical NAO structure. A better understanding of how the NAO responds to external forcing, including sea surface temperature changes in the tropics, stratospheric influences, and increasing greenhouse gas concentrations, is crucial to the current debate on climate variability and change.

Sustainability of winter tourism in a changing climate over Kashmir Himalaya.

PubMed

Dar, Reyaz Ahmad; Rashid, Irfan; Romshoo, Shakil Ahmad; Marazi, Asif

2014-04-01

Mountain areas are sensitive to climate change. Implications of climate change can be seen in less snow, receding glaciers, increasing temperatures, and decreasing precipitation. Climate change is also a severe threat to snow-related winter sports such as skiing, snowboarding, and cross-country skiing. The change in climate will put further pressure on the sensitive environment of high mountains. Therefore, in this study, an attempt has been made to know the impact of climate change on the snow precipitation, water resources, and winter tourism in the two famous tourist resorts of the Kashmir Valley. Our findings show that winters are getting prolonged with little snow falls on account of climate change. The average minimum and maximum temperatures are showing statistically significant increasing trends for winter months. The precipitation is showing decreasing trends in both the regions. A considerable area in these regions remains under the snow and glacier cover throughout the year especially during the winter and spring seasons. However, time series analysis of LandSat MODIS images using Normalized Difference Snow Index shows a decreasing trend in snow cover in both the regions from past few years. Similarly, the stream discharge, comprising predominantly of snow- and glacier-melt, is showing a statistically significant declining trend despite the melting of these glaciers. The predicted futuristic trends of temperature from Predicting Regional Climates for Impact Studies regional climate model are showing an increase which may enhance snow-melting in the near future posing a serious threat to the sustainability of winter tourism in the region. Hence, it becomes essential to monitor the changes in temperature and snow cover depletion in these basins in order to evaluate their effect on the winter tourism and water resources in the region.

Factorial inferential grid grouping and representativeness analysis for a systematic selection of representative grids

NASA Astrophysics Data System (ADS)

Cheng, Guanhui; Huang, Guohe; Dong, Cong; Xu, Ye; Yao, Yao

2017-08-01

A factorial inferential grid grouping and representativeness analysis (FIGGRA) approach is developed to achieve a systematic selection of representative grids in large-scale climate change impact assessment and adaptation (LSCCIAA) studies and other fields of Earth and space sciences. FIGGRA is applied to representative-grid selection for temperature (Tas) and precipitation (Pr) over the Loess Plateau (LP) to verify methodological effectiveness. FIGGRA is effective at and outperforms existing grid-selection approaches (e.g., self-organizing maps) in multiple aspects such as clustering similar grids, differentiating dissimilar grids, and identifying representative grids for both Tas and Pr over LP. In comparison with Pr, the lower spatial heterogeneity and higher spatial discontinuity of Tas over LP lead to higher within-group similarity, lower between-group dissimilarity, lower grid grouping effectiveness, and higher grid representativeness; the lower interannual variability of the spatial distributions of Tas results in lower impacts of the interannual variability on the effectiveness of FIGGRA. For LP, the spatial climatic heterogeneity is the highest in January for Pr and in October for Tas; it decreases from spring, autumn, summer to winter for Tas and from summer, spring, autumn to winter for Pr. Two parameters, i.e., the statistical significance level (α) and the minimum number of grids in every climate zone (Nmin), and their joint effects are significant for the effectiveness of FIGGRA; normalization of a nonnormal climate-variable distribution is helpful for the effectiveness only for Pr. For FIGGRA-based LSCCIAA studies, a low value of Nmin is recommended for both Pr and Tas, and a high and medium value of α for Pr and Tas, respectively.

Arctic sea ice trends, variability and implications for seasonal ice forecasting.

PubMed

Serreze, Mark C; Stroeve, Julienne

2015-07-13

September Arctic sea ice extent over the period of satellite observations has a strong downward trend, accompanied by pronounced interannual variability with a detrended 1 year lag autocorrelation of essentially zero. We argue that through a combination of thinning and associated processes related to a warming climate (a stronger albedo feedback, a longer melt season, the lack of especially cold winters) the downward trend itself is steepening. The lack of autocorrelation manifests both the inherent large variability in summer atmospheric circulation patterns and that oceanic heat loss in winter acts as a negative (stabilizing) feedback, albeit insufficient to counter the steepening trend. These findings have implications for seasonal ice forecasting. In particular, while advances in observing sea ice thickness and assimilating thickness into coupled forecast systems have improved forecast skill, there remains an inherent limit to predictability owing to the largely chaotic nature of atmospheric variability. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Soil Moisture and Snow Cover: Active or Passive Elements of Climate?

NASA Technical Reports Server (NTRS)

Oglesby, Robert J.; Marshall, Susan; Erickson, David J., III; Robertson, Franklin R.; Roads, John O.; Arnold, James E. (Technical Monitor)

2002-01-01

A key question in the study of the hydrologic cycle is the extent to which surface effects such as soil moisture and snow cover are simply passive elements or whether they can affect the evolution of climate on seasonal and longer time scales. We have constructed ensembles of predictability studies using the NCAR CCM3 in which we compared the relative roles of initial surface and atmospheric conditions over the central and western U.S. in determining the subsequent evolution of soil moisture and of snow cover. We have also made sensitivity studies with exaggerated soil moisture and snow cover anomalies in order to determine the physical processes that may be important. Results from simulations with realistic soil moisture anomalies indicate that internal climate variability may be the strongest factor, with some indication that the initial atmospheric state is also important. The initial state of soil moisture does not appear important, a result that held whether simulations were started in late winter or late spring. Model runs with exaggerated soil moisture reductions (near-desert conditions) showed a much larger effect, with warmer surface temperatures, reduced precipitation, and lower surface pressures; the latter indicating a response of the atmospheric circulation. These results suggest the possibility of a threshold effect in soil moisture, whereby an anomaly must be of a sufficient size before it can have a significant impact on the atmospheric circulation and hence climate. Results from simulations with realistic snow cover anomalies indicate that the time of year can be crucial. When introduced in late winter, these anomalies strongly affected the subsequent evolution of snow cover. When introduced in early winter, however, little or no effect is seen on the subsequent snow cover. Runs with greatly exaggerated initial snow cover indicate that the high reflectively of snow is the most important process by which snow cover cart impact climate, through lower surface temperatures and increased surface pressures. In early winter, the amount of solar radiation is very small and so this albedo effect is inconsequential while in late winter, with the sun higher in the sky and period of daylight longer, the effect is much stronger.

Mid- to late Holocene climate-driven regime shifts inferred from diatom, ostracod and stable isotope records from Lake Son Kol (Central Tian Shan, Kyrgyzstan)

NASA Astrophysics Data System (ADS)

Schwarz, Anja; Turner, Falko; Lauterbach, Stefan; Plessen, Birgit; Krahn, Kim J.; Glodniok, Sven; Mischke, Steffen; Stebich, Martina; Witt, Roman; Mingram, Jens; Schwalb, Antje

2017-12-01

Arid Central Asia represents a key region for understanding climate variability and interactions in the Northern Hemisphere. Patterns and mechanisms of Holocene climate change in arid Central Asia are, however, only partially understood. Multi-proxy data combining diatom, ostracod, sedimentological, geochemical and stable isotope analyses from a ca. 6000-year-old lake sediment core from Son Kol (Central Kyrgyzstan) show distinct and repeated changes in species assemblages. Diatom- and ostracod-inferred conductivity shifts between meso-euhaline and freshwater conditions suggest water balance and regime shifts. Organism-derived data are corroborated by stable isotope, mineralogical and geochemical records, underlining that Son Kol was affected by strong lake level fluctuations of several meters. The δ13Ccarb/δ18Ocarb correlation shows repeated switchovers from a closed to an open lake system. From 6000 to 3800 and 3250 to 1950 cal. yr BP, Son Kol was a closed basin lake with higher conductivities, increased nutrient availability and a water level located below the modern outflow. Son Kol became again a hydrologically open lake at 3800 and 1950 cal. yr BP. Comparisons to other local and regional paleoclimate records indicate that these regime shifts were largely controlled by changing intensity and position of the Westerlies and the Siberian Anticyclone that triggered changes in the amount of winter precipitation. A strong influence of the Westerlies ca. 5000-4400, 3800-3250 and since 1950 cal. yr BP enhanced the amount of precipitation during spring, autumn and winter, whereas cold and dry winters prevailed during phases with a strong Siberian Anticyclone and southward shifted Westerlies at ca. 6000-5000, 4400-3800 and 3250-1950 cal. yr BP. Similarities between variations in winter precipitation at Son Kol and records of the predominant NAO-mode further suggest a teleconnection between wet (dry) winter climate in Central Asia and a positive (negative) NAO-mode. Thus, this study identifies climate fluctuations as the main driver for hydrological regime shifts in Son Kol controlling physicochemical conditions and consequently causing abrupt species assemblage changes. This emphasizes the importance of multi-proxy approaches to identify triggers, thresholds and cascades of aquatic ecosystem transformations.

Mid-to-Late Holocene Hydrologic Variability in the Southeastern Mojave Desert Using Sediments from Ford Lake

NASA Astrophysics Data System (ADS)

Mayer, S. A.; Kirby, M. E.; Anderson, W. T., Jr.; Stout, C.; Palermo, J. A.

2015-12-01

The focal point of most lacustrine studies in the Mojave National Preserve (MNP) to date has been on lakes fed by the Mojave River. The source of the Mojave River is found on the northern flank of the San Bernardino Mountains. Consequently, the lakes that receive these waters are predominantly responding to the winter-only coastal southwest United States climate (e.g., Kirby et al., 2015 - Silver Lake); to a lesser degree, these lakes are also influenced by the Mojave's bimodal winter/summer climate. Ford Lake, located in the southeastern Mojave Desert is a small closed basin lake with its drainage basin located exclusively within the Mojave Desert. Therefore, sediment collected from Ford Lake contains a 100% Mojave-only climate signal. A 2.18 m sediment core was collected from the lake's depocenter in May 2015. Sediment analyses at 1 cm contiguous intervals include: magnetic susceptibility (MS), percent total organic matter, percent total carbonate content, and grain size analysis; C:N ratios, C and N isotope (δ13C and δ15N) analyses, and macrofossil counts are determined at 2 cm intervals. The site's age model is based on accelerator mass spectrometry (AMS) radiocarbon ages from discrete organic macrofossils or bulk organic carbon. To deconvolve the coastal climate, winter-only signal from the Mojave-only climate signal the data from Ford Lake will be compared to one Mojave River fed lake (Silver) and several southern California lakes (Lower Bear, Lake Elsinore, Dry Lake, and Zaca Lake). Our results will be analyzed in the context of climate forcings such as insolation and ocean - atmosphere dynamics.

Effects of Climatic Conditions and Management Practices on Agricultural Carbon and Water Budgets in the Inland Pacific Northwest USA

NASA Astrophysics Data System (ADS)

Chi, Jinshu; Waldo, Sarah; Pressley, Shelley N.; Russell, Eric S.; O'Keeffe, Patrick T.; Pan, William L.; Huggins, David R.; Stöckle, Claudio O.; Brooks, Erin S.; Lamb, Brian K.

2017-12-01

Cropland is an important land cover influencing global carbon and water cycles. Variability of agricultural carbon and water fluxes depends on crop species, management practices, soil characteristics, and climatic conditions. In the context of climate change, it is critical to quantify the long-term effects of these environmental drivers and farming activities on carbon and water dynamics. Twenty site-years of carbon and water fluxes covering a large precipitation gradient and a variety of crop species and management practices were measured in the inland Pacific Northwest using the eddy covariance method. The rain-fed fields were net carbon sinks, while the irrigated site was close to carbon neutral during the winter wheat crop years. Sites growing spring crops were either carbon sinks, sources, or neutral, varying with crops, rainfall zones, and tillage practices. Fluxes were more sensitive to variability in precipitation than temperature: annual carbon and water fluxes increased with the increasing precipitation while only respiration increased with temperature in the high-rainfall area. Compared to a nearby rain-fed site, irrigation improved winter wheat production but resulted in large losses of carbon and water to the atmosphere. Compared to conventional tillage, no-till had significantly lower respiration but resulted in slightly lower yields and water use efficiency over 4 years. Under future climate change, it is expected that more carbon fixation by crops and evapotranspiration would occur in a warmer and wetter environment.

Characterizing Climate Controls on Vegetation Seasonality in the North American Southwest

NASA Astrophysics Data System (ADS)

Fish, M. A.; Cook, B.; Smerdon, J. E.; Seager, R.; Williams, P.

2014-12-01

The North American Southwest, which extends from Colorado to southern Mexico and California to eastern Texas, encompasses a diversity of climates, elevations, and ecosystems. This region is expected to experience significant climatic change, and associated impacts, in the coming decades. To better understand the spatiotemporal variability of vegetation in the Southwest and the expected climatic controls on timing and spatial extend of vegetation growth, we compared GIMMS normalized difference vegetation index (NDVI, 1981-2011) against temperature and precipitation data. Spatial variations in vegetation seasonality and the timing of peak NDVI are linked to spatial variability in the precipitation regimes across the Southwest. Regions with spring NDVI peaks are dominated by winter precipitation, while late summer and fall peaks are in regions with significant summer precipitation driven by the North American Monsoon. Inter-annual variability in peak NDVI is positively correlated with precipitation and negatively correlated with temperature, with the largest correlation coefficients at one-month lags. The only significant long-term trends in NDVI are for northern Mexico, where agricultural productivity has been increasing over the last 30 years.

Climate change in our backyards: the reshuffling of North America's winter bird communities.

PubMed

Princé, Karine; Zuckerberg, Benjamin

2015-02-01

Much of the recent changes in North American climate have occurred during the winter months, and as result, overwintering birds represent important sentinels of anthropogenic climate change. While there is mounting evidence that bird populations are responding to a warming climate (e.g., poleward shifts) questions remain as to whether these species-specific responses are resulting in community-wide changes. Here, we test the hypothesis that a changing winter climate should favor the formation of winter bird communities dominated by warm-adapted species. To do this, we quantified changes in community composition using a functional index--the Community Temperature Index (CTI)--which measures the balance between low- and high-temperature dwelling species in a community. Using data from Project FeederWatch, an international citizen science program, we quantified spatiotemporal changes in winter bird communities (n = 38 bird species) across eastern North America and tested the influence of changes in winter minimum temperature over a 22-year period. We implemented a jackknife analysis to identify those species most influential in driving changes at the community level and the population dynamics (e.g., extinction or colonization) responsible for these community changes. Since 1990, we found that the winter bird community structure has changed with communities increasingly composed of warm-adapted species. This reshuffling of winter bird communities was strongest in southerly latitudes and driven primarily by local increases in abundance and regional patterns of colonization by southerly birds. CTI tracked patterns of changing winter temperature at different temporal scales ranging from 1 to 35 years. We conclude that a shifting winter climate has provided an opportunity for smaller, southerly distributed species to colonize new regions and promote the formation of unique winter bird assemblages throughout eastern North America. © 2014 John Wiley & Sons Ltd.

Arctic sea ice variability in the context of recent atmospheric circulation trends

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deser, C.; Walsh, J.E.; Timlin, M.S.

Sea ice is a sensitive component of the climate system, influenced by conditions in both the atmosphere and ocean. Variations in sea ice may in turn modulate climate by altering the surface albedo; the exchange of heat, moisture, and momentum between the atmosphere and ocean; and the upper ocean stratification in areas of deep water formation. The surface albedo effect is considered to be one of the dominant factors in the poleward amplification of global warming due to increased greenhouse gas concentrations simulated in many climate models. Forty years (1958--97) of reanalysis products and corresponding sea ice concentration data aremore » used to document Arctic sea ice variability and its association with surface air temperature (SAT) and sea level pressure (SLP) throughout the Northern Hemisphere extratropics. The dominant mode of winter (January-March) sea ice variability exhibits out-of-phase fluctuations between the western and eastern North Atlantic, together with a weaker dipole in the North Pacific. The time series of this mode has a high winter-to-winter autocorrelation (0.69) and is dominated by decadal-scale variations and a longer-term trend of diminishing ice cover east of Greenland and increasing ice cover west of Greenland. Associated with the dominant pattern of winter sea ice variability are large-scale changes in SAT and SLP that closely resemble the North Atlantic oscillation. The associated SAT and surface sensible and latent heat flux anomalies are largest over the portions of the marginal sea ice zone in which the trends of ice coverage have been greatest, although the well-documented warming of the northern continental regions is also apparent. the temporal and spatial relationships between the SLP and ice anomaly fields are consistent with the notion that atmospheric circulation anomalies force the sea ice variations. However, there appears to be a local response of the atmospheric circulation to the changing sea ice variations. However, there appears to be a local response of the atmospheric circulation to the changing sea ice cover east of Greenland. Specifically, cyclone frequencies have increased and mean SLPs have decreased over the retracted ice margin in the Greenland Sea, and these changes differ from those associated directly with the North Atlantic oscillation. The dominant mode of sea ice variability in summer (July-September) is more spatially uniform than that in winter. Summer ice extent for the Arctic as a whole has exhibited a nearly monotonic decline (-4% decade{sup {minus}1}) during the past 40 yr. Summer sea ice variations appear to be initiated by atmospheric circulation anomalies over the high Arctic in late spring. Positive ice-albedo feedback may account for the relatively long delay (2--3 months) between the time of atmospheric forcing and the maximum ice response, and it may have served to amplify the summer ice retreat.« less

Climate and Physiography Predict Mercury Concentrations in Game Fish Species in Quebec Lakes Better than Anthropogenic Disturbances.

PubMed

Lucotte, Marc; Paquet, Serge; Moingt, Matthieu

2016-05-01

The fluctuations of mercury levels (Hg) in fish consumed by sport fishers in North-Eastern America depend upon a plethora of interrelated biological and abiological factors. To identify the dominant factors ultimately controlling fish Hg concentrations, we compiled mercury levels (Hg) during the 1976-2010 period in 90 large natural lakes in Quebec (Canada) for two major game species: northern pike (Esox lucius) and walleye (Sander vitreus). Our statistical analysis included 28 geographic information system variables and 15 climatic variables, including sulfate deposition. Higher winter temperatures explained 36% of the variability in higher walleye growth rates, in turn accounting for 54% of the variability in lower Hg concentrations. For northern pike, the dominance of a flat topography in the watershed explained 31% of the variability in lower Hg concentrations. Higher mean annual temperatures explained 27% of the variability in higher pike Hg concentrations. Pelagic versus littoral preferred habitats for walleye and pike respectively could explain the contrasted effect of temperature between the two species. Heavy logging could only explain 2% of the increase in walleye Hg concentrations. The influence of mining on fish Hg concentrations appeared to be masked by climatic effects.

Tree Ring Chronologies in Mexico and Dendroclimatic and Ecological Applications

NASA Astrophysics Data System (ADS)

Villanueva-Diaz, J.; Cerano-Paredes, J.; Stahle, D. W.; Therrell, M. D.; Luckman, B. H.

2007-05-01

The understanding of historic hydroclimate variability is basic to determine the impact of atmospheric circulatory patterns and to plan for a proper management of limited water resources and ecosystem conservation purposes. The objective of this study was to develop a network of tree-ring chronologies for climate reconstruction and to analyze the influence of the ENSO warm phase in northern Mexico by using the Tropical Rainfall Index. Climatic sensitive tree-ring chronologies were developed in mountain ranges and riparian ecosystems of the Sierras Madre Oriental and Occidental, and central Mexico. A grid of over 30 new Douglas-fir, baldcypress, and pinyon pine chronologies were developed and seasonal winter-spring and summer precipitation reconstructions have been produced for northern and central Mexico. The seasonal winter-spring precipitation reconstructions extended 353 years (1450 - 2002) and 530 years (1472 - 2002) for Chihuahua, 228 years (1765 - 1993) and 504 years (1500 - 2003) for Durango, 602 years (1400 - 2002) for Nuevo Leon, 522 years (1474 - 1995) for Tamaulipas; and 342 years (1659 - 2001) and 410 years (1595 - 2004) for Coahuila. Some of the low frequency events were specific for each reconstruction, but common low frequency events (decadal resolution) were present in most of the reconstructions; specific cases are the droughts of the 1780s, 1810s, 1860s, 1870s, 1950s, and 1990s; and the wet episodes of the 1820s, 1830s, and 1890s.Trends in dry or wet periods were disrupted by above or below normal precipitation as affected by the ENSO phenomena, especially in the winter- spring period when this circulatory pattern produced in times abundant rains in northern Mexico. However, the ENSO influence on winter-spring precipitation has fluctuated through time. Cold fronts and hurricanes impacting the Gulf of Mexico may explain some of the hydrological behavior detected for northeastern Mexico. These results indicate that winter-spring hydroclimate variability in northern Mexico is influenced by a range of atmospheric circulatory patterns, and a greater grid of tree-ring chronologies should be developed to better explain climatic variability in this region. Currently, a couple of summer precipitation reconstructions have been developed and others are in process, but future research will focus on this issue. Summer rainfall represents over 70% of the annual precipitation in Mexico and provides water for agriculture, forest productivity, and other uses. On the other hand, fire frequency and forest dynamic studies are in process for restoration and conservation purposes.

Long-Term Variability of Satellite Lake Surface Water Temperatures in the Great Lakes

NASA Astrophysics Data System (ADS)

Gierach, M. M.; Matsumoto, K.; Holt, B.; McKinney, P. J.; Tokos, K.

2014-12-01

The Great Lakes are the largest group of freshwater lakes on Earth that approximately 37 million people depend upon for fresh drinking water, food, flood and drought mitigation, and natural resources that support industry, jobs, shipping and tourism. Recent reports have stated (e.g., the National Climate Assessment) that climate change can impact and exacerbate a range of risks to the Great Lakes, including changes in the range and distribution of certain fish species, increased invasive species and harmful algal blooms, declining beach health, and lengthened commercial navigation season. In this study, we will examine the impact of climate change on the Laurentian Great Lakes through investigation of long-term lake surface water temperatures (LSWT). We will use the ATSR Reprocessing for Climate: Lake Surface Water Temperature & Ice Cover (ARC-Lake) product over the period 1995-2012 to investigate individual and interlake variability. Specifically, we will quantify the seasonal amplitude of LSWTs, the first and last appearances of the 4°C isotherm (i.e., an important identifier of the seasonal evolution of the lakes denoting winter and summer stratification), and interpret these quantities in the context of global interannual climate variability such as ENSO.

Glacier variability in the conterminous United States during the twentieth century

USGS Publications Warehouse

McCabe, Gregory J.; Fountain, Andrew G.

2013-01-01

Glaciers of the conterminous United States have been receding for the past century. Since 1900 the recession has varied from a 24 % loss in area (Mt. Rainier, Washington) to a 66 % loss in the Lewis Range of Montana. The rates of retreat are generally similar with a rapid loss in the early decades of the 20th century, slowing in the 1950s–1970s, and a resumption of rapid retreat starting in the 1990s. Decadal estimates of changes in glacier area for a subset of 31 glaciers from 1900 to 2000 are used to test a snow water equivalent model that is subsequently employed to examine the effects of temperature and precipitation variability on annual glacier area changes for these glaciers. Model results indicate that both winter precipitation and winter temperature have been important climatic factors affecting the variability of glacier variability during the 20th Century. Most of the glaciers analyzed appear to be more sensitive to temperature variability than to precipitation variability. However, precipitation variability is important, especially for high elevation glaciers. Additionally, glaciers with areas greater than 1 km2 are highly sensitive to variability in temperature.

The absence of an Atlantic imprint on the multidecadal variability of wintertime European temperature

PubMed Central

Yamamoto, Ayako; Palter, Jaime B.

2016-01-01

Northern Hemisphere climate responds sensitively to multidecadal variability in North Atlantic sea surface temperature (SST). It is therefore surprising that an imprint of such variability is conspicuously absent in wintertime western European temperature, despite that Europe's climate is strongly influenced by its neighbouring ocean, where multidecadal variability in basin-average SST persists in all seasons. Here we trace the cause of this missing imprint to a dynamic anomaly of the atmospheric circulation that masks its thermodynamic response to SST anomalies. Specifically, differences in the pathways Lagrangian particles take to Europe during anomalous SST winters suppress the expected fluctuations in air–sea heat exchange accumulated along those trajectories. Because decadal variability in North Atlantic-average SST may be driven partly by the Atlantic Meridional Overturning Circulation (AMOC), the atmosphere's dynamical adjustment to this mode of variability may have important implications for the European wintertime temperature response to a projected twenty-first century AMOC decline. PMID:26975331

Holocene Climate Variability in the Central North Pacific: An Organic Geochemical Record from Ka'au Crater Swamp, O'ahu, Hawai'i

NASA Astrophysics Data System (ADS)

Street, J. H.; Beilman, D.; Timmermann, A.; Gaidos, E.; Paytan, A.

2010-12-01

North Pacific climate is known to have varied during the Holocene, with significant “downstream” effects on the regional climate and hydrology of western North America. Evidence from paleoclimatic studies along the northeast Pacific margin hints at several broad-scale regime shifts since the early Holocene, with spatial expressions analogous to those observed during phase shifts of the modern ENSO and PDO, though occurring on much longer (centennial to millennial) timescales. Nonetheless, the timing, magnitude and spatial patterns of Holocene rearrangements in oceanic and atmospheric circulation in the North Pacific remain incompletely defined. The main Hawaiian Islands (19 - 22 °N, 155 - 160 °W) are uniquely situated to “sample” climate variability in the subtropical, central North Pacific. Precipitation in Hawai’i is strongly influenced by the seasonal migration of the Pacific Anticyclone and the associated trade winds, and, during the winter, the frequency and intensity of westerly moisture-bearing storms. On interannual to decadal timescales, basin-wide circulation changes related to ENSO and PDO modulate trade wind strength and the occurrence of winter storm patterns, leading to local variations in precipitation. Terrestrial paleoclimatic records from Hawai’i are rare, but of great potential value to reconstruct aspects of central North Pacific atmospheric circulation during the Holocene, including the influence of the tropical ENSO system. In this study we present initial results from a 4.5 m, ~14 kyr sedimentary sequence recovered from Ka’au Crater Swamp, located near the leeward crest of the Ko’olau range of southeastern O’ahu, in a zone of high precipitation (>330 cm/yr). We utilize carbon and nitrogen elemental abundances (TOC, TN, C/N) and isotopic compositions (δ13C, δ15N) of bulk organic matter and ratios of biomarker compounds to reconstruct changes in vegetation, organic matter sources, and biogeochemical cycling in relation to climatic variables. Variation in elemental abundances and ratios, particularly in the mid-Holocene, suggest a sensitive response to climate. In addition, we evaluate the use of compound-specific hydrogen isotope (δD) measurements on plant leaf-wax compounds extracted from the sediment as a means of reconstructing paleohydrologic conditions and moisture sources to the site. Leaf-wax δD at Ka’au Crater is affected by changes in the isotopic composition precipitation as well as local water balance, both of which respond to variations in trade wind strength and the balance among the several winter circulation patterns.

Drastic shifts in the Levant hydroclimate during the last interglacial indicate changes in the tropical climate and winter storm tracks

NASA Astrophysics Data System (ADS)

Kiro, Y.; Goldstein, S. L.; Kushnir, Y.; Lazar, B.; Stein, M.

2017-12-01

Marine Isotope Stage (MIS) 5e was a warm interglacial with where with significantly varying insolation and hence varied significantly throughout this time suggesting highly variable climate. The ICDP Dead Sea Deep Drilling Project recovered a 460m record of the past 220ka, reflecting the variable climate along MIS 5e. This time interval is reflected by alternating halite and detritus sequences, including 20m of halite-free detritus during the peak insolation at 125 ka. The Dead Sea salt budget indicates that the Levant climate was extremely arid when halite formed, reaching 20% of the present runoff. The halite-free detritus layer reflects increased precipitation to levels similar to present day, assuming similar spatial and temporal rainfall patterns. However, the 234U/238U activity ratio in the lake, reflected by authigenic minerals (aragonite, gypsum and halite), shifts from values of 1.5 (reflecting the Jordan River, the present main water source) down to 1.3 at 125-122ka during the MIS5e insolation peak and 1.0 at 118-116ka. The low 234U/238U reflects increased flash floods and eastern water sources (234U/238U 1.05-1.2) from the drier part of the watershed in the desert belt. The intermediate 234U/238U of 1.3 suggests that the Jordan River, fed from Mediterranean-sourced storm tracks, continued to flow along with an increase in southern and eastern water sources. NCAR CCSM3 climate model runs for 125ka indicate increases in both Summer and Winter precipitation. The drastic decrease to 234U/238U 1.0 occurs during the driest period, indicating a near shutdown of Jordan River flow, and water input only through flash floods and southern and eastern sources. The 120ka climate model runs shows a decrease in Winter and increase in Fall precipitation as a result of an increased precipitation in the tropics. The extreme aridity, associated with increased flooding is similar to patterns expected due to future warming. The increase in aridity is the result of expansion of the desert-belt and increases in southern precipitation and indicates an important link between the tropical and mid-latitude climate.

A Coupled Snow Operations-Skier Demand Model for the Ontario (Canada) Ski Region

NASA Astrophysics Data System (ADS)

Pons, Marc; Scott, Daniel; Steiger, Robert; Rutty, Michelle; Johnson, Peter; Vilella, Marc

2016-04-01

The multi-billion dollar global ski industry is one of the tourism subsectors most directly impacted by climate variability and change. In the decades ahead, the scholarly literature consistently projects decreased reliability of natural snow cover, shortened and more variable ski seasons, as well as increased reliance on snowmaking with associated increases in operational costs. In order to develop the coupled snow, ski operations and demand model for the Ontario ski region (which represents approximately 18% of Canada's ski market), the research utilized multiple methods, including: a in situ survey of over 2400 skiers, daily operations data from ski resorts over the last 10 years, climate station data (1981-2013), climate change scenario ensemble (AR5 - RCP 8.5), an updated SkiSim model (building on Scott et al. 2003; Steiger 2010), and an agent-based model (building on Pons et al. 2014). Daily snow and ski operations for all ski areas in southern Ontario were modeled with the updated SkiSim model, which utilized current differential snowmaking capacity of individual resorts, as determined from daily ski area operations data. Snowmaking capacities and decision rules were informed by interviews with ski area managers and daily operations data. Model outputs were validated with local climate station and ski operations data. The coupled SkiSim-ABM model was run with historical weather data for seasons representative of an average winter for the 1981-2010 period, as well as an anomalously cold winter (2012-13) and the record warm winter in the region (2011-12). The impact on total skier visits and revenues, and the geographic and temporal distribution of skier visits were compared. The implications of further climate adaptation (i.e., improving the snowmaking capacity of all ski areas to the level of leading resorts in the region) were also explored. This research advances system modelling, especially improving the integration of snow and ski operations models with demand and socioeconomic implications. This innovative integrated systems model approach can be exported to other major ski tourism markets (e.g., Canada, USA, Western and Eastern Europe, Australia, Japan) to facilitate global comparative assessments of ski tourism vulnerability to climate change, establishing the standard for ski tourism vulnerability assessments and advancing scholarly work on sustainable tourism and climate-compatible development in mountain communities.

Effects of Changing Climate During the Snow Ablation Season on Seasonal Streamflow Forecasts

NASA Astrophysics Data System (ADS)

Gutzler, D. S.; Chavarria, S. B.

2017-12-01

Seasonal forecasts of total surface runoff (Q) in snowmelt-dominated watersheds derive most of their prediction skill from the historical relationship between late winter snowpack (SWE) and subsequent snowmelt runoff. Across the western US, however, the relationship between SWE and Q is weakening as temperatures rise. We describe the effects of climate variability and change during the springtime snow ablation season on water supply outlooks (forecasts of Q) for southwestern rivers. As snow melts earlier, the importance of post-snow rainfall increases: interannual variability of spring season precipitation accounts for an increasing fraction of the variability of Q in recent decades. The results indicate that improvements to the skill of S2S forecasts of spring season temperature and precipitation would contribute very significantly to water supply outlooks that are now based largely on observed SWE. We assess this hypothesis using historical data from several snowpack-dominated basins in the American Southwest (Rio Grande, Pecos, and Gila Rivers) which are undergoing rapid climate change.

Interannual variability: a crucial component of space use at the territory level.

PubMed

Uboni, Alessia; Vucetich, John A; Stahler, Daniel R; Smith, Douglas W

2015-01-01

Interannual variability in space use and how that variation is influenced by density-dependent and density-independent factors are important processes in population ecology. Nevertheless, interannual variability has been neglected by the majority of space use studies. We assessed that variation for wolves living in 15 different packs within Yellowstone National Park during a 13-year period (1996-2008). We estimated utilization distributions to quantify the intensity of space use within each pack's territory each year in summer and winter. Then, we used the volume of intersection index (VI) to quantify the extent to which space use varied from year to year. This index accounts for both the area of overlap and differences in the intensity of use throughout a territory and ranges between 0 and 1. The mean VI index was 0.49, and varied considerably, with approximately 20% of observations (n = 230) being <0.3 or >0.7. In summer, 42% of the variation was attributable to differences between packs. These differences can be attributable to learned behaviors and had never been thought to have such an influence on space use. In winter, 34% of the variation in overlap between years was attributable to interannual differences in precipitation and pack size. This result reveals the strong influence of climate on predator space use and underlies the importance of understanding how climatic factors are going to affect predator populations in the occurrence of climate change. We did not find any significant association between overlap and variables representing density-dependent processes (elk and wolf densities) or intraspecific competition (ratio of wolves to elk). This last result poses a challenge to the classic view of predator-prey systems. On a small spatial scale, predator space use may be driven by factors other than prey distribution.

Drivers of River Water Temperature Space-time Variability in Northeast Greenland

NASA Astrophysics Data System (ADS)

Hannah, D. M.; Docherty, C.; Milner, A.

2015-12-01

Water temperature plays an important role in stream ecosystem functioning; however, water temperature dynamics in high Arctic environments have received relatively little attention. Given that global climate is predicted to change most at high latitudes, it is vital we broaden our knowledge of space-time variability in Arctic river temperature to understand controlling processes and potential consequences of climate change. To address this gap, our research aims: (1) to characterise seasonal and diel patterns of variability over three summer and two winter seasons with contrasting hydrometeorological conditions, (2) to unravel the key drivers influencing thermal regimes and (3) to place these results in the context of other snow/ glacier-melt dominated environments. Fieldwork was undertaken in July-September 2013, 2014 and 2015 close to the Zackenberg Research Station in Northeast Greenland - an area of continuous permafrost with a mean July air temperature of 6 °C. Five streams were chosen that drain different water source contributions (glacier melt, snow melt, groundwater). Data were collected at 30 minute intervals using micro-dataloggers. Air temperature data were collected within 7km by the Greenland Survey. Weather conditions were highly variable between field campaigns, with 2013 experiencing below average, and 2014 and 2015 above average, snowfall. Summer water temperatures appear to be high in comparison to some Arctic streams in Alaska and in Svalbard. Winter snowfall extent decreases stream water temperature; and water temperature increases with atmospheric exposure time (distance from source) - illustrating the intertwined controls of water and heat fluxes. These Greenland streams are most strongly influenced by snowmelt, but groundwater contributions could increase with a changing climate due to increased active layer thickness, which may result in increased river temperature with implications for aquatic biodiversity and ecosystem functioning.

Regional Distribution Shifts Help Explain Local Changes in Wintering Raptor Abundance: Implications for Interpreting Population Trends

PubMed Central

Paprocki, Neil; Heath, Julie A.; Novak, Stephen J.

2014-01-01

Studies of multiple taxa across broad-scales suggest that species distributions are shifting poleward in response to global climate change. Recognizing the influence of distribution shifts on population indices will be an important part of interpreting trends within management units because current practice often assumes that changes in local populations reflect local habitat conditions. However, the individual- and population-level processes that drive distribution shifts may occur across a large, regional scale and have little to do with the habitats within the management unit. We examined the latitudinal center of abundance for the winter distributions of six western North America raptor species using Christmas Bird Counts from 1975–2011. Also, we considered whether population indices within western North America Bird Conservation Regions (BCRs) were explained by distribution shifts. All six raptors had significant poleward shifts in their wintering distributions over time. Rough-legged Hawks (Buteo lagopus) and Golden Eagles (Aquila chrysaetos) showed the fastest rate of change, with 8.41 km yr−1 and 7.74 km yr−1 shifts, respectively. Raptors may be particularly responsive to warming winters because of variable migration tendencies, intraspecific competition for nesting sites that drives males to winter farther north, or both. Overall, 40% of BCR population trend models were improved by incorporating information about wintering distributions; however, support for the effect of distribution on BCR indices varied by species with Rough-legged Hawks showing the most evidence. These results emphasize the importance of understanding how regional distribution shifts influence local-scale population indices. If global climate change is altering distribution patterns, then trends within some management units may not reflect changes in local habitat conditions. The methods used to monitor and manage bird populations within local BCRs will fundamentally change as species experience changes in distribution in response to climate change. PMID:24466253

Regional meteorological drivers and long term trends of winter-spring nitrate dynamics across watersheds in northeastern North America

USGS Publications Warehouse

Crossman, Jill; Eimers, M Catherine; Casson, Nora J.; Burns, Douglas A.; Campbell, John L.; Likens, Gene E; Mitchell, Myron J; Nelson, Sarah J.; Shanley, James B.; Watmough, Shaun A.; Webster, Kara L

2016-01-01

This study evaluated the contribution of winter rain-on-snow (ROS) events to annual and seasonal nitrate (N-NO3) export and identified the regional meteorological drivers of inter-annual variability in ROS N-NO3 export (ROS-N) at 9 headwater streams located across Ontario, Canada and the northeastern United States. Although on average only 3.3 % of annual precipitation fell as ROS during winter over the study period, these events contributed a significant proportion of annual and winter N-NO3 export at the majority of sites (average of 12 and 42 %, respectively); with the exception of the most northern catchment, where total winter precipitation was exceptionally low (average 77 mm). In years with a greater magnitude of ROS events, the timing of the peak N-NO3 export period (during spring melt) was redistributed to earlier in the year. Variability in ROS frequency and magnitude amongst sites was high and a generalised linear model demonstrated that this spatial variability could be explained by interactive effects between regional and site-specific drivers. Snowpack coverage was particularly important for explaining the site-specific ROS response. Specifically, ROS events were less common when higher temperatures eliminated snow cover despite increasing the proportion of winter rainfall, whereas ROS event frequency was greater at sites where sufficient snow cover remained. This research suggests that catchment response to changes in N deposition is sensitive to climate change; a vulnerability which appears to vary in intensity throughout the seasonally snow-covered temperate region. Furthermore, the sensitivity of stream N-NO3 export to ROS events and potential shifts (earlier) in the timing of N-NO3 export relative to other nutrients affect downstream nutrient stoichiometry and the community composition of phytoplankton and other algae.

Understanding hydro-climatic drivers of infectious diarrheal diseases in South Asia and their projected risks from regional climate models

NASA Astrophysics Data System (ADS)

Hasan, M. A.; Akanda, A. S.; Jutla, A.; Huq, A.; Colwell, R. R.

2017-12-01

Diarrheal diseases remain a major threat to global public health and are the second largest cause of death for children under the age of five. Cholera and Rotavirus diarrhea together comprise more than two-thirds of the diarrheal morbidity in South Asia. Recent studies have shown strong influences of hydrologic processes and climatic variabilities on the onset, intensity, and seasonality of the outbreaks of these diseases. However, our understanding of the propagation and manifestation of these diseases in a changing climate in vulnerable regions of the world are still limited. In this study, we build on our understanding of the role of the hydro-climatic drivers of diarrheal diseases in South Asia in recent decades to project the probable risks of the diseases in this century using the climate projection scenarios from dynamically downscaled climate models. To build the current model, we conducted a multivariate logistic regression assessment using 34 climate indices to examine the role of temperature and rainfall extremes over the seasonality of rotavirus and cholera over a South Asian country, Bangladesh. We utilize the availability of long and reliable time-series of cholera and rotavirus from Bangladesh and conducted a temporal and spatial analysis derived from both ground and satellite observations. For projecting the future risks of the diseases, we used five bias-corrected Regional Climate Model (RCM) results of the CMIP5 series under the RCP 4.5 scenario. Cholera risk shows a significantly higher rate of increase compared to Rotavirus in Bangladesh in the 21st century. As the disease is significantly influenced by extreme rainfall, majority projections showed a significant increase in flood-driven cholera risk. Most RCMs suggest a warmer winter in future years, suggesting reduced risk for Rotavirus. However, as the dryness of the climate is also highly correlated with rotavirus epidemics, the incremental risk of the disease due to drier winters would likely undermine the reduced risk due to temperature increase. Probabilistic risk assessments of these diarrheal diseases with respect to hydro-climatic variability will, not only improve the local policymaking processes, but also allow us to pinpoint the climate-health hotspots around the globe.

Climate influences on whitebark pine mortality from mountain pine beetle in the Greater Yellowstone Ecosystem.

PubMed

Buotte, Polly C; Hicke, Jeffrey A; Preisler, Haiganoush K; Abatzoglou, John T; Raffa, Kenneth F; Logan, Jesse A

2016-12-01

Extensive mortality of whitebark pine, beginning in the early to mid-2000s, occurred in the Greater Yellowstone Ecosystem (GYE) of the western USA, primarily from mountain pine beetle but also from other threats such as white pine blister rust. The climatic drivers of this recent mortality and the potential for future whitebark pine mortality from mountain pine beetle are not well understood, yet are important considerations in whether to list whitebark pine as a threatened or endangered species. We sought to increase the understanding of climate influences on mountain pine beetle outbreaks in whitebark pine forests, which are less well understood than in lodgepole pine, by quantifying climate-beetle relationships, analyzing climate influences during the recent outbreak, and estimating the suitability of future climate for beetle outbreaks. We developed a statistical model of the probability of whitebark pine mortality in the GYE that included temperature effects on beetle development and survival, precipitation effects on host tree condition, beetle population size, and stand characteristics. Estimated probability of whitebark pine mortality increased with higher winter minimum temperature, indicating greater beetle winter survival; higher fall temperature, indicating synchronous beetle emergence; lower two-year summer precipitation, indicating increased potential for host tree stress; increasing beetle populations; stand age; and increasing percent composition of whitebark pine within a stand. The recent outbreak occurred during a period of higher-than-normal regional winter temperatures, suitable fall temperatures, and low summer precipitation. In contrast to lodgepole pine systems, area with mortality was linked to precipitation variability even at high beetle populations. Projections from climate models indicate future climate conditions will likely provide favorable conditions for beetle outbreaks within nearly all current whitebark pine habitat in the GYE by the middle of this century. Therefore, when surviving and regenerating trees reach ages suitable for beetle attack, there is strong potential for continued whitebark pine mortality due to mountain pine beetle. © 2016 by the Ecological Society of America.

Assessment of climate change impacts on climate variables using probabilistic ensemble modeling and trend analysis

NASA Astrophysics Data System (ADS)

Safavi, Hamid R.; Sajjadi, Sayed Mahdi; Raghibi, Vahid

2017-10-01

Water resources in snow-dependent regions have undergone significant changes due to climate change. Snow measurements in these regions have revealed alarming declines in snowfall over the past few years. The Zayandeh-Rud River in central Iran chiefly depends on winter falls as snow for supplying water from wet regions in high Zagrous Mountains to the downstream, (semi-)arid, low-lying lands. In this study, the historical records (baseline: 1971-2000) of climate variables (temperature and precipitation) in the wet region were chosen to construct a probabilistic ensemble model using 15 GCMs in order to forecast future trends and changes while the Long Ashton Research Station Weather Generator (LARS-WG) was utilized to project climate variables under two A2 and B1 scenarios to a future period (2015-2044). Since future snow water equivalent (SWE) forecasts by GCMs were not available for the study area, an artificial neural network (ANN) was implemented to build a relationship between climate variables and snow water equivalent for the baseline period to estimate future snowfall amounts. As a last step, homogeneity and trend tests were performed to evaluate the robustness of the data series and changes were examined to detect past and future variations. Results indicate different characteristics of the climate variables at upstream stations. A shift is observed in the type of precipitation from snow to rain as well as in its quantities across the subregions. The key role in these shifts and the subsequent side effects such as water losses is played by temperature.

The effect of climate manipulations on the herbivory of the pest slug Deroceras reticulatum (Müller, 1774) (Pulmonata: Agriolimacidae)

NASA Astrophysics Data System (ADS)

El-Danasoury, H.; Iglesias-Piñeiro, J.; Córdoba, M.

2016-10-01

The pestiferous status of the terrestrial slug Deroceras reticulatum and the strong dependence of its biology and ecology on climatic factors have driven research on the potential responses of the slug to predicted scenarios of climate change. Here, we report two short-term experiments performed outdoors, under seminatural conditions, to assess the behavioural response of D. reticulatum to different climate manipulations in terms of herbivory, by measuring over 7 days the damage inflicted by slug populations to lettuce seedlings. The climate manipulations tested emulate predicted climatic conditions for northwest Spain, specifically winter warming and increased summer rainfall, in contrast respectively with normal winter conditions and summer without rain conditions. In a winter experiment, we compared a normal winter treatment with a winter warming treatment; with respect to the normal winter treatment, the winter warming treatment was characterised by higher temperature, lower relative humidity and the absence of rainfall. In a summer experiment, we compared a summer drought treatment with an increased summer rainfall treatment; with respect to the summer drought treatment, the increased summer rainfall treatment was characterised by the presence of rainfall, while the conditions of temperature and relative humidity were similar in both treatments. Neither winter warming nor increased summer rainfall did lead to a significant increase on the number of seedlings damaged by the slugs. However, with both treatments, we found a moderate increase on the amount of damage suffered by the seedlings. The results are discussed in the context of the potential responses of D. reticulatum to future climatic conditions.

The effect of climate manipulations on the herbivory of the pest slug Deroceras reticulatum (Müller, 1774) (Pulmonata: Agriolimacidae).

PubMed

El-Danasoury, H; Iglesias-Piñeiro, J; Córdoba, M

2016-10-01

The pestiferous status of the terrestrial slug Deroceras reticulatum and the strong dependence of its biology and ecology on climatic factors have driven research on the potential responses of the slug to predicted scenarios of climate change. Here, we report two short-term experiments performed outdoors, under seminatural conditions, to assess the behavioural response of D. reticulatum to different climate manipulations in terms of herbivory, by measuring over 7 days the damage inflicted by slug populations to lettuce seedlings. The climate manipulations tested emulate predicted climatic conditions for northwest Spain, specifically winter warming and increased summer rainfall, in contrast respectively with normal winter conditions and summer without rain conditions. In a winter experiment, we compared a normal winter treatment with a winter warming treatment; with respect to the normal winter treatment, the winter warming treatment was characterised by higher temperature, lower relative humidity and the absence of rainfall. In a summer experiment, we compared a summer drought treatment with an increased summer rainfall treatment; with respect to the summer drought treatment, the increased summer rainfall treatment was characterised by the presence of rainfall, while the conditions of temperature and relative humidity were similar in both treatments. Neither winter warming nor increased summer rainfall did lead to a significant increase on the number of seedlings damaged by the slugs. However, with both treatments, we found a moderate increase on the amount of damage suffered by the seedlings. The results are discussed in the context of the potential responses of D. reticulatum to future climatic conditions.

Multi-scale enhancement of climate prediction over land by increasing the model sensitivity to vegetation variability in EC-Earth

NASA Astrophysics Data System (ADS)

Alessandri, Andrea; Catalano, Franco; De Felice, Matteo; Van Den Hurk, Bart; Doblas Reyes, Francisco; Boussetta, Souhail; Balsamo, Gianpaolo; Miller, Paul

2016-04-01

The EC-Earth earth system model has been recently developed to include the dynamics of vegetation. In its original formulation, vegetation variability is simply operated by the Leaf Area Index (LAI), which affects climate basically by changing the vegetation physiological resistance to evapotranspiration. This coupling has been found to have only a weak effect on the surface climate modeled by EC-Earth. In reality, the effective sub-grid vegetation fractional coverage will vary seasonally and at interannual time-scales in response to leaf-canopy growth, phenology and senescence. Therefore it affects biophysical parameters such as the albedo, surface roughness and soil field capacity. To adequately represent this effect in EC-Earth, we included an exponential dependence of the vegetation cover on the LAI. By comparing two sets of simulations performed with and without the new variable fractional-coverage parameterization, spanning retrospective predictions at the decadal (5-years), seasonal and sub-seasonal time-scales, we show for the first time a significant multi-scale enhancement of vegetation impacts in climate simulation and prediction over land. Particularly large effects at multiple time scales are shown over boreal winter middle-to-high latitudes over Canada, West US, Eastern Europe, Russia and eastern Siberia due to the implemented time-varying shadowing effect by tree-vegetation on snow surfaces. Over Northern Hemisphere boreal forest regions the improved representation of vegetation cover tends to correct the winter warm biases, improves the climate change sensitivity, the decadal potential predictability as well as the skill of forecasts at seasonal and sub-seasonal time-scales. Significant improvements of the prediction of 2m temperature and rainfall are also shown over transitional land surface hot spots. Both the potential predictability at decadal time-scale and seasonal-forecasts skill are enhanced over Sahel, North American Great Plains, Nordeste Brazil and South East Asia, mainly related to improved performance in the surface evapotranspiration.

Multi-scale enhancement of climate prediction over land by increasing the model sensitivity to vegetation variability in EC-Earth

NASA Astrophysics Data System (ADS)

Alessandri, A.; Catalano, F.; De Felice, M.; van den Hurk, B.; Doblas-Reyes, F. J.; Boussetta, S.; Balsamo, G.; Miller, P. A.

2016-12-01

The European consortium earth system model (EC-Earth; http://www.ec-earth.org) has been recently developed to include the dynamics of vegetation. In its original formulation, vegetation variability is simply operated by the Leaf Area Index (LAI), which affects climate basically by changing the vegetation physiological resistance to evapotranspiration. This coupling has been found to have only a weak effect on the surface climate modeled by EC-Earth. In reality, the effective sub-grid vegetation fractional coverage will vary seasonally and at interannual time-scales in response to leaf-canopy growth, phenology and senescence. Therefore it affects biophysical parameters such as the albedo, surface roughness and soil field capacity. To adequately represent this effect in EC-Earth, we included an exponential dependence of the vegetation cover on the LAI. By comparing two sets of simulations performed with and without the new variable fractional-coverage parameterization, spanning from centennial (20th Century) simulations and retrospective predictions to the decadal (5-years), seasonal and weather time-scales, we show for the first time a significant multi-scale enhancement of vegetation impacts in climate simulation and prediction over land. Particularly large effects at multiple time scales are shown over boreal winter middle-to-high latitudes over Canada, West US, Eastern Europe, Russia and eastern Siberia due to the implemented time-varying shadowing effect by tree-vegetation on snow surfaces. Over Northern Hemisphere boreal forest regions the improved representation of vegetation cover tends to correct the winter warm biases, improves the climate change sensitivity, the decadal potential predictability as well as the skill of forecasts at seasonal and weather time-scales. Significant improvements of the prediction of 2m temperature and rainfall are also shown over transitional land surface hot spots. Both the potential predictability at decadal time-scale and seasonal-forecasts skill are enhanced over Sahel, North American Great Plains, Nordeste Brazil and South East Asia, mainly related to improved performance in the surface evapotranspiration.

Multi-scale enhancement of climate prediction over land by increasing the model sensitivity to vegetation variability in EC-Earth

NASA Astrophysics Data System (ADS)

Alessandri, Andrea; Catalano, Franco; De Felice, Matteo; Van Den Hurk, Bart; Doblas Reyes, Francisco; Boussetta, Souhail; Balsamo, Gianpaolo; Miller, Paul A.

2017-08-01

The EC-Earth earth system model has been recently developed to include the dynamics of vegetation. In its original formulation, vegetation variability is simply operated by the Leaf Area Index (LAI), which affects climate basically by changing the vegetation physiological resistance to evapotranspiration. This coupling has been found to have only a weak effect on the surface climate modeled by EC-Earth. In reality, the effective sub-grid vegetation fractional coverage will vary seasonally and at interannual time-scales in response to leaf-canopy growth, phenology and senescence. Therefore it affects biophysical parameters such as the albedo, surface roughness and soil field capacity. To adequately represent this effect in EC-Earth, we included an exponential dependence of the vegetation cover on the LAI. By comparing two sets of simulations performed with and without the new variable fractional-coverage parameterization, spanning from centennial (twentieth century) simulations and retrospective predictions to the decadal (5-years), seasonal and weather time-scales, we show for the first time a significant multi-scale enhancement of vegetation impacts in climate simulation and prediction over land. Particularly large effects at multiple time scales are shown over boreal winter middle-to-high latitudes over Canada, West US, Eastern Europe, Russia and eastern Siberia due to the implemented time-varying shadowing effect by tree-vegetation on snow surfaces. Over Northern Hemisphere boreal forest regions the improved representation of vegetation cover tends to correct the winter warm biases, improves the climate change sensitivity, the decadal potential predictability as well as the skill of forecasts at seasonal and weather time-scales. Significant improvements of the prediction of 2 m temperature and rainfall are also shown over transitional land surface hot spots. Both the potential predictability at decadal time-scale and seasonal-forecasts skill are enhanced over Sahel, North American Great Plains, Nordeste Brazil and South East Asia, mainly related to improved performance in the surface evapotranspiration.

Multi-scale enhancement of climate prediction over land by increasing the model sensitivity to vegetation variability in EC-Earth

NASA Astrophysics Data System (ADS)

Alessandri, Andrea; Catalano, Franco; De Felice, Matteo; Van Den Hurk, Bart; Doblas Reyes, Francisco; Boussetta, Souhail; Balsamo, Gianpaolo; Miller, Paul A.

2017-04-01

The EC-Earth earth system model has been recently developed to include the dynamics of vegetation. In its original formulation, vegetation variability is simply operated by the Leaf Area Index (LAI), which affects climate basically by changing the vegetation physiological resistance to evapotranspiration. This coupling has been found to have only a weak effect on the surface climate modeled by EC-Earth. In reality, the effective sub-grid vegetation fractional coverage will vary seasonally and at interannual time-scales in response to leaf-canopy growth, phenology and senescence. Therefore it affects biophysical parameters such as the albedo, surface roughness and soil field capacity. To adequately represent this effect in EC-Earth, we included an exponential dependence of the vegetation cover on the LAI. By comparing two sets of simulations performed with and without the new variable fractional-coverage parameterization, spanning from centennial (20th Century) simulations and retrospective predictions to the decadal (5-years), seasonal and weather time-scales, we show for the first time a significant multi-scale enhancement of vegetation impacts in climate simulation and prediction over land. Particularly large effects at multiple time scales are shown over boreal winter middle-to-high latitudes over Canada, West US, Eastern Europe, Russia and eastern Siberia due to the implemented time-varying shadowing effect by tree-vegetation on snow surfaces. Over Northern Hemisphere boreal forest regions the improved representation of vegetation cover tends to correct the winter warm biases, improves the climate change sensitivity, the decadal potential predictability as well as the skill of forecasts at seasonal and weather time-scales. Significant improvements of the prediction of 2m temperature and rainfall are also shown over transitional land surface hot spots. Both the potential predictability at decadal time-scale and seasonal-forecasts skill are enhanced over Sahel, North American Great Plains, Nordeste Brazil and South East Asia, mainly related to improved performance in the surface evapotranspiration.

Asymmetry of projected increases in extreme temperature distributions

PubMed Central

Kodra, Evan; Ganguly, Auroop R.

2014-01-01

A statistical analysis reveals projections of consistently larger increases in the highest percentiles of summer and winter temperature maxima and minima versus the respective lowest percentiles, resulting in a wider range of temperature extremes in the future. These asymmetric changes in tail distributions of temperature appear robust when explored through 14 CMIP5 climate models and three reanalysis datasets. Asymmetry of projected increases in temperature extremes generalizes widely. Magnitude of the projected asymmetry depends significantly on region, season, land-ocean contrast, and climate model variability as well as whether the extremes of consideration are seasonal minima or maxima events. An assessment of potential physical mechanisms provides support for asymmetric tail increases and hence wider temperature extremes ranges, especially for northern winter extremes. These results offer statistically grounded perspectives on projected changes in the IPCC-recommended extremes indices relevant for impacts and adaptation studies. PMID:25073751

Revisiting the relationship between jet position, forced response, and annular mode variability in the southern midlatitudes

NASA Astrophysics Data System (ADS)

Simpson, Isla R.; Polvani, Lorenzo M.

2016-03-01

Climate models exhibit a wide range in latitudinal position of the Southern Hemisphere westerly jet. Previous work has demonstrated, in the annual mean, that models with lower latitude jets, exhibit greater poleward jet shifts under climate forcings. It has been argued that this behavior is due to stronger eddy/mean flow feedbacks in models with lower latitude jets, as inferred from the timescale of the Southern Annular Mode (SAM). Here we revisit this question with a focus on seasonality. Using a larger set of models and forcing scenarios from the Coupled Model Intercomparison Project, phase 5, we find that the jet position/jet shift relationship is strong in winter but insignificant in summer, whereas the model spread in SAM timescales arises primarily in summer, with winter timescales similar across models. The results, therefore, question previous interpretations and motivate an improved understanding of the spread in model behavior.

Climate, geography, and tree establishment in Subalpine Meadows of the Olympic Mountains, Washington, U.S.A.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woodward, A.; Silsbee, D.G.; Schreiner, E.G.

1995-08-01

Noticeable changes in vegetation distribution have occurred in the Pacific Northwest during the last century as trees have established in some subalpine meadows. To study the relationship of this process to climate, recently established trees were aged in six subalpine meadows in the Olympic Mountains, Washington. The sites represent three points along a steep precipitation gradient. Subalpine fir (Abies lasiocarpa) has been establishing at the dry end of the gradient, mountain hemlock (Tsuga mertensiana) at the wet end, and both species in the center. Establishment patterns were compared with deviations from the century-long average for these weather variables: winter precipitation,more » Palmer Drought Severity Index, and winter, October and May temperatures. Results show that establishment occurred in dry areas when weather conditions were wetter than average, and in wet areas under drier than average conditions. Establishment at central sites did not show consistent relationships with climate. If future climatic conditions continue to warm, establishment of subalpine fir in subalpine meadows in dry areas may cease and mountain hemlock may resume in wet areas. 34 refs., 5 figs., 3 tabs.« less

Effects of changing climate and cultivar on the phenology and yield of winter wheat in the North China Plain

NASA Astrophysics Data System (ADS)

Li, Kenan; Yang, Xiaoguang; Tian, Hanqin; Pan, Shufen; Liu, Zhijuan; Lu, Shuo

2016-01-01

Understanding how changing climate and cultivars influence crop phenology and potential yield is essential for crop adaptation to future climate change. In this study, crop and daily weather data collected from six sites across the North China Plain were used to drive a crop model to analyze the impacts of climate change and cultivar development on the phenology and production of winter wheat from 1981 to 2005. Results showed that both the growth period (GP) and the vegetative growth period (VGP) decreased during the study period, whereas changes in the reproductive growth period (RGP) either increased slightly or had no significant trend. Although new cultivars could prolong the winter wheat phenology (0.3˜3.8 days per decade for GP), climate warming impacts were more significant and mainly accounted for the changes. The harvest index and kernel number per stem weight have significantly increased. Model simulation indicated that the yield of winter wheat exhibited increases (5.0˜19.4 %) if new cultivars were applied. Climate change demonstrated a negative effect on winter wheat yield as suggested by the simulation driven by climate data only (-3.3 to -54.8 kg ha-1 year-1, except for Lushi). Results of this study also indicated that winter wheat cultivar development can compensate for the negative effects of future climatic change.

Effects of changing climate and cultivar on the phenology and yield of winter wheat in the North China Plain.

PubMed

Li, Kenan; Yang, Xiaoguang; Tian, Hanqin; Pan, Shufen; Liu, Zhijuan; Lu, Shuo

2016-01-01

Understanding how changing climate and cultivars influence crop phenology and potential yield is essential for crop adaptation to future climate change. In this study, crop and daily weather data collected from six sites across the North China Plain were used to drive a crop model to analyze the impacts of climate change and cultivar development on the phenology and production of winter wheat from 1981 to 2005. Results showed that both the growth period (GP) and the vegetative growth period (VGP) decreased during the study period, whereas changes in the reproductive growth period (RGP) either increased slightly or had no significant trend. Although new cultivars could prolong the winter wheat phenology (0.3∼3.8 days per decade for GP), climate warming impacts were more significant and mainly accounted for the changes. The harvest index and kernel number per stem weight have significantly increased. Model simulation indicated that the yield of winter wheat exhibited increases (5.0∼19.4%) if new cultivars were applied. Climate change demonstrated a negative effect on winter wheat yield as suggested by the simulation driven by climate data only (-3.3 to -54.8 kg ha(-1) year(-1), except for Lushi). Results of this study also indicated that winter wheat cultivar development can compensate for the negative effects of future climatic change.

ENSO-related Interannual Variability of Southern Hemisphere Atmospheric Circulation: Assessment and Projected Changes in CMIP5 Models

NASA Astrophysics Data System (ADS)

Frederiksen, Carsten; Grainger, Simon; Zheng, Xiaogu; Sisson, Janice

2013-04-01

ENSO variability is an important driver of the Southern Hemisphere (SH) atmospheric circulation. Understanding the observed and projected changes in ENSO variability is therefore important to understanding changes in Australian surface climate. Using a recently developed methodology (Zheng et al., 2009), the coherent patterns, or modes, of ENSO-related variability in the SH atmospheric circulation can be separated from modes that are related to intraseasonal variability or to changes in radiative forcings. Under this methodology, the seasonal mean SH 500 hPa geopotential height is considered to consist of three components. These are: (1) an intraseasonal component related to internal dynamics on intraseasonal time scales; (2) a slow-internal component related to internal dynamics on slowly varying (interannual or longer) time scales, including ENSO; and (3) a slow-external component related to external (i.e. radiative) forcings. Empirical Orthogonal Functions (EOFs) are used to represent the modes of variability of the interannual covariance of the three components. An assessment is first made of the modes in models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) dataset for the SH summer and winter seasons in the 20th century. In reanalysis data, two EOFs of the slow component (which includes the slow-internal and slow-external components) have been found to be related to ENSO variability (Frederiksen and Zheng, 2007). In SH summer, the CMIP5 models reproduce the leading ENSO mode very well when the structures of the EOF and the associated SST, and associated variance are considered. There is substantial improvement in this mode when compared with the CMIP3 models shown in Grainger et al. (2012). However, the second ENSO mode in SH summer has a poorly reproduced EOF structure in the CMIP5 models, and the associated variance is generally underestimated. In SH winter, the performance of the CMIP5 models in reproducing the structure and variance is similar for both ENSO modes, with the associated variance being generally underestimated. Projected changes in the modes in the 21st century are then investigated using ensembles of CMIP5 models that reproduce well the 20th century slow modes. The slow-internal and slow-external components are examined separately, allowing the projected changes in the response to ENSO variability to be separated from the response to changes in greenhouse gas concentrations. By using several ensembles, the model-dependency of the projected changes in the ENSO-related slow-internal modes is examined. Frederiksen, C. S., and X. Zheng, 2007: Variability of seasonal-mean fields arising from intraseasonal variability. Part 3: Application to SH winter and summer circulations. Climate Dyn., 28, 849-866. Grainger, S., C. S. Frederiksen, and X. Zheng, 2012: Modes of interannual variability of Southern Hemisphere atmospheric circulation in CMIP3 models: Assessment and Projections. Climate Dyn., in press. Zheng, X., D. M. Straus, C. S. Frederiksen, and S. Grainger, 2009: Potentially predictable patterns of extratropical tropospheric circulation in an ensemble of climate simulations with the COLA AGCM. Quart. J. Roy. Meteor. Soc., 135, 1816-1829.

Projected climate change impacts on winter recreation in the ...

EPA Pesticide Factsheets

A physically-based water and energy balance model is used to simulate natural snow accumulation at 247 winter recreation locations across the continental United States. We combine this model with projections of snowmaking conditions to determine downhill skiing, cross-country skiing, and snowmobiling season lengths under baseline and future climates, using data from five climate models and two emissions scenarios. The present-day simulations from the snow model without snowmaking are validated with observations of snow-water-equivalent from snow monitoring sites. Projected season lengths are combined with baseline estimates of winter recreation activity to monetize impacts to the selected winter recreation activity categories for the years 2050 and 2090. Estimate the physical and economic impact of climate change on winter recreation in the contiguous U.S.

Western juniper and ponderosa pine ecotonal climate-growth relationships across landscape gradients in southern Oregon

USGS Publications Warehouse

Knutson, K.C.; Pyke, D.A.

2008-01-01

Forecasts of climate change for the Pacific northwestern United States predict warmer temperatures, increased winter precipitation, and drier summers. Prediction of forest growth responses to these climate fluctuations requires identification of climatic variables limiting tree growth, particularly at limits of free species distributions. We addressed this problem at the pine-woodland ecotone using tree-ring data for western juniper (Juniperus occidentalis var. occidentalis Hook.) and ponderosa pine (Pinus ponderosa Dougl. ex Loud.) from southern Oregon. Annual growth chronologies for 1950-2000 were developed for each species at 17 locations. Correlation and linear regression of climate-growth relationships revealed that radial growth in both species is highly dependent on October-June precipitation events that recharge growing season soil water. Mean annual radial growth for the nine driest years suggests that annual growth in both species is more sensitive to drought at lower elevations and sites with steeper slopes and sandy or rocky soils. Future increases in winter precipitation could increase productivity in both species at the pine-woodland ecotone. Growth responses, however, will also likely vary across landscape features, and our findings suggest that heightened sensitivity to future drought periods and increased temperatures in the two species will predominantly occur at lower elevation sites with poor water-holding capacities. ?? 2008 NRC.

Distribution patterns of wintering sea ducks in relation to the North Atlantic Oscillation and local environmental characteristics

USGS Publications Warehouse

Zipkin, Elise F.; Gardner, Beth; Gilbert, Andrew T.; O'Connell, Allan F.; Royle, J. Andrew; Silverman, Emily D.

2010-01-01

Twelve species of North American sea ducks (Tribe Mergini) winter off the eastern coast of the United States and Canada. Yet, despite their seasonal proximity to urbanized areas in this region, there is limited information on patterns of wintering sea duck habitat use. It is difficult to gather information on sea ducks because of the relative inaccessibility of their offshore locations, their high degree of mobility, and their aggregated distributions. To characterize environmental conditions that affect wintering distributions, as well as their geographic ranges, we analyzed count data on five species of sea ducks (black scoters Melanitta nigra americana, surf scoters M. perspicillata, white-winged scoters M. fusca, common eiders Somateria mollissima, and long-tailed ducks Clangula hyemalis) that were collected during the Atlantic Flyway Sea Duck Survey for ten years starting in the early 1990s. We modeled count data for each species within ten-nautical-mile linear survey segments using a zero-inflated negative binomial model that included four local-scale habitat covariates (sea surface temperature, mean bottom depth, maximum bottom slope, and a variable to indicate if the segment was in a bay or not), one broad-scale covariate (the North Atlantic Oscillation), and a temporal correlation component. Our results indicate that species distributions have strong latitudinal gradients and consistency in local habitat use. The North Atlantic Oscillation was the only environmental covariate that had a significant (but variable) effect on the expected count for all five species, suggesting that broad-scale climatic conditions may be directly or indirectly important to the distributions of wintering sea ducks. Our results provide critical information on species-habitat associations, elucidate the complicated relationship between the North Atlantic Oscillation, sea surface temperature, and local sea duck abundances, and should be useful in assessing the impacts of climate change on seabirds.

A late Holocene record of solar-forced atmospheric blocking variability over Northern Europe inferred from varved lake sediments of Lake Kuninkaisenlampi

NASA Astrophysics Data System (ADS)

Saarni, Saija; Muschitiello, Francesco; Weege, Stefanie; Brauer, Achim; Saarinen, Timo

2016-12-01

This study presents a new varved lake sediment sequence from Lake Kuninkaisenlampi, Eastern Finland. The record is constituted by alternations of clastic and biogenic laminae and provides a precise chronology extending back to 3607 ± 94 varve yrs. BP. The seasonality of the boreal climatic zone, with cold winters and mild summers, is reflected in the varve structure as a succession of three laminae from bottom to top, (i) a coarse to fine-grained detrital lamina marked by detrital catchment material transported by spring floods; (ii) a biogenic lamina with diatoms, plant and insect remnants reflecting biological productivity during the season of lake productivity; and (iii) a very fine amorphous organic lamina deposited during the winter stratification. The thickness of the detrital lamina in the lake reflects changes in the rate of spring snow melt in the catchment and is, therefore, considered a proxy for winter conditions. Hence, the record allows reconstructing local climate and environmental conditions on inter-annual to the multi-centennial timescales. We find that minerogenic accumulation reflected in the detrital lamina exhibits a high multi-decadal to centennial-scale spectral coherency with proxies for solar activity, such as Δ14C, and Total Solar Irradiance, suggesting a strong link between solar variability and sediment transport to the lake basin. Increased catchment erosion is observed during periods of low solar activity, which we ascribe to the development of more frequent atmospheric winter blocking circulation induced by solar-forced changes in the stratosphere. We suggest that soil frost in the catchment of Lake Kuninkaisenlampi related to more frequent winter blocking led to increased surface run-off and ultimately to increased catchment erosion during spring. We conclude that, during the past ca 3600 years, solar forcing may have modulated multi-decadal to centennial variations in sedimentation regimes in lakes from Eastern Finland and potentially in other North European lakes.

Distribution patterns of wintering sea ducks in relation to the North Atlantic Oscillation and local environmental characteristics.

PubMed

Zipkin, Elise F; Gardner, Beth; Gilbert, Andrew T; O'Connell, Allan F; Royle, J Andrew; Silverman, Emily D

2010-08-01

Twelve species of North American sea ducks (Tribe Mergini) winter off the eastern coast of the United States and Canada. Yet, despite their seasonal proximity to urbanized areas in this region, there is limited information on patterns of wintering sea duck habitat use. It is difficult to gather information on sea ducks because of the relative inaccessibility of their offshore locations, their high degree of mobility, and their aggregated distributions. To characterize environmental conditions that affect wintering distributions, as well as their geographic ranges, we analyzed count data on five species of sea ducks (black scoters Melanitta nigra americana, surf scoters M. perspicillata, white-winged scoters M. fusca, common eiders Somateria mollissima, and long-tailed ducks Clangula hyemalis) that were collected during the Atlantic Flyway Sea Duck Survey for ten years starting in the early 1990s. We modeled count data for each species within ten-nautical-mile linear survey segments using a zero-inflated negative binomial model that included four local-scale habitat covariates (sea surface temperature, mean bottom depth, maximum bottom slope, and a variable to indicate if the segment was in a bay or not), one broad-scale covariate (the North Atlantic Oscillation), and a temporal correlation component. Our results indicate that species distributions have strong latitudinal gradients and consistency in local habitat use. The North Atlantic Oscillation was the only environmental covariate that had a significant (but variable) effect on the expected count for all five species, suggesting that broad-scale climatic conditions may be directly or indirectly important to the distributions of wintering sea ducks. Our results provide critical information on species-habitat associations, elucidate the complicated relationship between the North Atlantic Oscillation, sea surface temperature, and local sea duck abundances, and should be useful in assessing the impacts of climate change on seabirds.

Analysis of the variability of the North Atlantic eddy-driven jet stream in CMIP5

NASA Astrophysics Data System (ADS)

Iqbal, Waheed; Leung, Wai-Nang; Hannachi, Abdel

2017-09-01

The North Atlantic eddy-driven jet is a dominant feature of extratropical climate and its variability is associated with the large-scale changes in the surface climate of midlatitudes. Variability of this jet is analysed in a set of General Circulation Models (GCMs) from the Coupled Model Inter-comparison Project phase-5 (CMIP5) over the North Atlantic region. The CMIP5 simulations for the 20th century climate (Historical) are compared with the ERA40 reanalysis data. The jet latitude index, wind speed and jet persistence are analysed in order to evaluate 11 CMIP5 GCMs and to compare them with those from CMIP3 integrations. The phase of mean seasonal cycle of jet latitude and wind speed from historical runs of CMIP5 GCMs are comparable to ERA40. The wind speed mean seasonal cycle by CMIP5 GCMs is overestimated in winter months. A positive (negative) jet latitude anomaly in historical simulations relative to ERA40 is observed in summer (winter). The ensemble mean of jet latitude biases in historical simulations of CMIP3 and CMIP5 with respect to ERA40 are -2.43° and -1.79° respectively. Thus indicating improvements in CMIP5 in comparison to the CMIP3 GCMs. The comparison of historical and future simulations of CMIP5 under RCP4.5 and RCP8.5 for the period 2076-2099, shows positive anomalies in the jet latitude implying a poleward shifted jet. The results from the analysed models offer no specific improvements in simulating the trimodality of the eddy-driven jet.

Severe winter cooling during the Younger Dryas in northern Alaska - evidence from the stable isotope composition of a buried ice-wedge system

NASA Astrophysics Data System (ADS)

Meyer, Hanno; Schirrmeister, Lutz; Yoshikawa, Kenji; Opel, Thomas; Wetterich, Sebastian; Hubberten, Hans-W.; Brown, Jerry

2010-05-01

The Younger Dryas (YD) interval, from approximately 12.9 to 11.5 kyr cal BP, a rapid reversion to glacial climate conditions at the Pleistocene-Holocene transition, has generally been attributed to the release of meltwater from the Laurentide Ice Sheet to the North Atlantic or Arctic oceans. The reaction of the North Pacific region to this "shutdown" of the thermohaline circulation in the North Atlantic during Younger Dryas is, however, little understood. The YD cold interval is of great interest for understanding rapid natural climate change, especially with regard to recent global warming scenarios. Various archives such as glacier ice, tree rings, lacustrine and marine sediments provide evidence for strong climate variability during the Late Glacial-Holocene transition. In our study, we investigated a relict, buried ice-wedge system within the continuous permafrost zone near Barrow, northern Alaska (71°18'N, 156°40'W). The Barrow ice-wedge system is buried under about three meters of Late Glacial/early Holocene ice-rich sediments. The ice wedges are accessible through a shaft which extends into an underground excavation, where a detailed description and sampling with an electrical chain saw were carried out. Permafrost is not only susceptible to recent climate change, it also may store evidence of these changes in ground ice, especially in ice wedges. Ice wedges can be assessed by stable water isotope methods similar to glacier ice climate reconstructions. Ice wedges are assumed to be indicative of winter climate conditions, because the seasonality of thermal contraction cracking and of the infill of frost cracks are generally related to winter and spring, respectively. In this paper, we present a winter climate record from ice wedges in permafrost of northern Alaska, a region, where paleoclimate records extending beyond the Late Glacial-Holocene transition are generally rather sparse, often restricted to lake sediments and rely mostly on summer indicators such as pollen. This reconstruction is the first radiocarbon-dated centennial-scale stable water isotope record from permafrost at all. The Late Glacial winter climate reconstruction from Barrow ice wedges clearly demonstrates the existence of a Younger Dryas cold event, formerly believed to be reduced or absent in this area. Comparing the Barrow ice-wedge record to Greenland ice cores (such as N-GRIP), we observe similar and contemporaneous isotopic variations in the same order of magnitude, underpinning the climatic relevance of our ice wedge data. The Barrow ice-wedge stable isotope record additionally displays a gradual change of the atmospheric moisture source conditions during the Younger Dryas reflected in a shift of the d excess, potentially being associated with the successive opening of the Bering Strait.

Decadal-scale climate drivers for glacial dynamics in Glacier National Park, Montana, USA

USGS Publications Warehouse

Pederson, G.T.; Fagre, D.B.; Gray, S.T.; Graumlich, L.J.

2004-01-01

Little Ice Age (14th-19th centuries A.D.) glacial maxima and 20th century retreat have been well documented in Glacier National Park, Montana, USA. However, the influence of regional and Pacific Basin driven climate variability on these events is poorly understood. We use tree-ring reconstructions of North Pacific surface temperature anomalies and summer drought as proxies for winter glacial accumulation and summer ablation, respectively, over the past three centuries. These records show that the 1850's glacial maximum was likely produced by ???70 yrs of cool/wet summers coupled with high snowpack. Post 1850, glacial retreat coincides with an extended period (>50 yr) of summer drought and low snowpack culminating in the exceptional events of 1917 to 1941 when retreat rates for some glaciers exceeded 100 m/yr. This research highlights potential local and ocean-based drivers of glacial dynamics, and difficulties in separating the effects of global climate change from regional expressions of decadal-scale climate variability. Copyright 2004 by the American Geophysical Union.

Soil erosion from winter wheat cropland under climate change in central Oklahoma

USDA-ARS?s Scientific Manuscript database

Effects of climate change on sediment yield from a winter wheat field were investigated to determine what conservation practices would be required under climate change to maintain future sediment yield at no more than today’s rates. GCM climate projections for climate change scenario RCP8.5 in West-...

Reconstruction of Monsoon Driven South China Sea Surface Ocean Circulation using Coral Δ14C

NASA Astrophysics Data System (ADS)

Goodkin, N.; Bolton, A.; Karnauskas, K. B.; Hughen, K. A.; Griffin, S.; Druffel, E. R. M.

2016-12-01

The need to improve our understanding of annual and decadal climate behavior in the South China Sea is increasingly important, as this region includes the largest population density globally but encompasses few climate records. Here we present a record of annually resolved Δ14C from a coral collected off the coast of Nha Trang, Vietnam (12°12'49.90″N, 109°18'17.51″E), that reveals a significant correlation to regional winter sea level pressure (SLP) and sea surface temperature (SST), and extends back more than 400 years. Coral Δ14C during thermonuclear bomb testing indicates the presence of wet-season (summer) upwelling, demonstrated by low Δ14C values for both baseline and peak values relative to other records in the region (Bolton et al., 2016, Radiocarbon). However, annually resolved pre-bomb Δ14C correlates significantly to regional dry-season (winter) SLP and SST, indicating that annual variability is driven by changes to the East Asian Winter Monsoon (EAWM) and subsequent down-welling at this site. Spectral density is focused at 25, 11.8, 7, 4, and 3.2 years per cycle reflecting a range of influences on surface advection variability including the EAWM (D'Arrigo et al., 2005, GRL) and the El Nino Southern Oscillation (ENSO). Spectral power at all of these frequencies decreases following the Little Ice Age ( 1600-1850?) to today, indicating that wind driven surface advection was more variable when hemispheric temperatures were cooler. Decadal variance in the past 100 years is significantly correlated to variance records of the Arctic Oscillation (AO, Thompson and Wallace, 1989, GRL), suggesting that increasing variance in the EAWM may be tied to increasing variance of the AO during the Little Ice Age and vice versa.

Trends and variability in streamflow and snowmelt runoff timing in the southern Tianshan Mountains

NASA Astrophysics Data System (ADS)

Shen, Yan-Jun; Shen, Yanjun; Fink, Manfred; Kralisch, Sven; Chen, Yaning; Brenning, Alexander

2018-02-01

Streamflow and snowmelt runoff timing of mountain rivers are susceptible to climate change. Trends and variability in streamflow and snowmelt runoff timing in four mountain basins in the southern Tianshan were analyzed in this study. Streamflow trends were detected by Mann-Kendall tests and changes in snowmelt runoff timing were analyzed based on the winter/spring snowmelt runoff center time (WSCT). Pearson's correlation coefficient was further calculated to analyze the relationships between climate variables, streamflow and WSCT. Annual streamflow increased significantly in past decades in the southern Tianshan, especially in spring and winter months. However, the relations between streamflow and temperature/precipitation depend on the different streamflow generation processes. Annual precipitation plays a vital role in controlling recharge in the Toxkon basin, while the Kaidu and Huangshuigou basins are governed by both precipitation and temperature. Seasonally, temperature has a strong effect on streamflow in autumn and winter, while summer streamflow appears more sensitive to changes in precipitation. However, temperature is the dominant factor for streamflow in the glacierized Kunmalik basin at annual and seasonal scales. An uptrend in streamflow begins in the 1990s at both annual and seasonal scales, which is generally consistent with temperature and precipitation fluctuations. Average WSCT dates in the Kaidu and Huangshuigou basins are earlier than in the Toxkon and Kunmalik basins, and shifted towards earlier dates since the mid-1980s in all the basins. It is plausible that WSCT dates are more sensitive to warmer temperature in spring period compared to precipitation, except for the Huangshuigou basin. Taken together, these findings are useful for applications in flood risk regulation, future hydropower projects and integrated water resources management.

Poleward transport variability in the Northern Hemisphere during final stratospheric warmings simulated by CESM(WACCM)

NASA Astrophysics Data System (ADS)

Thiéblemont, Rémi; Matthes, Katja; Orsolini, Yvan J.; Hauchecorne, Alain; Huret, Nathalie

2016-09-01

Observational studies of Arctic stratospheric final warmings have shown that tropical/subtropical air masses can be advected to high latitudes and remain confined within a long-lived "frozen-in" anticyclone (FrIAC) for several months. It was suggested that the frequency of FrIACs may have increased since 2000 and that their interannual variability may be modulated by (i) the occurrence of major stratospheric warmings (mSSWs) in the preceding winter and (ii) the phase of the quasi-biennial oscillation (QBO). In this study, we tested these observational-based hypotheses for the first time using a chemistry climate model. Three 145 year sensitivity experiments were performed with the National Center of Atmospheric Research's Community Earth System Model (CESM): one control experiment including only natural variability, one with an extreme greenhouse gas emission scenario, and one without the QBO in the tropical stratosphere. In comparison with reanalysis, the model simulates a realistic frequency and characteristics of FrIACs, which occur under an abrupt and early winter-to-summer stratospheric circulation transition, driven by enhanced planetary wave activity. Furthermore, the model results support the suggestion that the development of FrIACs is favored by an easterly QBO in the middle stratosphere and by the absence of mSSWs during the preceding winter. The lower stratospheric persistence of background dynamical state anomalies induced by deep mSSWs leads to less favorable conditions for planetary waves to enter the high-latitude stratosphere in April, which in turn decreases the probability of FrIAC development. Our model results do not suggest that climate change conditions (RCP8.5 scenario) influence FrIAC occurrences.

Poleward Transport Variability in the Northern Hemisphere during Final Stratospheric Warmings simulated by CESM(WACCM)

NASA Astrophysics Data System (ADS)

Thiéblemont, Rémi; Matthes, Katja; Orsolini, Yvan; Hauchecorne, Alain; Huret, Nathalie

2017-04-01

Observational studies of Arctic stratospheric final warmings have shown that tropical/subtropical air masses can be advected to high latitudes and remain confined within a long-lived "frozen-in" anticyclone (FrIAC) for several months. It was suggested that the frequency of FrIACs may have increased since 2000 and that their interannual variability may be modulated by (i) the occurrence of major stratospheric warmings (mSSWs) in the preceding winter and (ii) the phase of the Quasi-Biennial Oscillation (QBO). In this study, we tested these observational-based hypotheses for the first time using a chemistry-climate model. Three 145-year sensitivity experiments were performed with the National Center of Atmospheric Research's Community Earth System Model (CESM): one control experiment including only natural variability, one with an extreme greenhouse gas emission scenario, and one without the QBO in the tropical stratosphere. In comparison with reanalysis, the model simulates a realistic frequency and characteristics of FrIACs, which occur under an abrupt and early winter-to-summer stratospheric circulation transition, driven by enhanced planetary wave activity. Furthermore, the model results support the suggestion that the development of FrIACs is favored by an easterly QBO in the middle stratosphere and by the absence of mSSWs during the preceding winter. The lower stratospheric persistence of background dynamical state anomalies induced by deep mSSWs leads to less favorable conditions for planetary waves to enter the high-latitude stratosphere in April, which in turn decreases the probability of FrIAC development. Our model results do not suggest that climate change conditions (RCP8.5 scenario) influence FrIAC occurrences.

Influence of North Atlantic modes on European climate extremes

NASA Astrophysics Data System (ADS)

Proemmel, K.; Cubasch, U.

2017-12-01

It is well known that the North Atlantic strongly influences European climate. Only few studies exist that focus on its impact on climate extremes. We are interested in these extremes and the processes and mechanisms behind it. For the analysis of the North Atlantic Oscillation (NAO) we use simulations performed with the Max Planck Institute for Meteorology Earth System Model (MPI-ESM). The NAO has a strong impact especially on European winter and the changes in minimum temperature are even larger than in maximum temperature. The impact of the Atlantic Multi-decadal Variability (AMV) on climate extremes is analyzed in ECHAM6 simulations forced with AMV warm and AMV cold sea surface temperature patterns. We analyze different extreme indices and try to understand the processes.

Climate drivers on malaria transmission in Arunachal Pradesh, India.

PubMed

Upadhyayula, Suryanaryana Murty; Mutheneni, Srinivasa Rao; Chenna, Sumana; Parasaram, Vaideesh; Kadiri, Madhusudhan Rao

2015-01-01

The present study was conducted during the years 2006 to 2012 and provides information on prevalence of malaria and its regulation with effect to various climatic factors in East Siang district of Arunachal Pradesh, India. Correlation analysis, Principal Component Analysis and Hotelling's T² statistics models are adopted to understand the effect of weather variables on malaria transmission. The epidemiological study shows that the prevalence of malaria is mostly caused by the parasite Plasmodium vivax followed by Plasmodium falciparum. It is noted that, the intensity of malaria cases declined gradually from the year 2006 to 2012. The transmission of malaria observed was more during the rainy season, as compared to summer and winter seasons. Further, the data analysis study with Principal Component Analysis and Hotelling's T² statistic has revealed that the climatic variables such as temperature and rainfall are the most influencing factors for the high rate of malaria transmission in East Siang district of Arunachal Pradesh.

Are winter and summer dormancy symmetrical seasonal adaptive strategies? The case of temperate herbaceous perennials.

PubMed

Gillespie, Lauren M; Volaire, Florence A

2017-02-01

Dormancy in higher plants is an adaptive response enabling plant survival during the harshest seasons and has been more explored in woody species than in herbaceous species. Nevertheless, winter and summer shoot meristem dormancy are adaptive strategies that could play a major role in enhancing seasonal stress tolerance and resilience of widespread herbaceous plant communities. This review outlines the symmetrical aspects of winter and summer dormancy in order to better understand plant adaptation to severe stress, and highlight research priorities in a changing climate. Seasonal dormancy is a good model to explore the growth-stress survival trade-off and unravel the relationships between growth potential and stress hardiness. Although photoperiod and temperature are known to play a crucial, though reversed, role in the induction and release of both types of dormancy, the thresholds and combined effects of these environmental factors remain to be identified. The biochemical compounds involved in induction or release in winter dormancy (abscisic acid, ethylene, sugars, cytokinins and gibberellins) could be a priority research focus for summer dormancy. To address these research priorities, herbaceous species, being more tractable than woody species, are excellent model plants for which both summer and winter dormancy have been clearly identified. Summer and winter dormancy, although responding to inverse conditions, share many characteristics. This analogous nature can facilitate research as well as lead to insight into plant adaptations to extreme conditions and the evolution of phenological patterns of species and communities under climate change. The development of phenotypes showing reduced winter and/or enhanced summer dormancy may be expected and could improve adaptation to less predictable environmental stresses correlated with future climates. To this end, it is suggested to explore the inter- and intraspecific genotypic variability of dormancy and its plasticity according to environmental conditions to contribute to predicting and mitigating global warming. © The Author 2017. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Population viability of Pediocactus bradyi (Cactaceae) in a changing climate.

PubMed

Shryock, Daniel F; Esque, Todd C; Hughes, Lee

2014-11-01

A key question concerns the vulnerability of desert species adapted to harsh, variable climates to future climate change. Evaluating this requires coupling long-term demographic models with information on past and projected future climates. We investigated climatic drivers of population growth using a 22-yr demographic model for Pediocactus bradyi, an endangered cactus in northern Arizona. We used a matrix model to calculate stochastic population growth rates (λs) and the relative influences of life-cycle transitions on population growth. Regression models linked population growth with climatic variability, while stochastic simulations were used to (1) understand how predicted increases in drought frequency and extreme precipitation would affect λs, and (2) quantify variability in λs based on temporal replication of data. Overall λs was below unity (0.961). Population growth was equally influenced by fecundity and survival and significantly correlated with increased annual precipitation and higher winter temperatures. Stochastic simulations increasing the probability of drought and extreme precipitation reduced λs, but less than simulations increasing the probability of drought alone. Simulations varying the temporal replication of data suggested 14 yr were required for accurate λs estimates. Pediocactus bradyi may be vulnerable to increases in the frequency and intensity of extreme climatic events, particularly drought. Biotic interactions resulting in low survival during drought years outweighed increased seedling establishment following heavy precipitation. Climatic extremes beyond historical ranges of variability may threaten rare desert species with low population growth rates and therefore high susceptibility to stochastic events. © 2014 Botanical Society of America, Inc.

The impact of extreme weather conditions on the life of settlers in the Central Russia in X - XVI centuries

NASA Astrophysics Data System (ADS)

Graves, Irina; Nizovtsev, Viacheslav; Erman, Natalia

2017-04-01

A special place in the reconstruction of climate dynamics takes an analysis of extraordinary meteorological phenomena. These extreme weather events in the first place impact the functioning of, the rhythm and dynamics of the landscapes and determine not only the features of economy, but also certain aspects of historical development. In the analysis of primary chronicles and published data, along with the direct climatic characteristics (hot, warm, cold, wet, dry, etc.) a lot of attention was paid to abnormal (extreme) natural phenomena and indirect indications of climate variability (floods, crop failures, hunger years, epidemics, etc.). As a result, tables were compiled reflecting climatic basic characteristics and extremes for each year since 900 BC. X-XI centuries was a period of minor climatic optimum - the climate was warmer and drier than the modern one. In addition to higher temperatures (up to 1-3C above than mordern), during this period there were no severe winters. A small amount of summer rainfall has led to a reduction in the number of small water reservoirs and flooding rivers. This is evidenced by Slavic settlements on floodplains of a number of rivers in the Moscow region. It is in this favorable climatic time the way "from the Vikings to the Greeks" was open. Catastrophic natural events had a minimum repeatability. For example, during the X century the Russian chronicles mentioned 41 extreme event, but for the XIII century - 102. Most of the villages and towns were located on the low floodplain terraces of rivers. The main farmland was concentrated there as well. In the "period of contrasts" (XIII - XIV centuries) there was an increase of intra-seasonal climate variability, humidity and widespread reduction in summer temperatures by 1-2C. The number of extreme weather events increased: cold prolonged winters, long rains in summers, cold weather returns in the early summer, early frosts in late summer - early autumn. Such conditions often resulted in crop damage and famine. From the XIV century the little Ice Age began. Year average temperature becomes lower by 1.4°C and summer temperature - by 2-3°C. In the XIV century the chronicles mentioned a total of 100 extreme natural phenomena, as a result of which Russia experienced more than 37 years of famine. The climate was particularly variable in late XIV - early XV century and XVI - XVII centuries, when there were years of particularly cold winters and increased humidity (due to winter precipitation). The duration of the crop growing season was reduced by three weeks. At the beginning of the XVII century spruce became dominant in the spruce-deciduous forests and co-dominant in deciduous forests. There was a transfer of settlements and agricultural land to interfluve areas and higher river valleys. The determining factors were demographic, socio-economic and historical factors, but the role of natural factors cannot be overlooked. The end of the XVI century was marked by the most severe political and economic crisis in the Russian State (oprichnina (political and administrative apparatus established by Ivan IV) and Livonian Wars by Ivan IV), which, combined with deteriorating environmental conditions (increased humidity of the climate, the average annual temperature drop) caused massive desolation of the lands. Many hundreds of villages turned into wasteland. In this period the Moscow land was reported as a "wild desert, covered with shrubs, bogs and imbanks", there were also memories of the past navigation on small rivers, data on mills on the streams. The climate deterioration caused the agrarian revolution in Russia in XIV-XVI centuries. Slash-and-burn and shifting cultivation was replaced by plow farming system (two- and three-field), which was more adapted to the harsh climatic conditions. The work is performed under project № 17-05-00662of the Russian Foundation for Basic Research

Exploring a Variable-Resolution Approach for Simulating Regional Climate in the Rocky Mountain Region Using the VR-CESM

NASA Astrophysics Data System (ADS)

Wu, Chenglai; Liu, Xiaohong; Lin, Zhaohui; Rhoades, Alan M.; Ullrich, Paul A.; Zarzycki, Colin M.; Lu, Zheng; Rahimi-Esfarjani, Stefan R.

2017-10-01

The reliability of climate simulations and projections, particularly in the regions with complex terrains, is greatly limited by the model resolution. In this study we evaluate the variable-resolution Community Earth System Model (VR-CESM) with a high-resolution (0.125°) refinement over the Rocky Mountain region. The VR-CESM results are compared with observations, as well as CESM simulation at a quasi-uniform 1° resolution (UNIF) and Canadian Regional Climate Model version 5 (CRCM5) simulation at a 0.11° resolution. We find that VR-CESM is effective at capturing the observed spatial patterns of temperature, precipitation, and snowpack in the Rocky Mountains with the performance comparable to CRCM5, while UNIF is unable to do so. VR-CESM and CRCM5 simulate better the seasonal variations of precipitation than UNIF, although VR-CESM still overestimates winter precipitation whereas CRCM5 and UNIF underestimate it. All simulations distribute more winter precipitation along the windward (west) flanks of mountain ridges with the greatest overestimation in VR-CESM. VR-CESM simulates much greater snow water equivalent peaks than CRCM5 and UNIF, although the peaks are still 10-40% less than observations. Moreover, the frequency of heavy precipitation events (daily precipitation ≥ 25 mm) in VR-CESM and CRCM5 is comparable to observations, whereas the same events in UNIF are an order of magnitude less frequent. In addition, VR-CESM captures the observed occurrence frequency and seasonal variation of rain-on-snow days and performs better than UNIF and CRCM5. These results demonstrate the VR-CESM's capability in regional climate modeling over the mountainous regions and its promising applications for climate change studies.

Climate forcing for dynamics of dissolved inorganic nutrients at Palmer Station, Antarctica: An interdecadal (1993-2013) analysis

NASA Astrophysics Data System (ADS)

Kim, Hyewon; Doney, Scott C.; Iannuzzi, Richard A.; Meredith, Michael P.; Martinson, Douglas G.; Ducklow, Hugh W.

2016-09-01

We analyzed 20 years (1993-2013) of observations of dissolved inorganic macronutrients (nitrate, N; phosphate, P; and silicate, Si) and chlorophyll a (Chl) at Palmer Station, Antarctica (64.8°S, 64.1°W) to elucidate how large-scale climate and local physical forcing affect the interannual variability in the seasonal phytoplankton bloom and associated drawdown of nutrients. The leading modes of nutrients (N, P, and Si empirical orthogonal functions 1, EOF1) represent overall negative anomalies throughout growing seasons, showing a mixed signal of variability in the initial levels and drawdown thereafter (low-frequency dynamics). The second most common seasonal patterns of nitrate and phosphate (N and P EOF2) capture prolonged drawdown events during December-March, which are correlated to Chl EOF1. Si EOF2 captures a drawdown event during November-December, which is correlated to Chl EOF2. These different drawdown patterns are shaped by different sets of physical and climate forcing mechanisms. N and P drawdown events during December-March are influenced by the winter and spring Southern Annular Mode (SAM) phase, where nutrient utilization is enhanced in a stabilized upper water column as a consequence of SAM-driven winter sea ice and spring wind dynamics. Si drawdown during November-December is influenced by early sea ice retreat, where ice breakup may induce abrupt water column stratification and a subsequent diatom bloom or release of diatom cells from within the sea ice. Our findings underscore that seasonal nutrient dynamics in the coastal WAP are coupled to large-scale climate forcing and related physics, understanding of which may enable improved projections of biogeochemical responses to climate change.

Lake Ice Cover of Shallow Lakes and Climate Interactions in Arctic Regions (1950-2011): SAR Data Analysis and Numerical Modeling

NASA Astrophysics Data System (ADS)

Surdu, C.; Duguay, C.; Brown, L.; Fernàndez-Prieto, D.; Samuelsson, P.

2012-12-01

Lake ice cover is highly correlated with climatic conditions and has, therefore, been demonstrated to be an essential indicator of climate variability and change. Recent studies have shown that the duration of the lake ice cover has decreased, mainly as a consequence of earlier thaw dates in many parts of the Northern Hemisphere over the last 50 years, mainly as a feedback to increased winter and spring air temperature. In response to projected air temperature and winter precipitation changes by climate models until the end of the 21st century, the timing, duration, and thickness of ice cover on Arctic lakes are expected to be impacted. This, in turn, will likely alter the energy, water, and bio-geochemical cycling in various regions of the Arctic. In the case of shallow tundra lakes, many of which are less than 3-m deep, warmer climate conditions could result in a smaller fraction of lakes that fully freeze to the bottom at the time of maximum winter ice thickness since thinner ice covers are predicted to develop. Shallow thermokarst lakes of the coastal plain of northern Alaska, and of other similar Arctic regions, have likely been experiencing changes in seasonal ice phenology and thickness over the last few decades but these have not yet been comprehensively documented. Analysis of a 20-year time series of ERS-1/2 synthetic aperture radar (SAR) data and numerical lake ice modeling were employed to determine the response of ice cover (thickness, freezing to bed, and phenology) on shallow lakes of the North Slope of Alaska (NSA) to climate conditions over the last three decades. New downscaled data specific to the Arctic domain (at a resolution of 0.44 degrees using ERA Interim Reanalysis as boundary condition) produced by the Rossby Centre Regional Atmospheric Climate Model (RCA4) was used to drive the Canadian Lake Ice Model (CLIMo) for the period 1950-2011. In order to assess and integrate the SAR-derived observed changes into a longer historical context, and to improve the simulation outputs, CLIMo was also forced with climatic data recorded at the Barrow airport meteorological station since the middle of the 20th century. ERS-1/2 data was used to map areas of the shallow lakes that freeze to bed and the rate at which this occurs during the ice season for the period 1991-2011. The results were compared to daily ice thickness results derived from CLIMo. Analysis from a sub-region of the NSA near Barrow shows that the interannual variability in ice thickness simulated with CLIMo compares favorably with the fraction of lakes that freeze to their bed in winter, thicker ice cover corresponding to a higher ratio of lakes fully frozen to the bottom, as determined from the analysis of SAR data.

Subalpine tree growth, climate, and increasing CO sub 2 : An assessment of recent growth trends. [Pinus balfouriana; P. murrayana; Juniperus occidentalis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graumlich, L.J.

1991-02-01

Five tree-ring series from foxtail pine (Pinus balfouriana), lodgepole pine (P. murrayana), and western juniper (Juniperus occidentalis) collected in the Sierra Nevada, California, were analyzed to determine if the temporal and spatial patterns of recent growth were consistent with the hypothesized CO{sub 2}-induced growth enhancement. Specifically, the author addresses the following questions: (1) can growth trends be explained solely in terms of climatic variation; (2) are recent growth trends unusual with respect to long-term growth records While the results offer no support for the hypothesized CO{sub 2} fertilization effect, they do provide insights into the response of subalpine conifers tomore » climatic variation. Response surfaces demonstrate that precipitation during previous winter and temperature during the current summer interact in controlling growth and that the response can be nonlinear. Although maximum growth rates occur under conditions of high winter precipitation and warm summers for all three species, substantial species-to-species variation occurs in the response to these two variables.« less

A reindeer herder's perspective on caribou, weather and socio-economic change on the Seward Peninsula, Alaska.

Treesearch

Kumi Rattenbury; Knut Kielland; Greg Finstad; William Schneider

2009-01-01

Nonclimate variables shape vulnerability and adaptive capacity to climate change. Here, we describe how recent environmental and socioeconomic developments have transformed reindeer herding and perceptions of weather on the Seward Peninsula, Alaska. The reindeer industry has shrunk considerably since the early 1990s, when the winter range of the Western Arctic Caribou...

Climate and life-history evolution in evening primroses (Oenothera, Onagraceae): a phylogenetic comparative analysis.

PubMed

Evans, Margaret E K; Hearn, David J; Hahn, William J; Spangle, Jennifer M; Venable, D Lawrence

2005-09-01

Evolutionary ecologists have long sought to understand the conditions under which perennial (iteroparous) versus annual (semelparous) plant life histories are favored. We evaluated the idea that aridity and variation in the length of droughts should favor the evolution of an annual life history, both by decreasing adult survival and by increasing the potential for high seedling survival via reduced plant cover. We calculated phylogenetically independent contrasts of climate with respect to life history in a clade of winter-establishing evening primroses (sections Anogra and Kleinia; Oenothera; Onagraceae), which includes seven annuals, 12 perennials, and two variable taxa. Climate variables were quantified from long-term records at weather stations near collection localities. To explicitly account for phylogenetic uncertainty, contrasts were calculated on a random sample of phylogenetic trees from the posterior distribution of a Bayesian analysis of DNA sequence data. Statements of association are based on comparing the per-tree mean contrast, which has a null expectation of zero, to a set of per-tree mean contrasts calculated on the same trees, after randomizing the climate data. As predicted, increased annual aridity, increased annual potential evapotranspiration, and decreased annual precipitation were associated with transitions to the annual habit, but these trends were not significantly different from the null pattern. Transitions to the annual habit were not significantly associated with increases in one measure of aridity in summer nor with increased summer drought, but they were associated with significantly increased maximum summer temperatures. In winter, increased aridity and decreased precipitation were significantly associated with transitions to the annual habit. Changes in life history were not significantly associated with changes in the coefficient of variation of precipitation, either on an annual or seasonal (summer vs. winter) basis. Though we cannot attribute causality on the basis of a correlational, historical study, our results are consistent with the idea that increased heat and drought at certain times of the year favor the evolution of the annual habit. Increased heat in summer may cause adult survival to decline, while increased aridity and decreased precipitation in the season of seedling recruitment (winter) may favor a drought-avoiding, short-lived annual strategy. Not all of the predicted patterns were observed: the capability for drought-induced dormancy may preclude change in habit in response to summer drought in our study group.

The indirect effects of climate variability on the reproductive dynamics and productivity of an avian predator in the arid Southwest.

PubMed

Borgman, Corrie C; Wolf, Blair O

2016-01-01

The deserts of the southwestern US are experiencing rapid warming, and climate models predict declining winter precipitation. The combined effects of higher air temperatures and drought are a reduction in productivity, which may importantly impact reproduction in consumers. Here, we investigate the effects of warming and drought on the reproductive timing and output in loggerhead shrikes (Lanius ludovicianus) in central New Mexico from 2007 to 2012. We found increases in air temperature of 3 °C during the breeding season (March-July) and highly variable winter and annual precipitation. With increasing spring temperatures, shrikes advanced nesting phenology by 20 days over 6 years, a much higher rate than is reported for any other bird species. During this period, the number of breeding pairs also increased from 25 to 37, and clutch size and the number offspring produced per successful nest did not vary. Nest success, however, was often very low and ranged from 11 to 46%. Although our models indicated that low nest success was driven by precipitation and temperature, it was mediated indirectly through increased predation rates during the hot and dry periods.

Ensemble Downscaling of Winter Seasonal Forecasts: The MRED Project

NASA Astrophysics Data System (ADS)

Arritt, R. W.; Mred Team

2010-12-01

The Multi-Regional climate model Ensemble Downscaling (MRED) project is a multi-institutional project that is producing large ensembles of downscaled winter seasonal forecasts from coupled atmosphere-ocean seasonal prediction models. Eight regional climate models each are downscaling 15-member ensembles from the National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFS) and the new NASA seasonal forecast system based on the GEOS5 atmospheric model coupled with the MOM4 ocean model. This produces 240-member ensembles, i.e., 8 regional models x 15 global ensemble members x 2 global models, for each winter season (December-April) of 1982-2003. Results to date show that combined global-regional downscaled forecasts have greatest skill for seasonal precipitation anomalies during strong El Niño events such as 1982-83 and 1997-98. Ensemble means of area-averaged seasonal precipitation for the regional models generally track the corresponding results for the global model, though there is considerable inter-model variability amongst the regional models. For seasons and regions where area mean precipitation is accurately simulated the regional models bring added value by extracting greater spatial detail from the global forecasts, mainly due to better resolution of terrain in the regional models. Our results also emphasize that an ensemble approach is essential to realizing the added value from the combined global-regional modeling system.

Geo(spatial) Health Investigation of Rotavirus in an Endemic Region: Hydroclimatic Influences and Epidemiology of Rotavirus in Bangladesh

NASA Astrophysics Data System (ADS)

Hasan, M. A.; Akanda, A. S.; Jutla, A.; Colwell, R. R.

2016-12-01

Rotavirus is the leading cause of severe dehydrating diarrhea among children under 5. Over 80% of the approximate half a million child deaths every year occur in South Asia and sub-Saharan Africa alone. Although less explored than cholera as a climate driven and influenced global health problem, recent studies have showed that the disease shown strong seasonality and spatio-temporal variability depending on regional hydroclimatic and local environmental conditions. Understanding the epidemiology of this disease, especially the spatio-temporal incidence patterns with respect to environmental factors is vitally important to allow for identification of "hotspots", preventative preparations, and vaccination strategies to improve wellbeing of the vulnerable populations. With climate change, spatio-temporal signatures and footprints of the disease are changing along with increasing burden. However, a robust understanding of the relationships between rotavirus epidemiology and hydroclimatic drivers is yet to be developed. In this study, we evaluate the seasonality and epidemiologic characteristics of rotavirous infection and its spatio-temporal incidence patterns with respect to regional hydroclimatic variables and their extremes in an endemic region in South Asia. Hospital-based surveillance data from different geographic locations allowed us to explore the detailed spatial and temporal characteristics of rotavirus propagation under the influence of climate variables in both coastal and inland areas. The rotavirus transmission patterns show two peaks in a year in the capital city of Dhaka, where winter season (highest in January) shows a high peak and the July-August monsoon season shows a smaller peak. Correlation with climate variables revealed that minimum temperature has strong influence on the winter season outbreak, while rainfall extremes show a strong positive association with the secondary monsoon peak. Spatial analysis also revealed that humidity and soil wetness may influence the timing as drier areas experience earlier outbreaks than wetter areas. Accurate understanding of rotavirus propagation with respect to hydroclimatic and environmental variability can be utilized to establish global surveillance and forecast imminent risk of diarrheal outbreaks in vulnerable regions.

Implications of climate change on winter road networks in Ontario's Far North and northern Manitoba, Canada, based on climate model projections

NASA Astrophysics Data System (ADS)

Hori, Y.; Cheng, V. Y. S.; Gough, W. A.

2017-12-01

A network of winter roads in northern Canada connects a number of remote First Nations communities to all-season roads and rails. The extent of the winter road networks depends on the geographic features, socio-economic activities, and the numbers of remote First Nations so that it differs among the provinces. The most extensive winter road networks below the 60th parallel south are located in Ontario and Manitoba, serving 32 and 18 communities respectively. In recent years, a warmer climate has resulted in a shorter winter road season and an increase in unreliable road conditions; thus, limiting access among remote communities. This study focused on examining the future freezing degree-days (FDDs) accumulations during the winter road season at selected locations throughout Ontario's Far North and northern Manitoba using recent climate model projections from the multi-model ensembles of General Circulation Models (GCMs) under the Representative Concentration Pathway (RCP) scenarios. First, the non-parametric Mann-Kendall correlation test and the Theil-Sen method were used to identify any statistically significant trends between FDDs and time for the base period (1981-2010). Second, future climate scenarios are developed for the study areas using statistical downscaling methods. This study also examined the lowest threshold of FDDs during the winter road construction in a future period. Our previous study established the lowest threshold of 380 FDDs, which derived from the relationship between the FDDs and the opening dates of James Bay Winter Road near the Hudson-James Bay coast. Thus, this study applied the threshold measure as a conservative estimate of the minimum threshold of FDDs to examine the effects of climate change on the winter road construction period.

Climate change affects winter chill for temperate fruit and nut trees.

PubMed

Luedeling, Eike; Girvetz, Evan H; Semenov, Mikhail A; Brown, Patrick H

2011-01-01

Temperate fruit and nut trees require adequate winter chill to produce economically viable yields. Global warming has the potential to reduce available winter chill and greatly impact crop yields. We estimated winter chill for two past (1975 and 2000) and 18 future scenarios (mid and end 21st century; 3 Global Climate Models [GCMs]; 3 greenhouse gas emissions [GHG] scenarios). For 4,293 weather stations around the world and GCM projections, Safe Winter Chill (SWC), the amount of winter chill that is exceeded in 90% of all years, was estimated for all scenarios using the "Dynamic Model" and interpolated globally. We found that SWC ranged between 0 and about 170 Chill Portions (CP) for all climate scenarios, but that the global distribution varied across scenarios. Warm regions are likely to experience severe reductions in available winter chill, potentially threatening production there. In contrast, SWC in most temperate growing regions is likely to remain relatively unchanged, and cold regions may even see an increase in SWC. Climate change impacts on SWC differed quantitatively among GCMs and GHG scenarios, with the highest GHG leading to losses up to 40 CP in warm regions, compared to 20 CP for the lowest GHG. The extent of projected changes in winter chill in many major growing regions of fruits and nuts indicates that growers of these commodities will likely experience problems in the future. Mitigation of climate change through reductions in greenhouse gas emissions can help reduce the impacts, however, adaption to changes will have to occur. To better prepare for likely impacts of climate change, efforts should be undertaken to breed tree cultivars for lower chilling requirements, to develop tools to cope with insufficient winter chill, and to better understand the temperature responses of tree crops.

On the Past, Present, and Future of Eastern Boundary Upwelling Systems

NASA Astrophysics Data System (ADS)

Bograd, S. J.; Black, B.; Garcia-Reyes, M.; Rykaczewski, R. R.; Thompson, S. A.; Turley, B. D.; van der Sleen, P.; Sydeman, W. J.

2016-12-01

Coastal upwelling in Eastern Boundary Upwelling Systems (EBUS) drives high productivity and marine biodiversity and supports lucrative commercial fishing operations. Thus there is significant interest in understanding the mechanisms underlying variations in the upwelling process, its drivers, and potential changes relative to global warming. Here we review recent results from a combination of regional and global observations, reanalysis products, and climate model projections that describe variability in coastal upwelling in EBUS. Key findings include: (1) interannual variability in California Current upwelling occurs in two orthogonal seasonal modes: a winter/early spring mode dominated by interannual variability and a summer mode dominated by long-term increasing trend; (2) there is substantial coherence in year-to-year variability between this winter/spring upwelling mode and upper trophic level demographic processes, including fish growth rates (rockfish and salmon) and seabird phenology, breeding success and survival; (3) a meta-analysis of existing literature suggests consistency with the Bakun (1990) hypothesis that rising global greenhouse-gas concentrations would result in upwelling-favorable wind intensification; however, (4) an ensemble of coupled, global ocean-atmosphere models finds limited evidence for intensification of upwelling-favorable winds over the 21st century, although summertime winds near the poleward boundaries of climatalogical upwelling zones are projected to intensify. We will also review a new comparative research program between the California and Benguela Upwelling Systems, including efforts to understand patterns of change and variation between climate, upwelling, fish, and seabirds.

QBO Influence on Polar Stratospheric Variability in the GEOS Chemistry-Climate Model

NASA Technical Reports Server (NTRS)

Hurwitz, M. M.; Oman, L. D.; Li, F.; Slong, I.-S.; Newman, P. A.; Nielsen, J. E.

2010-01-01

The quasi-biennial oscillation modulates the strength of both the Arctic and Antarctic stratospheric vortices. Model and observational studies have found that the phase and characteristics of the quasi-biennial oscillation (QBO) contribute to the high degree of variability in the Arctic stratosphere in winter. While the Antarctic stratosphere is less variable, recent work has shown that Southern Hemisphere planetary wave driving increases in response to "warm pool" El Nino events that are coincident with the easterly phase of the QBO. These events hasten the breakup of the Antarctic polar vortex. The Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) is now capable of generating a realistic QBO, due a new parameterization of gravity wave drag. In this presentation, we will use this new model capability to assess the influence of the QBO on polar stratospheric variability. Using simulations of the recent past, we will compare the modeled relationship between QBO phase and mid-winter vortex strength with the observed Holton-Tan relation, in both hemispheres. We will use simulations of the 21 St century to estimate future trends in the relationship between QBO phase and vortex strength. In addition, we will evaluate the combined influence of the QBO and El Nino/Southern Oscillation (ENSO) on the timing of the breakup of the polar stratospheric vortices in the GEOS CCM. We will compare the influence of these two natural phenomena with trends in the vortex breakup associated with ozone recovery and increasing greenhouse gas concentrations.

Climate controls on streamflow variability in the Missouri River Basin

NASA Astrophysics Data System (ADS)

Wise, E.; Woodhouse, C. A.; McCabe, G. J., Jr.; Pederson, G. T.; St-Jacques, J. M.

2017-12-01

The Missouri River's hydroclimatic variability presents a challenge for water managers, who must balance many competing demands on the system. Water resources in the Missouri River Basin (MRB) have increasingly been challenged by the droughts and floods that have occurred over the past several decades and the potential future exacerbation of these extremes by climate change. Here, we use observed and modeled hydroclimatic data and estimated natural flow records to describe the climatic controls on streamflow in the upper and lower portions of the MRB, examine atmospheric and oceanic patterns associated with high- and low-flow years, and investigate trends in climate and streamflow over the instrumental period. Results indicate that the two main source regions for total outflow, in the uppermost and lowermost parts of the basin, are under the influence of very different sets of climatic controls. Winter precipitation, impacted by changes in zonal versus meridional flow from the Pacific Ocean, as well as spring precipitation and temperature, play a key role in surface water supply variability in the upper basin. Lower basin flow is significantly correlated with precipitation in late spring and early summer, indicative of Atlantic-influenced circulation variability affecting the flow of moisture from the Gulf of Mexico. The upper basin, with decreasing snowpack and streamflow and warming spring temperatures, will be less likely to provide important flow supplements to the lower basin in the future.

Interannual Variability in the Position and Strength of the East Asian Jet Stream and Its Relation to Large - scale Circulation

NASA Astrophysics Data System (ADS)

Chan, Duo; Zhang, Yang; Wu, Qigang

2013-04-01

East Asian Jet Stream (EASJ) is charactered by obvious interannual variability in strength and position (latitude), with wide impacts on East Asian climate in all seasons. In this study, two indices are established to measure the interannual variability in intensity and position of EAJS. Possible causing factors, including both local signals and non-local large-scale circulation, are examined using NCAP-NCAR reanalysis data to investigate their relations with jet variation. Our analysis shows that the relationship between the interannual variations of EASJ and these factors depends on seasons. In the summer, both the intensity and position of EASJ are closely related to the meridional gradient of local surface temperature, but display no apparent relationship with the larg-scale circulation. In cold seasons (autumn, winter and spring), both the local factor and the large-scale circulation, i.e. the Pacific/North American teleconnection pattern (PNA), play important roles in the interannual variability of the jet intensity. The variability in the jet position, however, is more correlated to the Arctic Oscillation (AO), especially in winter. Diagnostic analysis indicates that transient eddy activity plays an important role in connecting the interannual variability of EASJ position with AO.

Seasonal and interannual variability of surface CDOM in the South China Sea associated with El Niño

NASA Astrophysics Data System (ADS)

Ma, Jinfeng; Zhan, Haigang; Du, Yan

2011-04-01

Satellite imagery of SeaWiFS from October 1997 to November 2007 is used to investigate the dominant seasonal and interannual variations of the surface light absorption due to Colored Dissolved Organic Materials (CDOM) in the South China Sea (SCS). Results show that the spatial distribution of CDOM mimics the major features of the SCS basin-scale circulation. High values of CDOM are found in upwelling regions like southeast of Vietnam in summer and northwest of Luzon in winter. At a basin scale, CDOM is high in winter when upwelling is strong, solar shortwave radiation and stratification weak, and vertical mixing intense. Opposite conditions exist in spring and summer. Interannual variability of the basin-wide CDOM is characterized by abnormal troughs during the El Niño events. A strong relationship exists between the time series of the first EOF mode (for both winter and summer) and Niño 3.4 Index. Associations of these events with climatic and hydrographic properties (i.e. wind forcing, solar shortwave radiation, Ekman pumping, vertical mixing, sea surface height and temperature) are discussed.

The climate of the Common Era off the Iberian Peninsula

NASA Astrophysics Data System (ADS)

Abrantes, Fátima; Rodrigues, Teresa; Rufino, Marta; Salgueiro, Emília; Oliveira, Dulce; Gomes, Sandra; Oliveira, Paulo; Costa, Ana; Mil-Homens, Mário; Drago, Teresa; Naughton, Filipa

2017-12-01

The Mediterranean region is a climate hot spot, sensitive not only to global warming but also to water availability. In this work we document major temperature and precipitation changes in the Iberian Peninsula and margin during the last 2000 years and propose an interplay of the North Atlantic internal variability with the three atmospheric circulation modes (ACMs), (North Atlantic Oscillation (NAO), east atlantic (EA) and Scandinavia (SCAND)) to explain the detected climate variability. We present reconstructions of sea surface temperature (SST derived from alkenones) and on-land precipitation (estimated from higher plant n-alkanes and pollen data) in sedimentary sequences recovered along the Iberian Margin between the south of Portugal (Algarve) and the northwest of Spain (Galiza) (36 to 42° N). A clear long-term cooling trend, from 0 CE to the beginning of the 20th century, emerges in all SST records and is considered to be a reflection of the decrease in the Northern Hemisphere summer insolation that began after the Holocene optimum. Multi-decadal/centennial SST variability follows other records from Spain, Europe and the Northern Hemisphere. Warm SSTs throughout the first 1300 years encompass the Roman period (RP), the Dark Ages (DA) and the Medieval Climate Anomaly (MCA). A cooling initiated at 1300 CE leads to 4 centuries of colder SSTs contemporary with the Little Ice Age (LIA), while a climate warming at 1800 CE marks the beginning of the modern/Industrial Era. Novel results include two distinct phases in the MCA: an early period (900-1100 years) characterized by intense precipitation/flooding and warm winters but a cooler spring-fall season attributed to the interplay of internal oceanic variability with a positive phase in the three modes of atmospheric circulation (NAO, EA and SCAND). The late MCA is marked by cooler and relatively drier winters and a warmer spring-fall season consistent with a shift to a negative mode of the SCAND. The Industrial Era reveals a clear difference between the NW Iberia and the Algarve records. While off NW Iberia variability is low, the Algarve shows large-amplitude decadal variability with an inverse relationship between SST and river input. Such conditions suggest a shift in the EA mode, from negative between 1900 and 1970 CE to positive after 1970, while NAO and SCAND remain in a positive phase. The particularly noticeable rise in SST at the Algarve site by the mid-20th century (±1970), provides evidence for a regional response to the ongoing climate warming. The reported findings have implications for decadal-scale predictions of future climate change in the Iberian Peninsula.

Satellite-derived attributes of cloud vortex systems and their application to climate studies

NASA Technical Reports Server (NTRS)

Carleton, Andrew M.

1987-01-01

Defense Meteorological Satellite Program (DMSP) visible and infrared mosaics are analyzed in conjunction with synoptic meteorological observations of sea level pressure (SLP) and upper-air height to derive composite patterns of cyclonic cloud vortices for the Northern Hemisphere. The patterns reveal variations in the structure and implied dynamics of cyclonic systems at different stages of development that include: (1) increasing vertical symmetry of the lower-level and upper-air circulations and (2) decreasing lower-tropospheric thicknesses and temperature advection, associated with increasing age of the vortex. Cloud vortices are more intense in winter than in summer and typically reach maximum intensity in the short-lived prespiral signature stage. There are major structural differences among frontal wave, polar air, and 'instant occlusion' cyclogenesis types. Cyclones in the dissipation stage may reintensify (deepen), as denoted by the appearance in the imagery of an asymmetric cloud band or a tightened spiral vortex. The satellite-derived statistics on cloud vortex intensity, which are seasonal- and latitude- as well as type-dependent, are applied to a preliminary examination of the synoptic manifestations of seasonal climate variability. An apparently close relationship is found, for two winter and spring seasons, between Northern Hemisphere cyclonic activity and variations in cryosphere variables, particularly the extent of Arctic sea ice. The results may indicate that increased snow and ice extent accompany a southward displacement of cyclonic activity and/or a predominance of deeper systems. However, there is also a strong regional dependence to the ice-synoptics feedback. This study demonstrates the utility of high resolution meteorological satellite imagery for studies of climate variations (climate dynamics).

Inter-annual and spatial variability in hillslope runoff and mercury flux during spring snowmelt.

PubMed

Haynes, Kristine M; Mitchell, Carl P J

2012-08-01

Spring snowmelt is an important period of mercury (Hg) export from watersheds. Limited research has investigated the potential effects of climate variability on hydrologic and Hg fluxes during spring snowmelt. The purpose of this research was to assess the potential impacts of inter-annual climate variability on Hg mobility in forested uplands, as well as spatial variability in hillslope hydrology and Hg fluxes. We compared hydrological flows, Hg and solute mobility from three adjacent hillslopes in the S7 watershed of the Marcell Experimental Forest, Minnesota during two very different spring snowmelt periods: one following a winter (2009-2010) with severely diminished snow accumulation (snow water equivalent (SWE) = 48 mm) with an early melt, and a second (2010-2011) with significantly greater winter snow accumulation (SWE = 98 mm) with average to late melt timing. Observed inter-annual differences in total Hg (THg) and dissolved organic carbon (DOC) yields were predominantly flow-driven, as the proportion by which solute yields increased was the same as the increase in runoff. Accounting for inter-annual differences in flow, there was no significant difference in THg and DOC export between the two snowmelt periods. The spring 2010 snowmelt highlighted the important contribution of melting soil frost in the timing of a considerable portion of THg exported from the hillslope, accounting for nearly 30% of the THg mobilized. Differences in slope morphology and soil depths to the confining till layer were important in controlling the large observed spatial variability in hydrological flowpaths, transmissivity feedback responses, and Hg flux trends across the adjacent hillslopes.

A monsoon-like Southwest Australian circulation and its relation with rainfall in Southwest Western Australia

NASA Astrophysics Data System (ADS)

Feng, Juan; Li, Jianping; Li, Yun

2010-05-01

Using the NCEP/NCAR, ERA-40 reanalysis, and precipitation data from CMAP and Australian Bureau of Meteorology, the variability and circulation features influencing the southwest Western Australia (SWWA) winter rainfall are investigated. It is found that the climate of southwest Australia bears a strong seasonality in the annual cycle and exhibits a monsoon-like atmospheric circulation, which is termed as the southwest Australian circulation (SWAC) for its several distinct features characterizing a monsoonal circulation: the seasonal reversal of winds, alternate wet and dry seasons, and an evident land-sea thermal contrast. The seasonal march of the SWAC in extended winter (May to October) is demonstrated by pentad data. An index based on the dynamics normalized seasonality was introduced to describe the behavior and variation of the winter SWAC. It is found that the winter rainfall over SWWA has a significant positive correlation with the SWAC index in both early (May to July) and late (August to October) winter. In weaker winter SWAC years there is an anti-cyclonic anomaly over southern Indian Ocean resulting in weaker westerlies and northerlies which are not favorable for more rainfall over SWWA, and the opposite combination is true in the stronger winter SWAC years. The SWAC explains not only a large portion of the interannual variability of SWWA rainfall in both early and late winter, but also the long term drying trend over SWWA in early winter. The well-coupled SWAC-SWWA rainfall relationship seems to be largely independent of the well-known effects of large-scale atmospheric circulations such as the Southern Hemisphere Annular Mode (SAM), El Niño/Southern Oscillation (ENSO), Indian Ocean Dipole (IOD) and ENSO Modoki (EM). The result offers qualified support for the argument that the monsoon-like circulation may contribute to the rainfall decline in early winter over SWWA.

Mapping urban climate zones and quantifying climate behaviors--an application on Toulouse urban area (France).

PubMed

Houet, Thomas; Pigeon, Grégoire

2011-01-01

Facing the concern of the population to its environment and to climatic change, city planners are now considering the urban climate in their choices of planning. The use of climatic maps, such Urban Climate Zone‑UCZ, is adapted for this kind of application. The objective of this paper is to demonstrate that the UCZ classification, integrated in the World Meteorological Organization guidelines, first can be automatically determined for sample areas and second is meaningful according to climatic variables. The analysis presented is applied on Toulouse urban area (France). Results show first that UCZ differentiate according to air and surface temperature. It has been possible to determine the membership of sample areas to an UCZ using landscape descriptors automatically computed with GIS and remote sensed data. It also emphasizes that climate behavior and magnitude of UCZ may vary from winter to summer. Finally we discuss the influence of climate data and scale of observation on UCZ mapping and climate characterization. Copyright © 2011 Elsevier Ltd. All rights reserved.

Climate change impact on hydroclimate regimes and extremes over Andean basins in the central-southern Chile

NASA Astrophysics Data System (ADS)

Bozkurt, Deniz; Rojas, Maisa; Valdivieso, Jonás; Falvey, Mark

2015-04-01

We have assessed the impact of projected increases in temperature and decreased precipitation on variability and potential changes in hydroclimate regimes and extremes over Andean basins in the central-southern Chile (~30-40S). The altitude of the southern Andes in the study area has an average altitude of 5000 m in the north that decreases to 3000 m at the southern edge. Climatically the region has a Mediterranean-like climate with mainly winter precipitation that gradually increases southwards, from around 300 mm/yr to 1000 mm/yr. The region is home to most of the population in Chile (~10 mil. inhabitants), it has fertile and productive agriculture land, as well as hydro-electrical power plants. During the 20th Century the region has experienced a decreasing precipitation trend imbedded in important interannual and decadal scale variability. We have used gridded observed daily precipitation and temperatures to drive and validate the VIC macro-scale model over the region of interest at 0.25 x 0.25 degree resolution. Historical (1960-2005) and projected (RCP8.5, 2006-2099) daily precipitation and temperatures from 28 CMIP5 models are adjusted via a transfer function based on the gridded observed daily precipitation and temperature data. Adjusted time series are then used to drive the VIC model in order to present climate change projections. The hydrological model simulations foresee that drying is robust in the models and total annual runoff will decrease in the future (40-45% by the end of the century). Center timing of runoff tends to shift to earlier days (3-5 weeks by the end of the century). In some areas over the Andes winter runoff is projected to increase due to upward movement of zero isotherm. Moreover, reductions in the amount of snowpack and accelerated snowmelt lead to more pronounced increase in winter evapotranspiration over the same areas. The simulated 12-months Standardized Runoff Index (SRI) clearly shows severe persistent hydrological droughts without (or a few) wet spell interruptions by the end of the century. On the other hand, probability density function of annual maximum runoff over high elevations (>1000 m) and higher interannual variability of 3-months SRI indicate a possible increase in the probability of flood events.

Interannual variability of physical oceanographic characteristics of Gilbert Bay: A marine protected area in Labrador, Canada

NASA Astrophysics Data System (ADS)

Best, Sara; Lundrigan, Sarah; Demirov, Entcho; Wroblewski, Joe

2011-10-01

Gilbert Bay on the southeast coast of Labrador is the site of the first Marine Protected Area (MPA) established in the subarctic coastal zone of eastern Canada. The MPA was created to conserve a genetically distinctive population of Atlantic cod, Gadus morhua. This article presents results from a study of the interannual variability in atmospheric and physical oceanographic characteristics of Gilbert Bay over the period 1949-2006. We describe seasonal and interannual variability of the atmospheric parameters at the sea surface in the bay. The interannual variability of the atmosphere in the Gilbert Bay region is related to the North Atlantic Oscillation (NAO) and a recent warming trend in the local climate of coastal Labrador. The related changes in seawater temperature, salinity and sea-ice thickness in winter are simulated with a one-dimensional water column model, the General Ocean Turbulence Model (GOTM). A warming Gilbert Bay ecosystem would be favorable for cod growth, but reduced sea-ice formation during the winter months increases the danger of traveling across the bay by snowmobile.

Diverging seasonal extremes for ocean acidification during the twenty-first century

NASA Astrophysics Data System (ADS)

Kwiatkowski, Lester; Orr, James C.

2018-01-01

How ocean acidification will affect marine organisms depends on changes in both the long-term mean and the short-term temporal variability of carbonate chemistry1-8. Although the decadal-to-centennial response to atmospheric CO2 and climate change is constrained by observations and models1, 9, little is known about corresponding changes in seasonality10-12, particularly for pH. Here we assess the latter by analysing nine earth system models (ESMs) forced with a business-as-usual emissions scenario13. During the twenty-first century, the seasonal cycle of surface-ocean pH was attenuated by 16 ± 7%, on average, whereas that for hydrogen ion concentration [H+] was amplified by 81 ± 16%. Simultaneously, the seasonal amplitude of the aragonite saturation state (Ωarag) was attenuated except in the subtropics, where it was amplified. These contrasting changes derive from regionally varying sensitivities of these variables to atmospheric CO2 and climate change and to diverging trends in seasonal extremes in the primary controlling variables (temperature, dissolved inorganic carbon and alkalinity). Projected seasonality changes will tend to exacerbate the impacts of increasing [H+] on marine organisms during the summer and ameliorate the impacts during the winter, although the opposite holds in the high latitudes. Similarly, over most of the ocean, impacts from declining Ωarag are likely to be intensified during the summer and dampened during the winter.

Climate change is affecting altitudinal migrants and hibernating species.

PubMed

Inouye, D W; Barr, B; Armitage, K B; Inouye, B D

2000-02-15

Calendar date of the beginning of the growing season at high altitude in the Colorado Rocky Mountains is variable but has not changed significantly over the past 25 years. This result differs from growing evidence from low altitudes that climate change is resulting in a longer growing season, earlier migrations, and earlier reproduction in a variety of taxa. At our study site, the beginning of the growing season is controlled by melting of the previous winter's snowpack. Despite a trend for warmer spring temperatures the average date of snowmelt has not changed, perhaps because of the trend for increased winter precipitation. This disjunction between phenology at low and high altitudes may create problems for species, such as many birds, that migrate over altitudinal gradients. We present data indicating that this already may be true for American robins, which are arriving 14 days earlier than they did in 1981; the interval between arrival date and the first date of bare ground has grown by 18 days. We also report evidence for an effect of climate change on hibernation behavior; yellow-bellied marmots are emerging 38 days earlier than 23 years ago, apparently in response to warmer spring air temperatures. Migrants and hibernators may experience problems as a consequence of these changes in phenology, which may be exacerbated if climate models are correct in their predictions of increased winter snowfall in our study area. The trends we report for earlier formation of permanent snowpack and for a longer period of snow cover also have implications for hibernating species.

Climate change is affecting altitudinal migrants and hibernating species

PubMed Central

Inouye, David W.; Barr, Billy; Armitage, Kenneth B.; Inouye, Brian D.

2000-01-01

Calendar date of the beginning of the growing season at high altitude in the Colorado Rocky Mountains is variable but has not changed significantly over the past 25 years. This result differs from growing evidence from low altitudes that climate change is resulting in a longer growing season, earlier migrations, and earlier reproduction in a variety of taxa. At our study site, the beginning of the growing season is controlled by melting of the previous winter's snowpack. Despite a trend for warmer spring temperatures the average date of snowmelt has not changed, perhaps because of the trend for increased winter precipitation. This disjunction between phenology at low and high altitudes may create problems for species, such as many birds, that migrate over altitudinal gradients. We present data indicating that this already may be true for American robins, which are arriving 14 days earlier than they did in 1981; the interval between arrival date and the first date of bare ground has grown by 18 days. We also report evidence for an effect of climate change on hibernation behavior; yellow-bellied marmots are emerging 38 days earlier than 23 years ago, apparently in response to warmer spring air temperatures. Migrants and hibernators may experience problems as a consequence of these changes in phenology, which may be exacerbated if climate models are correct in their predictions of increased winter snowfall in our study area. The trends we report for earlier formation of permanent snowpack and for a longer period of snow cover also have implications for hibernating species. PMID:10677510

Precipitation variability in the winter rainfall zone of South Africa during the last 1400 yr linked to the austral westerlies

NASA Astrophysics Data System (ADS)

Stager, J. C.; Mayewski, P. A.; White, J.; Chase, B. M.; Neumann, F. H.; Meadows, M. E.; King, C. D.; Dixon, D. A.

2011-12-01

The austral westerlies strongly influence precipitation and ocean circulation in the southern temperate zone, with important consequences for cultures and ecosystems. Global climate models anticipate poleward contraction of the austral westerlies with future warming, but the available paleoclimate records that might test these models have been largely limited to South America, are not fully consistent with each other, and may be complicated by influences from other climatic factors. Here we present the first fine-interval diatom and sedimentological records from the winter rainfall region of South Africa, representing precipitation during the last 1400 yr. Inferred rainfall increased ~1400-1200 cal yr BP and most notably during the Little Ice Age with pulses centered on ~600, 530, 470, 330, 200, and 90 cal yr BP. Synchronous fluctuations in Antarctic ice core chemistry strongly suggest that these variations are linked to changes in the westerlies. Partial inconsistencies among South African and South American records warn against the simplistic application of local-scale histories to the Southern Hemisphere as a whole. Nonetheless, these findings in general do support model projections of increasing aridity in austral winter rainfall zones with future warming.

The boreal winter Madden-Julian Oscillation's influence on summertime precipitation in the greater Caribbean

NASA Astrophysics Data System (ADS)

Curtis, Scott; Gamble, Douglas W.

2016-07-01

Precipitation totals in the greater Caribbean are known to be affected by interannual variability. In particular, dry conditions in the spring-summer have been physically linked to the positive phase of North Atlantic Oscillation (NAO) in the literature. In this study, it was found through regression analysis that an active Madden-Julian Oscillation (MJO) in winter geographically focused over the Maritime Continent contributes to a positive NAO in March via the generation of Rossby waves in the Northern Hemisphere. Specifically, a negative Pacific-North American pattern develops in the winter and transitions to an Atlantic pattern in spring. The positive NAO is a transient feature of this evolving wave train, but a center of significant positive 200 hPa geopotential heights is entrenched over the southeast U.S. throughout the February to May time period and is manifested as high pressure at the surface. The southern flank of this system increases the speeds of the trade winds and leads to a cooling of the Caribbean sea surface temperatures and, thus, convection suppression and reduced precipitation. Thus, this study advances our understanding of the climate of the greater Caribbean by using climate teleconnections to relate the MJO to rainfall in the region.

Climate as a driver of continent-wide irruptions in boreal seed-eating birds (Invited)

NASA Astrophysics Data System (ADS)

Strong, C.; Zuckerberg, B.; Betancourt, J. L.

2013-12-01

Boreal seed-eating birds regularly breed and overwinter throughout Canada and Alaska, but every few years these species demonstrate impressive irruptive migrations out of the boreal forest and into more southerly regions. It is thought that irruptive migrations are inversely dependent on a circumboreally synchronized pattern of seed crop fluctuations in boreal trees; seed-eating boreal birds stay in the north when food is plentiful, but sojourn south when food is scarce. Because both seed production and bird irruptions are characterized by periodicity ranging from biennial to decadal cycles, there is a strong possibility that these ecological phenomena are driven by climate variability. Using over twenty years of data from Project FeederWatch (a national citizen science project), we found that 'super irruptions' are correlated with continent-wide irruptive events in pine siskin population, and that these irruptions are associated with multi-decadal climate variability of Pacific origin. We also investigate how climate variability may influence the distribution of boreal bird species across different regions of North America during winter, and evaluate results in the context of limited banding data to assess possible geographic pathways of irruptions.

Quantitative Analysis of Relevant Soil, Land-use and Climate Characteristics on Landscape Degradation in Hungary

NASA Astrophysics Data System (ADS)

Kertesz, Adam; Mika, Janos; Jakab, Gergely; Palinkas, Melinda

2017-04-01

The objective of our research is to survey degradation processes acting in each micro-region of Hungary in connection with geographical and climatic characteristics. A survey of land degradation processes has been carried out at medium scale (1:50 000) to identify the affected areas of the region. Over 18,000 rectangles of Hungary have been digitally characterised for several types of land degradation. Water-flow type gully erosion and soil-loss (RUSLE, 2015: Esdac-data) are studied for dependent variables in this study. USDA textural classes, available water capacity, bulk density, clay content, coarse fragments, silt content, sand content, soil parent material, soil texture, land-use type (Corine, 2012) are used for non-climatic variables. Some of these characteristics are quantified in a non-scalable way, so the first step was to arrange these qualitative codes or pseudo-numbers into monotonous order for including them into the following multi-regression analyses. Data available from the CarpatClim Project (www.carpatclim-eu.org/pages/home) for 1961-2010 are also used in their 50 years averages is seasonal and annual resolution. The selected variables from this gridded data set are global radiation, daily mean temperature, maximum and minimum temperature, number of extreme cold days (< 20 C), precipitation, extreme wet days (>20 mm), days with utilizable precipitation (>1mm/d), potential evapotranspiration, Palmer Index (PDSI), Palfai Index (PAI), relative humidity and wind speed at 10 m height. The gully erosion processes strongly depend on the investigated non-climatic variables, mostly on parent material and slope. The group of further climatic factors is formed by winter relative humidity, wind speed and all-year round Palmer index. Besides leading role of the above non-climatic factors, additional effects of the significant climate variables are difficult to interpret. Nevertheless, the partial effects of these climate variables are combined with future climate scenarios available from GCM and RCM studies for Hungary. The real climate change effects may likely be stronger, than those obtained by this combination, due to inter-dependences between the non-climatic factors and climate variations. The study has been supported by the OTKA-K108755 project.

Climate change and adverse health events: community perceptions from the Tanahu district of Nepal

NASA Astrophysics Data System (ADS)

Mishra, Shiva Raj; Mani Bhandari, Parash; Issa, Rita; Neupane, Dinesh; Gurung, Swadesh; Khanal, Vishnu

2015-03-01

Nepal is a country economically dependent on climate-sensitive industries. It is highly vulnerable to the environmental, social, economic and health impacts of climate change. The objective of this study is to explore community perceptions of climate variability and human health risks. In this letter, we present a cross sectional study conducted between August 2013 and July 2014 in the Tanahu district of Nepal. Our analysis is based on 258 face-to-face interviews with household heads utilizing structured questionnaires. Over half of the respondents (54.7%) had perceived a change in climate, 53.9% had perceived an increase in temperature in the summer and 49.2% had perceived an increase in rainfall during the rainy season. Half of the respondents perceived an increase in the number of diseases during the summer, 46.5% perceived an increase during the rainy season and 48.8% during winter. Only 8.9% of the respondents felt that the government was doing enough to prevent climate change and its impact on their community. Belonging to the Janajati (indigenous) ethnic group, living in a pakki, super-pakki house and belonging to poor or mid-level income were related to higher odds of perceiving climate variability. Illiterates were less likely to perceive climate variability. Respondents living in a pakki house, super-pakki, or those who were poor were more likely to perceive health risks. Illiterates were less likely to perceive health risks.

Investigating the Influence of Anthropogenic Forcing on Observed Mean and Extreme Sea Level Pressure Trends over the Mediterranean Region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barkhordarian, Armineh

We investigate whether the observed mean sea level pressure (SLP) trends over the Mediterranean region in the period from 1975 to 2004 are significantly consistent with what 17 models projected as response of SLP to anthropogenic forcing (greenhouse gases and sulphate aerosols, GS). Obtained results indicate that the observed trends in mean SLP cannot be explained by natural (internal) variability. Externally forced changes are detectable in all seasons, except spring. The large-scale component (spatial mean) of the GS signal is detectable in all the 17 models in winter and in 12 of the 17 models in summer. However, the small-scalemore » component (spatial anomalies about the spatial mean) of GS signal is only detectable in winter within 11 of the 17 models. We also show that GS signal has a detectable influence on observed decreasing (increasing) tendency in the frequencies of extremely low (high) SLP days in winter and that these changes cannot be explained by internal climate variability. While the detection of GS forcing is robust in winter and summer, there are striking inconsistencies in autumn, where analysis points to the presence of an external forcing, which is not GS forcing.« less

Investigating the Influence of Anthropogenic Forcing on Observed Mean and Extreme Sea Level Pressure Trends over the Mediterranean Region

DOE PAGES

Barkhordarian, Armineh

2012-01-01

We investigate whether the observed mean sea level pressure (SLP) trends over the Mediterranean region in the period from 1975 to 2004 are significantly consistent with what 17 models projected as response of SLP to anthropogenic forcing (greenhouse gases and sulphate aerosols, GS). Obtained results indicate that the observed trends in mean SLP cannot be explained by natural (internal) variability. Externally forced changes are detectable in all seasons, except spring. The large-scale component (spatial mean) of the GS signal is detectable in all the 17 models in winter and in 12 of the 17 models in summer. However, the small-scalemore » component (spatial anomalies about the spatial mean) of GS signal is only detectable in winter within 11 of the 17 models. We also show that GS signal has a detectable influence on observed decreasing (increasing) tendency in the frequencies of extremely low (high) SLP days in winter and that these changes cannot be explained by internal climate variability. While the detection of GS forcing is robust in winter and summer, there are striking inconsistencies in autumn, where analysis points to the presence of an external forcing, which is not GS forcing.« less

Storm-tracks interannual variability and large-scale climate modes

NASA Astrophysics Data System (ADS)

Liberato, Margarida L. R.; Trigo, Isabel F.; Trigo, Ricardo M.

2013-04-01

In this study we focus on the interannual variability and observed changes in northern hemisphere mid-latitude storm-tracks and relate them to large scale atmospheric circulation variability modes. Extratropical storminess, cyclones dominant paths, frequency and intensity have long been the object of climatological studies. The analysis of storm characteristics and historical trends presented here is based on the cyclone detecting and tracking algorithm first developed for the Mediterranean region (Trigo et al. 1999) and recently extended to a larger Euro-Atlantic region (Trigo 2006). The objective methodology, which identifies and follows individual lows as minima in SLP fields, fulfilling a set of conditions regarding the central pressure and the pressure gradient, is applied to the northern hemisphere 6-hourly geopotential data at 1000 hPa from the 20th Century Reanalyses (20CRv2) project and from reanalyses datasets provided by the European Centre for Medium-Range Weather Forecasts (ECMWF): ERA-40 and ERA Interim reanalyses. First, we assess the interannual variability and cyclone frequency trends for each of the datasets, for the 20th century and for the period between 1958 and 2002 using the highest spatial resolution available (1.125° x 1.125°) from the ERA-40 data. Results show that winter variability of storm paths, cyclone frequency and travel times is in agreement with the reported variability in a number of large-scale climate patterns (including the North Atlantic Oscillation, the East Atlantic Pattern and the Scandinavian Pattern). In addition, three storm-track databases are built spanning the common available extended winter seasons from October 1979 to March 2002. Although relatively short, this common period allows a comparison of systems represented in reanalyses datasets with distinct horizontal resolutions. This exercise is mostly focused on the key areas of cyclogenesis and cyclolysis and main cyclone characteristics over the northern hemisphere. Trigo IF., TD Davies, GR Bigg (1999) Objective climatology of cyclones in the Mediterranean region. J. Climate 12: 1685-1696. Trigo IF (2006) Climatology and interannual variability of storm-tracks in the Euro-Atlantic sector: a comparison between ERA-40 and NCEP/NCAR reanalyses. Clim. Dyn. 26: 127-143.

Wintertime East Asian Jet Stream and its Association with the Asian-Pacific-American Climate

NASA Technical Reports Server (NTRS)

Yang, Song; Lau, K.-M.; Kim, K.-M.

1999-01-01

The wintertime upper-tropospheric westerly jet stream over subtropical East Asia and western Pacific, often referred to as East Asian Jet (EAJ), is an important atmospheric circulation system in the Asian-Pacific-American (APA) region. It is characterized by variabilities on a wide range of time scales and exerts a strong impact on the weather and climate of the region. On the synoptic scale, the jet is closely linked to many phenomena such as cyclogenesis, frontogenesis, blocking, storm track activity, and the development of other atmospheric disturbances. On the seasonal time scale, the variation of the EAJ determines many characteristics of the seasonal transition of the atmospheric circulation over Asia. The variabilities of the jet on these time scales have been relatively well documented (e.g., Yeh et al. 1959, Palmen and Newton 1969; Zeng 1979). It has also been understood that the inter-annual variability of the EAJ is associated with many climate signals in the APA region. These signals include the persistent anomalies of the East Asian winter monsoon and the changes in diabatic heating and in the Hadley circulation (Bjerknes 1966; Chang and Lau 1980; Huang and Gambo 1982; Kang and Held 1986; Tao and Chen 1987; Lau et al. 1988; Yang and Webster 1990; Ding 1992; Webster and Yang 1992; Dong et al. 1999). However, many questions remain for the year-to-year variabilities of the jet and their relation to the APA climate. For example, what is the relationship between the EAJ and El Nino/Southern Oscillation (ENSO)? Will the jet and ENSO play different roles in modulating the APA climate? How is the jet linked to North Pacific sea surface temperature (SST) and the Pacific/North American (PNA) teleconnection pattern? In this study, we address several issues related to the wintertime EAJ with a focus on interannual time scales. We will examine the association between the jet core and ENSO, which has always been overshadowed by the relationship between ENSO and the upper-tropospheric winds over northern extratropics of the central Pacific. We will investigate the linkage of the jet to variabilities of the Asian winter monsoon, tropical convection, and upper tropospheric wave patterns. We will also explore the relationship between the jet core and extratropical S ST with an aim at providing helpful information for improving our understanding of the connection of the EAJ to surface boundary conditions. The analysis is expected to provide information that is helpful for improving regional climate predictions.

Rising synchrony controls western North American ecosystems.

PubMed

Black, Bryan A; van der Sleen, Peter; Di Lorenzo, Emanuele; Griffin, Daniel; Sydeman, William J; Dunham, Jason B; Rykaczewski, Ryan R; García-Reyes, Marisol; Safeeq, Mohammad; Arismendi, Ivan; Bograd, Steven J

2018-06-01

Along the western margin of North America, the winter expression of the North Pacific High (NPH) strongly influences interannual variability in coastal upwelling, storm track position, precipitation, and river discharge. Coherence among these factors induces covariance among physical and biological processes across adjacent marine and terrestrial ecosystems. Here, we show that over the past century the degree and spatial extent of this covariance (synchrony) has substantially increased, and is coincident with rising variance in the winter NPH. Furthermore, centuries-long blue oak (Quercus douglasii) growth chronologies sensitive to the winter NPH provide robust evidence that modern levels of synchrony are among the highest observed in the context of the last 250 years. These trends may ultimately be linked to changing impacts of the El Niño Southern Oscillation on midlatitude ecosystems of North America. Such a rise in synchrony may destabilize ecosystems, expose populations to higher risks of extinction, and is thus a concern given the broad biological relevance of winter climate to biological systems. © 2018 John Wiley & Sons Ltd.

Rising synchrony controls western North American ecosystems

USGS Publications Warehouse

Black, Bryan A.; van der Sleen, Peter; Di Lorenzo, Emanuele; Griffin, Daniel; Sydeman, William J.; Dunham, Jason B.; Rykaczewski, Ryan R.; Garcia-Reyes, Marisol; Safeeq, Mohammad; Arismendi, Ivan; Bograd, Steven J.

2018-01-01

Along the western margin of North America, the winter expression of the North Pacific High (NPH) strongly influences interannual variability in coastal upwelling, storm track position, precipitation, and river discharge. Coherence among these factors induces covariance among physical and biological processes across adjacent marine and terrestrial ecosystems. Here, we show that over the past century the degree and spatial extent of this covariance (synchrony) has substantially increased, and is coincident with rising variance in the winter NPH. Furthermore, centuries‐long blue oak (Quercus douglasii) growth chronologies sensitive to the winter NPH provide robust evidence that modern levels of synchrony are among the highest observed in the context of the last 250 years. These trends may ultimately be linked to changing impacts of the El Niño Southern Oscillation on mid‐latitude ecosystems of North America. Such a rise in synchrony may destabilize ecosystems, expose populations to higher risks of extinction, and is thus a concern given the broad biological relevance of winter climate to biological systems.

Water availability change in central Belgium for the late 21st century

NASA Astrophysics Data System (ADS)

Tabari, Hossein; Taye, Meron Teferi; Willems, Patrick

2015-08-01

We investigate the potential impact of climate change on water availability in central Belgium. Two water balance components being precipitation and potential evapotranspiration are initially projected for the late 21st century (2071-2100) based on 30 Coupled Models Intercomparison Project phase 5 (CMIP5) models relative to a baseline period of 1961-1990, assuming forcing by four representative concentration pathway emission scenarios (RCP2.6, RCP4.5, RCP6.0, RCP8.5). The future available water is then estimated as the difference between precipitation and potential evapotranspiration projections. The number of wet days and mean monthly precipitation for summer season is projected to decrease in most of the scenarios, while the projections show an increase in those variables for the winter months. Potential evapotranspiration is expected to increase during both winter and summer seasons. The results show a decrease in water availability for summer and an increase for winter, suggesting drier summers and wetter winters for the late 21st century in central Belgium.

Performance and carcass characteristics of steers fed with two levels of metabolizable energy intake during summer and winter season.

PubMed

Arias, R A; Keim, J P; Gandarillas, M; Velásquez, A; Alvarado-Gilis, C; Mader, T L

2018-05-22

Climate change is producing an increase on extreme weather events around the world such as flooding, drought and extreme ambient temperatures impacting animal production and animal welfare. At present, there is a lack of studies addressing the effects of climatic conditions associated with energy intake in finishing cattle in South American feed yards. Therefore, two experiments were conducted to assess the effects of environmental variables and level of metabolizable energy intake above maintenance requirements (MEI) on performance and carcass quality of steers. In each experiment (winter and summer), steers were fed with 1.85 or 2.72 times of their requirements of metabolizable energy of maintenance. A total of 24 crossbred steers per experiment were used and located in four pens (26.25 m2/head) equipped with a Calan Broadbent Feeding System. Animals were fed with the same diet within each season, varying the amount offered to adjust the MEI treatments. Mud depth, mud scores, tympanic temperature (TT), environmental variables, average daily gain, respiration rates and carcass characteristics plus three thermal comfort indices were collected. Data analysis considered a factorial arrangement (Season and MEI). In addition, a repeated measures analysis was performed for TT and respiration rate. Mean values of ambient temperature, solar radiation and comfort thermal indices were greater in the summer experiment as expected (P<0.005). The mean values of TT were higher in steers fed with higher MEI and also in the summer season. The average daily gain was greater during summer v. winter (1.10±0.11 v. 0.36±0.06) kg/day, also when steers were fed 2.72 v. 1.85 MEI level (0.89±0.12 v. 0.57±0.10) kg/day. In summer, respiration rate increased in 41.2% in the afternoon. In winter, muddy conditions increased with time of feeding, whereas wind speed and rainfall had significant effects on TT and average daily gain. We conclude that MEI and environmental variables have direct effects on the physiology and performance of steers, including TT and average daily gain, particularly during the winter. In addition, carcass characteristics were affected by season but not by the level of MEI. Finally, due to the high variability of data as well as the small number of animals assessed in these experiments, more studies on carcass characteristics under similar conditions are required.

Recent climate hiatus revealed dual control by temperature and drought on the stem growth of Mediterranean Quercus ilex.

PubMed

Lempereur, Morine; Limousin, Jean-Marc; Guibal, Frédéric; Ourcival, Jean-Marc; Rambal, Serge; Ruffault, Julien; Mouillot, Florent

2017-01-01

A better understanding of stem growth phenology and its climate drivers would improve projections of the impact of climate change on forest productivity. Under a Mediterranean climate, tree growth is primarily limited by soil water availability during summer, but cold temperatures in winter also prevent tree growth in evergreen forests. In the widespread Mediterranean evergreen tree species Quercus ilex, the duration of stem growth has been shown to predict annual stem increment, and to be limited by winter temperatures on the one hand, and by the summer drought onset on the other hand. We tested how these climatic controls of Q. ilex growth varied with recent climate change by correlating a 40-year tree ring record and a 30-year annual diameter inventory against winter temperature, spring precipitation, and simulated growth duration. Our results showed that growth duration was the best predictor of annual tree growth. We predicted that recent climate changes have resulted in earlier growth onset (-10 days) due to winter warming and earlier growth cessation (-26 days) due to earlier drought onset. These climatic trends partly offset one another, as we observed no significant trend of change in tree growth between 1968 and 2008. A moving-window correlation analysis revealed that in the past, Q. ilex growth was only correlated with water availability, but that since the 2000s, growth suddenly became correlated with winter temperature in addition to spring drought. This change in the climate-growth correlations matches the start of the recent atmospheric warming pause also known as the 'climate hiatus'. The duration of growth of Q. ilex is thus shortened because winter warming has stopped compensating for increasing drought in the last decade. Decoupled trends in precipitation and temperature, a neglected aspect of climate change, might reduce forest productivity through phenological constraints and have more consequences than climate warming alone. © 2016 John Wiley & Sons Ltd.

Attribution of UK Winter Floods to Anthropogenic Forcing

NASA Astrophysics Data System (ADS)

Schaller, N.; Alison, K.; Sparrow, S. N.; Otto, F. E. L.; Massey, N.; Vautard, R.; Yiou, P.; van Oldenborgh, G. J.; van Haren, R.; Lamb, R.; Huntingford, C.; Crooks, S.; Legg, T.; Weisheimer, A.; Bowery, A.; Miller, J.; Jones, R.; Stott, P.; Allen, M. R.

2014-12-01

Many regions of southern UK experienced severe flooding during the 2013/2014 winter. Simultaneously, large areas in the USA and Canada were struck by prolonged cold weather. At the time, the media and public asked whether the general rainy conditions over northern Europe and the cold weather over North America were caused by climate change. Providing an answer to this question is not trivial, but recent studies show that probabilistic event attribution is feasible. Using the citizen science project weather@home, we ran over 40'000 perturbed initial condition simulations of the 2013/2014 winter. These simulations fall into two categories: one set aims at simulating the world with climate change using observed sea surface temperatures while the second set is run with sea surface temperatures corresponding to a world that might have been without climate change. The relevant modelled variables are then downscaled by a hydrological model to obtain river flows. First results show that anthropogenic climate change led to a small but significant increase in the fractional attributable risk for 30-days peak flows for the river Thames. A single number can summarize the final result from probabilistic attribution studies indicating, for example, an increase, decrease or no change to the risk of the event occurring. However, communicating this to the public, media and other scientists remains challenging. The assumptions made in the chain of models used need to be explained. In addition, extreme events, like the UK floods of the 2013/2014 winter, are usually caused by a range of factors. While heavy precipitation events can be caused by dynamic and/or thermodynamic processes, floods occur only partly as a response to heavy precipitation. Depending on the catchment, they can be largely due to soil properties and conditions of the previous months. Probabilistic attribution studies are multidisciplinary and therefore all aspects need to be communicated properly.

The last millennium of Aleutian low variability based on dendrochonolgy and water isotope proxies

NASA Astrophysics Data System (ADS)

Gaglioti, B.; Mann, D. H.; Andreu-Hayles, L.; Wiles, G. C.; Streverler, G.; Williams, P.; Field, R. D.; D'Arrigo, R.

2017-12-01

How the wintertime Aleutian Low pressure system (AL) will respond to climate forcing is germane to the forest resources, glaciers, and fisheries in the North Pacific region. Recent work suggests the AL has strengthened over the last few centuries, and new, high-resolution paleo-records could help evaluate this trend. Namely, when it started, whether it has any historical precedents, and what it means for high-latitude climate feedbacks? Our study area is Southeast Alaska and the Southwest Yukon Territory, where the winters are warmer and wetter when the AL is stronger (deeper) and positioned further east. First, we use newly developed winter-sensitive tree-ring records to determine how AL variability has changed over the past 1000 years. During winters with a stronger AL, meridional flow brings: (i) heavy ice storms and snow loads to the coastal mountains that can injure sub-alpine trees; (ii) thaw events that can compromise growth in coastal forests; and (iii) changes in seasonality that can moderate the climate sensitivity of mid-elevation trees. Therefore, a time series of changing tree architecture in the mountains, tree ring widths in the lowlands, and running inter-series correlation in mid-slope chronologies collectively provide a landscape-level view of paleo-AL variability. Second, we compare and complement this dendro perspective with new proxy records based on stable oxygen isotope ratios measured in tree-ring and peat cellulose (d18O cell). To interpret how these proxies reflect the AL, we analyze the precipitation isotopes in Gustavus, Alaska over the past 16 months. We then use d18Ocell time series along a coastal to inland transect that records the degree of heavy-isotope rainout over the St. Elias Mountains, a factor that depends on the sources and pathways of the dominant storm tracks, which are influenced by the AL strength. We will present these new data in the context of existing AL reconstructions, and discuss the implications for the ongoing trends, and environmental corollaries of AL strength.

The Impact of Stratospheric Circulation Extremes on Minimum Arctic Sea Ice Extent

NASA Astrophysics Data System (ADS)

Smith, K. L.; Polvani, L. M.; Tremblay, B.

2017-12-01

The interannual variability of summertime Arctic sea ice extent (SIE) is anti-correlated with the leading mode of extratropical atmospheric variability in preceding winter, the Arctic Oscillation (AO). Given this relationship and the need for better seasonal predictions of Arctic SIE, we here examine the role of stratospheric circulation extremes and stratosphere-troposphere coupling in linking the AO and Arctic SIE variability. We show that extremes in the stratospheric circulation during the winter season, namely stratospheric sudden warming (SSW) and strong polar vortex (SPV) events, are associated with significant anomalies in sea ice concentration in the Bering Straight and the Sea of Okhotsk in winter, the Barents Sea in spring and along the Eurasian coastline in summer in both observations and a fully-coupled, stratosphere-resolving general circulation model. The accompanying figure shows the composite mean sea ice concentration anomalies from the Whole Atmosphere Community Climate Model (WACCM) for SSWs (N = 126, top row) and SPVs (N = 99, bottom row) for winter (a,d), spring (b,e) and summer (c,f). Consistent with previous work on the AO, we find that SSWs, which are followed by the negative phase of the AO at the surface, result in sea ice growth, whereas SPVs, which are followed by the positive phase of the AO at the surface, result in sea ice loss, although the dynamic and thermodynamic processes driving these sea ice anomalies in the three Arctic regions, noted above, are different. Our analysis suggests that the presence or absence of stratospheric circulation extremes in winter may play a non-trivial role in determining total September Arctic SIE when combined with other factors.

Multiannual forecasting of seasonal influenza dynamics reveals climatic and evolutionary drivers.

PubMed

Axelsen, Jacob Bock; Yaari, Rami; Grenfell, Bryan T; Stone, Lewi

2014-07-01

Human influenza occurs annually in most temperate climatic zones of the world, with epidemics peaking in the cold winter months. Considerable debate surrounds the relative role of epidemic dynamics, viral evolution, and climatic drivers in driving year-to-year variability of outbreaks. The ultimate test of understanding is prediction; however, existing influenza models rarely forecast beyond a single year at best. Here, we use a simple epidemiological model to reveal multiannual predictability based on high-quality influenza surveillance data for Israel; the model fit is corroborated by simple metapopulation comparisons within Israel. Successful forecasts are driven by temperature, humidity, antigenic drift, and immunity loss. Essentially, influenza dynamics are a balance between large perturbations following significant antigenic jumps, interspersed with nonlinear epidemic dynamics tuned by climatic forcing.

The impact of changing the land surface scheme in ACCESS(v1.0/1.1) on the surface climatology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kowalczyk, Eva A.; Stevens, Lauren E.; Law, Rachel M.

The Community Atmosphere Biosphere Land Exchange (CABLE) model has been coupled to the UK Met Office Unified Model (UM) within the existing framework of the Australian Community Climate and Earth System Simulator (ACCESS), replacing the Met Office Surface Exchange Scheme (MOSES). Here we investigate how features of the CABLE model impact on present-day surface climate using ACCESS atmosphere-only simulations. The main differences attributed to CABLE include a warmer winter and a cooler summer in the Northern Hemisphere (NH), earlier NH spring runoff from snowmelt, and smaller seasonal and diurnal temperature ranges. The cooler NH summer temperatures in canopy-covered regions aremore » more consistent with observations and are attributed to two factors. Firstly, CABLE accounts for aerodynamic and radiative interactions between the canopy and the ground below; this placement of the canopy above the ground eliminates the need for a separate bare ground tile in canopy-covered areas. Secondly, CABLE simulates larger evapotranspiration fluxes and a slightly larger daytime cloud cover fraction. Warmer NH winter temperatures result from the parameterization of cold climate processes in CABLE in snow-covered areas. In particular, prognostic snow density increases through the winter and lowers the diurnally resolved snow albedo; variable snow thermal conductivity prevents early winter heat loss but allows more heat to enter the ground as the snow season progresses; liquid precipitation freezing within the snowpack delays the building of the snowpack in autumn and accelerates snow melting in spring. Altogether we find that the ACCESS simulation of surface air temperature benefits from the specific representation of the turbulent transport within and just above the canopy in the roughness sublayer as well as the more complex snow scheme in CABLE relative to MOSES.« less

The impact of changing the land surface scheme in ACCESS(v1.0/1.1) on the surface climatology

DOE PAGES

Kowalczyk, Eva A.; Stevens, Lauren E.; Law, Rachel M.; ...

2016-08-23

The Community Atmosphere Biosphere Land Exchange (CABLE) model has been coupled to the UK Met Office Unified Model (UM) within the existing framework of the Australian Community Climate and Earth System Simulator (ACCESS), replacing the Met Office Surface Exchange Scheme (MOSES). Here we investigate how features of the CABLE model impact on present-day surface climate using ACCESS atmosphere-only simulations. The main differences attributed to CABLE include a warmer winter and a cooler summer in the Northern Hemisphere (NH), earlier NH spring runoff from snowmelt, and smaller seasonal and diurnal temperature ranges. The cooler NH summer temperatures in canopy-covered regions aremore » more consistent with observations and are attributed to two factors. Firstly, CABLE accounts for aerodynamic and radiative interactions between the canopy and the ground below; this placement of the canopy above the ground eliminates the need for a separate bare ground tile in canopy-covered areas. Secondly, CABLE simulates larger evapotranspiration fluxes and a slightly larger daytime cloud cover fraction. Warmer NH winter temperatures result from the parameterization of cold climate processes in CABLE in snow-covered areas. In particular, prognostic snow density increases through the winter and lowers the diurnally resolved snow albedo; variable snow thermal conductivity prevents early winter heat loss but allows more heat to enter the ground as the snow season progresses; liquid precipitation freezing within the snowpack delays the building of the snowpack in autumn and accelerates snow melting in spring. Altogether we find that the ACCESS simulation of surface air temperature benefits from the specific representation of the turbulent transport within and just above the canopy in the roughness sublayer as well as the more complex snow scheme in CABLE relative to MOSES.« less

Winter distribution and survival of a high-desert breeding population of canvasbacks

USGS Publications Warehouse

Kruse, K.L.; Lovvorn, J.R.; Takekawa, John Y.; MacKay, J.

2003-01-01

The southernmost major breeding area of Canvasbacks (Aythya valisineria) is located at the Ruby Lake National Wildlife Refuge, Nevada, in the high desert of the western Great Basin. We determined winter distributions, recovery rates, and survival for Canvasbacks banded in Nevada from March to November, 1968–2000. Winter recovery distributions did not differ by sex or age, but differed between direct recoveries (same year as banding) and indirect recoveries (after year of banding), indicating variable site use between years. Of direct band returns (October–March), 92% were from the Pacific Flyway and 56% were from California alone. In California, recovery distributions shifted from southern California and the San Francisco Bay estuary in the 1970s to the Central Valley in the 1980s and 1990s. In the 1990s, there were no recoveries in San Francisco Bay, historically the major wintering area for Canvasbacks in the Pacific Flyway. Adult and juvenile survival decreased by 24% between the 1980s and 1990s. Ruby Lake Canvasbacks exhibited weaker fidelity to wintering sites than Canvasbacks wintering on the Atlantic and Gulf coasts. Moreover, no major concentrations occurred during fall migration, unlike patterns in eastern North America. Shifts in distribution and survival may correspond to effects of El Niño weather on habitat conditions in Nevada and San Francisco Bay, and to major improvements in water delivery and wetland restoration in the Central Valley. Canvasbacks that use widely distributed and variable habitats may be good indicators of the effects of changing climate and water-use practices on waterbirds throughout this arid region.

Seasonal differences in melatonin concentrations and heart rates during sleep in obese subjects in Japan

NASA Astrophysics Data System (ADS)

Sato, Maki; Kanikowska, Dominika; Iwase, Satoshi; Shimizu, Yuuki; Nishimura, Naoki; Inukai, Yoko; Sato, Motohiko; Sugenoya, Junichi

2013-09-01

During the past several decades, obesity has been increasing globally. In Japan, obesity is defined by a BMI of 25 kg/m2 or over; 28.6 % of men and 20.6 % of women are obese. Obese people have an increased incidence of developing cardiovascular, renal, and hormonal diseases and sleep disorders. Obese people also have shortened sleep durations. We investigated seasonal differences in melatonin concentrations, heart rates, and heart rate variability during sleep in obese subjects in Japan. Five obese (BMI, 32.0 ± 4.9 kg/m2) and five non-obese (BMI, 23.2 ± 2.9 kg/m2) men participated in this study in the summer and winter. Electrocardiograms were measured continuously overnight in a climatic chamber at 26 °C with a relative humidity of 50 %. Saliva samples for melatonin were collected at 2300 hours, 0200 hours, and 0600 hours. We found that melatonin concentrations during sleep in obese subjects were significantly lower than those in non-obese subjects in the winter. Heart rate during sleep in winter was significantly higher than that in summer in both obese and non-obese subjects. Heart rate variability was not significantly different in the summer and winter in both obese and non-obese subjects. Our results show that decreased nocturnal melatonin concentrations during winter in obese men may be related to higher heart rates, and this may suggest that obese men are at an increased risk of a cardiovascular incident during sleep, especially in the winter.

Nineteenth Century Long-Term Instrumental Records, Examples From the Southeastern United States

NASA Astrophysics Data System (ADS)

Mock, C. J.

2001-12-01

Early instrumental records in the United States, defined as those operating before 1892 which is regarded the period prior to the modern climate record, provide a longer perspective of climatic variability at decadal and interannual timescales. Such reconstructions also provide a means of verification for other proxy data. This paper provides a American perspective of historical climatic research, emphasizing the urgent need to properly evaluate data quality and provide necessary corrections to make them compatible with the modern record. Different fixed observation times, different practices of weather instrument exposures, and statistical methods for calibration are the main issues in applying corrections and conducting proper climatic interpretations. I illustrate several examples on methodologies of this historical climatic research, focusing on the following in the Southeastern United States: daily reconstructed temperature time-series centered on Charleston SC and Natchez MS back to the late eighteenth century, and precipitation frequency reconstructions during the antebellum period for the Gulf Coast and coastal Southeast Atlantic states. Results indicate several prominent extremes unprecedented as compared to the modern record, such as the widespread warm winter of 1827-28, and the severe cold winters of 1856 and 1857. The reconstructions also yield important information concerning responses to past ENSO events, the PNA, NAO, and the PDO, particularly when compared with instrumental data from other regions. A high potential also exists for applying the climate reconstructions to assess historical climatic impacts on society in the Southeast, such as to understand climatic linkages to famous case studies of Yellow Fever epidemics and severe drought.

Skillful seasonal predictions of winter precipitation over southern China

NASA Astrophysics Data System (ADS)

Lu, Bo; Scaife, Adam A.; Dunstone, Nick; Smith, Doug; Ren, Hong-Li; Liu, Ying; Eade, Rosie

2017-07-01

Southern China experiences large year-to-year variability in the amount of winter precipitation, which can result in severe social and economic impacts. In this study, we demonstrate prediction skill of southern China winter precipitation by three operational seasonal prediction models: the operational Global seasonal forecasting system version 5 (GloSea5), the NCEP Climate Forecast System (CFSv2) and the Beijing Climate Center Climate System Model (BCC-CSM1.1m). The correlation scores reach 0.76 and 0.67 in GloSea5 and CFSv2, respectively; and the amplitude of the ensemble mean forecast signal is comparable to the observed variations. The skilful predictions in GloSea5 and CFSv2 mainly benefit from the successful representation of the observed ENSO teleconnection. El Niño weakens the Walker circulation and leads to the strengthening of the subtropical high over the northwestern Pacific. The anti-cyclone then induces anomalous northward flow over the South China Sea and brings water vapor to southern China, resulting in more precipitation. This teleconnection pattern is too weak in BCC-CSM1.1m, which explains its low skill (0.13). Whereas the most skilful forecast system is also able to simulate the influence of the Indian Ocean on southern China precipitation via changes in southwesterly winds over the Bay of Bengal. Finally, we examine the real-time forecast for 2015/16 winter when a strong El Niño event led to the highest rainfall over southern China in recent decades. We find that the GloSea5 system gave good advice as it produced the third wettest southern China in the hindcast, but underestimated the observed amplitude. This is likely due to the underestimation of the Siberian High strength in 2015/2016 winter, which has driven strong convergence over southern China. We conclude that some current seasonal forecast systems can give useful warning of impending extremes. However, there is still need for further model improvement to fully represent the complex dynamics of the region.

Drivers of Seasonal Variability in Marine Boundary Layer Aerosol Number Concentration Investigated Using a Steady State Approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohrmann, Johannes; Wood, Robert; McGibbon, Jeremy

Marine boundary layer (MBL) aerosol particles affect the climate through their interaction with MBL clouds. Although both MBL clouds and aerosol particles have pronounced seasonal cycles, the factors controlling seasonal variability of MBL aerosol particle concentration are not well-constrained. In this paper an aerosol budget is constructed representing the effects of wet deposition, free-tropospheric entrainment, primary surface sources, and advection on the MBL accumulation mode aerosol number concentration (N a). These terms are further parameterized, and by assuming that on seasonal timescales N a is in steady state, the budget equation is rearranged to form a diagnostic equation for Nmore » a based on observable variables. Using data primarily collected in the subtropical northeast Pacific during the MAGIC campaign (Marine ARM (Atmospheric Radiation Measurement) GPCI (GCSS Pacific Cross-section Intercomparison) Investigation of Clouds), estimates of both mean summer and winter N a concentrations are made using the simplified steady-state model and seasonal mean observed variables, and are found to match well with the observed N a. To attribute the modeled difference between summer and winter aerosol concentrations to individual observed variables (e.g. precipitation rate, free-tropospheric aerosol number concentration), a local sensitivity analysis is combined with the seasonal difference in observed variables. This analysis shows that despite wintertime precipitation frequency being lower than summer, the higher winter precipitation rate accounted for approximately 60% of the modeled seasonal difference in N a, which emphasizes the importance of marine stratocumulus precipitation in determining MBL aerosol concentrations on longer time scales.« less

Drivers of Seasonal Variability in Marine Boundary Layer Aerosol Number Concentration Investigated Using a Steady State Approach

DOE PAGES

Mohrmann, Johannes; Wood, Robert; McGibbon, Jeremy; ...

2018-01-21

Marine boundary layer (MBL) aerosol particles affect the climate through their interaction with MBL clouds. Although both MBL clouds and aerosol particles have pronounced seasonal cycles, the factors controlling seasonal variability of MBL aerosol particle concentration are not well-constrained. In this paper an aerosol budget is constructed representing the effects of wet deposition, free-tropospheric entrainment, primary surface sources, and advection on the MBL accumulation mode aerosol number concentration (N a). These terms are further parameterized, and by assuming that on seasonal timescales N a is in steady state, the budget equation is rearranged to form a diagnostic equation for Nmore » a based on observable variables. Using data primarily collected in the subtropical northeast Pacific during the MAGIC campaign (Marine ARM (Atmospheric Radiation Measurement) GPCI (GCSS Pacific Cross-section Intercomparison) Investigation of Clouds), estimates of both mean summer and winter N a concentrations are made using the simplified steady-state model and seasonal mean observed variables, and are found to match well with the observed N a. To attribute the modeled difference between summer and winter aerosol concentrations to individual observed variables (e.g. precipitation rate, free-tropospheric aerosol number concentration), a local sensitivity analysis is combined with the seasonal difference in observed variables. This analysis shows that despite wintertime precipitation frequency being lower than summer, the higher winter precipitation rate accounted for approximately 60% of the modeled seasonal difference in N a, which emphasizes the importance of marine stratocumulus precipitation in determining MBL aerosol concentrations on longer time scales.« less

Drivers of Seasonal Variability in Marine Boundary Layer Aerosol Number Concentration Investigated Using a Steady State Approach

NASA Astrophysics Data System (ADS)

Mohrmann, Johannes; Wood, Robert; McGibbon, Jeremy; Eastman, Ryan; Luke, Edward

2018-01-01

Marine boundary layer (MBL) aerosol particles affect the climate through their interaction with MBL clouds. Although both MBL clouds and aerosol particles have pronounced seasonal cycles, the factors controlling seasonal variability of MBL aerosol particle concentration are not well constrained. In this paper an aerosol budget is constructed representing the effects of wet deposition, free-tropospheric entrainment, primary surface sources, and advection on the MBL accumulation mode aerosol number concentration (Na). These terms are then parameterized, and by assuming that on seasonal time scales Na is in steady state, the budget equation is rearranged to form a diagnostic equation for Na based on observable variables. Using data primarily collected in the subtropical northeast Pacific during the MAGIC campaign (Marine ARM (Atmospheric Radiation Measurement) GPCI (GCSS Pacific Cross-Section Intercomparison) Investigation of Clouds), estimates of both mean summer and winter Na concentrations are made using the simplified steady state model and seasonal mean observed variables. These are found to match well with the observed Na. To attribute the modeled difference between summer and winter aerosol concentrations to individual observed variables (e.g., precipitation rate and free-tropospheric aerosol number concentration), a local sensitivity analysis is combined with the seasonal difference in observed variables. This analysis shows that despite wintertime precipitation frequency being lower than summer, the higher winter precipitation rate accounted for approximately 60% of the modeled seasonal difference in Na, which emphasizes the importance of marine stratocumulus precipitation in determining MBL aerosol concentrations on longer time scales.

Soil Moisture and Snow Cover: Active or Passive Elements of Climate?

NASA Technical Reports Server (NTRS)

Oglesby, Robert J.; Marshall, Susan; Robertson, Franklin R.; Roads, John O.; Arnold, James E. (Technical Monitor)

2001-01-01

A key question in the study of the hydrologic cycle is the extent to which surface effects such as soil moisture and snow cover are simply passive elements or whether they can affect the evolution of climate on seasonal and longer time scales. We have constructed ensembles of predictability studies using the NCAR CCM3 in which we compared the relative roles of initial surface and atmospheric conditions over the central and western U.S. GAPP region in determining the subsequent evolution of soil moisture and of snow cover. We have also made sensitivity studies with exaggerated soil moisture and snow cover anomalies in order to determine the physical processes that may be important. Results from simulations with realistic soil moisture anomalies indicate that internal climate variability may be the strongest factor, with some indication that the initial atmospheric state is also important. The initial state of soil moisture does not appear important, a result that held whether simulations were started in late winter or late spring. Model runs with exaggerated soil moisture reductions (near-desert conditions) showed a much larger effect, with warmer surface temperatures, reduced precipitation, and lower surface pressures; the latter indicating a response of the atmospheric circulation. These results suggest the possibility of a threshold effect in soil moisture, whereby an anomaly must be of a sufficient size before it can have a significant impact on the atmospheric circulation and hence climate. Results from simulations with realistic snow cover anomalies indicate that the time of year can be crucial. When introduced in late winter, these anomalies strongly affected the subsequent evolution of snow cover. When introduced in early winter, however, little or no effect is seen on the subsequent snow cover. Runs with greatly exaggerated initial snow cover indicate that the high reflectivity of snow is the most important process by which snow cover can impact climate, through lower surface temperatures and increased surface pressures. In early winter, the amount of solar radiation is very small and so this albedo, effect is inconsequential while in late winter, with the sun higher in the sky and period of daylight longer, the effect is much stronger. The results to date were obtained for model runs with present-day conditions. We are currently analyzing runs made with projected forcings for the 21st century to see if these results are modified in any way under likely scenarios of future climate change.

Emergence of the significant local warming of Korea in CMIP5 projections

NASA Astrophysics Data System (ADS)

Boo, Kyung-On; Shim, Sungbo; Kim, Jee-Eun

2016-04-01

According to IPCC AR5, anthropogenic influence on warming is obvious in local scales, especially in some tropical regions. Detection of significant local warming is important for adaptation to climate change of society and ecosystem. Recently much attention has focused on the time of emergence (ToE) for the signal of anthropogenic climate change against the natural climate variability. Motivated from the previous studies, this study analyzes ToE of regional surface air temperature over Korea. Simulations of CMIP5 15 models are used for RCP 2.6, 4.5 and 8.5. For each year, JJA and DJF temperature anomalies are calculated for the time period 1900-1929. For noise of interannual variability, natural-only historical simulations of CMIP5 12 models are used and the standard deviation of the time series is obtained. For signal of warming, we examine the year when the signal above 2 standard deviations is detected in 80% of the models using 30-year smoothed time series. According to our results, interannual variability is larger in land than ocean. Seasonally, it is larger in winter than in summer. Accordingly, ToE of summertime temperature is earlier than that in winter and is expected to appear in 2030s from three RCPs. The seasonal difference is consistent with previous studies. Wintertime ToE appears in 2040s for RCP85 and 2060s for RCP4.5. The different emergence time between RCP8.5 and RCP4.5 reflects the influence of mitigation. In a similar way, daily maximum and minimum temperatures are analyzed. ToE of Tmin appears earlier than that of Tmax and difference is small. Acknowledgements. This study is supported by the National Institute of Meteorological Sciences, Korea Meteorological Administration (NIMR-2012-B-2).

Downscaling of Global Climate Change Estimates to Regional Scales: An Application to Iberian Rainfall in Wintertime.

NASA Astrophysics Data System (ADS)

von Storch, Hans; Zorita, Eduardo; Cubasch, Ulrich

1993-06-01

A statistical strategy to deduct regional-scale features from climate general circulation model (GCM) simulations has been designed and tested. The main idea is to interrelate the characteristic patterns of observed simultaneous variations of regional climate parameters and of large-scale atmospheric flow using the canonical correlation technique.The large-scale North Atlantic sea level pressure (SLP) is related to the regional, variable, winter (DJF) mean Iberian Peninsula rainfall. The skill of the resulting statistical model is shown by reproducing, to a good approximation, the winter mean Iberian rainfall from 1900 to present from the observed North Atlantic mean SLP distributions. It is shown that this observed relationship between these two variables is not well reproduced in the output of a general circulation model (GCM).The implications for Iberian rainfall changes as the response to increasing atmospheric greenhouse-gas concentrations simulated by two GCM experiments are examined with the proposed statistical model. In an instantaneous `2 C02' doubling experiment, using the simulated change of the mean North Atlantic SLP field to predict Iberian rainfall yields, there is an insignificant increase of area-averaged rainfall of 1 mm/month, with maximum values of 4 mm/month in the northwest of the peninsula. In contrast, for the four GCM grid points representing the Iberian Peninsula, the change is 10 mm/month, with a minimum of 19 mm/month in the southwest. In the second experiment, with the IPCC scenario A ("business as usual") increase Of C02, the statistical-model results partially differ from the directly simulated rainfall changes: in the experimental range of 100 years, the area-averaged rainfall decreases by 7 mm/month (statistical model), and by 9 mm/month (GCM); at the same time the amplitude of the interdecadal variability is quite different.

Projecting 21st Century Snowpack Trends in the Western United States using Variable-Resolution CESM

NASA Astrophysics Data System (ADS)

Rhoades, A.; Huang, X.; Zarzycki, C. M.; Ullrich, P. A.

2015-12-01

The western USA is integrally reliant upon winter season snowpack, which supplies 3/4 of the region's fresh water and buffers against seasonal aridity on agricultural, ecosystem, and urban water demands. By the end of the 21st century, western USA snowpack (SWE) could decline by 40-70%, snowfall by 25-40%, more winter storms could tend towards rain rather than snow, and the peak timing of snowmelt will shift several weeks earlier in the season. Further, there has been evidence that mountain ranges could face more accelerated warming (elevational dependent warming) due to climate change. These future trends have largely been derived from global climate models (CMIP5) which can't resolve some of the more relatively narrow mountain ranges, like the California Sierra Nevada, in great detail. Therefore, due to the importance of orographic uplift on weather fronts, eastern Pacific sea-surface temperature anomalies, atmospheric river events, and mesoscale convective systems, high-resolution global scale modeling techniques are necessary to properly resolve western USA mountain range climatology. Variable-resolution global climate models (VRGCMs) are a promising next-generation technique to analyze both past and future hydroclimatic trends in the region. VRGCMs serve as a bridge between regional and global models by allowing for high-resolution in areas of interest, eliminate lateral boundary forcings (and resultant model biases), allow for more dynamically inclusive large-scale climate teleconnections, and require smaller simulation times and lower data storage demand (compared to conventional global models). This presentation focuses on validating these next-generation models as well as projecting future climate change scenario impacts on several of the western USA's key hydroclimate metrics (e.g., two-meter surface temperature, snow cover, snow water equivalent, and snowfall) to inform water managers and policy makers and offer resilience to climate change impacts facing the region.

Why were Past North Atlantic Warming Conditions Associated with Drier Climate in the Western United States?

NASA Astrophysics Data System (ADS)

Wong, C. I.; Potter, G. L.; Montanez, I. P.; Otto-Bliesner, B. L.; Behling, P.; Oster, J. L.

2014-12-01

Investigating climate dynamics governing rainfall over the western US during past warmings and coolings of the last glacial and deglaciation is pertinent to understanding how precipitation patterns might change with future global warming, especially as the processes driving the global hydrological reorganization affecting this drought-prone region during these rapid temperature changes remain unresolved. We present model climates of the Bølling warm event (14,500 years ago) and Younger Dryas cool event (12,200 years ago) that i) uniquely enable the assessment of dueling hypothesis about the atmospheric teleconnections responsible for abrupt temperature shifts in the North Atlantic region to variations in moisture conditions across the western US, and ii) show that existing hypotheses about these teleconnections are unsupported. Modeling results show no evidence for a north-south shift of the Pacific winter storm track, and we argue that a tropical moisture source with evolving trajectory cannot explain alternation between wet/dry conditions, which have been reconstructed from the proxy record. Alternatively, model results support a new hypothesis that variations in the intensity of the winter storm track, corresponding to its expansion/contraction, can account for regional moisture differences between warm and cool intervals of the last deglaciation. Furthermore, we demonstrate that the mechanism forcing the teleconnection between the North Atlantic and western US is the same across different boundary conditions. In our simulation, during the last deglaciation, and in simulations of future warming, perturbation of the Rossby wave structure reconfigures the atmospheric state. This reconfiguration affects the Aleutian Low and high-pressure ridge over and off of the northern North American coastline driving variability in the storm track. Similarity between the processes governing the climate response during these distinct time intervals illustrates the robust nature of the teleconnection, a novel result that provides context for understanding the climate processes governing the response of moisture variability to future climate change.

Controls on winter ecosystem respiration in temperate and boreal ecosystems

Treesearch

T. Wang; P. Ciais; S.L. Piao; C. Ottle; P. Brender; F. Maignan; A. Arain; A. Cescatti; D. Gianelle; C. Gough; L Gu; P. Lafleur; T. Laurila; B. Marcolla; H. Margolis; L. Montagnani; E. Moors; N. Saigusa; T. Vesala; G. Wohlfahrt; C. Koven; A. Black; E. Dellwik; A. Don; D. Hollinger; A. Knohl; R. Monson; J. Munger; A. Suyker; A. Varlagin; S. Verma

2011-01-01

Winter CO2 fluxes represent an important component of the annual carbon budget in northern ecosystems. Understanding winter respiration processes and their responses to climate change is also central to our ability to assess terrestrial carbon cycle and climate feedbacks in the future. However, the factors influencing the spatial and temporal...

Evaluating sub-seasonal skill in probabilistic forecasts of Atmospheric Rivers and associated extreme events

NASA Astrophysics Data System (ADS)

Subramanian, A. C.; Lavers, D.; Matsueda, M.; Shukla, S.; Cayan, D. R.; Ralph, M.

2017-12-01

Atmospheric rivers (ARs) - elongated plumes of intense moisture transport - are a primary source of hydrological extremes, water resources and impactful weather along the West Coast of North America and Europe. There is strong demand in the water management, societal infrastructure and humanitarian sectors for reliable sub-seasonal forecasts, particularly of extreme events, such as floods and droughts so that actions to mitigate disastrous impacts can be taken with sufficient lead-time. Many recent studies have shown that ARs in the Pacific and the Atlantic are modulated by large-scale modes of climate variability. Leveraging the improved understanding of how these large-scale climate modes modulate the ARs in these two basins, we use the state-of-the-art multi-model forecast systems such as the North American Multi-Model Ensemble (NMME) and the Subseasonal-to-Seasonal (S2S) database to help inform and assess the probabilistic prediction of ARs and related extreme weather events over the North American and European West Coasts. We will present results from evaluating probabilistic forecasts of extreme precipitation and AR activity at the sub-seasonal scale. In particular, results from the comparison of two winters (2015-16 and 2016-17) will be shown, winters which defied canonical El Niño teleconnection patterns over North America and Europe. We further extend this study to analyze probabilistic forecast skill of AR events in these two basins and the variability in forecast skill during certain regimes of large-scale climate modes.

Winter color polymorphisms identify global hot spots for evolutionary rescue from climate change.

PubMed

Mills, L Scott; Bragina, Eugenia V; Kumar, Alexander V; Zimova, Marketa; Lafferty, Diana J R; Feltner, Jennifer; Davis, Brandon M; Hackländer, Klaus; Alves, Paulo C; Good, Jeffrey M; Melo-Ferreira, José; Dietz, Andreas; Abramov, Alexei V; Lopatina, Natalia; Fay, Kairsten

2018-03-02

Maintenance of biodiversity in a rapidly changing climate will depend on the efficacy of evolutionary rescue, whereby population declines due to abrupt environmental change are reversed by shifts in genetically driven adaptive traits. However, a lack of traits known to be under direct selection by anthropogenic climate change has limited the incorporation of evolutionary processes into global conservation efforts. In 21 vertebrate species, some individuals undergo a seasonal color molt from summer brown to winter white as camouflage against snow, whereas other individuals remain brown. Seasonal snow duration is decreasing globally, and fitness is lower for winter white animals on snowless backgrounds. Based on 2713 georeferenced samples of known winter coat color-from eight species across trophic levels-we identify environmentally driven clinal gradients in winter coat color, including polymorphic zones where winter brown and white morphs co-occur. These polymorphic zones, underrepresented by existing global protected area networks, indicate hot spots for evolutionary rescue in a changing climate. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Linking crop yield anomalies to large-scale atmospheric circulation in Europe.

PubMed

Ceglar, Andrej; Turco, Marco; Toreti, Andrea; Doblas-Reyes, Francisco J

2017-06-15

Understanding the effects of climate variability and extremes on crop growth and development represents a necessary step to assess the resilience of agricultural systems to changing climate conditions. This study investigates the links between the large-scale atmospheric circulation and crop yields in Europe, providing the basis to develop seasonal crop yield forecasting and thus enabling a more effective and dynamic adaptation to climate variability and change. Four dominant modes of large-scale atmospheric variability have been used: North Atlantic Oscillation, Eastern Atlantic, Scandinavian and Eastern Atlantic-Western Russia patterns. Large-scale atmospheric circulation explains on average 43% of inter-annual winter wheat yield variability, ranging between 20% and 70% across countries. As for grain maize, the average explained variability is 38%, ranging between 20% and 58%. Spatially, the skill of the developed statistical models strongly depends on the large-scale atmospheric variability impact on weather at the regional level, especially during the most sensitive growth stages of flowering and grain filling. Our results also suggest that preceding atmospheric conditions might provide an important source of predictability especially for maize yields in south-eastern Europe. Since the seasonal predictability of large-scale atmospheric patterns is generally higher than the one of surface weather variables (e.g. precipitation) in Europe, seasonal crop yield prediction could benefit from the integration of derived statistical models exploiting the dynamical seasonal forecast of large-scale atmospheric circulation.

Historical floods reconstruction using NOAA 20CR global climate reanalysis over the last 150 years

NASA Astrophysics Data System (ADS)

Mathevet, T.; Brigode, P.; Jégonday, S.; Hingray, B.; Gailhard, J.; Wilhelm, B.

2017-12-01

Since several years, climatologists are producing long reanalysis for studying the variability of global climate over the last 150 years. For hydrologists, these datasets offer interesting opportunities for reconstructing historical flood events, and thus increasing the sample size used for flood frequency analysis. In this study, a streamflow reconstruction method based on the analogy of atmospheric situations (using NOAA 20CR reanalysis) for the reconstruction of climatic series and on a rainfall-runoff model for the streamflow reconstruction has been applied over different French catchments at the daily timestep. The studied catchments have been selected because of the availability of long observed streamflow series (used for quantifying the performances of the flood reconstructions) and for their different hydro-climatological regimes. Different methodologies have been tested for the reconstruction of daily climatic series over the 1851-2014 period, using geopotential heights and additional variables available within the 20CR reanalysis (relative humidity, precipitable water, etc.). Long observed climatic series have also been used when available as a reference for the climatic reconstructions. The different reconstruction methods have been finally ranked in terms of their historical flood reconstruction performances, quantified by flood types (autumn or winter floods) and atmospheric genesis (using a weather pattern classification). The obtained results indicate that using additional 20CR variables to the geopotential heights only slightly improve the flood reconstructions, while using observed climatic series improves significantly the flood reconstruction over the different catchments.

Climatic dipoles drive two principal modes of North American boreal bird irruption

PubMed Central

Strong, Courtenay; Zuckerberg, Benjamin; Betancourt, Julio L.; Koenig, Walter D.

2015-01-01

Pine Siskins exemplify normally boreal seed-eating birds that can be sparse or absent across entire regions of North America in one year and then appear in large numbers the next. These dramatic avian “irruptions” are thought to stem from intermittent but broadly synchronous seed production (masting) in one year and meager seed crops in the next. A prevalent hypothesis is that widespread masting in the boreal forest at high latitudes is driven primarily by favorable climate during the two to three consecutive years required to initiate and mature seed crops in most conifers. Seed production is expensive for trees and is much reduced in the years following masting, driving boreal birds to search elsewhere for food and overwintering habitat. Despite this plausible logic, prior efforts to discover climate-irruption relationships have been inconclusive. Here, analysis of more than 2 million Pine Siskin observations from Project FeederWatch, a citizen science program, reveals two principal irruption modes (North-South and West-East), both of which are correlated with climate variability. The North-South irruption mode is, in part, influenced by winter harshness, but the predominant climate drivers of both modes manifest in the warm season as continental-scale pairs of oppositely signed precipitation and temperature anomalies (i.e., dipoles). The climate dipoles juxtapose favorable and unfavorable conditions for seed production and wintering habitat, motivating a push-pull paradigm to explain irruptions of Pine Siskins and possibly other boreal bird populations in North America. PMID:25964328

Climate Change Affects Winter Chill for Temperate Fruit and Nut Trees

PubMed Central

Luedeling, Eike; Girvetz, Evan H.; Semenov, Mikhail A.; Brown, Patrick H.

2011-01-01

Background Temperate fruit and nut trees require adequate winter chill to produce economically viable yields. Global warming has the potential to reduce available winter chill and greatly impact crop yields. Methodology/Principal Findings We estimated winter chill for two past (1975 and 2000) and 18 future scenarios (mid and end 21st century; 3 Global Climate Models [GCMs]; 3 greenhouse gas emissions [GHG] scenarios). For 4,293 weather stations around the world and GCM projections, Safe Winter Chill (SWC), the amount of winter chill that is exceeded in 90% of all years, was estimated for all scenarios using the “Dynamic Model” and interpolated globally. We found that SWC ranged between 0 and about 170 Chill Portions (CP) for all climate scenarios, but that the global distribution varied across scenarios. Warm regions are likely to experience severe reductions in available winter chill, potentially threatening production there. In contrast, SWC in most temperate growing regions is likely to remain relatively unchanged, and cold regions may even see an increase in SWC. Climate change impacts on SWC differed quantitatively among GCMs and GHG scenarios, with the highest GHG leading to losses up to 40 CP in warm regions, compared to 20 CP for the lowest GHG. Conclusions/Significance The extent of projected changes in winter chill in many major growing regions of fruits and nuts indicates that growers of these commodities will likely experience problems in the future. Mitigation of climate change through reductions in greenhouse gas emissions can help reduce the impacts, however, adaption to changes will have to occur. To better prepare for likely impacts of climate change, efforts should be undertaken to breed tree cultivars for lower chilling requirements, to develop tools to cope with insufficient winter chill, and to better understand the temperature responses of tree crops. PMID:21629649

Direct and indirect climate controls predict heterogeneous early-mid 21st century wildfire burned area across western and boreal North America

PubMed Central

Falk, Donald A.; Westerling, Anthony L.; Swetnam, Thomas W.

2017-01-01

Predicting wildfire under future conditions is complicated by complex interrelated drivers operating across large spatial scales. Annual area burned (AAB) is a useful index of global wildfire activity. Current and antecedent seasonal climatic conditions, and the timing of snowpack melt, have been suggested as important drivers of AAB. As climate warms, seasonal climate and snowpack co-vary in intricate ways, influencing fire at continental and sub-continental scales. We used independent records of seasonal climate and snow cover duration (last date of permanent snowpack, LDPS) and cell-based Structural Equation Models (SEM) to separate direct (climatic) and indirect (snow cover) effects on relative changes in AAB under future climatic scenarios across western and boreal North America. To isolate seasonal climate variables with the greatest effect on AAB, we ran multiple regression models of log-transformed AAB on seasonal climate variables and LDPS. We used the results of multiple regressions to project future AAB using GCM ensemble climate variables and LDPS, and validated model predictions with recent AAB trends. Direct influences of spring and winter temperatures on AAB are larger and more widespread than the indirect effect mediated by changes in LDPS in most areas. Despite significant warming trends and reductions in snow cover duration, projected responses of AAB to early-mid 21st century are heterogeneous across the continent. Changes in AAB range from strongly increasing (one order of magnitude increases in AAB) to moderately decreasing (more than halving of baseline AAB). Annual wildfire area burned in coming decades is likely to be highly geographically heterogeneous, reflecting interacting regional and seasonal climate drivers of fire occurrence and spread. PMID:29244839

Direct and indirect climate controls predict heterogeneous early-mid 21st century wildfire burned area across western and boreal North America.

PubMed

Kitzberger, Thomas; Falk, Donald A; Westerling, Anthony L; Swetnam, Thomas W

2017-01-01

Predicting wildfire under future conditions is complicated by complex interrelated drivers operating across large spatial scales. Annual area burned (AAB) is a useful index of global wildfire activity. Current and antecedent seasonal climatic conditions, and the timing of snowpack melt, have been suggested as important drivers of AAB. As climate warms, seasonal climate and snowpack co-vary in intricate ways, influencing fire at continental and sub-continental scales. We used independent records of seasonal climate and snow cover duration (last date of permanent snowpack, LDPS) and cell-based Structural Equation Models (SEM) to separate direct (climatic) and indirect (snow cover) effects on relative changes in AAB under future climatic scenarios across western and boreal North America. To isolate seasonal climate variables with the greatest effect on AAB, we ran multiple regression models of log-transformed AAB on seasonal climate variables and LDPS. We used the results of multiple regressions to project future AAB using GCM ensemble climate variables and LDPS, and validated model predictions with recent AAB trends. Direct influences of spring and winter temperatures on AAB are larger and more widespread than the indirect effect mediated by changes in LDPS in most areas. Despite significant warming trends and reductions in snow cover duration, projected responses of AAB to early-mid 21st century are heterogeneous across the continent. Changes in AAB range from strongly increasing (one order of magnitude increases in AAB) to moderately decreasing (more than halving of baseline AAB). Annual wildfire area burned in coming decades is likely to be highly geographically heterogeneous, reflecting interacting regional and seasonal climate drivers of fire occurrence and spread.

The effect of climate on the phenology, acorn crop and radial increment of pedunculate oak (Quercus robur) in the middle Volga region, Tatarstan, Russia.

PubMed

Askeyev, O V; Tischin, D; Sparks, T H; Askeyev, I V

2005-03-01

Our data, collected in the extreme east of Europe, show that a significant biological effect of climate change has been experienced even in territories where temperature increase has been the lowest. This study documents the climatic response of pedunculate oak (Quercus robur) growing near its north-eastern limits in Europe. It demonstrates the potential of oak trees in old-growth forest to act as proxy climate indicators. Many factors may influence the temporal stability of the growth-climate, acorn crop-climate and first leafing-climate relationships. Climate data, climatic fluctuations, reproduction, genetics and tree-age may relate to this instability. Our results stress that an increase in climate variability or climatic warming resulting from warmer winters or summers could affect the oak population in eastern Europe in a similar way to that in western Europe. These findings, from remnants of oak forest in the middle Volga region of Russia, allow a further understanding of how species could be affected by future climates.

Impacts of climate change on growth period and planting boundaries of winter wheat in China under RCP4.5 scenario

NASA Astrophysics Data System (ADS)

Sun, Z.; Jia, S. F.; Lv, A. F.; Yang, K. J.; Svensson, J.; Gao, Y. C.

2015-10-01

This paper advances understanding of the impacts of climate change on crops in China by moving from ex-post analysis to forecasting, and by demonstrating how the effects of climate change will affect the growth period and the planting boundaries of winter wheat. Using a multiple regression model based on agricultural meteorological observations and the IPCC AR5 GCMs simulations, we find that the sowing date of winter wheat in the base period, 2040s and 2070s, shows a gradually delayed trend from north to south and the growth period of winter wheat in China will be shortened under climate change. The simulation results also show that (i) the north planting boundaries of winter wheat in China will likely move northward and expand westward in the future, while the south planting boundary will rise and spread in south Hainan and Taiwan; and (ii) the Xinjiang Uygur Autonomous Region and the Inner Mongolia Autonomous Region will have the largest increases in planting areas in 2040s and 2070s. Our simulation implies that Xinjiang and Inner Mongolia are more sensitive to climate change than other regions in China and priority should be given to design adaptation strategies for winter wheat planting for these provinces.

Warming effects on the urban hydrology in cold climate regions.

PubMed

Järvi, L; Grimmond, C S B; McFadden, J P; Christen, A; Strachan, I B; Taka, M; Warsta, L; Heimann, M

2017-07-19

While approximately 338 million people in the Northern hemisphere live in regions that are regularly snow covered in winter, there is little hydro-climatologic knowledge in the cities impacted by snow. Using observations and modelling we have evaluated the energy and water exchanges of four cities that are exposed to wintertime snow. We show that the presence of snow critically changes the impact that city design has on the local-scale hydrology and climate. After snow melt, the cities return to being strongly controlled by the proportion of built and vegetated surfaces. However in winter, the presence of snow masks the influence of the built and vegetated fractions. We show how inter-year variability of wintertime temperature can modify this effect of snow. With increasing temperatures, these cities could be pushed towards very different partitioning between runoff and evapotranspiration. We derive the dependency of wintertime runoff on this warming effect in combination with the effect of urban densification.

Forest productivity in southwestern Europe is controlled by coupled North Atlantic and Atlantic Multidecadal Oscillations.

PubMed

Madrigal-González, Jaime; Ballesteros-Cánovas, Juan A; Herrero, Asier; Ruiz-Benito, Paloma; Stoffel, Markus; Lucas-Borja, Manuel E; Andivia, Enrique; Sancho-García, Cesar; Zavala, Miguel A

2017-12-20

The North Atlantic Oscillation (NAO) depicts annual and decadal oscillatory modes of variability responsible for dry spells over the European continent. The NAO therefore holds a great potential to evaluate the role, as carbon sinks, of water-limited forests under climate change. However, uncertainties related to inconsistent responses of long-term forest productivity to NAO have so far hampered firm conclusions on its impacts. We hypothesize that, in part, such inconsistencies might have their origin in periodical sea surface temperature anomalies in the Atlantic Ocean (i.e., Atlantic Multidecadal Oscillation, AMO). Here we show strong empirical evidence in support of this hypothesis using 120 years of periodical inventory data from Iberian pine forests. Our results point to AMO + NAO + and AMO - NAO - phases as being critical for forest productivity, likely due to decreased winter water balance and abnormally low winter temperatures, respectively. Our findings could be essential for the evaluation of ecosystem functioning vulnerabilities associated with increased climatic anomalies under unprecedented warming conditions in the Mediterranean.

Nonlinear Response of the Stratosphere and the North Atlantic-European Climate to Global Warming

NASA Astrophysics Data System (ADS)

Manzini, E.; Karpechko, A. Yu.; Kornblueh, L.

2018-05-01

The response of the northern winter atmospheric circulation for two consecutive global warming periods of 2 K is examined in a grand ensemble (68 members) of idealized CO2 increase experiments performed with the same climate model. The comparison of the atmospheric responses for the two periods shows remarkable differences, indicating the nonlinearity of the response. The nonlinear signature of the atmospheric and surface responses is reminiscent of the positive phase of the annular mode of variability. The stratospheric vortex response shifts from an easterly wind change for the first 2 K to a westerly wind change for the second 2 K. The North Atlantic storm track shifts poleward only in the second period. A weaker November Arctic amplification during the second period suggests that differences in Arctic sea ice changes can act to trigger the atmospheric nonlinear response. Stratosphere-troposphere coupling thereafter can provide for the persistence of this nonlinearity throughout the winter.

Current temporal trends in moth abundance are counter to predicted effects of climate change in an assemblage of subarctic forest moths.

PubMed

Hunter, Mark D; Kozlov, Mikhail V; Itämies, Juhani; Pulliainen, Erkki; Bäck, Jaana; Kyrö, Ella-Maria; Niemelä, Pekka

2014-06-01

Changes in climate are influencing the distribution and abundance of the world's biota, with significant consequences for biological diversity and ecosystem processes. Recent work has raised concern that populations of moths and butterflies (Lepidoptera) may be particularly susceptible to population declines under environmental change. Moreover, effects of climate change may be especially pronounced in high latitude ecosystems. Here, we examine population dynamics in an assemblage of subarctic forest moths in Finnish Lapland to assess current trajectories of population change. Moth counts were made continuously over a period of 32 years using light traps. From 456 species recorded, 80 were sufficiently abundant for detailed analyses of their population dynamics. Climate records indicated rapid increases in temperature and winter precipitation at our study site during the sampling period. However, 90% of moth populations were stable (57%) or increasing (33%) over the same period of study. Nonetheless, current population trends do not appear to reflect positive responses to climate change. Rather, time-series models illustrated that the per capita rates of change of moth species were more frequently associated negatively than positively with climate change variables, even as their populations were increasing. For example, the per capita rates of change of 35% of microlepidoptera were associated negatively with climate change variables. Moth life-history traits were not generally strong predictors of current population change or associations with climate change variables. However, 60% of moth species that fed as larvae on resources other than living vascular plants (e.g. litter, lichen, mosses) were associated negatively with climate change variables in time-series models, suggesting that such species may be particularly vulnerable to climate change. Overall, populations of subarctic forest moths in Finland are performing better than expected, and their populations appear buffered at present from potential deleterious effects of climate change by other ecological forces. © 2014 John Wiley & Sons Ltd.

Climate change effects on extreme flows of water supply area in Istanbul: utility of regional climate models and downscaling method.

PubMed

Kara, Fatih; Yucel, Ismail

2015-09-01

This study investigates the climate change impact on the changes of mean and extreme flows under current and future climate conditions in the Omerli Basin of Istanbul, Turkey. The 15 regional climate model output from the EU-ENSEMBLES project and a downscaling method based on local implications from geophysical variables were used for the comparative analyses. Automated calibration algorithm is used to optimize the parameters of Hydrologiska Byråns Vattenbalansavdel-ning (HBV) model for the study catchment using observed daily temperature and precipitation. The calibrated HBV model was implemented to simulate daily flows using precipitation and temperature data from climate models with and without downscaling method for reference (1960-1990) and scenario (2071-2100) periods. Flood indices were derived from daily flows, and their changes throughout the four seasons and year were evaluated by comparing their values derived from simulations corresponding to the current and future climate. All climate models strongly underestimate precipitation while downscaling improves their underestimation feature particularly for extreme events. Depending on precipitation input from climate models with and without downscaling the HBV also significantly underestimates daily mean and extreme flows through all seasons. However, this underestimation feature is importantly improved for all seasons especially for spring and winter through the use of downscaled inputs. Changes in extreme flows from reference to future increased for the winter and spring and decreased for the fall and summer seasons. These changes were more significant with downscaling inputs. With respect to current time, higher flow magnitudes for given return periods will be experienced in the future and hence, in the planning of the Omerli reservoir, the effective storage and water use should be sustained.

Gray Wolves as Climate Change Buffers in Yellowstone

PubMed Central

Getz, Wayne M

2005-01-01

Understanding the mechanisms by which climate and predation patterns by top predators co-vary to affect community structure accrues added importance as humans exert growing influence over both climate and regional predator assemblages. In Yellowstone National Park, winter conditions and reintroduced gray wolves (Canis lupus) together determine the availability of winter carrion on which numerous scavenger species depend for survival and reproduction. As climate changes in Yellowstone, therefore, scavenger species may experience a dramatic reshuffling of food resources. As such, we analyzed 55 y of weather data from Yellowstone in order to determine trends in winter conditions. We found that winters are getting shorter, as measured by the number of days with snow on the ground, due to decreased snowfall and increased number of days with temperatures above freezing. To investigate synergistic effects of human and climatic alterations of species interactions, we used an empirically derived model to show that in the absence of wolves, early snow thaw leads to a substantial reduction in late-winter carrion, causing potential food bottlenecks for scavengers. In addition, by narrowing the window of time over which carrion is available and thereby creating a resource pulse, climate change likely favors scavengers that can quickly track food sources over great distances. Wolves, however, largely mitigate late-winter reduction in carrion due to earlier snow thaws. By buffering the effects of climate change on carrion availability, wolves allow scavengers to adapt to a changing environment over a longer time scale more commensurate with natural processes. This study illustrates the importance of restoring and maintaining intact food chains in the face of large-scale environmental perturbations such as climate change. PMID:15757363

Gray wolves as climate change buffers in Yellowstone.

PubMed

Wilmers, Christopher C; Getz, Wayne M

2005-04-01

Understanding the mechanisms by which climate and predation patterns by top predators co-vary to affect community structure accrues added importance as humans exert growing influence over both climate and regional predator assemblages. In Yellowstone National Park, winter conditions and reintroduced gray wolves (Canis lupus) together determine the availability of winter carrion on which numerous scavenger species depend for survival and reproduction. As climate changes in Yellowstone, therefore, scavenger species may experience a dramatic reshuffling of food resources. As such, we analyzed 55 y of weather data from Yellowstone in order to determine trends in winter conditions. We found that winters are getting shorter, as measured by the number of days with snow on the ground, due to decreased snowfall and increased number of days with temperatures above freezing. To investigate synergistic effects of human and climatic alterations of species interactions, we used an empirically derived model to show that in the absence of wolves, early snow thaw leads to a substantial reduction in late-winter carrion, causing potential food bottlenecks for scavengers. In addition, by narrowing the window of time over which carrion is available and thereby creating a resource pulse, climate change likely favors scavengers that can quickly track food sources over great distances. Wolves, however, largely mitigate late-winter reduction in carrion due to earlier snow thaws. By buffering the effects of climate change on carrion availability, wolves allow scavengers to adapt to a changing environment over a longer time scale more commensurate with natural processes. This study illustrates the importance of restoring and maintaining intact food chains in the face of large-scale environmental perturbations such as climate change.

Climate Change Across Seasons Experiment (CCASE): A new method for simulating future climate in seasonally snow-covered ecosystems.

PubMed

Templer, Pamela H; Reinmann, Andrew B; Sanders-DeMott, Rebecca; Sorensen, Patrick O; Juice, Stephanie M; Bowles, Francis; Sofen, Laura E; Harrison, Jamie L; Halm, Ian; Rustad, Lindsey; Martin, Mary E; Grant, Nicholas

2017-01-01

Climate models project an increase in mean annual air temperatures and a reduction in the depth and duration of winter snowpack for many mid and high latitude and high elevation seasonally snow-covered ecosystems over the next century. The combined effects of these changes in climate will lead to warmer soils in the growing season and increased frequency of soil freeze-thaw cycles (FTCs) in winter due to the loss of a continuous, insulating snowpack. Previous experiments have warmed soils or removed snow via shoveling or with shelters to mimic projected declines in the winter snowpack. To our knowledge, no experiment has examined the interactive effects of declining snowpack and increased frequency of soil FTCs, combined with soil warming in the snow-free season on terrestrial ecosystems. In addition, none have mimicked directly the projected increase in soil FTC frequency in tall statured forests that is expected as a result of a loss of insulating snow in winter. We established the Climate Change Across Seasons Experiment (CCASE) at Hubbard Brook Experimental Forest in the White Mountains of New Hampshire in 2012 to assess the combined effects of these changes in climate on a variety of pedoclimate conditions, biogeochemical processes, and ecology of northern hardwood forests. This paper demonstrates the feasibility of creating soil FTC events in a tall statured ecosystem in winter to simulate the projected increase in soil FTC frequency over the next century and combines this projected change in winter climate with ecosystem warming throughout the snow-free season. Together, this experiment provides a new and more comprehensive approach for climate change experiments that can be adopted in other seasonally snow-covered ecosystems to simulate expected changes resulting from global air temperature rise.

Climate Change Across Seasons Experiment (CCASE): A new method for simulating future climate in seasonally snow-covered ecosystems

PubMed Central

Templer, Pamela H.; Reinmann, Andrew B.; Sanders-DeMott, Rebecca; Sorensen, Patrick O.; Juice, Stephanie M.; Bowles, Francis; Sofen, Laura E.; Harrison, Jamie L.; Halm, Ian; Rustad, Lindsey; Martin, Mary E.; Grant, Nicholas

2017-01-01

Climate models project an increase in mean annual air temperatures and a reduction in the depth and duration of winter snowpack for many mid and high latitude and high elevation seasonally snow-covered ecosystems over the next century. The combined effects of these changes in climate will lead to warmer soils in the growing season and increased frequency of soil freeze-thaw cycles (FTCs) in winter due to the loss of a continuous, insulating snowpack. Previous experiments have warmed soils or removed snow via shoveling or with shelters to mimic projected declines in the winter snowpack. To our knowledge, no experiment has examined the interactive effects of declining snowpack and increased frequency of soil FTCs, combined with soil warming in the snow-free season on terrestrial ecosystems. In addition, none have mimicked directly the projected increase in soil FTC frequency in tall statured forests that is expected as a result of a loss of insulating snow in winter. We established the Climate Change Across Seasons Experiment (CCASE) at Hubbard Brook Experimental Forest in the White Mountains of New Hampshire in 2012 to assess the combined effects of these changes in climate on a variety of pedoclimate conditions, biogeochemical processes, and ecology of northern hardwood forests. This paper demonstrates the feasibility of creating soil FTC events in a tall statured ecosystem in winter to simulate the projected increase in soil FTC frequency over the next century and combines this projected change in winter climate with ecosystem warming throughout the snow-free season. Together, this experiment provides a new and more comprehensive approach for climate change experiments that can be adopted in other seasonally snow-covered ecosystems to simulate expected changes resulting from global air temperature rise. PMID:28207766

Wintertime East Asian Jet Stream and Its Association with the Asian-Pacific Climate

NASA Technical Reports Server (NTRS)

Yang, Song; Lau, K.-M.; Kim, K.-M.

2000-01-01

Interannual variability of the wintertime East Asian westerly jet stream and the linkage between this variability and the Asian-Pacific climate are investigated. The study emphasizes on the variability of the jet core and its association with the Asian winter monsoon, tropical convection, upper tropospheric wave patterns, and the teleconnection of the jet with other climate systems. The relationship between the jet and North Pacific sea surface temperature pattern (SST) is also explored. NCEP/NCAR reanalysis, NASA GISS surface temperature, NASA GEOS reanalysis, NOAA reconstructed SST, GPCP precipitation, and NOAA snow cover data sets are analyzed in this study. An index of the East Asian jet has been defined by the December-February means of the 200 mb zonal winds that are averaged within a box enclosing the jet maximum, which shifts only moderately from one year to another especially in the south-north direction. The jet links to a teleconnection pattern whose major climate anomalies appear over the Asian continent and western Pacific (west of the dateline). This pattern differs distinctly from the teleconnection pattern associated with El Nino/Southern Oscillation (ENSO), which causes the Pacific/North American pattern to the east of the dateline. A strong jet is accompanied clearly by an increase in the intensity of the atmospheric circulation over Asia and the Pacific. In particular, the winter monsoon strengthens over East Asia, leading to cold climate in the region, and convection intensifies over the tropical Asia-Australia sector. Changes in the jet are associated with broad-scale modification in the upper tropospheric wave patterns that leads to downstream climate anomalies over the eastern Pacific. Through this downstream influence, the East Asian jet causes climate signals in North America as well. A strong jet gives rise to warming and less snow cover in the western United States but reverse climate anomalies in the eastern part of the country, although these signals are relatively weaker than the jet-related anomalies in East Asia. There is a strong association between the East Asian jet and the North Pacific SST (NPSST). A strong jet is accompanied by a cooling in the extratropical Pacific and a warming in the tropical-subtropical Pacific. Evidence also indicates that the extratropical NPSST pattern plays a role in modulating the intensity of the jet stream. ENSO, the jet, and the NPSST are mutually interactive on certain time scales and such an interaction links closely to the climate anomalies in the Asian-Pacific-American regions.

Estimation of winter wheat canopy nitrogen density at different growth stages based on Multi-LUT approach

NASA Astrophysics Data System (ADS)

Li, Zhenhai; Li, Na; Li, Zhenhong; Wang, Jianwen; Liu, Chang

2017-10-01

Rapid real-time monitoring of wheat nitrogen (N) status is crucial for precision N management during wheat growth. In this study, Multi Lookup Table (Multi-LUT) approach based on the N-PROSAIL model parameters setting at different growth stages was constructed to estimating canopy N density (CND) in winter wheat. The results showed that the estimated CND was in line with with measured CND, with the determination coefficient (R2) and the corresponding root mean square error (RMSE) values of 0.80 and 1.16 g m-2, respectively. Time-consuming of one sample estimation was only 6 ms under the test machine with CPU configuration of Intel(R) Core(TM) i5-2430 @2.40GHz quad-core. These results confirmed the potential of using Multi-LUT approach for CND retrieval in winter wheat at different growth stages and under variables climatic conditions.

A 350-year reconstruction of the response of south Cascade Glacier to interannual and interdecadal climatic variability

Treesearch

Kailey W. Marcinkowski; David L. Peterson

2015-01-01

Mountain hemlock growth chronologies were used to reconstruct the mass balance of South Cascade Glacier, an alpine glacier in the North Cascade Range of Washington State. The net balance reconstruction spans 350 years, from 1659 to 2009. Summer and winter balances were reconstructed for 1346–2009 and 1615–2009, respectively. Relationships between mass balance and...

Attribution of declining Western U.S. Snowpack to human effects

USGS Publications Warehouse

Pierce, D.W.; Barnett, T.P.; Hidalgo, H.G.; Das, T.; Bonfils, Celine; Santer, B.D.; Bala, G.; Dettinger, M.D.; Cayan, D.R.; Mirin, A.; Wood, A.W.; Nozawa, T.

2008-01-01

Observations show snowpack has declined across much of the western United States over the period 1950-99. This reduction has important social and economic implications, as water retained in the snowpack from winter storms forms an important part of the hydrological cycle and water supply in the region. A formal model-based detection and attribution (D-A) study of these reductions is performed. The detection variable is the ratio of 1 April snow water equivalent (SWE) to water-year-to-date precipitation (P), chosen to reduce the effect of P variability on the results. Estimates of natural internal climate variability are obtained from 1600 years of two control simulations performed with fully coupled ocean-atmosphere climate models. Estimates of the SWE/P response to anthropogenic greenhouse gases, ozone, and some aerosols are taken from multiple-member ensembles of perturbation experiments run with two models. The D-A shows the observations and anthropogenically forced models have greater SWE/P reductions than can be explained by natural internal climate variability alone. Model-estimated effects of changes in solar and volcanic forcing likewise do not explain the SWE/P reductions. The mean model estimate is that about half of the SWE/P reductions observed in the west from 1950 to 1999 are the result of climate changes forced by anthropogenic greenhouse gases, ozone, and aerosols. ?? 2008 American Meteorological Society.

Pooled versus separate tree-ring δD measurements, and implications for reconstruction of the Arctic Oscillation in northwestern China.

PubMed

Liu, Xiaohong; An, Wenling; Treydte, Kerstin; Wang, Wenzhi; Xu, Guobao; Zeng, Xiaomin; Wu, Guoju; Wang, Bo; Zhang, Xuanwen

2015-04-01

Stable hydrogen isotope ratios (δD) in tree rings are an attractive but still rarely explored terrestrial archive of past climatic information. Because the preparation of the cellulose nitrate for δD measurements requires more wood and a longer preparation time than preparation techniques for other isotopes in cellulose (δ18O or δ13C), it is challenging to obtain high-resolution records, especially for slow-growing trees at high elevations and in boreal regions. Here, we tested whether annually pooled samples of Qinghai spruce (Picea crassifolia Kom.) trees from northwestern China provided results similar to those derived as the mean of individual measurements of the same trees and whether the resulting chronologies recorded useful climate information. Inter-tree variability of δD was higher than that of measured ring width for the same trees. We found higher and significant coherence between pooled and mean isotope chronologies than that among the individual series. It showed a logarithmic relationship between ring mass and δD; however, accounting for the influence of ring mass on δD values only slightly improved the strength of climatic signals in the pooled records. Tree-ring δD was significantly positively correlated with the mean, maximum, and minimum temperatures during the previous winter and with maximum temperature during the current August, and significantly negatively correlated with precipitation in the previous November to January and the current July. The winter climate signal seems to dominate tree-ring δD through the influence of large-scale atmospheric circulation patterns, i.e. the Arctic Oscillation. These results will facilitate reconstruction of winter atmospheric circulation patterns over northwestern China based on a regional tree-ring δD networks. Copyright © 2015 Elsevier B.V. All rights reserved.

Forcing of Climate Variations by Mev-gev Particles

NASA Technical Reports Server (NTRS)

Tinsley, Brian A.

1990-01-01

Changes in ionization production in the lower stratosphere by a few percent during Forbush decreases have been shown to correlate well with changes in winter tropospheric dynamics by a similar relatively small amount. Changes in ionization production by tens of percent on the decadal time scale have been shown to be correlated with changes in winter storm frequencies by tens of percent in the western North Atlantic. Changes in total solar irradiance or solar UV do not have time variations to match the tropospheric variations on the day to day time scales discussed here. Forcing related to magnetic activity is not supported. Thus solar wind/MeV-GeV particle changes appear to be the only viable forcing function for these day to day variations. If solar wind/particle forcing of a few percent amplitude can produce short term weather responses, then observed changes by tens of percent on the decadal and centennial time scale could produce climate changes on these longer time scales. The changes in circulation involved would produce regional climate changes, as observed. At present the relations between stratospheric ionization, electric fields and chemistry and aerosol and cloud microphysics are as poorly known as the relations between the latter and storm feedback processes. However, the capability for investigating these relationships now exists and has recently been most successfully used for elucidating the stratospheric chemistry and cloud microphysics associated with the Antarctic ozone hole. The economic benefits of being able to predict winter severity on an interannual basis, and the extent to which climate change related to solar variability will add to or substract from the greenhouse effect, should be more than adequate to justify support for research in this area.

Prevalence, behavioral manifestations and associated individual and climatic factors of seasonality in the Korean general population.

PubMed

Baek, Ji Hyun; Kim, Ji Sun; Huh, Iksoo; Lee, Kounseok; Park, Ju Hyun; Park, Taesung; Ha, Kyooseob; Hong, Kyung Sue

2015-02-01

Seasonality, an individual trait of seasonal variations in mood and behavior, has received clinical attention for its association with mood disorders. This study aimed to explore the prevalence, specific manifestation, and associated individual and climatic factors of seasonality in the non-elderly adult population. Five hundred fifty-two participants [male n=220; female n=332; mean age 34.92years, standard deviation (SD) 10.18] with no psychiatric history were recruited from the Seoul metropolitan area (37°33'58.87″N 126°58'40.63″E). Seasonality was evaluated using the Seasonal Pattern Assessment Questionnaire. Climatic variables used in analyses were averaged over recent 5years (from 2008 to 2013) on a monthly basis. The mean global seasonality score (GSS) was 5.53 (SD 3.91), and 16.2% (n=89) of participants had seasonal affective disorder (SAD) or sub-SAD. The "feeling worst" month in most of the participants with significant seasonality were winter (41.6%) or summer (38.2%). Socio-demographic factors including age and sex were not related to the seasonality. Decreased sunlight amount and diurnal temperature range in a given and previous month, and increased humidity in a previous month showed significant associations with the percentage of participants with the worst mood. The most frequently reported symptom related to seasonality was 'changes in energy level'. Specific manifestations were not significantly different between the winter type and the summer type. The summer and winter type seasonality in the non-clinical adult population did not differ in terms of behavioral manifestations. Decreased sunlight amount, diurnal temperature range, and increased humidity appeared to be major climatic factors associated with seasonality. Copyright © 2014 Elsevier Inc. All rights reserved.

Deacclimation may be crucial for winter survival of cereals under warming climate.

PubMed

Rapacz, Marcin; Jurczyk, Barbara; Sasal, Monika

2017-03-01

Climate warming can change the winter weather patterns. Warmer temperatures during winter result in a lower risk of extreme freezing events. On the other hand the predicted warm gaps during winter will decrease their freezing tolerance. Both contradict effects will affect winter survival but their resultant effect is unclear. In this paper, we demonstrate that climate warming may result in a decrease in winter survival of plants. A field study of winterhardiness of common wheat and triticale was established at 11 locations and repeated during three subsequent winters. The freezing tolerance of the plants was studied after controlled cold acclimation and de-acclimation using both plant survival analysis and chlorophyll fluorescence measurements. Cold deacclimation resistance was shown to be independent from cold acclimation ability. Further, cold deacclimation resistance appeared to be crucial for overwintering when deacclimation conditions occurred in the field. The shortening of uninterrupted cold acclimation may increase cold deacclimation efficiency, which could threaten plant survival during warmer winters. Measurements of chlorophyll fluorescence transient showed some differences triggered by freezing before and after deacclimation. We conclude that cold deacclimation resistance should be considered in the breeding of winter cereals and in future models of winter damage risk. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Relationship between Climate Variability, Wildfire Risk, and Wildfire Occurrence in Wildland-Urban Interface of the Southwestern United States

NASA Astrophysics Data System (ADS)

Kafatos, M.; Kim, S. H.; Jia, S.; Nghiem, S. V.

2017-12-01

As housing units in or near wildlands have grown, the wildland-urban interface (WUI) contain at present approximately one-third of all housing in the contiguous US. Wildfires are a part of the natural cycle in the Southwestern United States (SWUS) but the increasing trend of WUI has made wildfires a serious high-risk hazard. The expansion of WUI has elevated wildfire risks by increasing the chance of human caused ignitions and past fire suppression in the area. Previous studies on climate variability have shown that the SWUS region is prone to frequent droughts and has suffered from severe wildfires in the recent decade. Therefore, assessing the increased vulnerability to the wildfire in WUI is crucial for proactive adaptation under climate change. Our previous study has shown that a strong correlation between North Atlantic Oscillation (NAO) and temperature was found during March-June in the SWUS. The abnormally warm and dry spring conditions, combined with suppression of winter precipitation, can cause an early start of a fire season and high fire risk throughout the summer and fall. Therefore, it is crucial to investigate the connections between climate variability and wildfire danger characteristics. This study aims to identify climate variability using multiple climate indices such as NAO, El Niño-Southern Oscillation and the Pacific Decadal Oscillation closely related with droughts in the SWUS region. Correlation between the variability and fire frequency and severity in WUI were examined. Also, we investigated climate variability and its relationship on local wildfire potential using both Keetch-Byram Drought Index (KBDI) and Fire Weather Index (FWI) which have been used to assessing wildfire potential in the U.S.A and Canada, respectively. We examined the long-term variability of the fire potential indices and relationships between the indices and historical occurrence in WUI using multi-decadal reanalysis data sets. Following our analysis, we investigated joint impacts of multiple climate indices on droughts and human activities in the WUI for regional wildfire potential.

Response of wheat yield in Spain to large-scale patterns

NASA Astrophysics Data System (ADS)

Hernandez-Barrera, Sara; Rodriguez-Puebla, Concepcion

2016-04-01

Crops are vulnerable to extreme climate conditions as drought, heat stress and frost risk. In previous study we have quantified the influence of these climate conditions for winter wheat in Spain (Hernandez-Barrera et al. 2015). The climate extremes respond to large-scale atmospheric and oceanic patterns. Therefore, a question emerges in our investigation: How large-scale patterns affect wheat yield? Obtaining and understanding these relationships require different approaches. In this study, we first obtained the leading mode of observed wheat yield variability to characterize the common variability over different provinces in Spain. Then, the wheat variability is related to different modes of mean sea level pressure, jet stream and sea surface temperature by using Partial Least-Squares, which captures the relevant climate drivers accounting for variations in wheat yield from sowing to harvesting. We used the ERA-Interim reanalysis data and the Extended Reconstructed Sea Surface Temperature (SST) (ERSST v3b). The derived model provides insight about the teleconnections between wheat yield and atmospheric and oceanic circulations, which is considered to project the wheat yield trend under global warming using outputs of twelve climate models corresponding to the Coupled Models Intercomparison Project phase 5 (CMIP5). Hernandez-Barrera S., C. Rodríguez-Puebla and A.J. Challinor. Effects of diurnal temperature range and drought on wheat yield in Spain. Theoretical and Applied Climatology (submitted)

Application of Remote Sensing to Assess the Impact of Short Term Climate Variability on Coastal Sedimentation

NASA Technical Reports Server (NTRS)

Moeller, Christopher C.; Gunshor, Mathew M.; Menzel, W. Paul; Huh, Oscar K.; Walker, Nan D.; Rouse, Lawrence J.; Frey, Herbert V. (Technical Monitor)

2001-01-01

The University of Wisconsin and Louisiana State University have teamed to study the forcing of winter season cold frontal wind systems on sediment distribution patterns and geomorphology in the Louisiana coastal zone. Wind systems associated with cold fronts have been shown to modify coastal circulation and resuspend sediments along the microtidal Louisiana coast. The assessment includes quantifying the influence of cumulative winter season atmospheric forcing (through surface wind observations) from year to year in response to short term climate variability, such as El Nino events. A correlation between winter cyclone frequency and the strength of El Nino events has been suggested. The atmospheric forcing data are being correlated to geomorphic measurements along western Louisiana's prograding muddy coast. Remote sensing data is being used to map and track sediment distribution patterns for various wind conditions. Transferring a suspended sediment concentration (SSC) algorithm to EOS MODIS observations will enable estimates of SSC in case 2 waters over the global domain. Progress in Year 1 of this study has included data collection and analysis of wind observations for atmospheric forcing characterization, a field activity (TX-2001) to collect in situ water samples with co-incident remote sensing measurements from the NASA ER-2 based MODIS Airborne Simulator (MAS) and the EOS Terra based MODerate resolution Imaging Spectroradiometer (MODIS) instruments, aerial photography and of sediment burial pipe field measurements along the prograding muddy Chenier Plain coast of western Louisiana for documenting coastal change in that dynamic region, and routine collection of MODIS 250 in resolution data for monitoring coastal sediment patterns. The data sets are being used in a process to transfer an SSC estimation algorithm to the MODIS platform. Work is underway on assessing coastal transport for the winter 2000-01 season. Water level data for use in a Geomorphic Impact Index, which relates wind energy, water level conditions, and geomorphic change along the microtidal western Louisiana coastline is being assembled.

Descriptive modelling to predict deoxynivalenol in winter wheat in the Netherlands.

PubMed

Van Der Fels-Klerx, H J; Burgers, S L G E; Booij, C J H

2010-05-01

Predictions of deoxynivalenol (DON) content in wheat at harvest can be useful for decision-making by stakeholders of the wheat feed and food supply chain. The objective of the current research was to develop quantitative predictive models for DON in mature winter wheat in the Netherlands for two specific groups of end-users. One model was developed for use by farmers in underpinning Fusarium spp. disease management, specifically the application of fungicides around wheat flowering (model A). The second model was developed for industry and food safety authorities, and considered the entire wheat cultivation period (model B). Model development was based on observational data collected from 425 fields throughout the Netherlands between 2001 and 2008. For each field, agronomical information, climatic data and DON levels in mature wheat were collected. Using multiple regression analyses, the set of biological relevant variables that provided the highest statistical performance was selected. The two final models include the following variables: region, wheat resistance level, spraying, flowering date, several climatic variables in the different stages of wheat growing, and length of the period between flowering and harvesting (model B only). The percentages of variance accounted for were 64.4% and 65.6% for models A and B, respectively. Model validation showed high correlation between the predicted and observed DON levels. The two models may be applied by various groups of end-users to reduce DON contamination in wheat-derived feed and food products and, ultimately, reduce animal and consumer health risks.

Analysis of induction and establishment of dwarf bunt of wheat under marginal climatic conditions.

USDA-ARS?s Scientific Manuscript database

Dwarf bunt caused by Tilletia contraversa is a disease of winter wheat that has a limited geographic distribution due to specific winter climate requirements. The pathogen is listed as a quarantine organism by several countries that may have wheat production areas with inadequate or marginal climat...

Past climate variability between 97 and 7 ka reconstructed from a multi proxy speleothem record from Western Cuba

NASA Astrophysics Data System (ADS)

Winterhalder, Sophie; Scholz, Denis; Mangini, Augusto; Spötl, Christoph; Jochum, Klaus Peter; Pajón, Jesús M.

2016-04-01

The tropical hydrological cycle plays a key role in regulating global climate, mainly through the export of heat and moisture to higher latitudes, and is highly sensitive to climate change, for instance due to changes in the position of the Intertropical Convergence Zone (ITCZ). Previous work on Caribbean stalagmites suggests a strong connection of precipitation variability to North Atlantic (NA) sea surface temperatures on multidecadal to millenial timescales (Fensterer et al., 2012; Fensterer et al., 2013; Winter et al., 2011). Cold phases in the NA potentially lead to a southward shift of the ITCZ and thus drier conditions in Cuba. On orbital timescales, Cuban stalagmites suggest a relation of speleothem δ18O values with the δ18O value of Caribbean surface waters (Fensterer et al., 2013). Here we present an expansion of the Cuban speleothem record covering the whole last glacial period from the end of MIS5c (97 ka BP) until 7 ka with hiatuses between 93-80 ka, 37-35 ka and 13-10 ka. Stalagmite Cuba medio (CM) has been precisely dated with 60 230Th/U-ages, mainly performed by the MC-ICPMS technique. The δ18O and δ13C records are completed by a continuous, high resolution LA-ICPMS trace element profile. These data allow for the first time to establish a multi-proxy climate reconstruction for the North Western Caribbean at decadal to centennial resolution for this period. The long-term variability of the δ18O values probably reflects rainfall amount in Cuba. The response to some Dansgaard/Oeschger and Heinrich stadials confirms the previously observed correlation between Caribbean and NA climate variability. However, this connection is not clearly imprinted throughout the record. Furthermore, trace elements, such as Mg, do not proof without ambiguity drier conditions in Cuba during NA cold events, such as the Heinrich stadials. This suggests that climate variability in Cuba was more complex during the last 100ka, and that the NA was not the only driving factor. Due to the competing influence of the NA, the Gulf of Mexico and the Pacific Ocean, the proposed severe changes in the tropical hydrological cycle during that time (such as variations of the ITCZ, insolation and the thermohaline circulation (THC)) have potentially lead to significant changes in sources and trajectories of precipitation in Western Cuba. Our record, thus, provides an important contribution towards understanding and differentiating these parameters on Caribbean climate during glacial climate changes. References: Fensterer, C., Scholz, D., Hoffmann, D., Spötl, C., Pajón, J.M., Mangini, A., 2012. Cuban stalagmite suggests relationship between Caribbean precipitation and the Atlantic Multidecadal Oscillation during the past 1.3 ka. The Holocene, 0959683612449759. Fensterer, C., Scholz, D., Hoffmann, D.L., Spötl, C., Schröder-Ritzrau, A., Horn, C., Pajón, J.M., Mangini, A., 2013. Millennial-scale climate variability during the last 12.5 ka recorded in a Caribbean speleothem. Earth and Planetary Science Letters 361, 143-151. Winter, A., Miller, T., Kushnir, Y., Sinha, A., Timmermann, A., Jury, M.R., Gallup, C., Cheng, H., Edwards, R.L., 2011. Evidence for 800years of North Atlantic multi-decadal variability from a Puerto Rican speleothem. Earth and Planetary Science Letters 308, 23-28.

Observed decreases in the Canadian outdoor skating season due to recent winter warming

NASA Astrophysics Data System (ADS)

Damyanov, Nikolay N.; Damon Matthews, H.; Mysak, Lawrence A.

2012-03-01

Global warming has the potential to negatively affect one of Canada’s primary sources of winter recreation: hockey and ice skating on outdoor rinks. Observed changes in winter temperatures in Canada suggest changes in the meteorological conditions required to support the creation and maintenance of outdoor skating rinks; while there have been observed increases in the ice-free period of several natural water bodies, there has been no study of potential trends in the duration of the season supporting the construction of outdoor skating rinks. Here we show that the outdoor skating season (OSS) in Canada has significantly shortened in many regions of the country as a result of changing climate conditions. We first established a meteorological criterion for the beginning, and a proxy for the length of the OSS. We extracted this information from daily maximum temperature observations from 1951 to 2005, and tested it for significant changes over time due to global warming as well as due to changes in patterns of large-scale natural climate variability. We found that many locations have seen a statistically significant decrease in the OSS length, particularly in Southwest and Central Canada. This suggests that future global warming has the potential to significantly compromise the viability of outdoor skating in Canada.

Linking the pacific decadal oscillation to seasonal stream discharge patterns in Southeast Alaska

USGS Publications Warehouse

Neal, E.G.; Todd, Walter M.; Coffeen, C.

2002-01-01

This study identified and examined differences in Southeast Alaskan streamflow patterns between the two most recent modes of the Pacific decadal oscillation (PDO). Identifying relationships between the PDO and specific regional phenomena is important for understanding climate variability, interpreting historical hydrological variability, and improving water-resources forecasting. Stream discharge data from six watersheds in Southeast Alaska were divided into cold-PDO (1947-1976) and warm-PDO (1977-1998) subsets. For all watersheds, the average annual streamflows during cold-PDO years were not significantly different from warm-PDO years. Monthly and seasonal discharges, however, did differ significantly between the two subsets, with the warm-PDO winter flows being typically higher than the cold-PDO winter flows and the warm-PDO summer flows being typically lower than the cold-PDO flows. These results were consistent with and driven by observed temperature and snowfall patterns for the region. During warm-PDO winters, precipitation fell as rain and ran-off immediately, causing higher than normal winter streamflow. During cold-PDO winters, precipitation was stored as snow and ran off during the summer snowmelt, creating greater summer streamflows. The Mendenhall River was unique in that it experienced higher flows for all seasons during the warm-PDO relative to the cold-PDO. The large amount of Mendenhall River discharge caused by glacial melt during warm-PDO summers offset any flow reduction caused by lack of snow accumulation during warm-PDO winters. The effect of the PDO on Southeast Alaskan watersheds differs from other regions of the Pacific Coast of North America in that monthly/seasonal discharge patterns changed dramatically with the switch in PDO modes but annual discharge did not. ?? 2002 Elsevier Science B.V. All rights reserved.

Relative Contributions of Mean-State Shifts and ENSO-Driven Variability to Precipitation Changes in a Warming Climate

NASA Technical Reports Server (NTRS)

Bonfils, Celine J. W.; Santer, Benjamin D.; Phillips, Thomas J.; Marvel, Kate; Leung, L. Ruby; Doutriaux, Charles; Capotondi, Antonietta

2015-01-01

El Niño-Southern Oscillation (ENSO) is an important driver of regional hydroclimate variability through far-reaching teleconnections. This study uses simulations performed with coupled general circulation models (CGCMs) to investigate how regional precipitation in the twenty-first century may be affected by changes in both ENSO-driven precipitation variability and slowly evolving mean rainfall. First, a dominant, time-invariant pattern of canonical ENSO variability (cENSO) is identified in observed SST data. Next, the fidelity with which 33 state-of-the-art CGCMs represent the spatial structure and temporal variability of this pattern (as well as its associated precipitation responses) is evaluated in simulations of twentieth-century climate change. Possible changes in both the temporal variability of this pattern and its associated precipitation teleconnections are investigated in twenty-first-century climate projections. Models with better representation of the observed structure of the cENSO pattern produce winter rainfall teleconnection patterns that are in better accord with twentieth-century observations and more stationary during the twenty-first century. Finally, the model-predicted twenty-first-century rainfall response to cENSO is decomposed into the sum of three terms: 1) the twenty-first-century change in the mean state of precipitation, 2) the historical precipitation response to the cENSO pattern, and 3) a future enhancement in the rainfall response to cENSO, which amplifies rainfall extremes. By examining the three terms jointly, this conceptual framework allows the identification of regions likely to experience future rainfall anomalies that are without precedent in the current climate.

Relative Contributions of Mean-State Shifts and ENSO-Driven Variability to Precipitation Changes in a Warming Climate

NASA Technical Reports Server (NTRS)

Bonfils, Celine J. W.; Santer, Benjamin D.; Phillips, Thomas J.; Marvel, Kate; Leung, L. Ruby; Doutriaux, Charles; Capotondi, Antonietta

2015-01-01

The El Nino-Southern Oscillation (ENSO) is an important driver of regional hydroclimate variability through far-reaching teleconnections. This study uses simulations performed with Coupled General Circulation Models (CGCMs) to investigate how regional precipitation in the 21st century may be affected by changes in both ENSO-driven precipitation variability and slowly-evolving mean rainfall. First, a dominant, time-invariant pattern of canonical ENSO variability (cENSO) is identified in observed SST data. Next, the fidelity with which 33 state-of-the-art CGCMs represent the spatial structure and temporal variability of this pattern (as well as its associated precipitation responses) is evaluated in simulations of 20th century climate change. Possible changes in both the temporal variability of this pattern and its associated precipitation teleconnections are investigated in 21st century climate projections. Models with better representation of the observed structure of the cENSO pattern produce winter rainfall teleconnection patterns that are in better accord with 20th century observations and more stationary during the 21st century. Finally, the model-predicted 21st century rainfall response to cENSO is decomposed into the sum of three terms: 1) the 21st century change in the mean state of precipitation; 2) the historical precipitation response to the cENSO pattern; and 3) a future enhancement in the rainfall response to cENSO, which amplifies rainfall extremes. By examining the three terms jointly, this conceptual framework allows the identification of regions likely to experience future rainfall anomalies that are without precedent in the current climate.

On the Influence of North Pacific Sea Surface Temperature on the Arctic Winter Climate

NASA Technical Reports Server (NTRS)

Hurwitz, Margaret M.; Newman, P. A.; Garfinkel, C. I.

2012-01-01

Differences between two ensembles of Goddard Earth Observing System Chemistry-Climate Model simulations isolate the impact of North Pacific sea surface temperatures (SSTs) on the Arctic winter climate. One ensemble of extended winter season forecasts is forced by unusually high SSTs in the North Pacific, while in the second ensemble SSTs in the North Pacific are unusually low. High Low differences are consistent with a weakened Western Pacific atmospheric teleconnection pattern, and in particular, a weakening of the Aleutian low. This relative change in tropospheric circulation inhibits planetary wave propagation into the stratosphere, in turn reducing polar stratospheric temperature in mid- and late winter. The number of winters with sudden stratospheric warmings is approximately tripled in the Low ensemble as compared with the High ensemble. Enhanced North Pacific SSTs, and thus a more stable and persistent Arctic vortex, lead to a relative decrease in lower stratospheric ozone in late winter, affecting the April clear-sky UV index at Northern Hemisphere mid-latitudes.

Generalized Dissimilarity Modeling of Late-Quaternary Variations in Pollen-Based Compositional Dissimilarity

NASA Astrophysics Data System (ADS)

Williams, J. W.; Blois, J.; Ferrier, S.; Manion, G.; Fitzpatrick, M.; Veloz, S.; He, F.; Liu, Z.; Otto-Bliesner, B. L.

2011-12-01

In Quaternary paleoecology and paleoclimatology, compositionally dissimilar fossil assemblages usually indicate dissimilar environments; this relationship underpins assemblage-level techniques for paleoenvironmental reconstruction such as mutual climatic ranges or the modern analog technique. However, there has been relatively little investigation into the form of the relationship between compositional dissimilarity and climatic dissimilarity. Here we apply generalized dissimilarity modeling (GDM; Ferrier et al. 2007) as a tool for modeling the expected non-linear relationships between compositional and climatic dissimilarity. We use the CCSM3.0 transient paleoclimatic simulations from the SynTrace working group (Liu et al. 2009) and a new generation of fossil pollen maps from eastern North America (Blois et al. 2011) to 1) assess the spatial relationships between compositional dissimilarity and climatic dissimilarity and 2) whether these spatial relationships change over time. We used a taxonomic list of 106 genus-level pollen types, six climatic variables (winter precipitation and mean temperature, summer precipitation and temperature, seasonality of precipitation, and seasonality of temperature) that were chosen to minimize collinearity, and a cross-referenced pollen and climate dataset mapped for time slices spaced 1000 years apart. When GDM was trained for one time slice, the correlation between predicted and observed spatial patterns of community dissimilarity for other times ranged between 0.3 and 0.73. The selection of climatic predictor variables changed over time, as did the form of the relationship between compositional turnover and climatic predictors. Summer temperature was the only variable selected for all time periods. These results thus suggest that the relationship between compositional dissimilarity in pollen assemblages (and, by implication, beta diversity in plant communities) and climatic dissimilarity can change over time, for reasons to be further studied.

Optimal Sampling to Provide User-Specific Climate Information.

NASA Astrophysics Data System (ADS)

Panturat, Suwanna

The types of weather-related world problems which are of socio-economic importance selected in this study as representative of three different levels of user groups include: (i) a regional problem concerned with air pollution plumes which lead to acid rain in the north eastern United States, (ii) a state-level problem in the form of winter wheat production in Oklahoma, and (iii) an individual-level problem involving reservoir management given errors in rainfall estimation at Lake Ellsworth, upstream from Lawton, Oklahoma. The study is aimed at designing optimal sampling networks which are based on customer value systems and also abstracting from data sets that information which is most cost-effective in reducing the climate-sensitive aspects of a given user problem. Three process models being used in this study to interpret climate variability in terms of the variables of importance to the user comprise: (i) the HEFFTER-SAMSON diffusion model as the climate transfer function for acid rain, (ii) the CERES-MAIZE plant process model for winter wheat production and (iii) the AGEHYD streamflow model selected as "a black box" for reservoir management. A state-of-the-art Non Linear Program (NLP) algorithm for minimizing an objective function is employed to determine the optimal number and location of various sensors. Statistical quantities considered in determining sensor locations including Bayes Risk, the chi-squared value, the probability of the Type I error (alpha) and the probability of the Type II error (beta) and the noncentrality parameter delta^2. Moreover, the number of years required to detect a climate change resulting in a given bushel per acre change in mean wheat production is determined; the number of seasons of observations required to reduce the standard deviation of the error variance of the ambient sulfur dioxide to less than a certain percent of the mean is found; and finally the policy of maintaining pre-storm flood pools at selected levels is examined given information from the optimal sampling network as defined by the study.

Multi-scale enhancement of climate prediction over land by improving the model sensitivity to vegetation variability

NASA Astrophysics Data System (ADS)

Alessandri, A.; Catalano, F.; De Felice, M.; Hurk, B. V. D.; Doblas-Reyes, F. J.; Boussetta, S.; Balsamo, G.; Miller, P. A.

2017-12-01

Here we demonstrate, for the first time, that the implementation of a realistic representation of vegetation in Earth System Models (ESMs) can significantly improve climate simulation and prediction across multiple time-scales. The effective sub-grid vegetation fractional coverage vary seasonally and at interannual time-scales in response to leaf-canopy growth, phenology and senescence. Therefore it affects biophysical parameters such as the surface resistance to evapotranspiration, albedo, roughness lenght, and soil field capacity. To adequately represent this effect in the EC-Earth ESM, we included an exponential dependence of the vegetation cover on the Leaf Area Index.By comparing two sets of simulations performed with and without the new variable fractional-coverage parameterization, spanning from centennial (20th Century) simulations and retrospective predictions to the decadal (5-years), seasonal (2-4 months) and weather (4 days) time-scales, we show for the first time a significant multi-scale enhancement of vegetation impacts in climate simulation and prediction over land. Particularly large effects at multiple time scales are shown over boreal winter middle-to-high latitudes over Canada, West US, Eastern Europe, Russia and eastern Siberia due to the implemented time-varying shadowing effect by tree-vegetation on snow surfaces. Over Northern Hemisphere boreal forest regions the improved representation of vegetation-cover consistently correct the winter warm biases, improves the climate change sensitivity, the decadal potential predictability as well as the skill of forecasts at seasonal and weather time-scales. Significant improvements of the prediction of 2m temperature and rainfall are also shown over transitional land surface hot spots. Both the potential predictability at decadal time-scale and seasonal-forecasts skill are enhanced over Sahel, North American Great Plains, Nordeste Brazil and South East Asia, mainly related to improved performance in the surface evapotranspiration.Above results are discussed in a peer-review paper just being accepted for publication on Climate Dynamics (Alessandri et al., 2017; doi:10.1007/s00382-017-3766-y).

Effects of climate change on water abstraction restrictions for irrigation during droughts - The UK case

NASA Astrophysics Data System (ADS)

Rey Vicario, D.; Holman, I.

2016-12-01

The use of water for irrigation and on-farm reservoir filling is globally important for agricultural production. In humid climates, like the UK, supplemental irrigation can be critical to buffer the effects of rainfall variability and to achieve high quality crops. Given regulatory efforts to secure sufficient environmental river flows and meet rising water demands due to population growth and climate change, increasing water scarcity is likely to compound the drought challenges faced by irrigated agriculture in this region. Currently, water abstraction from surface waters for agricultural irrigation can be restricted by the Environment Agency during droughts under Section 57 of the Water Resources Act (1991), based on abnormally low river flow levels and rainfall forecast, causing significant economic impacts on irrigated agricultural production. The aim of this study is to assess the impact that climate change may have on agricultural abstraction in the UK within the context of the abstraction restriction triggers currently in place. These triggers have been applied to the `Future Flows hydrology' database to assess the likelihood of increasing restrictions on agricultural abstraction in the future by comparing the probability of voluntary and compulsory restrictions in the baseline (1961-1990) and future period (2071-2098) for 282 catchments throughout the whole of the UK. The results of this study show a general increase in the probability of future agricultural irrigation abstraction restrictions in the UK in the summer, particularly in the South West, although there is significant variability between the 11 ensemble members. The results also indicate that UK winters are likely to become wetter in the future, although in some catchments the probability of abstraction restriction in the reservoir refilling winter months (November-February) could increase slightly. An increasing frequency of drought events due to climate change is therefore likely to lead to more water abstraction restrictions, increasing the need for irrigators to adapt their businesses to increase drought resilience and hence food security.

The Costs of Climate Change: Impact of Future Snow Cover Projections on Valuation of Albedo in Forest Management

NASA Astrophysics Data System (ADS)

Burakowski, E. A.; Lutz, D. A.

2014-12-01

Surface albedo provides an important climate regulating ecosystem service, particularly in the mid-latitudes where seasonal snow cover influences surface radiation budgets. In the case of substantial seasonal snow cover, the influence of albedo can equal or surpass the climatic benefits of carbon sequestration from forest growth. Climate mitigation platforms should therefore consider albedo in their framework in order to integrate these two climatic services in an economic context for the effective design and implementation of forest management projects. Over the next century, the influence of surface albedo is projected to diminish under higher emissions scenarios due to an overall decrease in snow depth and duration of snow cover in the mid-latitudes. In this study, we focus on the change in economic value of winter albedo in the northeastern United States projected through 2100 using the Special Report on Emissions Scenarios (SRES) a1 and b1 scenarios. Statistically downscaled temperature and precipitation are used as input to the Variable Infiltration Capacity (VIC) model to provide future daily snow depth fields through 2100. Using VIC projections of future snow depth, projected winter albedo fields over deforested lands were generated using an empirical logarithmic relationship between snow depth and albedo derived from a volunteer network of snow observers in New Hampshire over the period Nov 2011 through 2014. Our results show that greater reductions in snow depth and the number of winter days with snow cover in the a1 compared to the b1 scenario reduce wintertime albedo when forested lands are harvested. This result has implications on future trade-offs among albedo, carbon storage, and timber value that should be investigated in greater detail. The impacts of forest harvest on radiative forcing associated with energy redistribution (e.g., latent heat and surface roughness length) should also be considered in future work.

Evidence for range contraction of snowshoe hare in Pennsylvania

USGS Publications Warehouse

Diefenbach, Duane R.; Rathbun, Stephen L.; Vreeland, J.K.; Grove, Deborah; Kanapaux, William J.

2016-01-01

In Pennsylvania, Lepus americanus (Snowshoe Hare) is near the southern limits of its range and at risk of range contraction because of loss of early-successional forest and impacts of climate change. We used hunter-harvest data to investigate changes in the distribution of Snowshoe Hare in Pennsylvania (1983–2011), forest inventory and land-use data to assess changes in amount and distribution of early-successional forest (1988–2011), and occupancy modeling (2004) to identify habitat and climate variables that explain the current distribution of Snowshoe Hare. We determined presence of Snowshoe Hare based on visual sightings, observations of tracks, and DNA analysis of fecal pellets, and used repeated visits to sampling sites and occupancy models to estimate occupancy rates (Ψ). Hunter-harvest data indicated the range of Snowshoe Hare in Pennsylvania contracted towards northwestern and northeastern portions of the state. Based on occupancy modeling, Snowshoe Hare were most likely to occupy early-successional and mixed deciduous-coniferous forest types and areas with colder winter temperatures, which coincided with the distribution of hunter harvests. Among the 4 forest types, we estimated Ψ = 0.52-0.79 and Ψ = 0.10-0.32 where winter temperatures were coldest and warmest, respectively. Total forest loss was <1% during 1988-2011, and the loss of early-successional forest in the current and former range of Snowshoe Hares was similar as were mean patch size and a fragmentation metric of early-successional habitat. Thus, changes in forest characteristics did not explain the range contraction we observed. We used climate-model predictions and our occupancy model to predict that average occupancy probability across northern Pennsylvania may decline from 0.27 in 2004 to 0.10–0.18 by 2050–2059, depending on the climate model. The range of Snowshoe Hare in Pennsylvania has contracted to regions of Pennsylvania with the coldest winter temperatures and most persistent snowpack, and based on projected climate change, our results suggest further range contraction of Snowshoe Hare in Pennsylvania.

Environmental Predictors of Seasonal Influenza Epidemics across Temperate and Tropical Climates

PubMed Central

Tamerius, James D.; Shaman, Jeffrey; Alonso, Wladmir J.; Bloom-Feshbach, Kimberly; Uejio, Christopher K.; Comrie, Andrew; Viboud, Cécile

2013-01-01

Human influenza infections exhibit a strong seasonal cycle in temperate regions. Recent laboratory and epidemiological evidence suggests that low specific humidity conditions facilitate the airborne survival and transmission of the influenza virus in temperate regions, resulting in annual winter epidemics. However, this relationship is unlikely to account for the epidemiology of influenza in tropical and subtropical regions where epidemics often occur during the rainy season or transmit year-round without a well-defined season. We assessed the role of specific humidity and other local climatic variables on influenza virus seasonality by modeling epidemiological and climatic information from 78 study sites sampled globally. We substantiated that there are two types of environmental conditions associated with seasonal influenza epidemics: “cold-dry” and “humid-rainy”. For sites where monthly average specific humidity or temperature decreases below thresholds of approximately 11–12 g/kg and 18–21°C during the year, influenza activity peaks during the cold-dry season (i.e., winter) when specific humidity and temperature are at minimal levels. For sites where specific humidity and temperature do not decrease below these thresholds, seasonal influenza activity is more likely to peak in months when average precipitation totals are maximal and greater than 150 mm per month. These findings provide a simple climate-based model rooted in empirical data that accounts for the diversity of seasonal influenza patterns observed across temperate, subtropical and tropical climates. PMID:23505366

Spatial analysis of future East Asian seasonal temperature using two regional climate model simulations

NASA Astrophysics Data System (ADS)

Kim, Yura; Jun, Mikyoung; Min, Seung-Ki; Suh, Myoung-Seok; Kang, Hyun-Suk

2016-05-01

CORDEX-East Asia, a branch of the coordinated regional climate downscaling experiment (CORDEX) initiative, provides high-resolution climate simulations for the domain covering East Asia. This study analyzes temperature data from regional climate models (RCMs) participating in the CORDEX - East Asia region, accounting for the spatial dependence structure of the data. In particular, we assess similarities and dissimilarities of the outputs from two RCMs, HadGEM3-RA and RegCM4, over the region and over time. A Bayesian functional analysis of variance (ANOVA) approach is used to simultaneously model the temperature patterns from the two RCMs for the current and future climate. We exploit nonstationary spatial models to handle the spatial dependence structure of the temperature variable, which depends heavily on latitude and altitude. For a seasonal comparison, we examine changes in the winter temperature in addition to the summer temperature data. We find that the temperature increase projected by RegCM4 tends to be smaller than the projection of HadGEM3-RA for summers, and that the future warming projected by HadGEM3-RA tends to be weaker for winters. Also, the results show that there will be a warming of 1-3°C over the region in 45 years. More specifically, the warming pattern clearly depends on the latitude, with greater temperature increases in higher latitude areas, which implies that warming may be more severe in the northern part of the domain.

Climatic Change and the Classroom: A Teaching Aid to Understanding.

ERIC Educational Resources Information Center

Sanders, C. Gerald

Equable climates with mild winters and summers are more likely to maintain snow or ice cover in high latitudes than extreme climates having colder winters and hotter summers. A simplified version of the Milankovitch cycles can be used to develop a model instructors can use in their classes to illustrate the orbital variations producing either…

An evaluation of the variable-resolution CESM for modeling California's climate: Evaluation of VR-CESM for Modeling California's Climate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Xingying; Rhoades, Alan M.; Ullrich, Paul A.

In this paper, the recently developed variable-resolution option within the Community Earth System Model (VR-CESM) is assessed for long-term regional climate modeling of California at 0.25° (~ 28 km) and 0.125° (~ 14 km) horizontal resolutions. The mean climatology of near-surface temperature and precipitation is analyzed and contrasted with reanalysis, gridded observational data sets, and a traditional regional climate model (RCM)—the Weather Research and Forecasting (WRF) model. Statistical metrics for model evaluation and tests for differential significance have been extensively applied. VR-CESM tended to produce a warmer summer (by about 1–3°C) and overestimated overall winter precipitation (about 25%–35%) compared tomore » reference data sets when sea surface temperatures were prescribed. Increasing resolution from 0.25° to 0.125° did not produce a statistically significant improvement in the model results. By comparison, the analogous WRF climatology (constrained laterally and at the sea surface by ERA-Interim reanalysis) was ~1–3°C colder than the reference data sets, underestimated precipitation by ~20%–30% at 27 km resolution, and overestimated precipitation by ~ 65–85% at 9 km. Overall, VR-CESM produced comparable statistical biases to WRF in key climatological quantities. Moreover, this assessment highlights the value of variable-resolution global climate models (VRGCMs) in capturing fine-scale atmospheric processes, projecting future regional climate, and addressing the computational expense of uniform-resolution global climate models.« less

An evaluation of the variable-resolution CESM for modeling California's climate: Evaluation of VR-CESM for Modeling California's Climate

DOE PAGES

Huang, Xingying; Rhoades, Alan M.; Ullrich, Paul A.; ...

2016-03-01

In this paper, the recently developed variable-resolution option within the Community Earth System Model (VR-CESM) is assessed for long-term regional climate modeling of California at 0.25° (~ 28 km) and 0.125° (~ 14 km) horizontal resolutions. The mean climatology of near-surface temperature and precipitation is analyzed and contrasted with reanalysis, gridded observational data sets, and a traditional regional climate model (RCM)—the Weather Research and Forecasting (WRF) model. Statistical metrics for model evaluation and tests for differential significance have been extensively applied. VR-CESM tended to produce a warmer summer (by about 1–3°C) and overestimated overall winter precipitation (about 25%–35%) compared tomore » reference data sets when sea surface temperatures were prescribed. Increasing resolution from 0.25° to 0.125° did not produce a statistically significant improvement in the model results. By comparison, the analogous WRF climatology (constrained laterally and at the sea surface by ERA-Interim reanalysis) was ~1–3°C colder than the reference data sets, underestimated precipitation by ~20%–30% at 27 km resolution, and overestimated precipitation by ~ 65–85% at 9 km. Overall, VR-CESM produced comparable statistical biases to WRF in key climatological quantities. Moreover, this assessment highlights the value of variable-resolution global climate models (VRGCMs) in capturing fine-scale atmospheric processes, projecting future regional climate, and addressing the computational expense of uniform-resolution global climate models.« less

A new collective view of oceanography of the Arctic and North Atlantic basins

NASA Astrophysics Data System (ADS)

Yashayaev, Igor; Seidov, Dan; Demirov, Entcho

2015-03-01

We review some historical aspects of the major observational programs in the North Atlantic and adjacent regions that contributed to establishing and maintaining the global ocean climate monitoring network. The paper also presents the oceanic perspectives of climate change and touches the important issues of ocean climate variability on time scales from years to decades. Some elements of the improved understanding of the causes and mechanisms of variability in the subpolar North Atlantic and adjacent seas are discussed in detail. The sophistication of current oceanographic analysis, especially in connection with the most recent technological breakthroughs - notably the launch of the global array of profiling Argo floats - allows us to approach new challenges in ocean research. We demonstrate how the ocean-climate changes in the subpolar basins and polar seas correlate with variations in the major climate indices such as the North Atlantic Oscillation and Atlantic Multidecadal Oscillation, and discuss possible connections between the unprecedented changes in the Arctic and Greenland ice-melt rates observed over the past decade and variability of hydrographic conditions in the Labrador Sea. Furthermore, a synthesis of shipboard and Argo measurements in the Labrador Sea reveals the effects of the regional climate trends such as freshening of the upper layer - possible causes of which are also discussed - on the winter convection in the Labrador Sea including its strength, duration and spatial extent. These changes could have a profound impact on the regional and planetary climates. A section with the highlights of all papers comprising the Special Issue concludes the Preface.

Increased aridity at the end of the Eemian in the Levant and relationships to global climate

NASA Astrophysics Data System (ADS)

Kiro, Y.; Goldstein, S. L.; Kushnir, Y.; Lazar, B.; Stein, M.

2016-12-01

Thick layers of halite deposited in the Dead Sea at the end of MIS 5e, revealed by the ICDP Dead Sea Deep Drilling Project cores, indicate extremely arid conditions prevailing in the Levant . Average precipitation during this interval was 50% of the present, and there were strong fluctuations between wetter periods similar to the present-day lasting on the order of millennia, and drought periods with precipitation as low as 20% of the present-day lasting on the order of centuries. At the same time, there were infrequent but intense rainfall events in the southern Levant and flash floods. U-series ages indicate that the hyper-arid conditions prevailed between 120-110 ka, following the `Eemian' Northern Hemisphere insolation peak interval of MIS 5e, and coinciding with decreased high latitude temperatures and atmospheric CO2 (Jouzel et al. 2007, Bereiter et al. 2015). Such conditions are consistent with pollen records from southern Europe indicating that region was warm until 110 ka (Brauer et al., 2007). The hyper-arid interval in the Levant followed a relatively wet period during the Eemian, coinciding with an intense African monsoon and major sapropel deposition in the eastern Mediterranean. Climate models indicate increasing aridity in the Levant between 125 ka and 120 ka; while at 125 ka there was significant summer and winter precipitation, 120 ka was drier than the present. The Levant in the present-day has a Mediterranean climate with dry summers and wet winters, where warmer winters coincide with lower precipitation. While the time interval of 120 ka to 110 ka, following the Eemian, was characterized by decreasing summer insolation, winter insolation increased. This increase in winter insolation may have caused a decrease in the sea-land temperature gradient that resulted in decreased precipitation on land. Bereiter, B. et al., 2015, Antarctic Ice Cores Revised 800KYr CO2 Data Brauer, A et al., 2007, Evidence for last interglacial chronology and environmental change from Southern Europe.: Proceedings of the National Academy of Sciences of the United States of America, v. 104, no. 2, p. 450-455 Jouzel, J. et al., 2007, Orbital and millennial Antarctic climate variability over the past 800,000 years.: Science (New York, N.Y.), v. 317, no. 5839, p. 793-6

Variability and trends in surface seawater pCO2 and CO2 flux in the Pacific Ocean

NASA Astrophysics Data System (ADS)

Sutton, A. J.; Wanninkhof, R.; Sabine, C. L.; Feely, R. A.; Cronin, M. F.; Weller, R. A.

2017-06-01

Variability and change in the ocean sink of anthropogenic carbon dioxide (CO2) have implications for future climate and ocean acidification. Measurements of surface seawater CO2 partial pressure (pCO2) and wind speed from moored platforms are used to calculate high-resolution CO2 flux time series. Here we use the moored CO2 fluxes to examine variability and its drivers over a range of time scales at four locations in the Pacific Ocean. There are significant surface seawater pCO2, salinity, and wind speed trends in the North Pacific subtropical gyre, especially during winter and spring, which reduce CO2 uptake over the 10 year record of this study. Starting in late 2013, elevated seawater pCO2 values driven by warm anomalies cause this region to be a net annual CO2 source for the first time in the observational record, demonstrating how climate forcing can influence the timing of an ocean region shift from CO2 sink to source.

Paleoclimate reconstruction along the Pole-Equator-Pole transect of the Americas (PEP 1)

USGS Publications Warehouse

Markgraf, Vera; Baumgartner, T.R.; Bradbury, J.P.; Diaz, Henry F.; Dunbar, R.B.; Luckman, B.H.; Seltzer, G.O.; Swetnam, T.W.; Villalba, R.

2000-01-01

Examples are presented of inter-hemispheric comparison of instrumental climate and paleoclimate proxy records from the Americas for different temporal scales. Despite a certain symmetry of seasonal precipitation patterns along the PEP I transect, decadal variability of winter precipitation shows different characteristics in terms of amplitude and frequency in both the last 100 and last 1000 years. Such differences in variability are also seen in a comparison of time series of different El Nino/Southern Oscillation proxy records from North and South America, however, these differences do not appear to affect the spatial correlation with Pacific sea surface temperature patterns. Local and regional differences in response to climate change are even more pronounced for records with lower temporal resolution, and inter-hemispheric synchroneity may or may not be indicative of the same forcing. This aspect is illustrated in an inter-hemispheric comparison of the last 1000 years of glacier variability, and of the full- and lateglacial lake level history.

Fossils tell of mild winters in an ancient hothouse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kerr, R.A.

Fossil evidence from the Eocene points to a warmer winter climate in the continental interior (e.g. North Dakota) than that predicted by computer models. Paleobotanists have been able to quantify approximate winter mean temperatures by using leaf characteristics. As one example, leaves from colder climates have toothed edges. Leaf structure was correlated with modern climate regimes, and these relations were then applied to Eocene fossils. They found cold-month mean temperatures of 1-8[degrees]C in Wyoming and Montana, well above model predictions. Climate models can be manipulated to reproduce these temperatures, but not without overheating the entire globe. The problem could bemore » that the Eocene atmospheric circulation was different from today, something not accounted for well by climate models.« less

The hard winter of 1880-1881: Climatological context and communication via a Laura Ingalls Wilder narrative

NASA Astrophysics Data System (ADS)

Boustead, Barbara E.

The Hard Winter of 1880-1881 was featured in the Laura Ingalls Wilder historical fiction account, The Long Winter, as well as in several town histories across the region. Both meteorological records and historical accounts indicate that the winter was particularly long, snowy, and cold. The question of how "hard" a winter is for a given location depends on the climatological context, which relies on an objective characterization of winter severity. The Accumulated Winter Season Severity Index (AWSSI) allows comparison of the winter of 1880-1881 among sites across the region, as well as in the context of the period of record, to quantify its severity. Additionally, investigating the impacts of both the El Nino/Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO) in the central United States provides context for the influence of both a strongly negative NAO and an El Nino event during the winter of 1880-1881. With an understanding of the climatological factors influencing the Hard Winter, along with the context for its severity, a more thorough analysis then was conducted to quantify and describe its severity. The connection of the winter of 1880-1881 to a popular book written by an author who is a cultural icon provides a natural vehicle with which to communicate weather and climate concepts to multiple non-technical audiences. The communication of complex weather and climate concepts is a well-documented challenge. One method to bridge between science concepts and public understanding is to relate those concepts to familiar subjects and stories, including Laura Ingalls Wilder's books. A narrative constructed around the books, particularly The Long Winter, provides a means of audience engagement and interest in weather- and climate-related topics, which was at least partially quantified by surveying audiences of the narrative. Overall, the scientific background, combined with a familiar narrative voice, provides a means to transmit weather and climate.

Regional climate model simulations indicate limited climatic impacts by operational and planned European wind farms.

PubMed

Vautard, Robert; Thais, Françoise; Tobin, Isabelle; Bréon, François-Marie; Devezeaux de Lavergne, Jean-Guy; Colette, Augustin; Yiou, Pascal; Ruti, Paolo Michele

2014-01-01

The rapid development of wind energy has raised concerns about environmental impacts. Temperature changes are found in the vicinity of wind farms and previous simulations have suggested that large-scale wind farms could alter regional climate. However, assessments of the effects of realistic wind power development scenarios at the scale of a continent are missing. Here we simulate the impacts of current and near-future wind energy production according to European Union energy and climate policies. We use a regional climate model describing the interactions between turbines and the atmosphere, and find limited impacts. A statistically significant signal is only found in winter, with changes within ±0.3 °C and within 0-5% for precipitation. It results from the combination of local wind farm effects and changes due to a weak, but robust, anticyclonic-induced circulation over Europe. However, the impacts remain much weaker than the natural climate interannual variability and changes expected from greenhouse gas emissions.

Sensitivity of the Eocene climate to CO2 and orbital variability

NASA Astrophysics Data System (ADS)

Keery, John S.; Holden, Philip B.; Edwards, Neil R.

2018-02-01

The early Eocene, from about 56 Ma, with high atmospheric CO2 levels, offers an analogue for the response of the Earth's climate system to anthropogenic fossil fuel burning. In this study, we present an ensemble of 50 Earth system model runs with an early Eocene palaeogeography and variation in the forcing values of atmospheric CO2 and the Earth's orbital parameters. Relationships between simple summary metrics of model outputs and the forcing parameters are identified by linear modelling, providing estimates of the relative magnitudes of the effects of atmospheric CO2 and each of the orbital parameters on important climatic features, including tropical-polar temperature difference, ocean-land temperature contrast, Asian, African and South (S.) American monsoon rains, and climate sensitivity. Our results indicate that although CO2 exerts a dominant control on most of the climatic features examined in this study, the orbital parameters also strongly influence important components of the ocean-atmosphere system in a greenhouse Earth. In our ensemble, atmospheric CO2 spans the range 280-3000 ppm, and this variation accounts for over 90 % of the effects on mean air temperature, southern winter high-latitude ocean-land temperature contrast and northern winter tropical-polar temperature difference. However, the variation of precession accounts for over 80 % of the influence of the forcing parameters on the Asian and African monsoon rainfall, and obliquity variation accounts for over 65 % of the effects on winter ocean-land temperature contrast in high northern latitudes and northern summer tropical-polar temperature difference. Our results indicate a bimodal climate sensitivity, with values of 4.36 and 2.54 °C, dependent on low or high states of atmospheric CO2 concentration, respectively, with a threshold at approximately 1000 ppm in this model, and due to a saturated vegetation-albedo feedback. Our method gives a quantitative ranking of the influence of each of the forcing parameters on key climatic model outputs, with additional spatial information from singular value decomposition providing insights into likely physical mechanisms. The results demonstrate the importance of orbital variation as an agent of change in climates of the past, and we demonstrate that emulators derived from our modelling output can be used as rapid and efficient surrogates of the full complexity model to provide estimates of climate conditions from any set of forcing parameters.

The role of the winter residual circulation in the summer mesopause regions in WACCM

NASA Astrophysics Data System (ADS)

Sanne Kuilman, Maartje; Karlsson, Bodil

2018-03-01

High winter planetary wave activity warms the summer polar mesopause via a link between the two hemispheres. Complex wave-mean-flow interactions take place on a global scale, involving sharpening and weakening of the summer zonal flow. Changes in the wind shear occasionally generate flow instabilities. Additionally, an altering zonal wind modifies the breaking of vertically propagating gravity waves. A crucial component for changes in the summer zonal flow is the equatorial temperature, as it modifies latitudinal gradients. Since several mechanisms drive variability in the summer zonal flow, it can be hard to distinguish which one is dominant. In the mechanism coined interhemispheric coupling, the mesospheric zonal flow is suggested to be a key player for how the summer polar mesosphere responds to planetary wave activity in the winter hemisphere. We here use the Whole Atmosphere Community Climate Model (WACCM) to investigate the role of the summer stratosphere in shaping the conditions of the summer polar mesosphere. Using composite analyses, we show that in the absence of an anomalous summer mesospheric temperature gradient between the equator and the polar region, weak planetary wave forcing in the winter would lead to a warming of the summer mesosphere region instead of a cooling, and vice versa. This is opposing the temperature signal of the interhemispheric coupling that takes place in the mesosphere, in which a cold and calm winter stratosphere goes together with a cold summer mesopause. We hereby strengthen the evidence that the variability in the summer mesopause region is mainly driven by changes in the summer mesosphere rather than in the summer stratosphere.

Modeling winter hydrological processes under differing climatic conditions: Modifying WEPP

NASA Astrophysics Data System (ADS)

Dun, Shuhui

Water erosion is a serious and continuous environmental problem worldwide. In cold regions, soil freeze and thaw has great impacts on infiltration and erosion. Rain or snowmelt on a thawing soil can cause severe water erosion. Of equal importance is snow accumulation and snowmelt, which can be the predominant hydrological process in areas of mid- to high latitudes and forested watersheds. Modelers must properly simulate winter processes to adequately represent the overall hydrological outcome and sediment and chemical transport in these areas. Modeling winter hydrology is presently lacking in water erosion models. Most of these models are based on the functional Universal Soil Loss Equation (USLE) or its revised forms, e.g., Revised USLE (RUSLE). In RUSLE a seasonally variable soil erodibility factor (K) was used to account for the effects of frozen and thawing soil. Yet the use of this factor requires observation data for calibration, and such a simplified approach cannot represent the complicated transient freeze-thaw processes and their impacts on surface runoff and erosion. The Water Erosion Prediction Project (WEPP) watershed model, a physically-based erosion prediction software developed by the USDA-ARS, has seen numerous applications within and outside the US. WEPP simulates winter processes, including snow accumulation, snowmelt, and soil freeze-thaw, using an approach based on mass and energy conservation. However, previous studies showed the inadequacy of the winter routines in the WEPP model. Therefore, the objectives of this study were: (1) To adapt a modeling approach for winter hydrology based on mass and energy conservation, and to implement this approach into a physically-oriented hydrological model, such as WEPP; and (2) To assess this modeling approach through case applications to different geographic conditions. A new winter routine was developed and its performance was evaluated by incorporating it into WEPP (v2008.9) and then applying WEPP to four study sites at different spatial scales under different climatic conditions, including experimental plots in Pullman, WA and Morris, MN, two agricultural drainages in Pendleton, OR, and a forest watershed in Mica Creek, ID. The model applications showed promising results, indicating adequacy of the mass- and energy-balance-based approach for winter hydrology simulation.

Linking the South Atlantic Meridional Overturning Circulation and the Global Monsoons

NASA Astrophysics Data System (ADS)

Lopez, H.; Dong, S.; Goni, G. J.; Lee, S. K.

2016-02-01

This study tested the hypothesis whether low frequency decadal variability of the South Atlantic meridional heat transport (SAMHT) influences decadal variability of the global monsoons. A multi-century run from a state-of-the-art coupled general circulation model is used as basis for the analysis. Our findings indicate that multi-decadal variability of the South Atlantic Ocean plays a key role in modulating atmospheric circulation via interhemispheric changes in Atlantic Ocean heat content. Weaker SAMHT produces anomalous ocean heat divergence over the South Atlantic resulting in negative ocean heat content anomaly about 15 years later. This, in turn, forces a thermally direct anomalous interhemispheric Hadley circulation in the atmosphere, transporting heat from the northern hemisphere (NH) to the southern hemisphere (SH) and moisture from the SH to the NH, thereby intensify (weaken) summer (winter) monsoon in the NH and winter (summer) monsoon in the SH. Results also show that anomalous atmospheric eddies, both transient and stationary, transport heat northward in both hemispheres producing eddy heat flux convergence (divergence) in the NH (SH) around 15-30°, reinforcing the anomalous Hadley circulation. Overall, SAMHT decadal variability leads its atmospheric response by about 15 years, suggesting that the South Atlantic is a potential predictor of global climate variability.

Changes in the zonal mean flow, temperature, and planetary waves observed in the Northern Hemisphere mid-winter months during the last decades

NASA Astrophysics Data System (ADS)

Rakushina, E. V.; Ermakova, T. S.; Pogoreltsev, A. I.

2018-06-01

Four sets of data: the UK Met Office, Modern Era Retrospective-analysis for Research and Applications (MERRA), Japanese 55-year Reanalysis data (JRA-55), and ERA-Interim data (ERA) have been used to estimate the climatic variability of the zonal mean flow, temperature, and Stationary Planetary Waves (SPW1, SPW2) from the troposphere up to the lower mesosphere levels. The composites of the meteorological fields during mid-winter month have been averaged over the first (1995-2005) and second (2006-2016) 11 years intervals and have been compared mainly paying attention to interannual and intraseasonal variability. Results show that changes in the mean fields and SPW2 are weaker and statistical significance of these changes is lower in comparison with the changes observed in the intraseasonal variability of these characteristics. All data sets demonstrate a decrease of SPW1 amplitude at the higher-middle latitudes in the lower stratosphere and opposite effect in the upper stratosphere. However, there is an increase of the intraseasonal variability for all meteorological parameters and this rise is statistically significant. The results obtained show that UK Met Office data demonstrate stronger changes and increase of the intraseasonal variability in comparison with other data sets.

Centennial-scale vegetation dynamics and climate variability in SE Europe during Marine Isotope Stage 11 based on a pollen record from Lake Ohrid

NASA Astrophysics Data System (ADS)

Kousis, Ilias; Koutsodendris, Andreas; Peyron, Odile; Leicher, Niklas; Francke, Alexander; Wagner, Bernd; Giaccio, Biagio; Knipping, Maria; Pross, Jörg

2018-06-01

To better understand climate variability during Marine Isotope Stage (MIS) 11, we here present a new, centennial-scale-resolution pollen record from Lake Ohrid (Balkan Peninsula) derived from sediment cores retrieved during an International Continental Scientific Drilling Program (ICDP) campaign. Our palynological data, augmented by quantitative pollen-based climate reconstructions, provide insight into the vegetation dynamics and thus also climate variability in SE Europe during one of the best orbital analogues for the Holocene. Comparison of our palynological results with other proxy data from Lake Ohrid as well as with regional and global climate records shows that the vegetation in SE Europe responded sensitively both to long- and short-term climate change during MIS 11. The chronology of our palynological record is based on orbital tuning, and is further supported by the detection of a new tephra from the Vico volcano, central Italy, dated to 410 ± 2 ka. Our study indicates that MIS 11c (∼424-398 ka) was the warmest interval of MIS 11. The younger part of the interglacial (i.e., MIS 11b-11a; ∼398-367 ka) exhibits a gradual cooling trend passing over into MIS 10. It is characterized by considerable millennial-scale variability as inferred by six abrupt forest-contraction events. Interestingly, the first forest contraction occurred during full interglacial conditions of MIS 11c; this event lasted for ∼1.7 kyrs (406.2-404.5 ka) and was characterized by substantial reductions in winter temperature and annual precipitation. Most notably, it occurred ∼7 ka before the end of MIS 11c and ∼15 ka before the first strong ice-rafted debris event in the North Atlantic. Our findings suggest that millennial-scale climate variability during MIS 11 was established in Southern Europe already during MIS 11c, which is earlier than in the North Atlantic where it is registered only from MIS 11b onwards.

Using Clustering to Establish Climate Regimes from PCM Output

NASA Technical Reports Server (NTRS)

Oglesby, Robert; Arnold, James E. (Technical Monitor); Hoffman, Forrest; Hargrove, W. W.; Erickson, D.

2002-01-01

A multivariate statistical clustering technique--based on the k-means algorithm of Hartigan has been used to extract patterns of climatological significance from 200 years of general circulation model (GCM) output. Originally developed and implemented on a Beowulf-style parallel computer constructed by Hoffman and Hargrove from surplus commodity desktop PCs, the high performance parallel clustering algorithm was previously applied to the derivation of ecoregions from map stacks of 9 and 25 geophysical conditions or variables for the conterminous U.S. at a resolution of 1 sq km. Now applied both across space and through time, the clustering technique yields temporally-varying climate regimes predicted by transient runs of the Parallel Climate Model (PCM). Using a business-as-usual (BAU) scenario and clustering four fields of significance to the global water cycle (surface temperature, precipitation, soil moisture, and snow depth) from 1871 through 2098, the authors' analysis shows an increase in spatial area occupied by the cluster or climate regime which typifies desert regions (i.e., an increase in desertification) and a decrease in the spatial area occupied by the climate regime typifying winter-time high latitude perma-frost regions. The patterns of cluster changes have been analyzed to understand the predicted variability in the water cycle on global and continental scales. In addition, representative climate regimes were determined by taking three 10-year averages of the fields 100 years apart for northern hemisphere winter (December, January, and February) and summer (June, July, and August). The result is global maps of typical seasonal climate regimes for 100 years in the past, for the present, and for 100 years into the future. Using three-dimensional data or phase space representations of these climate regimes (i.e., the cluster centroids), the authors demonstrate the portion of this phase space occupied by the land surface at all points in space and time. Any single spot on the globe will exist in one of these climate regimes at any single point in time. By incrementing time, that same spot will trace out a trajectory or orbit between and among these climate regimes (or atmospheric states) in phase (or state) space. When a geographic region enters a state it never previously visited, a climatic change is said to have occurred. Tracing out the entire trajectory of a single spot on the globe yields a 'manifold' in state space representing the shape of its predicted climate occupancy. This sort of analysis enables a researcher to more easily grasp the multivariate behavior of the climate system.

Identification and future description of warming signatures over Pakistan with special emphasis on evolution of CO2 levels and temperature during the first decade of the twenty-first century.

PubMed

Haider, Khadija; Khokhar, Muhammad Fahim; Chishtie, Farrukh; RazzaqKhan, Waseem; Hakeem, Khalid Rehman

2017-03-01

Like other developing countries, Pakistan is also facing changes in temperature per decade and other climatic abnormalities like droughts and torrential rains. In order to assess and identify the extent of temperature change over Pakistan, the whole Pakistan was divided into five climatic zones ranging from very cold to hot and dry climates. Similarly, seasons in Pakistan are defined on the basis of monsoon variability as winter, pre-monsoon, monsoon, and post-monsoon. This study primarily focuses on the comparison of surface temperature observations from Pakistan Meteorological Department (PMD) network with PRECIS (Providing Regional Climates for Impacts Studies) model simulations. Results indicate that PRECIS underestimates the temperature in Northern Pakistan and during the winter season. However, there exists a fair agreement between PRECIS output and observed datasets in the lower plain and hot areas of the country. An absolute increase of 0.07 °C is observed in the mean temperature over Pakistan during the time period of 1951-2010. Especially, the increase is more significant (0.7 °C) during the last 14 years (1997-2010). Moreover, SCIAMACHY observations were used to explore the evolution of atmospheric CO 2 levels in comparison to temperature over Pakistan. CO 2 levels have shown an increasing trend during the first decade of the twenty-first century.

The forcing of southwestern Asia teleconnections by low-frequency sea surface temperature variability during boreal winter

USGS Publications Warehouse

Hoell, Andrew; Funk, Christopher C.; Mathew Barlow,

2015-01-01

Southwestern Asia, defined here as the domain bounded by 20°–40°N and 40°–70°E, which includes the nations of Iraq, Iran, Afghanistan, and Pakistan, is a water-stressed and semiarid region that receives roughly 75% of its annual rainfall during November–April. The November–April climate of southwestern Asia is strongly influenced by tropical Indo-Pacific variability on intraseasonal and interannual time scales, much of which can be attributed to sea surface temperature (SST) variations. The influences of lower-frequency SST variability on southwestern Asia climate during November–April Pacific decadal SST (PDSST) variability and the long-term trend in SST (LTSST) is examined. The U.S. Climate Variability and Predictability Program (CLIVAR) Drought Working Group forced global atmospheric climate models with PDSST and LTSST patterns, identified using empirical orthogonal functions, to show the steady atmospheric response to these modes of decadal to multidecadal SST variability. During November–April, LTSST forces an anticyclone over southwestern Asia, which results in reduced precipitation and increases in surface temperature. The precipitation and tropospheric circulation influences of LTSST are corroborated by independent observed precipitation and circulation datasets during 1901–2004. The decadal variations of southwestern Asia precipitation may be forced by PDSST variability, with two of the three models indicating that the cold phase of PDSST forces an anticyclone and precipitation reductions. However, there are intermodel circulation variations to PDSST that influence subregional precipitation patterns over the Middle East, southwestern Asia, and subtropical Asia. Changes in wintertime temperature and precipitation over southwestern Asia forced by LTSST and PDSST imply important changes to the land surface hydrology during the spring and summer.

Relationships between large-scale circulation patterns and carbon dioxide exchange by a deciduous forest

NASA Astrophysics Data System (ADS)

Zhang, Jingyong; Wu, Lingyun; Huang, Gang; Notaro, Michael

2011-02-01

In this study, we focus on a deciduous forest in central Massachusetts and investigate the relationships between global climate indices and CO2 exchange using eddy-covariance flux measurements from 1992 to 2007. Results suggest that large-scale circulation patterns influence the annual CO2 exchange in the forest through their effects on the local surface climate. Annual gross ecosystem exchange (GEE) in the forest is closely associated with spring El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO), previous fall Atlantic Multidecadal Oscillation (AMO), and previous winter East Pacific-North Pacific (EP-NP) pattern. Annual net ecosystem exchange (NEE) responds to previous fall AMO and PDO, while annual respiration (R) is impacted by previous fall ENSO and Pacific/North American Oscillation (PNA). Regressions based on these relationships are developed to simulate the annual GEE, NEE, and R. To avoid problems of multicollinearity, we compute a "Composite Index for GEE (CIGEE)" based on a linear combination of spring ENSO and PDO, fall AMO, and winter EP-NP and a "Composite Index for R (CIR)" based on a linear combination of fall ENSO and PNA. CIGEE, CIR, and fall AMO and PDO can explain 41, 27, and 40% of the variance of the annual GEE, R, and NEE, respectively. We further apply the methodology to two other northern midlatitude forests and find that interannual variabilities in NEE of the two forests are largely controlled by large-scale circulation patterns. This study suggests that global climate indices provide the potential for predicting CO2 exchange variability in the northern midlatitude forests.

Inter-annual dynamics of the Barents Sea red king crab (Paralithodes camtschaticus) stock indices in relation to environmental factors

NASA Astrophysics Data System (ADS)

Dvoretsky, Alexander G.; Dvoretsky, Vladimir G.

2016-12-01

Knowledge of relationships between environmental variables and biological processes can greatly improve fisheries assessment and management in commercially important species. We analyzed the effects of environmental factors (climatic indices and water temperature) on the stock characteristics (total population number, number of pre-recruits and number of legal males) of the red king crab (Paralithodes camtschaticus), an introduced species in the Barents Sea. Stock trends in red king crab appear to be related to decadal climate shifts. Abundances were negatively related to the North Atlantic Oscillation index (NAO) in August and positively related to water temperature in late winter-early summer. Total and commercial stock abundance were negatively correlated with the lag-1 Arctic Oscillation index (AO) in August and the lag-2 winter NAO index. The total number of P. camtschaticus was most strongly associated with water temperature in spring and summer and NAO/AO indices in April and May. Lagged NAO indices in February and August (9 or 10 yr) had a positive relationship to the commercial stock of P. camtschaticus. These findings suggest that temperature conditions of current and previous year affect natural mortality of larvae and juvenile red king crabs. Warmer temperature conditions lead to increased biomass of red king crab food items. Negative correlations between climatic indices and the red king crab stocks may be associated with predator pressure on juvenile red king crabs or higher mortality because of predator or parasite pressure and diseases. The associations between stock indices and environmental variables could help better predict recruitment patterns of P. camtschaticus.

Decadal changes of reference crop evapotranspiration attribution: Spatial and temporal variability over China 1960-2011

NASA Astrophysics Data System (ADS)

Fan, Ze-Xin; Thomas, Axel

2018-05-01

Atmospheric evaporative demand can be used as a measure of the hydrological cycle and the global energy balance. Its long-term variation and the role of driving climatic factors have received increasingly attention in climate change studies. FAO-Penman-Monteith reference crop evapotranspiration rates were estimated for 644 meteorological stations over China for the period 1960-2011 to analyze spatial and temporal attribution variability. Attribution of climatic variables to reference crop evapotranspiration rates was not stable over the study period. While for all of China the contribution of sunshine duration remained relatively stable, the importance of relative humidity increased considerably during the last two decades, particularly in winter. Spatially distributed attribution analysis shows that the position of the center of maximum contribution of sunshine duration has shifted from Southeast to Northeast China while in West China the contribution of wind speed has decreased dramatically. In contrast relative humidity has become an important factor in most parts of China. Changes in the Asian Monsoon circulation may be responsible for altered patterns of cloudiness and a general decrease of wind speeds over China. The continuously low importance of temperature confirms that global warming does not necessarily lead to rising atmospheric evaporative demand.

Characterizing the nature and variability of avalanche hazard in western Canada

NASA Astrophysics Data System (ADS)

Shandro, Bret; Haegeli, Pascal

2018-04-01

The snow and avalanche climate types maritime, continental and transitional are well established and have been used extensively to characterize the general nature of avalanche hazard at a location, study inter-seasonal and large-scale spatial variabilities and provide context for the design of avalanche safety operations. While researchers and practitioners have an experience-based understanding of the avalanche hazard associated with the three climate types, no studies have described the hazard character of an avalanche climate in detail. Since the 2009/2010 winter, the consistent use of Statham et al. (2017) conceptual model of avalanche hazard in public avalanche bulletins in Canada has created a new quantitative record of avalanche hazard that offers novel opportunities for addressing this knowledge gap. We identified typical daily avalanche hazard situations using self-organizing maps (SOMs) and then calculated seasonal prevalence values of these situations. This approach produces a concise characterization that is conducive to statistical analyses, but still provides a comprehensive picture that is informative for avalanche risk management due to its link to avalanche problem types. Hazard situation prevalence values for individual seasons, elevations bands and forecast regions provide unprecedented insight into the inter-seasonal and spatial variability of avalanche hazard in western Canada.

Interannual variability (1979-2013) of the North-Western Mediterranean deep water mass formation: past observation reanalysis and coupled ocean-atmosphere high-resolution modelling

NASA Astrophysics Data System (ADS)

Somot, Samuel; Houpert, Loic; Sevault, Florence; Testor, Pierre; Bosse, Anthony; Durrieu de Madron, Xavier; Dubois, Clotilde; Herrmann, Marine; Waldman, Robin; Bouin, Marie-Noëlle; Cassou, Christophe

2015-04-01

The North-Western Mediterranean Sea is known as one of the only place in the world where open-sea deep convection occurs (often up to more than 2000m) with the formation of the Western Mediterranean Deep Water (WMDW). This phenomena is mostly driven by local preconditioning of the water column and strong buoyancy losses during Winter. At the event scale, the WMDW formation is characterized by different phases (preconditioning, strong mixing, restratification and spreading), intense air-sea interaction and strong meso-scale activity but, on a longer time scale, it also shows a large interannual variability and may be strongly affected by climate change with impact on the regional biogeochemistry. Therefore observing, simulating and understanding the long-term temporal variability of the North-Western Mediterranean deep water formation is still today a very challenging task. We try here to tackle those issues thanks to (1) a thorough reanalysis of past in-situ observations (CTD, Argo, surface and deep moorings, gliders) and (2) an ERA-Interim driven simulation using a recently-developed fully coupled Regional Climate System Model (CNRM-RCSM4, Sevault et al. 2014). The multi-decadal simulation (1979-2013) is designed to be temporally and spatially homogeneous with a realistic chronology, a high resolution representation of both the regional ocean and atmosphere, specific initial conditions, a long-term spin-up and a full ocean-atmosphere coupling without constraint at the air-sea interface. The observation reanalysis allows to reconstruct interannual time series of deep water formation indicators (ocean surface variables, mixed layer depth, surface of the convective area, dense water volumes and characteristics of the deep water). Using the observation-based indicators and the model outputs, the 34 Winters of the period 1979-2013 are analysed in terms of weather regimes, related Winter air-sea fluxes, ocean preconditioning, mixed layer depth, surface of the convective area, deep water formation rate and long-term evolution of the deep water hydrology.

The Effect of Climate Variability on Gray Whales (Eschrichtius robustus) within Their Wintering Areas

PubMed Central

Salvadeo, Christian J.; Gómez-Gallardo U., Alejandro; Nájera-Caballero, Mauricio; Urbán-Ramirez, Jorge; Lluch-Belda, Daniel

2015-01-01

The environmental conditions of the breeding and feeding grounds of the gray whale (Eschrichtius robustus) fluctuates at inter-annual scales in response to regional and basin climate patterns. Thus, the goals of this study were to assess if there are any relationships between summer sea ice on their feeding ground and counts of gray whale mother-calf (MC) pairs at Ojo de Liebre Lagoon (OLL); and if El Niño Southern Oscillation (ENSO) influences the winter distribution of gray whales MC pairs in the three primary breeding lagoons of OLL, San Ignacio Lagoon (SIL) and Santo Domingo Channel north of Bahia Magdalena (SDCh). Maximum February counts of MC pairs were compared with the length of the open-water season at the Bering Sea during the previous year. Then, an ENSO index and sea surface temperature anomalies outside the primary lagoons was compared with the maximum February counts of MC pairs at these lagoons. Results showed that maximum counts of MC pairs in OLL correlates with sea ice conditions in their feeding grounds from the previous feeding season, and this relationship can be attributed to changes in nutritive condition of females. ENSO-related variability influences distribution of MC pairs in the southern area of SDCh during the warm 1998 El Niño and cold 1999 La Niña. This supports the hypothesis that changes in the whales’ distribution related to sea temperature occurs to reduce thermal-stress and optimize energy utilization for newborn whales. Although this last conclusion should be considered in view of the limited data available from all the whales’ wintering locations in all the years considered. PMID:26309028

Seasonal Variations in Mortality, Clinical, and Laboratory Parameters in Hemodialysis Patients: A 5-Year Cohort Study

PubMed Central

Usvyat, Len A.; Carter, Mary; Thijssen, Stephan; Kooman, Jeroen P.; van der Sande, Frank M.; Zabetakis, Paul; Balter, Paul; Levin, Nathan W.; Kotanko, Peter

2012-01-01

Summary Background and objectives Mortality varies seasonally in the general population, but it is unknown whether this phenomenon is also present in hemodialysis patients with known higher background mortality and emphasis on cardiovascular causes of death. This study aimed to assess seasonal variations in mortality, in relation to clinical and laboratory variables in a large cohort of chronic hemodialysis patients over a 5-year period. Design, setting, participants, & measurements This study included 15,056 patients of 51 Renal Research Institute clinics from six states of varying climates in the United States. Seasonal differences were assessed by chi-squared tests and univariate and multivariate cosinor analyses. Results Mortality, both all-cause and cardiovascular, was significantly higher during winter compared with other seasons (14.2 deaths per 100 patient-years in winter, 13.1 in spring, 12.3 in autumn, and 11.9 in summer). The increase in mortality in winter was more pronounced in younger patients, as well as in whites and in men. Seasonal variations were similar across climatologically different regions. Seasonal variations were also observed in neutrophil/lymphocyte ratio and serum calcium, potassium, and platelet values. Differences in mortality disappeared when adjusted for seasonally variable clinical parameters. Conclusions In a large cohort of dialysis patients, significant seasonal variations in overall and cardiovascular mortality were observed, which were consistent over different climatic regions. Other physiologic and laboratory parameters were also seasonally different. Results showed that mortality differences were related to seasonality of physiologic and laboratory parameters. Seasonal variations should be taken into account when designing and interpreting longitudinal studies in dialysis patients. PMID:22096041

Interannual variability of western North Pacific SST anomalies and its impact on North Pacific and North America

NASA Astrophysics Data System (ADS)

Park, Jae-Heung; An, Soon-Il; Kug, Jong-Seong

2017-12-01

In this study, the interannual variability of sea surface temperature (SST) and its atmospheric teleconnection over the western North Pacific (WNP) toward the North Pacific/North America during boreal winter are investigated. First, we defined the WNP mode as the first empirical orthogonal function (EOF) mode of SST anomalies over the WNP region (100-165°E, 0-35°N), of which the principle component time-series are significantly correlated with several well-known climate modes such as the warm pool mode which is the second EOF mode of the tropical to North Pacific SST anomalies, North Pacific oscillation (NPO), North Pacific gyre oscillation (NPGO), and central Pacific (CP)-El Niño at 95% confidence level, but not correlated with the eastern Pacific (EP)-El Niño. The warm phase of the WNP mode (sea surface warming) is initiated by anomalous southerly winds through reduction of wind speed with the background of northerly mean winds over the WNP during boreal winter, i.e., reduced evaporative cooling. Meanwhile, the atmospheric response to the SST warming pattern and its diabatic heating further enhance the southerly wind anomaly, referred to the wind-evaporation-SST (WES) feedback. Thus, the WNP mode is developed and maintained through winter until spring, when the northerly mean wind disappears. Furthermore, it is also known that anomalous upper-level divergence associated with WNP mode leads to the NPO-like structure over the North Pacific and the east-west pressure contrast pattern over the North America through Rossby wave propagation, impacting the climate over the North Pacific and North America.

The Effect of Climate Variability on Gray Whales (Eschrichtius robustus) within Their Wintering Areas.

PubMed

Salvadeo, Christian J; Gómez-Gallardo U, Alejandro; Nájera-Caballero, Mauricio; Urbán-Ramirez, Jorge; Lluch-Belda, Daniel

2015-01-01

The environmental conditions of the breeding and feeding grounds of the gray whale (Eschrichtius robustus) fluctuates at inter-annual scales in response to regional and basin climate patterns. Thus, the goals of this study were to assess if there are any relationships between summer sea ice on their feeding ground and counts of gray whale mother-calf (MC) pairs at Ojo de Liebre Lagoon (OLL); and if El Niño Southern Oscillation (ENSO) influences the winter distribution of gray whales MC pairs in the three primary breeding lagoons of OLL, San Ignacio Lagoon (SIL) and Santo Domingo Channel north of Bahia Magdalena (SDCh). Maximum February counts of MC pairs were compared with the length of the open-water season at the Bering Sea during the previous year. Then, an ENSO index and sea surface temperature anomalies outside the primary lagoons was compared with the maximum February counts of MC pairs at these lagoons. Results showed that maximum counts of MC pairs in OLL correlates with sea ice conditions in their feeding grounds from the previous feeding season, and this relationship can be attributed to changes in nutritive condition of females. ENSO-related variability influences distribution of MC pairs in the southern area of SDCh during the warm 1998 El Niño and cold 1999 La Niña. This supports the hypothesis that changes in the whales' distribution related to sea temperature occurs to reduce thermal-stress and optimize energy utilization for newborn whales. Although this last conclusion should be considered in view of the limited data available from all the whales' wintering locations in all the years considered.

Decadal variability in the Northern Hemisphere winter circulation: Role of internal and external drivers

NASA Astrophysics Data System (ADS)

Maliniemi, V.; Asikainen, T.; Mursula, K.

2017-12-01

Northern Hemisphere winter circulation is known to be affected by both internal and external (solar-related) forcings. Earlier studies have shown ENSO and volcanic activity to produce negative and positive North Atlantic Oscillation (NAO) type responses, respectively. In addition, recent studies have shown a positive NAO response related to both geomagnetic activity (proxy for solar wind driven particle precipitation) and sunspot activity (proxy for solar irradiance). These solar-related signals have been suggested to be due to the changes in the polar vortex. Here the relative role of these four internal and external drivers on wintertime circulation in the Northern Hemisphere is studied. The phase of the quasi-biennial oscillation (QBO) is used to study the driver responses for different stratospheric conditions. Moreover, the effects are separated for early (Dec/Jan) and late (Feb/Mar) winter. The global pattern of ENSO is very similar (negative NAO) otherwise, but in early winter and westerly QBO the pattern is changed in the Atlantic sector to a weakly positive NAO. The positive NAO pattern due to volcanic activity is more pronounced for westerly QBO in both early and late winter. The positive NAO pattern produced by geomagnetic activity is obtained during easterly QBO phase in both early and late winter. Sunspot related NAO response in late winter is also strongly modulated by the QBO phase. These results imply that the stratospheric conditions expressed by QBO significantly modulate the way the internal and external drivers affect the Northern Hemisphere winter climate.

Can Regional Climate Models Improve Warm Season Forecasts in the North American Monsoon Region?

NASA Astrophysics Data System (ADS)

Dominguez, F.; Castro, C. L.

2009-12-01

The goal of this work is to improve warm season forecasts in the North American Monsoon Region. To do this, we are dynamically downscaling warm season CFS (Climate Forecast System) reforecasts from 1982-2005 for the contiguous U.S. using the Weather Research and Forecasting (WRF) regional climate model. CFS is the global coupled ocean-atmosphere model used by the Climate Prediction Center (CPC), a branch of the National Center for Environmental Prediction (NCEP), to provide official U.S. seasonal climate forecasts. Recently, NCEP has produced a comprehensive long-term retrospective ensemble CFS reforecasts for the years 1980-2005. These reforecasts show that CFS model 1) has an ability to forecast tropical Pacific SSTs and large-scale teleconnection patterns, at least as evaluated for the winter season; 2) has greater skill in forecasting winter than summer climate; and 3) demonstrates an increase in skill when a greater number of ensembles members are used. The decrease in CFS skill during the warm season is due to the fact that the physical mechanisms of rainfall at this time are more related to mesoscale processes, such as the diurnal cycle of convection, low-level moisture transport, propagation and organization of convection, and surface moisture recycling. In general, these are poorly represented in global atmospheric models. Preliminary simulations for years with extreme summer climate conditions in the western and central U.S. (specifically 1988 and 1993) show that CFS-WRF simulations can provide a more realistic representation of convective rainfall processes. Thus a RCM can potentially add significant value in climate forecasting of the warm season provided the downscaling methodology incorporates the following: 1) spectral nudging to preserve the variability in the large scale circulation while still permitting the development of smaller-scale variability in the RCM; and 2) use of realistic soil moisture initial condition, in this case provided by the North American Regional Reanalysis. With these conditions, downscaled CFS-WRF reforecast simulations can produce realistic continental-scale patterns of warm season precipitation. This includes a reasonable representation of the North American monsoon in the southwest U.S. and northwest Mexico, which is notoriously difficult to represent in a global atmospheric model. We anticipate that this research will help lead the way toward substantially improved real time operational forecasts of North American summer climate with a RCM.

Remotely Sensed Spatio-Temporal Variability of Snow Cover in Himalayan Region with Perspective of Climate Change

NASA Astrophysics Data System (ADS)

Dhakal, S.; Ojha, S.

2017-12-01

Climate change and its impact of water resource have gained tremendous attention among scientific committee, governments and other stakeholders since last couple of decades, especially in Himalayan region. In this study, we purpose remotely sensed measurements to monitor snow cover, both spatially and temporal, and assess climate change impact on water resource. The snow cover data from MODIS satellite (2000-2010) have been used to analyze some climate change indicators. In particular, the variability in the maximum snow extent with elevations, its temporal variability (8-day, monthly, seasonal and annual), its variation trend and its relation with temperature have been analyzed. The snow products used in this study are the maximum snow extent and fractional snow covers, which come in 8-day temporal and 500m and 0.05 degree spatial resolutions, respectively. The results showed a tremendous potential of the MODIS snow product for studying the spatial and temporal variability of snow as well as the study of climate change impact in large and inaccessible regions like the Himalayas. The snow area extent (SAE) (%) time series exhibits similar patterns during seven hydrological years, even though there are some deviations in the accumulation and melt periods. The analysis showed relatively well inverse relation between the daily mean temperature and SAE during the melting period. Some important trends of snow fall are also observed. In particular, the decreasing trend in January and increasing trend in late winter and early spring may be interpreted as a signal of a possible seasonal shift. However, it requires more years of data to verify this conclusion.

Impact of transient climate change upon Grouse population dynamics in the Italian Alps

NASA Astrophysics Data System (ADS)

Pirovano, Andrea; Bocchiola, Daniele

2010-05-01

Understanding the effect of short to medium term weather condition, and of transient global warming upon wildlife species life history is essential to predict the demographic consequences therein, and possibly develop adaptation strategies, especially in game species, where hunting mortality may play an important role in population dynamics. We carried out a preliminary investigation of observed impact of weather variables upon population dynamics indexes of three alpine Grouse species (i.e. Rock Ptarmigan, Lagopus Mutus, Black Grouse, Tetrao Tetrix, Rock Partridge, Alectoris Graeca), nested within central Italian Alps, based upon 15 years (1995-2009) of available censuses data, provided by the Sondrio Province authority. We used a set of climate variables already highlighted within recent literature for carrying considerable bearing on Grouse population dynamics, including e.g. temperature at hatching time and during winter, snow cover at nesting, and precipitation during nursing period. We then developed models of Grouses' population dynamics by explicitly driving population change according to their dependence upon the significant weather variables and population density and we evaluated objective indexes to assess the so obtained predictive power. Eventually, we develop projection of future local climate, based upon locally derived trends, and upon projections from GCMs (A2 IPCC storyline) already validated for the area, to project forward in time (until 2100 or so) the significant climatic variables, which we then use to force population dynamics models of the target species. The projected patterns obtained through this exercise are discussed and compared against those expected under stationary climate conditions at present, and preliminary conclusions are drawn.

Descriptors of natural thermal regimes in streams and their responsiveness to change in the Pacific Northwest of North America

USGS Publications Warehouse

Arismendi, Ivan; Johnson, Sherri L.; Dunham, Jason B.; Haggerty, Roy

2013-01-01

1. Temperature is a major driver of ecological processes in stream ecosystems, yet the dynamics of thermal regimes remain poorly described. Most work has focused on relatively simple descriptors that fail to capture the full range of conditions that characterise thermal regimes of streams across seasons or throughout the year. 2. To more completely describe thermal regimes, we developed several descriptors of magnitude, variability, frequency, duration and timing of thermal events throughout a year. We evaluated how these descriptors change over time using long-term (1979–2009), continuous temperature data from five relatively undisturbed cold-water streams in western Oregon, U.S.A. In addition to trends for each descriptor, we evaluated similarities among them, as well as patterns of spatial coherence, and temporal synchrony. 3. Using different groups of descriptors, we were able to more fully capture distinct aspects of the full range of variability in thermal regimes across space and time. A subset of descriptors showed both higher coherence and synchrony and, thus, an appropriate level of responsiveness to examine evidence of regional climatic influences on thermal regimes. Most notably, daily minimum values during winter–spring were the most responsive descriptors to potential climatic influences. 4. Overall, thermal regimes in streams we studied showed high frequency and low variability of cold temperatures during the cold-water period in winter and spring, and high frequency and high variability of warm temperatures during the warm-water period in summer and autumn. The cold and warm periods differed in the distribution of events with a higher frequency and longer duration of warm events in summer than cold events in winter. The cold period exhibited lower variability in the duration of events, but showed more variability in timing. 5. In conclusion, our results highlight the importance of a year-round perspective in identifying the most responsive characteristics or descriptors of thermal regimes in streams. The descriptors we provide herein can be applied across hydro-ecological regions to evaluate spatial and temporal patterns in thermal regimes. Evaluation of coherence and synchrony of different components of thermal regimes can facilitate identification of impacts of regional climate variability or local human or natural influences.

Short winters threaten temperate fish populations

PubMed Central

Farmer, Troy M.; Marschall, Elizabeth A.; Dabrowski, Konrad; Ludsin, Stuart A.

2015-01-01

Although climate warming is expected to benefit temperate ectotherms by lengthening the summer growing season, declines in reproductive success following short, warm winters may counter such positive effects. Here we present long-term (1973–2010) field patterns for Lake Erie yellow perch, Perca flavescens, which show that failed annual recruitment events followed short, warm winters. Subsequent laboratory experimentation and field investigations revealed how reduced reproductive success following short, warm winters underlie these observed field patterns. Following short winters, females spawn at warmer temperatures and produce smaller eggs that both hatch at lower rates and produce smaller larvae than females exposed to long winters. Our research suggests that continued climate warming can lead to unanticipated, negative effects on temperate fish populations. PMID:26173734

Remote Linkages to Anomalous Winter Atmospheric Ridging over the Northeastern Pacific

NASA Technical Reports Server (NTRS)

Swain, Daniel L.; Singh, Deepti; Horton, Daniel E.; Mankin, Justin S.; Ballard, Tristan C.; Diffenbaugh, Noah S.

2017-01-01

Severe drought in California between 2013 and 2016 has been linked to the multiyear persistence of anomalously high atmospheric pressure over the northeastern Pacific Ocean, which deflected the Pacific storm track northward and suppressed regional precipitation during California's winter 'rainy season.' Multiple hypotheses have emerged regarding why this high pressure ridge near the west coast of North America was so resilient-including unusual sea surface temperature patterns in the Pacific Ocean, reductions in Arctic sea ice, random atmospheric variability, or some combination thereof. Here we explore relationships between previously documented atmospheric conditions over the North Pacific and several potential remote oceanic and cryospheric influences using both observational data and a large ensemble of climate model simulations. Our results suggest that persistent wintertime atmospheric ridging similar to that implicated in California's 2013-2016 drought can at least partially be linked to unusual Pacific sea surface temperatures, and that Pacific Ocean conditions may offer some degree of cool-season foresight in this region despite the presence of substantial internal variability.

Remote Linkages to Anomalous Winter Atmospheric Ridging Over the Northeastern Pacific

NASA Astrophysics Data System (ADS)

Swain, Daniel L.; Singh, Deepti; Horton, Daniel E.; Mankin, Justin S.; Ballard, Tristan C.; Diffenbaugh, Noah S.

2017-11-01

Severe drought in California between 2013 and 2016 has been linked to the multiyear persistence of anomalously high atmospheric pressure over the northeastern Pacific Ocean, which deflected the Pacific storm track northward and suppressed regional precipitation during California's winter "rainy season." Multiple hypotheses have emerged regarding why this high pressure ridge near the west coast of North America was so resilient—including unusual sea surface temperature patterns in the Pacific Ocean, reductions in Arctic sea ice, random atmospheric variability, or some combination thereof. Here we explore relationships between previously documented atmospheric conditions over the North Pacific and several potential remote oceanic and cryospheric influences using both observational data and a large ensemble of climate model simulations. Our results suggest that persistent wintertime atmospheric ridging similar to that implicated in California's 2013-2016 drought can at least partially be linked to unusual Pacific sea surface temperatures and that Pacific Ocean conditions may offer some degree of cool-season foresight in this region despite the presence of substantial internal variability.

Assessing the sensitivity of avian species abundance to land cover and climate

USGS Publications Warehouse

LeBrun, Jaymi J.; Thogmartin, Wayne E.; Thompson, Frank R.; Dijak, William D.; Millspaugh, Joshua J.

2016-01-01

Climate projections for the Midwestern United States predict southerly climates to shift northward. These shifts in climate could alter distributions of species across North America through changes in climate (i.e., temperature and precipitation), or through climate-induced changes on land cover. Our objective was to determine the relative impacts of land cover and climate on the abundance of five bird species in the Central United States that have habitat requirements ranging from grassland and shrubland to forest. We substituted space for time to examine potential impacts of a changing climate by assessing climate and land cover relationships over a broad latitudinal gradient. We found positive and negative relationships of climate and land cover factors with avian abundances. Habitat variables drove patterns of abundance in migratory and resident species, although climate was also influential in predicting abundance for some species occupying more open habitat (i.e., prairie warbler, blue-winged warbler, and northern bobwhite). Abundance of northern bobwhite increased with winter temperature and was the species exhibiting the most significant effect of climate. Models for birds primarily occupying early successional habitats performed better with a combination of habitat and climate variables whereas models of species found in contiguous forest performed best with land cover alone. These varied species-specific responses present unique challenges to land managers trying to balance species conservation over a variety of land covers. Management activities focused on increasing forest cover may play a role in mitigating effects of future climate by providing habitat refugia to species vulnerable to projected changes. Conservation efforts would be best served focusing on areas with high species abundances and an array of habitats. Future work managing forests for resilience and resistance to climate change could benefit species already susceptible to climate impacts.

The 1430s: a cold period of extraordinary internal climate variability during the early Spörer Minimum with social and economic impacts in north-western and central Europe

NASA Astrophysics Data System (ADS)

Camenisch, Chantal; Keller, Kathrin M.; Salvisberg, Melanie; Amann, Benjamin; Bauch, Martin; Blumer, Sandro; Brázdil, Rudolf; Brönnimann, Stefan; Büntgen, Ulf; Campbell, Bruce M. S.; Fernández-Donado, Laura; Fleitmann, Dominik; Glaser, Rüdiger; González-Rouco, Fidel; Grosjean, Martin; Hoffmann, Richard C.; Huhtamaa, Heli; Joos, Fortunat; Kiss, Andrea; Kotyza, Oldřich; Lehner, Flavio; Luterbacher, Jürg; Maughan, Nicolas; Neukom, Raphael; Novy, Theresa; Pribyl, Kathleen; Raible, Christoph C.; Riemann, Dirk; Schuh, Maximilian; Slavin, Philip; Werner, Johannes P.; Wetter, Oliver

2016-12-01

Changes in climate affected human societies throughout the last millennium. While European cold periods in the 17th and 18th century have been assessed in detail, earlier cold periods received much less attention due to sparse information available. New evidence from proxy archives, historical documentary sources and climate model simulations permit us to provide an interdisciplinary, systematic assessment of an exceptionally cold period in the 15th century. Our assessment includes the role of internal, unforced climate variability and external forcing in shaping extreme climatic conditions and the impacts on and responses of the medieval society in north-western and central Europe.Climate reconstructions from a multitude of natural and anthropogenic archives indicate that the 1430s were the coldest decade in north-western and central Europe in the 15th century. This decade is characterised by cold winters and average to warm summers resulting in a strong seasonal cycle in temperature. Results from comprehensive climate models indicate consistently that these conditions occurred by chance due to the partly chaotic internal variability within the climate system. External forcing like volcanic eruptions tends to reduce simulated temperature seasonality and cannot explain the reconstructions. The strong seasonal cycle in temperature reduced food production and led to increasing food prices, a subsistence crisis and a famine in parts of Europe. Societies were not prepared to cope with failing markets and interrupted trade routes. In response to the crisis, authorities implemented numerous measures of supply policy and adaptation such as the installation of grain storage capacities to be prepared for future food production shortfalls.

Assessment of surface air temperature over the Arctic Ocean in reanalysis and IPCC AR4 model simulations with IABP/POLES observations

NASA Astrophysics Data System (ADS)

Liu, Jiping; Zhang, Zhanhai; Hu, Yongyun; Chen, Liqi; Dai, Yongjiu; Ren, Xiaobo

2008-05-01

The surface air temperature (SAT) over the Arctic Ocean in reanalyses and global climate model simulations was assessed using the International Arctic Buoy Programme/Polar Exchange at the Sea Surface (IABP/POLES) observations for the period 1979-1999. The reanalyses, including the National Centers for Environmental Prediction Reanalysis II (NCEP2) and European Centre for Medium-Range Weather Forecast 40-year Reanalysis (ERA40), show encouraging agreement with the IABP/POLES observations, although some spatiotemporal discrepancies are noteworthy. The reanalyses have warm annual mean biases and underestimate the observed interannual SAT variability in summer. Additionally, NCEP2 shows an excessive warming trend. Most model simulations (coordinated by the International Panel on Climate Change for its Fourth Assessment Report) reproduce the annual mean, seasonal cycle, and trend of the observed SAT reasonably well, particularly the multi-model ensemble mean. However, large discrepancies are found. Some models have the annual mean SAT biases far exceeding the standard deviation of the observed interannul SAT variability and the across-model standard deviation. Spatially, the largest inter-model variance of the annual mean SAT is found over the North Pole, Greenland Sea, Barents Sea and Baffin Bay. Seasonally, a large spread of the simulated SAT among the models is found in winter. The models show interannual variability and decadal trend of various amplitudes, and can not capture the observed dominant SAT mode variability and cooling trend in winter. Further discussions of the possible attributions to the identified SAT errors for some models suggest that the model's performance in the sea ice simulation is an important factor.

Assessing climate change impacts on winter cover crop nitrate uptake efficiency on the coastal plain of the Chesapeake Bay watershed using the SWAT model

USDA-ARS?s Scientific Manuscript database

Climate change is expected to exacerbate water quality degradation in the Chesapeake Bay watershed (CBW). Winter cover crops (WCCs) have been widely implemented in this region owing to their high effectiveness at reducing nitrate loads. However, little is known about climate change impacts on the ef...

NOAA: Strong El Niño sets the stage for 2015-2016 winter weather

Science.gov Websites

El Niño, among the strongest on record, is expected to influence weather and climate patterns this NOAA HOME WEATHER OCEANS FISHERIES CHARTING SATELLITES CLIMATE RESEARCH COASTS CAREERS National Temperature. Temperature - U.S. Winter Outlook: 2015-2016 (Credit: NOAA) Forecasters at NOAA's Climate

Mesoscale numerical modeling of meteorological events in a strong topographic gradient in the northeastern part of Mexico

NASA Astrophysics Data System (ADS)

Pineda-Martinez, Luis F.; Carbajal, Noel

2009-08-01

A series of numerical experiments were carried out to study the effect of meteorological events such as warm and cold air masses on climatic features and variability of a understudied region with strong topographic gradients in the northeastern part of Mexico. We applied the mesoscale model MM5. We investigated the influence of soil moisture availability in the performance of the model under two representative events for winter and summer. The results showed that a better resolution in land use cover improved the agreement among observed and calculated data. The topography induces atmospheric circulation patterns that determine the spatial distribution of climate and seasonal behavior. The numerical experiments reveal regions favorable to forced convection on the eastern side of the mountain chains Eastern Sierra Madre and Sierra de Alvarez. These processes affect the vertical and horizontal structure of the meteorological variables along the topographic gradient.

Deriving forest fire ignition risk with biogeochemical process modelling.

PubMed

Eastaugh, C S; Hasenauer, H

2014-05-01

Climate impacts the growth of trees and also affects disturbance regimes such as wildfire frequency. The European Alps have warmed considerably over the past half-century, but incomplete records make it difficult to definitively link alpine wildfire to climate change. Complicating this is the influence of forest composition and fuel loading on fire ignition risk, which is not considered by purely meteorological risk indices. Biogeochemical forest growth models track several variables that may be used as proxies for fire ignition risk. This study assesses the usefulness of the ecophysiological model BIOME-BGC's 'soil water' and 'labile litter carbon' variables in predicting fire ignition. A brief application case examines historic fire occurrence trends over pre-defined regions of Austria from 1960 to 2008. Results show that summer fire ignition risk is largely a function of low soil moisture, while winter fire ignitions are linked to the mass of volatile litter and atmospheric dryness.

Effects of increased wind power generation on Mid-Norway's energy balance under climate change: A market based approach

NASA Astrophysics Data System (ADS)

Francois, Baptiste; Martino, Sara; Tofte, Lena; Hingray, Benoit; Mo, Birger; Creutin, Jean-Dominique

2017-04-01

Thanks to its huge water storage capacity, Norway has an excess of energy generation at annual scale, although significant regional disparity exists. On average, the Mid-Norway region has an energy deficit and needs to import more electricity than it exports. We show that this energy deficit can be reduced with an increase in wind generation and transmission line capacity, even in future climate scenarios where both mean annual temperature and precipitation are changed. For the considered scenarios, the deficit observed in winter disappears, i.e. when electricity consumption and prices are high. At the annual scale, the deficit behavior depends more on future changes in precipitation. Another consequence of changes in wind production and transmission capacity is the modification of electricity exchanges with neighboring regions which are also modified both in terms of average, variability and seasonality. Keywords: Variable renewable energy, Wind, Hydro, Energy balance, Energy market

A regime perspective on the North Atlantic eddy-driven jet stream response to sudden stratospheric warmings

NASA Astrophysics Data System (ADS)

Maycock, A.; Masukwedza, G.; Hitchcock, P.

2017-12-01

The winter North Atlantic eddy-driven jet (NAJ) has been shown to exhibit three preferred latitudinal positions. Here we examine, for the first time, the influence of major Sudden Stratospheric Warmings (SSWs) on the regime behaviour of the NAJ using an ensemble of climate model experiments with stratospheric conditions nudged towards a major SSW, but with each ensemble member having freely evolving tropospheric conditions. The SSW experiment is compared to a control ensemble in which stratospheric variability is absent. The experiments show that the SSW leads to an increased occupancy of the southerly NAJ state and reduced occupancy of the northerly state. This effect is distinct from the mean southward shift of the NAJ identified in many previous studies, and instead suggests changes to the characteristics of NAJ variability as a result of SSWs. These results may aid in understanding the mechanisms by which SSWs impact on Euro-Atlantic climate.

Deriving forest fire ignition risk with biogeochemical process modelling☆

PubMed Central

Eastaugh, C.S.; Hasenauer, H.

2014-01-01

Climate impacts the growth of trees and also affects disturbance regimes such as wildfire frequency. The European Alps have warmed considerably over the past half-century, but incomplete records make it difficult to definitively link alpine wildfire to climate change. Complicating this is the influence of forest composition and fuel loading on fire ignition risk, which is not considered by purely meteorological risk indices. Biogeochemical forest growth models track several variables that may be used as proxies for fire ignition risk. This study assesses the usefulness of the ecophysiological model BIOME-BGC's ‘soil water’ and ‘labile litter carbon’ variables in predicting fire ignition. A brief application case examines historic fire occurrence trends over pre-defined regions of Austria from 1960 to 2008. Results show that summer fire ignition risk is largely a function of low soil moisture, while winter fire ignitions are linked to the mass of volatile litter and atmospheric dryness. PMID:26109905

Climate, streamflow, and legacy effects on growth of riparian Populus angustifolia in the arid San Luis Valley, Colorado

USGS Publications Warehouse

Andersen, Douglas

2016-01-01

Knowledge of the factors affecting the vigor of desert riparian trees is important for their conservation and management. I used multiple regression to assess effects of streamflow and climate (12–14 years of data) or climate alone (up to 60 years of data) on radial growth of clonal narrowleaf cottonwood (Populus angustifolia), a foundation species in the arid, Closed Basin portion of the San Luis Valley, Colorado. I collected increment cores from trees (14–90 cm DBH) at four sites along each of Sand and Deadman creeks (total N = 85), including both perennial and ephemeral reaches. Analyses on trees <110 m from the stream channel explained 33–64% of the variation in standardized growth index (SGI) over the period having discharge measurements. Only 3 of 7 models included a streamflow variable; inclusion of prior-year conditions was common. Models for trees farther from the channel or over a deep water table explained 23–71% of SGI variability, and 4 of 5 contained a streamflow variable. Analyses using solely climate variables over longer time periods explained 17–85% of SGI variability, and 10 of 12 included a variable indexing summer precipitation. Three large, abrupt shifts in recent decades from wet to dry conditions (indexed by a seasonal Palmer Drought Severity Index) coincided with dramatically reduced radial growth. Each shift was presumably associated with branch dieback that produced a legacy effect apparent in many SGI series: uncharacteristically low SGI in the year following the shift. My results suggest trees in locations distant from the active channel rely on the regional shallow unconfined aquifer, summer rainfall, or both to meet water demands. The landscape-level differences in the water supplies sustaining these trees imply variable effects from shifts in winter-versus monsoon-related precipitation, and from climate change versus streamflow or groundwater management.

The annual cycles of phytoplankton biomass

USGS Publications Warehouse

Winder, M.; Cloern, J.E.

2010-01-01

Terrestrial plants are powerful climate sentinels because their annual cycles of growth, reproduction and senescence are finely tuned to the annual climate cycle having a period of one year. Consistency in the seasonal phasing of terrestrial plant activity provides a relatively low-noise background from which phenological shifts can be detected and attributed to climate change. Here, we ask whether phytoplankton biomass also fluctuates over a consistent annual cycle in lake, estuarine-coastal and ocean ecosystems and whether there is a characteristic phenology of phytoplankton as a consistent phase and amplitude of variability. We compiled 125 time series of phytoplankton biomass (chloro-phyll a concentration) from temperate and subtropical zones and used wavelet analysis to extract their dominant periods of variability and the recurrence strength at those periods. Fewer than half (48%) of the series had a dominant 12-month period of variability, commonly expressed as the canonical spring-bloom pattern. About 20 per cent had a dominant six-month period of variability, commonly expressed as the spring and autumn or winter and summer blooms of temperate lakes and oceans. These annual patterns varied in recurrence strength across sites, and did not persist over the full series duration at some sites. About a third of the series had no component of variability at either the six-or 12-month period, reflecting a series of irregular pulses of biomass. These findings show that there is high variability of annual phytoplankton cycles across ecosystems, and that climate-driven annual cycles can be obscured by other drivers of population variability, including human disturbance, aperiodic weather events and strong trophic coupling between phytoplankton and their consumers. Regulation of phytoplankton biomass by multiple processes operating at multiple time scales adds complexity to the challenge of detecting climate-driven trends in aquatic ecosystems where the noise to signal ratio is high. ?? 2010 The Royal Society.

Downscaled Climate Change Projections for the Southern Colorado Plateau: Variability and Implications for Vegetation Changes

NASA Astrophysics Data System (ADS)

Garfin, G. M.; Eischeid, J. K.; Cole, K. L.; Ironside, K.; Cobb, N. S.

2008-12-01

Recent and rapid forest mortality in western North America and associated changes in fire frequency and area burned are among the chief concerns of ecosystem managers. These examples of climate change surprises demonstrate nonlinear and threshold ecosystem responses to increased temperatures and severe drought. A consistent management request from climate change adaptation workshops held during the last four years in the southwest U.S. is for region-specific estimates of climate and vegetation change, in order to provide guidance for management of federal and state forest, range, and riparian preserves and land holdings. Partly in response to these concerns, and partly in the interest of improving knowledge of potential ecosystem changes and their relationships with observed changes and changes demonstrated in the paleoecological record, we developed a set of integrated climate and ecosystem analyses. We selected five of twenty-two GCMs from the PCMDI archive of IPCC AR4 model runs, based on their approximations of observed critical seasonality for vegetation in the Southern Colorado Plateau (domain: 35°- 38°N, 114°-107°W), centered on the Four Corners states. We used three key seasons in our analysis, winter (November-March), pre-monsoon (May-June), and monsoon (July- September). Projections of monthly and seasonal temperature and precipitation from our five-model ensemble indicate steadily increasing temperatures in our region of interest during the twenty-first century. By 2050, the ensemble projects increases of 3.0°C during May and June, months critical for drought stress and tree mortality, and 4.5-5.0°C by 2090. Projected temperature changes for months during the heart of winter (December and January) are on the order of 2.5°C by 2050 and 3.0°C by 2090; such changes are likely to affect snow hydrology in middle to low elevations in the Southern Colorado Plateau. Summer temperature increases are on the order of 2.5°C (2050) and 4.0°C (2090). The most striking aspect of projections of future precipitation is steadily decreasing May-June precipitation during the twenty-first century. Though absolute precipitation during this season is small, declining moisture during the arid pre-monsoon will likely decrease soil moisture, and increase drought stress - consequently, increasing vegetation susceptibility the insect outbreaks and disease. Summer precipitation projections show considerable multi-decade variability, but no substantial trends. Winter precipitation shows little interannual variability and no strong trends. By 2090, annual precipitation is projected to decline by 1-5% across much of the region, with greater declines in the southern part of the domain and increases of 1-5% in the northwestern and northeastern parts of the domain. As part of a National Institute for Climate Change Research project, these projected changes will be input into a USDA-FS vegetation response model, in order to estimate species-specific responses to projected climate changes. We expect increasing temperatures, declining annual precipitation, and extreme declines in pre-monsoon season precipitation to generate significant redistribution of some plant species in the Southern Colorado Plateau.

Fossil palm beetles refine upland winter temperatures in the Early Eocene Climatic Optimum

PubMed Central

Archibald, S. Bruce; Morse, Geoffrey E.; Greenwood, David R.; Mathewes, Rolf W.

2014-01-01

Eocene climate and associated biotic patterns provide an analog system to understand their modern interactions. The relationship between mean annual temperatures and winter temperatures—temperature seasonality—may be an important factor in this dynamic. Fossils of frost-intolerant palms imply low Eocene temperature seasonality into high latitudes, constraining average winter temperatures there to >8 °C. However, their presence in a paleocommunity may be obscured by taphonomic and identification factors for macrofossils and pollen. We circumvented these problems by establishing the presence of obligate palm-feeding beetles (Chrysomelidae: Pachymerina) at three localities (a fourth, tentatively) in microthermal to lower mesothermal Early Eocene upland communities in Washington and British Columbia. This provides support for warmer winter Eocene climates extending northward into cooler Canadian uplands. PMID:24821798

Fossil palm beetles refine upland winter temperatures in the Early Eocene Climatic Optimum.

PubMed

Archibald, S Bruce; Morse, Geoffrey E; Greenwood, David R; Mathewes, Rolf W

2014-06-03

Eocene climate and associated biotic patterns provide an analog system to understand their modern interactions. The relationship between mean annual temperatures and winter temperatures-temperature seasonality-may be an important factor in this dynamic. Fossils of frost-intolerant palms imply low Eocene temperature seasonality into high latitudes, constraining average winter temperatures there to >8 °C. However, their presence in a paleocommunity may be obscured by taphonomic and identification factors for macrofossils and pollen. We circumvented these problems by establishing the presence of obligate palm-feeding beetles (Chrysomelidae: Pachymerina) at three localities (a fourth, tentatively) in microthermal to lower mesothermal Early Eocene upland communities in Washington and British Columbia. This provides support for warmer winter Eocene climates extending northward into cooler Canadian uplands.

Mechanisms Governing Interannual Variability of Stratosphere-to-Troposphere Ozone Transport

NASA Astrophysics Data System (ADS)

Albers, John R.; Perlwitz, Judith; Butler, Amy H.; Birner, Thomas; Kiladis, George N.; Lawrence, Zachary D.; Manney, Gloria L.; Langford, Andrew O.; Dias, Juliana

2018-01-01

Factors governing the strength and frequency of stratospheric ozone intrusions over the Pacific-North American region are considered for their role in modulating tropospheric ozone on interannual timescales. The strength of the association between two major modes of climate variability—the El Niño-Southern Oscillation (ENSO) and the Northern Annular Mode (NAM)—and the amount of ozone contained in stratospheric intrusions are tested in the context of two mechanisms that modulate stratosphere-to-troposphere transport (STT) of ozone: (StratVarO3) the winter season buildup of ozone abundances in the lowermost stratosphere (LMS) and (JetVar) Pacific jet and wave breaking variability during spring. In essence, StratVarO3 corresponds to variability in the amount of ozone per intrusion, while JetVar governs the frequency of intrusions. The resulting analysis, based on two different reanalysis products, suggests that StratVarO3 is more important than JetVar for driving interannual variations in STT of ozone over the Pacific-North American region. In particular, the abundance of ozone in the LMS at the end of winter is shown to be a robust indicator of the amount of ozone that will be contained in stratospheric intrusions during the ensuing spring. Additionally, it is shown that the overall strength of the winter season stratospheric NAM is a useful predictor of ozone intrusion strength. The results also suggest a nuanced relationship between the phase of ENSO and STT of ozone. While ENSO-related jet variability is associated with STT variability, it is wave breaking frequency rather than typical ENSO teleconnection patterns that is responsible for the ENSO-STT relationship.

Climate perceptions of local communities validated through scientific signals in Sikkim Himalaya, India.

PubMed

Sharma, R K; Shrestha, D G

2016-10-01

Sikkim, a tiny Himalayan state situated in the north-eastern region of India, records limited research on the climate change. Understanding the changes in climate based on the perceptions of local communities can provide important insights for the preparedness against the unprecedented consequences of climate change. A total of 228 households in 12 different villages of Sikkim, India, were interviewed using eight climate change indicators. The results from the public opinions showed a significant increase in temperature compared to a decade earlier, winters are getting warmer, water springs are drying up, change in concept of spring-water recharge (locally known as Mul Phutnu), changes in spring season, low crop yields, incidences of mosquitoes during winter, and decrease in rainfall in last 10 years. In addition, study also showed significant positive correlations of increase in temperature with other climate change indicators viz. spring-water recharge concept (R (2) = 0.893), warmer winter (R (2) = 0.839), drying up of water springs (R (2) = 0.76), changes in spring season (R (2) = 0.68), low crop yields (R (2) = 0.68), decrease in rainfall (R (2) = 0.63), and incidences of mosquitoes in winter (R (2) = 0.50). The air temperature for two meteorological stations of Sikkim indicated statistically significant increasing trend in mean minimum temperature and mean minimum winter temperature (DJF). The observed climate change is consistent with the people perceptions. This information can help in planning specific adaptation strategies to cope with the impacts of climate change by framing village-level action plan.

Assessing bio-economic impacts and climate adaptation potential in Flanders

NASA Astrophysics Data System (ADS)

Gobin, A.

2009-04-01

According to Global Circulation Model predictions, Belgium is situated on a wedge between a wetter and drier climatic regime. Observed changes show an increase of 1.3°C during the past decade, a higher frequency of warm summer days and a 6% increase in rainfall with a pronounced rise in winter precipitation of about 25% as compared to the normal (1961-1990). Since agriculture is particularly sensitive to climate variability and occupies more than 61% of the land surface in Flanders, the rural landscape will be confronted with profound changes. A combination of climate scenarios, production models and economic evaluation was used to assess climate impacts on agricultural goods & services, adaptation costs due to production losses and adaptation options. Agro-ecosystems offer a wide range of productive, supporting, regulating and cultural services to society. Productive services relate to crop, animal and energy production, but will alter with climate change. Supporting services such as biodiversity, soil and water quality will be negatively affected by a higher climate variability, increasing erosion and sediment transport, enhancing the breakdown of soil organic matter, lowering soil quality and increasing runoff or leaching of agri-chemicals. The effect of a warmer climate on regulating services is an intensification of most nutrient cycles with increased emissions, which may be compensated for by carbon storage in faster and longer growing crops. The need for flooding areas may result in a net-reduction of the agricultural area. A higher probability of dry weather during summer time and a longer growing season may enlarge the attraction of recreating in rural areas. Knowledge on the interaction of agro-ecosystem services and climate change is required to formulate sustainable adaptation measures. Heat stress and water shortages lead to reduced crop growth, whereas increased CO2-concentrations and a prolonged growing season have a positive effect on crop yields. The interaction between these effects depends on the crop type. The impact on crop production was simulated with a dynamic vegetation model for eight crops (winter wheat, potatoes, sugar beet, fodder maize, grass, grain maize, cauliflower spring, cauliflower autumn), three soil types (loamy sand, loam, clay) and four climatic data series (historic and three cc-scenarios). The three climate change scenarios were selected on the basis of multi-criteria analysis of the PRUDENCE RCM runs. In total 3480 year simulations were executed with a daily modelling step. Pronounced yield losses mainly due to water shortages and heat stress occur for all climate change scenario's, to a lesser extent in the case of winter and spring crops. Yield losses of up to 30% are simulated for sugar beet, whereas winter wheat losses are only 6 % on loamy sand. High critical temperatures lead to heat stress, decreased fodder uptake, outbreaks of diseases and ultimately to animal production losses. Changes in animal production were calculated with a threshold model, whereby a daily maximum temperature of 30°C was taken as the production limit. Calculated animal production losses are up to 9 % for sheep, 8 % for cattle, 6 % for pigs and 3% for poultry. An economic prognosis of the technical productivity, the price effect, the required agricultural area and number of animals was used to estimate the potential productivity for 16 agricultural activities. The impact of climate change was included through aggregating the modelled production losses for Flanders and assuming the agricultural area, the number of animals and the prices constant to the economic prognosis. The total financial impacts are 0.1 % or 6.6 million euro for the first scenario, 1.5% or 71 million euro for the second scenario and 4.1% or 201 million euro for the third scenario. The results represent the acceptable cost of adaptation measures to maintain current efficiencies and production levels. Three gradations of adaptation were defined as different adoption rates. In total 22 adaptation measures were identified. Measures for crop production include cultivation techniques, prevention of pests and diseases, and sustainable use of genetic resources. Measures for animal production relate to stables, feed composition, selection of breeds and prevention of diseases. Measures for agro-ecosystem services other than production concern the sustainable use of natural resources and the quality of the environment and overall community support. The extent of adaptation depends on the farm's economic buoyancy, its vulnerability and the severity of climate variability. Climate change issues therefore have to be integrated in agricultural policy by means of instruments that allow for refined insurance against natural hazards, sustainable management of natural resources, sustaining agro-ecosystem services, supporting sustainable measures and combating vulnerability through adapting infrastructure. This requires sufficient technical and institutional capacity to develop timely information systems.

North Pacific Westerly Jet Influence of the Winter Hawaii Rainfall in the last 21,000 years

NASA Astrophysics Data System (ADS)

Li, S.; Elison Timm, O.

2017-12-01

Hawaii rainfall has a strong seasonality which has more rainfall during the winter than summer. Part of the winter rainfall is from extratropical weather disturbances. Kona lows (KL) are important contributors to the annual rainfall budget of the Hawaiian Islands. KL activity is found to have a strong relationship with the North Pacific climate variability. The goal of the research is to test the hypothesis that changes in the strength and position of the upper level zonal wind jet is a key driver for regional rainfall changes. The main objectives are (1) to identify the relationship between North Pacific westerly jet strength and KL activity in present day climate, (2) to test the stability of this relationship under past climatic conditions, and (3) to explore the teleconnection between Hawaii and North America. For the present-day analysis of the westerly jet, the zonal wind at 250hPa is used from ERA-interim data from 1979-2014. The potential vorticity is used as a measure of extratropical synoptic activity. The Hawaii Rainfall Index is from the Rainfall Atlas of Hawaii (seasonal means, 1920-2012). For the paleoclimatic study, the transient TraCE-21ka simulation is used for the zonal wind - Hawaii rainfall analysis. The results of present-day analysis show that when the jet extends farther into the eastern Pacific sector the Kona Low activity is reduced, less winter rainfall is observed over Hawaii and more rainfall over the California region. The jet position-rainfall relationship was investigated within the TrACE-21 simulation. For the TraCE-21ka dataset, there is an increasing rainfall trend from 21kBP to 14kBP; this period coincides with a gradual decrease in the strength of the westerly wind jet. The results show that the westerly jet strength has a strong influence of the Kona Low activity and the rainfall over Hawaii both in the present and the past.

Drought and immunity determine the intensity of West Nile virus epidemics and climate change impacts

DOE PAGES

Paull, Sara H.; Horton, Daniel E.; Ashfaq, Moetasim; ...

2017-02-08

The effect of global climate change on infectious disease remains hotly debated because multiple extrinsic and intrinsic drivers interact to influence transmission dynamics in nonlinear ways. The dominant drivers of widespread pathogens, like West Nile virus, can be challenging to identify due to regional variability in vector and host ecology, with past studies producing disparate findings. Here, we used analyses at national and state scales to examine a suite of climatic and intrinsic drivers of continental-scale West Nile virus epidemics, including an empirically derived mechanistic relationship between temperature and transmission potential that accounts for spatial variability in vectors. We foundmore » that drought was the primary climatic driver of increased West Nile virus epidemics, rather than within-season or winter temperatures, or precipitation independently. Local-scale data from one region suggested drought increased epidemics via changes in mosquito infection prevalence rather than mosquito abundance. In addition, human acquired immunity following regional epidemics limited subsequent transmission in many states. We show that over the next 30 years, increased drought severity from climate change could triple West Nile virus cases, but only in regions with low human immunity. Lastly, these results illustrate how changes in drought severity can alter the transmission dynamics of vector-borne diseases.« less

Drought and immunity determine the intensity of West Nile virus epidemics and climate change impacts

PubMed Central

Horton, Daniel E.; Ashfaq, Moetasim; Rastogi, Deeksha; Kramer, Laura D.; Diffenbaugh, Noah S.

2017-01-01

The effect of global climate change on infectious disease remains hotly debated because multiple extrinsic and intrinsic drivers interact to influence transmission dynamics in nonlinear ways. The dominant drivers of widespread pathogens, like West Nile virus, can be challenging to identify due to regional variability in vector and host ecology, with past studies producing disparate findings. Here, we used analyses at national and state scales to examine a suite of climatic and intrinsic drivers of continental-scale West Nile virus epidemics, including an empirically derived mechanistic relationship between temperature and transmission potential that accounts for spatial variability in vectors. We found that drought was the primary climatic driver of increased West Nile virus epidemics, rather than within-season or winter temperatures, or precipitation independently. Local-scale data from one region suggested drought increased epidemics via changes in mosquito infection prevalence rather than mosquito abundance. In addition, human acquired immunity following regional epidemics limited subsequent transmission in many states. We show that over the next 30 years, increased drought severity from climate change could triple West Nile virus cases, but only in regions with low human immunity. These results illustrate how changes in drought severity can alter the transmission dynamics of vector-borne diseases. PMID:28179512

Impact of Spatial Soil and Climate Input Data Aggregation on Regional Yield Simulations

PubMed Central

Hoffmann, Holger; Zhao, Gang; Asseng, Senthold; Bindi, Marco; Biernath, Christian; Constantin, Julie; Coucheney, Elsa; Dechow, Rene; Doro, Luca; Eckersten, Henrik; Gaiser, Thomas; Grosz, Balázs; Heinlein, Florian; Kassie, Belay T.; Kersebaum, Kurt-Christian; Klein, Christian; Kuhnert, Matthias; Lewan, Elisabet; Moriondo, Marco; Nendel, Claas; Priesack, Eckart; Raynal, Helene; Roggero, Pier P.; Rötter, Reimund P.; Siebert, Stefan; Specka, Xenia; Tao, Fulu; Teixeira, Edmar; Trombi, Giacomo; Wallach, Daniel; Weihermüller, Lutz; Yeluripati, Jagadeesh; Ewert, Frank

2016-01-01

We show the error in water-limited yields simulated by crop models which is associated with spatially aggregated soil and climate input data. Crop simulations at large scales (regional, national, continental) frequently use input data of low resolution. Therefore, climate and soil data are often generated via averaging and sampling by area majority. This may bias simulated yields at large scales, varying largely across models. Thus, we evaluated the error associated with spatially aggregated soil and climate data for 14 crop models. Yields of winter wheat and silage maize were simulated under water-limited production conditions. We calculated this error from crop yields simulated at spatial resolutions from 1 to 100 km for the state of North Rhine-Westphalia, Germany. Most models showed yields biased by <15% when aggregating only soil data. The relative mean absolute error (rMAE) of most models using aggregated soil data was in the range or larger than the inter-annual or inter-model variability in yields. This error increased further when both climate and soil data were aggregated. Distinct error patterns indicate that the rMAE may be estimated from few soil variables. Illustrating the range of these aggregation effects across models, this study is a first step towards an ex-ante assessment of aggregation errors in large-scale simulations. PMID:27055028

Drought and immunity determine the intensity of West Nile virus epidemics and climate change impacts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paull, Sara H.; Horton, Daniel E.; Ashfaq, Moetasim

The effect of global climate change on infectious disease remains hotly debated because multiple extrinsic and intrinsic drivers interact to influence transmission dynamics in nonlinear ways. The dominant drivers of widespread pathogens, like West Nile virus, can be challenging to identify due to regional variability in vector and host ecology, with past studies producing disparate findings. Here, we used analyses at national and state scales to examine a suite of climatic and intrinsic drivers of continental-scale West Nile virus epidemics, including an empirically derived mechanistic relationship between temperature and transmission potential that accounts for spatial variability in vectors. We foundmore » that drought was the primary climatic driver of increased West Nile virus epidemics, rather than within-season or winter temperatures, or precipitation independently. Local-scale data from one region suggested drought increased epidemics via changes in mosquito infection prevalence rather than mosquito abundance. In addition, human acquired immunity following regional epidemics limited subsequent transmission in many states. We show that over the next 30 years, increased drought severity from climate change could triple West Nile virus cases, but only in regions with low human immunity. Lastly, these results illustrate how changes in drought severity can alter the transmission dynamics of vector-borne diseases.« less

Impact of Spatial Soil and Climate Input Data Aggregation on Regional Yield Simulations.

PubMed

Hoffmann, Holger; Zhao, Gang; Asseng, Senthold; Bindi, Marco; Biernath, Christian; Constantin, Julie; Coucheney, Elsa; Dechow, Rene; Doro, Luca; Eckersten, Henrik; Gaiser, Thomas; Grosz, Balázs; Heinlein, Florian; Kassie, Belay T; Kersebaum, Kurt-Christian; Klein, Christian; Kuhnert, Matthias; Lewan, Elisabet; Moriondo, Marco; Nendel, Claas; Priesack, Eckart; Raynal, Helene; Roggero, Pier P; Rötter, Reimund P; Siebert, Stefan; Specka, Xenia; Tao, Fulu; Teixeira, Edmar; Trombi, Giacomo; Wallach, Daniel; Weihermüller, Lutz; Yeluripati, Jagadeesh; Ewert, Frank

2016-01-01

We show the error in water-limited yields simulated by crop models which is associated with spatially aggregated soil and climate input data. Crop simulations at large scales (regional, national, continental) frequently use input data of low resolution. Therefore, climate and soil data are often generated via averaging and sampling by area majority. This may bias simulated yields at large scales, varying largely across models. Thus, we evaluated the error associated with spatially aggregated soil and climate data for 14 crop models. Yields of winter wheat and silage maize were simulated under water-limited production conditions. We calculated this error from crop yields simulated at spatial resolutions from 1 to 100 km for the state of North Rhine-Westphalia, Germany. Most models showed yields biased by <15% when aggregating only soil data. The relative mean absolute error (rMAE) of most models using aggregated soil data was in the range or larger than the inter-annual or inter-model variability in yields. This error increased further when both climate and soil data were aggregated. Distinct error patterns indicate that the rMAE may be estimated from few soil variables. Illustrating the range of these aggregation effects across models, this study is a first step towards an ex-ante assessment of aggregation errors in large-scale simulations.

Realized niche width of a brackish water submerged aquatic vegetation under current environmental conditions and projected influences of climate change.

PubMed

Kotta, Jonne; Möller, Tiia; Orav-Kotta, Helen; Pärnoja, Merli

2014-12-01

Little is known about how organisms might respond to multiple climate stressors and this lack of knowledge limits our ability to manage coastal ecosystems under contemporary climate change. Ecological models provide managers and decision makers with greater certainty that the systems affected by their decisions are accurately represented. In this study Boosted Regression Trees modelling was used to relate the cover of submerged aquatic vegetation to the abiotic environment in the brackish Baltic Sea. The analyses showed that the majority of the studied submerged aquatic species are most sensitive to changes in water temperature, current velocity and winter ice scour. Surprisingly, water salinity, turbidity and eutrophication have little impact on the distributional pattern of the studied biota. Both small and large scale environmental variability contributes to the variability of submerged aquatic vegetation. When modelling species distribution under the projected influences of climate change, all of the studied submerged aquatic species appear to be very resilient to a broad range of environmental perturbation and biomass gains are expected when seawater temperature increases. This is mainly because vegetation develops faster in spring and has a longer growing season under the projected climate change scenario. Copyright © 2014 Elsevier Ltd. All rights reserved.

Drought and immunity determine the intensity of West Nile virus epidemics and climate change impacts.

PubMed

Paull, Sara H; Horton, Daniel E; Ashfaq, Moetasim; Rastogi, Deeksha; Kramer, Laura D; Diffenbaugh, Noah S; Kilpatrick, A Marm

2017-02-08

The effect of global climate change on infectious disease remains hotly debated because multiple extrinsic and intrinsic drivers interact to influence transmission dynamics in nonlinear ways. The dominant drivers of widespread pathogens, like West Nile virus, can be challenging to identify due to regional variability in vector and host ecology, with past studies producing disparate findings. Here, we used analyses at national and state scales to examine a suite of climatic and intrinsic drivers of continental-scale West Nile virus epidemics, including an empirically derived mechanistic relationship between temperature and transmission potential that accounts for spatial variability in vectors. We found that drought was the primary climatic driver of increased West Nile virus epidemics, rather than within-season or winter temperatures, or precipitation independently. Local-scale data from one region suggested drought increased epidemics via changes in mosquito infection prevalence rather than mosquito abundance. In addition, human acquired immunity following regional epidemics limited subsequent transmission in many states. We show that over the next 30 years, increased drought severity from climate change could triple West Nile virus cases, but only in regions with low human immunity. These results illustrate how changes in drought severity can alter the transmission dynamics of vector-borne diseases. © 2017 The Author(s).

Streamflow changes in the Sierra Nevada, California, simulated using a statistically downscaled general circulation model scenario of climate change

USGS Publications Warehouse

Wilby, Robert L.; Dettinger, Michael D.

2000-01-01

Simulations of future climate using general circulation models (GCMs) suggest that rising concentrations of greenhouse gases may have significant consequences for the global climate. Of less certainty is the extent to which regional scale (i.e., sub-GCM grid) environmental processes will be affected. In this chapter, a range of downscaling techniques are critiqued. Then a relatively simple (yet robust) statistical downscaling technique and its use in the modelling of future runoff scenarios for three river basins in the Sierra Nevada, California, is described. This region was selected because GCM experiments driven by combined greenhouse-gas and sulphate-aerosol forcings consistently show major changes in the hydro-climate of the southwest United States by the end of the 21st century. The regression-based downscaling method was used to simulate daily rainfall and temperature series for streamflow modelling in three Californian river basins under current-and future-climate conditions. The downscaling involved just three predictor variables (specific humidity, zonal velocity component of airflow, and 500 hPa geopotential heights) supplied by the U.K. Meteorological Office couple ocean-atmosphere model (HadCM2) for the grid point nearest the target basins. When evaluated using independent data, the model showed reasonable skill at reproducing observed area-average precipitation, temperature, and concomitant streamflow variations. Overall, the downscaled data resulted in slight underestimates of mean annual streamflow due to underestimates of precipitation in spring and positive temperature biases in winter. Differences in the skill of simulated streamflows amongst the three basins were attributed to the smoothing effects of snowpack on streamflow responses to climate forcing. The Merced and American River basins drain the western, windward slope of the Sierra Nevada and are snowmelt dominated, whereas the Carson River drains the eastern, leeward slope and is a mix of rainfall runoff and snowmelt runoff. Simulated streamflow in the American River responds rapidly and sensitively to daily-scale temperature and precipitation fluctuations and errors; in the Merced and Carson Rivers, the response to the same short-term influences is much less. Consequently, the skill of simulated flows was significantly lower in the American River model than in the Carson and Merced. The physiography of the three basins also accounts for differences in their sensitivities to future climate change. Increases in winter precipitation exceeding +100% coupled with mean temperature rises greater than +2°C result in increased winter streamflows in all three basins. In the Merced and Carson basins, these streamflow increases reflect large changes in winter snowpack, whereas the streamflow changes in the lower elevation American basin are driven primarily by rainfall runoff. Furthermore, reductions in winter snowpack in the American River basin, owing to less precipitation falling as snow and earlier melting of snow at middle elevations, lead to less spring and summer streamflow. Taken collectively, the downscaling results suggest significant changes to both the timing and magnitude of streamflows in the Sierra Nevada by the end of the 21st Century. In the higher elevation basins, the HadCM2 scenario implies more annual streamflow and more streamflow during the spring and summer months that are critical for water-resources management in California. Depending on the relative significance of rainfall runoff and snowmelt, each basin responds in its own way to regional climate forcing. Generally, then, climate scenarios need to be specified — by whatever means — with sufficient temporal and spatial resolution to capture subtle orographic influences if projections of climate-change responses are to be useful and reproducible.