Multiple climate regimes in an idealized lake-ice-atmosphere model

NASA Astrophysics Data System (ADS)

Sugiyama, Noriyuki; Kravtsov, Sergey; Roebber, Paul

2018-01-01

In recent decades, the Laurentian Great Lakes have undergone rapid surface warming with the summertime trends substantially exceeding the warming rates of surrounding land. Warming of the deepest (Lake Superior) was the strongest, and that of the shallowest (Lake Erie)—the weakest of all lakes. To investigate the dynamics of accelerated lake warming, we considered single-column and multi-column thermodynamic lake-ice models coupled to an idealized two-layer atmosphere. The variable temperature of the upper atmospheric layer—a proxy for the large-scale atmospheric forcing—consisted, in the most general case, of a linear trend mimicking the global warming and atmospheric interannual variability, both on top of the prescribed seasonal cycle of the upper-air temperature. The atmospheric boundary layer of the coupled model exchanged heat with the lake and exhibited lateral diffusive heat transports between the adjacent atmospheric columns. In simpler single-column models, we find that, for a certain range of periodic atmospheric forcing, each lake possesses two stable equilibrium seasonal cycles, which we call "regimes"—with and without lake-ice occurrence in winter and with corresponding cold and warm temperatures in the following summer, respectively, all under an identical seasonally varying external forcing. Deeper lakes exhibit larger differences in their summertime surface water temperature between the warm and cold regimes, due to their larger thermal and dynamical inertia. The regime behavior of multi-column coupled models is similar but more complex, and in some cases, they admit more than two stable equilibrium seasonal cycles, with varying degrees of wintertime ice-cover. The simulated lake response to climate change in the presence of the atmospheric noise rationalizes the observed accelerated warming of the lakes, the correlation between wintertime ice cover and next summer's lake-surface temperature, as well as higher warming trends of the (occasionally wintertime ice-covered) deep-lake vs. shallow-lake regions, in terms of the corresponding characteristics of the forced transitions between colder and warmer lake regimes. Since the regime behavior in our models arises due to nonlinear dynamics rooted in the ice-albedo feedback, this feedback is also the root cause of the accelerated lake warming simulated by these models. In addition, our results imply that if Lake Superior eventually becomes largely ice-free (<10% maximum ice cover every winter) under continuing global warming, the surface warming trends of the deeper regions of the lake will become modest, similar to those of the shallower regions of the lake.

Interannual variability of March snow mass over Northern Eurasia and its relation to the concurrent and preceding surface air temperature, precipitation and atmospheric circulation

NASA Astrophysics Data System (ADS)

Ye, Kunhui

2018-06-01

The interannual variability of March snow water equivalent (SWE) in Northern Eurasia and its influencing factors are studied. The surface air temperature (SAT) and precipitation are the dominant factors for the snow accumulation in northern Europe and the remaining region, respectively. The strongest contribution of SAT to snow accumulation is mainly found in those months with moderate mean SAT. The strongest contribution of precipitation is not collocated with the climatological maxima in precipitation. The leading mode of March SWE variability is obtained and characterized by a spatial dipole. Anomalies in atmospheric water vapor divergence, storm activity and the associated atmospheric circulation can explain many of the associated precipitation and SAT features. Anomalies in autumn Arctic sea ice concentration (SIC) over the Barents Sea and Kara Sea (B/K Sea) and a dipole pattern of November snow cover (SC) in Eurasia are also observed. The atmospheric circulation anomalies that resemble a negative phase of North Atlantic Oscillation (NAO)/Arctic Oscillation (AO) are strongly projected onto the wintertime atmospheric circulation. Both observations and model experiment support that the autumn B/K Sea SIC has some impacts on the autumn and AO/NAO-like wintertime atmospheric circulation patterns. The dipole pattern of November Eurasian SC seems to be strongly forced by the autumn B/K Sea SIC and its feedback to the atmospheric circulation is important. Therefore, the impacts of autumn B/K Sea SIC on the autumn/wintertime atmospheric circulation and thus the March SWE variability may be modulated by both constructive and destructive interference of autumn Eurasian SC.

The Regional Influence of the Arctic Oscillation and Arctic Dipole on the Wintertime Arctic Surface Radiation Budget and Sea Ice Growth

NASA Technical Reports Server (NTRS)

Hegyi, Bradley M.; Taylor, Patrick C.

2017-01-01

An analysis of 2000-2015 monthly Clouds and the Earth's Radiant Energy System-Energy Balanced and Filled (CERES-EBAF) and Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA2) data reveals statistically significant fall and wintertime relationships between Arctic surface longwave (LW) radiative flux anomalies and the Arctic Oscillation (AO) and Arctic Dipole (AD). Signifying a substantial regional imprint, a negative AD index corresponds with positive downwelling clear-sky LW flux anomalies (greater than10W m(exp -2)) north of western Eurasia (0 deg E-120 deg E) and reduced sea ice growth in the Barents and Kara Seas in November-February. Conversely, a positive AO index coincides with negative clear-sky LW flux anomalies and minimal sea ice growth change in October-November across the Arctic. Increased (decreased) atmospheric temperature and water vapor coincide with the largest positive (negative) clear-sky flux anomalies. Positive surface LW cloud radiative effect anomalies also accompany the negative AD index in December-February. The results highlight a potential pathway by which Arctic atmospheric variability influences the regional surface radiation budget over areas of Arctic sea ice growth.

An isoline separating relatively warm from relatively cool wintertime forest surface temperatures for the southeastern United States

Treesearch

J. Wickham; T.G. Wade; K.H. Riitters

2014-01-01

Forest-oriented climate mitigation policies promote forestation as a means to increase uptake of atmospheric carbon to counteract global warming. Some have pointed out that a carbon-centric forest policy may be overstated because it discounts biophysical aspects of the influence of forests on climate. In extra-tropical regions, many climate models have shown that...

The interdecadal worsening of weather conditions affecting aerosol pollution in the Beijing area in relation to climate warming

NASA Astrophysics Data System (ADS)

Zhang, Xiaoye; Zhong, Junting; Wang, Jizhi; Wang, Yaqiang; Liu, Yanju

2018-04-01

The weather conditions affecting aerosol pollution in Beijing and its vicinity (BIV) in wintertime have worsened in recent years, particularly after 2010. The relation between interdecadal changes in weather conditions and climate warming is uncertain. Here, we analyze long-term variations of an integrated pollution-linked meteorological index (which is approximately and linearly related to aerosol pollution), the extent of changes in vertical temperature differences in the boundary layer (BL) in BIV, and northerly surface winds from Lake Baikal during wintertime to evaluate the potential contribution of climate warming to changes in meteorological conditions directly related to aerosol pollution in this area; this is accomplished using NCEP reanalysis data, surface observations, and long-term vertical balloon sounding observations since 1960. The weather conditions affecting BIV aerosol pollution are found to have worsened since the 1960s as a whole. This worsening is more significant after 2010, with PM2.5 reaching unprecedented high levels in many cities in China, particularly in BIV. The decadal worsening of meteorological conditions in BIV can partly be attributed to climate warming, which is defined by more warming in the higher layers of the boundary layer (BL) than the lower layers. This worsening can also be influenced by the accumulation of aerosol pollution, to a certain extent (particularly after 2010), because the increase in aerosol pollution from the ground leads to surface cooling by aerosol-radiation interactions, which facilitates temperature inversions, increases moisture accumulations, and results in the extra deterioration of meteorological conditions. If analyzed as a linear trend, weather conditions have worsened by ˜ 4 % each year from 2010 to 2017. Given such a deterioration rate, the worsening of weather conditions may lead to a corresponding amplitude increase in PM2.5 in BIV during wintertime in the next 5 years (i.e., 2018 to 2022). More stringent emission reduction measures will need to be conducted by the government.

An Active Englacial Hydrological System in a Cold Glacier: Blood Falls, Taylor Glacier, Antarctica

NASA Astrophysics Data System (ADS)

Carr, C. G.; Pettit, E. C.; Carmichael, J.; Badgeley, J.; Tulaczyk, S. M.; Lyons, W. B.; Mikucki, J.

2016-12-01

Blood Falls is a supraglacial hydrological feature formed by episodic release of iron-rich subglacial brine derived from an extensive aquifer beneath the cold, polar, Taylor Glacier. While fluid transport in non-temperate ice typically occurs through meltwater delivery from the glacier surface to the bed (hydrofracturing, supraglacial lake drainage), Blood Falls represents the opposite situation: brine moves from a subglacial source to the glacier surface. Here, we present the first complete conceptual model for brine transport and release, as well as the first direct evidence of a wintertime brine release at Blood Falls obtained through year-round time-lapse photography. Related analyses show that brine pools subglacially underneath the northern terminus of Taylor Glacier, rather than flowing directly into proglacial Lake Bonney because ice-cored moraines and channelized surface topography provide hydraulic barriers. This pooled brine is pressurized by hydraulic head from the upglacier brine source region. Based on seismic data, we propose that episodic supraglacial release is initiated by high strain rates coupled with pressurized subglacial brine that drive intermittent subglacial and englacial fracturing. Ultimately, brine-filled basal crevasses propagate upward to link with surface crevasses, allowing brine to flow from the bed to the surface. The observation of wintertime brine release indicates that surface-generated meltwater is not necessary to trigger crack propagation or to maintain the conduit as previously suggested. The liquid brine persists beneath and within the cold ice (-17°C) despite ambient ice/brine temperature differences of as high as 10°C through both locally depressed brine freezing temperatures through cryoconcentration of salts and increased ice temperatures through release of latent heat during partial freezing of brine. The existence of an englacial hydrological system initiated by basal crevassing extends to polar glaciers a process thought limited to temperate glaciers and confirms that supraglacial, englacial, and subglacial hydrological systems act in concert to provide critical forcing on glacier dynamics, even in cold polar ice.

Dust-wind interactions can intensify aerosol pollution over eastern China.

PubMed

Yang, Yang; Russell, Lynn M; Lou, Sijia; Liao, Hong; Guo, Jianping; Liu, Ying; Singh, Balwinder; Ghan, Steven J

2017-05-11

Eastern China has experienced severe and persistent winter haze episodes in recent years due to intensification of aerosol pollution. In addition to anthropogenic emissions, the winter aerosol pollution over eastern China is associated with unusual meteorological conditions, including weaker wind speeds. Here we show, based on model simulations, that during years with decreased wind speed, large decreases in dust emissions (29%) moderate the wintertime land-sea surface air temperature difference and further decrease winds by -0.06 (±0.05) m s -1 averaged over eastern China. The dust-induced lower winds enhance stagnation of air and account for about 13% of increasing aerosol concentrations over eastern China. Although recent increases in anthropogenic emissions are the main factor causing haze over eastern China, we conclude that natural emissions also exert a significant influence on the increases in wintertime aerosol concentrations, with important implications that need to be taken into account by air quality studies.

Predicting the Dominant Patterns of Subseasonal Variability of Wintertime Surface Air Temperature in Extratropical Northern Hemisphere

NASA Astrophysics Data System (ADS)

Lin, Hai

2018-05-01

Skillfully predicting persistent extreme temperature anomalies more than 10 days in advance remains a challenge although it is of great value to the society. Here the two leading modes of subseasonal variability of surface air temperature over the extratropical Northern Hemisphere in boreal winter are identified with pentad (5 days) averaged data. They are well separated geographically, dominating temperature variability in North America and Eurasia, respectively. There exists a two-pentad lagged correlation between these two modes, implying an intercontinental link of temperature variability. Forecast skill of these two modes is evaluated based on three operational subseasonal prediction models. The results show that useful forecasts of the Eurasian mode (EOF2) can be achieved four pentads in advance, which is more skillful than the North American mode (EOF1). EOF2 is found to benefit from the Madden-Julian Oscillation signal in the initial condition.

Solar wind: A possible factor driving the interannual sea surface temperature tripolar mode over North Atlantic

NASA Astrophysics Data System (ADS)

Xiao, Ziniu; Li, Delin

2016-06-01

The effect of solar wind (SW) on the North Atlantic sea surface temperature (SST) in boreal winter is examined through an analysis of observational data during 1964-2013. The North Atlantic SSTs show a pronounced meridional tripolar pattern in response to solar wind speed (SWS) variations. This pattern is broadly similar to the leading empirical orthogonal function (EOF) mode of interannual variations in the wintertime SSTs over North Atlantic. The time series of this leading EOF mode of SST shows a significant interannual period, which is the same as that of wintertime SWS. This response also appears as a compact north-south seesaw of sea level pressure and a vertical tripolar structure of zonal wind, which simultaneously resembles the North Atlantic Oscillation (NAO) in the overlying atmosphere. As compared with the typical low SWS winters, during the typical high SWS winters, the stratospheric polar night jet (PNJ) is evidently enhanced and extends from the stratosphere to the troposphere, even down to the North Atlantic Ocean surface. Notably, the North Atlantic Ocean is an exclusive region in which the SW signal spreads downward from the stratosphere to the troposphere. Thus, it seems that the SW is a possible factor for this North Atlantic SST tripolar mode. The dynamical process of stratosphere-troposphere coupling, together with the global atmospheric electric circuit-cloud microphysical process, probably accounts for the particular downward propagation of the SW signal.

Zonal wind indices to reconstruct United States winter precipitation during El Niño

NASA Astrophysics Data System (ADS)

Farnham, D. J.; Steinschneider, S.; Lall, U.

2017-12-01

The highly discussed 2015/16 El Niño event, which many likened to the similarly strong 1997/98 El Niño event, led to precipitation impacts over the continental United States (CONUS) inconsistent with general expectations given past events and model-based forecasts. This presents a challenge for regional water managers and others who use seasonal precipitation forecasts who previously viewed El Niño events as times of enhanced confidence in seasonal water availability and flood risk forecasts. It is therefore useful to understand the extent to which wintertime CONUS precipitation during El Niño events can be explained by seasonal sea surface temperature heating patterns and the extent to which the precipitation is a product of natural variability. In this work, we define two seasonal indices based on the zonal wind field spanning from the eastern Pacific to the western Atlantic over CONUS that can explain El Niño precipitation variation spatially throughout CONUS over 11 historic El Niño events from 1950 to 2016. The indices reconstruct El Niño event wintertime (Jan-Mar) gridded precipitation over CONUS through cross-validated regression much better than the traditional ENSO sea surface temperature indices or other known modes of variability. Lastly, we show strong relationships between sea surface temperature patterns and the phases of the zonal wind indices, which in turn suggests that some of the disparate CONUS precipitation during El Niño events can be explained by different heating patterns. The primary contribution of this work is the identification of intermediate variables (in the form of zonal wind indices) that can facilitate further studies into the distinct hydroclimatic response to specific El Niño events.

The Great Lakes' regional climate regimes

NASA Astrophysics Data System (ADS)

Sugiyama, Noriyuki

For the last couple of decades, the Great Lakes have undergone rapid surface warming. In particular, the magnitude of the summer surface-warming trends of the Great Lakes have been much greater than those of surrounding land (Austin and Colman, 2007). Among the Great Lakes, the deepest Lake Superior exhibited the strongest warming trend in its annual, as well as summer surface water temperature. We find that many aspects of this behavior can be explained in terms of the tendency of deep lakes to exhibit multiple regimes characterized, under the same seasonally varying forcing, by the warmer and colder seasonal cycles exhibiting different amounts of wintertime lake-ice cover and corresponding changes in the summertime lake-surface temperatures. In this thesis, we address the problem of the Great Lakes' warming using one-dimensional lake modeling to interpret diverse observations of the recent lake behavior. (Abstract shortened by ProQuest.).

Challenges in modelling spatiotemporally varying phytoplankton blooms in the Northwestern Arabian Sea and Gulf of Oman

NASA Astrophysics Data System (ADS)

Sedigh Marvasti, S.; Gnanadesikan, A.; Bidokhti, A. A.; Dunne, J. P.; Ghader, S.

2015-07-01

We examine interannual variability of phytoplankton blooms in northwestern Arabian Sea and Gulf of Oman. Satellite data (SeaWIFS ocean color) shows two climatological blooms in this region, a wintertime bloom peaking in February and a summertime bloom peaking in September. A pronounced anti-correlation between the AVISO sea surface height anomaly (SSHA) and chlorophyll is found during the wintertime bloom. On a regional scale, interannual variability of the wintertime bloom is thus dominated by cyclonic eddies which vary in location from one year to another. These results were compared against the outputs from three different 3-D Earth System models. We show that two coarse (1°) models with the relatively complex biogeochemistry (TOPAZ) capture the annual cycle but neither eddies nor the interannual variability. An eddy-resolving model (GFDL CM2.6) with a simpler biogeochemistry (miniBLING) displays larger interannual variability, but overestimates the wintertime bloom and captures eddy-bloom coupling in the south but not in the north. The southern part of the domain is a region with a much sharper thermocline and nutricline relatively close to the surface, in which eddies modulate diffusive nutrient supply to the surface (a mechanism not previously emphasized in the literature). We suggest that for the model to simulate the observed wintertime blooms within cyclones, it will be necessary to represent this relatively unusual nutrient structure as well as the cyclonic eddies. This is a challenge in the Northern Arabian Sea as it requires capturing the details of the outflow from the Persian Gulf.

Enhanced wintertime greenhouse effect reinforcing Arctic amplification and initial sea-ice melting.

PubMed

Cao, Yunfeng; Liang, Shunlin; Chen, Xiaona; He, Tao; Wang, Dongdong; Cheng, Xiao

2017-08-16

The speeds of both Arctic surface warming and sea-ice shrinking have accelerated over recent decades. However, the causes of this unprecedented phenomenon remain unclear and are subjects of considerable debate. In this study, we report strong observational evidence, for the first time from long-term (1984-2014) spatially complete satellite records, that increased cloudiness and atmospheric water vapor in winter and spring have caused an extraordinary downward longwave radiative flux to the ice surface, which may then amplify the Arctic wintertime ice-surface warming. In addition, we also provide observed evidence that it is quite likely the enhancement of the wintertime greenhouse effect caused by water vapor and cloudiness has advanced the time of onset of ice melting in mid-May through inhibiting sea-ice refreezing in the winter and accelerating the pre-melting process in the spring, and in turn triggered the positive sea-ice albedo feedback process and accelerated the sea ice melting in the summer.

Emerging European winter precipitation pattern linked to atmospheric circulation changes over the North Atlantic region in recent decades

NASA Astrophysics Data System (ADS)

Ummenhofer, Caroline C.; Seo, Hyodae; Kwon, Young-Oh; Parfitt, Rhys; Brands, Swen; Joyce, Terrence M.

2017-08-01

Dominant European winter precipitation patterns over the past century, along with their associated extratropical North Atlantic circulation changes, are evaluated using cluster analysis. Contrary to the four regimes traditionally identified based on daily wintertime atmospheric circulation patterns, five distinct seasonal precipitation regimes are detected here. Recurrent precipitation patterns in each regime are linked to changes in atmospheric blocking, storm track, and sea surface temperatures across the North Atlantic region. Multidecadal variability in the frequency of the precipitation patterns reveals more (fewer) winters with wet conditions in northern (southern) Europe in recent decades and an emerging distinct pattern of enhanced wintertime precipitation over the northern British Isles. This pattern has become unusually common since the 1980s and is associated with changes in moisture transport and more frequent atmospheric river events. The observed precipitation changes post-1950 coincide with changes in storm track activity over the central/eastern North Atlantic toward the northern British Isles.

Dust-wind interactions can intensify aerosol pollution over eastern China

PubMed Central

Yang, Yang; Russell, Lynn M.; Lou, Sijia; Liao, Hong; Guo, Jianping; Liu, Ying; Singh, Balwinder; Ghan, Steven J.

2017-01-01

Eastern China has experienced severe and persistent winter haze episodes in recent years due to intensification of aerosol pollution. In addition to anthropogenic emissions, the winter aerosol pollution over eastern China is associated with unusual meteorological conditions, including weaker wind speeds. Here we show, based on model simulations, that during years with decreased wind speed, large decreases in dust emissions (29%) moderate the wintertime land–sea surface air temperature difference and further decrease winds by −0.06 (±0.05) m s−1 averaged over eastern China. The dust-induced lower winds enhance stagnation of air and account for about 13% of increasing aerosol concentrations over eastern China. Although recent increases in anthropogenic emissions are the main factor causing haze over eastern China, we conclude that natural emissions also exert a significant influence on the increases in wintertime aerosol concentrations, with important implications that need to be taken into account by air quality studies. PMID:28492276

Studies on the wintertime current structure and T-S fine-structure in the Taiwan Strait

NASA Astrophysics Data System (ADS)

Hu, Jianyu; Fu, Zilang; Wu, Lianxing

1990-12-01

A cruise through the western sea area of the Taiwan Strait was carried out by the R/V Dong Fang Hong in December, 1987. Eight anchored and 10 not anchored stations were set up. Over 25 time-series current observations were made at each station and CTD (Conductivity-temperature-depth) measurements were made at 5 anchored and 10 not anchored stations. Based on the measured data. fine-structures and step-like vertical structures of temperature and salinity were analysed and a tentative wintertime current structure in the Taiwan Strait was described.

Regional climate impacts of a possible future grand solar minimum.

PubMed

Ineson, Sarah; Maycock, Amanda C; Gray, Lesley J; Scaife, Adam A; Dunstone, Nick J; Harder, Jerald W; Knight, Jeff R; Lockwood, Mike; Manners, James C; Wood, Richard A

2015-06-23

Any reduction in global mean near-surface temperature due to a future decline in solar activity is likely to be a small fraction of projected anthropogenic warming. However, variability in ultraviolet solar irradiance is linked to modulation of the Arctic and North Atlantic Oscillations, suggesting the potential for larger regional surface climate effects. Here, we explore possible impacts through two experiments designed to bracket uncertainty in ultraviolet irradiance in a scenario in which future solar activity decreases to Maunder Minimum-like conditions by 2050. Both experiments show regional structure in the wintertime response, resembling the North Atlantic Oscillation, with enhanced relative cooling over northern Eurasia and the eastern United States. For a high-end decline in solar ultraviolet irradiance, the impact on winter northern European surface temperatures over the late twenty-first century could be a significant fraction of the difference in climate change between plausible AR5 scenarios of greenhouse gas concentrations.

A study of oceanic surface heat fluxes in the Greenland, Norwegian, and Barents Seas

NASA Technical Reports Server (NTRS)

Hakkinen, Sirpa; Cavalieri, Donald J.

1989-01-01

This study examines oceanic surface heat fluxes in the Norwegian, Greenland, and Barents seas using the gridded Navy Fleet Numerical Oceanography Central surface analysis and the First GARP Global Experiment (FGGE) IIc cloudiness data bases. Monthly and annual means of net and turbulent heat fluxes are computed for the FGGE year 1979. The FGGE IIb data base consisting of individual observations provides particularly good data coverage in this region for a comparison with the gridded Navy winds and air temperatures. The standard errors of estimate between the Navy and FGGE IIb winds and air temperatures are 3.6 m/s and 2.5 C, respectively. The computations for the latent and sensible heat fluxes are based on bulk formulas with the same constant heat exchange coefficient of 0.0015. The results show extremely strong wintertime heat fluxes in the northern Greenland Sea and especially in the Barents Sea in contrast to previous studies.

Differences between radiosonde and dropsonde temperature profiles over the Arctic Ocean

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

Skony, S.M.; Kahl, J.D.W.; Zaitseva, N.A.

1994-10-01

The boundary layer structure measured by 402 pairs of approximately collocated radiosonde and dropsonde temperature profiles over the Arctic Ocean during the period 1957-1961 is examined. The radiosonde profiles were obtained at the Russian drifting ice camps `North Pole 7` and `North Pole 8,` and the dropsonde profiles were measured during the United States Air Force `Ptarmigan` series of weather reconnaissance flights. The boundary layer structure is characterized by the features of the low-level tropospheric temperature inversion. The results indicate that the dropsonde soundings, although containing relatively few measurement levels, contain sufficient vertical resolution to characterize the temperature inversion. Systematicmore » differences were noted in wintertime inversion features and near-surface temperatures as measured by dropsondes and radiosondes. These differences are attributed to contrasting temperature lag errors accompanying ascending and descending sensors.« less

NOx Lifetime During WINTER

NASA Astrophysics Data System (ADS)

Kenagy, H. S.; Sparks, T.; Ebben, C. J.; Wooldridge, P. J.; Lopez-Hilfiker, F.; Lee, B. H.; Thornton, J. A.; McDuffie, E. E.; Fibiger, D. L.; Brown, S. S.; Montzka, D. D.; Weinheimer, A. J.; Apel, E. C.; Jaegle, L.; Cohen, R. C.

2017-12-01

The study of the lifetime and fate of NOx (=NO + NO2) is important for understanding its persistence and distribution. This requires an understanding of the balance of NOx sinks. Although urban NOx lifetimes are relatively well understood during summertime conditions, wintertime NOx chemistry has been comparatively less studied. We used measurements of NOx and its oxidation products from the aircraft-based WINTER (Wintertime INvestigation of Transport, Emissions, and Reactivity) campaign over the northeastern US during February-March 2015 to help constrain NOx lifetime during wintertime conditions when days are shorter, actinic flux is reduced, and temperatures are colder. By analyzing the marine outflow from the NYC-DC corridor, we learn that wintertime NOx has a long lifetime, is much longer-lived during the day than at night, and its lifetime is controlled during both periods by NOx conversion to nitric acid (HNO3) as the primary NOx sink. We also employ a two-box model to constrain the wintertime plume dilution rate and HNO3 deposition rate. Additionally, analysis of the nighttime Ox budget suggests that approximately 10% of O3 is lost overnight through N2O5 dark reactions that produce HNO3.

Observational assessment of the role of nocturnal residual-layer chemistry in determining daytime surface particulate nitrate concentrations

NASA Astrophysics Data System (ADS)

Prabhakar, Gouri; Parworth, Caroline L.; Zhang, Xiaolu; Kim, Hwajin; Young, Dominique E.; Beyersdorf, Andreas J.; Ziemba, Luke D.; Nowak, John B.; Bertram, Timothy H.; Faloona, Ian C.; Zhang, Qi; Cappa, Christopher D.

2017-12-01

This study discusses an analysis of combined airborne and ground observations of particulate nitrate (NO3-(p)) concentrations made during the wintertime DISCOVER-AQ (Deriving Information on Surface Conditions from COlumn and VERtically resolved observations relevant to Air Quality) study at one of the most polluted cities in the United States - Fresno, CA - in the San Joaquin Valley (SJV) and focuses on developing an understanding of the various processes that impact surface nitrate concentrations during pollution events. The results provide an explicit case-study illustration of how nighttime chemistry can influence daytime surface-level NO3-(p) concentrations, complementing previous studies in the SJV. The observations exemplify the critical role that nocturnal chemical production of NO3-(p) aloft in the residual layer (RL) can play in determining daytime surface-level NO3-(p) concentrations. Further, they indicate that nocturnal production of NO3-(p) in the RL, along with daytime photochemical production, can contribute substantially to the buildup and sustaining of severe pollution episodes. The exceptionally shallow nocturnal boundary layer (NBL) heights characteristic of wintertime pollution events in the SJV intensify the importance of nocturnal production aloft in the residual layer to daytime surface concentrations. The observations also demonstrate that dynamics within the RL can influence the early-morning vertical distribution of NO3-(p), despite low wintertime wind speeds. This overnight reshaping of the vertical distribution above the city plays an important role in determining the net impact of nocturnal chemical production on local and regional surface-level NO3-(p) concentrations. Entrainment of clean free-tropospheric (FT) air into the boundary layer in the afternoon is identified as an important process that reduces surface-level NO3-(p) and limits buildup during pollution episodes. The influence of dry deposition of HNO3 gas to the surface on daytime particulate nitrate concentrations is important but limited by an excess of ammonia in the region, which leads to only a small fraction of nitrate existing in the gas phase even during the warmer daytime. However, in the late afternoon, when diminishing solar heating leads to a rapid fall in the mixed boundary layer height (BLH), the impact of surface deposition is temporarily enhanced and can lead to a substantial decline in surface-level particulate nitrate concentrations; this enhanced deposition is quickly arrested by a decrease in surface temperature, which drops the gas-phase fraction to near zero. The overall importance of enhanced late-afternoon gas-phase loss to the multiday buildup of pollution events is limited by the very shallow nocturnal boundary layer. The case study here demonstrates that mixing down of NO3-(p) from the RL can contribute a majority of the surface-level NO3-(p) in the morning (here, ˜ 80 %), and a strong influence can persist into the afternoon even when photochemical production is maximum. The particular day-to-day contribution of aloft nocturnal NO3-(p) production to surface concentrations will depend on prevailing chemical and meteorological conditions. Although specific to the SJV, the observations and conceptual framework further developed here provide general insights into the evolution of pollution episodes in wintertime environments.

Gaseous oxygen cooling of the Space Transportation System launch pad environment

NASA Astrophysics Data System (ADS)

Ahmad, R. A.; Mathias, E. C.; Boraas, S.

1991-12-01

The external tank (ET) of the Space Transportation System (STS) contains liquid oxygen and hydrogen as oxidizer and fuel for the Space Shuttle main engines (SSMEs). During and subsequent to the loading of the ET prior to the launch of an STS, the cryogens boil in the near atmospheric conditions existing within their respective tanks. The gaseous oxygen (GOX) formed as a result of this boiling is vented overboard, mixes with air, and may, under certain wind conditions, be transported toward the STS to cause a cooling of its environment. This paper describes a two-dimensional computational fliud dynamics analysis to determine the magnitude of this cooling effect by determining the temperature depression and stratification caused by this GOX/air mixture in the region around the east redesigned solid rocket motor (RSRM), the ET, and below the STS assembly. For a severe wintertime launch temperature of -4.44 C, the maximum local temperature depression of the mixture was calculated to be 32.22 C in the inboard region next to the ET surface, and a surface temperature on the east RSRM was found to be as much as 13.89 C colder than ambient. The computed average surface temperatures on either side of the RSRM were in excellent agreement with a temperature determined from a correlation of prelaunch temperature measurements.

Dust-wind interactions can intensify aerosol pollution over eastern China

DOE PAGES

Yang, Yang; Russell, Lynn M.; Lou, Sijia; ...

2017-05-11

Eastern China has experienced severe and persistent winter haze episodes in recent years due to intensification of aerosol pollution, which has adverse impacts on hundreds of millions of people across China1–4. In addition to anthropogenic emissions, the winter aerosol pollution over eastern China is associated with abnormal meteorological conditions, including weaker wind speeds5–9. Using a global climate model and a chemical transport model, we show that variations in dust emissions decrease the wintertime land-sea surface air temperature difference between eastern China and the South China Sea and weaken winds below the lowest 10th percentile of wind speed by 0.06 mmore » s-1. Here, the weakened winds enhance stagnation and account for 13% of the increases in PM2.5 aerosol concentrations over eastern China. Although recent increases in anthropogenic emissions are the main factor causing haze over eastern China, we conclude that natural emissions also exert a significant influence on the increases in wintertime PM2.5 concentrations, with important implications that should be considered in air quality studies.« less

Dust-wind interactions can intensify aerosol pollution over eastern China

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

Yang, Yang; Russell, Lynn M.; Lou, Sijia

Eastern China has experienced severe and persistent winter haze episodes in recent years due to intensification of aerosol pollution, which has adverse impacts on hundreds of millions of people across China1–4. In addition to anthropogenic emissions, the winter aerosol pollution over eastern China is associated with abnormal meteorological conditions, including weaker wind speeds5–9. Using a global climate model and a chemical transport model, we show that variations in dust emissions decrease the wintertime land-sea surface air temperature difference between eastern China and the South China Sea and weaken winds below the lowest 10th percentile of wind speed by 0.06 mmore » s-1. Here, the weakened winds enhance stagnation and account for 13% of the increases in PM2.5 aerosol concentrations over eastern China. Although recent increases in anthropogenic emissions are the main factor causing haze over eastern China, we conclude that natural emissions also exert a significant influence on the increases in wintertime PM2.5 concentrations, with important implications that should be considered in air quality studies.« less

Wintertime Boundary Layer Structure in the Grand Canyon.

NASA Astrophysics Data System (ADS)

Whiteman, C. David; Zhong, Shiyuan; Bian, Xindi

1999-08-01

Wintertime temperature profiles in the Grand Canyon exhibit a neutral to isothermal stratification during both daytime and nighttime, with only rare instances of actual temperature inversions. The canyon warms during daytime and cools during nighttime more or less uniformly through the canyon's entire depth. This weak stability and temperature structure evolution differ from other Rocky Mountain valleys, which develop strong nocturnal inversions and exhibit convective and stable boundary layers that grow upward from the valley floor. Mechanisms that may be responsible for the different behavior of the Grand Canyon are discussed, including the possibility that the canyon atmosphere is frequently mixed to near-neutral stratification when cold air drains into the top of the canyon from the nearby snow-covered Kaibab Plateau. Another feature of canyon temperature profiles is the sharp inversions that often form near the canyon rims. These are generally produced when warm air is advected over the canyon in advance of passing synoptic-scale ridges.Wintertime winds in the main canyon are not classical diurnal along-valley wind systems. Rather, they are driven along the canyon axis by the horizontal synoptic-scale pressure gradient that is superimposed along the canyon's axis by passing synoptic-scale weather disturbances. They may thus bring winds into the canyon from either end at any time of day.The implications of the observed canyon boundary layer structure for air pollution dispersion are discussed.

Bacterial Activity at −2 to −20°C in Arctic Wintertime Sea Ice

PubMed Central

Junge, Karen; Eicken, Hajo; Deming, Jody W.

2004-01-01

Arctic wintertime sea-ice cores, characterized by a temperature gradient of −2 to −20°C, were investigated to better understand constraints on bacterial abundance, activity, and diversity at subzero temperatures. With the fluorescent stains 4′,6′-diamidino-2-phenylindole 2HCl (DAPI) (for DNA) and 5-cyano-2,3-ditoyl tetrazolium chloride (CTC) (for O2-based respiration), the abundances of total, particle-associated (>3-μm), free-living, and actively respiring bacteria were determined for ice-core samples melted at their in situ temperatures (−2 to −20°C) and at the corresponding salinities of their brine inclusions (38 to 209 ppt). Fluorescence in situ hybridization was applied to determine the proportions of Bacteria, Cytophaga-Flavobacteria-Bacteroides (CFB), and Archaea. Microtome-prepared ice sections also were examined microscopically under in situ conditions to evaluate bacterial abundance (by DAPI staining) and particle associations within the brine-inclusion network of the ice. For both melted and intact ice sections, more than 50% of cells were found to be associated with particles or surfaces (sediment grains, detritus, and ice-crystal boundaries). CTC-active bacteria (0.5 to 4% of the total) and cells detectable by rRNA probes (18 to 86% of the total) were found in all ice samples, including the coldest (−20°C), where virtually all active cells were particle associated. The percentage of active bacteria associated with particles increased with decreasing temperature, as did the percentages of CFB (16 to 82% of Bacteria) and Archaea (0.0 to 3.4% of total cells). These results, combined with correlation analyses between bacterial variables and measures of particulate matter in the ice as well as the increase in CFB at lower temperatures, confirm the importance of particle or surface association to bacterial activity at subzero temperatures. Measuring activity down to −20°C adds to the concept that liquid inclusions in frozen environments provide an adequate habitat for active microbial populations on Earth and possibly elsewhere. PMID:14711687

High Wintertime Ozone in the Uinta Basin: Diurnal Mixing and Ozone Production Measured by Tethered Ozonesondes

NASA Astrophysics Data System (ADS)

Johnson, B.; Cullis, P.; Schnell, R. C.; Oltmans, S. J.; Sterling, C. W.; Jordan, A. F.; Hall, E.

2016-12-01

Extreme high ozone mixing ratios, far exceeding U.S. National Air Quality Standards, were observed in the Uinta Basin in January-February 2013 under conditions highly favorable for wintertime ozone production. Hourly average ozone mixing ratios increased from regional background levels of 40-50 ppbv to >160 ppbv during several multi-day episodes of prolonged temperature inversions over snow-covered ground within air confining topography. Extensive surface and tethered balloon profile measurements of ozone, meteorology, CH4, CO2, NO2 and a suite of non-methane hydrocarbons (NMHCs) link emissions from oil and natural gas extraction with the strong ozone production throughout the Basin. High levels of NMHCs that were well correlated with CH4 showed that abundant O3 precursors were available throughout the Basin where high ozone mixing ratios extended from the surface to the top of the inversion layer at 200 m above ground level. This layer was at a nearly uniform height across the Basin even though there are significant terrain variations. Tethered balloon measurements rising above the elevated levels of ozone within the cold pool layer beneath the inversion measured regional background O3 concentrations. Surface wind and direction data from tethered balloons showed a consistent diurnal pattern in the Basin that moved air with the highest levels of CH4 and ozone precursor NMHC's from the gas fields of the east-central portion of the Basin to the edges during the day, before draining back into the Basin at night.

Beyond Rayleigh Distillation: Reconstructing Glacial Nutrient Cycles using a Seasonal Model of the Southern Ocean

NASA Astrophysics Data System (ADS)

Kemeny, P. C.; Kast, E.; Fawcett, S. E.; Hain, M.; Sigman, D. M.

2016-12-01

The nitrogen (N) isotope ratios of diatom-bound organic matter recovered from Southern Ocean sediment cores have been used to investigate N cycling and the global carbon cycle over glacial-interglacial transitions. Increases in diatom-bound 15N/14N (δ15N) and decreases in export production have qualitatively been interpreted to reflect elevated nitrate (NO3-) consumption and decreased nutrient supply during glacial intervals; however, studies have yet to quantitatively relate paleoceanographic δ15N records to the surface NO3- concentration of ancient oceans. Furthermore, recent studies of the N and oxygen (O) isotope ratios of seawater NO3- reveal that seasonal processes may impact the isotopic signal of exported organic matter. The connection between diatom-bound δ15N and paleoceanographic NO3- availability is explored using a seasonally-resolved 1-dimension model of the Southern Ocean upper water column. The model parameterizes summer and winter physical and biogeochemical processes in the surface mixed layer and the temperature minimum layer. When calibrated to modern conditions, the model reproduces observed deviations from Rayleigh dynamics in the mixed layer, which result from a combination of summertime remineralization, late-summer N recycling, and wintertime nitrification. In glacial simulations, we observe an increase in diatom-bound δ15N that results dominantly from enhanced summertime NO3- consumption, as opposed to resulting from a rise in the δ15N of wintertime NO3-. Yet wintertime mixed layer (and thus initial spring/summer) NO3- concentration is greatly reduced under ice age conditions, such that export production, which has been observed to be lower during glacial intervals, was nevertheless able to consume almost all of the gross nitrate supply. The model suggests that observed differences in δ15N between centric and pennate diatom assemblages can be explained by the near-complete consumption of NO3- in the ice age summer mixed layer.

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

Nguyen, Thien Khoi V.; Ghate, Virendra P.; Carlton, Annmarie G.

Summertime aerosol optical thickness (AOT) over the Southeast U.S. is sharply enhanced over wintertime values. This seasonal pattern is unique and of particular interest because temperatures there have not warmed over the past 100 years. Patterns in surface fine particle mass are inconsistent with satellite reported AOT. In this work, we attempt to reconcile the spatial and temporal distribution of AOT over the U.S. with particle mass measurements at the surface by examining trends in aerosol liquid water (ALW), a particle constituent that scatters radiation affecting the satellite AOT, but is removed in mass measurements at routine surface monitoring sites.more » We employ the thermodynamic model ISORROPIAv2.1 to estimate ALW mass concentrations at IMRPOVE sites using measured ion mass concentrations and NARR meteorological data. Our findings suggest ALW provides a plausible explanation for the geographical and seasonal patterns in AOT and can reconcile previously noted discrepancies with surface mass measurements.« less

10-Year Observations of Cloud and Surface Longwave Radiation at Ny-Ålesund, Svalbard

NASA Astrophysics Data System (ADS)

Yeo, H.; Kim, S. W.; Kim, B. M.; Kim, J. H.; Shiobara, M.; Choi, T. J.; Son, S. W.; Kim, M. H.; Jeong, J. H.; Kim, S. J.

2015-12-01

Arctic clouds play a key role in surface radiation budget and may influence sea ice and snow melting. In this study, 10-year (2004-2013) observations of cloud from Micro-Pulse Lidar (MPL) and surface longwave (LW) radiation at Ny-Ålesund, Svalbard are analyzed to investigate cloud radiative effect. The cloud fraction (CF) derived from MPL shows distinct monthly variation, having higher CF (0.90) in summer and lower CF (0.79) in winter. Downward longwave radiation (DLW) during wintertime (Nov., Dec., Jan., and Feb.) decreases as cloud base height (CBH) increases. The DLW for CBH < 1km (264.7±35.4 W m-2) is approximately 1.46 times larger than that for cloud-free (181.8±25.8 W m-2) conditions. The temperature difference (ΔT) and DLW difference (ΔDLW), which are calculated as the difference of monthly mean temperature and DLW between all-sky and cloud-free conditions, are positively correlated (R2 = 0.83). This implies that an increase of DLW may influence surface warming, which can result in snow and sea ice melting. However, dramatic changes in surface temperature, cloud and DLW are observed with a time scale of a few days. The averaged surface temperature on the presence of low-level clouds (CBH < 2km) and under cloud-free conditions are estimated to be -6.9±6.1°C and -14.5±5.7°C, respectively. The duration of low-level clouds, showing relatively high DLW and high surface temperature, is about 2.5 days. This suggests that DLW induced by low-level clouds may not have a critical effect on surface temperature rising and sea ice melting.

Structure and Dynamics of Decadal Anomalies in the Wintertime Midlatitude North Pacific Ocean-Atmosphere System

NASA Astrophysics Data System (ADS)

Fang, J.

2017-12-01

The structure and dynamics of decadal anomalies in the wintertime midlatitude North Pacific ocean- atmosphere system are examined in this study, using the NCEP/NCAR atmospheric reanalysis, HadISST SST and Simple Ocean Data Assimilation data for 1960-2010. The midlatitude decadal anomalies associated with the Pacific Decadal Oscillation are identified, being characterized by an equivalent barotropic atmospheric low (high) pressure over a cold (warm) oceanic surface. Such a unique configuration of decadal anomalies can be maintained by an unstable ocean-atmosphere interaction mechanism in the midlatitudes, which is hypothesized as follows. Associated with a warm PDO phase, an initial midlatitude surface westerly anomaly accompanied with intensified Aleutian low tends to force a negative SST anomaly by increasing upward surface heat fluxes and driving southward Ekman current anomaly. The SST cooling tends to increase the meridional SST gradient, thus enhancing the subtropical oceanic front. As an adjustment of the atmospheric boundary layer to the enhanced oceanic front, the low-level atmospheric meridional temperature gradient and thus the low-level atmospheric baroclinicity tend to be strengthened, inducing more active transient eddy activities that increase transient eddy vorticity forcing. The vorticity forcing that dominates the total atmospheric forcing tends to produce an equivalent barotropic atmospheric low pressure north of the initial westerly anomaly, intensifying the initial anomalies of the midlatitude surface westerly and Aleutian low. Therefore, it is suggested that the midlatitude ocean-atmosphere interaction can provide a positive feedback mechanism for the development of initial anomaly, in which the oceanic front and the atmospheric transient eddy are the indispensable ingredients. Such a positive ocean-atmosphere feedback mechanism is fundamentally responsible for the observed decadal anomalies in the midlatitude North Pacific ocean-atmosphere system.

Factorial-based response-surface modeling with confidence intervals for optimizing thermal-optical transmission analysis of atmospheric black carbon.

PubMed

Conny, J M; Norris, G A; Gould, T R

2009-03-09

Thermal-optical transmission (TOT) analysis measures black carbon (BC) in atmospheric aerosol on a fibrous filter. The method pyrolyzes organic carbon (OC) and employs laser light absorption to distinguish BC from the pyrolyzed OC; however, the instrument does not necessarily separate the two physically. In addition, a comprehensive temperature protocol for the analysis based on the Beer-Lambert Law remains elusive. Here, empirical response-surface modeling was used to show how the temperature protocol in TOT analysis can be modified to distinguish pyrolyzed OC from BC based on the Beer-Lambert Law. We determined the apparent specific absorption cross sections for pyrolyzed OC (sigma(Char)) and BC (sigma(BC)), which accounted for individual absorption enhancement effects within the filter. Response-surface models of these cross sections were derived from a three-factor central-composite factorial experimental design: temperature and duration of the high-temperature step in the helium phase, and the heating increase in the helium-oxygen phase. The response surface for sigma(BC), which varied with instrument conditions, revealed a ridge indicating the correct conditions for OC pyrolysis in helium. The intersection of the sigma(BC) and sigma(Char) surfaces indicated the conditions where the cross sections were equivalent, satisfying an important assumption upon which the method relies. 95% confidence interval surfaces defined a confidence region for a range of pyrolysis conditions. Analyses of wintertime samples from Seattle, WA revealed a temperature between 830 degrees C and 850 degrees C as most suitable for the helium high-temperature step lasting 150s. However, a temperature as low as 750 degrees C could not be rejected statistically.

New Hampshire's Changing Wintertime Climate: Impact on Forestry Practices

NASA Astrophysics Data System (ADS)

Wurtzel, J. B.; Wake, C. P.

2007-12-01

Over the past four decades wintertime temperatures in New England have risen more than 2 degrees Celsius. This has had a significant impact on winter recreation in the region. Here we examine the effect of New Hampshire's warming wintertime climate on the logging industry, a vital source of revenue in New Hampshire, particularly in the northern counties such as Coos and Grafton. Recent statements from the industry have indicated that warmer wintertime temperatures have reduced the number of days for which the road is frozen and able to support the weight of the logging trucks. To assess the magnitude of change in New Hampshire, we examined the change in number of frozen road days in 15 locations for the period December through March for the years 1970 to 2007. We applied a Freeze-Thaw formula, based on daily mean temperatures, to determine when the roads were frozen or thawed. By dividing the state into three regions based on latitude and taking the mean results of the 5 towns located in each region, we find that since 1970 the northern region has lost 9 frozen road days and the central region has lost 10 frozen road days. The southern region also shows a loss in frozen days but with a much weaker trend. We also performed a sensitivity analysis by calculating trends using start years from 1965 to 1975 and found that the original results were robust. The strongest individual town trend was found in Berlin, located in Coos County, having already lost 18 days since 1970. Using estimates from a prior study suggest that the cost of a 9 day reduction in frozen road days per winter represents a loss of more than one million dollars in stumpage fees per year. The results of this study suggest that the forestry industry may need to consider alternative methods for logging in the near future.

Local atmospheric response to warm mesoscale ocean eddies in the Kuroshio-Oyashio Confluence region.

PubMed

Sugimoto, Shusaku; Aono, Kenji; Fukui, Shin

2017-09-19

In the extratropical regions, surface winds enhance upward heat release from the ocean to atmosphere, resulting in cold surface ocean: surface ocean temperature is negatively correlated with upward heat flux. However, in the western boundary currents and eddy-rich regions, the warmer surface waters compared to surrounding waters enhance upward heat release-a positive correlation between upward heat release and surface ocean temperature, implying that the ocean drives the atmosphere. The atmospheric response to warm mesoscale ocean eddies with a horizontal extent of a few hundred kilometers remains unclear because of a lack of observations. By conducting regional atmospheric model experiments, we show that, in the Kuroshio-Oyashio Confluence region, wintertime warm eddies heat the marine atmospheric boundary layer (MABL), and accelerate westerly winds in the near-surface atmosphere via the vertical mixing effect, leading to wind convergence around the eastern edge of eddies. The warm-eddy-induced convergence forms local ascending motion where convective precipitation is enhanced, providing diabatic heating to the atmosphere above MABL. Our results indicate that warm eddies affect not only near-surface atmosphere but also free atmosphere, and possibly synoptic atmospheric variability. A detailed understanding of warm eddy-atmosphere interaction is necessary to improve in weather and climate projections.

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.

Roles of tropical SST patterns during two types of ENSO in modulating wintertime rainfall over southern China

NASA Astrophysics Data System (ADS)

Xu, Kang; Huang, Qing-Lan; Tam, Chi-Yung; Wang, Weiqiang; Chen, Sheng; Zhu, Congwen

2018-03-01

The impacts of the eastern-Pacific (EP) and central-Pacific (CP) El Niño-Southern Oscillation (ENSO) on the southern China wintertime rainfall (SCWR) have been investigated. Results show that wintertime rainfall over most stations in southern China is enhanced (suppressed) during the EP (CP) El Niño, which are attributed to different atmospheric responses in the western North Pacific (WNP) and South China Sea (SCS) during two types of ENSO. When EP El Niño occurs, an anomalous low-level anticyclone is present over WNP/the Philippines region, resulting in stronger-than-normal southwesterlies over SCS. Such a wind branch acts to suppress East Asian winter monsoon (EAWM) and enhance moisture supply, implying surplus SCWR. During CP El Niño, however, anomalous sinking and low-level anticyclonic flow are found to cover a broad region in SCS. These circulation features are associated with moisture divergence over the northern part of SCS and suppressed SCWR. General circulation model experiments have also been conducted to study influence of various tropical sea surface temperature (SST) patterns on the EAWM atmospheric circulation. For EP El Niño, formation of anomalous low-level WNP anticyclone is jointly attributed to positive/negative SST anomalies (SSTA) over the central-to-eastern/ western equatorial Pacific. However, both positive and negative CP Niño-related-SSTA, located respectively over the central Pacific and WNP/SCS, offset each other and contribute a weak but broad-scale anticyclone centered at SCS. These results suggest that, besides the vital role of SST warming, SST cooling over SCS/WNP during two types of El Niño should be considered carefully for understanding the El Niño-EAWM relationship.

Observational Insights into N2O5 Heterogeneous Chemistry: Influencing Factors and Contribution to Wintertime Air Pollution

NASA Astrophysics Data System (ADS)

McDuffie, E. E.; Fibiger, D. L.; Womack, C.; Dube, W. P.; Lopez-Hilfiker, F.; Goldberger, L.; Thornton, J. A.; Shah, V.; Jaegle, L.; Guo, H.; Weber, R. J.; Schroder, J. C.; Campuzano Jost, P.; Jimenez, J. L.; Franchin, A.; Middlebrook, A. M.; Baasandorj, M.; Brown, S. S.

2017-12-01

Chemical mechanisms that underlie wintertime air pollution, including tropospheric ozone and aerosol nitrate, are poorly characterized. Due to colder temperatures and fewer hours of solar radiation, nocturnal heterogeneous uptake of N2O5 plays a relatively larger role during wintertime in controlling the oxidation of NOx (=NO+NO2) and its influence on ozone and soluble nitrate. After uptake to aerosol, N2O5 can act as both a nocturnal NOx reservoir and sink depending on the partitioning between its nitric acid and photo labile, ClNO2 reaction products. In addition, N2O5 itself can act as a NOx reservoir if the aerosol uptake coefficient is small. As a result, the nocturnal fate of N2O5 dictates the amount of NOx in an air parcel and the subsequent formation of aerosol nitrate and following-day ozone. Models of winter air pollution therefore require accurate parameterization of the N2O5 uptake coefficient, as well as factors that control its magnitude and N2O5 product partitioning. There are currently only a small number of ambient N2O5 and ClNO2 observations during the winter season concurrent with measurements of relevant variables such as aerosol size distributions and composition. The Wintertime INvestigation of Transport, Emissions, and Reactivity (WINTER) campaign conducted 10 nighttime research flights with the NCAR C-130 over the eastern U.S. during February and March, 2015. The more recent Utah Wintertime Fine Particulate Study (UWFPS) conducted over 20 research flights with the NOAA twin otter aircraft during January-February 2017 in three mountain basins near and including Salt Lake City, Utah. The two campaigns were similarly instrumented and have provided the first aircraft observations of N2O5, ClNO2, and aerosol composition in the wintertime boundary layer in these urban-influenced regions. Analysis of heterogeneous chemistry under a wide range of real environmental conditions provides insight into the factors controlling the N2O5 uptake coefficient, product partitioning, and contribution of N2O5 to wintertime pollution events in urban regions across the U.S.

Winter in Antarctica: dark, cold, windy, and .... wet?? Measurements and modeling of extensive wintertime surface melt

NASA Astrophysics Data System (ADS)

Kuipers Munneke, P.; Luckman, A. J.; Bevan, S. L.; Gilbert, E.; Smeets, P.; van den Broeke, M. R.; Wang, W.; Zender, C. S.; Ashmore, D. W.; Hubbard, B. P.; Orr, A.; King, J.

2017-12-01

We know that increased surface melt, driven by atmospheric warming, contributed to the collapse of ice shelves as observed in the Antarctic Peninsula. This has induced grounded-ice acceleration and increased ice discharge. You may associate this surface melt with the austral summer season, with plenty of solar radiation driving the melt. In contrast, winter in Antarctica evokes images of darkness, snow, and cold. However, we will make you rethink this picture by presenting observations of frequent snow surface melt in winter, from a weather station located in a previously unsurveyed area of the Larsen C Ice Shelf. Peak intensities of this wintertime melt even exceed summertime values, and thermal satellite images show that large ponds of meltwater are formed at the surface in the pitch-dark Antarctic winter. Obviously, we wanted to find out what could drive these strong melt events if it's not the sun. It turns out that these multi-day melt events occur when warm and dry föhn winds descend from the Antarctic Peninsula mountains. Simulations with a high-resolution weather model confirm that these winds generate turbulent fluxes of sensible heat, leading to melt fluxes in excess of 200 W m-2. In 2015 and 2016, about 23% of the annual melt was produced in winter. We use satellite radar to show that winter melt occurs on many more places in the Antarctic Peninsula. It happens every year, although in some years the melting is much more widespread than in others. We think that wintertime melt matters as its refreezing warms the snow and increases snow density. In this way, winter melt preconditions the ice shelf for more extensive surface drainage, potentially leading to meltwater-driven instability.

Estimating diffusivity from the mixed layer heat and salt balances in the North Pacific

NASA Astrophysics Data System (ADS)

Cronin, M. F.; Pelland, N.; Emerson, S. R.; Crawford, W. R.

2015-12-01

Data from two National Oceanographic and Atmospheric Administration (NOAA) surface moorings in the North Pacific, in combination with data from satellite, Argo floats and glider (when available), are used to evaluate the residual diffusive flux of heat across the base of the mixed layer from the surface mixed layer heat budget. The diffusion coefficient (i.e., diffusivity) is then computed by dividing the diffusive flux by the temperature gradient in the 20-m transition layer just below the base of the mixed layer. At Station Papa in the NE Pacific subpolar gyre, this diffusivity is 1×10-4 m2/s during summer, increasing to ~3×10-4 m2/s during fall. During late winter and early spring, diffusivity has large errors. At other times, diffusivity computed from the mixed layer salt budget at Papa correlate with those from the heat budget, giving confidence that the results are robust for all seasons except late winter-early spring and can be used for other tracers. In comparison, at the Kuroshio Extension Observatory (KEO) in the NW Pacific subtropical recirculation gyre, somewhat larger diffusivity are found based upon the mixed layer heat budget: ~ 3×10-4 m2/s during the warm season and more than an order of magnitude larger during the winter, although again, wintertime errors are large. These larger values at KEO appear to be due to the increased turbulence associated with the summertime typhoons, and weaker wintertime stratification.

Estimating diffusivity from the mixed layer heat and salt balances in the North Pacific

NASA Astrophysics Data System (ADS)

Cronin, Meghan F.; Pelland, Noel A.; Emerson, Steven R.; Crawford, William R.

2015-11-01

Data from two National Oceanographic and Atmospheric Administration (NOAA) surface moorings in the North Pacific, in combination with data from satellite, Argo floats and glider (when available), are used to evaluate the residual diffusive flux of heat across the base of the mixed layer from the surface mixed layer heat budget. The diffusion coefficient (i.e., diffusivity) is then computed by dividing the diffusive flux by the temperature gradient in the 20 m transition layer just below the base of the mixed layer. At Station Papa in the NE Pacific subpolar gyre, this diffusivity is 1 × 10-4 m2/s during summer, increasing to ˜3 × 10-4 m2/s during fall. During late winter and early spring, diffusivity has large errors. At other times, diffusivity computed from the mixed layer salt budget at Papa correlate with those from the heat budget, giving confidence that the results are robust for all seasons except late winter-early spring and can be used for other tracers. In comparison, at the Kuroshio Extension Observatory (KEO) in the NW Pacific subtropical recirculation gyre, somewhat larger diffusivities are found based upon the mixed layer heat budget: ˜ 3 × 10-4 m2/s during the warm season and more than an order of magnitude larger during the winter, although again, wintertime errors are large. These larger values at KEO appear to be due to the increased turbulence associated with the summertime typhoons, and weaker wintertime stratification.

Measurements and Modeling of Turbulent Fluxes during Persistent Cold Air Pool Events in Salt Lake Valley, Utah

NASA Astrophysics Data System (ADS)

Ivey, C. E.; Sun, X.; Holmes, H.

2017-12-01

Land surface processes are important in meteorology and climate research since they control the partitioning of surface energy and water exchange at the earth's surface. The surface layer is coupled to the planetary boundary layer (PBL) by surface fluxes, which serve as sinks or sources of energy, moisture, momentum, and atmospheric pollutants. Quantifying the surface heat and momentum fluxes at the land-atmosphere interface, especially for different surface land cover types, is important because they can further influence the atmospheric dynamics, vertical mixing, and transport processes that impact local, regional, and global climate. A cold air pool (CAP) forms when a topographic depression (i.e., valley) fills with cold air, where the air in the stagnant layer is colder than the air aloft. Insufficient surface heating, which is not able to sufficiently erode the temperature inversion that forms during the nighttime stable boundary layer, can lead to the formation of persistent CAPs during wintertime. These persistent CAPs can last for days, or even weeks, and are associated with increased air pollution concentrations. Thus, realistic simulations of the land-atmosphere exchange are meaningful to achieve improved predictions of the accumulation, transport, and dispersion of air pollution concentrations. The focus of this presentation is on observations and modeling results using turbulence data collected in Salt Lake Valley, Utah during the 2010-2011 wintertime Persistent Cold Air Pool Study (PCAPS). Turbulent fluxes and the surface energy balance over seven land use types are quantified. The urban site has an energy balance ratio (EBR) larger than one (1.276). Negative Bowen ratio (-0.070) is found at the cropland site. In addition to turbulence observations, half-hourly WRF simulated net radiation, latent heat, sensible heat, ground heat fluxes during one persistent CAP event are evaluated using the PCAPS observations. The results show that sensible and latent heat fluxes during the CAP event are overestimated. The sensitivity of WRF results to large-scale forcing datasets, PBL schemes and land surface models (LSMs) are also investigated. The optimal WRF configuration for simulating surface turbulent fluxes and atmospheric mixing during CAP events is determined.

Temperature effects on multiphase reactions of organic molecular markers: A modeling study

NASA Astrophysics Data System (ADS)

Pratap, Vikram; Chen, Ying; Yao, Guangming; Nakao, Shunsuke

2018-04-01

Various molecular markers are used in source apportionment studies. In early studies, molecular markers were assumed to be inert. However, recent studies suggest that molecular markers can decay rapidly through multiphase reactions, which makes interpretation of marker measurements challenging. This study presents a simplified model to account for the effects of temperature and relative humidity on the lifetime of molecular markers through a shift in gas-particle partitioning as well as a change in viscosity of the condensed phase. As a model case, this study examines the stability of levoglucosan, a key marker species of biomass burning, over a wide temperature range relevant to summertime and wintertime. Despite the importance of wood combustion for space heating in winter, the lifetime of levoglucosan in wintertime is not well understood. The model predicts that in low-temperature conditions, levoglucosan predominantly remains in the particle phase, and therefore its loss due to gas-phase oxidation reactions is significantly reduced. Furthermore, the movement of the levoglucosan from the bulk of the particle to the particle surface is reduced due to low diffusivity in the semi-solid state. The simplified model developed in this study reasonably reproduces upper and lower bounds of the lifetime of levoglucosan investigated in previous studies. The model results show that the levoglucosan depletion after seven days reduces significantly from ∼98% at 25 °C to <1% at 0 °C under dry conditions. The depletion of levoglucosan increases at higher relative humidities. However, at temperatures below 0 °C, levoglucosan appears to be a useful marker (lifetime > 1 week) even at 60% relative humidity irrespective of the assumed fragility parameter D that controls estimated diffusivity. The model shows that lifetime of an organic molecular marker strongly depends on assumed D especially when a semi-volatile marker is in semi-solid organic aerosol.

North American wintertime temperature anomalies: the role of El Niño diversity and differential teleconnections

NASA Astrophysics Data System (ADS)

Beyene, Mussie T.; Jain, Shaleen

2018-06-01

El Niño-Southern Oscillation (ENSO) teleconnections induced wintertime surface air temperature (SAT) anomalies over North America show inter-event variability, asymmetry, and nonlinearity. This diagnostic study appraises the assumption that ENSO-induced teleconnections are adequately characterized as symmetric shifts in the SAT probability distributions for North American locations. To this end, a new conditional quantile functional estimation approach presented here incorporates: (a) the detailed nature of location and amplitude of SST anomalies—in particular the Eastern Pacific (EP), Central Pacific (CP) ENSO events—based on its two leading principal components, and (b) over the entire range of SATs, characterize the differential sensitivity to ENSO. Statistical significance is assessed using a wild bootstrap approach. Conditional risk at upper and lower quartile SAT conditioned on archetypical ENSO states is derived. There is marked asymmetry in ENSO effects on the likelihood of upper and lower quartile winter SATs for most North American regions. CP El Niño patterns show 20-80% decrease in the likelihood of lower quartile SATs for Canada and US west coast and a 20-40% increase across southeastern US. However, the upper quartile SAT for large swathes of Canada shows no sensitivity to CP El Niño. Similarly, EP El Niño is linked to a 40-80% increase in the probability of upper quartile winter SATs for Canada and northern US and a 20% decrease for southern US and northern Mexico regions; however, little or no change in the risk of lower quartile winter temperatures for southern parts of North America. Localized estimate of ENSO-related risk are also presented.

Numerical Representation of Wintertime Near-Surface Inversions in the Arctic with a 2.5-km Version of the Global Environmental Multiscale (GEM) Model

NASA Astrophysics Data System (ADS)

Dehghan, A.; Mariani, Z.; Gascon, G.; Bélair, S.; Milbrandt, J.; Joe, P. I.; Crawford, R.; Melo, S.

2017-12-01

Environment and Climate Change Canada (ECCC) is implementing a 2.5-km resolution version of the Global Environmental Multiscale (GEM) model over the Canadian Arctic. Radiosonde observations were used to evaluate the numerical representation of surface-based temperature inversion which is a major feature in the Arctic region. Arctic surface-based inversions are often created by imbalance between radiative cooling processes at surface and warm air advection above. This can have a significant effect on vertical mixing of pollutants and moisture, and ultimately, on cloud formation. It is therefore important to correctly predict the existence of surface inversions along with their characteristics (i.e., intensity and depth). Previous climatological studies showed that the frequency and intensity of surface-based inversions are larger during colder months in the Arctic. Therefore, surface-based inversions were estimated using radiosonde measurements during winter (December 2015 to February 2016) at Iqaluit (Nunavut, Canada). Results show that the inversion intensity can exceed 10 K with depths as large as 1 km. Preliminary evaluation of GEM outputs reveals that the model tends to underestimate the intensity of near-surface inversions, and in some cases, the model failed to predict an inversion. This study presents the factors contributing to this bias including surface temperature and snow cover.

Physical and biological response of mesoscale eddies to wintertime forcing in the north central Red Sea (22˚N-25.5˚N)

NASA Astrophysics Data System (ADS)

Zarokanellos, N.; Jones, B. H.

2016-02-01

Red Sea is one of the saltiest and warmer seas in the world and acts as inverted estuary. Until recently, the Red Sea has been relatively underexplored. The limited observations that exist and results from various modeling exercises for the Red Sea have indicated that the sea has a complex mesoscale circulation often dominated by eddies. These mesoscale eddies are often visible in satellite imagery of sea surface height, temperature or chlorophyll, but only the surface expression of them. Because of previously limited in situ observations, the processes that drive the physical dynamics and the coupled biological responses have been poorly understood. To resolve and understand the role of these eddies in the dynamics of the north-central Red Sea during the wintertime, we used a combination of approaches that include remote sensing and autonomous underwater gliders equipped with physical, chemical, and bio-optical sensors. Remote sensing analyses of these eddies has shown that these eddies not only affect the physical circulation, but modify and disperse the phytoplankton populations and enhance exchange between the open sea and coastal coral reef ecosystems. During winter 2015, we observed deeper mixing driven by surface cooling and strong winds. As of result of the deeper mixing, phytoplankton populations became well mixed such that the ocean color imagery now reflected the integrated vertical processes. Localized diel fluctuations in phytoplankton are clearly evident during these well mixed periods. The mixing likely contributes to enhanced nutrient fluxes as well. Through sustained AUV observations, we have better understand the development, evolution, and dissipation of eddies. We also now have a better understanding of the mixing of source water from both the northern and southern Red Sea in this region of the north central Red Sea.

Effects of the diurnal cycle in solar radiation on the tropical Indian Ocean mixed layer variability during wintertime Madden-Julian Oscillations

NASA Astrophysics Data System (ADS)

Li, Yuanlong; Han, Weiqing; Shinoda, Toshiaki; Wang, Chunzai; Lien, Ren-Chieh; Moum, James N.; Wang, Jih-Wang

2013-10-01

The effects of solar radiation diurnal cycle on intraseasonal mixed layer variability in the tropical Indian Ocean during boreal wintertime Madden-Julian Oscillation (MJO) events are examined using the HYbrid Coordinate Ocean Model. Two parallel experiments, the main run and the experimental run, are performed for the period of 2005-2011 with daily atmospheric forcing except that an idealized hourly shortwave radiation diurnal cycle is included in the main run. The results show that the diurnal cycle of solar radiation generally warms the Indian Ocean sea surface temperature (SST) north of 10°S, particularly during the calm phase of the MJO when sea surface wind is weak, mixed layer is thin, and the SST diurnal cycle amplitude (dSST) is large. The diurnal cycle enhances the MJO-forced intraseasonal SST variability by about 20% in key regions like the Seychelles-Chagos Thermocline Ridge (SCTR; 55°-70°E, 12°-4°S) and the central equatorial Indian Ocean (CEIO; 65°-95°E, 3°S-3°N) primarily through nonlinear rectification. The model also well reproduced the upper-ocean variations monitored by the CINDY/DYNAMO field campaign between September-November 2011. During this period, dSST reaches 0.7°C in the CEIO region, and intraseasonal SST variability is significantly amplified. In the SCTR region where mean easterly winds are strong during this period, diurnal SST variation and its impact on intraseasonal ocean variability are much weaker. In both regions, the diurnal cycle also has a large impact on the upward surface turbulent heat flux QT and induces diurnal variation of QT with a peak-to-peak difference of O(10 W m-2).

Revisiting the Processes That Determine Wintertime Intraseasonal SST Variability in the Thermocline Ridge of the Tropical South Indian Ocean

NASA Astrophysics Data System (ADS)

Han, W.; Li, Y.; Shinoda, T.; Wang, C.; Ravichandran, M.; Wang, J. W.

2014-12-01

Intraseasonal sea surface temperature (SST) variability over the Seychelles-Chagos thermocline ridge (SCTR) induced by boreal wintertime Madden-Julian oscillations (MJOs) is investigated by performing a series of OGCM experiments with improved model configuration and the recently available high quality satellite forcing fields. The impact of the ocean interannual variation of the thermocline depth -represented by the depth of 20C isotherm (D20) - in the SCTR is also assessed. The OGCM main run solution agrees well with the observations. The results show that for the 2001-2011 period, surface shortwave radiation (SWR), turbulent heat fluxes associated with wind speed, and wind stress-driven ocean dynamical processes are all important in causing the MJO-related intraseasonal SST variability in the SCTR region. Overall, forcing by SWR contributes ~31%, and forcing by winds (via both surface turbulent heat flux and ocean dynamics) contributes ~62%. The contribution of turbulent heat flux associated with wind speed is ~39% and that of wind-stress driven ocean dynamics is ~23%. The contribution of ocean dynamics, however, is considerably larger during strong ("prime") MJO events under "strong" thermocline condition. The overall effect of interannual variability of D20 on intraseasonal SST during 2001-2011 is significant in the eastern part of the SCTR (70E-85E), where the intraseasonal SST amplitudes are strengthened by about 20%. In general, a shallower/deeper SCTR favors larger/smaller SST responses to the MJO forcing. In the eastern SCTR, both the heat flux forcing and entrainment are greatly amplified under the strong SCTR condition, but only slightly suppressed under the weak SCTR condition, leading to an overall strengthening effect on intraseasonal SST variability.

Detrended Partial-Cross-Correlation Analysis: A New Method for Analyzing Correlations in Complex System

PubMed Central

Yuan, Naiming; Fu, Zuntao; Zhang, Huan; Piao, Lin; Xoplaki, Elena; Luterbacher, Juerg

2015-01-01

In this paper, a new method, detrended partial-cross-correlation analysis (DPCCA), is proposed. Based on detrended cross-correlation analysis (DCCA), this method is improved by including partial-correlation technique, which can be applied to quantify the relations of two non-stationary signals (with influences of other signals removed) on different time scales. We illustrate the advantages of this method by performing two numerical tests. Test I shows the advantages of DPCCA in handling non-stationary signals, while Test II reveals the “intrinsic” relations between two considered time series with potential influences of other unconsidered signals removed. To further show the utility of DPCCA in natural complex systems, we provide new evidence on the winter-time Pacific Decadal Oscillation (PDO) and the winter-time Nino3 Sea Surface Temperature Anomaly (Nino3-SSTA) affecting the Summer Rainfall over the middle-lower reaches of the Yangtze River (SRYR). By applying DPCCA, better significant correlations between SRYR and Nino3-SSTA on time scales of 6 ~ 8 years are found over the period 1951 ~ 2012, while significant correlations between SRYR and PDO on time scales of 35 years arise. With these physically explainable results, we have confidence that DPCCA is an useful method in addressing complex systems. PMID:25634341

Surface formation, preservation, and history of low-porosity crusts at the WAIS Divide site, West Antarctica

NASA Astrophysics Data System (ADS)

Fegyveresi, John M.; Alley, Richard B.; Muto, Atsuhiro; Orsi, Anaïs J.; Spencer, Matthew K.

2018-01-01

Observations at the West Antarctic Ice Sheet (WAIS) Divide site show that near-surface snow is strongly altered by weather-related processes such as strong winds and temperature fluctuations, producing features that are recognizable in the deep ice core. Prominent glazed surface crusts develop frequently at the site during summer seasons. Surface, snow pit, and ice core observations made in this study during summer field seasons from 2008-2009 to 2012-2013, supplemented by automated weather station (AWS) data with short- and longwave radiation sensors, revealed that such crusts formed during relatively low-wind, low-humidity, clear-sky periods with intense daytime sunshine. After formation, such glazed surfaces typically developed cracks in a polygonal pattern likely from thermal contraction at night. Cracking was commonest when several clear days occurred in succession and was generally followed by surface hoar growth; vapor escaping through the cracks during sunny days may have contributed to the high humidity that favored nighttime formation of surface hoar. Temperature and radiation observations show that daytime solar heating often warmed the near-surface snow above the air temperature, contributing to upward mass transfer, favoring crust formation from below, and then surface hoar formation. A simple surface energy calculation supports this observation. Subsequent examination of the WDC06A deep ice core revealed that crusts are preserved through the bubbly ice, and some occur in snow accumulated during winters, although not as commonly as in summertime deposits. Although no one has been on site to observe crust formation during winter, it may be favored by greater wintertime wind packing from stronger peak winds, high temperatures and steep temperature gradients from rapid midwinter warmings reaching as high as -15 °C, and perhaps longer intervals of surface stability. Time variations in crust occurrence in the core may provide paleoclimatic information, although additional studies are required. Discontinuity and cracking of crusts likely explain why crusts do not produce significant anomalies in other paleoclimatic records.

The classification of the Arctic Sea ice types and the determination of surface temperature using advanced very high resolution radiometer data

NASA Technical Reports Server (NTRS)

Massom, Robert; Comiso, Josefino C.

1994-01-01

The accurate quantification of new ice and open water areas and surface temperatures within the sea ice packs is a key to the realistic parameterization of heat, moisture, and turbulence fluxes between ocean and atmosphere in the polar regions. Multispectral NOAA advanced very high resolution radiometer/2 (AVHRR/2) satellite images are analyzed to evaluate how effectively the data can be used to characterize sea ice in the Bering and Greenland seas, both in terms of surface type and physical temperature. The basis of the classification algorithm, which is developed using a late wintertime Bering Sea ice cover data, is that frequency distributions of 10.8- micrometers radiances provide four distinct peaks, represeting open water, new ice, young ice, and thick ice with a snow cover. The results are found to be spatially and temporally consistent. Possible sources of ambiguity, especially associated with wider temporal and spatial application of the technique, are discussed. An ice surface temperature algorithm is developed for the same study area by regressing thermal infrared data from 10.8- and 12.0- micrometers channels against station air temperatures, which are assumed to approximate the skin temperatures of adjacent snow and ice. The standard deviations of the results when compared with in situ data are about 0.5 K over leads and polynyas to about 0.5-1.5 K over thick ice. This study is based upon a set of in situ data limited in scope and coverage. Cloud masks are applied using a thresholding technique that utilizes 3.74- and 10.8- micrometers channel data. The temperature maps produced show coherence with surface features like new ice and leads, and consistency with corresponding surface type maps. Further studies are needed to better understand the effects of both the spatial and temporal variability in emissivity, aerosol and precipitable atmospheric ice particle distribution, and atmospheric temperature inversions.

The Siberian High and Arctic Sea Ice: Long-term Climate Change and Impacts on Air Pollution during Wintertime in China

NASA Astrophysics Data System (ADS)

Long, X.; Zhao, S.; Feng, T.; Tie, X.; Li, G.

2017-12-01

China has undergone severe air pollution during wintertime as national industrialization and urbanization have been increasingly developed in the past three decades. It has been suggested that high emission and adverse weather patterns contribute to wintertime air pollution. Recent studies propose that climate change and Arctic sea ice loss likely lead to extreme haze events in winter. Here we use two reanalysis and observational datasets to present the trends of Siberian High (SH) intensity over Eurasia, and Arctic temperature and sea ice. The results show the Arctic region of Asia is becoming warming accompanied by a rapid decline of sea ice while Eurasia is cooling and SH intensity is gradually enhancing. Wind patterns induced by these changes cause straight westerly prevailing over Eurasia at the year of weak SH while strengthened northerly winds at the year of strong SH. Therefore, we utilize regional dynamical and chemical WRF-Chem model to determine the impact of SH intensity difference on wintertime air pollution in China. As a result, enhancing northerly winds at the year of strong SH rapidly dilute and transport air pollution, causing a decline of 50 - 400 µg m-3 PM2.5 concentrations relative to that at the year of weak SH. We also assess the impact of emission reduction to half the current level on air pollution. The results show that emission reduction by 50% has an equivalent impact as the variability of SH intensity. This suggests that climate change over Eurasia has largely offset the negative impact of emission on air pollution and it is urgently needed to take measures to mitigate air pollution. In view of current high emission scenario in China, it will be a long way to effectively mitigate, or ultimately prevent wintertime air pollution.

Using Ozone Lidar to Investigate Sources of High Ozone Concentrations in the Western United States

NASA Astrophysics Data System (ADS)

Senff, C. J.; Langford, A. O.; Alvarez, R. J.; Brewer, Wm. A.; Banta, R. M.; Marchbanks, R. D.; Sandberg, S. P.; Weickmann, A. M.; Holloway, J. S.; Williams, E. J.

2016-06-01

We have used NOAA's Tunable Optical Profiler for Aerosol and oZone (TOPAZ) ozone lidar to investigate the sources of high surface ozone concentrations in two different regions of the western United States (US): the Uintah Basin in northeast Utah and Clark County in southern Nevada, which includes the city of Las Vegas. The Uintah Basin is a booming oil and gas producing region that often suffers from very high wintertime ozone concentrations. Clark County experiences violations of the US ozone standard primarily in spring and early summer despite a lack of any major local pollution sources. TOPAZ lidar observations, in conjunction with surface in situ measurements and model results, provided strong evidence that the high wintertime ozone concentrations in the Uintah Basin are primarily driven by local emissions associated with oil and gas exploration, whereas the Clark County ozone exceedances are often caused by ozone-rich air that is transported from the lower stratosphere all the way down to the earth's surface.

Analysis of the 1877-78 ENSO episode and comparison with 1982-83

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

Kiladis, G.N.; Diaz, H.F.

A comparison of the 1877-78 and 1982-83 El Nino/Southern Oscillation (ENSO) events was made using monthly and seasonal values of sea surface temperature (SST) and station pressure in the tropics, sea level pressure (SLP) in North America and the North Atlantic, temperature in North America and precipitation in several key areas around the globe. SST anomalies in the eastern tropical Pacific, heavy rains in coastal Peru and extreme pressure anomalies across the Pacific and Indian Oceans during 1877-78 indicate an ENSO event of comparable magnitude to that during 1982-83. Both events were also associated with drought conditions in the Indonesianmore » region, India, South Africa, northeastern Brazil and Hawaii. Wintertime teleconnections in the midlatitudes of the Northern Hemisphere were similar in terms of SLP from the North Pacific to Europe, resulting in significantly higher than normal temperatures over most of the US and extreme rains in California.« less

Pattern recognition analysis of polar clouds during summer and winter

NASA Technical Reports Server (NTRS)

Ebert, Elizabeth E.

1992-01-01

A pattern recognition algorithm is demonstrated which classifies eighteen surface and cloud types in high-latitude AVHRR imagery based on several spectral and textural features, then estimates the cloud properties (fractional coverage, albedo, and brightness temperature) using a hybrid histogram and spatial coherence technique. The summertime version of the algorithm uses both visible and infrared data (AVHRR channels 1-4), while the wintertime version uses only infrared data (AVHRR channels 3-5). Three days of low-resolution AVHRR imagery from the Arctic and Antarctic during January and July 1984 were analyzed for cloud type and fractional coverage. The analysis showed significant amounts of high cloudiness in the Arctic during one day in winter. The Antarctic summer scene was characterized by heavy cloud cover in the southern ocean and relatively clear conditions in the continental interior. A large region of extremely low brightness temperatures in East Antarctica during winter suggests the presence of polar stratospheric cloud.

The Impact of Trends in the Large Scale Atmospheric Circulation on Mediterranean Surface Turbulent Heat Fluxes

NASA Technical Reports Server (NTRS)

Romanski, Joy; Hameed, Sultan

2015-01-01

Interannual variations of latent heat fluxes (LHF) and sensible heat fluxes (SHF) over the Mediterranean for the boreal winter season (DJF) show positive trends during 1958-2011. Comparison of correlations between the heat fluxes and the intensity and location of the Azores High (AH), and the NAO and East Atlantic-West Russia (EAWR) teleconnections, along with analysis of composites of surface temperature, humidity and wind fields for different teleconnection states, demonstrates that variations of the AH are found to explain the heat flux changes more successfully than the NAO and the EAWR. Trends in sea level pressure and longitude of the Azores High during DJF show a strengthening, and an eastward shift. DJF Azores High pressure and longitude are shown to co-vary such that variability of the Azores High occurs along an axis defined by lower pressure and westward location at one extreme, and higher pressure and eastward location at the other extreme. The shift of the Azores High from predominance of the low/west state to the high/east state induces trends in Mediterranean Sea surface winds, temperature and moisture. These, combined with sea surface warming trends, produce trends in wintertime Mediterranean Sea sensible and latent heat fluxes.

The Impact of Trends in the Large Scale Atmospheric Circulation on Mediterranean Surface Turbulent Heat Fluxes

NASA Technical Reports Server (NTRS)

Romanski, Joy; Hameed, Sultan

2015-01-01

Interannual variations of latent heat fluxes (LHF) and sensible heat fluxes (SHF) over the Mediterranean for the boreal winter season (DJF) show positive trends during 1958-2011. Using reanalysis and satellite-based products, the variability and trends in the heat fluxes are compared with variations in three atmospheric teleconnection patterns: the North Atlantic Oscillation (NAO), the pressure and position of the Azores High (AH), and the East Atlantic-West Russia teleconnection pattern (EAWR). Comparison of correlations between the heat fluxes and teleconnections, along with analysis of composites of surface temperature, humidity, and wind fields for different teleconnection states, demonstrates that the AH explains the heat flux changes more successfully than NAO and EAWR. Trends in pressure and longitude of the Azores High show a strengthening and an eastward shift. Variations of the Azores High occur along an axis defined by lower pressure and westward location at one extreme and higher pressure and eastward location at the other extreme. The shift of the AH from predominance of the low/west state to the high/east state induces trends in Mediterranean Sea surface winds, temperature, and moisture. These, combined with sea surface warming trends, produce trends in wintertime sensible and latent heat fluxes.

Bacterial responses to fluctuations and extremes in temperature and brine salinity at the surface of Arctic winter sea ice.

PubMed

Ewert, Marcela; Deming, Jody W

2014-08-01

Wintertime measurements near Barrow, Alaska, showed that bacteria near the surface of first-year sea ice and in overlying saline snow experience more extreme temperatures and salinities, and wider fluctuations in both parameters, than bacteria deeper in the ice. To examine impacts of such conditions on bacterial survival, two Arctic isolates with different environmental tolerances were subjected to winter-freezing conditions, with and without the presence of organic solutes involved in osmoprotection: proline, choline, or glycine betaine. Obligate psychrophile Colwellia psychrerythraea strain 34H suffered cell losses under all treatments, with maximal loss after 15-day exposure to temperatures fluctuating between -7 and -25 °C. Osmoprotectants significantly reduced the losses, implying that salinity rather than temperature extremes presents the greater stress for this organism. In contrast, psychrotolerant Psychrobacter sp. strain 7E underwent miniaturization and fragmentation under both fluctuating and stable-freezing conditions, with cell numbers increasing in most cases, implying a different survival strategy that may include enhanced dispersal. Thus, the composition and abundance of the bacterial community that survives in winter sea ice may depend on the extent to which overlying snow buffers against extreme temperature and salinity conditions and on the availability of solutes that mitigate osmotic shock, especially during melting. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

Contribution of atmospheric circulation to recent off-shore sea-level variations in the Baltic Sea and the North Sea

NASA Astrophysics Data System (ADS)

Karabil, Sitar; Zorita, Eduardo; Hünicke, Birgit

2018-01-01

The main purpose of this study is to quantify the contribution of atmospheric factors to recent off-shore sea-level variability in the Baltic Sea and the North Sea on interannual timescales. For this purpose, we statistically analysed sea-level records from tide gauges and satellite altimetry and several climatic data sets covering the last century. Previous studies had concluded that the North Atlantic Oscillation (NAO) is the main pattern of atmospheric variability affecting sea level in the Baltic Sea and the North Sea in wintertime. However, we identify a different atmospheric circulation pattern that is more closely connected to sea-level variability than the NAO. This circulation pattern displays a link to sea level that remains stable through the 20th century, in contrast to the much more variable link between sea level and the NAO. We denote this atmospheric variability mode as the Baltic Sea and North Sea Oscillation (BANOS) index. The sea-level pressure (SLP) BANOS pattern displays an SLP dipole with centres of action located over (5° W, 45° N) and (20° E, 70° N) and this is distinct from the standard NAO SLP pattern in wintertime. In summertime, the discrepancy between the SLP BANOS and NAO patterns becomes clearer, with centres of action of the former located over (30° E, 45° N) and (20° E, 60° N). This index has a stronger connection to off-shore sea-level variability in the study area than the NAO in wintertime for the period 1993-2013, explaining locally up to 90 % of the interannual sea-level variance in winter and up to 79 % in summer. The eastern part of the Gulf of Finland is the area where the BANOS index is most sensitive to sea level in wintertime, whereas the Gulf of Riga is the most sensitive region in summertime. In the North Sea region, the maximum sea-level sensitivity to the BANOS pattern is located in the German Bight for both winter and summer seasons. We investigated, and when possible quantified, the contribution of several physical mechanisms which may explain the link between the sea-level variability and the atmospheric pattern described by the BANOS index. These mechanisms include the inverse barometer effect (IBE), freshwater balance, net energy surface flux and wind-induced water transport. We found that the most important mechanism is the IBE in both wintertime and summertime. Assuming a complete equilibration of seasonal sea level to the SLP gradients over this region, the IBE can explain up to 88 % of the sea-level variability attributed to the BANOS index in wintertime and 34 % in summertime. The net energy flux at the surface is found to be an important factor for the variation of sea level, explaining 35 % of sea-level variance in wintertime and a very small amount in summer. The freshwater flux could only explain 27 % of the variability in summertime and a negligible part in winter. In contrast to the NAO, the direct wind forcing associated with the SLP BANOS pattern does not lead to transport of water from the North Sea into the Baltic Sea in wintertime.

Dynamics of the transition zone in coastal zone color scanner-sensed ocean color in the North Pacific during oceanographic spring

NASA Technical Reports Server (NTRS)

Glover, David M.; Wroblewski, J. S.; Mcclain, Charles R.

1994-01-01

A transition zone in phytoplankton concentration running across the North Pacific basin at 30 deg to 40 deg north latitude corresponds to a basin-wide front in surface chlorophyll observed in a composite of coastal zone color scanner (CZCS) images for May, June, and July 1979-1986. This transition zone with low chlorophyll to the south and higher chlorophyll to the north can be simulated by a simple model of the concentration of phytoplankton, zooplankton, and dissolved nutrient (nitrate) in the surface mixed layer of the ocean applied to the North Pacific basin for the climatological conditions during oceanographic springtime (May, June, and July). The model is initialized with a 1 deg x 1 deg gridded estimate of wintertime (February, March, and April) mixed layer nitrate concentrations calculated from an extensive nutrient database and a similarly gridded mixed layer depth data set. Comparison of model predictions with CZCS data provides a means of evaluating the dynamics of the transition zone. We conclude that in the North Pacific, away from major boundary currents and coastal upwelling zones, wintertime vertical mixing determines the total nutrient available to the plankton ecosystem in the spring. The transition zone seen in basin-scale CZCS images is a reflection of the geographic variation in the wintertime mixed layer depth and the nitracline, leading to a latitudinal gradient in phytoplankton chlorophyll.

An Analysis of Wintertime Winds in Washington, D.C.

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

Berg, Larry K.; Allwine, K Jerry

This report consists of a description of the wintertime climatology of wind speed and wind direction around the National Mall in Washington, D.C. Meteorological data for this study were collected at Ronald Reagan Washington National Airport (Reagan National), Dulles International Airport (Dulles), and a set of surface meteorological stations that are located on a number of building tops around the National Mall. A five-year wintertime climatology of wind speed and wind direction measured at Reagan National and Dulles are presented. A more detailed analysis was completed for the period December 2003 through February 2004 using data gathered from stations locatedmore » around the National Mall, Reagan National, and Dulles. Key findings of our study include the following: * There are systematic differences between the wind speed and wind direction observed at Reagan National and the wind speed and wind direction measured by building top weather stations located in the National Mall. Although Dulles is located much further from the National Mall than Reagan National, there is better agreement between the wind speed and wind direction measured at Dulles and the weather stations in the National Mall. * When the winds are light (less than 3 ms-1 or 7 mph), there are significant differences in the wind directions reported at the various weather stations within the Mall. * Although the mean characteristics of the wind are similar at the various locations, significant, short-term differences are found when the time series are compared. These differences have important implications for the dispersion of airborne contaminants. In support of wintertime special events in the area of the National Mall, we recommend placing four additional meteorological instruments: three additional surface stations, one on the east bank of the Potomac River, one south of the Reflecting Pool (to better define the flow within the Mall), and a surface station near the Herbert C. Hoover Building; and wind-profiling instrument located along the southern edge of the National Mall to give measurements of the wind speed and direction as a function of height.« less

Application of change-point analysis to determine winter sleep patterns of the raccoon dog (Nyctereutes procyonoides) from body temperature recordings and a multi-faceted dietary and behavioral study of wintering.

PubMed

Mustonen, Anne-Mari; Lempiäinen, Terttu; Aspelund, Mikko; Hellstedt, Paavo; Ikonen, Katri; Itämies, Juhani; Vähä, Ville; Erkinaro, Jaakko; Asikainen, Juha; Kunnasranta, Mervi; Niemelä, Pekka; Aho, Jari; Nieminen, Petteri

2012-12-13

A multi-faceted approach was used to investigate the wintertime ecophysiology and behavioral patterns of the raccoon dog, Nyctereutes procyonoides, a suitable model for winter sleep studies. By utilizing GPS tracking, activity sensors, body temperature (Tb) recordings, change-point analysis (CPA), home range, habitat and dietary analyses, as well as fatty acid signatures (FAS), the impact of the species on wintertime food webs was assessed. The timing of passive bouts was determined with multiple methods and compared to Tb data analyzed by CPA. Raccoon dogs displayed wintertime mobility, and the home range sizes determined by GPS were similar or larger than previous estimates by radio tracking. The preferred habitats were gardens, shores, deciduous forests, and sparsely forested areas. Fields had close to neutral preference; roads and railroads were utilized as travel routes. Raccoon dogs participated actively in the food web and gained benefit from human activity. Mammals, plants, birds, and discarded fish comprised the most important dietary classes, and the consumption of fish could be detected in FAS. Ambient temperature was an important external factor influencing Tb and activity. The timing of passive periods approximated by behavioral data and by CPA shared 91% similarity. Passive periods can be determined with CPA from Tb recordings without the previously used time-consuming and expensive methods. It would be possible to recruit more animals by using the simple methods of data loggers and ear tags. Hunting could be used as a tool to return the ear-tagged individuals allowing the economical extension of follow-up studies. The Tb and CPA methods could be applied to other northern carnivores.

Application of change-point analysis to determine winter sleep patterns of the raccoon dog (Nyctereutes procyonoides) from body temperature recordings and a multi-faceted dietary and behavioral study of wintering

PubMed Central

2012-01-01

Background A multi-faceted approach was used to investigate the wintertime ecophysiology and behavioral patterns of the raccoon dog, Nyctereutes procyonoides, a suitable model for winter sleep studies. By utilizing GPS tracking, activity sensors, body temperature (Tb) recordings, change-point analysis (CPA), home range, habitat and dietary analyses, as well as fatty acid signatures (FAS), the impact of the species on wintertime food webs was assessed. The timing of passive bouts was determined with multiple methods and compared to Tb data analyzed by CPA. Results Raccoon dogs displayed wintertime mobility, and the home range sizes determined by GPS were similar or larger than previous estimates by radio tracking. The preferred habitats were gardens, shores, deciduous forests, and sparsely forested areas. Fields had close to neutral preference; roads and railroads were utilized as travel routes. Raccoon dogs participated actively in the food web and gained benefit from human activity. Mammals, plants, birds, and discarded fish comprised the most important dietary classes, and the consumption of fish could be detected in FAS. Ambient temperature was an important external factor influencing Tb and activity. The timing of passive periods approximated by behavioral data and by CPA shared 91% similarity. Conclusions Passive periods can be determined with CPA from Tb recordings without the previously used time-consuming and expensive methods. It would be possible to recruit more animals by using the simple methods of data loggers and ear tags. Hunting could be used as a tool to return the ear-tagged individuals allowing the economical extension of follow-up studies. The Tb and CPA methods could be applied to other northern carnivores. PMID:23237274

Wintertime ozone fluxes and profiles above a subalpine spruce-fir forest

Treesearch

Karl Zeller

2000-01-01

High rural concentrations of ozone (O3) are thought to be stratospheric in origin, advected from upwind urban sources, or photochemically generated locally by natural trace gas emissions. Ozone is known to be transported vertically downward from the above-canopy atmospheric surface layer and destroyed within stomata or on other biological and mineral surfaces. However...

Is Miscanthus a High Risk Biofuel Feedstock Prospect for the Upper Midwest US?

NASA Astrophysics Data System (ADS)

Kucharik, C. J.; VanLoocke, A. D.

2011-12-01

Miscanthus is a highly productive C4 perennial rhizomatous grass that is native to Southeast Asia, but its potential as a feedstock for cellulosic biofuel in the Midwest US is intriguing given extremely high productivity for low amounts of agrochemical inputs. However, Miscanthus x giganteus, a key variety currently studied is not planted from seed, but rather from rhizomes planted at a soil depth of 5 to 10 cm. Therefore, it is costly to establish on the basis of both time and money, making it a potentially risky investment in geographic regions that experience cold wintertime temperatures that can effectively kill the crop. The 50% kill threshold for M. giganteus rhizomes occurs when soil temperatures fall below -3.5C, which may contribute to a high risk of improper establishment during the first few seasons. Our first objective here was to study a historical, simulated reconstruction of daily wintertime soil temperatures at high spatial resolution (5 min) across the Midwest US from 1948-2007, and use this information to quantify the frequency that lethal soil temperature thresholds for Miscanthus were reached. A second objective was to investigate how the use of crop residues could impact wintertime soil temperatures. In this study, a dynamic agroecosystem model (Agro-IBIS) that has been modified to simulate Miscanthus growth and phenology was used in conjunction with high-resolution datasets of soil texture and daily gridded weather data. Model simulations suggest that across the states of North and South Dakota, Nebraska, Minnesota, Wisconsin, Michigan, and the northern half of Iowa, the kill threshold of -3.5C at a 10cm soil depth was reached in 70-95% of the simulation years. A boundary representing a 50% likelihood of reaching -3.5C at 10cm depth in any given year runs approximately from east central Colorado, thought northern Kansas and Missouri, through central Illinois, central Indiana, and central Ohio. An analysis of monthly mean 10cm soil temperatures illustrates that temperatures colder than the kill threshold generally exist in January and February north and west of a line running from central Nebraska to north central Illinois, through southeastern Wisconsin and northern lower Michigan. These results suggest that a bioclimatic limit to successful establishment might be positioned somewhere through the central portion of the Corn Belt, but this depends on how risk is defined in the future. Model simulations suggest that a significant warming trend of wintertime soil temperatures existed across the region; soil temperatures have increased 3 to 4C in the past 60 years at 10cm as well as to depths as great as 50 to 100cm across northern and western portions of the Midwest. This warming trend, in combination with the strategic use of straw and other crop residues may reduce the risk of failure of establishing Miscanthus x giganteus. However, any adaptive management will not completely eliminate the high risk of cold soil temperatures in regions that are currently being targeted to support cellulosic biofuel production in the next several decades.

COLD TEMPERATURE MOTOR VEHICLE EMISSIONS TESTING IN ALASKA

EPA Science Inventory

A motor vehicle emissions testing study was conducted in Anchorage and Fairbanks during the winter of 1998-99 to collect actual measurements of initial idle emission rates. The study was performed for a sample of 111 automobiles and light-duty trucks under cold wintertime ambient...

A possible cause of the AO polarity reversal from winter to summer in 2010 and its relation to hemispheric extreme summer weather

NASA Astrophysics Data System (ADS)

Otomi, Y.; Tachibana, Y.; Nakamura, T.

2012-12-01

In 2010, the Northern Hemisphere, in particular Russia, Europe and Japan, experienced an abnormally hot summer characterized by record-breaking warm temperatures and associated with a strongly positive Arctic Oscillation (AO). In contrast, in winter 2009/2010, the continent suffered from anomalously cold weather associated with a record-breaking negative AO. The winter-to-summer of the AO index during 2009/2010 evolved as follows: a strongly negative wintertime AO index continued until May, after which it abruptly changed, becoming strongly positive in July and continuing so until the beginning of August. The abrupt change of the AO index from strongly negative to strongly positive in 2010 thus corresponded to the change from the abnormally cold winter of 2009/2010 to the abnormally hot summer of 2010, which shows that the AO index is a good indicator of abnormal weather on a planetary-scale, and that extra-seasonal prediction of the AO is a key to long-term forecasting. In this study, we therefore aimed to examine the cause of the 2010 change in the AO index from strongly negative to strongly positive. We suggest that an oceanic memory of the strongly negative wintertime AO may have influenced the strongly positive summertime AO. The winter sea surface temperatures (SST) in the North Atlantic Ocean showed a tripolar anomaly pattern which is warm SST anomalies over the tropics and high latitudes and cold SST anomalies over the midlatitudes. The strongly negative wintertime AO would cause the warm SST anomaly in this region. The warm SST anomalies continued into summer 2010 because of the large oceanic heat capacity. In May and June, the heat flux anomaly changed from downward to upward in the tropics, and in July and August, the center of the upward anomaly moved westward. The area of the upward heat flux anomaly coincided with the area of the warm SST anomaly from May to August. The numerical model experiment showed that the tripolar SST pattern resulted in an anomalous height and wind pattern that caused a blocking high over Europe. The observed wave activity flux also seems to emanate from Europe. This midlatitude atmospheric response implies that strengthening of the positive geopotential anomalies over Europe was associated with the Atlantic tripolar SST anomaly. The positive geopotential anomaly in the area of the polar jet stream caused eastward propagation of Rossby waves, and the exceeding amplification of Rossby waves might have led to the formation of blocking anticyclones. As a consequence of these interactions, the positive AO pressure pattern can continue for a long time. Thus, a possible cause of the AO polarity reversal might be the "memory" of the negative winter AO in the North Atlantic Ocean, suggesting an interseasonal linkage of the AO in which the oceanic memory of a wintertime negative AO induces a positive AO in the following summer. Understanding of this interseasonal linkage may aid in the long-term prediction of such abnormal summer events. If this reversal pattern recurs, it might be possible to predict the summertime AO from the wintertime AO. Main parts of this study were published in Climatic Dynamics by Otomi et al, (2012).

Surface Formation and Preservation of Very-Low-Porosity Thin Crusts ( "Glazes") at the WAIS Divide Site, West Antarctica

NASA Astrophysics Data System (ADS)

Fegyveresi, J. M.; Alley, R. B.; Muto, A.; Spencer, M. K.; Orsi, A. J.

2014-12-01

Observations at the WAIS Divide site show that near-surface snow is strongly altered by weather-related processes, producing features that are recognizable in the ice core. Prominent reflective "glazed" surface crusts develop frequently during the summer. Observations during austral summers 2008-09 through 2012-13, supplemented by Automated Weather Station data with insolation sensors, documented formation of such crusts during relatively low-wind, low-humidity, clear-sky periods with intense daytime sunshine. After formation, such glazed surfaces typically developed cracks in a polygonal pattern with few-meter spacing, likely from thermal contraction at night. Cracking was commonest when several clear days occurred in succession, and was generally followed by surface hoar growth. Temperature and radiation observations showed that solar heating often warmed the near-surface snow above the air temperature, contributing to mass transfer favoring crust formation. Subsequent investigation of the WDC06A deep ice core revealed that preserved surface crusts were seen in the core at an average rate of ~4.3 ± 2 yr-1 over the past 5500 years. They are about 40% more common in layers deposited during summers than during winters. The total summertime crust frequency also covaried with site temperature, with more present during warmer periods. We hypothesize that the mechanism for glaze formation producing single-grain-thick very-low-porosity thin crusts (i.e. "glazes") involves additional in-filling of open pores. The thermal conductivity of ice greatly exceeds that of air, so heat transport in firn is primarily conductive. Because heat flow is primarily through the grain structure, for a temperature inversion (colder upper surface) beneath a growing thin crust at the upper surface, pores will be colder than interconnected grains, favoring mass transport into those pores. Transport may occur by vapor, surface, or volume diffusion, although vapor diffusion and surface transport in pre-melted films are likely to dominate. On-site wintertime observations have not been made, but crust formation during winter may be favored by greater wind-packing, large meteorologically-forced temperature changes reaching as high as -15oC in midwinter, and perhaps longer intervals of surface stability.

Modeling a Typical Winter-time Dust Event over the Arabian Peninsula and the Red Sea

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

Kalenderski, S.; Stenchikov, G.; Zhao, Chun

2013-02-20

We used WRF-Chem, a regional meteorological model coupled with an aerosol-chemistry component, to simulate various aspects of the dust phenomena over the Arabian Peninsula and Red Sea during a typical winter-time dust event that occurred in January 2009. The model predicted that the total amount of emitted dust was 18.3 Tg for the entire dust outburst period and that the two maximum daily rates were ~2.4 Tg/day and ~1.5 Tg/day, corresponding to two periods with the highest aerosol optical depth that were well captured by ground- and satellite-based observations. The model predicted that the dust plume was thick, extensive, andmore » mixed in a deep boundary layer at an altitude of 3-4 km. Its spatial distribution was modeled to be consistent with typical spatial patterns of dust emissions. We utilized MODIS-Aqua and Solar Village AERONET measurements of the aerosol optical depth (AOD) to evaluate the radiative impact of aerosols. Our results clearly indicated that the presence of dust particles in the atmosphere caused a significant reduction in the amount of solar radiation reaching the surface during the dust event. We also found that dust aerosols have significant impact on the energy and nutrient balances of the Red Sea. Our results showed that the simulated cooling under the dust plume reached 100 W/m2, which could have profound effects on both the sea surface temperature and circulation. Further analysis of dust generation and its spatial and temporal variability is extremely important for future projections and for better understanding of the climate and ecological history of the Red Sea.« less

Seasonal temperature variability and emergency hospital admissions for respiratory diseases: a population-based cohort study.

PubMed

Sun, Shengzhi; Laden, Francine; Hart, Jaime E; Qiu, Hong; Wang, Yan; Wong, Chit Ming; Lee, Ruby Siu-Yin; Tian, Linwei

2018-04-05

Climate change increases global mean temperature and changes short-term (eg, diurnal) and long-term (eg, intraseasonal) temperature variability. Numerous studies have shown that mean temperature and short-term temperature variability are both associated with increased respiratory morbidity or mortality. However, data on the impact of long-term temperature variability are sparse. We aimed to assess the association of intraseasonal temperature variability with respiratory disease hospitalisations among elders. We ascertained the first occurrence of emergency hospital admissions for respiratory diseases in a prospective Chinese elderly cohort of 66 820 older people (≥65 years) with 10-13 years of follow-up. We used an ordinary kriging method based on 22 weather monitoring stations in Hong Kong to spatially interpolate daily ambient temperature for each participant's residential address. Seasonal temperature variability was defined as the SD of daily mean summer (June-August) or winter (December-February) temperatures. We applied Cox proportional hazards regression with time-varying exposure of seasonal temperature variability to respiratory admissions. During the follow-up time, we ascertained 12 689 cases of incident respiratory diseases, of which 6672 were pneumonia and 3075 were COPD. The HRs per 1°C increase in wintertime temperature variability were 1.20 (95% CI 1.08 to 1.32), 1.15 (1.01 to 1.31) and 1.41 (1.15 to 1.71) for total respiratory diseases, pneumonia and COPD, respectively. The associations were not statistically significant for summertime temperature variability. Wintertime temperature variability was associated with higher risk of incident respiratory diseases. © 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.

A dynamical systems approach to studying midlatitude weather extremes

NASA Astrophysics Data System (ADS)

Messori, Gabriele; Caballero, Rodrigo; Faranda, Davide

2017-04-01

Extreme weather occurrences carry enormous social and economic costs and routinely garner widespread scientific and media coverage. The ability to predict these events is therefore a topic of crucial importance. Here we propose a novel predictability pathway for extreme events, by building upon recent advances in dynamical systems theory. We show that simple dynamical systems metrics can be used to identify sets of large-scale atmospheric flow patterns with similar spatial structure and temporal evolution on time scales of several days to a week. In regions where these patterns favor extreme weather, they afford a particularly good predictability of the extremes. We specifically test this technique on the atmospheric circulation in the North Atlantic region, where it provides predictability of large-scale wintertime surface temperature extremes in Europe up to 1 week in advance.

Challenges in modeling spatiotemporally varying phytoplankton blooms in the Northwestern Arabian Sea and Gulf of Oman

NASA Astrophysics Data System (ADS)

Sedigh Marvasti, S.; Gnanadesikan, A.; Bidokhti, A. A.; Dunne, J. P.; Ghader, S.

2016-02-01

Recent years have shown an increase in harmful algal blooms in the Northwest Arabian Sea and Gulf of Oman, raising the question of whether climate change will accelerate this trend. This has led us to examine whether the Earth System Models used to simulate phytoplankton productivity accurately capture bloom dynamics in this region - both in terms of the annual cycle and interannual variability. Satellite data (SeaWIFS ocean color) show two climatological blooms in this region, a wintertime bloom peaking in February and a summertime bloom peaking in September. On a regional scale, interannual variability of the wintertime bloom is dominated by cyclonic eddies which vary in location from one year to another. Two coarse (1°) models with the relatively complex biogeochemistry (TOPAZ) capture the annual cycle but neither eddies nor the interannual variability. An eddy-resolving model (GFDL CM2.6) with a simpler biogeochemistry (miniBLING) displays larger interannual variability, but overestimates the wintertime bloom and captures eddy-bloom coupling in the south but not in the north. The models fail to capture both the magnitude of the wintertime bloom and its modulation by eddies in part because of their failure to capture the observed sharp thermocline and/or nutricline in this region. When CM2.6 is able to capture such features in the Southern part of the basin, eddies modulate diffusive nutrient supply to the surface (a mechanism not previously emphasized in the literature). For the model to simulate the observed wintertime blooms within cyclones, it will be necessary to represent this relatively unusual nutrient structure as well as the cyclonic eddies. This is a challenge in the Northern Arabian Sea as it requires capturing the details of the outflow from the Persian Gulf - something that is poorly done in global models.

Man-made climatic changes in the Ganges basin

NASA Astrophysics Data System (ADS)

Adel, Miah M.

2002-06-01

Climate data pertaining to the Ganges basin in Bangladesh were analysed to find any climatic changes in the wake of the upstream water diversion by the Farakka Barrage. Whereas the diversions have been continuing from at least 30 international rivers upstream of Bangladesh, the diversion from the Ganges is the best known and has a wider coverage than all other diversions. The diversion reduced the Ganges' discharge through the delta by about 60% from a pre-diversion average value of 1932 m3 s-1, decreased water availability in flood plains, ponds, canals, and ditches by about 50%, dropped the groundwater table, and caused changes in surface features. It took about 5 years of diversions beyond the test run year of 1975 for the environment to react to set 1981 as the baseline year. During the post-baseline era: (1) heating degree days and cooling degree days were respectively 1.33 and 1.44 times more than their counterparts during the pre-baseline era; (2) the summertime and wintertime average temperatures were respectively 1 °C more and 0.5 °C less than the corresponding values during the pre-baseline era; (3) the mode 32 °C of summertime maximum temperatures was 1 °C higher and occurred 414 times more, and the mode 25 °C of wintertime temperature was 1 °C less and occurred 17 times less than the corresponding quantities during the pre-baseline era; (4) the average value of maximum relative humidity has increased by more than 2% and that of minimum relative humidity has dropped by the same amount; (5) the mode 95% and 70% of maximum and minimum relative humidity values have occurred 1322 times and 84 times more respectively than their pre-baseline counterparts; and (6) the frequency for 100 mm or more rainfall and the monthly average rainfalls have dropped by about 50% and 30% respectively. The solution to the climatic changes lies in the restoration of the virgin Ganges flow, dredging of the Ganges and its distributaries to remove shoals and siltation, and re-excavation of canals for water discharge to depleted surface water bodies to re-establish the lost wetland ecosystems. The findings are useful for climate modellers to predict the climatic changes due to changes in surface features, for policy makers of governments of riparian countries constructing dams/barrages on international rivers for unilateral diversion of water, and for donor agencies who finance such projects.

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.

Changes in wintertime pH and hydrography of the Gulf of Finland (Baltic Sea) with focus on depth layers.

PubMed

Almén, Anna-Karin; Glippa, Olivier; Pettersson, Heidi; Alenius, Pekka; Engström-Öst, Jonna

2017-04-01

We studied changes in sea water pH, temperature and salinity with focus on two depth layers, along the Gulf of Finland (the Baltic Sea) using long-term monitoring data from 1979 to 2015. Data from the most frequently sampled monitoring stations between western and eastern Gulf of Finland were used. The main result of the study reveals that pH has decreased both in surface and deep-water in the western Gulf of Finland with values ranging between -0.005 and -0.008 units year -1 . We also demonstrate a rise in temperature (~2 °C) and decrease in salinity (~-0.7 g kg -1 ) at several stations over the last 36 years. In general, the changes are shown to be more pronounced in the western part of the gulf. This paper also stresses the importance of improving the sampling frequency and quality of monitoring measurements.

Precipitation structure in the Sierra Nevada of California during winter

USGS Publications Warehouse

Pandey, G.R.; Cayan, D.R.; Georgakakos, K.P.

1999-01-01

Influences of upper air characteristics along the coast of California upon wintertime (November-April) precipitation in the Sierra Nevada are investigated. Precipitation events in the Sierra Nevada region occur mostly during wintertime, irrespective of station location (leeside or wihdside) and elevation. Most precipitation episodes in the region are associated with moist southwesterly winds (coming from the southwest direction) and also tend to occur when the 700-mbar temperature at the upwind direction is close to -2??C. This favored wind direction and temperature signify the importance of both moisture transport and orographic lifting in augmenting precipitation in the region. By utilizing the observed dependency of the precipitation upon the upper air conditions, a linear model is formulated to quantify the precipitation observed at different sites as a function of moisture transport. The skill of the model increases with timescale of aggregation, reaching more than 50% variance explained at an aggregation period of 5-7 days. This indicates that upstream air moisture transport can be used to estimate the precipitation totals in the Sierra Nevada region. Copyright 1999 by the American Geophysical Union.

A Comprehensive Breath Plume Model for Disease Transmission via Expiratory Aerosols

NASA Astrophysics Data System (ADS)

Halloran, S. K.; Wexler, A. S.; Ristenpart, W. D.

2012-11-01

The peak in influenza incidence during wintertime represents a longstanding unresolved scientific question. One hypothesis is that the efficacy of airborne transmission via aerosols is increased at low humidity and temperature, conditions that prevail in wintertime. Recent experiments with guinea pigs suggest that transmission is indeed maximized at low humidity and temperature, a finding which has been widely interpreted in terms of airborne influenza virus survivability. This interpretation, however, neglects the effect of the airflow on the transmission probability. Here we provide a comprehensive model for assessing the probability of disease transmission via expiratory aerosols between test animals in laboratory conditions. The spread of aerosols emitted from an infected animal is modeled using dispersion theory for a homogeneous turbulent airflow. The concentration and size distribution of the evaporating droplets in the resulting ``Gaussian breath plume'' are calculated as functions of downstream position. We demonstrate that the breath plume model is broadly consistent with the guinea pig experiments, without invoking airborne virus survivability. Moreover, the results highlight the need for careful characterization of the airflow in airborne transmission experiments.

The North Atlantic Oscillation Reconstructed at Bermuda for 220 Years Using Sr/Ca Ratios in Diploria labyrinthiformis (brain coral)

NASA Astrophysics Data System (ADS)

Goodkin, N. F.; Hughen, K. A.; Cohen, A. L.; Curry, W. B.; Doney, S. C.

2006-12-01

The North Atlantic Oscillation (NAO) is a meridional oscillation in atmospheric mass measured by pressure anomalies between Iceland (65°N, 23°W) and the Azores (38°N, 26°W) (Hurrell, 1995). Changes between the positive and negative phase of the NAO strongly influence weather patterns across the US, Europe and the Middle East. A shift in recent decades toward a sustained positive NAO has raised questions about the influence of greenhouse gas emissions on this system. Unfortunately, instrumental records are too short to identify the natural baseline variability of the NAO, and NAO reconstructions generally encompass only land-based proxies, excluding ocean processes. Winter-time sea surface temperatures (SST) in the Sargasso Sea have previously been shown to correlate to the NAO (Visbeck et al., 2001), and thus a long winter SST record based on proxy data could be used to reconstruct NAO variability back in time. Here we present an annually resolved winter-time strontium to calcium ratio (Sr/Ca) record from a 220-year old brain coral (Diploria labyrinthiformis) collected from the south shore of Bermuda. Brain coral is prevalent in Bermuda and shows distinct annual banding in its skeleton providing precise age models. Winter-time coral Sr/Ca has previously been shown to accurately record winter SST free from growth rate influences (Goodkin et al., 2005), and that relationship is confirmed here. Cross-spectral analysis between winter-time coral Sr/Ca and four instrumental and proxy records of the NAO (Hurrell, 1995, Jones et al., 1997, Luterbacher et al., 2001, Cook et al., 2002) show two frequencies of coherence with >95% confidence. At periods greater than 20 years and between 3 and 5 years, the coral Sr/Ca effectively captures the NAO variability. Filtering the coral record to these frequencies and comparing to the instrumental and proxy records, including another marine-based NAO reconstruction from the North and Norwegian Seas (Schoene et al., 2003), show strong agreement and provide information about the differences between high and low frequency responses to the NAO. At high frequencies, SST at Bermuda shows a positive correlation to the NAO, as predicted by the tri-pole SST response (Visbeck et al., 2001), and succeeds well at capturing amplitude variability. At low frequencies, however, Bermuda SST shows a negative correlation to the NAO, different than the response predicted by the high frequency tri-pole pattern. One possible explanation for this shift is a response to changes in the meridional overturning circulation (MOC), which is believed to show variability at lower frequencies (Curry et al., 2003) and which may be driving changes in both SST and the NAO. Over 50 years during the late 20th century warming (1950-1999), the amplitude of the Sr/Ca-based NAO record at 3-5 year periods is 20% greater than that found during an equivalent interval at the end of the LIA (1800- 1849). Low-frequency (20-50 year) variability also appears larger during the second half of the 20th century, compared to the LIA. These results indicate a change in NAO variability at different mean temperatures, with larger amplitude changes during warmer climates. However, a sustained positive NAO during the late LIA does not appear to support the hypothesis of a linear relationship between mean NAO and mean hemispheric temperature, as observed during the late 20th century warming.

The role of precipitation in aerosol-induced changes in northern hemisphere wintertime stationary waves

NASA Astrophysics Data System (ADS)

Lewinschal, A.; Ekman, A. M. L.; Körnich, H.

2012-04-01

Aerosol particles have a considerable impact on the energy budget of the atmosphere due to their ability to scatter and absorb incoming solar radiation. Persistent particle emissions in certain regions of the world have lead to quasi-permanent aerosol forcing patterns. This spatially varying forcing pattern has the potential to modify temperature gradients that in turn alter pressure gradients and the atmospheric circulation. This study focuses on the effect of aerosol direct radiative forcing on northern hemisphere wintertime stationary waves. A global general circulation model based on the ECMWF operational forecast model is applied (EC-Earth). Aerosols are prescribed as monthly mean mixing ratios of sulphate, black carbon, organic carbon, dust and sea salt. Only the direct aerosol effect is considered. The climatic change is defined as the difference between model simulations using present-day and pre-industrial concentrations of aerosol particles. Data from 40-year long simulations using a coupled ocean-atmosphere model system are used. In EC-Earth, the high aerosol loading over South Asia leads to a surface cooling, which appears to enhance the South Asian winter monsoon and weaken the Indian Ocean Walker circulation. The anomalous Walker circulation leads to changes in tropical convective precipitation and consequent changes in latent heat release which effectively acts to generate planetary scale waves propagating into the extra-tropics. Using a steady-state linear model we verify that the aerosol-induced anomalous convective precipitation is a crucial link between the wave changes and the direct aerosol radiative forcing.

Linking a sea level pressure anomaly dipole over North America to the central Pacific El Niño

NASA Astrophysics Data System (ADS)

Ding, Ruiqiang; Li, Jianping; Tseng, Yu-heng; Sun, Cheng; Zheng, Fei

2017-08-01

This study demonstrates the close connection between the north-south dipole pattern of sea level pressure anomalies over northeastern North America to the western tropical North Atlantic, referred to as the North American dipole (NAD), and the central Pacific (CP)-type El Niño a year later. In contrast to other ENSO precursors, such as the North Pacific Oscillation (NPO) and Pacific-North America (PNA) pattern, the NAD appears more closely related to the CP-type El Niño than to the eastern Pacific (EP)-type El Niño, indicating that the NAD may serve as a unique precursor for the CP El Niño. The wintertime NAD induces sea surface temperature anomalies in the northern tropical Atlantic (NTA), which subsequently play an important role in developing the CP El Niño-like pattern in the tropical Pacific over the course of the following year. It appears that the NAD influence on CP El Niño involves air-sea interaction over several major basins, including the subtropical/tropical Pacific and the NTA. Additional analysis indicates that the correlation of either the NAD index or the NPO index with the CP El Niño state a year later depends on the status of the other index. When the wintertime NAD index is of the opposite sign to the simultaneous NPO index, the correlation of the NAD or NPO index with the Niño4 index becomes much weaker.

Differential responses of invasive and native plants to warming with simulated changes in diurnal temperature ranges

PubMed Central

Chen, Bao-Ming; Gao, Yang; Liao, Hui-Xuan

2017-01-01

Abstract Although many studies have documented the effects of global warming on invasive plants, little is known about whether the effects of warming on plant invasion differ depending on the imposed change in different diurnal temperature ranges (DTR). We tested the impact of warming with DTR change on seed germination and seedling growth of eight species in the family Asteraceae. Four of these are invasive (Eupatorium catarium, Mikania micrantha, Biodens pilosa var. radiate, Ageratum conyzoides) in China, and four are native (Sonchus arvensis, Senecios candens, Pterocypsela indica, Eupatorium fortunei). Four temperature treatments were set in growth chambers (three warming by 3 °C with different DTRs and control), and experiments were run to mimic wintertime and summertime conditions. The control treatment (Tc) was set to the mean temperature for the corresponding time of year, and the three warming treatments were symmetric (i.e. equal night-and-day) (DTRsym), asymmetric warming with increased (DTRinc) and decreased (DTRdec) DTR. The warming treatments did not affect seed germination of invasive species under any of the conditions, but DTRsym and DTRinc increased seed germination of natives relative to the control, suggesting that warming may not increase success of these invasive plant species via effects on seed germination of invasive plants relative to native plants. The invasive plants had higher biomass and greater stem allocation than the native ones under all of the warming treatments. Wintertime warming increased the biomass of the invasive and wintertime DTRsym and DTRinc increased that of the native plants, whereas summertime asymmetric warming decreased the biomass of the invasives but not the natives. Therefore, warming may not facilitate invasion of these invasive species due to the suppressive effects of summertime warming (particularly the asymmetric warming) on growth. Compared with DTRsym, DTRdec decreased the biomass of both the invasive and native plants, while the asymmetric summer warming treatments (DTRinc and DTRdec) decreased the biomass of the invasive but not the native plants. In addition, wintertime DTRinc did not enhance the biomass of all the plants relative to DTRsym. Our results were obtained in an unrealistic setting; the growth conditions in chambers (e.g. low light, low herbivory, no competition) are quite different from natural conditions (high light, normal herbivory and competition), which may influence the effects of warming on the seedling establishment and growth of both invasive and native plants. Nonetheless, our work highlights the importance of asymmetric warming, particularly in regards to the comparison with the effects of symmetric warming on both invasive and native plants. Conclusions regarding the effects of future warming should be made cautiously because warming with different DTRs may suggest different implications for invasion, and effects of warming may be different in different seasons. PMID:28775830

A new perspective on origin of the East Sea Intermediate Water: Observations of Argo floats

NASA Astrophysics Data System (ADS)

Park, JongJin; Lim, Byunghwan

2018-01-01

The East Sea Intermediate Water (ESIW), defined as the salinity minimum in the East Sea (hereafter ES) (Sea of Japan), is examined with respect to its overall characteristics and its low salinity origin using historical Argo float data from 1999 to 2015. Our findings suggest that the ESIW is formed in the western Japan Basin (40-42°N, 130-133°E), especially west of the North Korean front in North Korean waters, where strong negative surface wind stress curl resides in wintertime. The core ESIW near the formation site has temperatures of 3-4 °C and less than 33.98 psu salinity, warmer and fresher than that in the southern part of the ES. In order to trace the origin of the warmer and fresher water at the sea surface in winter, we analyzed the data in three different ways: (1) spatial distribution of surface water properties using monthly climatology from the Argo float data, (2) seasonal variation of heat and salt contents at the formation site, and (3) backtracking of surface drifter trajectories. Based on these analyses, it is likely that the warmer and fresher surface water properties found in the ESIW formation site are attributed to the low-salinity surface water advected from the southern part of the ES in autumn.

Impact of Climate Change on Siberian High and Wintertime Air Pollution in China in Past Two Decades

NASA Astrophysics Data System (ADS)

Zhao, Shuyu; Feng, Tian; Tie, Xuexi; Long, Xin; Li, Guohui; Cao, Junji; Zhou, Weijian; An, Zhisheng

2018-02-01

China has suffered severe air pollutions during wintertime as national industrialization and urbanization have been increasingly developed in the past decades. Recent studies suggest that climate change has important impacts on extreme haze events in northern China. This study uses reanalysis datasets to analyze the trend and variability of Siberian High (SiH) intensity, and its relationship with the Arctic temperature and sea ice cover (SIC) in past two decades. The results show that Arctic is warming accompanied by a rapid decline of SIC, while Eurasia is cooling and SiH intensity is gradually enhancing. The statistics illustrates that the SiH has a significantly positive correlation to the temperature (R = 0.70), and a significant anticorrelation to the SIC (R = -0.69), and this is because the warming Arctic and the reducing SIC enhanced the SiH. The enhanced SiH leads to strengthened northerly winds in the North China Plain (NCP). The WRF-Chem model calculation reveals the strengthened northerly winds during the stronger SiH period in January 2016 produce a significant decrease in PM2.5 (particulate matter with aerodynamic diameter less than 2.5 µm) concentrations by 100-200 µg m-3 than that during the weaker one in January 2013. A sensitivity calculation figures out the reduction of PM2.5 concentrations due to a decrease of 50% in emissions is comparable to changes from the weak SiH condition to the strong SiH condition, suggesting that extreme climate variability in the past few years could have an equivalent impact as a consequence of a large emission reduction on wintertime air pollution in the NCP.

75 FR 59090 - Approval and Promulgation of Implementation Plans and Designation of Areas for Air Quality...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-27

.... These revisions include the suspension of a local wintertime cleaner burning gasoline rule, and the relaxation of a State rule governing wintertime gasoline in Clark County. EPA's proposed approval of the... limit in the State wintertime gasoline rule, if necessary, to implement the related contingency measure...

Effect of the tropical Pacific and Indian Ocean warming since the late 1970s on wintertime Northern Hemispheric atmospheric circulation and East Asian climate interdecadal changes

NASA Astrophysics Data System (ADS)

Chu, Cuijiao; Yang, Xiu-Qun; Sun, Xuguang; Yang, Dejian; Jiang, Yiquan; Feng, Tao; Liang, Jin

2018-04-01

Observation reveals that the tropical Pacific-Indian Ocean (TPIO) has experienced a pronounced interdecadal warming since the end of the 1970s. Meanwhile, the wintertime midlatitude Northern Hemispheric atmospheric circulation and East Asian climate have also undergone substantial interdecadal changes. The effect of the TPIO warming on these interdecadal changes are identified by a suite of AMIP-type atmospheric general circulation model experiments in which the model is integrated from September 1948 to December 1999 with prescribed historical, observed realistic sea surface temperature (SST) in a specific region and climatological SST elsewhere. Results show that the TPIO warming reproduces quite well the observed Northern Hemispheric wintertime interdecadal changes, suggesting that these interdecadal changes primarily originate from the TPIO warming. However, each sub-region of TPIO has its own distinct contribution. Comparatively, the tropical central-eastern Pacific (TCEP) and tropical western Pacific (TWP) warming makes dominant contributions to the observed positive-phase PNA-like interdecadal anomaly over the North Pacific sector, while the tropical Indian Ocean (TIO) warming tends to cancel these contributions. Meanwhile, the TIO and TWP warming makes dominant contributions to the observed positive NAO-like interdecadal anomaly over the North Atlantic sector as well as the interdecadal anomalies over the Eurasian sector, although the TWP warming's contribution is relatively small. These remote responses are directly attributed to the TPIO warming-induced tropical convection, rainfall and diabatic heating increases, in which the TIO warming has the most significant effect. Moreover, the TPIO warming excites a Gill-type pattern anomaly over the tropical western Pacific, with a low-level anticyclonic circulation anomaly over the Philippine Sea. Of three sub-regions, the TIO warming dominates such a pattern, although the TWP warming tends to cancel this effect. The anticyclonic circulation anomaly intensifies the southwesterly flow that transfers more moisture from the Bay of Bengal to East Asia and considerably increases the winter precipitation over the southern East Asia. This is strongly supported by the observational fact that there has been a significant interdecadal increase of winter precipitation over the southern China since the end of the 1970s.

Weather types across the Caribbean basin and their relationship with rainfall and sea surface temperature

NASA Astrophysics Data System (ADS)

Moron, Vincent; Gouirand, Isabelle; Taylor, Michael

2016-07-01

Eight weather types (WTs) are computed over 98.75°W-56.25°W, 8.75°N-31.25°N using cluster analysis of daily low-level (925 hPa) winds and outgoing longwave radiation, without removing the mean annual cycle, by a k-means algorithm from 1979 to 2013. The WTs can be firstly interpreted as snapshots of the annual cycle with a clear distinction between 5 "wintertime" and 3 "summertime" WTs, which account together for 70 % of the total mean annual rainfall across the studied domain. The wintertime WTs occur mostly from late November to late April and are characterized by varying intensity and location of the North Atlantic subtropical high (NASH) and transient synoptic troughs along the northern edge of the domain. Large-scale subsidence dominates the whole basin but rainfall can occur over sections of the basin, especially on the windward shores of the troughs associated with the synoptic waves. The transition between wintertime and summertime WTs is rather abrupt, especially in May. One summertime WT (WT 4) is prevalent in summer, and almost exclusive around late July. It is characterized by strong NASH, fast Caribbean low level jet and rainfall mostly concentrated over the Caribbean Islands, the Florida Peninsula, the whole Central America and the tropical Eastern Pacific. The two remaining summertime WTs display widespread rainfall respectively from Central America to Bermuda (WT 5) and over the Eastern Caribbean (WT 6). Both WTs combine reduced regional scale subsidence and weaker Caribbean low-level jet relatively to WT 4. The relationships between WT frequency and El Niño Southern Oscillation (ENSO) events are broadly linear. Warm central and eastern ENSO events are associated with more WT 4 (less WT 5-6) during boreal summer and autumn (0) while this relationship is reversed during boreal summer (+1) for central events only. In boreal winter, the largest anomalies are observed for two WTs consistent with negative (WT 2) and positive (WT 8) phases of the North Atlantic Oscillation; more (less) WT 2 and less (more) WT 8 than usually occur from January to early April during warm (cold) ENSO events, the strongest anomalies being recorded during eastern events. Multinomial logistic regression is used to hindcast the 11-day low-pass filtered occurrence of WTs from local (Caribbean Sea and Gulf of Mexico) and remote (Eastern and Central Tropical Pacific) sea surface temperatures (SSTs). In boreal summer, the interannual variability of the seasonal occurrence of WTs 4-6 is well hindcast when at least the Caribbean Sea and Eastern Tropical Pacific are included as predictors with anomalously warm (cold) SSTs over the Caribbean Sea (Eastern Tropical Pacific) being related to more WT 5-6 and less WT 4 and vice-versa. Using antecedent SST to forecast WT frequency shows that the SST forcing is negligible at the start of boreal summer and increases toward its end.

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.

Aircraft-based Observations and Modeling of Wintertime Submicron Aerosol Composition over the Northeastern U.S.

NASA Astrophysics Data System (ADS)

Shah, V.; Jaegle, L.; Schroder, J. C.; Campuzano-Jost, P.; Jimenez, J. L.; Guo, H.; Sullivan, A.; Weber, R. J.; Green, J. R.; Fiddler, M.; Bililign, S.; Lopez-Hilfiker, F.; Lee, B. H.; Thornton, J. A.

2017-12-01

Submicron aerosol particles (PM1) remain a major air pollution concern in the urban areas of northeastern U.S. While SO2 and NOx emission controls have been effective at reducing summertime PM1 concentrations, this has not been the case for wintertime sulfate and nitrate concentrations, suggesting a nonlinear response during winter. During winter, organic aerosol (OA) is also an important contributor to PM1 mass despite low biogenic emissions, suggesting the presence of important urban sources. We use aircraft-based observations collected during the Wintertime INvestigation of Transport, Emissions and Reactivity (WINTER) campaign (Feb-March 2015), together with the GEOS-Chem chemical transport model, to investigate the sources and chemical processes governing wintertime PM1 over the northeastern U.S. The mean observed concentration of PM1 between the surface and 1 km was 4 μg m-3, about 30% of which was composed of sulfate, 20% nitrate, 10% ammonium, and 40% OA. The model reproduces the observed sulfate, nitrate and ammonium concentrations after updates to HNO3 production and loss, SO2 oxidation, and NH3 emissions. We find that 65% of the sulfate formation occurs in the aqueous phase, and 55% of nitrate formation through N2O5 hydrolysis, highlighting the importance of multiphase and heterogeneous processes during winter. Aqueous-phase sulfate production and the gas-particle partitioning of nitrate and ammonium are affected by atmospheric acidity, which in turn depends on the concentration of these species. We examine these couplings with GEOS-Chem, and assess the response of wintertime PM1 concentrations to further emission reductions based on the U.S. EPA projections for the year 2023. For OA, we find that the standard GEOS-Chem simulation underestimates the observed concentrations, but a simple parameterization developed from previous summer field campaigns is able to reproduce the observations and the contribution of primary and secondary OA. We find that residential wood combustion accounts for about 25% of the OA, while secondary production from urban anthropogenic VOCs accounts for the rest. We examine how OA concentrations may change as a result of changing emissions for the year 2023.

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.

Extreme cyclone events in the Arctic: Wintertime variability and trends

NASA Astrophysics Data System (ADS)

Rinke, A.; Maturilli, M.; Graham, R. M.; Matthes, H.; Handorf, D.; Cohen, L.; Hudson, S. R.; Moore, J. C.

2017-12-01

Extreme cyclone events often occur during Arctic winters, and are of concern as they transport heat and moisture into the Arctic, which is associated with mixed-phase clouds and increased longwave downward radiation, and can cause temperatures to rise above freezing resulting in wintertime sea-ice melting or retarded sea-ice growth. With Arctic amplification and associated reduced sea-ice cover and warmer sea surface temperatures, the occurrence of extreme cyclones events could be a plausible scenario. We calculate the spatial patterns, and changes and trends of the number of extreme cyclone events in the Arctic based on ERA-Interim six-hourly sea level pressure (SLP) data for winter (November-February) 1979-2015. Further, we analyze the SLP data from the Ny-Ålesund station for the same 37 year period. We define an extreme cyclone event by an extreme low central pressure (SLP below 985 hPa, which is the 5th percentile of the Ny-Ålesund/N-ICE2015 SLP data). Typically 20-40 extreme cyclone events (sometimes called `weather bombs') occur in the Arctic North Atlantic per winter season, with an increasing trend of 6 events/decade, according to the Ny-Ålesund data. This increased frequency of extreme cyclones drive considerable warming in that region, consistent with the observed significant winter warming of 3 K/decade. The positive winter trend in extreme cyclones is dominated by a positive monthly trend of about 3-4 events/decade in November-December, due mainly to an increasing persistence of extreme cyclone events. A negative trend in January opposes this, while there is no significant trend in February. We relate the regional patterns of the trend in extreme cyclones to anomalously low sea-ice conditions in recent years, together with associated large-scale atmospheric circulation changes such as "blocking-like" circulation patterns (e.g. Scandinavian blocking in December and Ural blocking during January-February).

Elevated increases in human-perceived temperature under climate warming

NASA Astrophysics Data System (ADS)

Li, Jianfeng; Chen, Yongqin David; Gan, Thian Yew; Lau, Ngar-Cheung

2018-01-01

Changes in air temperature (AT), humidity and wind speed (Wind) affect apparent temperature (AP), the human-perceived equivalent temperature1-3. Here we show that under climate warming, both reanalysis data sets and Global Climate Model simulations indicate that AP has increased faster than AT over land. The faster increase in AP has been especially significant over low latitudes and is expected to continue in the future. The global land average AP increased at 0.04 °C per decade faster than AT before 2005. This trend is projected to increase to 0.06 °C (0.03-0.09 °C; minimum and maximum of the ensemble members) per decade and 0.17 °C (0.12-0.25 °C) per decade under the Representative Concentration Pathway 4.5 scenario (RCP4.5) and RCP8.5, respectively, and reduce to 0.02 °C (0-0.03 °C) per decade under RCP2.6 over 2006-2100. The higher increment in AP in summer daytime is more remarkable than in winter night-time and is most prominent over low latitudes. The summertime increases in AT-based thermal discomfort are projected to balance the wintertime decreases in AT-based discomfort over low and middle latitudes, while the summertime increases in AP-based thermal discomfort are expected to outpace the wintertime decreases in AP-based thermal discomfort. Effective climate change mitigation efforts to achieve RCP2.6 can considerably alleviate the faster increase in AP.

A Comprehensive Breath Plume Model for Disease Transmission via Expiratory Aerosols

PubMed Central

Halloran, Siobhan K.; Wexler, Anthony S.; Ristenpart, William D.

2012-01-01

The peak in influenza incidence during wintertime in temperate regions represents a longstanding, unresolved scientific question. One hypothesis is that the efficacy of airborne transmission via aerosols is increased at lower humidities and temperatures, conditions that prevail in wintertime. Recent work with a guinea pig model by Lowen et al. indicated that humidity and temperature do modulate airborne influenza virus transmission, and several investigators have interpreted the observed humidity dependence in terms of airborne virus survivability. This interpretation, however, neglects two key observations: the effect of ambient temperature on the viral growth kinetics within the animals, and the strong influence of the background airflow on transmission. Here we provide a comprehensive theoretical framework for assessing the probability of disease transmission via expiratory aerosols between test animals in laboratory conditions. The spread of aerosols emitted from an infected animal is modeled using dispersion theory for a homogeneous turbulent airflow. The concentration and size distribution of the evaporating droplets in the resulting “Gaussian breath plume” are calculated as functions of position, humidity, and temperature. The overall transmission probability is modeled with a combination of the time-dependent viral concentration in the infected animal and the probability of droplet inhalation by the exposed animal downstream. We demonstrate that the breath plume model is broadly consistent with the results of Lowen et al., without invoking airborne virus survivability. The results also suggest that, at least for guinea pigs, variation in viral kinetics within the infected animals is the dominant factor explaining the increased transmission probability observed at lower temperatures. PMID:22615902

Differential responses of invasive and native plants to warming with simulated changes in diurnal temperature ranges.

PubMed

Chen, Bao-Ming; Gao, Yang; Liao, Hui-Xuan; Peng, Shao-Lin

2017-07-01

Although many studies have documented the effects of global warming on invasive plants, little is known about whether the effects of warming on plant invasion differ depending on the imposed change in different diurnal temperature ranges (DTR). We tested the impact of warming with DTR change on seed germination and seedling growth of eight species in the family Asteraceae. Four of these are invasive ( Eupatorium catarium , Mikania micrantha , Biodens pilosa var. radiate , Ageratum conyzoides ) in China, and four are native ( Sonchus arvensis , Senecios candens , Pterocypsela indica , Eupatorium fortunei ). Four temperature treatments were set in growth chambers (three warming by 3 °C with different DTRs and control), and experiments were run to mimic wintertime and summertime conditions. The control treatment ( T c ) was set to the mean temperature for the corresponding time of year, and the three warming treatments were symmetric (i.e. equal night-and-day) (DTR sym ), asymmetric warming with increased (DTR inc ) and decreased (DTR dec ) DTR. The warming treatments did not affect seed germination of invasive species under any of the conditions, but DTR sym and DTR inc increased seed germination of natives relative to the control, suggesting that warming may not increase success of these invasive plant species via effects on seed germination of invasive plants relative to native plants. The invasive plants had higher biomass and greater stem allocation than the native ones under all of the warming treatments. Wintertime warming increased the biomass of the invasive and wintertime DTR sym and DTR inc increased that of the native plants, whereas summertime asymmetric warming decreased the biomass of the invasives but not the natives. Therefore, warming may not facilitate invasion of these invasive species due to the suppressive effects of summertime warming (particularly the asymmetric warming) on growth. Compared with DTR sym , DTR dec decreased the biomass of both the invasive and native plants, while the asymmetric summer warming treatments (DTR inc and DTR dec ) decreased the biomass of the invasive but not the native plants. In addition, wintertime DTR inc did not enhance the biomass of all the plants relative to DTR sym . Our results were obtained in an unrealistic setting; the growth conditions in chambers (e.g. low light, low herbivory, no competition) are quite different from natural conditions (high light, normal herbivory and competition), which may influence the effects of warming on the seedling establishment and growth of both invasive and native plants. Nonetheless, our work highlights the importance of asymmetric warming, particularly in regards to the comparison with the effects of symmetric warming on both invasive and native plants. Conclusions regarding the effects of future warming should be made cautiously because warming with different DTRs may suggest different implications for invasion, and effects of warming may be different in different seasons.

Assessing the Urban Heat Island Effect Across Biomes in the Continental USA Using Landsat and MODIS

NASA Technical Reports Server (NTRS)

Imhoff, Marc L.; Bounoua, L.; Zhang, Ping; Wolfe, Robert

2011-01-01

Impervious surface area (ISA) from the Landsat TM and land surface temperature (LST) from MODIS averaged over three annual cycles (2003-2005) are used in a spatial analysis to assess the urban heat island (UHI) skin temperature amplitude and its relationship to development intensity, size, and ecological setting for 38 of the most populous cities in the continental United States. Development intensity zones based on %ISA are defined across urban gradients and used to stratify sampling of LST and NDVI. We find that ecological context significantly influences the amplitude of summer daytime UHI (urban - rural temperature difference) with the largest 8 C (average) for cities built in mixed forest biomes. For all cities ISA is the primary driver for increase in temperature explaining 70% of the total variance. Annually, urban areas are warmer than the non-urban fringe by 2.9 C, except in biomes with arid and semiarid climates. The average amplitude of the UHI is asymmetric with a 4.3 C difference in summer and 1.3 C in winter. In desert environments, UHI's point to a possible heat sink effect. Results show that the urban heat island amplitude increases with city size and is seasonally asymmetric for a large number of cities across most biomes. The implications are that for urban areas developed within forested ecosystems the summertime UHI can be quite high relative to the wintertime UHI suggesting that the residential energy consumption required for summer cooling is likely to increase with urban growth within those biomes.

The Low-Frequency Variability of the Tropical Atlantic Ocean

NASA Technical Reports Server (NTRS)

Haekkinen, Sirpa; Mo, Kingtse C.; Koblinsky, Chester J. (Technical Monitor)

2001-01-01

Upper ocean temperature variability in the tropical Atlantic is examined from the Comprehensive Ocean Atmosphere Data Set (COADS) as well as from an ocean model simulation forced by COADS anomalies appended to a monthly climatology. Our findings are as follows: Only the sea surface temperatures (SST) in the northern tropics are driven by heat fluxes, while the southern tropical variability arises from wind driven ocean circulation changes. The subsurface temperatures in the northern and southern tropics are found to have a strong linkage to buoyancy forcing changes in the northern North Atlantic. Evidence for Kelvin-like boundary wave propagation from the high latitudes is presented from the model simulation. This extratropical influence is associated with wintertime North Atlantic Oscillation (NAO) forcing and manifests itself in the northern and southern tropical temperature anomalies of the same sign at depth of 100-200 meters as result of a Rossby wave propagation away from the eastern boundary in the wake of the boundary wave passage. The most apparent association of the southern tropical sea surface temperature anomalies (STA) arises with the anomalous cross-equatorial winds which can be related to both NAO and the remote influence from the Pacific equatorial region. These teleconnections are seasonal so that the NAO impact on the tropical SST is the largest it mid-winter but in spring and early summer the Pacific remote influence competes with NAO. However, NAO appears to have a more substantial role than the Pacific influence at low frequencies during the last 50 years. The dynamic origin of STA is indirectly confirmed from the SST-heat flux relationship using ocean model experiments which remove either anomalous wind stress forcing or atmospheric forcing anomalies contributing to heat exchange.

Wintertime Phytoplankton Blooms in the Western Equatorial Indian Ocean Associated With the Madden-Julian Oscillation

NASA Astrophysics Data System (ADS)

Liao, Xiaomei; Du, Yan; Zhan, Haigang; Wang, Tianyu; Feng, Ming

2017-12-01

This study investigated boreal wintertime phytoplankton blooms in the western equatorial Indian Ocean (WEIO) and the underlying physical mechanisms. The Sea viewing Wide field of View sensor (SeaWiFS) chlorophyll-a (Chla) concentrations show that phytoplankton blooms occur in the WEIO during December-March. The development of these blooms is not only a seasonal process but also consists of 2-3 intraseasonal events induced by the Madden-Julian Oscillation (MJO). During a typical intraseasonal event, enhanced cross-equatorial wind induces strong upwelling and ocean mixing, thus increasing the supply of nutrients to the surface in equatorial regions. Argo profiles clearly show various responses to the intraseasonal wind bursts, including shoaling of the thermocline and deepening of the mixed layer. Further analysis reveals that the former is the dominant mechanism for the blooms along the equator, while the latter controls the high Chla concentrations off the coast of Somalia. Surface ocean circulations not only account for the blooms south of the equator but also modulate the thermocline depth in the WEIO. The shallower thermocline during the early period of the northeast monsoon season provides favorable conditions for a stronger Chla response to intraseasonal forcing.

The Eurasia-North Pacific Oscillation in atmospheric mass variations independent of both IHO and AO and its possible impacts on winter climate

NASA Astrophysics Data System (ADS)

Zhang, Qian; Guan, Zhaoyong; Li, Minggang

2018-06-01

Using NCEP/NCAR reanalysis, we have investigated the features of migrations of atmospheric mass (AM) between land and ocean in Eurasia-North Pacific domain in boreal winter after having both signals of Inter-hemispheric Oscillation and Arctic Oscillation removed from the physical quantities. It is found that there is a Eurasia-North Pacific Oscillation (ENPO) in surface air pressure anomalies. This ENPO pattern characterizes with two oppositely signed anomalous surface pressure centers over Eurasia and North Pacific respectively, indicating strong connections between Siberian high and Aleutian low during period 1979-2012. The maintenance of this ENPO teleconnection is significantly associated with three factors including the anomalous AM flows and zonal circulation cell over Eurasia-North Pacific domain, the Rossby wave energy propagations, and the thermal forcing contrasts near the surface between Eurasia and North Pacific during boreal winter. The variations of both wintertime rainfall and temperature over Eurasia may be strongly affected by ENPO. When the ENPO index is positive (negative), there occurs the AM accumulation (depletion) over Eurasia with simultaneous depletion (accumulation) over mid-latitude North-Pacific. Correspondingly, this anomalous surface pressure pattern along with the related circulation anomalies at different isobaric levels possibly results in winter precipitation decreases (increases) over Siberian Plain and East China, whereas increases (decreases) over southeastern Europe, Xinjiang of China, and the west coast of Sea of Okhotsk. On the other hand, surface air temperature decreases (increases) over large areas of Eurasia. These results are helpful for our better understanding the mechanisms behind circulation and winter climate variations over Eurasia-North Pacific region.

The evolution of water property in the Mackenzie Bay polynya during Antarctic winter

NASA Astrophysics Data System (ADS)

Xu, Zhixin; Gao, Guoping; Xu, Jianping; Shi, Maochong

2017-10-01

Temperature and salinity profile data, collected by southern elephant seals equipped with autonomous CTD-Satellite Relay Data Loggers (CTD-SRDLs) during the Antarctic wintertime in 2011 and 2012, were used to study the evolution of water property and the resultant formation of the high density water in the Mackenzie Bay polynya (MBP) in front of the Amery Ice Shelf (AIS). In late March the upper 100-200 m layer is characterized by strong halocline and inversion thermocline. The mixed layer keeps deepening up to 250 m by mid-April with potential temperature remaining nearly the surface freezing point and sea surface salinity increasing from 34.00 to 34.21. From then on until mid-May, the whole water column stays isothermally at about -1.90℃ while the surface salinity increases by a further 0.23. Hereafter the temperature increases while salinity decreases along with the increasing depth both by 0.1 order of magnitude vertically. The upper ocean heat content ranging from 120.5 to 2.9 MJ m-2, heat flux with the values of 9.8-287.0 W m-2 loss and the sea ice growth rates of 4.3-11.7 cm d-1 were estimated by using simple 1-D heat and salt budget methods. The MBP exists throughout the whole Antarctic winter (March to October) due to the air-sea-ice interaction, with an average size of about 5.0×103 km2. It can be speculated that the decrease of the salinity of the upper ocean may occur after October each year. The recurring sea-ice production and the associated brine rejection process increase the salinity of the water column in the MBP progressively, resulting in, eventually, the formation of a large body of high density water.

Refining surface net radiation estimates in arid and semi-arid climates of Iran

NASA Astrophysics Data System (ADS)

Golkar, Foroogh; Rossow, William B.; Sabziparvar, Ali Akbar

2018-06-01

Although the downwelling fluxes exhibit space-time scales of dependency on characteristic of atmospheric variations, especially clouds, the upward fluxes and, hence the net radiation, depends on the variation of surface properties, particularly surface skin temperature and albedo. Evapotranspiration at the land surface depends on the properties of that surface and is determined primarily by the net surface radiation, mostly absorbed solar radiation. Thus, relatively high spatial resolution net radiation data are needed for evapotranspiration studies. Moreover, in more arid environments, the diurnal variations of surface (air and skin) temperature can be large so relatively high (sub-daily) time resolution net radiation is also needed. There are a variety of radiation and surface property products available but they differ in accuracy, space-time resolution and information content. This situation motivated the current study to evaluate multiple sources of information to obtain the best net radiation estimate with the highest space-time resolution from ISCCP FD dataset. This study investigates the accuracy of the ISCCP FD and AIRS surface air and skin temperatures, as well as the ISCCP FD and MODIS surface albedos and aerosol optical depths as the leading source of uncertainty in ISCCP FD dataset. The surface air temperatures, 10-cm soil temperatures and surface solar insolation from a number of surface sites are used to judge the best combinations of data products, especially on clear days. The corresponding surface skin temperatures in ISCCP FD, although they are known to be biased somewhat high, disagreed more with AIRS measurements because of the mismatch of spatial resolutions. The effect of spatial resolution on the comparisons was confirmed using the even higher resolution MODIS surface skin temperature values. The agreement of ISCCP FD surface solar insolation with surface measurements is good (within 2.4-9.1%), but the use of MODIS aerosol optical depths as an alternative was checked and found to not improve the agreement. The MODIS surface albedos differed from the ISCCP FD values by no more than 0.02-0.07, but because these differences are mostly at longer wavelengths, they did not change the net solar radiation very much. Therefore to obtain the best estimate of surface net radiation with the best combination of spatial and temporal resolution, we developed a method to adjust the ISCCP FD surface longwave fluxes using the AIRS surface air and skin temperatures to obtain the higher spatial resolution of the latter (45 km), while retaining the 3-h time intervals of the former. Overall, the refinements reduced the ISCCP FD longwave flux magnitudes by about 25.5-42.1 W/m2 RMS (maximum difference -27.5 W/m2 for incoming longwave radiation and -59 W/m2 for outgoing longwave radiation) with the largest differences occurring at 9:00 and 12:00 UTC near local noon. Combining the ISCCP FD net shortwave radiation data and the AIRS-modified net longwave radiation data changed the total net radiation for summertime by 4.64 to 61.5 W/m2 and for wintertime by 1.06 to 41.88 W/m2 (about 11.1-39.2% of the daily mean).

Role of persistent low-level clouds in mitigating air quality impacts of wintertime cold pool conditions

NASA Astrophysics Data System (ADS)

VanReken, Timothy M.; Dhammapala, Ranil S.; Jobson, B. Thomas; Bottenus, Courtney L.; VanderSchelden, Graham S.; Kaspari, Susan D.; Gao, Zhongming; Zhu, Qiurui; Lamb, Brian K.; Liu, Heping; Johnston, Jeff

2017-04-01

The Yakima Air Wintertime Nitrate Study (YAWNS) was conducted in January 2013 to investigate the drivers of elevated levels of fine particulate matter (PM2.5) frequently present in the region during winter stagnation periods. An extended stagnation period occurred during the study. For the first four days of the event, skies were clear and the strong diel variation in air pollution patterns were consistent with the expected effects of strong low-level nighttime temperature inversions with moderate mixing during daylight hours. Later in the event a low-level cloud layer formed that persisted over the Yakima Valley for the next seven days while regional conditions remained stagnant. Coincident with the onset of cloud, the levels of all measured primary pollutants, including CO2, CO, NOx, particle number concentration, and black carbon, dropped dramatically and remained low with negligible diel variation for as long as the cloud layer was present. The observed patterns for these air pollutants are consistent with decreased stability and enhanced mixing associated with the cloud-topped boundary layer. Interestingly, levels of secondary pollutants, most notably particulate ammonium nitrate, did not exhibit the same decline. This difference may be due to shifts in the chemical production of secondary pollutants during cloudy conditions, or may merely reflect a further influence of mixing. The results imply that the best strategies for managing wintertime air quality during episodes of persistent cloud are likely different from those needed during clear-sky stagnation events.

On the linkage between Arctic sea ice and Mid-latitude weather pattern: the situation in East Asia

NASA Astrophysics Data System (ADS)

Gu, S.; Zhang, Y.; Wu, Q.

2017-12-01

The influence of Arctic changes on the weather patterns in the highly populated mid-latitude is a complex and controversial topic with considerable uncertainties such as the low signal-to-noise, ill-suited metrics of circulation changes and the missing of dynamical understanding. In this study, the possible linkage between the Arctic sea ice concentration (SIC) and the wintertime weather patterns in East Asia is investigated by comparing groups of statistical and diagnostic analyses. Our study shows a robust relationship between the early autumn SIC in Barents, Kara, Laptev and East Siberia Sea and the energies of wintertime transient activities corresponding to the weather patterns over East Asia on inter-annual time scales. With the reduction of SIC in autumn, the wintertime synoptic (2-10 day) kinetic energy in the north of Eurasia decreases while the low-frequency (10-30 days) kinetic energy, which corresponds to persistent weather patterns, exhibits an evident and dominant increase over the north of Caspian Sea, Lake Baikal and the Ural Mountain. With the reduction of SIC, the intra-seasonal temperature fluctuations present coherent changes over a broader region as well, with significant increase of the low-frequency variability in the vast north of Tibet Plateau and East Asia. The changes of the low-frequency transient activities may be attributed to the slowly southward propagating wave energies from polar regions. However, no consistent stratosphere signals are found associated with such linkage on inter-annual time scales.

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.

The Response of a Branch of Puget Sound, Washington to the 2014 North Pacific Warm Anomaly

NASA Astrophysics Data System (ADS)

Mickett, J.; Newton, J.; Devol, A.; Krembs, C.; Ruef, W.

2016-02-01

The flow of the unprecedentedly-warm upper-ocean North Pacific "Blob" water into Puget Sound, Washington, caused local extreme water property anomalies that extended from the arrival of the water inshore in the fall of 2014 through 2015. Here we report on moored and seaplane observations from Hood Canal, a branch of Puget Sound, where temperature was more than 2σ above climatology for much of the year with maximum temperature anomalies at depth and at the surface +2.5 °C and +7 °C respectively. The low density of the oceanic warm "Blob" water resulted in weak deep water flushing in Hood Canal in the fall of 2014, which combined with a lack of wintertime flushing to result in anomalously-low dissolved oxygen (DO) concentrations at depth. Late-summer 2015 DO values were the lowest in a decade of mooring observations and more than 2σ below climatology. The anomalously low density of the deep basin water allowed a very early onset of the annually-occurring, late-summer intrusion, which first entered Hood Canal at the end of July compared to the usual arrival in early to mid-September. In late August this intrusion conspired with an early fall storm to lift the very low DO deep water to surface at the south end of Hood Canal, causing a significant fish kill event.

Sea Surface Temperature Records Using Sr/Ca Ratios in a Siderastrea siderea Coral from SE Cuba

NASA Astrophysics Data System (ADS)

Fargher, H. A.; Hughen, K. A.; Ossolinski, J. E.; Bretos, F.; Siciliano, D.; Gonzalez, P.

2015-12-01

Sea surface temperature (SST) variability from Cuba remains relatively unknown compared to the rest of the Caribbean. Cuba sits near an inflection point in the spatial pattern of SST from the North Atlantic Oscillation (NAO), and long SST records from the region could reveal changes in the influence of this climate system through time. A Siderastrea siderea coral from the Jardínes de la Reina in southern Cuba was drilled to obtain a 220 year long archive of environmental change. The genus Siderastrea has not been extensively studied as an SST archive, yet Sr/Ca ratios in the Cuban core show a clear seasonal signal and strong correlation to instrumental SST data (r2 = 0.86 and 0.36 for monthly and interannual (winter season) timescales, respectively). Annual growth rates (linear extension) of the coral are observed to have a minor influence on Sr/Ca variability, but do not show a direct correlation to SST on timescales from annual to multidecadal. Sr/Ca measurements from the Cuban coral are used to reconstruct monthly and seasonal (winter, summer) SST extending back more than two centuries. Wintertime SST in southern Cuba is compared to other coral Sr/Ca records of winter-season SST from locations sensitive to the NAO in order to investigate the stationarity of the NAO SST 'fingerprint' through time.

The regional climate model REMO (v2015) coupled with the 1-D freshwater lake model FLake (v1): Fenno-Scandinavian climate and lakes

NASA Astrophysics Data System (ADS)

Pietikäinen, Joni-Pekka; Markkanen, Tiina; Sieck, Kevin; Jacob, Daniela; Korhonen, Johanna; Räisänen, Petri; Gao, Yao; Ahola, Jaakko; Korhonen, Hannele; Laaksonen, Ari; Kaurola, Jussi

2018-04-01

The regional climate model REMO was coupled with the FLake lake model to include an interactive treatment of lakes. Using this new version, the Fenno-Scandinavian climate and lake characteristics were studied in a set of 35-year hindcast simulations. Additionally, sensitivity tests related to the parameterization of snow albedo were conducted. Our results show that overall the new model version improves the representation of the Fenno-Scandinavian climate in terms of 2 m temperature and precipitation, but the downside is that an existing wintertime cold bias in the model is enhanced. The lake surface water temperature, ice depth and ice season length were analyzed in detail for 10 Finnish, 4 Swedish and 2 Russian lakes and 1 Estonian lake. The results show that the model can reproduce these characteristics with reasonably high accuracy. The cold bias during winter causes overestimation of ice layer thickness, for example, at several of the studied lakes, but overall the values from the model are realistic and represent the lake physics well in a long-term simulation. We also analyzed the snow depth on ice from 10 Finnish lakes and vertical temperature profiles from 5 Finnish lakes and the model results are realistic.

Wintertime dynamics in the coastal northeastern Adriatic Sea: the NAdEx 2015 experiment

NASA Astrophysics Data System (ADS)

Vilibić, Ivica; Mihanović, Hrvoje; Janeković, Ivica; Denamiel, Cléa; Poulain, Pierre-Marie; Orlić, Mirko; Dunić, Natalija; Dadić, Vlado; Pasarić, Mira; Muslim, Stipe; Gerin, Riccardo; Matić, Frano; Šepić, Jadranka; Mauri, Elena; Kokkini, Zoi; Tudor, Martina; Kovač, Žarko; Džoić, Tomislav

2018-03-01

The paper investigates the wintertime dynamics of the coastal northeastern Adriatic Sea and is based on numerical modelling and in situ data collected through field campaigns executed during the winter and spring of 2015. The data were collected with a variety of instruments and platforms (acoustic Doppler current profilers, conductivity-temperature-depth probes, glider, profiling float) and are accompanied by the atmosphere-ocean ALADIN/ROMS modelling system. The research focused on the dense-water formation (DWF), thermal changes, circulation, and water exchange between the coastal and open Adriatic. According to both observations and modelling results, dense waters are formed in the northeastern coastal Adriatic during cold bora outbreaks. However, the dense water formed in this coastal region has lower densities than the dense water formed in the open Adriatic due to lower salinities. Since the coastal area is deeper than the open Adriatic, the observations indicate (i) balanced inward-outward exchange at the deep connecting channels of denser waters coming from the open Adriatic DWF site and less-dense waters coming from the coastal region and (ii) outward flow of less-dense waters dominating in the intermediate and surface layers. The latter phenomenon was confirmed by the model, even if it significantly underestimates the currents and transports in the connecting channels. The median residence time of the coastal area is estimated to be approximately 20 days, indicating that the coastal area may be renewed relatively quickly by the open Adriatic waters. The data that were obtained represent a comprehensive marine dataset that can be used to calibrate atmospheric and oceanic numerical models and point to several interesting phenomena to be investigated in the future.

Future Changes in Major Stratospheric Warmings in CCMI Models

NASA Technical Reports Server (NTRS)

Ayarzaguena, B.; Langematz, U.; Polvani, L. M; Abalichin, J.; Akiyoshi, H.; Klekociuk, A.; Michou, M.; Morgenstern, O.; Oman, L.

2015-01-01

Major stratospheric warmings (MSWs) are one of the most important phenomena of wintertime Arctic stratospheric variability. They consist of a warming of the Arctic stratosphere and a deceleration of the polar night jet, triggered by an anomalously high injection of tropospheric wave activity into the stratosphere. Due to the relevance and the impact of MSWs on the tropospheric circulation, several model studies have investigated their potential responses to climate change. However, a wide range of results has been obtained, extending from a future increase in the frequency of MSWs to a decrease. These discrepancies might be explained by different factors such as a competition of radiative and dynamical contributors with opposite effects on the Arctic polar vortex, biases of models to reproduce the related processes, or the metric chosen for the identification of MSWs. In this study, future changes in wintertime Arctic stratospheric variability are examined in order to obtaina more precise picture of future changes in the occurrence of MSWs. In particular, transient REFC2 simulations of different CCMs involved in the Chemistry Climate Model Initiative (CCMI) are used. These simulations extend from 1960 to 2100 and include forcings by halogens and greenhouse gases following the specifications of the CCMI-REF-C2 scenario. Sea surface temperatures (SSTs) and sea-ice distributions are either prescribed from coupled climate model integrations or calculated internally in the case of fully coupled atmosphere-ocean CCMs. Potential changes in the frequency and main characteristics of MSWs in the future are investigated with special focus on the dependence of the results on the criterion for the identification of MSWs and the tropospheric forcing of these phenomena.

Data Assimilation to Improve CMAQ Model Estimates of Particulate Matter Pollution during Wintertime Persistent Cold Air Pool Events in Salt Lake City, Utah

NASA Astrophysics Data System (ADS)

Ivey, C. E.; Balachandran, S.; Russell, A. G.; Hu, Y.; Holmes, H.

2017-12-01

More than one million people live in Salt Lake Valley, Utah, where wintertime pollution reaches unhealthy levels due to the unique meteorology and orography of the region. Persistent cold air pool (PCAP) events occur when high pressure ridges create stagnant conditions over a valley, which hampers large-scale advection and reduces surface wind speeds. During PCAP periods the fraction of incoming solar radiation that reaches the valley floor is also reduced, leading to temperature inversions that allow pollution to build. Pollution levels continue to climb until a washout event removes the pollutants from the valley. Washout events include high winds or precipitation events with advection or wet deposition related removal processes, respectively. In this work, novel data assimilation and source apportionment techniques are applied for January and February 2007 to analyze CMAQ-modeled source composition and source impacts for the Salt Lake Valley during PCAP events. First, a hybrid source-oriented apportionment model is applied over continental U.S. to determine observation and model-based impacts from 20 sources, including agricultural activities, fossil fuel combustion, dust, and metals processing. Then, a secondary bias correction method is applied to better quantify the source impacts on secondary PM2.5, which constitutes the majority of the PM2.5 mass. Revised concentrations reflect what was previously reported in studies of PCAP pollution in the Salt Lake Valley, where the dominant aerosol was found to be ammonium nitrate. Further, gasoline and natural gas combustion were found to be the greatest contributing sources to aerosol concentrations during the PCAP events. The benefit of the data assimilation methods is the availability of spatially and temporally resolved model estimates of source impacts that better reflect observed concentrations.

Surface Salinity Variability in the North Atlantic During Recent Decades

NASA Technical Reports Server (NTRS)

Haekkinen, Sirpa

2001-01-01

The sea surface salinity (SSS) variability in the North Atlantic is investigated using numerical model simulations for the last 50 years based on atmospheric forcing variability from Comprehensive Atmosphere Ocean Data Set (COADS) and National Center for Environmental Prediction / National Center for Atmospheric Research (NCEP/NCAR) Reanalysis. The largest interannual and longer term variability occurs in two regions: the Labrador Sea and the North Equatorial Countercurrent (NECC) region. In both regions the seasonality of the surface salinity variability is prominent with the maximum standard deviation occurring in the summer/fall period. In the Labrador Sea the summer SSS anomalies far exceed those of wintertime in amplitude. The interannual SSS variability in the subpolar gyre can be attributed to two factors: excess ice melt and heat flux (i.e. deep mixing) variations. On the other hand, heat flux variability can also lead to meridional overturning changes on decadal time scales such that weak overturning is manifested in fresh surface conditions in the subpolar gyre. The overturning changes also influence the NECC region SSS variability. Moreover, the subpolar freshening events are expected to occur during the negative phase of North Atlantic Oscillation which is associated with a weak wintertime surface heat loss in the subpolar gyre. No excess sea ice melt or precipitation is necessary for the formation of the fresh anomalies, because with the lack of wide-spread deep mixing, the fresh water that would be expected based on climatology, would accumulate at the surface. Thus, the fresh water 'conveyor' in the Atlantic operates via the overturning circulation such that deep mixing inserts fresh water while removing heat from the water column.

The Impact of Sea Ice Concentration Accuracies on Climate Model Simulations with the GISS GCM

NASA Technical Reports Server (NTRS)

Parkinson, Claire L.; Rind, David; Healy, Richard J.; Martinson, Douglas G.; Zukor, Dorothy J. (Technical Monitor)

2000-01-01

The Goddard Institute for Space Studies global climate model (GISS GCM) is used to examine the sensitivity of the simulated climate to sea ice concentration specifications in the type of simulation done in the Atmospheric Modeling Intercomparison Project (AMIP), with specified oceanic boundary conditions. Results show that sea ice concentration uncertainties of +/- 7% can affect simulated regional temperatures by more than 6 C, and biases in sea ice concentrations of +7% and -7% alter simulated annually averaged global surface air temperatures by -0.10 C and +0.17 C, respectively, over those in the control simulation. The resulting 0.27 C difference in simulated annual global surface air temperatures is reduced by a third, to 0.18 C, when considering instead biases of +4% and -4%. More broadly, least-squares fits through the temperature results of 17 simulations with ice concentration input changes ranging from increases of 50% versus the control simulation to decreases of 50% yield a yearly average global impact of 0.0107 C warming for every 1% ice concentration decrease, i.e., 1.07 C warming for the full +50% to -50% range. Regionally and on a monthly average basis, the differences can be far greater, especially in the polar regions, where wintertime contrasts between the +50% and -50% cases can exceed 30 C. However, few statistically significant effects are found outside the polar latitudes, and temperature effects over the non-polar oceans tend to be under 1 C, due in part to the specification of an unvarying annual cycle of sea surface temperatures. The +/- 7% and 14% results provide bounds on the impact (on GISS GCM simulations making use of satellite data) of satellite-derived ice concentration inaccuracies, +/- 7% being the current estimated average accuracy of satellite retrievals and +/- 4% being the anticipated improved average accuracy for upcoming satellite instruments. Results show that the impact on simulated temperatures of imposed ice concentration changes is least in summer, encouragingly the same season in which the satellite accuracies are thought to be worst. Hence the impact of satellite inaccuracies is probably less than the use of an annually averaged satellite inaccuracy would suggest.

When the Sun's Away, N2O5 Comes Out to Play: An Updated Analysis of Ambient N2O5 Heterogeneous Chemistry

NASA Astrophysics Data System (ADS)

McDuffie, E. E.; Brown, S. S.

2017-12-01

The heterogeneous chemistry of N2O5 impacts the budget of tropospheric oxidants, which directly controls air quality at Earth's surface. The reaction between gas-phase N2O5 and aerosol particles occurs largely at night, and is therefore more important during the less-intensively-studied winter season. Though N2O5-aerosol interactions are vital for the accurate understanding and simulation of tropospheric chemistry and air quality, many uncertainties persist in our understanding of how various environmental factors influence the reaction rate and probability. Quantitative and accurate evaluation of these factors directly improves the predictive capabilities of atmospheric models, used to inform mitigation strategies for wintertime air pollution. In an update to last year's presentation, The Wintertime Fate of N2O5: Observations and Box Model Analysis for the 2015 WINTER Aircraft Campaign, this presentation will focus on recent field results regarding new information about N2O5 heterogeneous chemistry and future research directions.

Evaluation of mix ingredients on the performance of rubber-modified asphalt mixtures

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

Takallou, H.B.

1987-01-01

In rubber-modified asphalt pavements ground recycled tire particles are added to a gap-graded aggregate and then mixed with hot asphalt cement. In view of the significant reductions in wintertime stopping distances under icy or frosty road surface conditions, the use of coarse rubber in asphalt pavements should be seriously considered. This research project consisted of a laboratory study of mix properties as a function of variables such as rubber gradation and content, void content, aggregate graduation, mix process, temperature, and asphalt content. Twenty different mix combinations were evaluated for diametral modulus and fatigue at two different temperatures. Also, five differentmore » mix combinations were evaluated for static creep and permanent deformation. The findings of the laboratory study indicate that the rubber gradation and content, aggregate gradation, and use of surcharge during sample preparation have considerable effect on modulus and fatigue life of the mix. The results of static creep and permanent deformation tests indicate that the rubber asphalt mixes had low stability and high elasticity. Also, due to greater allowable tensile strain in rubber-modified mixtures, the thickness of the modified mixture can be reduced, using a layer equivalency of 1.4 to 1.0« less

Statistical inhomogeneity of dates of sudden stratospheric warmings in the wintertime northern hemisphere

NASA Astrophysics Data System (ADS)

Savenkova, E. N.; Gavrilov, N. M.; Pogoreltsev, A. I.; Manuilova, R. O.

2017-05-01

Using the data of meteorological information reanalysis, a statistical analysis of dates of the main sudden stratospheric warmings observed in 1958-2014 has been performed and their inhomogeneous distribution in winter months with maximums in the beginning of January, from the end of January to the beginning of February, and in the end of February has been shown. To explain these regularities, a climatological analysis of variations in the amplitudes and vertical components of Eliassen-Palm fluxes created by large-scale planetary waves (PWs), as well as of zonal-mean winds and deviations of temperature from their winter-average values in high northern latitudes at heights of up to 50 km from the surface has been carried out using the 20-year (1995-2014) collection of daily meteorological information from the UK Met Office database. During the aforementioned intervals of observing more frequent sudden stratospheric warmings, climatological maximums of temperature perturbations, local minimums of eastward winds, and local maximums of the amplitude and Eliassen-Palm fluxes of PWs with a zonal wavenumber of 1 in the high-latitude northern stratosphere were found. Distinctions between atmospheric characteristics averaged over two last decades have been revealed.

Contrasting responses of the extended Gulf Stream to severe winter forcing

NASA Astrophysics Data System (ADS)

Jacobs, Z.; Grist, J. P.; Marsh, R.; Josey, S. A.; Sinha, B.

2015-12-01

Changes in the path and strength of the extended Gulf Stream, downstream of Cape Hatteras, and the North Atlantic Current (GSNAC), are associated with strong wintertime air-sea interactions that can further influence the atmospheric storm track. The GSNAC response to anomalous air-sea heat fluxes in particular is dependent on the location of excess heat loss, in turn related to meteorological circumstances. Outbreaks of cold continental air may lead to excess cooling over the Sargasso Sea, as in 1976-77. Under these circumstances, the Gulf Stream may intensify through a steepening of cross-stream density gradients. An alternative scenario prevailed during the cold outbreak of 2013-14 where excess cooling occurred over the central subpolar gyre and may have influenced the extreme storminess experienced in western Europe. An objectively-analysed temperature and salinity product (EN4) is used to investigate the variability of the GSNAC. Temperature and salinity profiles are used to obtain geostrophic transport at selected GSNAC transects, confirming strong horizontal temperature gradients and a positive geostrophic velocity anomaly at 70oW in spring 1977, the strongest spring transport seen in the 1970s at this location. In addition to observations, an eddy-resolving model hindcast spanning 1970-2013, is used to further characterise GSNAC transport variability, allowing a fuller assessment of the relationship between the winter surface heat flux, end-of-winter mixed layer depth, subtropical mode water volume and GSNAC transports. Preliminary results reveal a significant negative correlation between the winter surface heat flux over the Sargasso Sea and the GSNAC transport in the following spring.

40 CFR 80.599 - How do I calculate volume balances for designation purposes?

Code of Federal Regulations, 2012 CFR

2012-07-01

...) The following calculation may be used to account for wintertime blending of kerosene and the blending... following calculation may be used to account for wintertime blending of kerosene, the blending of non...

40 CFR 80.599 - How do I calculate volume balances for designation purposes?

Code of Federal Regulations, 2014 CFR

2014-07-01

...) The following calculation may be used to account for wintertime blending of kerosene and the blending... following calculation may be used to account for wintertime blending of kerosene, the blending of non...

40 CFR 80.599 - How do I calculate volume balances for designation purposes?

Code of Federal Regulations, 2013 CFR

2013-07-01

...) The following calculation may be used to account for wintertime blending of kerosene and the blending... following calculation may be used to account for wintertime blending of kerosene, the blending of non...

Snow hydrology in a general circulation model

NASA Technical Reports Server (NTRS)

Marshall, Susan; Roads, John O.; Glatzmaier, Gary

1994-01-01

A snow hydrology has been implemented in an atmospheric general circulation model (GCM). The snow hydrology consists of parameterizations of snowfall and snow cover fraction, a prognostic calculation of snow temperature, and a model of the snow mass and hydrologic budgets. Previously, only snow albedo had been included by a specified snow line. A 3-year GCM simulation with this now more complete surface hydrology is compared to a previous GCM control run with the specified snow line, as well as with observations. In particular, the authors discuss comparisons of the atmospheric and surface hydrologic budgets and the surface energy budget for U.S. and Canadian areas. The new snow hydrology changes the annual cycle of the surface moisture and energy budgets in the model. There is a noticeable shift in the runoff maximum from winter in the control run to spring in the snow hydrology run. A substantial amount of GCM winter precipitation is now stored in the seasonal snowpack. Snow cover also acts as an important insulating layer between the atmosphere and the ground. Wintertime soil temperatures are much higher in the snow hydrology experiment than in the control experiment. Seasonal snow cover is important for dampening large fluctuations in GCM continental skin temperature during the Northern Hemisphere winter. Snow depths and snow extent show good agreement with observations over North America. The geographic distribution of maximum depths is not as well simulated by the model due, in part, to the coarse resolution of the model. The patterns of runoff are qualitatively and quantitatively similar to observed patterns of streamflow averaged over the continental United States. The seasonal cycles of precipitation and evaporation are also reasonably well simulated by the model, although their magnitudes are larger than is observed. This is due, in part, to a cold bias in this model, which results in a dry model atmosphere and enhances the hydrologic cycle everywhere.

A Two Time-scale response of the Southern Ocean to the Ozone Hole: Regional Responses and Mechanisms

NASA Astrophysics Data System (ADS)

Gnanadesikan, A.; Seviour, W.; Waugh, D.; Pradal, M. A. S.

2016-12-01

The impact of changing ozone on the climate of the Southern Ocean is evaluated using an ensemble of coupled climate models. By imposing a step change from 1860 to 2000 conditions we are able to estimate response functions associated with this change. Two time scales are found, an initial cooling centered in the Southwest Pacific followed by cooling in the Pacific sector and then warming in both sectors. The physical processes that drive this response are different across time periods and locations, as is the sign of the response itself. Initial cooling in the Pacific sector is not just driven by the increased winds pushing cold water northward, but also by a decrease in surface salinity reducing wintertime mixing and increased ice and clouds reflecting more shortwave radiation back to space. The decrease in salinity is primarily driven by a southward shift of precipitation associated with a shifting storm track, coupled with decreased evaporation associated with colder surface temperatures. A subsurface increase in heat associated with this reduction in mixing then upwells along the Antarctic coast, producing a subsequent warming. Similar changes in convective activity occur in the Weddell Sea but are offset in time.

Modulation of the Seasonal Cycle of Antarctic Sea Ice Extent Related to the Southern Annular Mode

NASA Astrophysics Data System (ADS)

Doddridge, Edward W.; Marshall, John

2017-10-01

Through analysis of remotely sensed sea surface temperature (SST) and sea ice concentration data, we investigate the impact of winds related to the Southern Annular Mode (SAM) on sea ice extent around Antarctica. We show that positive SAM anomalies in the austral summer are associated with anomalously cold SSTs that persist and lead to anomalous ice growth in the following autumn, while negative SAM anomalies precede warm SSTs and a reduction in sea ice extent during autumn. The largest effect occurs in April, when a unit change in the detrended summertime SAM is followed by a 1.8±0.6 ×105 km2 change in detrended sea ice extent. We find no evidence that sea ice extent anomalies related to the summertime SAM affect the wintertime sea ice extent maximum. Our analysis shows that the wind anomalies related to the negative SAM during the 2016/2017 austral summer contributed to the record minimum Antarctic sea ice extent observed in March 2017.

On the role of successive downstream development in East Asian polar air outbreaks

NASA Technical Reports Server (NTRS)

Jung, C. H.; Hitchman, M. H.

1982-01-01

Common features were drawn from 16 events of wintertime migration of cold Siberian air moving southeastward across the east Asia coast, accompanied by strong northerly winds. Criteria for including an event as an instance of a typical synoptic scale occurrence comprised a surface pressure gradient over Korea exceeding 2.5 mb/100 km, and a drop in the daily mean temperature of over 5 C in one day. The events were required to have at least a 10 day separation. A sequence of events was discerned, including the formation of troughs and ridges over the western north Atlantic 6-7 days before an event, their development and decay downstream from one another across the Eurasian continent, and then an outbreak of polar weather. The troughs and ridges displayed maximum amplitude in the same places in the majority of cases studied, with the center moving along a curved trajectory of the 300 mb flow at nearly 30 deg longitudinally every day.

Episodic Southern Ocean Heat Loss and Its Mixed Layer Impacts Revealed by the Farthest South Multiyear Surface Flux Mooring

NASA Astrophysics Data System (ADS)

Ogle, S. E.; Tamsitt, V.; Josey, S. A.; Gille, S. T.; Cerovečki, I.; Talley, L. D.; Weller, R. A.

2018-05-01

The Ocean Observatories Initiative air-sea flux mooring deployed at 54.08°S, 89.67°W, in the southeast Pacific sector of the Southern Ocean, is the farthest south long-term open ocean flux mooring ever deployed. Mooring observations (February 2015 to August 2017) provide the first in situ quantification of annual net air-sea heat exchange from one of the prime Subantarctic Mode Water formation regions. Episodic turbulent heat loss events (reaching a daily mean net flux of -294 W/m2) generally occur when northeastward winds bring relatively cold, dry air to the mooring location, leading to large air-sea temperature and humidity differences. Wintertime heat loss events promote deep mixed layer formation that lead to Subantarctic Mode Water formation. However, these processes have strong interannual variability; a higher frequency of 2 σ and 3 σ turbulent heat loss events in winter 2015 led to deep mixed layers (>300 m), which were nonexistent in winter 2016.

Large-scale Rossby Normal Modes during Some Recent Northern Hemisphere Winters

DTIC Science & Technology

2011-01-01

day wave has been observed ubiquitously in the troposphere (Madden, 1978) and in the middle atmosphere during winter (Forbes et al., 1995), as well as...assimilate version 2.2 limb retrievals of temperature, water vapor and ozone from the Microwave Limb Sounder (MLS) on NASA’s Aura satellite and...aspects of the wintertime meteorology have been documented: the tropospheric pre-conditioning of a SSW (Coy et al., 2009); the role of gravity wave

Physiological adaptations to prolonged fasting in the overwintering striped skunk (Mephitis mephitis).

PubMed

Mustonen, Anne-Mari; Bowman, Jeff; Sadowski, Carrie; Nituch, Larissa A; Bruce, Laura; Halonen, Toivo; Puukka, Katri; Rouvinen-Watt, Kirsti; Aho, Jari; Nieminen, Petteri

2013-12-01

Wintertime physiology of captive striped skunks (Mephitis mephitis) in response to cold ambient temperature (Ta) and fasting was investigated with body temperature (Tb) and activity recordings and analyses of hematology, plasma biochemistry and tissue fatty acids (FA). After 105 days of food deprivation, the skunks were in phase II of fasting indicated by the elevated plasma nonesterified FA and glycerol but no accumulation of nitrogen end products. Shorter-chain saturated and monounsaturated FA together with C18-20 n-3 polyunsaturated FA were preferentially mobilized. Individual amino acids responded to fasting in a complex manner, while essential and nonessential amino acid sums remained stable. Increases in hemoglobin and hematocrit suggested dehydration. The activity levels were lower in mid-January-early March, and the activity bouts were mostly displayed between 17:00-23:00 h. Daily torpor was observed in two females with 29 and 46 bouts. The deepest torpor (Tb<31 °C) occurred between dawn and early afternoon and lasted for 3.3 ± 0.18 h. The average minimum Tb was 29.2 ± 0.15 °C and the lowest recorded Tb was 25.8 °C. There was significant relation between the average 24-h Tb and Ta. Increases in wintertime Ta, as predicted by climate change scenarios, could influence torpor patterns in the species. © 2013.

Changes in the relationship NAO-Northern hemisphere temperature due to solar activity

NASA Astrophysics Data System (ADS)

Gimeno, Luis; de la Torre, Laura; Nieto, Raquel; García, Ricardo; Hernández, Emiliano; Ribera, Pedro

2003-01-01

The influence of the North Atlantic Oscillation (NAO) on wintertime Northern Hemisphere Temperature (NHT) is investigated. The results suggest that this relationship has different sign according to the phase of the solar cycle. For solar maximum phases NAO and NHT are positively correlated - a result assumed up to the moment - but for solar minimum phases correlations are not significant or even negative. This result is in agreement with the different extension of the NAO for solar cycle phases [Kodera, Geophys. Res. Lett. 29 (2002) 14557-14560] - almost hemispheric for maximum phases and confined to the eastern Atlantic for minimum phases.

Unified Aerosol Microphysics for NWP

DTIC Science & Technology

2013-09-30

it may be treated as a generic variable such as when it is processed by advection, or it may be used specifically like dust in ice nucleation...interactions. We shifted instead to a winter-time passage of a low pressure system across North Africa and the Mediterranean Sea (Figure 1). The strong...MODIS multispectral albedo data, MODIS land surface data, and the NRL DSD for SW Asia and E Asia a multi-variate, non-linear classification was

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.

Wave inhibition by sea ice enables trans-Atlantic ice rafting of debris during Heinrich Events

NASA Astrophysics Data System (ADS)

Wagner, T. J. W.; Dell, R.; Eisenman, I.; Keeling, R. F.; Padman, L.; Severinghaus, J. P.

2017-12-01

The thickness of the ice-rafted debris (IRD) layers that signal Heinrich Events declines far more gradually with distance from the iceberg sources than would be expected based on present-day iceberg trajectories. Here we model icebergs as passive Lagrangian tracers driven by ocean currents, winds, and sea surface temperatures. The icebergs are released in a comprehensive climate model simulation of the last glacial maximum (LGM), as well as a simulation of the modern climate. The two simulated climates result in qualitatively similar distributions of iceberg meltwater and hence debris, with the colder temperatures of the LGM having only a relatively small effect on meltwater spread. In both scenarios, meltwater flux falls off rapidly with zonal distance from the source, in contrast with the more uniform spread of IRD in sediment cores. In order to address this discrepancy, we propose a physical mechanism that could have prolonged the lifetime of icebergs during Heinrich events. The mechanism involves a surface layer of cold and fresh meltwater formed from, and retained around, densely packed armadas of icebergs. This leads to wintertime sea ice formation even in relatively low latitudes. The sea ice in turn shields the icebergs from wave erosion, which is the main source of iceberg ablation. We find that allowing sea ice to form around all icebergs during four months each winter causes the model to approximately agree with the distribution of IRD in sediment cores.

A possible cause of the AO polarity reversal from winter to summer in 2010 and its relation to hemispheric extreme summer weather

NASA Astrophysics Data System (ADS)

Otomi, Yuriko; Tachibana, Yoshihiro; Nakamura, Tetsu

2013-04-01

In 2010, the Northern Hemisphere, in particular Russia and Japan, experienced an abnormally hot summer characterized by record-breaking warm temperatures and associated with a strongly positive Arctic Oscillation (AO), that is, low pressure in the Arctic and high pressure in the midlatitudes. In contrast, the AO index the previous winter and spring (2009/2010) was record-breaking negative. The AO polarity reversal that began in summer 2010 can explain the abnormally hot summer. The winter sea surface temperatures (SST) in the North Atlantic Ocean showed a tripolar anomaly pattern—warm SST anomalies over the tropics and high latitudes and cold SST anomalies over the midlatitudes—under the influence of the negative AO. The warm SST anomalies continued into summer 2010 because of the large oceanic heat capacity. A model simulation strongly suggested that the AO-related summertime North Atlantic oceanic warm temperature anomalies remotely caused blocking highs to form over Europe, which amplified the positive summertime AO. Thus, a possible cause of the AO polarity reversal might be the "memory" of the negative winter AO in the North Atlantic Ocean, suggesting an interseasonal linkage of the AO in which the oceanic memory of a wintertime negative AO induces a positive AO in the following summer. Understanding of this interseasonal linkage may aid in the long-term prediction of such abnormal summer events.

A possible cause of the AO polarity reversal from winter to summer in 2010 and its relation to hemispheric extreme hot summer

NASA Astrophysics Data System (ADS)

Tachibana, Yoshihiro; Otomi, Yuriko; Nakamura, Tetsu

2013-04-01

In 2010, the Northern Hemisphere, in particular Russia and Japan, experienced an abnormally hot summer characterized by record-breaking warm temperatures and associated with a strongly positive Arctic Oscillation (AO), that is, low pressure in the Arctic and high pressure in the midlatitudes. In contrast, the AO index the previous winter and spring (2009/2010) was record-breaking negative. The AO polarity reversal that began in summer 2010 can explain the abnormally hot summer. The winter sea surface temperatures (SST) in the North Atlantic Ocean showed a tripolar anomaly pattern—warm SST anomalies over the tropics and high latitudes and cold SST anomalies over the midlatitudes—under the influence of the negative AO. The warm SST anomalies continued into summer 2010 because of the large oceanic heat capacity. A model simulation strongly suggested that the AO-related summertime North Atlantic oceanic warm temperature anomalies remotely caused blocking highs to form over Europe, which amplified the positive summertime AO. Thus, a possible cause of the AO polarity reversal might be the "memory" of the negative winter AO in the North Atlantic Ocean, suggesting an interseasonal linkage of the AO in which the oceanic memory of a wintertime negative AO induces a positive AO in the following summer. Understanding of this interseasonal linkage may aid in the long-term prediction of such abnormal summer events.

Evaluation of the Community Multiscale Air Quality Model for Simulating Winter Ozone Formation in the Uinta Basin

NASA Astrophysics Data System (ADS)

Matichuk, Rebecca; Tonnesen, Gail; Luecken, Deborah; Gilliam, Rob; Napelenok, Sergey L.; Baker, Kirk R.; Schwede, Donna; Murphy, Ben; Helmig, Detlev; Lyman, Seth N.; Roselle, Shawn

2017-12-01

The Weather Research and Forecasting (WRF) and Community Multiscale Air Quality (CMAQ) models were used to simulate a 10 day high-ozone episode observed during the 2013 Uinta Basin Winter Ozone Study (UBWOS). The baseline model had a large negative bias when compared to ozone (O3) and volatile organic compound (VOC) measurements across the basin. Contrary to other wintertime Uinta Basin studies, predicted nitrogen oxides (NOx) were typically low compared to measurements. Increases to oil and gas VOC emissions resulted in O3 predictions closer to observations, and nighttime O3 improved when reducing the deposition velocity for all chemical species. Vertical structures of these pollutants were similar to observations on multiple days. However, the predicted surface layer VOC mixing ratios were generally found to be underestimated during the day and overestimated at night. While temperature profiles compared well to observations, WRF was found to have a warm temperature bias and too low nighttime mixing heights. Analyses of more realistic snow heat capacity in WRF to account for the warm bias and vertical mixing resulted in improved temperature profiles, although the improved temperature profiles seldom resulted in improved O3 profiles. While additional work is needed to investigate meteorological impacts, results suggest that the uncertainty in the oil and gas emissions contributes more to the underestimation of O3. Further, model adjustments based on a single site may not be suitable across all sites within the basin.

Projecting crop yield in northern high latitude area.

PubMed

Matsumura, Kanichiro

2014-01-01

Changing climatic conditions on seasonal and longer time scales influence agricultural production. Improvement of soil and fertilizer is a strong factor in agricultural production, but agricultural production is influenced by climate conditions even in highly developed countries. It is valuable if fewer predictors make it possible to conduct future projections. Monthly temperature and precipitation, wintertime 500hPa geopotential height, and the previous year's yield are used as predictors to forecast spring wheat yield in advance. Canadian small agricultural divisions (SAD) are used for analysis. Each SAD is composed of a collection of Canadian Agricultural Regions (CAR) of similar weather and growing conditions. Spring wheat yields in each CAR are forecast from the following variables: (a) the previous year's yield, (b) earlier stages of the growing season's climate conditions and, (c) the previous year's wintertime northern hemisphere 500hPa geopotential height field. Arctic outflow events in the Okanagan Valley in Canada are associated with episodes of extremely low temperatures during wintertime. Principal component analysis (PCA) is applied for wintertime northern hemisphere 500hPa geopotential height anomalies. The spatial PCA mode1 is defined as Arctic Oscillation and it influences prevailing westerlies. The prevailing westerlies meanders and influences climatic conditions. The spatial similarity between wintertime top 5 Arctic outflow event year's composites of 500hPa geopotential height anomalies and mode 3's spatial pattern is found. Mode 3's spatial pattern looks like the Pacific/North American (PNA) pattern which describes the variation of atmospheric circulation pattern over the Pacific Ocean and North America. Climate conditions from April to June, May to July, mode 3's time coefficients, and previous year's yield are used for forecasting spring wheat yield in each SAD. Cross-validation procedure which generates eight sets of models for the eight validation periods is used. To show the reproducing projection between observed and calculated values, the root mean squared error for skill score (RMSE SS) with the persistence model serving as the reference model is used. The persistence model is used as a benchmark. The results show that SADs near USA border show better RMSE SS values and mode 3's time coefficients can be a useful predictor especially for inland province such as Manitoba. Among 27 Canadian Prairie's SADs with perfect yield data, 67% of Alberta's SADs, 86% of Manitoba's SADs, and 77% of Saskatchewan's SADs can get positive skill scores. In each SAD, future yield projection is calculated applying predictors in 2013 for the obtained eight sets of models and eight sets of forecasted values in 2013 are averaged and a near future projection result is obtained. Series of outputs including calculated forecasted yield value in each SAD is provided by smart phone application. A system for providing climatic condition for a point with a permission of Climatic Research Unit - University of East Anglia and for obtaining patent is proposed. There are several patented systems similar to the system proposed in this paper. However, these patents are different in essence. The system proposed in this paper consists of two parts. First part is to estimate equations using time series data. The second part is to acquire and apply latest climatic conditions for obtained equations and calculate future projection. If the procedure is refined and devices are originally developed, series of idea can be patented. For future work, crop index, Hokkaido is also introduced.

A Laboratory Model of a Cooled Continental Shelf

DTIC Science & Technology

1993-06-01

26 Abstract A laboratory model of wintertime cooling over a continental shelf has a water surface cooled by air in an annular rotating...singular point where Froude number u/(g’hl)1/2 equaled a given value and flowed out along the bottom. In this formula, u is velocity of the water onto...support cross-shelf geostrophic currents. To accomplish this, an annular geometry was used. A cylindrical tank was fitted with a shallow but wide

Estimates of surface humidity and latent heat fluxes over oceans from SSM/I data

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

Cho, S.H.; Atlas, R.M.; Shie, C.L.

1995-08-01

Monthly averages of daily latent heat fluxes over the oceans for February and August 1988 are estimated using a stability-dependent bulk scheme. Daily fluxes are computed from daily SSM/I (Special Sensor Microwave/Imager) wind speeds and EOF-retrieved SSM/I surface humidity, National Meteorological Center sea surface temperatures, and the European Centre for Medium-Range Weather Forecasts analyzed 2-m temperatures. Daily surface specific humidity (Q) is estimated from SSM/I precipitable water of total (W) and a 500-m bottom layer (W{sub B}) using an EOF (empirical orthogonal function) method. This method has six W-based categories of EOFs (independent of geographical locations) and is developed usingmore » 23 177 FGGE IIb humidity soundings over the global oceans. For 1200 FGGE IIb humidity soundings, the accuracy of EOF-retrieved Q is 0.75 g kg{sup -1} for the case without errors in W and W{sub B} and increases to 1.16 g kg{sup -1} for the case with errors in W and W{sub B}. Compared to 342 collocated radiosonde observations, the EOF-retrieved SSM/I Q has an accuracy of 1.7 g kg{sup -1}. The method improves upon the humidity retrieval of Liu and is competitive with that of Schulz et al. The SSM/I surface humidity and latent heat fluxes of these two months agree reasonably well with those of COADS (Comprehensive Ocean-Atmosphere Data Set). Compared to the COADS, the sea-air humidity difference of SSM/I has a positive bias of approximately 1-3 g kg{sup -1} (an overestimation of flux) over the wintertime eastern equatorial Pacific Ocean, it has a negative bias of about 1-2 g kg{sup -1} (an underestimation of flux). The results further suggest that the two monthly flux estimates, computed from daily and monthly mean data, do not differ significantly over the oceans. 35 refs., 12 figs., 4 tabs.« less

Impacts of meteorological conditions on wintertime PM2.5 pollution in Taiyuan, North China.

PubMed

Miao, Yucong; Liu, Shuhua; Guo, Jianping; Yan, Yan; Huang, Shunxiang; Zhang, Gen; Zhang, Yong; Lou, Mengyun

2018-05-23

Taiyuan frequently experiences heavy PM 2.5 pollution in winter under unfavorable meteorological conditions. To understand how the meteorological factors influence the pollution in Taiyuan, this study involved a systematic analysis for a continuous period from November 2016 to January 2017, using near-surface meteorological observations, radiosonde soundings, PM 2.5 measurements, and three-dimension numerical simulation, in combination with backward trajectory calculations. The results show that PM 2.5 concentration positively correlates with surface temperature and relative humidity and anti-correlates with near-surface wind speed and boundary layer height (BLH). The low BLH is often associated with a strong thermal inversion layer capping over. In addition to the high local emissions, it is found that under certain synoptic conditions, the southwesterly and southerly winds could bring pollutants from Linfen to Taiyuan, leading to a near-surface PM 2.5 concentration higher than 200 μg m -3 . Another pollution enhancing issue is due to the semi-closed basin of Taiyuan affecting the planetary boundary layer (PBL): the surrounding mountains favor the formation of a cold air pool in the basin, which inhibits vertical exchanges of heat, flux, and momentum between PBL and the free troposphere, resulting in stagnant conditions and poor air quality in Taiyuan. These findings can be utilized to improve the understanding of PM 2.5 pollution in Taiyuan, to enhance the accuracy of forecasting pollution, and to provide scientific support for policy makers to mitigate the pollution.

The Anatomy of High Levels of Wintertime Photochemical Ozone Production in the Uintah Basin, Utah, 2013

NASA Astrophysics Data System (ADS)

Schnell, R. C.; Oltmans, S. J.; Johnson, B.; Petron, G.; Neely, R. R.

2013-12-01

The Uintah Basin, Utah is ~ 5,000 km2 in size with lower elevations of ~1400 m msl ringed by mountains rising to ~3,000 m. Within this basin are 6,000 gas wells that produced 10 billion m3 of natural gas and 4,000 oil wells that produced ~22 million barrels of oil in 2012. In winter, the confined geography in the basin traps effluents from these fossil fuel extraction activities into a shallow layer (a few 100 meters deep) beneath strong temperature inversions, especially when ample snow cover is present throughout the basin. The temperature inversions isolate the basin from upper level winds that allow for stagnant conditions that may last for a week or more before a frontal system may flush the basin out. The highly reflective snow provides for enhanced photolysis rates that in February are comparable to those in June. In 2013 December snowfall in the Uintah Basin persisted until early March with exceptionally elevated ozone production occurring in four distinct, 10-day periods separated by 2-3 days of near background values following frontal induced washouts of the basins. In one well studied ozone event, background ozone levels of 55 ppb in the basin were measured from the surface to the lower troposphere on January 30, 2013. By February 1, ozone concentrations from the surface to the top of the 180 m deep temperature inversion averaged 100 ppb. By February 6 ozone concentrations were 165 ppb throughout the same layer. From aircraft measurements these ozone concentrations were observed to be fairly well mixed throughout the basin although there were some notable hotspots. Clean-out of ozone and ozone precursors in the Uintah Basin was observed to occur within 4 hours or less as basin air was replaced with air coming in from the west coast and mixing to the surface.

On the wintertime low bias of Northern Hemisphere carbon monoxide in global model studies

NASA Astrophysics Data System (ADS)

Stein, O.; Schultz, M. G.; Bouarar, I.; Clark, H.; Huijnen, V.; Gaudel, A.; George, M.; Clerbaux, C.

2014-01-01

The uncertainties in the global budget of carbon monoxide (CO) are assessed to explain causes for the long-standing issue of Northern Hemispheric wintertime underestimation of CO concentrations in global models. With a series of MOZART sensitivity simulations for the year 2008, the impacts from changing a variety of surface sources and sinks were analyzed. The model results were evaluated with monthly averages of surface station observations from the global CO monitoring network as well as with total columns observed from satellites and with vertical profiles from measurements on passenger aircraft. Our basic simulation using MACCity anthropogenic emissions underestimated Northern Hemispheric near-surface CO concentrations on average by more than 20 ppb from December to April with the largest bias over Europe of up to 75 ppb in January. An increase in global biomass burning or biogenic emissions of CO or volatile organic compounds (VOC) is not able to reduce the annual course of the model bias and yields too high concentrations over the Southern Hemisphere. Raising global annual anthropogenic emissions results in overestimations of surface concentrations in most regions all-year-round. Instead, our results indicate that anthropogenic emissions in the MACCity inventory are too low for the industrialized countries during winter and spring. Thus we found it necessary to adjust emissions seasonally with regionally varying scaling factors. Moreover, exchanging the original resistance-type dry deposition scheme with a parameterization for CO uptake by oxidation from soil bacteria and microbes reduced the boreal winter dry deposition fluxes and could partly correct for the model bias. When combining the modified dry deposition scheme with increased wintertime road traffic emissions over Europe and North America (factors up to 4.5 and 2, respectively) we were able to optimize the match to surface observations and to reduce the model bias significantly with respect to the satellite and aircraft observations. A reason for the apparent underestimation of emissions may be an exaggerated downward trend in the RCP8.5 scenario in these regions between 2000 and 2010, as this scenario was used to extrapolate the MACCity emissions from their base year 2000. This factor is potentially amplified by a lack of knowledge about the seasonality of emissions. A methane lifetime of 9.7 yr for our basic model and 9.8 yr for the optimized simulation agrees well with current estimates of global OH, but we cannot exclude a potential effect from errors in the geographical and seasonal distribution of OH concentrations. Finally, underestimated emissions from anthropogenic VOCs can also account for a small part of the missing CO concentrations.

Evaluation of the thermal structure in an urban street canyon: field measurements and model simulation

NASA Astrophysics Data System (ADS)

Giovannini, L.; de Franceschi, M.; Zardi, D.

2009-04-01

The results of a research project, aiming at providing tools and criteria to evaluate the temperature field inside an urban street canyon, are presented. Temperature measurements have been carried out, both in summertime and in wintertime, inside a North-South oriented urban canyon in the city of Trento (Italy) in the Alps, with sensors placed at various heights on the front of buildings flanking the street and on top of traffic lights in the middle of the canyon. The results have been analyzed in comparison with data from an automated weather station placed close to the street canyon, at 33 m above ground level and taken as a reference for the above roof-top level. During sunny days a well defined cycle was identified in the daily evolution of air temperature measured by the sensors inside the urban canyon, which was primarily influenced by direct solar radiation. As expected, during the morning the East-facing sensors warmed up faster than the other ones, while in the afternoon the West-facing instruments were the warmest. In most cases the air temperature inside the canyon was higher than above roof level, with differences depending on weather conditions and hour of the day. The dataset allowed to characterize the microclimate of the urban canopy layer and provided a basis for testing the ability of a simple numerical model to simulate the thermal structure inside the urban canyon. The model displays the following characteristics: assignment of distinct surface types (road, walls and roofs), in order to better simulate their physical properties; computation of radiative exchanges inside the canyon based on view factors between the different surfaces and explicitly treating both the solar reflections and the shadows; storage heat flux simulated by means of the heat conduction equation. The model requires as input the geometry parameters of the street and the values of meteorological variables measured above roof level. The main outputs are the heat fluxes determined by the surface energy balance (road, building fronts), the surface temperatures and the average air temperature inside the urban canyon. The comparison between the results of the model and the measurements made during the field experiments displays a good agreement, with an average error of 0.3-0.4 °C on the evaluation of the mean air temperature inside the street canyon. This result is remarkable, especially considering the low level of complexity of the numerical code and the simplifying assumptions made.

Public health vulnerability to wintertime weather: time-series regression and episode analyses of national mortality and morbidity databases to inform the Cold Weather Plan for England.

PubMed

Hajat, S; Chalabi, Z; Wilkinson, P; Erens, B; Jones, L; Mays, N

2016-08-01

To inform development of Public Health England's Cold Weather Plan (CWP) by characterizing pre-existing relationships between wintertime weather and mortality and morbidity outcomes, and identification of groups most at risk. Time-series regression analysis and episode analysis of daily mortality, emergency hospital admissions, and accident and emergency visits for each region of England. Seasonally-adjusted Poisson regression models estimating the percent change in daily health events per 1 °C fall in temperature or during individual episodes of extreme weather. Adverse cold effects were observed in all regions, with the North East, North West and London having the greatest risk of cold-related mortality. Nationally, there was a 3.44% (95% CI: 3.01, 3.87) increase in all-cause deaths and 0.78% (95% CI: 0.53, 1.04) increase in all-cause emergency admissions for every 1 °C drop in temperature below identified thresholds. The very elderly and people with COPD were most at risk from low temperatures. A&E visits for fractures were elevated during heavy snowfall periods, with adults (16-64 years) being the most sensitive age-group. Since even moderately cold days are associated with adverse health effects, by far the greatest health burdens of cold weather fell outside of the alert periods currently used in the CWP. Our findings indicate that levels 0 ('year round planning') and 1 ('winter preparedness and action') are crucial components of the CWP in comparison to the alerts. Those most vulnerable during winter may vary depending on the type of weather conditions being experienced. Recommendations are made for the CWP. Copyright © 2016 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.

Source Contributions to Wintertime Elemental and Organic Carbon in the Western Arctic Based on Radiocarbon and Tracer Apportionment.

PubMed

Barrett, T E; Robinson, E M; Usenko, S; Sheesley, R J

2015-10-06

To quantify the contributions of fossil and biomass sources to the wintertime Arctic aerosol burden source apportionment is reported for elemental (EC) and organic carbon (OC) fractions of six PM10 samples collected during a wintertime (2012-2013) campaign in Barrow, AK. Radiocarbon apportionment of EC indicates that fossil sources contribute an average of 68 ± 9% (0.01-0.07 μg m(-3)) in midwinter decreasing to 49 ± 6% (0.02 μg m(-3)) in late winter. The mean contribution of fossil sources to OC for the campaign was stable at 38 ± 8% (0.04-0.32 μg m(-3)). Samples were also analyzed for organic tracers, including levoglucosan, for use in a chemical mass balance (CMB) source apportionment model. The CMB model was able to apportion 24-53% and 99% of the OC and EC burdens, respectively, during the campaign, with fossil OC contributions ranging from 25 to 74% (0.02-0.09 μg m(-3)) and fossil EC contributions ranging from 73 to 94% (0.03-0.07 μg m(-3)). Back trajectories identified two major wintertime source regions to Barrow: the Russian and North American Arctic. Atmospheric lifetimes of levoglucosan, ranging from 50 to 320 h, revealed variability in wintertime atmospheric processing of this biomass burning tracer. This study allows for unambiguous apportionment of EC to fossil fuel and biomass combustion sources and intercomparison with CMB modeling.

Source Estimation of Wintertime Soot Particles for an Urban Site Varanasi (25.30 N, 83.00 E) in Central Indo-Gangetic Plain Region

NASA Astrophysics Data System (ADS)

Singh, A. K.; Srivastava, M. K.; Dumka, U. C.; Singh, R. K.; Singh, R. S.; Tiwari, S.; Mehrotra, B. J.; Srivastava, A. K.

2017-12-01

Black carbon particles (BC: also called Soot) are formed by incomplete combustion of hydrocarbon based fuels (fossil fuel: coal, diesel, petrol, etc.) as well as due to burning of biomass and bio-fuels (wood, shrubs, dry leaves, etc.). Soot particles are warming agent to the atmosphere that gained wide attention in recent years due to their direct and indirect impacts on local, regional as well as global climate. The climatic effects due to soot are not well understood as indicated by large uncertainties in their climate forcing estimation, particularly in South and East Asian region, possibly due to unavailability of adequate database and information about the source. Measurement of wintertime BC mass concentrations for urban site in central IGP, `Varanasi' (25.30 N, 83.00 E), using a seven wavelength Aethalometer is reported in this work. Delta-C (=BC370 - BC880), which is an indicator of biomass/bio-fuels or residential coal burning is used to understand the source. Aethalometer based source apportionment model "Aethalometer model" was used to apportion the fossil fuel/traffic and wood/biomass burning mass concentration to the total BC mass. The preliminary results for representative month (January-2015) show that daily-average BC mass ranged from 4.47 to 20.70 μg m-3 (Average: 9.45 ± 4.15 μg m-3). The daily Absorption Ångström Exponent (AAE) and the ratio of BCff/BC and BCff/BCwb varied between 1.09 - 1.32, 0.67 - 0.92 and 2 - 40, respectively, due to the changes in BC emissions rates. The total BC, BC from fossil fuel (BCff) and BC from wood/biomass burning (BCwb) behaved in the remarkable diurnal pattern, behaving opposite to the mixing layer heights (MLHs). During daytime, MLHs are higher due to surface based solar warming and causes more volume of atmosphere for the BC dispersion. This phenomenon causes the surface measurement of lower BC mass during the daytime. The data is, however, still being processed for multi-year wintertime observations and the detailed discussions will be shown during the presentation.

Role of climate anomalies on decadal variation in the occurrence of wintertime haze in the Yangtze River Delta, China.

PubMed

Xu, Jianming; Chang, Luyu; Yan, Fengxia; He, JinHai

2017-12-01

The wintertime haze day (HD) in the Yangtze River Delta (YRD) region of China shows a significant upward trend during the past decades due to the rapid industrialization and urbanization. Besides the enhanced anthropogenic emission, climate change also plays the important role in the long term HD variations. In this study, the significant decadal variation of wintertime HD during the period 1960-2012 in YRD is examined by the empirical orthogonal function (EOF) analysis, featured as less HD occurrence before 1980 and more occurrence after 2000. The numerical simulations by the global transport and chemical model (Model for Ozone and Related chemical Tracers, MOZART) with the same emission inventory suggest 8.4% enhancement of wintertime PM 2.5 (particulate matter with the equivalent diameter of air dynamics less than or equal to 2.5μm) mass concentration in YRD during 2001-2009 compared with that during 1971-1979 attributed to meteorological changes, indicating the significant effect of climate anomaly on the decadal variations of wintertime HD. Through the composite analysis on the atmospheric dynamical and thermal conditions based on the reanalysis data, the faster warming in the lower and middle troposphere over the continent in the recent decade is suggested to be important for the out-of-phase decadal HD variation in YRD. The thermal anomaly not only reverses the zonal thermal difference of land-sea to stimulate the anomalous southerlies over YRD leading to reduced prevailing north wind in winter, but also develops the deep inversion below the mid-troposphere to enhance the atmospheric stability. As a result, more frequent and persistent air stagnations in recent decade are expected for the reduction of atmospheric horizontal dispersion and vertical diffusion capacity leading to more occurrence of wintertime HD in YRD. Copyright © 2017 Elsevier B.V. All rights reserved.

Land-atmosphere-ocean interactions in the southeastern Atlantic: interannual variability

NASA Astrophysics Data System (ADS)

Sun, Xiaoming; Vizy, Edward K.; Cook, Kerry H.

2018-02-01

Land-atmosphere-ocean interactions in the southeastern South Atlantic and their connections to interannual variability are examined using a regional climate model coupled with an intermediate-level ocean model. In austral summer, zonal displacements of the South Atlantic subtropical high (SASH) can induce variations of mixed-layer currents in the Benguela upwelling region through surface wind stress curl anomalies near the Namibian coast, and an eastward shifted SASH is related to the first Pacific-South American mode. When the SASH is meridionally displaced, mixed layer vertically-integrated Ekman transport anomalies are mainly a response to the change of alongshore surface wind stress. The latitudinal shift of the SASH tends to dampen the anomalous alongshore wind by modulating the land-sea thermal contrast, while opposed by oceanic diffusion. Although the position of the SASH is closely linked to the phase of El Niño-Southern Oscillation (ENSO) and the southern annular mode (SAM) in austral summer, an overall relationship between Benguela upwelling strength and ENSO or SAM is absent. During austral winter, variations of the mixed layer Ekman transport in the Benguela upwelling region are connected to the strength of the SASH through its impact on both coastal wind stress curl and alongshore surface wind stress. Compared with austral summer, low-level cloud cover change plays a more important role. Although wintertime sea surface temperature fluctuations in the equatorial Atlantic are strong and may act to influence variability over the northern Benguela area, the surface heat budget analysis suggests that local air-sea interactions dominate.

Persian Gulf Response to a Wintertime Shamal Wind Event

DTIC Science & Technology

2010-01-01

26 "’lÖF^B ^^H H7^V??I K ^rB^S IT .’, . 2 i. SST diff - ^ S ^^> • fl THC IP •« 30 28 26 24 22 20 18...during the August- September period (Thoppil and Hogan, submitted for publication). Because of the narrow, shallow and irregular nature of bathy...metry, these eddies remain stationary or trapped by the bottom topography until they dissipate locally. They have clear signatures in the surface

Receptor model source attributions for Utah’s Salt Lake City airshed and the impacts of wintertime secondary ammonium nitrate and ammonium chloride aerosol.

EPA Science Inventory

Communities along Utah’s Wasatch Front are currently developing strategies to reduce daily average PM2.5 levels to below National Ambient Air Quality Standards during wintertime, persistent, multi-day stable atmospheric conditions or cold-air pools. Speciated PM2.5 data from the ...

Anomalies of Siberian High Intensity and Their Precursors in Climatic Models Output

NASA Astrophysics Data System (ADS)

Martynova, Yuliya; Krupchatnikov, Vladimir

2016-04-01

The Siberian High (SH) is a powerful pressure system that determines the weather regime during the wintertime for the huge part of Asia [Sazonov B.I., 1991]. Particularly, SH regulates an intensity and duration of frosts in Siberia. Moreover, this pressure system has a strong connection with another atmospheric centers of action of the Northern Hemisphere such as Arctic High, Icelandic Low, the Azores High [Morozova S.V., 2013]. SH variation is closely related to atmospheric dynamics processes and air temperature variations between surface and middle troposphere. The maintaining of SH mainly depends on downward through the troposphere airflow which variation is strongly affected by the Arctic oscillation (AO). Positive (negative) AO phase causes the remarkably weakening (strengthening) of the downward airflow that has strong effect on the SH behavior [Gong G. et al., 2002; Krupchatnikov V. N. et al., 2009; Martynova Yu.V. and V.N. Krupchatnikov, 2010]. SH is highly exposed to global climate change that increases standard deviation of SH intensity [Fei L.I. and G. A. O. Yong-Qi, 2015]. The changes of SH characteristics result from not only direct climate change effect (such as global temperature rise) but also feedback effect of another climate system parameters variation. Thus, these parameters can serve as precursors of the extremely SH intensity. It's important to remember that the changes of the just one component of this High-Low interaction system could affect whole system. This study is devoted to determination of the precursors of the anomaly SH behavior and estimation of changes of the determined connection in the climate change conditions. The research was provided on a base of climate system models and reanalysis data. Acknowledgements This work is partially supported by SB RAS project VIII.80.2.1, RFBR grants 14-05-00502, 16-35-00301, 16-05-00558. References Fei L.I. and G. A. O. Yong-Qi The Project Siberian High in CMIP5 Models // Atmospheric and Oceanic Science Letters. 2015. V. 8, No. 4, pp. 179-184. Gong, G., D. Entekhabi, and J. Cohen A large-ensemble model study of the wintertime AO-NAO and the role of interannual snow perturbations // J. Climate. 2002. V. 15, pp. 3488-3499. Krupchatnikov V. N. et al. Hydrology and Vegetation Dynamics of the Climate System of Northern Eurasia and the Arctic Basin // Izvestiya, Atmospheric and Oceanic Physics, 2009, Vol. 45, No. 1, pp. 116-136. Martynova Yu.V. and V.N. Krupchatnikov A Study of the Sensitivity of the Surface Temperature in Eurasia in Winter to Snow Cover Anomalies: The Role of the Stratosphere // Izvestiya, Atmospheric and Oceanic Physics, 2010, Vol. 46, No. 6, pp. 757-769. Morozova S.V. Comprehensive Analysis of the Centres of the Atmosphere Action of the Nortern Hemishere // Izv. Saratov Univ. (N.S.), Ser. Earth Sciences, 2013, vol. 13, iss. 1, P. 38-44 (in Russian). Sazonov B.I. Harsh winters and drought / B.I. Sazonov. - L.: Hydrometeoizdat, 1991. - 240 p. (in Russian).

Remote Sensing of the Urban Heat Island Effect Across Biomes in the Continental USA

NASA Technical Reports Server (NTRS)

Imhoff, Marc L.; Zhang, Ping; Wolfe, Robert E.; Bounoua, Lahouari

2010-01-01

Impervious surface area (ISA) from the Landsat TM-based NLCD 2001 dataset and land surface temperature (LST) from MODIS averaged over three annual cycles (2003-2005) are used in a spatial analysis to assess the urban heat island (UHI) skin temperature amplitude and its relationship to development intensity, size, and ecological setting for 38 of the most populous cities in the continental United States. Development intensity zones based on %ISA are defined for each urban area emanating outward from the urban core to the nonurban rural areas nearby and used to stratify sampling for land surface temperatures and NDVI. Sampling is further constrained by biome and elevation to insure objective intercomparisons between zones and between cities in different biomes permitting the definition of hierarchically ordered zones that are consistent across urban areas in different ecological setting and across scales. We find that ecological context significantly influences the amplitude of summer daytime UHI (urban-rural temperature difference) the largest (8 C average) observed for cities built in biomes dominated by temperate broadleaf and mixed forest. For all cities combined, ISA is the primary driver for increase in temperature explaining 70% of the total variance in LST. On a yearly average, urban areas are substantially warmer than the non-urban fringe by 2.9 C, except for urban areas in biomes with arid and semiarid climates. The average amplitude of the UHI is remarkably asymmetric with a 4.3 C temperature difference in summer and only 1.3 C in winter. In desert environments, the LST's response to ISA presents an uncharacteristic "U-shaped" horizontal gradient decreasing from the urban core to the outskirts of the city and then increasing again in the suburban to the rural zones. UHI's calculated for these cities point to a possible heat sink effect. These observational results show that the urban heat island amplitude both increases with city size and is seasonally asymmetric for a large number of cities across most biomes. The implications are that for urban areas developed within forested ecosystems the summertime UHI can be quite high relative to the wintertime UHI suggesting that the residential energy consumption required for summer cooling is likely to increase with urban growth within those biomes.

Multi-year analysis of distributed glacier mass balance modelling and equilibrium line altitude on King George Island, Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Falk, Ulrike; López, Damián A.; Silva-Busso, Adrián

2018-04-01

The South Shetland Islands are located at the northern tip of the Antarctic Peninsula (AP). This region was subject to strong warming trends in the atmospheric surface layer. Surface air temperature increased about 3 K in 50 years, concurrent with retreating glacier fronts, an increase in melt areas, ice surface lowering and rapid break-up and disintegration of ice shelves. The positive trend in surface air temperature has currently come to a halt. Observed surface air temperature lapse rates show a high variability during winter months (standard deviations up to ±1.0 K (100 m)-1) and a distinct spatial heterogeneity reflecting the impact of synoptic weather patterns. The increased mesocyclonic activity during the wintertime over the past decades in the study area results in intensified advection of warm, moist air with high temperatures and rain and leads to melt conditions on the ice cap, fixating surface air temperatures to the melting point. Its impact on winter accumulation results in the observed negative mass balance estimates. Six years of continuous glaciological measurements on mass balance stake transects as well as 5 years of climatological data time series are presented and a spatially distributed glacier energy balance melt model adapted and run based on these multi-year data sets. The glaciological surface mass balance model is generally in good agreement with observations, except for atmospheric conditions promoting snow drift by high wind speeds, turbulence-driven snow deposition and snow layer erosion by rain. No drift in the difference between simulated mass balance and mass balance measurements can be seen over the course of the 5-year model run period. The winter accumulation does not suffice to compensate for the high variability in summer ablation. The results are analysed to assess changes in meltwater input to the coastal waters, specific glacier mass balance and the equilibrium line altitude (ELA). The Fourcade Glacier catchment drains into Potter cove, has an area of 23.6 km2 and is glacierized to 93.8 %. Annual discharge from Fourcade Glacier into Potter Cove is estimated to q ¯ = 25±6 hm3 yr-1 with the standard deviation of 8 % annotating the high interannual variability. The average ELA calculated from our own glaciological observations on Fourcade Glacier over the time period 2010 to 2015 amounts to 260±20 m. Published studies suggest rather stable conditions of slightly negative glacier mass balance until the mid-1980s with an ELA of approx. 150 m. The calculated accumulation area ratio suggests dramatic changes in the future extent of the inland ice cap for the South Shetland Islands.

Determination of a Critical Sea Ice Thickness Threshold for the Central Arctic Ocean

NASA Astrophysics Data System (ADS)

Ford, V.; Frauenfeld, O. W.; Nowotarski, C. J.

2017-12-01

While sea ice extent is readily measurable from satellite observations and can be used to assess the overall survivability of the Arctic sea ice pack, determining the spatial variability of sea ice thickness remains a challenge. Turbulent and conductive heat fluxes are extremely sensitive to ice thickness but are dominated by the sensible heat flux, with energy exchange expected to increase with thinner ice cover. Fluxes over open water are strongest and have the greatest influence on the atmosphere, while fluxes over thick sea ice are minimal as heat conduction from the ocean through thick ice cannot reach the atmosphere. We know that turbulent energy fluxes are strongest over open ocean, but is there a "critical thickness of ice" where fluxes are considered non-negligible? Through polar-optimized Weather Research and Forecasting model simulations, this study assesses how the wintertime Arctic surface boundary layer, via sensible heat flux exchange and surface air temperature, responds to sea ice thinning. The region immediately north of Franz Josef Land is characterized by a thickness gradient where sea ice transitions from the thickest multi-year ice to the very thin marginal ice seas. This provides an ideal location to simulate how the diminishing Arctic sea ice interacts with a warming atmosphere. Scenarios include both fixed sea surface temperature domains for idealized thickness variability, and fixed ice fields to detect changes in the ocean-ice-atmosphere energy exchange. Results indicate that a critical thickness threshold exists below 1 meter. The threshold is between 0.4-1 meters thinner than the critical thickness for melt season survival - the difference between first year and multi-year ice. Turbulent heat fluxes and surface air temperature increase as sea ice thickness transitions from perennial ice to seasonal ice. While models predict a sea ice free Arctic at the end of the warm season in future decades, sea ice will continue to transform seasonally during Polar winter. However, despite seasonal sea ice change, if and where its thickness remains below this critical threshold, the Arctic Ocean will continue interacting with the overlying atmosphere and contributing to Arctic amplification during the cold season.

Impacts of anthropogenic emissions and cold air pools on urban to montane gradients of snowpack ion concentrations in the Wasatch Mountains, Utah

NASA Astrophysics Data System (ADS)

Hall, Steven J.; Maurer, Gregory; Hoch, Sebastian W.; Taylor, Raili; Bowling, David R.

2014-12-01

Urban montane valleys are often characterized by periodic wintertime temperature inversions (cold air pools) that increase atmospheric particulate matter concentrations, potentially stimulating the deposition of major ions to these snow-covered ecosystems. We assessed spatial and temporal patterns of ion concentrations in snow across urban to montane gradients in Salt Lake City, Utah, USA, and the adjacent Wasatch Mountains during January 2011, a period of several persistent cold air pools. Ion concentrations in fresh snow samples were greatest in urban sites, and were lower by factors of 4-130 in a remote high-elevation montane site. Adjacent undeveloped canyons experienced significant incursions of particulate-rich urban air during stable atmospheric conditions, where snow ion concentrations were lower but not significantly different from urban sites. Surface snow ion concentrations on elevation transects in and adjacent to Salt Lake City varied with temporal and spatial trends in aerosol concentrations, increasing following exposure to particulate-rich air as cold air pools developed, and peaking at intermediate elevations (1500-1600 m above sea level, or 200-300 m above the valley floor). Elevation trends in ion concentrations, especially NH4+ and NO3-, corresponded with patterns of aerosol exposure inferred from laser ceilometer data, suggesting that high particulate matter concentrations stimulated fog or dry ion deposition to snow-covered surfaces at the top of the cold air pools. Fog/dry deposition inputs were similar to wet deposition at mid-elevation montane sites, but appeared negligible at lower and higher-elevation sites. Overall, snow ion concentrations in our urban and adjacent montane sites exceeded many values reported from urban precipitation in North America, and greatly exceeded those reported for remote snowpacks. Sodium, Cl-, NH4+, and NO3- concentrations in fresh snow were high relative to previously measured urban precipitation, with means of 120, 117, 42, and 39 μeq l-1, respectively. After exposure to atmospheric particulate matter during cold pool events, surface snow concentrations peaked at 2500, 3600, 93, and 90 μeq l-1 for these ions. Median nitrogen (N) deposition in fresh urban snow samples measured 0.8 kg N ha-1 during January 2011, with similar fog/dry deposition inputs at mid-elevation montane sites. Wintertime anthropogenic air pollution represents a significant source of ions to snow-covered ecosystems proximate to urban montane areas, with important implications for ecosystem function.

Vertical Profiles as Observational Constraints on Nitrous Oxide (N2O) Emissions in an Agricultural Region

NASA Astrophysics Data System (ADS)

Pusede, S.; Diskin, G. S.

2015-12-01

We use diurnal variability in near-surface N2O vertical profiles to derive N2O emission rates. Our emissions estimates are ~3 times greater than are accounted for by inventories, a discrepancy in line with results from previous studies using different approaches. We quantify the surface N2O concentration's memory of local surface emissions on previous days to be 50-90%. We compare measured profiles both over and away from a dense N2O source region in the San Joaquin Valley, finding that profile shapes, diurnal variability, and changes in integrated near-surface column abundances are distinct according to proximity to source areas. To do this work, we use aircraft observations from the wintertime DISCOVER-AQ project in California's San Joaquin Valley, a region of intense agricultural activity.

Contribution of Soil Moisture Information to Streamflow Prediction in the Snowmelt Season: A Continental-Scale Analysis

NASA Technical Reports Server (NTRS)

Reichle, Rolf; Mahanama, Sarith; Koster, Randal; Lettenmaier, Dennis

2009-01-01

In areas dominated by winter snowcover, the prediction of streamflow during the snowmelt season may benefit from three pieces of information: (i) the accurate prediction of weather variability (precipitation, etc.) leading up to and during the snowmelt season, (ii) estimates of the amount of snow present during the winter season, and (iii) estimates of the amount of soil moisture underlying the snowpack during the winter season. The importance of accurate meteorological predictions and wintertime snow estimates is obvious. The contribution of soil moisture to streamflow prediction is more subtle yet potentially very important. If the soil is dry below the snowpack, a significant fraction of the snowmelt may be lost to streamflow and potential reservoir storage, since it may infiltrate the soil instead for later evaporation. Such evaporative losses are presumably smaller if the soil below the snowpack is wet. In this paper, we use a state-of-the-art land surface model to quantify the contribution of wintertime snow and soil moisture information -- both together and separately -- to skill in forecasting springtime streamflow. We find that soil moisture information indeed contributes significantly to streamflow prediction skill.

NASA Astrophysics Data System (ADS)

Shakhova, N. E.; Semiletov, I. P.

2007-12-01

Importance of huge pool of old carbon stored within off-shore permafrost in Siberian region is determined by gradual mobilization of old carbon during permafrost degradation and its incorporation into modern carbon cycle in form of methane. Acceleration of this process due to both natural and anthropogenic disturbance of coastal environment may not only enhance a positive feedback to a global warming, but also can potentially cause rapid or even abrupt climate change on Earth. Theoretically, during times of marine transgression, the sub-sea permafrost could reduce in thickness and develops nearly isothermal conditions close to the melting point. This might occur early on after the marine transgression (high heat flow), or it might take up to several thousand years (low heat flow). Due to the time lag existing between the maximum heat flow and maximum permafrost transformation, the most drastic changes in thermal regime of permafrost might occur not at a warmest time, (for example, at Holocene optimum), but further. Moreover, the key changes in permafrost properties might not be reaching a phase transition stages, but more likely reaching permeability for gas on a larger scale. As sub-sea permafrost does not necessarily represent a rocklike ice-bonded layer, but is sometimes ice free under negative temperatures as its salinity increases, this allows permeability for upward migration of gases, stored within permafrost and/or beneath it. Our recent study in the East-Siberian Arctic shelf (2003-2006) detected CH4 super-saturation of surface water in some areas up to 10,000 % above background level, implying that strong air-to-sea fluxes must occur at times. It leads to significant increase in atmospheric concentrations of methane above the sea surface - up to 8 ppm (latitude specific monthly mean concentrations is 1.85 ppm). Our first wintertime data (April 2007) shows extremely high CH4 concentrations (up to 5.7 µmol l-1) in the surface water beneath the sea ice. Being commensurable with concentrations, measured during the wintertime in thermokarst lakes of Siberian Lowland, these values represent the highest CH4 concentrations, observed in the Arctic Ocean, and are comparable to those registered over decaying gas hydrate fields in the Sea of Okhotsk. The vertical distribution of dissolved CH4, as well as the size and number of CH4 bubbles, trapped within the sea ice, strongly indicate ebullition as a mechanism of CH4 transfer to the water surface. The areas, which should be considered as favorable for opening potentially perennial pathways for methane escape after over 6,000 year inundation, are following: large rivers taliks; a meandering river system (paleo- valleys), running across the shelf; so-called geological disjunctives (fault zones, tectonically and seismically active areas); sedimentary basins; completely submerged, or transformed into sea lagoons, thaw lake taliks.

Seasonal differences in aerosol water may reconcile AOT and surface mass measurements in the Southeast U.S.

NASA Astrophysics Data System (ADS)

Nguyen, T. K. V.; Ghate, V. P.; Carlton, A. M. G.

2015-12-01

Summertime aerosol optical thickness (AOT) in the Southeast U.S. is high and sharply enhanced (2-3 times) compared to wintertime AOT. This seasonal pattern is unique to the Southeast U.S. and is of particular interest because temperatures there have not warmed over the past 100 years, contrasting with trends in other U.S. regions. Some investigators hypothesize the Southeast temperature trend is due to secondary organic aerosols (SOA) formed from interactions of biogenic volatile organic compounds (BVOCs) and anthropogenic emissions that create a cooling haze. However, aerosol measurements made at the surface do not exhibit strong seasonal differences in mass or organic fraction to support this hypothesis. In this work, we attempt to reconcile the spatial and temporal distribution of AOT over the U.S. with surface mass measurements by examining trends in particle-phase liquid water, an aerosol constituent that effectively scatters radiation and is removed from aerosols in mass measurements at routine surface monitoring sites. We employ the thermodynamic model ISORROPIA (v2.1) to estimate surface and aloft aerosol water mass concentrations at locations of Interagency Monitoring of Protected Visual Environments (IMPROVE) sites using measured speciated ion mass concentrations and NCEP North American Regional Reanalysis (NARR) meteorological data. Results demonstrate strong seasonal differences in aerosol water in the eastern compared to the western part of the U.S., consistent with geographic patterns in AOT. The highest mean regional seasonal difference from 2000 to 2007 is 5.5 μg m-3 and occurs the Southeast, while the lowest is 0.44 μg m-3 and occurs in the dry Mountain West. Our findings suggest 1) similarity between spatial trends in aerosol water in the U.S. and previously published AOT data from the MODIS-TERRA instrument and 2) similar interannual trends in mean aerosol water and previously published interannual AOT trends from MISR, MODIS-TERRA, MODIS-AQUA, and the Walker Branch AERONET site. These aerosol water results provide a plausible explanation for the geographical and seasonal patterns in AOT, and reconcile AOT with surface mass networks.

Wintertime vertical variations in particulate matter (PM) and precursor concentrations in the San Joaquin Valley during the California Regional Coarse PM/Fine PM Air Quality Study.

PubMed

Brown, Steven G; Roberts, Paul T; McCarthy, Michael C; Lurmann, Frederick W; Hyslop, Nicole P

2006-09-01

Air quality monitoring was conducted at a rural site with a tower in the middle of California's San Joaquin Valley (SJV) and at elevated sites in the foothills and mountains surrounding the SJV for the California Regional PM10/ PM2.5 Air Quality Study. Measurements at the surface and n a tower at 90 m were collected in Angiola, CA, from December 2000 through February 2001 and included hourly black carbon (BC), particle counts from optical particle counters, nitric oxide, ozone, temperature, relative humidity, wind speed, and direction. Boundary site measurements were made primarily using 24-hr integrated particulate matter (PM) samples. These measurements were used to understand the vertical variations of PM and PM precursors, the effect of stratification in the winter on concentrations and chemistry aloft and at the surface, and the impact of aloft-versus-surface transport on PM concentrations. Vertical variations of concentrations differed among individual species. The stratification may be important to atmospheric chemistry processes, particularly nighttime nitrate formation aloft, because NO2 appeared to be oxidized by ozone in the stratified aloft layer. Additionally, increases in accumulation-mode particle concentrations in the aloft layer during a fine PM (PM2.5) episode corresponded with increases in aloft nitrate, demonstrating the likelihood of an aloft nighttime nitrate formation mechanism. Evidence of local transport at the surface and regional transport aloft was found; transport processes also varied among the species. The distribution of BC appeared to be regional, and BC was often uniformly mixed vertically. Overall, the combination of time-resolved tower and surface measurements provided important insight into PM stratification, formation, and transport.

Physically Consistent Eddy-resolving State Estimation and Prediction of the Coupled Pan-Arctic Climate System at Daily to Interannual Time Scales Using the Regional Arctic Climate Model (RACM)

DTIC Science & Technology

2014-09-30

large biases aloft manifest themselves as large circulation biases at the surface (Fig. 3). Wintertime sea level pressure ( SLP ) contours align closely...extends Arctic, and the Icelandic low is very weak and shifted eastward from its proper location. Summer SLP biases in RASM_nonudg are smaller than...winter SLP biases, but are still substantial, and are again greatly improved in RASM_nudg. Although the magnitude of SLP biases is somewhat smaller

Analysis of Strong Wintertime Ozone Events in an Area of Extensive Oil and Gas Extraction

NASA Astrophysics Data System (ADS)

Rappenglück, Bernhard; Ackermann, Luis; Alvarez, Sergio; Golovko, Julia; Buhr, Martin; Field, Robert; Soltis, Jeff; Montague, Derek C.; Hauze, Bill; Scott, Adamson; Risch, Dan; Wilkerson, George; Bush, David; Stoeckenius, Till; Keslar, Cara

2015-04-01

During recent years, elevated ozone (O3) values have been observed repeatedly in the Upper Green River Basin (UGRB), Wyoming during wintertime. This paper presents an analysis of high ozone days in late winter 2011 (1-hour average up to 166 ppbv). Intensive Observational Periods (IOPs) were performed which included comprehensive surface and boundary layer measurements. Low windspeeds in combination with low mixing layer heights (~50 m agl) are essential for accumulation of pollutants. Air masses contain substantial amounts of reactive nitrogen (NOx) and non-methane hydrocarbons (NMHC) emitted from fossil fuel exploration activities in the Pinedale Anticline. On IOP days in the morning hours reactive nitrogen (up to 69%), then aromatics and alkanes (each ~10-15%; mostly ethane and propane) are major contributors to the hydroxyl (OH) reactivity. This time frame largely coincides with lowest NMHC/NOx ratios (~50), reflecting a relatively low NMHC mixture, and a change from a NOx-limited regime towards a NMHC limited regime. OH production on IOP days is mainly due to nitrous acid (HONO). On a 24-hr basis and as determined for a measurement height of 1.80 m above the surface HONO photolysis on IOP days can contribute ~83% to OH production on average, followed by alkene ozonolysis (~9%). Photolysis by ozone and HCHO photolysis contributes about 4% each to hydroxyl formation. High HONO levels (maximum hourly median on IOP days: 1,096 pptv) are favored by a combination of shallow boundary layer conditions and enhanced photolysis rates due to the high albedo of the snow surface. HONO is most likely formed through (i) abundant nitric acid (HNO3) produced in atmospheric oxidation of NOx, deposited onto the snow surface and undergoing photo-enhanced heterogeneous conversion to HONO and (ii) combustion related emission of HONO. HONO production is confined to the lowermost 10 m of the boundary layer. HONO, serves as the most important precursor for OH, strongly enhanced due to the high albedo of the snow cover.

Compositional and surface characterization of HULIS by UV-Vis, FTIR, NMR and XPS: Wintertime study in Northern India

NASA Astrophysics Data System (ADS)

Kumar, Varun; Goel, Anubha; Rajput, Prashant

2017-09-01

This study (first attempt) characterizes HULIS (Humic Like Substances) in wintertime aerosols (n = 12 during day and nighttime each) from Indo-Gangetic Plain (IGP, at Kanpur) by using various state-of-the art techniques such as UV-VIS, FTIR, 1H NMR and XPS. Based on UV-Vis analysis the absorption coefficient at 365 nm (babs-365) of HULIS was found to average at 13.6 and 28.8 Mm-1 during day and nighttime, respectively. Relatively high babs-365 of HULIS during the nighttime is attributed to influence of fog-processing. However, the power fit of UV-Vis spectrum provided near similar AAE (absorption Angstrom exponent) value of HULIS centering at 4.9 ± 1.4 and 5.1 ± 1.3 during daytime and nighttime, respectively. FTIR spectra and its double derivative revealed the presence of various functional groups viz. alcohols, ketones aldehydes, carboxylic acids as well as unsaturated and saturated carbon bonds. 1H NMR spectroscopy was applied to quantify relative percentage of various types of hydrogen atoms contained in HULIS, whereas XPS technique provided information on surface composition and oxidation states of various elements present. A significantly high abundance of H‒C‒O group has been observed in HULIS (based on 1H NMR); 41.4± 2.7% and 30.9± 2.4% in day and nighttime, respectively. However, aromatic protons (Ar-H) were higher in nighttime samples (19.3± 1.8%) as compared to that in daytime samples (7.5 ± 1.9). XPS studies revealed presence of various species on the surface of HULIS samples. Carbon existed in 7 different chemical states while total nitrogen and sulfur exhibited 3 and 2 different oxidation states (respectively) on the surface of HULIS. This study reports structural information and absorption properties of HULIS which has implications to their role as cloud condensation nuclei and atmospheric direct radiative forcing.

Magnetic navigation behavior and the oceanic ecology of young loggerhead sea turtles.

PubMed

Putman, Nathan F; Verley, Philippe; Endres, Courtney S; Lohmann, Kenneth J

2015-04-01

During long-distance migrations, animals navigate using a variety of sensory cues, mechanisms and strategies. Although guidance mechanisms are usually studied under controlled laboratory conditions, such methods seldom allow for navigation behavior to be examined in an environmental context. Similarly, although realistic environmental models are often used to investigate the ecological implications of animal movement, explicit consideration of navigation mechanisms in such models is rare. Here, we used an interdisciplinary approach in which we first conducted lab-based experiments to determine how hatchling loggerhead sea turtles (Caretta caretta) respond to magnetic fields that exist at five widely separated locations along their migratory route, and then studied the consequences of the observed behavior by simulating it within an ocean circulation model. Magnetic fields associated with two geographic regions that pose risks to young turtles (due to cold wintertime temperatures or potential displacement from the migratory route) elicited oriented swimming, whereas fields from three locations where surface currents and temperature pose no such risk did not. Additionally, at locations with fields that elicited oriented swimming, simulations indicate that the observed behavior greatly increases the likelihood of turtles advancing along the migratory pathway. Our findings suggest that the magnetic navigation behavior of sea turtles is intimately tied to their oceanic ecology and is shaped by a complex interplay between ocean circulation and geomagnetic dynamics. © 2015. Published by The Company of Biologists Ltd.

Simultaneous measurements of new particle formation at 1 s time resolution at a street site and a rooftop site

NASA Astrophysics Data System (ADS)

Zhu, Yujiao; Yan, Caiqing; Zhang, Renyi; Wang, Zifa; Zheng, Mei; Gao, Huiwang; Gao, Yang; Yao, Xiaohong

2017-08-01

This study is the first to use two identical Fast Mobility Particle Sizers for simultaneous measurement of particle number size distributions (PNSDs) at a street site and a rooftop site within 500 m distance in wintertime and springtime to investigate new particle formation (NPF) in Beijing. The collected datasets at 1 s time resolution allow deduction of the freshly emitted traffic particle signal from the measurements at the street site and thereby enable the evaluation of the effects on NPF in an urban atmosphere through a site-by-site comparison. The number concentrations of 8 to 20 nm newly formed particles and the apparent formation rate (FR) in the springtime were smaller at the street site than at the rooftop site. In contrast, NPF was enhanced in the wintertime at the street site with FR increased by a factor of 3 to 5, characterized by a shorter NPF time and higher new particle yields than at the rooftop site. Our results imply that the street canyon likely exerts distinct effects on NPF under warm or cold ambient temperature conditions because of on-road vehicle emissions, i.e., stronger condensation sinks that may be responsible for the reduced NPF in the springtime but efficient nucleation and partitioning of gaseous species that contribute to the enhanced NPF in the wintertime. The occurrence or absence of apparent growth for new particles with mobility diameters larger than 10 nm was also analyzed. The oxidization of biogenic organics in the presence of strong photochemical reactions is suggested to play an important role in growing new particles with diameters larger than 10 nm, but sulfuric acid is unlikely to be the main species for the apparent growth. However, the number of datasets used in this study is relatively small, and larger datasets are essential to draw a general conclusion.

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

Zhang, Jiachen; Zhang, Kai; Liu, Junfeng

Solar reflective “cool roofs” absorb less sunlight than traditional dark roofs, reducing solar heat gain, and decreasing the amount of heat transferred to the atmosphere. Widespread adoption of cool roofs could therefore reduce temperatures in urban areas, partially mitigating the urban heat island effect, and contributing to reversing the local impacts of global climate change. The impacts of cool roofs on global climate remain debated by past research and are uncertain. Using a sophisticated Earth system model, the impacts of cool roofs on climate are investigated at urban, continental, and global scales. We find that global adoption of cool roofsmore » in urban areas reduces urban heat islands everywhere, with an annual- and global-mean decrease from 1.6 to 1.2 K. Decreases are statistically significant, except for some areas in Africa and Mexico where urban fraction is low, and some high-latitude areas during wintertime. Analysis of the surface and TOA energy budget in urban regions at continental-scale shows cool roofs causing increases in solar radiation leaving the Earth-atmosphere system in most regions around the globe, though the presence of aerosols and clouds are found to partially offset increases in upward radiation. Aerosols dampen cool roof-induced increases in upward solar radiation, ranging from 4% in the United States to 18% in more polluted China. Adoption of cool roofs also causes statistically significant reductions in surface air temperatures in urbanized regions of China (0.11±0.10 K) and the United States (0.14±0.12 K); India and Europe show statistically insignificant changes. The research presented here indicates that adoption of cool roofs around the globe would lead to statistically insignificant reductions in global mean air temperature (0.0021 ±0.026 K). This counters past research suggesting that cool roofs can reduce, or even increase global mean temperatures. Thus, we suggest that while cool roofs are an effective tool for reducing building energy use in hot climates, urban heat islands, and regional air temperatures, their influence on global climate is likely negligible.« less

Revisiting the climate impacts of cool roofs around the globe using an Earth system model

NASA Astrophysics Data System (ADS)

Zhang, Jiachen; Zhang, Kai; Liu, Junfeng; Ban-Weiss, George

2016-08-01

Solar reflective ‘cool roofs’ absorb less sunlight than traditional dark roofs, reducing solar heat gain, and decreasing the amount of heat transferred to the atmosphere. Widespread adoption of cool roofs could therefore reduce temperatures in urban areas, partially mitigating the urban heat island effect, and contributing to reversing the local impacts of global climate change. The impacts of cool roofs on global climate remain debated by past research and are uncertain. Using a sophisticated Earth system model, the impacts of cool roofs on climate are investigated at urban, continental, and global scales. We find that global adoption of cool roofs in urban areas reduces urban heat islands everywhere, with an annual- and global-mean decrease from 1.6 to 1.2 K. Decreases are statistically significant, except for some areas in Africa and Mexico where urban fraction is low, and some high-latitude areas during wintertime. Analysis of the surface and TOA energy budget in urban regions at continental-scale shows cool roofs causing increases in solar radiation leaving the Earth-atmosphere system in most regions around the globe, though the presence of aerosols and clouds are found to partially offset increases in upward radiation. Aerosols dampen cool roof-induced increases in upward solar radiation, ranging from 4% in the United States to 18% in more polluted China. Adoption of cool roofs also causes statistically significant reductions in surface air temperatures in urbanized regions of China (-0.11 ± 0.10 K) and the United States (-0.14 ± 0.12 K); India and Europe show statistically insignificant changes. Though past research has disagreed on whether widespread adoption of cool roofs would cool or warm global climate, these studies have lacked analysis on the statistical significance of global temperature changes. The research presented here indicates that adoption of cool roofs around the globe would lead to statistically insignificant reductions in global mean air temperature (-0.0021 ± 0.026 K). Thus, we suggest that while cool roofs are an effective tool for reducing building energy use in hot climates, urban heat islands, and regional air temperatures, their influence on global climate is likely negligible.

Revisiting the Climate Impacts of Cool Roofs around the Globe Using an Earth System Model

NASA Astrophysics Data System (ADS)

Zhang, J.; Ban-Weiss, G. A.; Zhang, K.; Liu, J.

2016-12-01

Solar reflective "cool roofs" absorb less sunlight than traditional dark roofs, reducing solar heat gain, and decreasing the amount of heat transferred to the atmosphere. Widespread adoption of cool roofs could therefore reduce temperatures in urban areas, partially mitigating the urban heat island effect, and contributing to reversing the local impacts of global climate change. The impacts of cool roofs on global climate remain debated by past research and are uncertain. Using a sophisticated Earth system model, the impacts of cool roofs on climate are investigated at urban, continental, and global scales. We find that global adoption of cool roofs in urban areas reduces urban heat islands everywhere, with an annual- and global-mean decrease from 1.6 to 1.2 K. Decreases are statistically significant, except for some areas in Africa and Mexico where urban fraction is low, and some high-latitude areas during wintertime. Analysis of the surface and TOA energy budget in urban regions at continental-scale shows cool roofs causing increases in solar radiation leaving the Earth-atmosphere system in most regions around the globe, though the presence of aerosols and clouds are found to partially offset increases in upward radiation. Aerosols dampen cool roof-induced increases in upward solar radiation, ranging from 4% in the United States to 18% in more polluted China. Adoption of cool roofs also causes statistically significant reductions in surface air temperatures in urbanized regions of China (-0.11±0.10 K) and the United States (-0.14±0.12 K); India and Europe show statistically insignificant changes. Though past research has disagreed on whether widespread adoption of cool roofs would cool or warm global climate, these studies have lacked analysis on the statistical significance of global temperature changes. The research presented here indicates that adoption of cool roofs around the globe would lead to statistically insignificant reductions in global mean air temperature (-0.0021 ± 0.026 K). Thus, we suggest that while cool roofs are an effective tool for reducing building energy use in hot climates, urban heat islands, and regional air temperatures, their influence on global climate is likely negligible.

Remote sensing to monitor cover crop adoption in southeastern Pennsylvania

USGS Publications Warehouse

Hively, Wells; Sjoerd Duiker,; Greg McCarty,; Prabhakara, Kusuma

2015-01-01

In the Chesapeake Bay Watershed, winter cereal cover crops are often planted in rotation with summer crops to reduce the loss of nutrients and sediment from agricultural systems. Cover crops can also improve soil health, control weeds and pests, supplement forage needs, and support resilient cropping systems. In southeastern Pennsylvania, cover crops can be successfully established following corn (Zea mays L.) silage harvest and are strongly promoted for use in this niche. They are also planted following corn grain, soybean (Glycine max L.), and vegetable harvest. In Pennsylvania, the use of winter cover crops for agricultural conservation has been supported through a combination of outreach, regulation, and incentives. On-farm implementation is thought to be increasing, but the actual extent of cover crops is not well quantified. Satellite imagery can be used to map green winter cover crop vegetation on agricultural fields and, when integrated with additional remote sensing data products, can be used to evaluate wintertime vegetative groundcover following specific summer crops. This study used Landsat and SPOT (System Probatoire d’ Observation de la Terre) satellite imagery, in combination with the USDA National Agricultural Statistics Service Cropland Data Layer, to evaluate the extent and amount of green wintertime vegetation on agricultural fields in four Pennsylvania counties (Berks, Lebanon, Lancaster, and York) from 2010 to 2013. In December of 2010, a windshield survey was conducted to collect baseline data on winter cover crop implementation, with particular focus on identifying corn harvested for silage (expected earlier harvest date and lower levels of crop residue), versus for grain (expected later harvest date and higher levels of crop residue). Satellite spectral indices were successfully used to detect both the amount of green vegetative groundcover and the amount of crop residue on the surveyed fields. Analysis of wintertime satellite imagery showed consistent increases in vegetative groundcover over the four-year study period and determined that trends did not result from annual weather variability, indicating that farmers are increasing adoption of practices such as cover cropping that promote wintertime vegetation. Between 2010 and 2013, the occurrence of wintertime vegetation on agricultural fields increased from 36% to 67% of corn fields in Berks County, from 53% to 75% in Lancaster County, from 42% to 65% in Lebanon County, and from 26% to 52% in York County. Apparently, efforts to promote cover crop use in the Chesapeake Bay Watershed have coincided with a rapid increase in the occurrence of wintertime vegetation following corn harvest in southeastern Pennsylvania. However, despite these increases, between 25% and 48% of corn fields remained without substantial green vegetation over the wintertime, indicating further opportunity for cover crop adoption.

Spring snow albedo feedback in daily data over Russia: Comparing in-situ measurements with reanalysis products.

NASA Astrophysics Data System (ADS)

Wegmann, M.; Zolina, O.; Jacobi, H. W.

2016-12-01

Global warming is enhanced at high northern latitudes where the Arctic surface air temperature has risen at twice the rate of the global average in recent decades - a feature called Arctic amplification. This recent Arctic warming signal likely results from several factors such as the albedo feedback due to a diminishing cryosphere, enhanced poleward atmospheric and oceanic heat transport, and changes in humidity. Surface albedo feedback is stating that the additional amount of shortwave radiation at the top of the atmosphere decreases with decreasing surface albedo whereas surface air temperature increases with decreasing surface albedo. It is considered a positive feedback in that an initial warming perturbation than kicks off a strengthening warming. Looking at the Northern Hemisphere with its large landmasses, snow albedo feedback is especially strong since most of these landmasses experience snow cover during boreal wintertime. Unfortunately, so far there remains a lack of reliable observational data over large parts of the cryosphere. Satellite products cover large parts of the NH, however lack high temporal resolution and have problems with large solar zenith angles as well as over complex terrain (eg. Wang et al. 2014). Our analysis focuses at the Russian territory where we utilize in-situ radiation and snow depth measurements. We found 50 stations which measure both variables on a daily basis for the period 2000-2013. Since Hall (2004) found that 50% of the notal NH snow albedo feedback caused by global warming occurs during NH spring, we focus on the transition period of March to June (MAMJ). Thackeray & Fletcher 2006 compared albedo feedback processes CMIP3 and CMIP5 model families and found while the models represent the feedback process accurately, there are still inherent biases and outdated parameterizations. Therefore we use the daily observations and state of the art reanalysis products to 1) evaluate reanalysis and model products in respect to radiation properties, 2) investigate snow albedo feedbacks on a daily scale during spring and 3) to suggest climate change signals over Russia in albedo feedback between 2000 - 2013 based on in-situ measurements.

Mid-Century Ensemble Regional Climate Change Scenarios for the Western United States

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

Leung, Lai R.; Qian, Yun; Bian, Xindi

To study the impacts of climate change on water resources in the western U.S., global climate simulations were produced using the National Center for Atmospheric Research/Department of Energy (NCAR/DOE) Parallel Climate Model (PCM). The Penn State/NCAR Mesoscale Model (MM5) was used to downscale the PCM control (1995-2015) and three future (2040-2060) climate simulations to yield ensemble regional climate simulations at 40 km spatial resolution for the western U.S. This paper focuses on analyses of regional simulations in the Columbia River and Sacramento-San Joaquin River Basins. Results based on the regional simulations show that by mid-century, the average regional warming ofmore » 1-2.5oC strongly affects snowpack in the western U.S. Along coastal mountains, reduction in annual snowpack is about 70%. Besides changes in mean temperature, precipitation, and snowpack, cold season extreme daily precipitation is found to increase by 5 to 15 mm/day (15-20%) along the Cascades and the Sierra. The warming results in increased rainfall over snowfall and reduced snow accumulation (or earlier snowmelt) during the cold season. In the Columbia River Basin, these changes are accompanied by more frequent rain-on-snow events. Overall, they induce higher likelihood of wintertime flooding and reduced runoff and soil moisture in the summer. Such changes could have serious impacts on water resources and agriculture in the western U.S. Changes in surface water and energy budgets in the Columbia River and Sacramento-San Joaquin basins are driven mainly by changes in surface temperature, which are statistically significant at the 0.95 confidence level. Changes in precipitation, however, are spatially incoherent and not statistically significant except for the drying trend during summer.« less

Meteorological and environmental aspects of one of the worst national air pollution episodes (January, 2004) in Logan, Cache Valley, Utah, USA

NASA Astrophysics Data System (ADS)

Malek, Esmaiel; Davis, Tess; Martin, Randal S.; Silva, Philip J.

2006-02-01

Logan, Utah, USA, had the nation's worst air pollution on 15 January, 2004. The high concentration of PM 2.5 (particulates smaller than 2.5 μm in diameter) in the air resulted from geographical, meteorological, and environmental aspects of Cache Valley. A strong inversion (increase of temperature with height) and light precipitation and/or wind were the major causes for trapping pollutants in the air. Other meteorological factors enhancing the inversion were: the prolonged high atmospheric surface pressure, a snow-covered surface which plunged temperatures to as low as - 23.6 °C on January 23rd and high reflection of solar radiation (up to about 80%), which caused less solar radiation absorption during the day throughout the most part of January 2004. Among non-meteorological factors are Cache Valley's small-basin geographical structure which traps air, with no big body of water to help the air circulation (as a result of differential heating and cooling rates for land and water), motor vehicle emissions, and existence of excess ammonia gas as a byproduct of livestock manure and urine. Concentration of PM 2.5 was monitored in downtown Logan. On January 15, 2004, the 24-h, filter-based concentration reached about 132.5 μg per cubic meter of air, an astonishingly high value compared to the values of 65 μg m - 3 and over, indicating a health alert for everyone. These tiny particles in the air have an enormous impact on health, aggravating heart and lung disease, triggering asthma and even death. The causes of this inversion and some suggestions to alleviate the wintertime particle concentration in Cache Valley will be addressed in this article.

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).

Characteristic Paths of Extratropical Cyclones that Cause High Wind Events in the Northeast United States

NASA Astrophysics Data System (ADS)

Booth, J. F.; Rieder, H. E.; Lee, D.; Kushnir, Y.

2014-12-01

This study analyzes the association between wintertime high wind events (HWEs) in the northeast United States US and extratropical cyclones. Sustained wind maxima in the Daily Summary Data from the National Climatic Data Center's Integrated Surface Database are analyzed for 1979-2012. For each station, a Generalized Pareto Distribution (GPD) is fit to the upper tail of the daily maximum wind speed data, and probabilistic return levels at intervals of 1, 3 and 5-years are derived from the GPD fit. At each interval, wind events meeting the return level criteria are termed HWEs. The HWEs occurring on the same day are grouped into multi-station events allowing the association with extratropical cyclones, which are tracked in the European Center for Medium-Range Weather Forecast ERA-Interim reanalysis. Using hierarchical clustering analysis, this study finds that the HWEs are most often associated with cyclones travelling from southwest to northeast, usually originating west of the Appalachian Mountains. The results show that a storm approaching from the southwest is four times more likely to cause strong surface winds than a Nor'easter. A series of sensitivity analyses confirms the robustness of this result. Next, the relationship between the strength of the wind events and the corresponding storm minimum sea level pressure is analyzed. No robust relationship between these quantities is found for strong wind events. Nevertheless, subsequent analysis shows that a relationship between deeper storms and stronger winds emerges if the analysis is extended to the entire set of wintertime storms.

Carbonyl Emissions From Oil and Gas Production Facilities

NASA Astrophysics Data System (ADS)

Lyman, S. N.; O'Neil, T.; Tran, T.

2015-12-01

A number of recent studies have targeted emissions of methane and other hydrocarbons from oil and gas exploration and production activity. These measurements are greatly increasing understanding of the atmospheric impacts of oil and gas development. Very few measurements exist, however, of emissions of formaldehyde and other carbonyls from oil and gas equipment. Carbonyls are toxic and serve as important ozone precursors, especially during winter ozone episodes in places like Utah's Uintah Basin. Current air quality models are only able to reproduce observed high wintertime ozone if they incorporate emissions inventories with very high carbonyl emissions. We measured carbonyl emissions from oil and gas equipment and facilities—including glycol dehydrators, liquid storage tanks, raw gas leaks, raw gas-burning engines, and produced water surface impoundments—in Rocky Mountain oil and gas fields. Carbonyl emissions from raw gas were below detection, but emissions of formaldehyde, acetaldehyde, and other carbonyls were detected from liquid storage tanks, glycol dehydrators, and other oil and gas equipment. In some cases, carbonyls may be formed from the degradation of methanol and other chemicals used in oil and gas production, but the collected data provide evidence for other non-combustion formation pathways. Raw gas-burning engines also emitted carbonyls. Emissions from all measured sources were a small fraction of total volatile organic compound emissions. We incorporated our measurements into an emissions inventory, used that inventory in an air quality model (WRF-SMOKE-CAMx), and were unable to reproduce observed high wintertime ozone. This could be because (1) emission sources we have not yet measured, including compressors, gas processing plants, and others, are large; (2) non-carbonyl emissions, especially those that quickly degrade into carbonyls during photochemical processing, are underestimated in the inventory; or (3) the air quality model is unable to accurately simulate inversion conditions or wintertime chemistry, thus leading to low ozone production in spite of an accurate inventory.

Seasonal rhythms of body temperature in the free-ranging raccoon dog (Nyctereutes procyonoides) with special emphasis on winter sleep.

PubMed

Mustonen, Anne-Mari; Asikainen, Juha; Kauhala, Kaarina; Paakkonen, Tommi; Nieminen, Petteri

2007-01-01

The raccoon dog (Nyctereutes procyonoides) is the only canid with passive overwintering in areas with cold winters, but the depth and rhythmicity of wintertime hypothermia in the wild raccoon dog are unknown. To study the seasonal rhythms of body temperature (T(b)), seven free-ranging animals were captured and implanted with intra-abdominal T(b) loggers and radio-tracked during years 2004-2006. The average size of the home ranges was 306+/-26 ha, and the average 24 h T(b) was 38.0+/-<0.01 degrees C during the snow-free period (May-November). The highest and lowest T(b) were usually recorded around midnight (21:00-02:00 h) and between 05:00-11:00 h, respectively, and the range of the 24 h oscillations was 1.2+/-0.01 degrees C. The animals lost approximately 43+/-6% of body mass in winter (December-April), when the average size of the home ranges was 372+/-108 ha. During the 2-9-wk periods of passivity in January-March, the average 24 h T(b) decreased by 1.4-2.1 degrees C compared to the snow-free period. The raccoon dogs were hypothermic for 5 h in the morning (06:00-11:00 h), whereas the highest T(b) values were recorded between 16:00-23:00 h. The range of the 24 h oscillations increased by approximately 0.6 degrees C, and the rhythmicity was more pronounced than in the snow-free period. The ambient temperature and depth of snow cover were important determinants of the seasonal T(b) rhythms. The overwintering strategy of the raccoon dog resembled the patterns of winter sleep in bears and badgers, but the wintertime passivity of the species was more intermittent and the decrease in the T(b) less pronounced.

The Plunger Hypothesis: an overview of a new theory of stratosphere-troposphere dynamic coupling

NASA Astrophysics Data System (ADS)

Clark, S.; Baldwin, M. P.; Stephenson, D.

2015-12-01

I will demonstrate the advantages of a new method of quantifying polar stratosphere-troposphere coupling by considering large-scale movements of mass into and out of the polar stratosphere. This project aims to use these mass movements to explain pressure and temperature anomalies throughout the polar troposphere and lower stratosphere in the aftermath of extreme stratospheric events. We hypothesise that these mass movements are induced by deposition of momentum by breaking waves in the stratosphere, slowing the wintertime polar vortex, and so are associated with sudden stratospheric warmings (SSWs). Such a mass movement in the upper stratosphere acts to compress the polar atmosphere below it in the manner of a plunger. In this way the pressure anomaly in the upper polar stratosphere 'controls' the pressure and temperature anomalies below by adiabatic compression of the polar atmospheric column. Better understanding this method of control will allow us to use stratospheric data to improve medium-range forecasting ability in the troposphere. One of the key innovations featured in this project is considering pressure and temperature fields at fixed geopotential surfaces, allowing for the easy observation of mass movement into and out of a polar cap region (which we have defined as north of 65N) as a function of altitude. Reanalysis data considered in this manner demonstrates a relationship between tropospheric pressure anomalies and stratospheric anomalies in the polar cap, and so a way to predict tropospheric variability given stratospheric information. This work forms part of a three and a half year PhD project.

The role of local sea surface temperature pattern changes in shaping climate change in the North Atlantic sector

NASA Astrophysics Data System (ADS)

Hand, Ralf; Keenlyside, Noel S.; Omrani, Nour-Eddine; Bader, Jürgen; Greatbatch, Richard J.

2018-03-01

Beside its global effects, climate change is manifested in many regionally pronounced features mainly resulting from changes in the oceanic and atmospheric circulation. Here we investigate the influence of the North Atlantic SST on shaping the winter-time response to global warming. Our results are based on a long-term climate projection with the Max Planck Institute Earth System Model (MPI-ESM) to investigate the influence of North Atlantic sea surface temperature pattern changes on shaping the atmospheric climate change signal. In sensitivity experiments with the model's atmospheric component we decompose the response into components controlled by the local SST structure and components controlled by global/remote changes. MPI-ESM simulates a global warming response in SST similar to other climate models: there is a warming minimum—or "warming hole"—in the subpolar North Atlantic, and the sharp SST gradients associated with the Gulf Stream and the North Atlantic Current shift northward by a few a degrees. Over the warming hole, global warming causes a relatively weak increase in rainfall. Beyond this, our experiments show more localized effects, likely resulting from future SST gradient changes in the North Atlantic. This includes a significant precipitation decrease to the south of the Gulf Stream despite increased underlying SSTs. Since this region is characterised by a strong band of precipitation in the current climate, this is contrary to the usual case that wet regions become wetter and dry regions become drier in a warmer climate. A moisture budget analysis identifies a complex interplay of various processes in the region of modified SST gradients: reduced surface winds cause a decrease in evaporation; and thermodynamic, modified atmospheric eddy transports, and coastal processes cause a change in the moisture convergence. The changes in the the North Atlantic storm track are mainly controlled by the non-regional changes in the forcing. The impact of the local SST pattern changes on regions outside the North Atlantic is small in our setup.

Measuring wintertime surface fluxes at the Tiksi observatory in northern Sakha (Yakutia)

NASA Astrophysics Data System (ADS)

Laurila, Thomas; Aurela, Mika; Hatakka, Juha; Tuovinen, Juha-Pekka; Asmi, Eija; Kondratyev, Vladimir; Ivakhov, Victor; Reshetnikov, Alexander; Makshtas, Alexander; Uttal, Taneil

2013-04-01

Tiksi hydrometeorological observatory has been equipped by new instrumentation for meteorology, turbulence, trace gas and aerosols studies as a joint effort by National Oceanic and Atmospheric Administration (NOAA), Roshydromet (Yakutian Hydrometeorological Service, Arctic and Antarctic Research Institute and Voeikov Main Geophysical Observatory units) and the Finnish Meteorological Institute (FMI). The site is close to the coast of the Laptev Sea on deep permafrost soil with low tundra vegetation and patches of arctic semidesert. Near-by terrain is gently sloping to the south. Further away they are hills in the NE- and W-directions. Turbulence (3-d wind components and sonic temperature) was measured at 10 Hz by USA-1Scientific sonic by Metek, Gmbh. Concentrations of CO2 and H2O were measured by LiCor LI7000 analyzer and CH4 concentrations by Los Gatos RMT200 analyzer. Measurement height was 2.5m. Active layer freeze up took place in extended October period. Methane and carbon dioxide emissions were observed up to early December. Emissions to the atmosphere were enhanced by turbulence created by high wind speeds. Midwinter conditions existed from the end of October to the beginning of April based on rather constant negative net radiation between 20-30 Wm-2 that cools the surface and forms highly stable stratification. Weather conditions are characterized by either low or high wind speed modes. Roughly half of the time wind speed was low, below 2 ms-1. Then, katabatic winds were common and air temperature was between -40..-30°C. High wind speeds, up to 24 ms-1, were observed during synoptic disturbances which lasted typically a few days. In this presentation we will show climatology of surface layer characteristics in late autumn and winter. We will show frequency of well-developed turbulence vs. katabatic low wind speed conditions and related atmospheric stability. The effect of wind speed on methane and carbon dioxide emissions during the freezing period will be shown.

Field evaluation of open and closed-path CO2 flux systems over asphalt surface

NASA Astrophysics Data System (ADS)

Bogoev, I.; Santos, E.

2016-12-01

Eddy covariance (EC) is a widely used method for quantifying surface fluxes of heat, water vapor and carbon dioxide between ecosystems and the atmosphere. A typical EC system consists of an ultrasonic anemometer measuring the 3D wind vector and a fast-response infrared gas analyzer for sensing the water vapor and CO2 density in the air. When using an open-path analyzer that detects the constituent's density in situ a correction for concurrent air temperature and humidity fluctuations must be applied, Webb et al. (1980). In environments with small magnitudes of CO2 flux (<5µmol m-2 s-1) and in the presence of high sensible heat flux, like wintertime over boreal forest, open-path flux measurements have been challenging since the magnitude of the density corrections are as large as the uncorrected CO2 flux itself. A new technology merging the sensing paths of the gas analyzer and the sonic anemometer has been recently developed. This new integrated instrument allows a direct measurement of CO2 mixing ratio in the open air and has the potential to improve the quality of the temperature related density corrections by synchronously measuring the sensible heat flux in the optical path of the gas analyzer. We evaluate the performance and the accuracy of this new sensor over a large parking lot with an asphalt surface where the CO2 fluxes are considered low and the interfering sensible heat fluxes are above 200 Wm-2. A co-located closed-path EC system is used as a reference measurement to examine any systematic biases and apparent CO2 uptake observed with open-path sensors under high sensible heat flux regimes. Half-hour mean and variance of CO2 and water vapor concentrations are evaluated. The relative spectral responses, covariances and corrected turbulent fluxes using a common sonic anemometer are analyzed. The influence of sensor separation and frequency response attenuation on the density corrections is discussed.

Morphology, nurse plants, and minimum apical temperatures for young Carnegiea gigantea

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

Nobel, P.S.

1980-06-01

The northern limit of Carnegiea gigantea (Engelm.) Britton and Rose apparently depends on minimum apical temperatures. Diameters, apical spine coverage, and effects of nurse plants on incoming long-wave (infrared (ir)) radiation, all of which affect apical temperatures, were therefore determined for stems of C. gigantea up to 4 m tall at four sites along a north-south transect in Arizona. A simulation model indicated that the increase in diameter accompanying stem growth raised the minimum apical temperature more than 3 C. Thus, plants with the shortest stems would be expected to be the most vulnerable to freezing damage; indeed, freezing damagemore » on stems <0.5 m tall without nurse plants was fairly common at the colder sites. Nurse plants obstructed a greater portion of the sky for C. gigantea at the colder sites; e.g., the effective environmental temperature for ir radiation at such locations was raised more than 10 C for stems under 1 m tall. If the northern limit of C. gigantea reflects wintertime survival of juveniles, nurse plants could extend the range by offering some protection against freezing.« less

Influence of El Nino Southern Oscillation on the Mesospheric Temperature

NASA Technical Reports Server (NTRS)

Li, Tao; Calvo, Natalia; Yue, Jia; Dou, Xiankang; Russell, J. M, III; Mlynczak, M. G.; She, Chiao-Yao; Xue, Xianghui

2013-01-01

Using the middle atmosphere temperature data set observed by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite experiment between 2002 and 2012, and temperatures simulated by the Whole Atmospheric Community Climate Model version 3.5 (WACCM3.5) between 1953 and 2005, we studied the influence of El Niño-Southern Oscillation (ENSO) on middle atmosphere temperature during the Northern Hemisphere (NH) wintertime. For the first time, a significant winter temperature response to ENSO in the middle mesosphere has been observed, with an anomalous warming of approximately 1.0 K/MEI (Multivariate ENSO Index) in the tropics and an anomalous cooling of approximately 2.0 K/MEI in the NH middle latitudes. The observed temperature responses to ENSO in the mesosphere are opposite to those in the stratosphere, in agreement with previous modeling studies. Temperature responses to ENSO observed by SABER show similar patterns to those simulated by the WACCM3.5 model. Analysis of the WACCM3.5 residual mean meridional circulation response to ENSO reveals a significant downwelling in the tropical mesosphere and upwelling in the NH middle and high latitudes during warm ENSO events, which is mostly driven by anomalous eastward gravity wave forcing in the NH mesosphere.

Summer to Winter Diurnal Variabilities of Temperature and Water Vapour in the Lowermost Troposphere as Observed by HAMSTRAD over Dome C, Antarctica

NASA Astrophysics Data System (ADS)

Ricaud, P.; Genthon, C.; Durand, P.; Attié, J.-L.; Carminati, F.; Canut, G.; Vanacker, J.-F.; Moggio, L.; Courcoux, Y.; Pellegrini, A.; Rose, T.

2012-04-01

The HAMSTRAD (H2O Antarctica Microwave Stratospheric and Tropospheric Radiometers) microwave radiometer operating at 60 GHz (oxygen line, thus temperature) and 183 GHz (water vapour line) has been permanently deployed at the Dome C station, Concordia, Antarctica [75°06'S, 123°21'E, 3,233 m above mean sea level] in January 2010 to study long-term trends in tropospheric absolute humidity and temperature. The great sensitivity of the instrument in the lowermost troposphere helped to characterize the diurnal cycle of temperature and H2O from the austral summer (January 2010) to the winter (June 2010) seasons from heights of 10 to 200 m in the planetary boundary layer (PBL). The study has characterized the vertical resolution of the HAMSTRAD measurements: 10-20 m for temperature and 25-50 m for H2O. A strong diurnal cycle in temperature and H2O (although noisier) has been measured in summertime at 10 m, decreasing in amplitude with height, and phase-shifted by about 4 h above 50 m with a strong H2O-temperature correlation (>0.8) throughout the entire PBL. In autumn, whilst the diurnal cycle in temperature and H2O is less intense, a 12-h phase shift is observed above 30 m. In wintertime, a weak diurnal signal measured between 10 to 200 m is attributed to the methodology employed, which consists of monthly averaged data, and that combines air masses from different origins (sampling effect) and not to the imprint of the null solar irradiation. In situ sensors scanning the entire 24-h period, radiosondes launched at 2000 local solar time (LST) and European Centre for Medium-Range Weather Forecasts (ECMWF) analyses at 0200, 0800, 1400 and 2000 LST agree very well with the HAMSTRAD diurnal cycles for temperature and relatively well for absolute humidity. For temperature, HAMSTRAD tends to be consistent with all the other datasets but shows a smoother vertical profile from 10 to 100 m compared to radiosondes and in-situ data, with ECMWF profiles even smoother than HAMSTRAD profiles, and particularly obvious when moving from summer to winter. For H2O, HAMSTRAD measures a much moister atmosphere compared to all the other datasets with a much weaker diurnal cycle at 10 m. Our study has helped characterize the time variation of the PBL at Dome C with a top around 200 m in summertime decreasing to 30 m in wintertime. In summer, from 2000 to 0600 LST a stable layer is observed, followed by a well-mixed layer the remaining time, while only a nocturnal stable layer remains in winter. In autumn, a daytime convective layer shallower than the nocturnal stable layer develops.

Sensitivity of snow process simulations to precipitation-phase transition method in forested and open areas

NASA Astrophysics Data System (ADS)

Lundberg, A.; Gustafsson, D.

2009-04-01

Modeling of forest snow processes is complicated and especially problematic seems to be the separation of precipitation phase in climates where a large part of the precipitation falls at temperatures near zero degrees Celsius. When the precipitation is classified as snow, the tree crowns can carry an order of magnitude more canopy storage as compared to when the precipitation is classified as rain, and snow in the trees also alters the albedo of the forest while rain does not. Many different schemes for the precipitation phase separation are used by various snow models. Some models use just one air temperature threshold (TR/S) below which all precipitation is assumed to be snow and above which all precipitation is classified as rain. A more common approach for forest snow models is to use two temperature thresholds. The snow fraction (SF) is then set to one below the snow threshold (TS) and to zero above the rain threshold (TR) and SF is assumed to decrease linearly between these two thresholds. Also more sophisticated schemes exist, but three seems to be a lack of agreement on how the precipitation phase separations should be performed. The aim with this study is to use a hydrological model including canopy snow processes to illustrate the sensitivity for different formulations of the precipitation phase separation on a) the simulated maximum snow pack storage b) the interception evaporation loss and c) snow melt runoff. In other words, to investigate of the choice of precipitation phase separation has an impact on the simulated wintertime water balance. Simulations are made for sites in different climates and for both open fields and forest sites in different regions of Sweden from north to south. In general, precipitation phase separation methods that classified snowfall at higher temperatures resulted in a larger proportion of the precipitation lost by interception evaporation as a result of the increased interception capacity. However, the maximum snow accumulation was also increased in some cases due to the overall increased snowfall, depending on canopy density and precipitation and temperature regimes. Results show that the choice of precipitation phase separation method can have an significant impact on the simulated wintertime water balance, especially in forested regions.

Convective Systems Over the Japan Sea: Cloud-Resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Yoshizaki, Masanori; Shie, Chung-Lin; Kato, Teryuki

2002-01-01

Wintertime observations of MCSs (Mesoscale Convective Systems) over the Sea of Japan - 2001 (WMO-01) were collected from January 12 to February 1, 2001. One of the major objectives is to better understand and forecast snow systems and accompanying disturbances and the associated key physical processes involved in the formation and development of these disturbances. Multiple observation platforms (e.g., upper-air soundings, Doppler radar, wind profilers, radiometers, etc.) during WMO-01 provided a first attempt at investigating the detailed characteristics of convective storms and air pattern changes associated with winter storms over the Sea of Japan region. WMO-01 also provided estimates of the apparent heat source (Q1) and apparent moisture sink (Q2). The vertical integrals of Q1 and Q2 are equal to the surface precipitation rates. The horizontal and vertical adjective components of Q1 and Q2 can be used as large-scale forcing for the Cloud Resolving Models (CRMs). The Goddard Cumulus Ensemble (GCE) model is a CRM (typically run with a 1-km grid size). The GCE model has sophisticated microphysics and allows explicit interactions between clouds, radiation, and surface processes. It will be used to understand and quantify precipitation processes associated with wintertime convective systems over the Sea of Japan (using data collected during the WMO-01). This is the first cloud-resolving model used to simulate precipitation processes in this particular region. The GCE model-simulated WMO-01 results will also be compared to other GCE model-simulated weather systems that developed during other field campaigns (i.e., South China Sea, west Pacific warm pool region, eastern Atlantic region and central USA).

Can MODIS AOD be employed to derive PM2.5 in Beijing-Tianjin-Hebei over China?

NASA Astrophysics Data System (ADS)

Ma, Xiaoyan; Wang, Jianying; Yu, Fangqun; Jia, Hailing; Hu, Yanan

2016-11-01

The fine particular matter (PM) concentrations in China have increased considerably due to the rapid economic growth and urbanization in the last few decades, especially in the most populated and industrialized regions. Beijing-Tianjin-Hebei is one of the most polluted regions in China, so to monitor the PM2.5 concentrations over this region is quite critical for human health. By making use the new released hourly PM2.5 mass concentration from ground-based observations in Beijing-Tianjin-Hebei over China, and collocated MODIS level 2 AOD data from April 2014 to March 2015, we explored the relation between surface PM2.5 mass concentration and MODIS AOD and possibility to derive the surface PM2.5 from satellite retrieval in the region. Our study show that the relation strongly depend on the seasons due to distinct seasonal characteristics of PM2.5 and AOD, with a relatively better correlation in spring and summertime (correlation coefficient r ranging from 0.52 to 0.79) than autumn and wintertime (r can be low as to 0.23 in site Baoding). Our analysis gave evidence that worse relationship and/or smaller number of sample in wintertime is associated with the significantly high PM2.5 concentration and a lot of missing data occurring in MODIS AOD, implying that current MODIS AOD retrieval scheme does not work very well in highly polluted cases. The derived PM2.5 mass concentration from MODIS AOD in summertime can basically capture the major observed features of the time series and about 20% large bias of the derived values compared to the observation is expected to be reduced if longer time period data is available and used for analysis.

Can MODIS AOD be employed to derive PM2.5 in Beijing-Tianjin-Hebei over China?

NASA Astrophysics Data System (ADS)

Ma, Xiaoyan

2017-04-01

The fine particular matter (PM) concentrations in China have increased considerably due to the rapid economic growth and urbanization in the last few decades, especially in the most populated and industrialized regions. The Beijing-Tianjin-Hebei is one of the most polluted regions in China, so to monitor the PM2.5 concentrations over this region is quite critical for human health. By making use the new released hourly PM2.5 mass concentration from ground-based observations in Beijing-Tianjin-Hebei over China, and the collocated MODIS level 2 AOD data from April 2014 to March 2015, we explored the relation between surface PM2.5 mass concentration and MODIS AOD and possibility to derive the surface PM2.5 from satellite retrieval in the region. Our study show that the relation strongly depend on the seasons due to distinct seasonal characteristics of PM2.5 and AOD, with a relatively better correlation in spring and summertime than autumn and wintertime. Our analysis give an evidence that worse relationship and/or smaller number of sample in wintertime is associated with the significantly high PM2.5 concentration and a lot of missing data occurring in MODIS AOD, implying that current MODIS AOD retrieval scheme does not work very well in highly polluted cases. The derived PM2.5 mass concentration from MODIS AOD in summertime can basically capture the major observed features of the time series and about 20% large bias of the derived values compared to the observation is expected to be reduced once longer time period data is available and used for analysis.

Aerosol loading in the Southeastern United States: reconciling surface and satellite observations

NASA Astrophysics Data System (ADS)

Ford, B.; Heald, C. L.

2013-04-01

We investigate the seasonality in aerosols over the Southeastern United States using observations from several satellite instruments (MODIS, MISR, CALIOP) and surface network sites (IMPROVE, SEARCH, AERONET). We find that the strong summertime enhancement in satellite-observed aerosol optical depth (factor 2-3 enhancement over wintertime AOD) is not present in surface mass concentrations (25-55% summertime enhancement). Goldstein et al. (2009) previously attributed this seasonality in AOD to biogenic organic aerosol; however, surface observations show that organic aerosol only accounts for ~35% of PM2.5 mass and exhibits similar seasonality to total PM2.5. The GEOS-Chem model generally reproduces these surface aerosol measurements, but under represents the AOD seasonality observed by satellites. We show that seasonal differences in water uptake cannot sufficiently explain the magnitude of AOD increase. As CALIOP profiles indicate the presence of additional aerosol in the lower troposphere (below 700 hPa), which cannot be explained by vertical mixing; we conclude that the discrepancy is due to a missing source of aerosols above the surface in summer.

Autotrophic and Heterotrophic Controls over Winter Soil Carbon Cycling in a Subalpine Forest Ecosystem

NASA Astrophysics Data System (ADS)

Monson, R. K.; Scott-Denton, L. E.; Lipson, D. A.; Weintrub, M. N.; Rosenstiel, T. N.; Schmidt, S. K.; Williams, M. W.; Burns, S. P.; Delany, A. E.; Turnipseed, A. A.

2005-12-01

Studies were conducted at the Niwot Ridge Ameriflux site to understand wintertime soil carbon cycling and its control over ecosystem respiration. Wintertime respiration in this ecosystem results in the loss of 60-90% of the carbon assimilated the previous growing season. Thus, an understanding of the controls over winter carbon cycling is required to understand controls over the annual carbon budget. Trees were girdled to prevent the transport of photosynthates to the rhizosphere. In plots with non-girdled trees a large mid-winter pulse of sucrose was observed to enter the soil. In plots with girdled trees, no sucrose pulse was observed. Trees of this ecosystem are not photosynthetically active during the winter, leading us to conclude that the sucrose pulse is due to the death of fine roots that had accumulated sucrose the previous autumn. The sucrose pulse is potentially utilized by a novel winter community of microbes. Using DNA fingerprinting we discovered that the dominant isolates from the winter soils were from Jathinobacter, whereas the summer isolates were from Burkholderia. The winter community was capable of high rates of respiration and exponential growth at low temperatures, whereas the summer community was not. Our winter observations also indicated high activity of N-acetyl-C-glucosaminidase, one of the principal enzymes involved in chitin degradation. The presence of such high chitinase activities implicates decomposing fungal biomass as a principle source of CO2 beneath the snow pack. Using a novel in situ, beneath-snow CO2 measurement system, we observed unprecedented Q10 values for winter respiration, being 98 and 8.44 x 104 for the soil next to tree boles or within the open spaces between trees, respectively. These high Q10 values are likely the result of fractional changes in the availability of liquid water below 0°C and responses of microbial biomass to changes in the liquid water fraction. Using six-years of eddy covariance data, we showed that interannual variation in winter ecosystem respiration is positively correlated to interannual variation in the spring snow depth. Years with a with a deeper spring snow pack exhibited higher soil temperatures, and concomitantly higher soil respiration rates. Given the recently reported decadal-scale trend in decreasing snow pack in the Western U.S., which is coupled to warm climate anomalies, our observations indicate the potential for higher wintertime soil carbon sequestration due to lower winter ecosystem respiration rates in subalpine forests. Our studies of processes beneath the winter snow pack demonstrate that contrary to previous assumptions, winter biogeochemical processing of soil organic matter is an important component of ecosystem carbon budgets. Despite low temperatures and an inactive plant rhizosphere, winter microbial communities and exoenzymes appear to be active, carbon substrates appear to be in relatively high abundance and soil respiration rates appear to be sensitive to seasonal and interannual winter climate variability.

The Potential Impact of CO2 and Air Temperature Increases on Krummholz's Transformation into Arborescent Form in the Southern Siberian Mountains

NASA Technical Reports Server (NTRS)

Kharuk, V. I.; Dvinskaya, M. L.; Im, S. T.; Ranson, K. J.

2011-01-01

Trees in the southern Siberian Mountains forest-tundra ecotone have considerably increased their radial and apical growth increments during the last few decades. This leads to the widespread vertical transformation of mat and prostrate krummholz forms of larch (Larix sibirica Ledeb) and Siberian pine (Pinus sibirica Du Tour). An analysis of the radial growth increments showed that these transformations began in the mid-1980s. Larch showed a greater resistance to the harsh alpine environment and attained a vertical growth form in areas where Siberian pine is still krummholz. Upper larch treeline is about 10 m higher than Siberian pine treeline. Observed apical and radial growth increment increases were correlated with CO2 concentration (r = 0.83-0.87), summer temperatures (r = 0.55-0.64), and "cold period" (i.e. September-May) air temperatures (r = 0.36-0.37). Positive correlation between growth increments and winter precipitation was attributed to snow cover protection for trees during wintertime.

Multi-RCM ensemble downscaling of global seasonal forecasts (MRED)

NASA Astrophysics Data System (ADS)

Arritt, R. W.

2008-12-01

The Multi-RCM Ensemble Downscaling (MRED) project was recently initiated to address the question, Can regional climate models provide additional useful information from global seasonal forecasts? MRED will use a suite of regional climate models to downscale seasonal forecasts produced by the new National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFS) seasonal forecast system and the NASA GEOS5 system. The initial focus will be on wintertime forecasts in order to evaluate topographic forcing, snowmelt, and the potential usefulness of higher resolution, especially for near-surface fields influenced by high resolution orography. Each regional model will cover the conterminous US (CONUS) at approximately 32 km resolution, and will perform an ensemble of 15 runs for each year 1982-2003 for the forecast period 1 December - 30 April. MRED will compare individual regional and global forecasts as well as ensemble mean precipitation and temperature forecasts, which are currently being used to drive macroscale land surface models (LSMs), as well as wind, humidity, radiation, turbulent heat fluxes, which are important for more advanced coupled macro-scale hydrologic models. Metrics of ensemble spread will also be evaluated. Extensive analysis will be performed to link improvements in downscaled forecast skill to regional forcings and physical mechanisms. Our overarching goal is to determine what additional skill can be provided by a community ensemble of high resolution regional models, which we believe will eventually define a strategy for more skillful and useful regional seasonal climate forecasts.

Eastern Pacific tropical cyclones intensified by El Niño delivery of subsurface ocean heat.

PubMed

Jin, F-F; Boucharel, J; Lin, I-I

2014-12-04

The El Niño Southern Oscillation (ENSO) creates strong variations in sea surface temperature in the eastern equatorial Pacific, leading to major climatic and societal impacts. In particular, ENSO influences the yearly variations of tropical cyclone (TC) activities in both the Pacific and Atlantic basins through atmospheric dynamical factors such as vertical wind shear and stability. Until recently, however, the direct ocean thermal control of ENSO on TCs has not been taken into consideration because of an apparent mismatch in both timing and location: ENSO peaks in winter and its surface warming occurs mostly along the Equator, a region without TC activity. Here we show that El Niño--the warm phase of an ENSO cycle--effectively discharges heat into the eastern North Pacific basin two to three seasons after its wintertime peak, leading to intensified TCs. This basin is characterized by abundant TC activity and is the second most active TC region in the world. As a result of the time involved in ocean transport, El Niño's equatorial subsurface 'heat reservoir', built up in boreal winter, appears in the eastern North Pacific several months later during peak TC season (boreal summer and autumn). By means of this delayed ocean transport mechanism, ENSO provides an additional heat supply favourable for the formation of strong hurricanes. This thermal control on intense TC variability has significant implications for seasonal predictions and long-term projections of TC activity over the eastern North Pacific.

Wintertime Emission Ratios of CO2 and NOy from Washington, D.C.-Baltimore

NASA Astrophysics Data System (ADS)

Salmon, O. E.; Shepson, P. B.; Ren, X.; Stirm, B. H.; Brown, S. S.; Fibiger, D. L.; Thornton, J. A.; Dickerson, R. R.; McDuffie, E. E.; Gurney, K. R.

2016-12-01

Cities are known to be key emitters of the combustion products carbon dioxide (CO2) and nitrogen oxides (NOx=NO+NO2), as a result of spatially concentrated combustion sources from the transportation sector and electric energy generating stations. Wintertime in mid-latitude cities provides a unique environment for these species to accumulate and react. Fewer daylight hours of relatively weak radiation, along with lower temperatures, can lead to slower oxidation of NOx, which influences the partitioning of total reactive nitrogen (NOy; the sum of NOx, NO3, N2O5, ClNO2, HNO3, acyl peroxy nitrates, and alkyl nitrates). The altered photochemical lifetimes of these reactive nitrogen species can result in unique chemistry and transport, altering the oxidizing capacity of the atmosphere within the city, and downwind of it as well. A collaborative study, employing three airborne platforms, named the Wintertime INvestigation of Transport, Emissions, and Reactivity (WINTER) was conducted in the northeastern United States in 2015 to investigate these cold season trends. Recent studies have suggested national inventories overestimate NOx emissions. We estimate city-wide emission rates of NOy from the Washington, D.C.-Baltimore area, and report their magnitude as emission factors relative to CO2. The University of Maryland's (UMD) 402B research Cessna and Purdue University's Airborne Laboratory for Atmospheric Research were instrumented to measure CO2, NO2, and other gaseous species. Measurements of NOy, and partitioning of its constituent species, were conducted from the NCAR C-130. NOy mixing ratios were estimated from the UMD and Purdue NO2 measurements using the C-130 measurements of NO2:NOy, a ratio whose magnitude is a function of time since emission from the cities. The Purdue and UMD mass balance flights around Washington, D.C.-Baltimore allow for the determination of the urban area's downwind enhancement in CO2 and estimated NOy. The urban enhancements in these gases are multiplied by the perpendicular wind speed to give the total emission rate. Here we compare our absolute NOy emission rates and the relative NOy:CO2 emission ratios from the UMD and Purdue flights to inventory estimates.

Climatology of winter transition days for the contiguous USA, 1951-2007

NASA Astrophysics Data System (ADS)

Hondula, David M.; Davis, Robert E.

2011-01-01

In middle and high latitudes, climate change could impact the frequency and characteristics of frontal passages. Although transitions between air masses are significant features of the general circulation that influence human activities and other surface processes, they are much more difficult to objectively identify than single variables like temperature or even extreme events like fires, droughts, and floods. The recently developed Spatial Synoptic Classification (SSC) provides a fairly objective means of identifying frontal passages. In this research, we determine the specific meteorological patterns represented by the SSC's Transition category, a "catch-all" group that attempts to identify those days that cannot be characterized as a single, homogeneous air mass type. The result is a detailed transition climatology for the continental USA. We identify four subtypes of the Transition category based on intra-day sea level pressure change and dew point temperature change. Across the contiguous USA, most transition days are identified as cold fronts and warm fronts during the winter season. Among the two less common subtypes, transition days in which the dew point temperature and pressure both rise are more frequently observed across the western states, and days in which both variables fall are more frequently observed in coastal regions. The relative frequencies of wintertime warm and cold fronts have changed over the period 1951-2007. Relative cold front frequency has significantly increased in the Northeast and Midwest regions, and warm front frequencies have declined in the Midwest, Rocky Mountain, and Pacific Northwest regions. The overall shift toward cold fronts and away from warm fronts across the northern USA arises from a combination of an enhanced ridge over western North America and a northward shift of storm tracks throughout the mid-latitudes. These results are consistent with projections of climate change associated with elevated greenhouse gas concentrations.

High-latitude stratospheric aerosols measured by the SAM II satellite system in 1978 and 1979

NASA Technical Reports Server (NTRS)

Mccormick, M. P.; Chu, W. P.; Mcmaster, L. R.; Grams, G. W.; Hamill, P.; Steele, H. M.; Swissler, T. J.; Herman, B. M.; Pepin, T. J.; Russell, P. B.

1981-01-01

Results of the first year of data collection by the SAM (Stratospheric Aerosol Measurement) II satellite system are presented. Almost 10,000 profiles of stratospheric aerosol extinction in the Arctic and Antarctic regions are used to construct plots of weekly averaged aerosol extinction versus altitude and time and stratospheric optical depth versus time. Corresponding temperature fields are presented. These data show striking similarities in the aerosol behavior for corresponding seasons. Wintertime polar stratospheric clouds that are strongly correlated with temperature are documented. They are much more prevalent in the Antarctic stratosphere during the cold austral winter and increase the stratospheric optical depths by as much as an order of magnitude for a period of about 2 months. These clouds might represent a sink for stratospheric water vapor and must be considered in the radiative budget for this region and time.

Resolving the Strange Behavior of Extraterrestrial Potassium in the Upper Atmosphere

NASA Technical Reports Server (NTRS)

Plane, J. M. C.; Feng, W.; Dawkins, E.; Chipperfield, M. P.; Hoeffner, J.; Janches, D.; Marsh, D. R.

2014-01-01

It has been known since the 1960s that the layers of Na and K atoms, which occur between 80 and 105km in the Earth's atmosphere as a result of meteoric ablation, exhibit completely different seasonal behavior. In the extratropics Na varies annually, with a pronounced wintertime maximum and summertime minimum. However, K varies semiannually with a small summertime maximum and minima at the equinoxes. This contrasting behavior has never been satisfactorily explained. Here we use a combination of electronic structure and chemical kinetic rate theory to determine two key differences in the chemistries of K and Na. First, the neutralization of K+ ions is only favored at low temperatures during summer. Second, cycling between K and its major neutral reservoir KHCO3 is essentially temperature independent. A whole atmosphere model incorporating this new chemistry, together with a meteor input function, now correctly predicts the seasonal behavior of the K layer.

Summer-winter concentrations and gas-particle partitioning of short chain chlorinated paraffins in the atmosphere of an urban setting.

PubMed

Wang, Thanh; Han, Shanlong; Yuan, Bo; Zeng, Lixi; Li, Yingming; Wang, Yawei; Jiang, Guibin

2012-12-01

Short chain chlorinated paraffins (SCCPs) are semi-volatile chemicals that are considered persistent in the environment, potential toxic and subject to long-range transport. This study investigates the concentrations and gas-particle partitioning of SCCPs at an urban site in Beijing during summer and wintertime. The total atmospheric SCCP levels ranged 1.9-33.0 ng/m(3) during wintertime. Significantly higher levels were found during the summer (range 112-332 ng/m(3)). The average fraction of total SCCPs in the particle phase (ϕ) was 0.67 during wintertime but decreased significantly during the summer (ϕ = 0.06). The ten and eleven carbon chain homologues with five to eight chlorine atoms were the predominant SCCP formula groups in air. Significant linear correlations were found between the gas-particle partition coefficients and the predicted subcooled vapor pressures and octanol-air partition coefficients. The gas-particle partitioning of SCCPs was further investigated and compared with both the Junge-Pankow adsorption and K(oa)-based absorption models. Copyright © 2012 Elsevier Ltd. All rights reserved.

Frequency of extreme daily temperatures (HadEX2) over Eurasia documented in a northern Red Sea coral oxygen isotope record during the last century

NASA Astrophysics Data System (ADS)

Ionita-Scholz, Monica; Felis, Thomas; Rimbu, Norel; Lohmann, Gerrit

2017-04-01

The potential of a bimonthly-resolved northern Red Sea coral δ18O record as an archive for the occurrence of extreme daily temperature phenomena over Eurasia during Northern Hemisphere winter is investigated for the 1901-1995 period using extreme indices provided by the HadEX2 dataset (e.g., frost days, ice days, cold nights and cold days). The coral δ18O record reflects a combined signal of temperature and salinity variations in the surface waters of the northern Red Sea, and has been previously shown to provide a proxy for atmospheric circulation changes over the Northern Hemisphere mid-latitudes at interannual to decadal time scales. Here we show, by applying composite analysis, that cooler/more arid (warmer/less arid) winter conditions in the northern Red Sea region, indicated by positive (negative) coral δ18O anomalies (January-February), are related to a strong (weak) Northern Hemisphere polar vortex and, as a consequence, to a decreased (increased) number of days characterized by very cold temperatures and frost over Scandinavia and Central Europe. This situation is associated with an increased (decreased) number of days characterized by very cold temperatures and frost over the Balkan region. The occurrence of these daily temperature extremes is modulated by the frequency of atmospheric blocking over the British Isles and Central Europe, and a shift in the direction of the North Atlantic storm tracks. Importantly, coral records provide a bimonthly to monthly resolution, compared to other high-resolution proxy records which have either an annual resolution (e.g., ice cores, varved sediments) or an annual resolution with a signal that is biased towards a specific season that in most cases is not winter (e.g., tree rings). We argue that bimonthly-resolved northern Red Sea coral δ18O records provide an archive of interannual to decadal variations in the occurrence of extreme daily temperature events over wintertime Eurasia prior to the start of instrumental observations.

Aerosol loading in the Southeastern United States: reconciling surface and satellite observations

NASA Astrophysics Data System (ADS)

Ford, B.; Heald, C. L.

2013-09-01

We investigate the seasonality in aerosols over the Southeastern United States using observations from several satellite instruments (MODIS, MISR, CALIOP) and surface network sites (IMPROVE, SEARCH, AERONET). We find that the strong summertime enhancement in satellite-observed aerosol optical depth (AOD) (factor 2-3 enhancement over wintertime AOD) is not present in surface mass concentrations (25-55% summertime enhancement). Goldstein et al. (2009) previously attributed this seasonality in AOD to biogenic organic aerosol; however, surface observations show that organic aerosol only accounts for ∼35% of fine particulate matter (smaller than 2.5 μm in aerodynamic diameter, PM2.5) and exhibits similar seasonality to total surface PM2.5. The GEOS-Chem model generally reproduces these surface aerosol measurements, but underrepresents the AOD seasonality observed by satellites. We show that seasonal differences in water uptake cannot sufficiently explain the magnitude of AOD increase. As CALIOP profiles indicate the presence of additional aerosol in the lower troposphere (below 700 hPa), which cannot be explained by vertical mixing, we conclude that the discrepancy is due to a missing source of aerosols above the surface layer in summer.

Use of output from high-resolution atmospheric models in landscape-scale hydrologic models: An assessment

USGS Publications Warehouse

Hostetler, S.W.; Giorgi, F.

1993-01-01

In this paper we investigate the feasibility of coupling regional climate models (RCMs) with landscape-scale hydrologic models (LSHMs) for studies of the effects of climate on hydrologic systems. The RCM used is the National Center for Atmospheric Research/Pennsylvania State University mesoscale model (MM4). Output from two year-round simulations (1983 and 1988) over the western United States is used to drive a lake model for Pyramid Lake in Nevada and a streamfiow model for Steamboat Creek in Oregon. Comparisons with observed data indicate that MM4 is able to produce meteorologic data sets that can be used to drive hydrologic models. Results from the lake model simulations indicate that the use of MM4 output produces reasonably good predictions of surface temperature and evaporation. Results from the streamflow simulations indicate that the use of MM4 output results in good simulations of the seasonal cycle of streamflow, but deficiencies in simulated wintertime precipitation resulted in underestimates of streamflow and soil moisture. Further work with climate (multiyear) simulations is necessary to achieve a complete analysis, but the results from this study indicate that coupling of LSHMs and RCMs may be a useful approach for evaluating the effects of climate change on hydrologic systems.

Boreal Winter MJO Teleconnection in the Community Atmosphere Model Version 5 with the Unified Convection Parameterization

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

Yoo, Changhyun; Park, Sungsu; Kim, Daehyun

2015-10-01

The Madden-Julian Oscillation (MJO), the dominant mode of tropical intraseasonal variability, influences weather and climate in the extratropics through atmospheric teleconnection. In this study, two simulations using the Community Atmosphere Model version 5 (CAM5) - one with the default shallow and deep convection schemes and the other with the Unified Convection scheme (UNICON) - are employed to examine the impacts of cumulus parameterizations on the simulation of the boreal wintertime MJO teleconnection in the Northern Hemisphere. We demonstrate that the UNICON substantially improves the MJO teleconnection. When the UNICON is employed, the simulated circulation anomalies associated with the MJO bettermore » resemble the observed counterpart, compared to the simulation with the default convection schemes. Quantitatively, the pattern correlation for the 300-hPa geopotential height anomalies between the simulations and observation increases from 0.07 for the default schemes to 0.54 for the UNICON. These circulation anomalies associated with the MJO further help to enhance the surface air temperature and precipitation anomalies over North America, although room for improvement is still evident. Initial value calculations suggest that the realistic MJO teleconnection with the UNICON is not attributed to the changes in the background wind, but primarily to the improved tropical convective heating associated with the MJO.« less

Determinants of vitamin D status in adult Crohn's disease patients, with particular emphasis on supplemental vitamin D use.

PubMed

Gilman, J; Shanahan, F; Cashman, K D

2006-07-01

To investigate determinants (pathophysiologic and physiologic, behavioural and lifestyle) of vitamin D status in Irish Crohn's disease (CD) patients. A cross-sectional observational study. Cork City, Ireland (52 degrees N). Crohn's Disease patients (n=58; mean age 38.1 years) were recruited from Cork University Hospital. Fifty and nineteen percent of Irish CD patients were vitamin D deficient (defined by serum 25 hydroxyvitamin (OH) D levels <50 nmol/l) during winter and summer, respectively. Multiple regression analysis showed that summer-time serum 25 (OH) D levels were positively associated with use of vitamin D supplements (P=0.033) and negatively associated with smoking (P=0.006) and being male (P=0.063). During winter-time, use of vitamin D supplements (P=0.041) and sun habits (P=0.066) were positively associated, whereas small intestinal involvement (P=0.005) and body mass index (BMI) (P=0.083) were negatively associated with serum 25 (OH) D levels. There was no significant association between other non-pathophysiologic (age, dietary calcium or vitamin D) or pathophysiologic factors (steroid use, resection), and serum 25 (OH) D levels, at either season. Approximately 41 and 60% of the total variation in summer- and winter-time serum 25 (OH) D, respectively, was explained by this model. A high proportion of Irish CD patents had some level of vitamin D deficiency (<50 nmol/l) during late-wintertime. Use of regular low-dose supplemental vitamin D, particularly by patients with small intestinal involvement, cessation of smoking and adequate, but responsible, exposure to summer sunlight as well as maintaining BMI in the normal range could help maintain adequate vitamin D levels during wintertime.

Survival, growth and reproduction of non-indigenous Nile tilapia, Oreochromis niloticus (Linnaeus 1758). I. Physiological capabilities in various temperatures and salinities

USGS Publications Warehouse

Schofield, Pamela J.; Peterson, Mark S.; Lowe, Michael R.; Brown-Peterson, Nancy J.; Slack, William T.

2011-01-01

The physiological tolerances of non-native fishes is an integral component of assessing potential invasive risk. Salinity and temperature are environmental variables that limit the spread of many non-native fishes. We hypothesised that combinations of temperature and salinity will interact to affect survival, growth, and reproduction of Nile tilapia, Oreochromis niloticus, introduced into Mississippi, USA. Tilapia withstood acute transfer from fresh water up to a salinity of 20 and survived gradual transfer up to 60 at typical summertime (30°C) temperatures. However, cold temperature (14°C) reduced survival of fish in saline waters ≥10 and increased the incidence of disease in freshwater controls. Although fish were able to equilibrate to saline waters in warm temperatures, reproductive parameters were reduced at salinities ≥30. These integrated responses suggest that Nile tilapia can invade coastal areas beyond their point of introduction. However, successful invasion is subject to two caveats: (1) wintertime survival depends on finding thermal refugia, and (2) reproduction is hampered in regions where salinities are ≥30. These data are vital to predicting the invasion of non-native fishes into coastal watersheds. This is particularly important given the predicted changes in coastal landscapes due to global climate change and sea-level rise.

Decadal variability in the oxygen inventory of North Atlantic subtropical underwater captured by sustained, long-term oceanographic time series observations

NASA Astrophysics Data System (ADS)

Montes, Enrique; Muller-Karger, Frank E.; Cianca, Andrés.; Lomas, Michael W.; Lorenzoni, Laura; Habtes, Sennai

2016-03-01

Historical observations of potential temperature (θ), salinity (S), and dissolved oxygen concentrations (O2) in the tropical and subtropical North Atlantic (0-500 m; 0-40°N, 10-90°W) were examined to understand decadal-scale changes in O2 in subtropical underwater (STUW). STUW is observed at four of the longest, sustained ocean biogeochemical and ecological time series stations, namely, the CArbon Retention In A Colored Ocean (CARIACO) Ocean Time Series Program (10.5°N, 64.7°W), the Bermuda Atlantic Time-series Study (BATS; 31.7°N, 64.2°W), Hydrostation "S" (32.1°N, 64.4°W), and the European Station for Time-series in the Ocean, Canary Islands (ESTOC; 29.2°N, 15.5°W). Observations over similar time periods at CARIACO (1996-2013), BATS (1988-2011), and Hydrostation S (1980-2013) show that STUW O2 has decreased approximately 0.71, 0.28, and 0.37 µmol kg-1 yr-1, respectively. No apparent change in STUW O2 was observed at ESTOC over the course of the time series (1994-2013). Ship observation data for the tropical and subtropical North Atlantic archived at NOAA National Oceanographic Data Center show that between 1980 and 2013, STUW O2 (upper ~300 m) declined 0.58 µmol kg-1 yr-1 in the southeastern Caribbean Sea (10-15°N, 60-70°W) and 0.68 µmol kg-1 yr-1 in the western subtropical North Atlantic (30-35°N, 60-65°W). A declining O2 trend was not observed in the eastern subtropical North Atlantic (25-30°N, 15-20°W) over the same period. Most of the observed O2 loss seems to result from shifts in ventilation associated with decreased wind-driven mixing and a slowing down of STUW formation rates, rather than changes in diffusive air-sea O2 gas exchange or changes in the biological oceanography of the North Atlantic. Variability of STUW O2 showed a significant relationship with the wintertime (January-March) Atlantic Multidecadal Oscillation index (AMO, R2 = 0.32). During negative wintertime AMO years trade winds are typically stronger between 10°N and 30°N. These conditions stimulate the formation and ventilation of STUW. The decreasing trend in STUW O2 in the three decades spanning 1980 through 2013 reflects the shift from a strongly negative wintertime AMO between the mid-1980s and mid-1990s to a positive wintertime AMO observed between the mid-1990s and 2013. These changes in STUW O2 were captured by the CARIACO, BATS, and Hydrostation S time series stations. Sustained positive AMO conditions could lead to further deoxygenation in tropical and subtropical North Atlantic upper waters.

Intercomparison of AIRS and HIRDLS stratospheric gravity wave observations

NASA Astrophysics Data System (ADS)

Meyer, Catrin I.; Ern, Manfred; Hoffmann, Lars; Trinh, Quang Thai; Alexander, M. Joan

2018-01-01

We investigate stratospheric gravity wave observations by the Atmospheric InfraRed Sounder (AIRS) aboard NASA's Aqua satellite and the High Resolution Dynamics Limb Sounder (HIRDLS) aboard NASA's Aura satellite. AIRS operational temperature retrievals are typically not used for studies of gravity waves, because their vertical and horizontal resolution is rather limited. This study uses data of a high-resolution retrieval which provides stratospheric temperature profiles for each individual satellite footprint. Therefore the horizontal sampling of the high-resolution retrieval is 9 times better than that of the operational retrieval. HIRDLS provides 2-D spectral information of observed gravity waves in terms of along-track and vertical wavelengths. AIRS as a nadir sounder is more sensitive to short-horizontal-wavelength gravity waves, and HIRDLS as a limb sounder is more sensitive to short-vertical-wavelength gravity waves. Therefore HIRDLS is ideally suited to complement AIRS observations. A calculated momentum flux factor indicates that the waves seen by AIRS contribute significantly to momentum flux, even if the AIRS temperature variance may be small compared to HIRDLS. The stratospheric wave structures observed by AIRS and HIRDLS often agree very well. Case studies of a mountain wave event and a non-orographic wave event demonstrate that the observed phase structures of AIRS and HIRDLS are also similar. AIRS has a coarser vertical resolution, which results in an attenuation of the amplitude and coarser vertical wavelengths than for HIRDLS. However, AIRS has a much higher horizontal resolution, and the propagation direction of the waves can be clearly identified in geographical maps. The horizontal orientation of the phase fronts can be deduced from AIRS 3-D temperature fields. This is a restricting factor for gravity wave analyses of limb measurements. Additionally, temperature variances with respect to stratospheric gravity wave activity are compared on a statistical basis. The complete HIRDLS measurement period from January 2005 to March 2008 is covered. The seasonal and latitudinal distributions of gravity wave activity as observed by AIRS and HIRDLS agree well. A strong annual cycle at mid- and high latitudes is found in time series of gravity wave variances at 42 km, which has its maxima during wintertime and its minima during summertime. The variability is largest during austral wintertime at 60° S. Variations in the zonal winds at 2.5 hPa are associated with large variability in gravity wave variances. Altogether, gravity wave variances of AIRS and HIRDLS are complementary to each other. Large parts of the gravity wave spectrum are covered by joint observations. This opens up fascinating vistas for future gravity wave research.

A modelling study of the influence of anomalous wind forcing over the Barents Sea on the Atlantic water flow to the Arctic Ocean in the period 1979-2004

NASA Astrophysics Data System (ADS)

Marciniak, Jakub; Schlichtholz, Pawel; Maslowski, Wieslaw

2016-04-01

Arctic climate system is influenced by oceanic heat transport with the Atlantic water (AW) streaming towards the Arctic Ocean in two branches, through the deep Fram Strait and the shallow Barents Sea. In Fram Strait, the AW submerges below the Polar surface water and then flows cyclonically along the margin of the Arctic Ocean as a subsurface water mass in the Arctic Slope Current. In contrast to the Fram Strait branch, which is the major source of heat for the Arctic Ocean, most of the heat influx to the Barents Sea through the Barents Sea opening (BSO) is passed to the atmosphere. Only cold remnants of AW outflow to the Arctic Ocean through the northeastern gate of the Barents Sea. Some AW entering the Barents Sea recirculates westward, contributing to an outflow from the Barents Sea through the BSO along the shelf slope south of Bear Island, in the Bear Island Slope Current. Even though the two-branched AW flow toward the Arctic Ocean has been known for more than a century, little is known about co-variability of heat fluxes in the two branches, its mechanisms and climatic implications. Recent studies indicate that the Bear Island Slope Current may play a role in this co-variability. Here, co-variability of the flow through the BSO and Fram Strait is investigated using a pan-Arctic coupled ice-ocean hindcast model run for the period 1979-2004 and forced with daily atmospheric data from the ECMWF. Significant wintertime co-variability between the volume transport in the Bear Island and Arctic slope currents and its link to wind forcing over the Barents Sea is confirmed. It is found that the volume transports in these currents are, however, not correlated in the annual mean and that the wintertime co-variability of these currents has no immediate effect on either the net heat flux through the BSO or the net heat flux divergence in the Barents Sea. It is shown that the main climatic effect of wind forcing over the northern Barents Sea shelf is to induce temperature anomalies in the Murman/West Novaya Zemlya current system on the eastern side of the Barents Sea. These anomalies affect sea ice in the eastern Barents Sea 1-3 months later, but are not completely lost on the interactions with the sea ice and local atmosphere. Statistically significant subsurface temperature anomalies driven by anomalous winds over the Barents Sea join, on their exit to the Arctic Ocean through St. Anna Trough, the Arctic Slope Current, in which they persist for several years.

An Investigation of the Effects of Black Carbon on Precipitation in the Western United States

NASA Astrophysics Data System (ADS)

Tseng, Hsien-Liang Rose

Black carbon (BC), the byproduct of incomplete combustion, is considered to be the second most important anthropogenic climate forcing agent after carbon dioxide. BC warms the atmosphere by absorbing solar radiation (direct effect), alters cloud and precipitation formation by acting as cloud condensation nuclei (indirect effect), and modifies cloud distribution via cloud burn-off (semi-direct effect). Currently, there are large discrepancies in general circulation model estimates of the influence of BC on precipitation. Even less known is how BC changes precipitation on regional scales. In the drought-stricken western United States (WUS), where BC emissions are known to affect the hydrological cycle, an investigation on how BC influences precipitation is warranted. In this study, we employ the Weather Research and Forecasting-Chemistry (WRF Chem) model (version 3.6.0) with the newly chemistry- and microphysics-coupled Fu-Liou-Gu radiation scheme to study how black carbon affects precipitation by separating BC-related effects into direct and semi-direct, and indirect effects. In this three-part study, we use a recent wet year (2005) to investigate black carbon effects. We first examine BC effects during a heavy wintertime heavy precipitation event (7-11 January 2005), a heavy summertime precipitation week for comparison to the wintertime event (20-24 July 2005), and finally, examine these same effects for the months of January to June 2005 to investigate month-long trends. We find that BC suppresses precipitation, predominantly through its direct and semi-direct effects. The direct and semi-direct effects warm the air aloft, and cool the lower levels of the atmosphere (surface dimming) through the reduction of downward shortwave radiation flux at the surface. These changes in vertical temperature increase the stability of the atmosphere and reduce convective precipitation. Convective precipitation reduction accounts for approximately 60 75% of the total precipitation reduction. Additionally, cooling in the lower levels reduces evaporation from the surface, which reduces the moisture needed for non-convective precipitation. Subsequently, reduced moisture in the atmosphere suppresses non-convective precipitation by approximately 10-40%. The indirect effects also reduce precipitation, but to a much smaller extent of 5-20%. Although we use an atypical BC emission dataset is used in this study, the resulting reduction of the different types of precipitation sheds light on the physical mechanisms of BC-cloud-radiation interactions by which the reductions follow. In particular, our results highlight the importance of the cumulus and surface layer parameterizations that house the triggering mechanism and surface moisture flux parameterizations in future studies. In this research we find the NEI 2005 emissions did not significantly change precipitation. This is likely due to the aggressive emission regulations that exist for the United States. Emission regulations, however, do not exist or are enforced equally across the globe. In the developing countries that rely on inefficient cook stoves and heating systems, the populations suffer the most due to black carbon emission. Along with respiratory and cardiovascular impacts from black carbon, they may suffer from reduced water resources from suppressed precipitation, as well. In a larger sense, findings from this research serve as a platform for understanding the wider-reaching effects of black carbon on regional precipitation and drought. In particular, in areas where there are no black carbon emission regulations, this would highlight health and potentially significant environmental benefits that could be achieved from a black carbon cap and trade.

Quantifying Observed Temperature Extremes in the Southeastern United States

NASA Astrophysics Data System (ADS)

Sura, P.; Stefanova, L. B.; Griffin, M.; Worsnop, R.

2011-12-01

There is broad consensus that the most hazardous effects of climate change are related to a potential increase (in frequency and/or intensity) of extreme weather and climate events. In particular, the statistics of regional daily temperature extremes are of practical interest for the agricultural community and energy suppliers. This is notably true for the Southeastern United States where winter hard freezes are a relatively rare and potentially catastrophic event. Here we use a long record of quality-controlled observations collected from 272 National Weather Service (NWS) Cooperative Observing Network (COOP) stations throughout Florida, Georgia, Alabama, and South and North Carolina to provide a detailed climatology of temperature extremes in the Southeastern United States. We employ two complementary approaches. First, we analyze the effect of El Nino-Southern Oscillation (ENSO) and the Arctic Oscillation (AO) on the non-Gaussian (i.e. higher order) statistics of wintertime daily minimum and maximum temperatures. We find a significant and spatially varying impact of ENSO and AO on the non-Gaussian statistics of daily maximum and minimum temperatures throughout the domain. Second, the extremes of the temperature distributions are studied by calculating the 1st and 99th percentiles, and then analyzing the number of days with record low/high temperatures per season. This analysis of daily temperature extremes reveals oscillating, multi-decadal patterns with spatially varying centers of action.

An anatomy of the projected North Atlantic warming hole in CMIP5 models

NASA Astrophysics Data System (ADS)

Menary, Matthew B.; Wood, Richard A.

2018-04-01

Global mean surface air temperature has increased over the past century and climate models project this trend to continue. However, the pattern of change is not homogeneous. Of particular interest is the subpolar North Atlantic, which has cooled in recent years and is projected to continue to warm less rapidly than the global mean. This is often termed the North Atlantic warming hole (WH). In climate model projections, the development of the WH is concomitant with a weakening of the Atlantic meridional overturning circulation (AMOC). Here, we further investigate the possible link between the AMOC and WH and the competing drivers of vertical mixing and surface heat fluxes. Across a large ensemble of 41 climate models we find that the spatial structure of the WH varies considerably from model to model but is generally upstream of the simulated deep water formation regions. A heat budget analysis suggests the formation of the WH is related to changes in ocean heat transport. Although the models display a plethora of AMOC mean states, they generally predict a weakening and shallowing of the AMOC also consistent with the evolving depth structure of the WH. A lagged regression analysis during the WH onset phase suggests that reductions in wintertime mixing lead a weakening of the AMOC by 5 years in turn leading initiation of the WH by 5 years. Inter-model differences in the evolution and structure of the WH are likely to lead to somewhat different projected climate impacts in nearby Europe and North America.

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.

Minimizing the wintertime low bias of Northern Hemisphere carbon monoxide in global model simulations

NASA Astrophysics Data System (ADS)

Stein, Olaf; Schultz, Martin G.; Bouarar, Idir; Clark, Hannah; Huijnen, Vincent; Gaudel, Audrey; George, Maya; Clerbaux, Cathy

2015-04-01

Carbon monoxide (CO) is a product of incomplete combustion and is also produced from oxidation of volatile organic compounds (VOC) in the atmosphere. It is of interest as an indirect greenhouse gas and an air pollutant causing health effects and is thus subject to emission restrictions. CO acts as a major sink for the OH radical and as a precursor for tropospheric ozone and affects the oxidizing capacity of the atmosphere as well as regional air quality. Despite the developments in the global modelling of chemistry and of the parameterization of the physical processes, CO concentrations remain underestimated during NH winter by most state-of-the-art chemical transport models. The resulting model bias can in principle originate from either an underestimation of CO sources or an overestimation of its sinks. We address both the role of sources and sinks with a series of MOZART chemistry transport model sensitivity simulations for the year 2008 and compare our results to observational data from ground-based stations, satellite observations, and from MOZAIC tropospheric profile measurements on passenger aircraft. Our base case simulation using the MACCity emission inventory (Granier et al. 2011) underestimates the near-surface Northern Hemispheric CO mixing ratios by more than 20 ppb from December to April with a maximal bias of 40 ppb in January. The bias is strongest for the European region (up to 75 ppb in January). From our sensitivity studies the mismatch between observed and modelled atmospheric CO concentrations can be explained by a combination of the following emission inventory shortcuts: (i) missing anthropogenic wintertime CO emissions from traffic or other combustion processes, (ii) missing anthropogenic VOC emissions, (iii) an exaggerated downward trend in the RCP8.5 scenario underlying the MACCity inventory, (iv) a lack of knowledge about the seasonality of emissions. Deficiencies in the parameterization of the dry deposition velocities can also lead to underestimations of Northern Hemisphere wintertime CO concentrations which are in the same order than those from the current emission inventories. A methane lifetime of 9.7 yr for our basic model and 9.8 yr for the optimized simulation agrees well with current estimates of global OH, but we cannot fully exclude a potential effect from errors in the geographical and seasonal distribution of OH concentrations on the modelled CO. References: Granier C. et al., Evolution of anthropogenic and biomass burning emissions of air pollutants at global and regional scales during the 1980-2010 period, Climatic Change, doi:10.1007/s10584-011-0154-1, 2011. Stein, O., Schultz, M. G., Bouarar, I., Clark, H., Huijnen, V., Gaudel, A., George, M., and Clerbaux, C.: On the wintertime low bias of Northern Hemisphere carbon monoxide found in global model simulations, Atmos. Chem. Phys., doi:10.5194/acp-14-9295-2014, 2014.

Winter Storm Jupiter of January 2017: Meteorological Drivers, Synoptic Evolution, and Climate Change Considerations in Portland, Oregon

NASA Astrophysics Data System (ADS)

Dean, S.; Loikith, P. C.

2017-12-01

Although the Pacific Northwest has some of the highest wintertime precipitation in the United States, most urban areas receive little in the way of snow. While 37 inches of wintertime rain fall in Portland on average annually, the city only receives four inches of snow on average. Although wintertime extreme snowstorm events are rare in Portland, in the last century they have occurred about once every ten years. On January 10-12th, 2017, winter storm Jupiter brought 11 inches of snow to downtown Portland within a 12-hour period, making it the largest snowstorm for the city in twenty years. The city declared a state of emergency, over 30,000 citizens lost power, and thousands of businesses were forced to shut down. The anomalously cold air and high amounts of snowfall in a short amount of time made the storm different from others in recent years. This study aims to discover the meteorological drivers behind the January 2017 snowstorm in Portland, Oregon. We also aim to understand how this storm compared with other local storms in the past, and assess the likelihood of a similar event occurring in the future. To do this, reanalysis data were used to display the synoptic evolution of the January 2017 storm. We compared this storm with two other extreme snowfall events from December 2008 and January 1980, assessing meteorological similarities and differences between storms. Results show that the 2017 event was associated with a slow moving, strong low-pressure system accompanied by a 500 hPa trough. These large-scale features helped drive slow moving, locally heavy snow bands over the city of Portland. At the same time, an unusually strong Arctic high-pressure system moved into the interior Pacific Northwest allowing for strong cold air advection west through the Cascade Mountain Range and Columbia River Gorge. Temperature trends show warming of 1-2 °C in the Pacific Northwest since the middle of the last century. Because of this, uncertainty associated with occurrence and magnitude of extreme snowfall events with respect to climate change must also be assessed. Understanding essential questions about the synoptic evolution of extreme snowfall events will better equip meteorologists and city planners to understand how this event occurred, and what to look for to better prepare Pacific Northwest cities for future storms.

Cold-related mortality vs heat-related mortality in a changing climate: A case study in Vilnius (Lithuania).

PubMed

Martinez, Gerardo Sanchez; Diaz, Julio; Hooyberghs, Hans; Lauwaet, Dirk; De Ridder, Koen; Linares, Cristina; Carmona, Rocio; Ortiz, Cristina; Kendrovski, Vladimir; Adamonyte, Dovile

2018-06-21

Direct health effects of extreme temperatures are a significant environmental health problem in Lithuania, and could worsen further under climate change. This paper attempts to describe the change in environmental temperature conditions that the urban population of Vilnius could experience under climate change, and the effects such change could have on excess heat-related and cold-related mortality in two future periods within the 21st century. We modelled the urban climate of Vilnius for the summer and winter seasons during a sample period (2009-2015) and projected summertime and wintertime daily temperatures for two prospective periods, one in the near (2030-2045) and one in the far future (2085-2100), under the Representative Concentration Pathway (RCP) 8.5. We then analysed the historical relationship between temperature and mortality for the period 2009-2015, and estimated the projected mortality in the near future and far future periods under a changing climate and population, assuming alternatively no acclimatisation and acclimatisation to heat and cold based on a constant-percentile threshold temperature. During the sample period 2009-2015 in summertime we observed an increase in daily mortality from a maximum daily temperature of 30 °C (the 96th percentile of the series), with an average of around 7 deaths per year. Under a no acclimatisation scenario, annual average heat-related mortality would rise to 24 deaths/year (95% CI: 8.4-38.4) in the near future and to 46 deaths/year (95% CI: 16.4-74.4) in the far future. Under a heat acclimatisation scenario, mortality would not increase significantly in the near or in the far future. Regarding wintertime cold-related mortality in the sample period 2009-2015, we observed increased mortality on days on which the minimum daily temperature fell below - 12 °C (the 7th percentile of the series), with an average of around 10 deaths a year. Keeping the threshold temperature constant, annual average cold-related mortality would decrease markedly in the near future, to 5 deaths/year (95% CI: 0.8-7.9) and even more in the far future, down to 0.44 deaths/year (95% C: 0.1-0.8). Assuming a "middle ground" between the acclimatisation and non-acclimatisation scenarios, the decrease in cold-related mortality will not compensate the increase in heat-related mortality. Thermal extremes, both heat and cold, constitute a serious public health threat in Vilnius, and in a changing climate the decrease in mortality attributable to cold will not compensate for the increase in mortality attributable to heat. Study results reinforce the notion that public health prevention against thermal extremes should be designed as a dynamic, adaptive process from the inception. Copyright © 2018 Elsevier Inc. All rights reserved.

Bioclimatic conditions of the winter months in Western Kazakhstan and their dynamics in relation to climate change

NASA Astrophysics Data System (ADS)

Nyssanbayeva, Aiman S.; Cherednichenko, Alexandr V.; Cherednichenko, Vladimir S.; Abayev, Nurlan N.; Madibekov, Azamat S.

2018-03-01

The territory of West Kazakhstan is an intensively developing region. The main oil and gas fields are concentrated there. In addition, this region is well-known as a region of nomad cattle breeding. Both of industry and agriculture demand a lot of employees, working in the open air in wintertime. Severe winter conditions, primary very low temperatures, and strong winds characterize the region. In this work, we calculated and analyzed the spatial and temporal distributions of effective temperatures in the region and their dynamics due to the global warming in the last decades. To calculate the equivalent temperature (WCET) was used the method of OFCM 2003. Nowadays, it is known as a common method for similar studies. It was shown that in the observed region, WCET is significantly lower than the ambient temperature. Repeatability of WCET, corresponding to «increasing risk», «high risk» is high in the main part of the region. Global warming in the region results in returning extremely high temperatures of the air, decreasing repeatability of the average gradation of WCET approximately on 4%, but there is no any visible changing repeatability of extreme WCET. Obtained results can be used for planning any construction work in the open air and agriculture branches.

Bioclimatic conditions of the winter months in Western Kazakhstan and their dynamics in relation to climate change.

PubMed

Nyssanbayeva, Aiman S; Cherednichenko, Alexandr V; Cherednichenko, Vladimir S; Abayev, Nurlan N; Madibekov, Azamat S

2018-03-05

The territory of West Kazakhstan is an intensively developing region. The main oil and gas fields are concentrated there. In addition, this region is well-known as a region of nomad cattle breeding. Both of industry and agriculture demand a lot of employees, working in the open air in wintertime. Severe winter conditions, primary very low temperatures, and strong winds characterize the region. In this work, we calculated and analyzed the spatial and temporal distributions of effective temperatures in the region and their dynamics due to the global warming in the last decades. To calculate the equivalent temperature (WCET) was used the method of OFCM 2003. Nowadays, it is known as a common method for similar studies. It was shown that in the observed region, WCET is significantly lower than the ambient temperature. Repeatability of WCET, corresponding to «increasing risk», «high risk» is high in the main part of the region. Global warming in the region results in returning extremely high temperatures of the air, decreasing repeatability of the average gradation of WCET approximately on 4%, but there is no any visible changing repeatability of extreme WCET. Obtained results can be used for planning any construction work in the open air and agriculture branches.

Daily Kilometer-Scale MODIS Satellite Maps of PM2.5 Describe Wintertime Episodes

NASA Technical Reports Server (NTRS)

Chatfield, Robert B.; Sorek Hamer, Meytar; Lyapustin, Alexei; Wang, Yujie

2017-01-01

The San Joaquin Valley (SJV) suffers from severe health-endangering episodes of PM2.5 aerosol loadings in wintertime; episodes last approximately 5 days and differ in geographical distribution and composition. PM2.5 stations are scattered; consequently the use of remote sensing to map variable regional patterns of these varying respirable aerosol concentrations is desirable. High-precision AOT retrievals can capture column particulate loading. However,PM2.5 mapping is challenging due to several reasons: particularly thin mixed layers (ML) and thus relatively low aerosol optical thickness (AOT) close to current measurement limits, variable and a typical composition of the aerosols, and complex surface bidirectional reflectance. However, the West does present some advantages in analysis. Air basins are isolated from long-distance transport, and experience predominant strong meteorological subsidence. Thus these Western basin regions have fewer problematic cases of overriding aerosol layers detached from the surface. To counter such local overriding, Chu et al. have described an approach for the Eastern US, and He et al have described a synoptic classification approach useful in Shanghai. The Bay Area Air Quality Management District (BAAQMD) expands our experience with the use of AOT, with lower PM2.5 and several isolated sub-basins. We have prepared daily maps of episodes in each region. We present also a sequence of increasingly detailed statistical models, AOT initially appears to contribute little information; however, inclusion of weather information reveals its utility. Lyapustin and Wang's MultiAngle Implementation of Atmospheric Correction (MAIAC) retrieval for AOT provided the most useful operational remote sensing information for these regions. It provides high (1-km) spatial resolution maps and a high percentage of availability. Empirical regression methods have found that random effects regression models (aka mixed effects models, ME) employing AOT provide good estimates of ground PM2.5 concentrations.Here, we attempt to extend these methods and evaluate the usefulness of AOT with greater physical analysis, based on DISCOVER-AQ4 experience.

Enhancement of PM2.5 Concentrations by Aerosol-Meteorology Interactions Over China

NASA Astrophysics Data System (ADS)

Zhang, Xin; Zhang, Qiang; Hong, Chaopeng; Zheng, Yixuan; Geng, Guannan; Tong, Dan; Zhang, Yuxuan; Zhang, Xiaoye

2018-01-01

Aerosol-meteorology interactions can change surface aerosol concentrations via different mechanisms such as altering radiation budget or cloud microphysics. However, few studies investigated the impacts of different mechanisms on temporal and spatial distribution of PM2.5 concentrations over China. Here we used the fully coupled Weather Research and Forecasting model with online chemistry (WRF-Chem) to quantify the enhancement of PM2.5 concentrations by aerosol-meteorology feedback in China in 2014 for different seasons and separate the relative impacts of aerosol radiation interactions (ARIs) and aerosol-cloud interactions (ACIs). We found that ARIs and ACIs could increase population-weighted annual mean PM2.5 concentration over China by 4.0 μg/m3 and 1.6 μg/m3, respectively. We found that ARIs play a dominant role in aerosol-meteorology interactions in winter, while the enhancement of PM2.5 concentration by ARIs and ACIs is comparable in other three seasons. ARIs reduced the wintertime monthly mean wind speed and planetary boundary layer (PBL) height by up to 0.1 m/s and 160 m, respectively, but increased the relative humidity by up to 4%, leading to accumulation of pollutants within PBL. Also, ARIs reduced dry deposition velocity of aerosols by up to 20%, resulting in an increase in PM2.5 lifetime and concentrations. ARIs can increase wintertime monthly mean surface PM2.5 concentration by a maximum of 30 μg/m3 in Sichuan Basin. ACIs can also increase PM2.5 concentration with more significant impacts in wet seasons via reduced wet scavenging and enhanced in-cloud chemistry. Dominant processes in PM2.5 enhancement are also clarified in different seasons. Results show that physical process is more important than chemical processes in winter in ARIs, while chemical process of secondary inorganic aerosols production may be crucial in wet seasons via ACIs.

On the Mechanisms Linking Nitrogen Oxides to Trends in Ammonium Nitrate Aerosol over the Last Decade in the San Joaquin Valley

NASA Astrophysics Data System (ADS)

Pusede, S. E.; Zhang, Q.; Parworth, C.; Kim, H.; Shusterman, A.; Saleh, A.; Duffey, K.; Wooldridge, P. J.; Valin, L. C.; Fried, A.; Nowak, J. B.; Crawford, J. H.; Cohen, R. C.

2014-12-01

Nitrogen oxide (NOx) abundances across the U.S. have fallen steadily over the last fifteen years. Patterns in anthropogenic sources result in 2-fold lower NOx on weekends than weekdays largely without co-occurring changes in other emissions. These trends taken together provide a near perfect NOx constraint on the nonlinear chemistry of ozone, on the key oxidants nitrate radical (NO3) and hydroxyl radical (OH), and on secondary aerosol formation. We use this NOx constraint to interpret trends in wintertime PM2.5 over the last decade in San Joaquin Valley, California, a location with severe aerosol pollution and where a large portion of the total aerosol mass is ammonium nitrate (NH4NO3). We combine the 12-year routine monitoring record and the air- and ground-based DISCOVER-AQ-2013 datasets to quantify the impact of NOx emission controls on the frequency of wintertime exceedances of the national PM2.5 standard. Nitrate ion (NO3-) is the oxidation product of NO2 and is formed by distinct daytime and nighttime pathways, both of which are nonlinear functions of the NO2 abundance. We present observationally derived decadal trends in both pathways and show that NOx reductions have worked to simultaneously increase daytime and decrease nighttime NH4NO3 production over the last 15 years. The net effect has been a substantial decrease in NH4NO3 via decreased NO3-radical initiated production in the nocturnal residual layer, a layer largely separated from nighttime emissions at the surface. Whereas NO3- production in the nocturnal residual layer drove NH4NO3 chemistry over the last decade, OH-initiated chemistry at the surface is poised to be the most important source of NH4NO3 in the next decade.

Temperature threshold of isoprene emission from tropical trees, Ficus virgata and Ficus septica.

PubMed

Oku, Hirosuke; Inafuku, Masashi; Takamine, Tomonori; Nagamine, Maki; Saitoh, Seikoh; Fukuta, Masakazu

2014-01-01

This paper describes the existence of temperature threshold in isoprene emission from tropical trees for the first time. Isoprene emission capacity of Ficus virgata leaves kept outdoors were measured over a period of 20 d in the wintertime. When the plants experienced the low temperature below 12 °C in the daytime, isoprene emission was completely suppressed, and re-activated by elevated temperature above the threshold of 12 °C. Photosynthesis is also decreased similarly, but too much smaller extent compared to the reduction observed for isoprene emission. The cut off level of accumulated temperature to shut off the isoprene emission was roughly estimated to be 300 degree/d. The shut off in the isoprene emission by the low temperature was confirmed experimentally by use of phytotron with tropical trees of F. virgata and F. septica. Isoprene emission of both species ceased at 12 °C, and re-activated by raising the temperature above the threshold level. Photosynthesis was lowered slightly as was the case for the field observation, and no close association between photosynthesis and isoprene emission was noted. The expression of isoprene synthase gene showed much greater variation after exposure to the cold temperature compared to those involved in photosynthesis. These observations therefore suggested the existence of putative direct connection between perception of temperature and isoprene emission in tropical trees, which may merit further investigation to estimate the net output of isoprene from subtropical or tropical forest. Copyright © 2013 Elsevier Ltd. All rights reserved.

Online molecular characterization of fine particulate matter in Port Angeles, WA: Evidence for a major impact from residential wood smoke

NASA Astrophysics Data System (ADS)

Gaston, Cassandra J.; Lopez-Hilfiker, Felipe D.; Whybrew, Lauren E.; Hadley, Odelle; McNair, Fran; Gao, Honglian; Jaffe, Daniel A.; Thornton, Joel A.

2016-08-01

We present on-line molecular composition measurements of wintertime particulate matter (PM) during 2014 using an iodide-adduct high-resolution, time-of-flight chemical ionization mass spectrometer (HR-TOF-CIMS) coupled to a Filter Inlet for Gases and AEROsols (FIGAERO). These measurements were part of an intensive effort to characterize PM in the region with a focus on ultrafine particle sources. The technique was used to detect and quantify different classes of wood burning tracers, including levoglucosan, methoxyphenols, and nitrocatechols, among other compounds in near real-time. During the campaign, particulate mass concentrations of compounds with the same molecular composition as levoglucosan ranged from 0.002 to 19 μg/m3 with a median mass concentration of 0.9 μg/m3. Wood burning markers, in general, showed a strong diurnal pattern peaking at night and in the early morning. This diurnal profile combined with cold, stagnant conditions, wind directions from predominantly residential areas, and observations of lower combustion efficiency at night support residential wood burning as a dominant source of wintertime PM in Port Angeles. This finding has implications for improving wintertime air quality in the region by encouraging the use of high efficiency wood-burning stoves or other cleaner home heating options throughout the relevant domain.

Rising Variance and Synchrony across Marine and Terrestrial Ecosystems of Western North America

NASA Astrophysics Data System (ADS)

Black, B.; Di Lorenzo, E.

2016-12-01

Along the west coast of North America, the strength of the wintertime North Pacific High (NPH) is closely linked to wintertime upwelling in the California Current, and thus to various upper-trophic indicators of ecosystem productivity including seabird breeding success, fish growth-increment chronologies, and a copepod community index. The wintertime NPH also affects the Pacific storm track and thus precipitation and tree growth on land. Over the past century, variance of the winter NPH has risen and coincided with rising variance of drought, river discharge, upwelling, and sea level indicators. Moreover, synchrony within and among these indicators has also increased, especially on land where synchrony is further magnified by long-term warming trends. Rising synchrony is also imprinted on biological time series, including rockfish chronologies and a network of moisture-sensitive blue oak chronologies, which have risen to their highest levels of synchrony in at least the past four centuries. The ultimate drivers of rising NPH variance appears to be rising variability in the El Niño Southern Oscillation and more efficient coupling between the tropical and extra-tropics. These results suggest that rising climate variance is increasingly limiting biological variability with implications for ecosystem resilience and degree of coupling across the land-sea interface.

St. Petersburg, Russia as seen from STS-60

NASA Technical Reports Server (NTRS)

1994-01-01

This wintertime photograph shows the large city of St. Petersburg, Russia at the head of the Gulf of Finland. The city, built by Peter the Great, is situated in the former swampy delta of the Neva River which connects the large Lake Ladoga (the frozen white surface on the edge of the photograph) to the Gulf of Finland. An interesting feature of St. Petersburg which can be discerned in this photograph is the new storm surge barrier built from both sides of the Gulf of Finland out to the island of Kronstadt in the middle. Also visible as a thin line between Kronstadt and St. Petersburg is the ice-free shipping channel kept open much of the winter. Power plant plumes are also visible on the frame.

Wintertime urban heat island modified by global climate change over Japan

NASA Astrophysics Data System (ADS)

Hara, M.

2015-12-01

Urban thermal environment change, especially, surface air temperature (SAT) rise in metropolitan areas, is one of the major recent issues in urban areas. The urban thermal environmental change affects not only human health such as heat stroke, but also increasing infectious disease due to spreading out virus vectors habitat and increase of industry and house energy consumption. The SAT rise is mostly caused by global climate change and urban heat island (hereafter UHI) by urbanization. The population in Tokyo metropolitan area is over 30 millions and the Tokyo metropolitan area is one of the biggest megacities in the world. The temperature rise due to urbanization seems comparable to the global climate change in the major megacities. It is important to project how the urbanization and the global climate change affect to the future change of urban thermal environment to plan the adaptation and mitigation policy. To predict future SAT change in urban scale, we should estimate future UHI modified by the global climate change. This study investigates change in UHI intensity (UHII) of major metropolitan areas in Japan by effects of the global climate change. We performed a series of climate simulations. Present climate simulations with and without urban process are conducted for ten seasons using a high-resolution numerical climate model, the Weather Research and Forecasting (WRF) model. Future climate projections with and without urban process are also conducted. The future projections are performed using the pseudo global warming method, assuming 2050s' initial and boundary conditions estimated by a GCM under the RCP scenario. Simulation results indicated that UHII would be enhanced more than 30% in Tokyo during the night due to the global climate change. The enhancement of urban heat island is mostly caused by change of lower atmospheric stability.

Soil Biogeochemistry in a Changing Climate: Effect of Snow Removal

NASA Astrophysics Data System (ADS)

Patel, K.; Tatariw, C.; Fernandez, I. J.; Macrae, J. D.; Ohno, T.

2016-12-01

Winter snowpack plays an important role in ecosystem functioning, thermally insulating the subnivean soil from freezing temperatures. Wintertime microbial mineralization of organic material results in accumulation of nutrients under the snowpack, which are available post-melt for plant root uptake. The northeastern United States has experienced declining snow accumulation, and climate models project this trend will continue in the future. Intermittent and reduced snow cover increases soil freezing and frost damage, which can have implications on spring nutrient availability and forest productivity. We conducted a 2-year snow removal experiment in the Dwight B. DeMeritt Forest at the University of Maine to study subnivean winter processes, and to examine the effect of a decreased snowpack on soil winter and spring biogeochemistry. Surface organic soils were collected during winter and spring of 2015 and 2016, years with sharply contrasting snow accumulation, to track temporal changes in nutrient dynamics as the system evolved from under the snowpack. Laboratory extractions and incubations were performed to quantify the inorganic available nitrogen, dissolved organic carbon (DOC), and potential net N-mineralization (PNNM) in field moist soils. Snow removal resulted in decreased winter soil temperatures (2-8°C colder than the reference plots). There was an increased incidence of rain-on-soil events in the winter, forming concrete frost. Freeze-thaw cycles in the treatment plots resulted in higher NH4-N and DOC concentrations, but lower PNNM, compared to the reference plots. Treatment effects on DOC and NH4-N concentrations were not seen in the spring, although the effects on PNNM persisted. Our findings demonstrated that freeze-thaw cycles play an important role in the timing and magnitude of soil nutrient availability during the vernal transition. Understanding these processes becomes increasingly important when defining forest ecosystem response to a changing climate.

Year-round simulated methane emissions from a permafrost ecosystem in Northeast Siberia

NASA Astrophysics Data System (ADS)

Castro-Morales, Karel; Kleinen, Thomas; Kaiser, Sonja; Zaehle, Sönke; Kittler, Fanny; Kwon, Min Jung; Beer, Christian; Göckede, Mathias

2018-05-01

Wetlands of northern high latitudes are ecosystems highly vulnerable to climate change. Some degradation effects include soil hydrologic changes due to permafrost thaw, formation of deeper active layers, and rising topsoil temperatures that accelerate the degradation of permafrost carbon and increase in CO2 and CH4 emissions. In this work we present 2 years of modeled year-round CH4 emissions into the atmosphere from a Northeast Siberian region in the Russian Far East. We use a revisited version of the process-based JSBACH-methane model that includes four CH4 transport pathways: plant-mediated transport, ebullition and molecular diffusion in the presence or absence of snow. The gas is emitted through wetlands represented by grid cell inundated areas simulated with a TOPMODEL approach. The magnitude of the summertime modeled CH4 emissions is comparable to ground-based CH4 fluxes measured with the eddy covariance technique and flux chambers in the same area of study, whereas wintertime modeled values are underestimated by 1 order of magnitude. In an annual balance, the most important mechanism for transport of methane into the atmosphere is through plants (61 %). This is followed by ebullition ( ˜ 35 %), while summertime molecular diffusion is negligible (0.02 %) compared to the diffusion through the snow during winter ( ˜ 4 %). We investigate the relationship between temporal changes in the CH4 fluxes, soil temperature, and soil moisture content. Our results highlight the heterogeneity in CH4 emissions at landscape scale and suggest that further improvements to the representation of large-scale hydrological conditions in the model will facilitate a more process-oriented land surface scheme and better simulate CH4 emissions under climate change. This is especially necessary at regional scales in Arctic ecosystems influenced by permafrost thaw.

Seismic Signatures of Brine Release at Blood Falls, Taylor Glacier, Antarctica

NASA Astrophysics Data System (ADS)

Carr, C. G.; Pettit, E. C.; Carmichael, J.

2017-12-01

Blood Falls is created by the release of subglacially-sourced, iron-rich brine at the surface of Taylor Glacier, McMurdo Dry Valleys, Antarctica. The supraglacial portion of this hydrological feature is episodically active. Englacial liquid brine flow occurs despite ice temperatures of -17°C and we document supraglacial liquid brine release despite ambient air temperatures average -20°C. In this study, we use data from a seismic network, time-lapse cameras, and publicly available weather station data to address the questions: what are the characteristics of seismic events that occur during Blood Falls brine release and how do these compare with seismic events that occur during times of Blood Falls quiescence? How are different processes observable in the time-lapse imagery represented in the seismic record? Time-lapse photography constrains the timing of brine release events during the austral winter of 2014. We use a noise-adaptive digital power detector to identify seismic events and cluster analysis to identify repeating events based on waveform similarity across the network. During the 2014 wintertime brine release, high-energy repeated seismic events occurred proximal to Blood Falls. We investigate the ground motions associated with these clustered events, as well as their spatial distribution. We see evidence of possible tremor during the brine release periods, an indicator of fluid movement. If distinctive seismic signatures are associated with Blood Falls brine release they could be identified based solely on seismic data without any aid from time-lapse cameras. Passive seismologic monitoring has the benefit of continuity during the polar night and other poor visibility conditions, which make time-lapse imagery unusable.

Effect of en-glacial water on ice sheet temperatures in a warming climate - a model approach

NASA Astrophysics Data System (ADS)

Phillips, T. P.; Rajaram, H.; Steffen, K.

2009-12-01

Each summer, significant amount of melt is generated in the ablation zones of large glaciers and ice sheets. This melt does not run off on the surface of the glacier or ice sheet. In fact a significant fraction enters the glacier and flows through en-glacial and sub-glacial hydrologic systems. Correspondingly, the en-glacial and sub-glacial hydrologic systems are brought to a temperature close to the pressure melting point of ice. The thermal influence of these hydrologic processes is seldom incorporated in heat transfer models for glaciers and ice sheets. In a warming climate, as melt water generation is amplified, en-glacial and sub-glacial hydrologic processes can influence the thermal dynamics of an ice sheet significantly, a feedback which is missed in current models. Although the role of refreezing melt water in the firn of the accumulation zone is often accounted for to explain warmer near-surface temperatures, the role of melt water flow within a glacier is not considered in large ice sheet models. We propose a simple parameterization of the influence of en-glacial and sub-glacial hydrology on the thermal dynamics of ice sheets, in the form of a dual-column model. Our model basically modifies the classical Budd column model for temperature variations in ice sheets by introducing an interaction with an en-glacial column, where the temperature is brought to the melting point during the melt season, and winter-time refreezing is influenced by latent heat effects associated with water retained within the en-glacial and sub-glacial systems. A cryo-hydraulic heat exchange coefficient ς is defined, as a parameter that quantifies this interaction. The parameter ς is related to k/R^2, where R is the characteristic spacing between en-glacial passages. The general behavior of the dual-column model is influenced by the competition between cooling by horizontal advection and warming by cryo-hydraulic exchange. We present a dimensionless parameter to quantify this competition. Model simulations indicate that the combination of en-glacial water flow and winter snow cover can warm the ice and produce a higher steady state en-glacial temperature. Transient simulations indicate a spin-up period of approximately 10 years until the new steady state is attained. The en-glacially trapped water prevents the ice from cooling as the Arctic winter approaches. As the water refreezes in the shallow ice, the snow cover reaches a thickness that insulates the ice and slows further cooling. The en-glacial temperature is highly dependent on the magnitude of the cryo-hydraulic term (warming) and the magnitude of the horizontal advection term (cooling) which control the newly reached balance. The dual-column model was applied to analyze deep borehole temperature profiles from five sites on Dead Glacier in western Greenland north of Jakobshavn Glacier. The model was able to explain some features of the borehole temperatures that cannot be explained by the conventional single column model.

Year-Long Vertical Velocity Statistics Derived from Doppler Lidar Data for the Continental Convective Boundary Layer

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

Berg, Larry K.; Newsom, Rob K.; Turner, David D.

One year of Coherent Doppler Lidar (CDL) data collected at the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) site in Oklahoma is analyzed to provide profiles of vertical velocity variance, skewness, and kurtosis for cases of cloud-free convective boundary layers. The variance was scaled by the Deardorff convective velocity scale, which was successful when the boundary layer depth was stationary but failed in situations when the layer was changing rapidly. In this study the data are sorted according to time of day, season, wind direction, surface shear stress, degree of instability, and wind shear across the boundary-layer top. Themore » normalized variance was found to have its peak value near a normalized height of 0.25. The magnitude of the variance changes with season, shear stress, and degree of instability, but was not impacted by wind shear across the boundary-layer top. The skewness was largest in the top half of the boundary layer (with the exception of wintertime conditions). The skewness was found to be a function of the season, shear stress, wind shear across the boundary-layer top, with larger amounts of shear leading to smaller values. Like skewness, the vertical profile of kurtosis followed a consistent pattern, with peak values near the boundary-layer top (also with the exception of wintertime data). The altitude of the peak values of kurtosis was found to be lower when there was a large amount of wind shear at the boundary-layer top.« less

Observations of high droplet number concentrations in Southern Ocean boundary layer clouds

NASA Astrophysics Data System (ADS)

Chubb, T.; Huang, Y.; Jensen, J.; Campos, T.; Siems, S.; Manton, M.

2015-09-01

Data from the standard cloud physics payload during the NSF/NCAR High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) Pole-to-Pole Observations (HIPPO) campaigns provide a snapshot of unusual wintertime microphysical conditions in the boundary layer over the Southern Ocean. On 29 June 2011, the HIAPER sampled the boundary layer in a region of pre-frontal warm air advection between 58 and 48° S to the south of Tasmania. Cloud droplet number concentrations were consistent with climatological values in the northernmost profiles but were exceptionally high for wintertime in the Southern Ocean at 100-200 cm-3 in the southernmost profiles. Sub-micron (0.0625 m s-1) were most likely responsible for production of sea spray aerosol which influenced the microphysical properties of the boundary layer clouds. The smaller size and higher number concentration of cloud droplets is inferred to increase the albedo of these clouds, and these conditions occur regularly, and are expected to increase in frequency, over windy parts of the Southern Ocean.

Dual effects of the winter monsoon on haze-fog variations in eastern China

NASA Astrophysics Data System (ADS)

Liu, Qian; Sheng, Lifang; Cao, Ziqi; Diao, Yina; Wang, Wencai; Zhou, Yang

2017-06-01

Previous studies have revealed a negative correlation between the East Asian winter monsoon and wintertime haze-fog events in China. The winter monsoon reduces haze-fog by advecting away aerosol particles and supplying clean air through cold waves. However, it is found that the frequency of haze-fog events on subseasonal time scales displays no correlation with typical winter monsoon indices. The results show that the accumulating and maintaining effects of calm weather related to the Siberian High, which is also a part of the monsoon circulation system, are equally important for the development of haze-fog events during winter. Correlation analysis indicates that subseasonal variations in haze-fog are closely related to the intensity of the Siberian High (r = 0.49). The Siberian High may increase the occurrence of haze-fog events by reducing the near surface wind speed and enhancing the stratification stability. To quantify the contribution of these diverse effects of the winter monsoon on the variations in haze-fog events, we analyzed haze-fog events during periods of cold wave activity and calm weather separately and contrasted the relative contributions of these two effects on different time scales. On the subseasonal scale, the effect of the Siberian High was 2.0 times that of cold waves; on the interannual scale, the effect of cold waves was 2.4 times that of the Siberian High. This study reveals the dual effects of the East Asian winter monsoon on wintertime haze-fog variations in eastern China and provides a more comprehensive understanding of the relationship between the monsoon and haze-fog events.

Influence of wintertime large-scale circulation on the explosively developing cyclones over the western North Pacific and their downstream effects

NASA Astrophysics Data System (ADS)

Yoshiike, Satoki; Kawamura, Ryuichi

2009-07-01

The relationships between large-scale wintertime circulation and extratropical cyclones that develop explosively (the so-called bomb cyclones) over the western North Pacific are investigated using Japanese long-term reanalysis project data. On a monthly basis, the East Asian winter monsoon variability strongly modulates the bomb cyclone activity in terms of its geographical distribution. When the monsoon is strong, the bomb cyclone activity tends to concentrate in the vicinity of the Kuroshio Current and the Kuroshio Extension near Japan, while when the monsoon is weak, it disperses over the broader areas. The enhancement of the monsoon increases the heat and moisture supply from warm currents, facilitating unstable conditions within the atmospheric boundary layer and intensifying baroclinicity in the lower troposphere. These factors are believed to play a role in inducing bomb cyclones, particularly along the warm currents. On submonthly timescales, the stationary Rossby wave propagation along the South Asian waveguide serves as a prominent trigger for the rapid reinforcement of synoptic-scale disturbances around Japan. When a pronounced bomb cyclone comes to its mature stage northeast of Japan, it is capable of exciting stationary Rossby waves downstream from the Asian jet exit region as vorticity forcing. The stationary wave packets developing southeastward across the North Pacific Ocean basin induce surface cyclogenesis in the vicinity of the Hawaiian Islands by leading to the equatorward advection of higher potential vorticity from the midlatitudes, bringing about the occurrence of kona storms, which cause weather hazards in Hawaii.

Peculiarities of the Bound Water and Water Ice Seasonal Variations in the Martian Surface Layer of the Regolith.

NASA Astrophysics Data System (ADS)

Kuzmin, R. O.; Zabalueva, E. V.; Evdokimova, N. A.; Christensen, P. H.; Mitrofanov, I. G.; Litvak, M. L.

2008-09-01

Introduction: The processes of the hydration/ dehydration of salt minerals within the Martian soil and the condensation/sublimation of water ice (and frost) in the surficial soil layer and on the polar cap surface play great significance in the modern water cycle on Mars and directly affect the redistribution of the water phases and forms in the system "atmosphere/regolith/polar caps" [1, 2, 3, 4, 5]. The processes are reversible in time and their intensity is strongly dependent on such time-variable climatic parameters as atmospheric and surface temperature, atmospheric water vapour content and specific features of atmospheric seasonal circulation [6, 7, 8, 9, 10]. In the work we report the study results of the seasonal variations of the chemically bound water (BW) spectral signature (based on the TES and OMEGA data), estimation and mapping of the winterand spring-time water ice increase within the Martian surface soil (based on the TES and HEND data). Analysis and results: Regional and global mapping of the BW spectral index distribution as function of the seasons was conducted by using of the 6.1 μm emission pick from the TES dataset and the 1.91 μm absorption band from reflectance spectra of the OMEGA data. The study of the seasonal redistribution of the water ice (and frost) within the thin surficial soil layer was conducted based on the TES thermal inertia (TI) data and the HEND neutrons flux mapping data. Bound water mapping: The mapping of the TES 6.1 μm BW index distributions was conducted at the time steps from 30° to 60° of Ls [11]. The mapping results show remarkable changes of the BW index values from one season to other one at notable latitudinal dependence of the index (Fig.1). At that, the higher BW index values are disposed mostly within the peripheral zone near the edge of the perennial and seasonal polar caps (cooler, wetter areas), while the lower BW index values are observed at low latitudes (warmer, drier areas). Between the Nspring (Ls=0°-90°) and winter (Ls=270°-360°) the zone with maximum values of BW index is shifting gradually from high latitudes to middle latitudes (20°- 30°N), being mostly disappearing in the period of Ls=150°-210°. Mapping results demonstrates that intensity of the TES 6.1 μm BW index correlates well with albedo, being higher in the brighter dusty areas and lower in the darker areas on Mars. Nevertheless, the seasonal variations of the BW index are characteristic for both bright and dark surfaces. The distinct hemispherical asymmetry of the BW index distribution is observed during the N-summer, while during the S-summer the asymmetry is much less visible. The observing time range from hydrated to dehydrated states of surface materials corresponds to the Ls range from 15° to 30° (from ~1 to 2 months). The time scale may to be conforming to the rate of the hydration/dehydration process for the Mg- and Fesulfates, composing part of the Martian soil [12, 13]. The BW index based on 1.91μm band has been mapped for spring and summer by using the OMEGA data of the first and second Martian year observations. As well in the case of the TES BW index, the mapping results of the 1.91 μm BW index also shown remarkable difference in the bound water distribution between spring and summer seasons (Fig.2). Seasonal water ice increase in the surface regolith: To define the order of the winter-time increase of the water ice within the Martian surface layer corresponding to the daily thermal skin depth (3- 10 cm in thickness) we compared the difference between the TI values mapped separately for the Nsummer- (Ls=120°-150°) and the N-winter (Ls=300°- 310°) in the latitude range ±50° out of the seasonal CO2 ice cover. We consider the summer-time and the winter-time TI values as characteristic of the dry and icy soils correspondingly. To estimate the possible water ice amount increase in the soil during winter we definition based on relationship between TI dry soil_ and TI icy soil (computed for different soil's ice content from 0% to 10%)._Following to the estimations, the zonally averaged (in 5°-latitude belts) winter-time TI values are consistent with a soil's ice content from 2-8 vol. % in the latitude ranges 30°-50°N and 40°-50°S to < 1 vol. % (and up to dry soil) at a lower latitudes 0-30° S/N. The water ice volume part was estimated for all coincided summer and winter TES TI surface footprints by solving of the quadratic equation, received at inclusion of the thermal parameters for two-component mixture (soil+ice) into formula of thermal inertia [15]. The estimated winter-time amount of water ice in the Martian soil was globally mapped and the received result is shown on Figure 3. The described method we also applied for estimation and mapping of the water ice within surficial soil in the peripheral zone of the retreating seasonal CO2 ice cap, where the polar water ice annulus (~5° circular belt) has been observed recently [16,17]. In our report we will discuss the character of the soil's water ice amount dynamics in the belt as function of the Ls and latitude. Example of the water ice amount mapping within the surficial soil in the circular belt for Ls=0-40° is shown on figure 4. As one can see from the map, the ice amount in the soil layer (with thickness 3-10cm) within the belt is varies from 3 to 11 vol. %. The seasonal variations of the water amount within thicker surface layer (up to depth 20-30 cm), we had analyzed [18] based on the HEND fast neutrons flux data (with energy range 2.5-10 Mev (FN2)) collected during two Martian years [19]. We found that distribution of the water equivalent on Mars shows notable annual differences (Fig.5). At that, the picture of the winter-time (in both hemispheres) water equivalent distribution has visible similarity with trend of the winter-time distribution of the water ice (frost) derived from the TES TI data. Conclusion: The received results of the joint analysis of the TES, HEND and OMEGA data demonstrates existence of the strong seasonal effect of the bound water and water ice amount variations in the surficial soil layer with thickness from a hundreds microns up to 20-30 cm. Appearance of the water ice in the surficial soil layer around of receding CO2 ice cap serves as direct conformation of the seasonal permafrost layer formation on Mars. Our results shown that mapped amount of the soil's water ice (involved in the seasonal redistribution) exceed notably the content of the atmospheric water. This means that the role of the regolith in the modern water cycle on Mars may to be much significant than it was suggested before. References: [1] Fanale F.P. et al., (1986), Icarus, 68, 1- 18 ; [2] Zent A.P. et al, (1995), JGR, 100, 5341-5349 ; [3] Zolotov M. Yu. (1989), LPSC XX, 1257-1258 ; [4] Mohlmann D.T.F. (2004), Icarus, 168, 318-323 ; [5] Tokano T. (2003), Icarus, 164, 50-78 ; [6] Mellon M.T. and Jakosky B.M. (1995), JGR, 100, 11781-11799 ; [7] Bottger H.M. et al., (2004), JGL, 31,L22702; [8] Smith M.D. (2004), Icarus, 167, 148-165 ; [9] Bish D.L. et al., (2003), Icarus, 164, 96- 103 ; [10] Kuzmin R.O. et al., (2007), Solar System Reseach, 41, 99-102 ; [11] Kuzmin R.O. et al., (2006), LPSC XXXVII, #1846 ; [12] Chipera S.J., Vaniman D.T. (2007), Geoch. et Cosmoch. Acta, 71, 241-250 ; [13] Chou I-M, R.R. Seal II (2007), JGR, 112, E11004, doi : 10.1029/2007JE002898 ; [14] Kuzmin R.O. et al., (2007) 7th Mars Conf., #3022; [15] Kuzmin R.O. et al., (2007), Europian Mars Science and Exploration Conference : Mars Express & ExoMars, # 1120023 ;[16] Titus, T.N. (2005), Lunar. Planet. Sci.XXXVI, Abstract #1993; [17] Wagstaff, K.L., T.N. Titus, A.B. Ivanov, R. Castano, J.L.Bandfield. (2008), Planetary and Space Science, 56, 256-265;[18] Kuzmin R.O. et al., (2007), Brown-Vernadsky Microsymp. 46th (www.planetology.ru/micro.php.); [19] Litvak M.L. et al., (2007), Solar System Reseach, 41,5, 385-397. used the nomogram [14], created for ice content

Peculiarities of the Bound Water and Water Ice Seasonal Variations in the Martian Surface Layer of the Regolith.

NASA Astrophysics Data System (ADS)

Kuzmin, R. O.; Zabalueva, E. V.; Evdokimova, N. A.; Christensen, P. H.; Mitrofanov, I. G.; Litvak, M. L.

2008-09-01

Introduction: The processes of the hydration/ dehydration of salt minerals within the Martian soil and the condensation/sublimation of water ice (and frost) in the surficial soil layer and on the polar cap surface play great significance in the modern water cycle on Mars and directly affect the redistribution of the water phases and forms in the system "atmosphere/regolith/polar caps" [1, 2, 3, 4, 5]. The processes are reversible in time and their intensity is strongly dependent on such time-variable climatic parameters as atmospheric and surface temperature, atmospheric water vapour content and specific features of atmospheric seasonal circulation [6, 7, 8, 9, 10]. In the work we report the study results of the seasonal variations of the chemically bound water (BW) spectral signature (based on the TES and OMEGA data), estimation and mapping of the winterand spring-time water ice increase within the Martian surface soil (based on the TES and HEND data). Analysis and results: Regional and global mapping of the BW spectral index distribution as function of the seasons was conducted by using of the 6.1 μm emission pick from the TES dataset and the 1.91 μm absorption band from reflectance spectra of the OMEGA data. The study of the seasonal redistribution of the water ice (and frost) within the thin surficial soil layer was conducted based on the TES thermal inertia (TI) data and the HEND neutrons flux mapping data. Bound water mapping: The mapping of the TES 6.1 μm BW index distributions was conducted at the time steps from 30° to 60° of Ls [11]. The mapping results show remarkable changes of the BW index values from one season to other one at notable latitudinal dependence of the index (Fig.1). At that, the higher BW index values are disposed mostly within the peripheral zone near the edge of the perennial and seasonal polar caps (cooler, wetter areas), while the lower BW index values are observed at low latitudes (warmer, drier areas). Between the Nspring (Ls=0°-90°) and winter (Ls=270°-360°) the zone with maximum values of BW index is shifting gradually from high latitudes to middle latitudes (20°- 30°N), being mostly disappearing in the period of Ls=150°-210°. Mapping results demonstrates that intensity of the TES 6.1 μm BW index correlates well with albedo, being higher in the brighter dusty areas and lower in the darker areas on Mars. Nevertheless, the seasonal variations of the BW index are characteristic for both bright and dark surfaces. The distinct hemispherical asymmetry of the BW index distribution is observed during the N-summer, while during the S-summer the asymmetry is much less visible. The observing time range from hydrated to dehydrated states of surface materials corresponds to the Ls range from 15° to 30° (from ~1 to 2 months). The time scale may to be conforming to the rate of the hydration/dehydration process for the Mg- and Fesulfates, composing part of the Martian soil [12, 13]. The BW index based on 1.91μm band has been mapped for spring and summer by using the OMEGA data of the first and second Martian year observations. As well in the case of the TES BW index, the mapping results of the 1.91 μm BW index also shown remarkable difference in the bound water distribution between spring and summer seasons (Fig.2). Seasonal water ice increase in the surface regolith: To define the order of the winter-time increase of the water ice within the Martian surface layer corresponding to the daily thermal skin depth (3- 10 cm in thickness) we compared the difference between the TI values mapped separately for the Nsummer- (Ls=120°-150°) and the N-winter (Ls=300°- 310°) in the latitude range ±50° out of the seasonal CO2 ice cover. We consider the summer-time and the winter-time TI values as characteristic of the dry and icy soils correspondingly. To estimate the possible water ice amount increase in the soil during winter we used the nomogram [14], created for ice content definition based on relationship between TI dry soil_ and TI icy soil (computed for different soil's ice content from 0% to 10%)._Following to the estimations, the zonally averaged (in 5°-latitude belts) winter-time TI values are consistent with a soil's ice content from 2-8 vol. % in the latitude ranges 30°-50°N and 40°-50°S to < 1 vol. % (and up to dry soil) at a lower latitudes 0-30° S/N. The water ice volume part was estimated for all coincided summer and winter TES TI surface footprints by solving of the quadratic equation, received at inclusion of the thermal parameters for two-component mixture (soil+ice) into formula of thermal inertia [15]. The estimated winter-time amount of water ice in the Martian soil was globally mapped and the received result is shown on Figure 3. The described method we also applied for estimation and mapping of the water ice within surficial soil in the peripheral zone of the retreating seasonal CO2 ice cap, where the polar water ice annulus (~5° circular belt) has been observed recently [16,17]. In our report we will discuss the character of the soil's water ice amount dynamics in the belt as function of the Ls and latitude. Example of the water ice amount mapping within the surficial soil in the circular belt for Ls=0-40° is shown on figure 4. As one can see from the map, the ice amount in the soil layer (with thickness 3-10cm) within the belt is varies from 3 to 11 vol. %. The seasonal variations of the water amount within thicker surface layer (up to depth 20-30 cm), we had analyzed [18] based on the HEND fast neutrons flux data (with energy range 2.5-10 Mev (FN2)) collected during two Martian years [19]. We found that distribution of the water equivalent on Mars shows notable annual differences (Fig.5). At that, the picture of the winter-time (in both hemispheres) water equivalent distribution has visible similarity with trend of the winter-time distribution of the water ice (frost) derived from the TES TI data. Conclusion: The received results of the joint analysis of the TES, HEND and OMEGA data demonstrates existence of the strong seasonal effect of the bound water and water ice amount variations in the surficial soil layer with thickness from a hundreds microns up to 20-30 cm. Appearance of the water ice in the surficial soil layer around of receding CO2 ice cap serves as direct conformation of the seasonal permafrost layer formation on Mars. Our results shown that mapped amount of the soil's water ice (involved in the seasonal redistribution) exceed notably the content of the atmospheric water. This means that the role of the regolith in the modern water cycle on Mars may to be much significant than it was suggested before. References: [1] Fanale F.P. et al., (1986), Icarus, 68, 1- 18 ; [2] Zent A.P. et al, (1995), JGR, 100, 5341-5349 ; [3] Zolotov M. Yu. (1989), LPSC XX, 1257-1258 ; [4] Mohlmann D.T.F. (2004), Icarus, 168, 318-323 ; [5] Tokano T. (2003), Icarus, 164, 50-78 ; [6] Mellon M.T. and Jakosky B.M. (1995), JGR, 100, 11781-11799 ; [7] Bottger H.M. et al., (2004), JGL, 31,L22702; [8] Smith M.D. (2004), Icarus, 167, 148-165 ; [9] Bish D.L. et al., (2003), Icarus, 164, 96- 103 ; [10] Kuzmin R.O. et al., (2007), Solar System Reseach, 41, 99-102 ; [11] Kuzmin R.O. et al., (2006), LPSC XXXVII, #1846 ; [12] Chipera S.J., Vaniman D.T. (2007), Geoch. et Cosmoch. Acta, 71, 241-250 ; [13] Chou I-M, R.R. Seal II (2007), JGR, 112, E11004, doi : 10.1029/2007JE002898 ; [14] Kuzmin R.O. et al., (2007) 7th Mars Conf., #3022; [15] Kuzmin R.O. et al., (2007), Europian Mars Science and Exploration Conference : Mars Express & ExoMars, # 1120023 ;[16] Titus, T.N. (2005), Lunar. Planet. Sci.XXXVI, Abstract #1993; [17] Wagstaff, K.L., T.N. Titus, A.B. Ivanov, R. Castano, J.L.Bandfield. (2008), Planetary and Space Science, 56, 256-265;[18] Kuzmin R.O. et al., (2007), Brown-Vernadsky Microsymp. 46th (www.planetology.ru/micro.php.); [19] Litvak M.L. et al., (2007), Solar System Reseach, 41,5, 385-397.

Distinct characteristics of the intermediate water observed off the east coast of Korea during two contrasting years

NASA Astrophysics Data System (ADS)

Nam, S.; Yoon, S.; Park, J. H.; Kim, Y. H.; Chang, K. I.

2016-02-01

The intermediate water known as `East Sea Intermediate Water' and its coastal mode `North Korea Cold Water' found south of the Subpolar Front (SF) is formed in the northern East (Japan) Sea, and its physical properties are known to be determined by wintertime air-sea interaction north of the SF. Hydrographic data collected off the coast bi-monthly from 1994 to 2011 show significant decadal oscillations in spiciness following isopycnals of intermediate water (27.1-27.2 sigma-theta typically corresponding to 150 m depth), which are explained by the Arctic Oscillation (AO) and consequent cold-air outbreaks. During positive AO phases over the decades, the cold-air outbreak and water formation are more active and the intermediate water having the same spiciness reaches higher density (higher spiciness following the same isopycnals). At interannual timescale, however, the spiciness variability is well beyond the relationship with the AO. Especially, significantly lower spiciness (or both less saline and lower temperature) intermediate water was observed in spring of 2010 than 2001 under the similar AO condition (negative peaks). Strong cooling with common negative peaks in surface net-heat flux (with different patterns) and common negative peaks in the AO index are prominent in winter of the two years over past two decades. Such contrasting characteristics of intermediate water between 2001 and 2010 are consistent with the HYCOM reanalysis results which, along with the satellite altimetry-derived sea surface height maps, indicates widespread extension of low (high) spiciness intermediate water in the southwestern East Sea in 2010 (2001). A clear contrast in circulation pattern, along with net-heat flux pattern, is suggested to derive the observational results in the distinctly different characteristics of the intermediate water.

Synoptic climatological analysis of persistent cold air pools over the Carpathian Basin

NASA Astrophysics Data System (ADS)

Szabóné André, Karolina; Bartholy, Judit; Pongrácz, Rita

2016-04-01

A persistent cold air pool (PCAP) is a winter-time, anticyclone-related weather event over a relatively large basin. During this time the air is colder near the surface than aloft. This inversion near the surface can last even for weeks. As the cold air cools down, relative humidity increases and fog forms. The entire life cycle of a PCAP depends on the large scale circulation pattern. PCAP usually appears when an anticyclone builds up after a cold front passed over the examined basin, and it is usually destructed by a coming strong cold front of another midlatitude cyclone. Moreover, the intensity of the anticyclone affects the intensity of the PCAP. PCAP may result in different hazards for the population: (1) Temperature inversion in the surface layers together with weak wind may lead to severe air pollution causing health problems for many people, especially, elderly and children. (2) The fog and/or smog during chilly weather conditions often results in freezing rain. Both fog and freezing rain can distract transportation and electricity supply. Unfortunately, the numerical weather prediction models have difficulties to predict PCAP formation and destruction. One of the reasons is that PCAP is not defined objectively with a simple formula, which could be easily applied to the numerical output data. However, according to some recommendations from the synoptic literature, the shallow convective potential energy (SCPE) can be used to mathematically describe PCAP. In this study, we used the ERA-Interim reanalysis datasets to examine this very specific weather event (i.e., PCAP) over the Carpathian Basin. The connection between the mean sea level pressure and some PCAP measures (e.g., SCPE, energy deficit, etc.) is evaluated. For instance, we used logistic regression to identify PCAP periods over the Carpathian Basin. Then, further statistical analysis includes the evaluation of the length and intensity of these PCAP periods.

Isolating the atmospheric circulation response to Arctic sea-ice loss in the coupled climate system

NASA Astrophysics Data System (ADS)

Kushner, P. J.; Blackport, R.

2016-12-01

In the coupled climate system, projected global warming drives extensive sea-ice loss, but sea-ice loss drives warming that amplifies and can be confounded with the global warming process. This makes it challenging to cleanly attribute the atmospheric circulation response to sea-ice loss within coupled earth-system model (ESM) simulations of greenhouse warming. In this study, many centuries of output from coupled ocean/atmosphere/land/sea-ice ESM simulations driven separately by sea-ice albedo reduction and by projected greenhouse-dominated radiative forcing are combined to cleanly isolate the hemispheric scale response of the circulation to sea-ice loss. To isolate the sea-ice loss signal, a pattern scaling approach is proposed in which the local multidecadal mean atmospheric response is assumed to be separately proportional to the total sea-ice loss and to the total low latitude ocean surface warming. The proposed approach estimates the response to Arctic sea-ice loss with low latitude ocean temperatures fixed and vice versa. The sea-ice response includes a high northern latitude easterly zonal wind response, an equatorward shift of the eddy driven jet, a weakening of the stratospheric polar vortex, an anticyclonic sea level pressure anomaly over coastal Eurasia, a cyclonic sea level pressure anomaly over the North Pacific, and increased wintertime precipitation over the west coast of North America. Many of these responses are opposed by the response to low-latitude surface warming with sea ice fixed. However, both sea-ice loss and low latitude surface warming act in concert to reduce storm track strength throughout the mid and high latitudes. The responses are similar in two related versions of the National Center for Atmospheric Research earth system models, apart from the stratospheric polar vortex response. Evidence is presented that internal variability can easily contaminate the estimates if not enough independent climate states are used to construct them.

Future Climate Impacts of Direct Radiative Forcing Anthropogenic Aerosols, Tropospheric Ozone, and Long-lived Greenhouse Gases

NASA Technical Reports Server (NTRS)

Chen, Wei-Ting; Liao, Hong; Seinfeld, John H.

2007-01-01

Long-lived greenhouse gases (GHGs) are the most important driver of climate change over the next century. Aerosols and tropospheric ozone (O3) are expected to induce significant perturbations to the GHG-forced climate. To distinguish the equilibrium climate responses to changes in direct radiative forcing of anthropogenic aerosols, tropospheric ozone, and GHG between present day and year 2100, four 80-year equilibrium climates are simulated using a unified tropospheric chemistry-aerosol model within the Goddard Institute for Space Studies (GISS) general circulation model (GCM) 110. Concentrations of sulfate, nitrate, primary organic (POA) carbon, secondary organic (SOA) carbon, black carbon (BC) aerosols, and tropospheric ozone for present day and year 2100 are obtained a priori by coupled chemistry-aerosol GCM simulations, with emissions of aerosols, ozone, and precursors based on the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenario (SRES) A2. Changing anthropogenic aerosols, tropospheric ozone, and GHG from present day to year 2100 is predicted to perturb the global annual mean radiative forcing by +0.18 (considering aerosol direct effects only), +0.65, and +6.54 W m(sup -2) at the tropopause, and to induce an equilibrium global annual mean surface temperature change of +0.14, +0.32, and +5.31 K, respectively, with the largest temperature response occurring at northern high latitudes. Anthropogenic aerosols, through their direct effect, are predicted to alter the Hadley circulation owing to an increasing interhemispheric temperature gradient, leading to changes in tropical precipitation. When changes in both aerosols and tropospheric ozone are considered, the predicted patterns of change in global circulation and the hydrological cycle are similar to those induced by aerosols alone. GHG-induced climate changes, such as amplified warming over high latitudes, weakened Hadley circulation, and increasing precipitation over the Tropics and high latitudes, are consistent with predictions of a number of previous GCM studies. Finally, direct radiative forcing of anthropogenic aerosols is predicted to induce strong regional cooling over East and South Asia. Wintertime rainfall over southeastern China and the Indian subcontinent is predicted to decrease because of the increased atmospheric stability and decreased surface evaporation, while the geographic distribution of precipitation is also predicted to be altered as a result of aerosol-induced changes in wind flow.

The effect of aerosols on northern hemisphere wintertime stationary waves

NASA Astrophysics Data System (ADS)

Lewinschal, Anna; Ekman, Annica M. L.

2010-05-01

Aerosol particles have a considerable impact on the energy budget of the atmosphere because of their ability to scatter and absorb incoming solar radiation. Since the beginning of the industrialisation a large increase has been seen mainly in the concentrations of sulphate and black carbon as a result of combustion of fossil fuel and biomass burning. Aerosol particles have a relatively short residence time in the atmosphere why the aerosol concentration shows a large variation spatially as well as in time where high concentrations are found close to emission sources. This leads to a highly varying radiative forcing pattern which modifies temperature gradients which in turn can alter the pressure distribution and lead to changes in the circulation in the atmosphere. In this study, the effect on the wintertime planetary scale waves on the northern hemisphere is specifically considered together with the regional climate impact due to changes in the stationary waves. To investigate the effect of aerosols on the circulation a global general circulation model based on the ECMWF operational forecast model is used (EC-Earth). The aerosol description in EC-Earth consists of prescribed monthly mean mass concentration fields of five different types of aerosols: sulphate, black carbon, organic carbon, dust and sea salt. Only the direct radiative effect is considered and the different aerosol types are treated as external mixtures. Changes in the stationary wave pattern are determined by comparing model simulations using present-day and pre-industrial concentrations of aerosol particles. Since the planetary scale waves largely influence the storm tracks and are an important part of the meridional heat transport, changes in the wave pattern may have substantial impact on the climate globally and locally. By looking at changes in the model simulations globally it can be found that the aerosol radiative forcing has the potential to change the stationary wave pattern. Furthermore, it shows that regional changes in the climate occur also where the radiative forcing from aerosol particles is not particularly strong, which would indicate that the large scale dynamical response to aerosol forcing can induce changes in temperature, precipitation and wind patterns outside the region where the forcing is initially located.

Combining ground-based microwave radiometer and the AROME convective scale model through 1DVAR retrievals in complex terrain: an Alpine valley case study

NASA Astrophysics Data System (ADS)

Martinet, Pauline; Cimini, Domenico; De Angelis, Francesco; Canut, Guylaine; Unger, Vinciane; Guillot, Remi; Tzanos, Diane; Paci, Alexandre

2017-09-01

A RPG-HATPRO ground-based microwave radiometer (MWR) was operated in a deep Alpine valley during the Passy-2015 field campaign. This experiment aims to investigate how stable boundary layers during wintertime conditions drive the accumulation of pollutants. In order to understand the atmospheric processes in the valley, MWRs continuously provide vertical profiles of temperature and humidity at a high time frequency, providing valuable information to follow the evolution of the boundary layer. A one-dimensional variational (1DVAR) retrieval technique has been implemented during the field campaign to optimally combine an MWR and 1 h forecasts from the French convective scale model AROME. Retrievals were compared to radiosonde data launched at least every 3 h during two intensive observation periods (IOPs). An analysis of the AROME forecast errors during the IOPs has shown a large underestimation of the surface cooling during the strongest stable episode. MWR brightness temperatures were monitored against simulations from the radiative transfer model ARTS2 (Atmospheric Radiative Transfer Simulator) and radiosonde launched during the field campaign. Large errors were observed for most transparent channels (i.e., 51-52 GHz) affected by absorption model and calibration uncertainties while a good agreement was found for opaque channels (i.e., 54-58 GHz). Based on this monitoring, a bias correction of raw brightness temperature measurements was applied before the 1DVAR retrievals. 1DVAR retrievals were found to significantly improve the AROME forecasts up to 3 km but mainly below 1 km and to outperform usual statistical regressions above 1 km. With the present implementation, a root-mean-square error (RMSE) of 1 K through all the atmospheric profile was obtained with values within 0.5 K below 500 m in clear-sky conditions. The use of lower elevation angles (up to 5°) in the MWR scanning and the bias correction were found to improve the retrievals below 1000 m. MWR retrievals were found to catch deep near-surface temperature inversions very well. Larger errors were observed in cloudy conditions due to the difficulty of ground-based MWRs to resolve high level inversions that are still challenging. Finally, 1DVAR retrievals were optimized for the analysis of the IOPs by using radiosondes as backgrounds in the 1DVAR algorithm instead of the AROME forecasts. A significant improvement of the retrievals in cloudy conditions and below 1000 m in clear-sky conditions was observed. From this study, we can conclude that MWRs are expected to bring valuable information into numerical weather prediction models up to 3 km in altitude both in clear-sky and cloudy-sky conditions with the maximum improvement found around 500 m. With an accuracy between 0.5 and 1 K in RMSE, our study has also proven that MWRs are capable of resolving deep near-surface temperature inversions observed in complex terrain during highly stable boundary layer conditions.

Absolute Humidity and the Seasonality of Influenza (Invited)

NASA Astrophysics Data System (ADS)

Shaman, J. L.; Pitzer, V.; Viboud, C.; Grenfell, B.; Goldstein, E.; Lipsitch, M.

2010-12-01

Much of the observed wintertime increase of mortality in temperate regions is attributed to seasonal influenza. A recent re-analysis of laboratory experiments indicates that absolute humidity strongly modulates the airborne survival and transmission of the influenza virus. Here we show that the onset of increased wintertime influenza-related mortality in the United States is associated with anomalously low absolute humidity levels during the prior weeks. We then use an epidemiological model, in which observed absolute humidity conditions temper influenza transmission rates, to successfully simulate the seasonal cycle of observed influenza-related mortality. The model results indicate that direct modulation of influenza transmissibility by absolute humidity alone is sufficient to produce this observed seasonality. These findings provide epidemiological support for the hypothesis that absolute humidity drives seasonal variations of influenza transmission in temperate regions. In addition, we show that variations of the basic and effective reproductive numbers for influenza, caused by seasonal changes in absolute humidity, are consistent with the general timing of pandemic influenza outbreaks observed for 2009 A/H1N1 in temperate regions. Indeed, absolute humidity conditions correctly identify the region of the United States vulnerable to a third, wintertime wave of pandemic influenza. These findings suggest that the timing of pandemic influenza outbreaks is controlled by a combination of absolute humidity conditions, levels of susceptibility and changes in population mixing and contact rates.

Analysis of Surface Albedo to Improve Upper-Ocean Heat Budget Calculations

NASA Astrophysics Data System (ADS)

Hogikyan, A.; Zhang, D.; Cronin, M. F.

2016-12-01

Over 90% of the Earth's energy imbalance is stored in the oceans, so it is important to understand the ocean-atmosphere heat transfer. The Ocean Climate Stations group (OCS) at the Pacific Marine Environmental Laboratory maintains two moored surface buoys in the North Pacific (PAPA and KEO) as air-sea flux reference sites. The goal of the reference sites is to validate global air-sea flux products from atmospheric reanalyses and satellite products, that are critical to understand and model the variability and trend of the earth climate. As other air-sea flux reference buoys in the world ocean, PAPA and KEO only measure downward shortwave radiation (SWdown), but utilize the albedo and the directly measured SWdown to calculate the SWup. Since the open ocean albedo is small, the errors associated with this practice are thought to be comparable or smaller than the instrumentation errors in the air-sea flux measurements. In addition, it is generally accepted that ocean surface albedos can be derived with reasonable confidence from surface radiative fluxes in satellite products such as the Clouds and the Earth's Radiant Energy System (CERES) and the International Satellite Cloud Climatology Project (ISCCP). This project developed a CERES-based albedo product for derivation of SWnet at PAPA and KEO, and assessed the impact of CERES-based albedo on the net surface heat fluxes relative to the currently used ISCCP-based albedo in the OCS air-sea flux data (http://www.pmel.noaa.gov/ocs/data/fluxdisdel/). The high-resolution surface fluxes from CERES are more frequently updated, and consider more physical factors in the approximation, than those from ISCCP. There was a greater change between ISCCP and CERES albedo during wintertime than during summer. There was a greater change at Station PAPA in the northeastern sub-Arctic Pacific, than at Station KEO in the northwestern subtropical Pacific. The rate of temperature change of the mixed-layer is shown to increase based on the new source of albedo data, .08 and .5 °C/year at KEO and PAPA, respectively. The differences in the net surface heat flux due to different albedos used in this study suggest that more comprehensive investigations of the albedo in different products and radiative models, and their impacts on oceanic and atmospheric processes are needed.

The Importance of Ammonia for Winter Haze Formation in Two Oil and Gas Production Regions

NASA Astrophysics Data System (ADS)

Collett, J. L., Jr.; Li, Y.; Evanoski-Cole, A. R.; Sullivan, A.; Day, D.; Archuleta, C.; Tigges, M.; Sewell, H. J.; Prenni, A. J.; Schichtel, B. A.

2014-12-01

Fine particle ammonium nitrate formation results from the atmospheric reaction of gaseous ammonia and nitric acid. This reaction is most important in winter when low temperatures thermodynamically enhance particle formation. Nitrogen oxides emissions from oil and gas operations partially react in the atmosphere to form nitric acid. The availability of atmospheric ammonia plays an important role in determining whether the nitric acid formed results in wintertime ammonium nitrate formation. Here we contrast situations in two important U.S. oil and gas production regions. Measurements of ammonia, nitric acid, ammonium nitrate and other species were made from 2007 to present near Boulder, Wyoming and in winters 2013 and 2014 in western North Dakota. The Boulder, Wyoming site is close to the large Jonah and Pinedale Anticline gas fields. Field sites at the north unit of Theodore Roosevelt National Park and Fort Union are situated in the large Bakken Formation oil and gas production region. Wintertime formation of nitric acid and ammonium nitrate, together comprising nitrogen in the +5 oxidation state (N(V)), was observed in both locations. Concentrations of N(V), however, are generally much lower at Boulder, WY than in the Bakken. An even bigger difference is seen in fine particle ammonium nitrate concentrations; limited regional ammonia is available in western Wyoming to react with nitric acid, leaving a portion of the nitric acid trapped in the gas phase. Higher concentrations of ammonia are observed in the Bakken where they support formation of much higher concentrations of ammonium nitrate. Comparison of these two regions clearly indicates the importance of understanding both local NOx emissions and regional concentrations of ammonia in predicting source impacts on formation of fine particles and haze.

The analysis of polar clouds from AVHRR satellite data using pattern recognition techniques

NASA Technical Reports Server (NTRS)

Smith, William L.; Ebert, Elizabeth

1990-01-01

The cloud cover in a set of summertime and wintertime AVHRR data from the Arctic and Antarctic regions was analyzed using a pattern recognition algorithm. The data were collected by the NOAA-7 satellite on 6 to 13 Jan. and 1 to 7 Jul. 1984 between 60 deg and 90 deg north and south latitude in 5 spectral channels, at the Global Area Coverage (GAC) resolution of approximately 4 km. This data embodied a Polar Cloud Pilot Data Set which was analyzed by a number of research groups as part of a polar cloud algorithm intercomparison study. This study was intended to determine whether the additional information contained in the AVHRR channels (beyond the standard visible and infrared bands on geostationary satellites) could be effectively utilized in cloud algorithms to resolve some of the cloud detection problems caused by low visible and thermal contrasts in the polar regions. The analysis described makes use of a pattern recognition algorithm which estimates the surface and cloud classification, cloud fraction, and surface and cloudy visible (channel 1) albedo and infrared (channel 4) brightness temperatures on a 2.5 x 2.5 deg latitude-longitude grid. In each grid box several spectral and textural features were computed from the calibrated pixel values in the multispectral imagery, then used to classify the region into one of eighteen surface and/or cloud types using the maximum likelihood decision rule. A slightly different version of the algorithm was used for each season and hemisphere because of differences in categories and because of the lack of visible imagery during winter. The classification of the scene is used to specify the optimal AVHRR channel for separating clear and cloudy pixels using a hybrid histogram-spatial coherence method. This method estimates values for cloud fraction, clear and cloudy albedos and brightness temperatures in each grid box. The choice of a class-dependent AVHRR channel allows for better separation of clear and cloudy pixels than does a global choice of a visible and/or infrared threshold. The classification also prevents erroneous estimates of large fractional cloudiness in areas of cloudfree snow and sea ice. The hybrid histogram-spatial coherence technique and the advantages of first classifying a scene in the polar regions are detailed. The complete Polar Cloud Pilot Data Set was analyzed and the results are presented and discussed.

CO2 emissions from permafrost regions in Alaska during the nongrowing seasons

NASA Astrophysics Data System (ADS)

Natali, S.; Risk, D. A.; Minions, C.; Ludwig, S.; Watts, J. D.; Rogers, B. M.; Goetz, S. J.; Jastrow, J. D.; Jorgenson, T.; Schade, J. D.

2017-12-01

Surface air temperatures in the Arctic have been increasing twice as fast as the global average, and climate models project that this rate of warming will continue through the century, with the greatest warming occurring during the winter months. An increase in wintertime temperature may reduce belowground carbon storage due to enhanced microbial respiration during the snow-covered period when plant carbon uptake has predominantly ceased. Carbon emissions during the nongrowing season (NGS: i.e., autumn, winter and spring) are an important component of annual respiratory loss, yet there are large uncertainties in local and regional estimates of NGS CO2 fluxes. To address these uncertainties, we established a network of automated soil respiration sensors that run throughout the year at 10 locations across AK, including several paired burned and unburned sites in tundra and boreal regions. We measured soil CO2 flux, soil temperature (15, 50, 100 cm), soil moisture, and snow depth throughout the NGS, and plant cover, stand density, organic layer depth and thaw depth, and we analyzed active layer soils for total C and N, and organic matter composition. During spring thaw, all sites exhibited a strong pulse of CO2, a result of physical release of CO2 produced during the NGS. CO2 flux rates during the spring thaw were 1-2 orders of magnitude higher than winter CO2 fluxes and twice as high as fluxes during the early growing season. While temperature was a key driver of NGS fluxes across sites, our results suggest that soil organic matter content and composition were also important for NGS CO2 production. Despite warmer soils in burned spruce forests (Nome Creek, 2004 burn and Hess Creek, 2003 burn; 1-2 C warmer at 50-100 cm) compared to mature forests, NGS fluxes were either not significantly different or were higher in the mature stands than in burned stands, which may be a result of substrate limitation to NGS fluxes following fire. Quantifying the magnitude and drivers of NGS CO2 flux is critical for determining whether the Arctic is currently a source or sink for carbon and how this is likely to change as warming continues.

Quantifying Ozone Production throughout the Boundary Layer from High Frequency Tethered Profile Measurements during a High Ozone Episode in the Uinta Basin, Utah

NASA Astrophysics Data System (ADS)

Sterling, C. W.; Johnson, B.; Schnell, R. C.; Oltmans, S. J.; Cullis, P.; Hall, E. G.; Jordan, A. F.; Windell, J.; McClure-Begley, A.; Helmig, D.; Petron, G.

2015-12-01

During the Uinta Basin Winter Ozone Study (UBWOS) in Jan - Feb 2013, 735 tethered ozonesonde profiles were obtained at 3 sites including during high wintertime photochemical ozone production events that regularly exceeded 125 ppb. High resolution profiles of ozone and temperature with altitude, measured during daylight hours, showed the development of approximately week long high ozone episodes building from background levels of ~40 ppb to >150 ppb. The topography of the basin combined with a strong temperature inversion trapped oil and gas production effluents in the basin and the snow covered surface amplified the sun's radiation driving the photochemical ozone production at rates up to 13 ppb/hour in a cold layer capped at 1600-1700 meters above sea level. Beginning in mid-morning, ozone mixing ratios throughout the cold layer increased until late afternoon. Ozone mixing ratios were generally constant with height indicating that ozone production was nearly uniform throughout the depth of the cold pool. Although there was strong diurnal variation, ozone mixing ratios increased during the day more than decreased during the night, resulting in elevated levels the next morning; an indication that nighttime loss processes did not compensate for daytime production. Even though the 3 tethersonde sites were at elevations differing by as much as 140 m, the top of the high ozone layer was nearly uniform in altitude at the 3 locations. Mobile van surface ozone measurements across the basin confirmed this capped structure of the ozone layer; the vehicle drove out of high ozone mixing ratios at an elevation of ~1900 meters above sea level, above which free tropospheric ozone mixing ratios of ~50 ppb were measured. Exhaust plumes from a coal-fired power plant in the eastern portion of the basin were intercepted by the tethersondes. The structure of the profiles clearly showed that effluents in the plumes were not mixed downward and thus did not contribute precursor nitrogen oxides to the observed ozone production in the boundary layer.

Coupling of the spatial-temporal distributions of nutrients and physical conditions in the southern Yellow Sea

NASA Astrophysics Data System (ADS)

Wei, Qin-Sheng; Yu, Zhi-Gang; Wang, Bao-Dong; Fu, Ming-Zhu; Xia, Chang-Shui; Liu, Lu; Ge, Ren-Feng; Wang, Hui-Wu; Zhan, Run

2016-04-01

This study investigated the coupling of the spatial-temporal variations in nutrient distributions and physical conditions in the southern Yellow Sea (SYS) using data compiled from annual-cycle surveys conducted in 2006-2007 as well as satellite-derived sea-surface temperature (SST) images. The influence of physical dynamics on the distribution and transport of nutrients varied spatially and seasonally in the SYS. The Changjiang Diluted Water (CDW) plume (in summertime), the Subei Coastal Water (SCW) (year-round), and the Lubei Coastal Current (LCC) (in wintertime) served as important sources of nutrients in the inshore area in a dynamic environment. The saline Taiwan Warm Current (TWC) might transport nutrients to the northeast region of the Changjiang Estuary in the summer, and this nutrient source began to increase from spring to summer and decrease when autumn arrived. Three types of nutrient fronts, i.e., estuarine, offshore, and coastal, were identified. A circular nutrient front caused by cross-shelf transport of SCW in the southeast shelf bank area in the winter and spring was observed. The southeastward flow of western coastal cold water in the SYS might be an important conduit for cross-shelf nutrient exchange between the SYS and the East China Sea (ECS). The tongue-shaped low-nutrient region in the western study area in the wintertime was driven by the interaction of the southward Yellow Sea Western Coastal Current (YSWCC) and the biological activity. The vertically variable SCM (subsurface Chl-a maximum) in the central SYS was controlled by coupled physical-chemical processes that involved stratification and associated nutricline. The average nutrient fluxes into the euphotic zone due to upwelling near the frontal zone of the Yellow Sea Cold Water Mass (YSCWM) in the summer are estimated here for the first time: 1.4 ± 0.9 × 103 μmol/m2/d, 0.1 ± 0.1 × 103 μmol/m2/d, and 2.0 ± 1.3 × 103 μmol/m2/d for DIN, PO4-P, and SiO3-Si, respectively. The depletion of nutrients in the central SYS and the upwelled transport in the boundary of the YSCWM resulted in a spatial transfer of the high Chl-a zone, varying generally from the central SYS to the boundary of the YSCWM from spring to summer, and the nutrient flux associated with this upwelling could contribute significantly to local primary production. This study deepens our understanding of the mechanisms influencing the distribution and transport of nutrients in the SYS.

Satellite Sees a Midwest White Out

NASA Image and Video Library

2017-12-08

The GOES-East satellite captured a Midwestern wintertime "White Out" at 2015 UTC/3:15 p.m. EST on January 6, 2014. Blowing snow and intensely cold air created dangerous white-out conditions over the Midwest, particularly around the Great Lakes, where daytime temperatures averaged -20F with a wind chill near -50F. The GOES-East satellite is managed by NOAA. The image was created at NASA's GOES Project at NASA's Goddard Space Flight Center, Greenbelt, Md. Credit: NASA NOAA GOES Project, Dennis Chesters NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Long-term Changes in Extreme Air Pollution Meteorology and the Implications for Air Quality.

PubMed

Hou, Pei; Wu, Shiliang

2016-03-31

Extreme air pollution meteorological events, such as heat waves, temperature inversions and atmospheric stagnation episodes, can significantly affect air quality. Based on observational data, we have analyzed the long-term evolution of extreme air pollution meteorology on the global scale and their potential impacts on air quality, especially the high pollution episodes. We have identified significant increasing trends for the occurrences of extreme air pollution meteorological events in the past six decades, especially over the continental regions. Statistical analysis combining air quality data and meteorological data further indicates strong sensitivities of air quality (including both average air pollutant concentrations and high pollution episodes) to extreme meteorological events. For example, we find that in the United States the probability of severe ozone pollution when there are heat waves could be up to seven times of the average probability during summertime, while temperature inversions in wintertime could enhance the probability of severe particulate matter pollution by more than a factor of two. We have also identified significant seasonal and spatial variations in the sensitivity of air quality to extreme air pollution meteorology.

Chemical characteristics of N2O5 observed at a rural site in Beijing winter 2016: from clean to polluted air mass

NASA Astrophysics Data System (ADS)

Wang, H.; Lu, K.; Tan, Z.; Chen, X.; Wu, Z.; Zhu, Q.; Li, X.; Liu, Y.; Shang, D.; Wu, Y.; Min, H.; Zeng, L.; Schmitt, S. H.; Rohrer, F.; Kiendler-Scharr, A.; Wahner, A.; Zhang, Y.

2017-12-01

Dinitrogen pentoxide (N2O5) plays a vital role in the atmospheric oxidation, the NOX removal and the nitrate formation. A comprehensive campaign was conducted in the wintertime of 2016 in Beijing to focus on the atmospheric oxidation, new particle formation and aerosol light extinctions during the wintertime in Beijing. The site is located at a rural area in the northeast of Beijing and about 60 km away from the city center. A newly developed instrument based on the cavity enhanced absorption spectroscopy (CEAS) was deployed to measure ambient N2O5. Simultaneous measurements of the properties of particles and the relevant trace gases are available. The daily peaks of N2O5 in the clean episodes was lower than that of polluted episodes, the campaign maximum of 1.4 ppbv were captured in the most serious pollution episode. The averaged N2O5 maximum was about 120 pptv near 20:00, which is higher than that observed in summer. The uptake coefficient of N2O5 was derived from an iterative box model approach based on the Regional Atmospheric Chemical Mechanism version 2 (RACM2), constrained to observed trace gas compounds as well as the aerosol surface concentrations. The mechanisms of the chemical compounds of aerosols (measured by AMS) affects the N2O5 uptake coefficient are explored in several chemical coordinate systems. The chemical behaviors of the ambient N2O5 concentrations for this campaign is further discussed in the context of other campaigns performed in the urban and suburban areas in Beijing.

Opposing Seasonal Trends in Seawater pH and Aragonite Saturation State on the Bermuda Coral Reef Platform Reveal Complex Controls on Seawater Chemistry by Biological and Physical Processes

NASA Astrophysics Data System (ADS)

Andersson, A. J.; Bates, N. R.; dePutron, S.; Collins, A.; Neely, K.; Best, M.; Noyes, T.

2011-12-01

To accurately predict future consequences of ocean acidification on coastal environments and ecosystems, it is critical to understand present conditions and variability. As part of the Bermuda ocean acidification and coral reef investigation (BEACON), significant efforts have been dedicated to characterize the complete surface seawater carbonic-acid system at different temporal and spatial scales on the Bermuda coral reef platform to understand current levels and variability in seawater CO2 parameters, reef metabolism, and future potential changes arising from ocean acidification. A four years monthly time-series of seawater carbonic-acid parameters at eight different locations on the Bermuda coral reef platform reveals strong seasonal patterns in dissolved inorganic carbon (DIC), total alkalinity (TA), pH, pCO2, and [HCO3-], and somewhat weaker trends in [CO32-] and saturation state with respect to CaCO3 minerals. Strong spatial gradients are also observed in DIC and TA during summertime owing to reef metabolism, but no or weak spatial gradients of these parameters are observed in the wintertime. Interestingly, maximum pH-sws (~8.15) is observed during wintertime when minimum aragonite saturation state (<3.0) is observed. In contrast, minimum pH-sws (~7.95) is observed in the summertime when maximum aragonite saturation state (>3.70) is observed. The observed trends and gradients point to complex relationships and interactions between seawater chemistry, biology and physics that need to be considered in the context of ocean acidification and in making future predictions on the effects of this perturbation on coral reefs and coastal ecosystems.

On the effectiveness of nitrogen oxide reductions as a control over ammonium nitrate aerosol

NASA Astrophysics Data System (ADS)

Pusede, S. E.; Duffey, K. C.; Shusterman, A. A.; Saleh, A.; Laughner, J. L.; Wooldridge, P. J.; Zhang, Q.; Parworth, C. L.; Kim, H.; Capps, S. L.; Valin, L. C.; Cappa, C. D.; Fried, A.; Walega, J.; Nowak, J. B.; Hoff, R. M.; Berkoff, T. A.; Beyersdorf, A. J.; Olson, J.; Crawford, J. H.; Cohen, R. C.

2015-10-01

Nitrogen oxides (NOx) have fallen steadily across the US over the last fifteen years. At the same time, due to patterns diesel truck activities, NOx concentrations decrease on weekends relative to weekdays, largely without co-occurring changes in other gas-phase emissions. These trends taken together provide two independent constraints on the role of NOx in the nonlinear chemistry of atmospheric oxidation. In this context, we interpret interannual trends in wintertime ammonium nitrate (NH4NO3) in the San Joaquin Valley of California, a location with the worst aerosol pollution in the US and where a large portion of aerosol mass is NH4NO3. Here, we show that NOx reductions have simultaneously decreased nighttime and increased daytime NH4NO3 production over the last decade. We find a substantial decrease in NH4NO3 since 2000 and conclude that this decrease is due to reduced nitrate radical-initiated production at night in residual layers that are decoupled from fresh emissions at the surface. Further reductions in NOx are imminent in California, and nationwide, and we make a quantitative prediction of the response of NH4NO3. We show that the combination of rapid chemical production and efficient NH4NO3 loss via deposition of gas-phase nitric acid implies high aerosol days in cities in the San Joaquin Valley air basin are responsive to local changes in NOx within those individual cities. Our calculations indicate that large decreases in NOx in the future will not only lower wintertime NH4NO3 concentrations, they will also cause a transition in the dominant NH4NO3 source from nighttime to daytime chemistry.

On the effectiveness of nitrogen oxide reductions as a control over ammonium nitrate aerosol

NASA Astrophysics Data System (ADS)

Pusede, S. E.; Duffey, K. C.; Shusterman, A. A.; Saleh, A.; Laughner, J. L.; Wooldridge, P. J.; Zhang, Q.; Parworth, C. L.; Kim, H.; Capps, S. L.; Valin, L. C.; Cappa, C. D.; Fried, A.; Walega, J.; Nowak, J. B.; Weinheimer, A. J.; Hoff, R. M.; Berkoff, T. A.; Beyersdorf, A. J.; Olson, J.; Crawford, J. H.; Cohen, R. C.

2016-03-01

Nitrogen oxides (NOx) have fallen steadily across the US over the last 15 years. At the same time, NOx concentrations decrease on weekends relative to weekdays, largely without co-occurring changes in other gas-phase emissions, due to patterns of diesel truck activities. These trends taken together provide two independent constraints on the role of NOx in the nonlinear chemistry of atmospheric oxidation. In this context, we interpret interannual trends in wintertime ammonium nitrate (NH4NO3) in the San Joaquin Valley of California, a location with the worst aerosol pollution in the US and where a large portion of aerosol mass is NH4NO3. Here, we show that NOx reductions have simultaneously decreased nighttime and increased daytime NH4NO3 production over the last decade. We find a substantial decrease in NH4NO3 since 2000 and conclude that this decrease is due to reduced nitrate radical-initiated production at night in residual layers that are decoupled from fresh emissions at the surface. Further reductions in NOx are imminent in California, and nationwide, and we make a quantitative prediction of the response of NH4NO3. We show that the combination of rapid chemical production and efficient NH4NO3 loss via deposition of gas-phase nitric acid implies that high aerosol days in cities in the San Joaquin Valley air basin are responsive to local changes in NOx within those individual cities. Our calculations indicate that large decreases in NOx in the future will not only lower wintertime NH4NO3 concentrations but also cause a transition in the dominant NH4NO3 source from nighttime to daytime chemistry.

Influence of projected snow and sea-ice changes on future climate in heavy snowfall region

NASA Astrophysics Data System (ADS)

Matsumura, S.; Sato, T.

2011-12-01

Snow/ice albedo and cloud feedbacks are critical for climate change projection in cryosphere regions. However, future snow and sea-ice distributions are significantly different in each GCM. Thus, surface albedo in cryosphere regions is one of the causes of the uncertainty for climate change projection. Northern Japan is one of the heaviest snowfall regions in the world. In particular, Hokkaido is bounded on the north by the Okhotsk Sea, where is the southernmost ocean in the Northern Hemisphere that is covered with sea ice during winter. Wintertime climate around Hokkaido is highly sensitive to fluctuations in snow and sea-ice. The purpose of this study is to evaluate the influence of global warming on future climate around Hokkaido, using the Pseudo-Global-Warming method (PGW) by a regional climate model. The boundary conditions of the PGW run were obtained by adding the difference between the future (2090s) and past (1990s) climates simulated by coupled general circulation model (MIROC3.2 medres), which is from the CMIP3 multi-model dataset, into the 6-hourly NCEP reanalysis (R-2) and daily OISST data in the past climate (CTL) run. The PGW experiments show that snow depth significantly decreases over mountainous areas and snow cover mainly decreases over plain areas, contributing to higher surface warming due to the decreased snow albedo. Despite the snow reductions, precipitation mainly increases over the mountainous areas because of enhanced water vapor content. However, precipitation decreases over the Japan Sea and the coastal areas, indicating the weakening of a convergent cloud band, which is formed by convergence between cold northwesteries from the Eurasian continent and anticyclonic circulation over the Okhotsk Sea. These results suggest that Okhotsk sea-ice decline may change the atmospheric circulation and the resulting effect on cloud formation, resulting in changes in winter snow or precipitation. We will also examine another CMIP3 model (MRI-CGCM2.3.2), which sensitivity of surface albedo to surface air temperature is the lowest in the CMIP3 models.

Nitrous acid formation in a snow-free wintertime polluted rural area

NASA Astrophysics Data System (ADS)

Tsai, Catalina; Spolaor, Max; Fedele Colosimo, Santo; Pikelnaya, Olga; Cheung, Ross; Williams, Eric; Gilman, Jessica B.; Lerner, Brian M.; Zamora, Robert J.; Warneke, Carsten; Roberts, James M.; Ahmadov, Ravan; de Gouw, Joost; Bates, Timothy; Quinn, Patricia K.; Stutz, Jochen

2018-02-01

Nitrous acid (HONO) photolysis is an important source of hydroxyl radicals (OH) in the lower atmosphere, in particular in winter when other OH sources are less efficient. The nighttime formation of HONO and its photolysis in the early morning have long been recognized as an important contributor to the OH budget in polluted environments. Over the past few decades it has become clear that the formation of HONO during the day is an even larger contributor to the OH budget and additionally provides a pathway to recycle NOx. Despite the recognition of this unidentified HONO daytime source, the precise chemical mechanism remains elusive. A number of mechanisms have been proposed, including gas-phase, aerosol, and ground surface processes, to explain the elevated levels of daytime HONO. To identify the likely HONO formation mechanisms in a wintertime polluted rural environment we present LP-DOAS observations of HONO, NO2, and O3 on three absorption paths that cover altitude intervals from 2 to 31, 45, and 68 m above ground level (a.g.l.) during the UBWOS 2012 experiment in the Uintah Basin, Utah, USA. Daytime HONO mixing ratios in the 2-31 m height interval were, on average, 78 ppt, which is lower than HONO levels measured in most polluted urban environments with similar NO2 mixing ratios of 1-2 ppb. HONO surface fluxes at 19 m a.g.l., calculated using the HONO gradients from the LP-DOAS and measured eddy diffusivity coefficient, show clear upward fluxes. The hourly average vertical HONO flux during sunny days followed solar irradiance, with a maximum of (4.9 ± 0.2) × 1010 molec. cm-2 s-1 at noontime. A photostationary state analysis of the HONO budget shows that the surface flux closes the HONO budget, accounting for 63 ± 32 % of the unidentified HONO daytime source throughout the day and 90 ± 30 % near noontime. This is also supported by 1-D chemistry and transport model calculations that include the measured surface flux, thus clearly identifying chemistry at the ground as the missing daytime HONO source in this environment. Comparison between HONO surface flux, solar radiation, NO2 and HNO3 mixing ratios, and results from 1-D model runs suggest that, under high NOx conditions, HONO formation mechanisms related to solar radiation and NO2 mixing ratios, such as photo-enhanced conversion of NO2 on the ground, are most likely the source of daytime HONO. Under moderate to low NO2 conditions, photolysis of HNO3 on the ground seems to be the main source of HONO.

Lidar Observations of the Vertical Structure of Ozone and Aerosol during Wintertime High-Ozone Episodes Associated with Oil and Gas Exploration in the Uintah Basin

NASA Astrophysics Data System (ADS)

Senff, C. J.; Langford, A. O.; Banta, R. M.; Alvarez, R. J.; Weickmann, A.; Sandberg, S.; Marchbanks, R. D.; Brewer, A.; Hardesty, R. M.

2013-12-01

The Uintah Basin in northeast Utah has been experiencing extended periods of poor air quality in the winter months including very high levels of surface ozone. To investigate the causes of these wintertime ozone pollution episodes, two comprehensive studies were undertaken in January/February of 2012 and 2013. As part of these Uintah Basin Ozone Studies (UBOS), NOAA deployed its ground-based, scanning Tunable Optical Profiler for Aerosol and oZone (TOPAZ) lidar to document the vertical structure of ozone and aerosol backscatter from near the surface up to about 3 km above ground level (AGL). TOPAZ, along with a comprehensive set of chemistry and meteorological measurements, was situated in both years at the Horse Pool site at the northern edge of a large concentration of gas producing wells in the eastern part of the Uintah Basin. The 2012 study was characterized by unusually warm and snow-free condition and the TOPAZ lidar observed deep boundary layers (BL) and mostly well-mixed vertical ozone profiles at or slightly above tropospheric background levels. During UBOS 2013, winter weather conditions in the Uintah Basin were more typical with snow-covered ground and a persistent, shallow cold-pool layer. The TOPAZ lidar characterized with great temporal and spatial detail the evolution of multiple high-ozone episodes as well as cleanout events caused by the passage of synoptic-scale storm systems. Despite the snow cover, the TOPAZ observations show well-mixed afternoon ozone and aerosol profiles up to about 100 m AGL. After several days of pollutant buildup, BL ozone values reached 120-150 ppbv. Above the mixed layer, ozone values gradually decreased to tropospheric background values of around 50 ppbv throughout the several-hundred-meter-deep cold-pool layer and then stayed constant above that up to about 3 km AGL. During the ozone episodes, the lidar observations show no indication of either vertical or horizontal transport of high ozone levels to the surface, thus supporting the notion that ozone is locally produced in the Uintah Basin. In both winters, TOPAZ occasionally observed ozone titration as the NOx-rich plume from the nearby Bonanza power plant was advected over the Horse Pool site. In 2012, low ozone values due to titration were observed at the surface and throughout the well-mixed BL, while in 2013 low ozone values were confined to the upper part of the cold-pool layer above the BL. This suggests that power plant NOx was very likely not part of the precursor mix that led to the high surface ozone values observed in 2013.

Challenges in Understanding and Predicting Greenland Lake Drainage Events

NASA Astrophysics Data System (ADS)

Poinar, K.; Andrews, L. C.; Moon, T. A.; Nowicki, S.

2017-12-01

To accurately predict ice flow, an ice-sheet model must resolve the complex spatio-temporal variability of the ice-sheet hydrologic system. For Greenland, this requires understanding rapid lake drainage events, by which moulins deliver water from supraglacial lakes to the ice-sheet base. Critical metrics include the drainage event location and its timing during the melt season. Here, we use multiple remote sensing datasets to investigate whether local principal strain rates control the dates of rapid supraglacial lake drainage events. We identify 359 rapid lake drainage events through a semi-automated analysis of MODIS and Landsat imagery, which we apply to Pâkitsoq, western Greenland, over nine summers (2006-2010 and 2013-2016). We compare these drainage dates to principal strain rates derived from InSAR (MEaSUREs and other products) and Landsat (GoLIVE and other products) satellite data over the same years. The InSAR-derived strain rates have lower uncertainties ( 0.01 yr-1) but capture only a wintertime average; the Landsat-derived strain rates have larger uncertainties ( 0.1 yr-1) but feature higher temporal resolution (≥16 days) and span the entire year, including the melt season. We find that locations with more-tensile wintertime strain rates are associated with earlier draining of supraglacial lakes in the subsequent summer. This is consistent with observations of lake drainage "clusters" or "cascades", where the perturbation from an initial lake drainage event is thought to trigger other lake drainages in the area. Our relation is not statistically significant, however, and any causality is complicated by a stronger correlation with more traditional metrics such as surface elevation and cumulative melt days. We also find that the Landsat-derived summertime strain rates, despite their higher temporal resolution, do not resolve the transient extensional strain rates known from GPS observations to accompany and/or incite rapid lake drainages. Our results highlight the current challenges in observing, at the regional scale, the causes of rapid lake drainage events, which must be better understood in order to parameterize surface-to-bed hydrological connections in ice-sheet models.

Intercomparison and validation of the mixed layer depth fields of global ocean syntheses

NASA Astrophysics Data System (ADS)

Toyoda, Takahiro; Fujii, Yosuke; Kuragano, Tsurane; Kamachi, Masafumi; Ishikawa, Yoichi; Masuda, Shuhei; Sato, Kanako; Awaji, Toshiyuki; Hernandez, Fabrice; Ferry, Nicolas; Guinehut, Stéphanie; Martin, Matthew J.; Peterson, K. Andrew; Good, Simon A.; Valdivieso, Maria; Haines, Keith; Storto, Andrea; Masina, Simona; Köhl, Armin; Zuo, Hao; Balmaseda, Magdalena; Yin, Yonghong; Shi, Li; Alves, Oscar; Smith, Gregory; Chang, You-Soon; Vernieres, Guillaume; Wang, Xiaochun; Forget, Gael; Heimbach, Patrick; Wang, Ou; Fukumori, Ichiro; Lee, Tong

2017-08-01

Intercomparison and evaluation of the global ocean surface mixed layer depth (MLD) fields estimated from a suite of major ocean syntheses are conducted. Compared with the reference MLDs calculated from individual profiles, MLDs calculated from monthly mean and gridded profiles show negative biases of 10-20 m in early spring related to the re-stratification process of relatively deep mixed layers. Vertical resolution of profiles also influences the MLD estimation. MLDs are underestimated by approximately 5-7 (14-16) m with the vertical resolution of 25 (50) m when the criterion of potential density exceeding the 10-m value by 0.03 kg m-3 is used for the MLD estimation. Using the larger criterion (0.125 kg m-3) generally reduces the underestimations. In addition, positive biases greater than 100 m are found in wintertime subpolar regions when MLD criteria based on temperature are used. Biases of the reanalyses are due to both model errors and errors related to differences between the assimilation methods. The result shows that these errors are partially cancelled out through the ensemble averaging. Moreover, the bias in the ensemble mean field of the reanalyses is smaller than in the observation-only analyses. This is largely attributed to comparably higher resolutions of the reanalyses. The robust reproduction of both the seasonal cycle and interannual variability by the ensemble mean of the reanalyses indicates a great potential of the ensemble mean MLD field for investigating and monitoring upper ocean processes.

Heat and salt budgets over the Gulf Stream North Wall during LatMix survey in winter 2012.

NASA Astrophysics Data System (ADS)

Sanchez-Rios, A.; Shearman, R. K.; D'Asaro, E. A.; Lee, C.; Gula, J.; Klymak, J. M.

2016-02-01

As part of the ONR-sponsored LatMix Experiment, ship-based and glider-based observations following a Lagrangian float are used to examine the evolution of temperature, salinity and density along the Gulf Stream north wall in wintertime. Satellite observations during the survey and the in-situ measurements showed the presence of submesoscale (<10 km) features along the front. Models have successfully reproduced similar features, but observations are lacking, particularly at the small scales needed to understand their role in the transport of heat and salt across the front and out of the mixed layer. Calculating the trend in time at each depth and cross-front location we found an increase of heat and salinity in regions where the strongest cross-front gradients of velocity were observed at the mixed layer and around 150m depth, these changes are density compensated and suggest isopycnal mixing and a connection between the mixed layer and subsurface layers. The large Rossby number (Ro>1) calculated for this regions corroborates the possibility of submesoscale dynamics. Using a heat and salinity budget, we show that surface forcing, entrainment from below and advection by the mean flow velocities are not sufficient to explain the observed rate of change of heat and salinity in the mixed layer. Although confidence estimates prevent an accurate flux divergence calculation, Reynold flux estimates are consistent with a cross-frontal exchange that can reproduce the observed temporal trends.

Low-temperature tolerance and cold hardening of cacti

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

Nobel, P.S.

Reduced uptake by the chlorenchyma cells of cacti of a stain (neutral red) was used as an indicator of low-temperature damage resulting from cooling stems in the laboratory. Necrosis set in a few degrees below the temperature at which the fraction of cells accumulating stain was reduced by 50%. Coryphantha vivipara, Opuntia polyacantha, and Pediocactus simpsonii, which range to over 300 m altitude in southern Wyoming, were quite cold tolerant. Relationships among tissue cold sensitivity, morphological features which protect the stems from low temperatures, and the occurrence of species in progressively colder regions were investigated. Differences in tissue cold sensitivitymore » accounted for the approx. = 600 m higher elevational limit of Coryphantha vivipara var. rosea compared to the morphologically similar var. deserti in southern Nevada. In contrast, morphological differences alone could adequately explain the relative northern limits of the columnar cacti Carnegiea gigantea vs Stenocereus gummosus and the barrel cacti Ferocactus acanthodes vs. F. wislizenii in the southwestern United States, as previously indicated using a computer model. Cold hardening in response to decreasing day/night air temperatures was observed for 10 species. A decrease from 50/sup 0//40/sup 0/ to 10/sup 0//0/sup 0/ lowered by 4/sup 0/ the temperature at which the fraction of the chlorenchyma cells taking up stain was reduced 50% for both D. rhodacantha and T. candicans, with a half-time for the shift of approx. = 3 d. The tolerance of subzero temperatures and the ability to cold harden allow cacti to range into regions with considerable wintertime freezing.« less

Increases in wintertime PM2.5 sodium and chloride linked to snowfall and road salt application

NASA Astrophysics Data System (ADS)

Kolesar, Katheryn R.; Mattson, Claire N.; Peterson, Peter K.; May, Nathaniel W.; Prendergast, Rashad K.; Pratt, Kerri A.

2018-03-01

The application of salts and salty brines to roads is common practice during the winter in many urban environments. Road salts can become aerosolized, thereby injecting sodium and chloride particulate matter (PM) into the atmosphere. Here, data from the United States Environmental Protection Agency Chemical Speciation Monitoring Network were used to assess temporal trends of sodium and chloride PM2.5 (PM < 2.5 μm) at 25 locations across the United States to investigate the ubiquity of road salt aerosols. Sodium and chloride PM2.5 concentrations were an average of three times higher in the winter, as compared to the summer, for locations with greater than 25 cm of average annual snowfall. Winter urban chloride PM2.5 concentrations attributed to road salt can even sometimes rival those of coastal sea spray aerosol-influenced sites. In most snow-influenced cities, chloride and sodium PM2.5 concentrations were positively correlated with snowfall; however, this relationship is complicated by differences in state and local winter maintenance practices. This study highlights the ubiquity of road salt aerosols in the United States and their potential impact on wintertime urban air quality, particularly due to the potential for multiphase reactions to liberate chlorine from the particle-phase. Since road salt application is a common practice in wintertime urban environments across the world, it is imperative that road salt application emissions, currently not included in inventories, and its impacts be investigated through measurements and modeling.

Contributions of wood smoke and vehicle emissions to ambient concentrations of volatile organic compounds and particulate matter during the Yakima wintertime nitrate study

NASA Astrophysics Data System (ADS)

VanderSchelden, Graham; de Foy, Benjamin; Herring, Courtney; Kaspari, Susan; VanReken, Tim; Jobson, Bertram

2017-02-01

A multiple linear regression (MLR) chemical mass balance model was applied to data collected during an air quality field experiment in Yakima, WA, during January 2013 to determine the relative contribution of residential wood combustion (RWC) and vehicle emissions to ambient pollutant levels. Acetonitrile was used as a chemical tracer for wood burning and nitrogen oxides (NOx) as a chemical tracer for mobile sources. RWC was found to be a substantial source of gas phase air toxics in wintertime. The MLR model found RWC primarily responsible for emissions of formaldehyde (73%), acetaldehyde (69%), and black carbon (55%) and mobile sources primarily responsible for emissions of carbon monoxide (CO; 83%), toluene (81%), C2-alkylbenzenes (81%), and benzene (64%). When compared with the Environmental Protection Agency's 2011 winter emission inventory, the MLR results suggest that the contribution of RWC to CO emissions was underestimated in the inventory by a factor of 2. Emission ratios to NOx from the MLR model agreed to within 25% with wintertime emission ratios predicted from the Motor Vehicle Emissions Simulator (MOVES) 2010b emission model for Yakima County for all pollutants modeled except for CO, C2-alkylbenzenes, and black carbon. The MLR model results suggest that MOVES was overpredicting mobile source emissions of CO relative to NOx by a factor of 1.33 and black carbon relative to NOx by about a factor of 3.

Observations of fine particulate nitrated phenols in four sites in northern China: concentrations, source apportionment, and secondary formation

NASA Astrophysics Data System (ADS)

Wang, Liwei; Wang, Xinfeng; Gu, Rongrong; Wang, Hao; Yao, Lan; Wen, Liang; Zhu, Fanping; Wang, Weihao; Xue, Likun; Yang, Lingxiao; Lu, Keding; Chen, Jianmin; Wang, Tao; Zhang, Yuanghang; Wang, Wenxing

2018-03-01

Filter samples of fine particulate matters were collected at four sites in northern China (urban, rural, and mountain) in summer and winter, and the contents of nine nitrated phenols were quantified in the laboratory with the use of ultra-high-performance liquid chromatography coupled with mass spectrometry. During the sampling periods, the concentrations of particulate nitrated phenols exhibited distinct temporal and spatial variation. On average, the total concentration of particulate nitrated phenols in urban Jinan in the wintertime reached 48.4 ng m-3, and those in the summertime were 9.8, 5.7, 5.9, and 2.5 ng m-3 in urban Jinan, rural Yucheng and Wangdu, and Mt. Tai, respectively. The elevated concentrations of nitrated phenols in wintertime and in urban areas demonstrate the apparent influences of anthropogenic sources. The positive matrix factorization receptor model was then applied to determine the origins of particulate nitrated phenols in northern China. The five major source factors were traffic, coal combustion, biomass burning, secondary formation, and aged coal combustion plume. Among them, coal combustion played a vital role, especially at the urban site in the wintertime, with a contribution of around 55 %. In the summertime, the observed nitrated phenols were highly influenced by aged coal combustion plumes at all of the sampling sites. Meanwhile, in remote areas, contributions from secondary formation were significant. Further correlation analysis indicates that nitrosalicylic acids were produced mostly from secondary formation that was dominated by NO2 nitration.

Upper and Lower Limits of the Rate of SO2 Oxidation In Wintertime Atmosphere Over The Eastern United States

NASA Astrophysics Data System (ADS)

Green, J. R.; Fiddler, M. N.; Brown, S. S.; Bililign, S.; Jaegle, L.; Thornton, J. A.; Shah, V.; Lopez-Hilfiker, F.; Haskins, J.; Fibiger, D. L.; McDuffie, E. E.; Sparks, T.; Ebben, C. J.; Wooldridge, P. J.; Veres, P. R.; Weinheimer, A. J.; Dibb, J. E.; Schroder, J. C.; Campuzano-Jost, P.; Day, D.; Jimenez, J. L.; Sullivan, A.; DiGangi, J. P.

2017-12-01

A set of constraints on the rate of oxidation of SO2 during wintertime conditions over the Eastern United States is presented, based on measurements taken during a series of night and day flights on a C-130 aircraft from Feb 3 to Mar 13, 2015 over the Eastern coastal region of the United States during the Wintertime INvestigation of Transport, Emission and Reactivity (WINTER) campaign. In the Eastern United States, there are fewer reactant sinks for gaseous SO2 during the winter, and as a result the atmospheric lifetime is measurably longer. Photochemical oxidation of SO2 is extremely slow during winter due to significantly reduced OH concentrations compared to summer. The long photochemical lifetime enables analysis of rates of proposed alternative sulfur oxidation mechanisms, such as heterogeneous uptake. An examination of the SO4/SO2 ratio and the mixing ratio will be used to determine the upper and lower limits of the rate of SO2 oxidation, along with the branching ratios of the gas-phase and heterogeneous removal. A correlation of SO2 to the co-emitted compounds measured in the region will allow for the accurate assignment of intercepted plumes to individual power plants and urban areas. A combination of HYSPLIT trajectory modeling, use of several chemical clocks, and analysis of the wind speed along the path of the plume is used to constrain the travel time from the source to the intercepted plume.

Twentieth century warming of the tropical Atlantic captured by Sr-U paleothermometry

NASA Astrophysics Data System (ADS)

Alpert, Alice E.; Cohen, Anne L.; Oppo, Delia W.; DeCarlo, Thomas M.; Gaetani, Glenn A.; Hernandez-Delgado, Edwin A.; Winter, Amos; Gonneea, Meagan E.

2017-02-01

Coral skeletons are valuable archives of past ocean conditions. However, interpretation of coral paleotemperature records is confounded by uncertainties associated with single-element ratio thermometers, including Sr/Ca. A new approach, Sr-U, uses U/Ca to constrain the influence of Rayleigh fractionation on Sr/Ca. Here we build on the initial Pacific Porites Sr-U calibration to include multiple Atlantic and Pacific coral genera from multiple coral reef locations spanning a temperature range of 23.15-30.12°C. Accounting for the wintertime growth cessation of one Bermuda coral, we show that Sr-U is strongly correlated with the average water temperature at each location (r2 = 0.91, P < 0.001, n = 19). We applied the multispecies spatial calibration between Sr-U and temperature to reconstruct a 96 year long temperature record at Mona Island, Puerto Rico, using a coral not included in the calibration. Average Sr-U derived temperature for the period 1900-1996 is within 0.12°C of the average instrumental temperature at this site and captures the twentieth century warming trend of 0.06°C per decade. Sr-U also captures the timing of multiyear variability but with higher amplitude than implied by the instrumental data. Mean Sr-U temperatures and patterns of multiyear variability were replicated in a second coral in the same grid box. Conversely, Sr/Ca records from the same two corals were inconsistent with each other and failed to capture absolute sea temperatures, timing of multiyear variability, or the twentieth century warming trend. Our results suggest that coral Sr-U paleothermometry is a promising new tool for reconstruction of past ocean temperatures.

Twentieth century warming of the tropical Atlantic captured by Sr-U paleothermometry

USGS Publications Warehouse

Alpert, Alice E.; Cohen, Anne L.; Oppo, Delia W.; DeCarlo, Thomas M.; Gaetani, Glenn A.; Hernandez-Delgado, Edwin A.; Winter, Amos; Gonneea, Meagan

2017-01-01

Coral skeletons are valuable archives of past ocean conditions. However, interpretation of coral paleotemperature records is confounded by uncertainties associated with single-element ratio thermometers, including Sr/Ca. A new approach, Sr-U, uses U/Ca to constrain the influence of Rayleigh fractionation on Sr/Ca. Here we build on the initial Pacific Porites Sr-U calibration to include multiple Atlantic and Pacific coral genera from multiple coral reef locations spanning a temperature range of 23.15–30.12°C. Accounting for the wintertime growth cessation of one Bermuda coral, we show that Sr-U is strongly correlated with the average water temperature at each location (r2 = 0.91, P < 0.001, n = 19). We applied the multispecies spatial calibration between Sr-U and temperature to reconstruct a 96 year long temperature record at Mona Island, Puerto Rico, using a coral not included in the calibration. Average Sr-U derived temperature for the period 1900–1996 is within 0.12°C of the average instrumental temperature at this site and captures the twentieth century warming trend of 0.06°C per decade. Sr-U also captures the timing of multiyear variability but with higher amplitude than implied by the instrumental data. Mean Sr-U temperatures and patterns of multiyear variability were replicated in a second coral in the same grid box. Conversely, Sr/Ca records from the same two corals were inconsistent with each other and failed to capture absolute sea temperatures, timing of multiyear variability, or the twentieth century warming trend. Our results suggest that coral Sr-U paleothermometry is a promising new tool for reconstruction of past ocean temperatures.

The role of the Asian winter monsoon in the rapid propagation of abrupt climate changes during the last deglaciation

NASA Astrophysics Data System (ADS)

Chu, Guoqiang; Sun, Qing; Zhu, Qingzeng; Shan, Yabing; Shang, Wenyu; Ling, Yuan; Su, Youliang; Xie, Manman; Wang, Xishen; Liu, Jiaqi

2017-12-01

High-resolution temperature records spanning the last deglaciation from low latitudes are scarce; however, they are important for understanding the rapid propagation of abrupt climate events throughout the Northern Hemisphere and the tropics. Here, we present a branched GDGTs-based temperature reconstruction from the sediments of Maar Lake Huguangyan in tropical China. The record reveals that the mean temperature during the Oldest Dryas was 17.8 °C, which was followed by a two-step increase of 2-3 °C to the Bølling-Allerød, a decrease to 19.8 °C during the Younger Dryas, and a rapid warming at the onset of the Holocene. The Oldest Dryas was about 2 °C warmer than the Younger Dryas. The reconstructed temperature was weighted towards the wintertime since the lake is monomictic and the mixing process in winter supplies nutrients from the lake bottom to the entire water column, greatly promoting biological productivity. In addition, the winter-biased temperature changes observed in the study are more distinctive than the summer-biased temperature records from extra-tropical regions of East Asia. This implies that the temperature decreases during abrupt climatic events were mainly a winter phenomenon. Within the limits of the dating uncertainties, the broadly similar pattern of winter-weighted temperature change observed in both tropical Lake Huguangyan and in Greenland ice cores indicates the occurrence of tightly-coupled interactions between high latitude ice sheets and land areas in the tropics. We suggest that the winter monsoon (especially cold surges) could play an important role in the rapid transmission of the temperature signal from the Arctic to the tropics.

The impacts of intense moisture transport on the deep and marginal sea-ice zones of the Arctic during winter

NASA Astrophysics Data System (ADS)

Woods, Cian; Caballero, Rodrigo

2015-04-01

Over the past few decades observations have shown that the Arctic is warming at a much faster rate than the global average; a phenomenon know as polar amplification. This tendency for the high latitudes to warm at a disproportionate rate compared to the global average is also a robust feature of global climate model simulations and highlights the importance of climate research in this region. The most often cited mechanism explaining polar amplification is the ice-albedo feed-back; a mechanism by which the surface albedo decreases as sea ice retreats in response to a warming climate. This in turn leads to a higher absorption of insolation and the melting of more ice. In recent years the role of the ice-albedo feedback mechanism as the main cause of polar amplification has been brought into question. GCM studies show a slight reduction of the total poleward energy transport in a warming climate; with the dry static component decreasing at a much faster rate than the moist component. This repartitioning of the poleward energy transport has implications for the formation of clouds in the Arctic, which induce a secondary warming by trapping escaping OLR. These cloud processes in the atmosphere can explain at least part of the recent temperature amplification in the Arctic; and indeed even aquaplanet model studies with zero sea-ice reproduce the polar amplification phenomenon. Directionally, the ice-albedo feedback is a "bottom-up" process; inducing warming in the atmosphere from an increasing surface heat source i.e. more open ocean. The opening of more ocean surface is also consistent with the bottom amplified structure of warming in the Arctic. Here we present evidence for a mechanism in the atmosphere that matches with observations, but in fact acts the opposite direction i.e. "top-down", whereby moist air masses from lower latitudes, termed "moisture intrusions", travelling over the sea-ice increase the longwave down radiation and in turn induce a bottom amplified warming at the surface. There are an average of 14 such events that enter the polar cap each winter, driving about 50% of the seasonal variation in surface temperature over the deep Arctic. We show that, over the last 30 years, the marginal ice-zones in the Barents, Labrador and Chukchi Seas have experienced roughly a doubling in the frequency of these intense moisture intrusion events during winter. Interestingly, these are the regions that have experienced the most rapid wintertime ice loss in the Arctic, raising the question: to what extent has the recent Arctic warming been driven by local vs. interannual/remote processes?

A Multi-Year Aerosol Characterization for the Greater Tehran Area Using Satellite, Surface, and Modeling Data

PubMed Central

Crosbie, Ewan; Sorooshian, Armin; Monfared, Negar Abolhassani; Shingler, Taylor; Esmaili, Omid

2014-01-01

This study reports a multi-year (2000–2009) aerosol characterization for metropolitan Tehran and surrounding areas using multiple datasets (Moderate Resolution Imaging Spectroradiometer (MODIS), Multi-angle Imaging Spectroradiometer (MISR), Total Ozone Mapping Spectrometer (TOMS), Goddard Ozone Chemistry Aerosol Radiation and Transport (GOCART), and surface and upper air data from local stations). Monthly trends in aerosol characteristics are examined in the context of the local meteorology, regional and local emission sources, and air mass back-trajectory data. Dust strongly affects the region during the late spring and summer months (May–August) when aerosol optical depth (AOD) is at its peak and precipitation accumulation is at a minimum. In addition, the peak AOD that occurs in July is further enhanced by a substantial number of seasonal wildfires in upwind regions. Conversely, AOD is at a minimum during winter; however, reduced mixing heights and a stagnant lower atmosphere trap local aerosol emissions near the surface and lead to significant reductions in visibility within Tehran. The unique meteorology and topographic setting makes wintertime visibility and surface aerosol concentrations particularly sensitive to local anthropogenic sources and is evident in the noteworthy improvement in visibility observed on weekends. Scavenging of aerosol due to precipitation is evident during the winter when aconsistent increase in surface visibility and concurrent decrease in AOD is observed in the days after rain compared with the days immediately before rain. PMID:25083295

Potential sea salt aerosol sources from frost flowers in the pan-Arctic region

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

Xu, Li; Russell, Lynn M.; Burrows, Susannah M.

In order to better represent observed wintertime aerosol concentrations at Barrow, Alaska, we implemented an observationally-based parameterization for estimating sea salt production from frost flowers in the Community Earth System Model (CESM). In this work, we evaluate the potential influence of this sea salt source on the pan-Arctic (60ºN-90ºN) climate. Results show that frost flower salt emissions substantially increase the modeled surface sea salt aerosol concentration in the winter months when new sea ice and frost flowers are present. The parameterization reproduces both the magnitude and seasonal variation of the observed submicron sea salt aerosol concentration at surface in Barrowmore » during winter much better than the standard CESM simulation without a frost-flower salt particle source. Adding these frost flower salt particle emissions increases aerosol optical depth by 10% and results in a small cooling at surface. The increase in salt particle mass concentrations of a factor of 8 provides nearly two times the cloud condensation nuclei concentration, as well as 10% increases in cloud droplet number and 40% increases in liquid water content near coastal regions adjacent to continents. These cloud changes reduce longwave cloud forcing by 3% and cause a small surface warming, increasing the downward longwave flux at the surface by 2 W m-2 in the pan-Arctic under the present-day climate.« less

Lidar measurements at Lauder, NZ

NASA Technical Reports Server (NTRS)

McGee, Thomas J.; Gross, Michael; Singh, Upendra; Kimvilakani, Patrick

1995-01-01

In March of 1994, the GSFC Stratospheric Ozone Lidar was deployed to the Network for the Detection of Stratospheric Change (NDSC) site at Lauder, NZ. This was in conjunction with a series of NASA ER-2 flights from Christchurch, NZ south to the Antarctic Circle. These flights were organized to study the chemistry of the stratosphere before, during and after the formation of the well-known 'ozone hole'. Lidar measurements were made at four different time periods corresponding to the times of the ER-2 flights. Lauder is situated nearly along the flight path as the aircraft flew south and so the lidar measurements provide a checkpoint for the ozone, aerosol and temperature instruments onboard the aircraft. Whenever the weather permitted, lidar measurements were made as near to dawn, prior to the flight, and as near to sunset, after the flight. This provided data as close to the aircraft transit time as possible. More than 70 individual lidar measurements were made, each consisting of a vertical profile of ozone, temperature, and aerosol. These were made over three different seasons and show seasonal variation. Of particular interest in the lidar data base is the wintertime stratospheric - mesospheric temperature profiles, which show large variations at the stratopause and also some significant wave activity.

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.

India: Bihar

Atmospheric Science Data Center

2013-04-16

... an immense wintertime pool of pollution over the northern Indian state of Bihar. The discovery was made by researchers analyzing four ... Urbana-Champaign . MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Science Mission ...

Decadal and annual changes in biogenic opal and carbonate fluxes to the deep Sargasso Sea

USGS Publications Warehouse

Deuser, W.G.; Jickells, T.D.; Commeau, Judith A.

1995-01-01

Analyses of samples from a 14-year series of sediment-trap deployments in the deep Sargasso Sea reveal a significant trend in the ratio of the sinking fluxes of biogenic calcium carbonate and silica. Although there are pronounced seasonal cycles for both flux components, the overall opal/CaCO3 ratio changed by 50% from 1978 to 1991 (largely due to a decrease of opal flux), while total flux had no significant trend. These results suggest that plankton communities respond rapidly to subtle climate change, such as is evident in regional variations of wind speed, precipitation, wintertime ventilation and midwater temperatures. If the trends we observe in the makeup of sinking particulate matter occur on a large scale, they may in turn modify climate by modulating ocean-atmosphere CO2 exchange and albedo over the ocean.

A twenty-first century California observing network for monitoring extreme weather events

USGS Publications Warehouse

White, A.B.; Anderson, M.L.; Dettinger, M.D.; Ralph, F.M.; Hinojosa, A.; Cayan, D.R.; Hartman, R.K.; Reynolds, D.W.; Johnson, L.E.; Schneider, T.L.; Cifelli, R.; Toth, Z.; Gutman, S.I.; King, C.W.; Gehrke, F.; Johnston, P.E.; Walls, C.; Mann, Dorte; Gottas, D.J.; Coleman, T.

2013-01-01

During Northern Hemisphere winters, the West Coast of North America is battered by extratropical storms. The impact of these storms is of paramount concern to California, where aging water supply and flood protection infrastructures are challenged by increased standards for urban flood protection, an unusually variable weather regime, and projections of climate change. Additionally, there are inherent conflicts between releasing water to provide flood protection and storing water to meet requirements for water supply, water quality, hydropower generation, water temperature and flow for at-risk species, and recreation. In order to improve reservoir management and meet the increasing demands on water, improved forecasts of precipitation, especially during extreme events, is required. Here we describe how California is addressing their most important and costliest environmental issue – water management – in part, by installing a state-of-the-art observing system to better track the area’s most severe wintertime storms.

Winter monsoon variability and its impact on aerosol concentrations in East Asia.

PubMed

Jeong, Jaein I; Park, Rokjin J

2017-02-01

We investigate the relationship between winter aerosol concentrations over East Asia and variability in the East Asian winter monsoon (EAWM) using GEOS-Chem 3-D global chemical transport model simulations and ground-based aerosol concentration data. We find that both observed and modeled surface aerosol concentrations have strong relationships with the intensity of the EAWM over northern (30-50°N, 100-140°E) and southern (20-30°N, 100-140°E) East Asia. In strong winter monsoon years, compared to weak winter monsoon years, lower and higher surface PM 2.5 concentrations by up to 25% are shown over northern and southern East Asia, respectively. Analysis of the simulated results indicates that the southward transport of aerosols is a key process controlling changes in aerosol concentrations over East Asia associated with the EAWM. Variability in the EAWM is found to play a major role in interannual variations in aerosol concentrations; consequently, changes in the EAWM will be important for understanding future changes in wintertime air quality over East Asia. Copyright © 2016 Elsevier Ltd. All rights reserved.

Antifreeze Admixtures for Concrete

DOT National Transportation Integrated Search

1997-10-01

The goal of this project was to develop a chemical admixture that would reduce the need for wintertime thermal protection of freshly placed concrete. Chemicals were investigated for their ability to promote strength gain in concrete cured below 0 deg...

Linking deep convection and phytoplankton blooms in the northern Labrador Sea in a changing climate

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

Balaguru, Karthik; Doney, Scott C.; Bianucci, Laura

Wintertime convective mixing plays a pivotal role in the sub-polar North Atlantic spring phytoplankton blooms by favoring phytoplankton survival in the competition between light-dependent production and losses due to grazing and gravitational settling. We use satellite and ocean reanalyses to show that the area-averaged maximum winter mixed layer depth is positively correlated with April chlorophyll concentration in the northern Labrador Sea. A simple theoretical framework is developed to understand the relative roles of winter/spring convection and gravitational sedimentation in spring blooms in this region. Combining climate model simulations that project a weakening of wintertime Labrador Sea convection from Arctic seamore » ice melt with our framework suggests a potentially significant reduction in the initial fall phytoplankton population that survive the winter to seed the region's spring bloom by the end of the 21st century.« less

Season-ahead water quality forecasts for the Schuylkill River, Pennsylvania

NASA Astrophysics Data System (ADS)

Block, P. J.; Leung, K.

2013-12-01

Anticipating and preparing for elevated water quality parameter levels in critical water sources, using weather forecasts, is not uncommon. In this study, we explore the feasibility of extending this prediction scale to a season-ahead for the Schuylkill River in Philadelphia, utilizing both statistical and dynamical prediction models, to characterize the season. This advance information has relevance for recreational activities, ecosystem health, and water treatment, as the Schuylkill provides 40% of Philadelphia's water supply. The statistical model associates large-scale climate drivers with streamflow and water quality parameter levels; numerous variables from NOAA's CFSv2 model are evaluated for the dynamical approach. A multi-model combination is also assessed. Results indicate moderately skillful prediction of average summertime total coliform and wintertime turbidity, using season-ahead oceanic and atmospheric variables, predominantly from the North Atlantic Ocean. Models predicting the number of elevated turbidity events across the wintertime season are also explored.

Budget of the OH reactivity in the North China Plain in summer- and wintertime: Results from recent field campaigns

NASA Astrophysics Data System (ADS)

Fuchs, H.; Tan, Z.; Lu, K.; Bohn, B.; Borchardt, J.; Broch, S.; Brown, S. S.; Dong, H.; Gkatzelis, G.; Gomm, S.; Häseler, R.; He, L. Y.; Hohaus, T.; Hofzumahaus, A.; Holland, F.; Kiendler-Scharr, A.; Li, X.; Liu, Y.; Lu, S.; Min, K. E.; Novelli, A.; Rohrer, F.; Shao, M.; Wang, B.; Wang, M.; Wu, Y.; Zeng, L.; Zhang, Y.; Wegener, R.; Wahner, A.; Zhang, Y.

2016-12-01

Two comprehensive field campaigns were conducted in the densely populated North China Plain in summer 2014 and winter 2016. In 2014, the measurement site was located in a botanic garden close to the smaller town of Wangdu without major industry, but influenced by regional transportation of air pollution. In 2016, measurements were done close to Beijing and this site was partly impacted by wintertime pollution events. The loss rate coefficient of atmospheric hydroxyl radicals (OH) was quantified by direct measurements of the OH reactivity. Concurrent measurements of OH reactants allow for the determination of calculated OH reactivity. The comparison between measured and calculated OH reactivity can be used to quantify the fraction of missing OH reactivity. Closure of OH reactivity in these campaigns for different seasons will be investigated and compared with results from previous campaigns in China.

Linking deep convection and phytoplankton blooms in the northern Labrador Sea in a changing climate

PubMed Central

Doney, Scott C.; Bianucci, Laura; Rasch, Philip J.; Leung, L. Ruby; Yoon, Jin-Ho; Lima, Ivan D.

2018-01-01

Wintertime convective mixing plays a pivotal role in the sub-polar North Atlantic spring phytoplankton blooms by favoring phytoplankton survival in the competition between light-dependent production and losses due to grazing and gravitational settling. We use satellite and ocean reanalyses to show that the area-averaged maximum winter mixed layer depth is positively correlated with April chlorophyll concentration in the northern Labrador Sea. A simple theoretical framework is developed to understand the relative roles of winter/spring convection and gravitational sedimentation in spring blooms in this region. Combining climate model simulations that project a weakening of wintertime Labrador Sea convection from Arctic sea ice melt with our framework suggests a potentially significant reduction in the initial fall phytoplankton population that survive the winter to seed the region’s spring bloom by the end of the 21st century. PMID:29370224

Linking deep convection and phytoplankton blooms in the northern Labrador Sea in a changing climate.

PubMed

Balaguru, Karthik; Doney, Scott C; Bianucci, Laura; Rasch, Philip J; Leung, L Ruby; Yoon, Jin-Ho; Lima, Ivan D

2018-01-01

Wintertime convective mixing plays a pivotal role in the sub-polar North Atlantic spring phytoplankton blooms by favoring phytoplankton survival in the competition between light-dependent production and losses due to grazing and gravitational settling. We use satellite and ocean reanalyses to show that the area-averaged maximum winter mixed layer depth is positively correlated with April chlorophyll concentration in the northern Labrador Sea. A simple theoretical framework is developed to understand the relative roles of winter/spring convection and gravitational sedimentation in spring blooms in this region. Combining climate model simulations that project a weakening of wintertime Labrador Sea convection from Arctic sea ice melt with our framework suggests a potentially significant reduction in the initial fall phytoplankton population that survive the winter to seed the region's spring bloom by the end of the 21st century.

Temperature minima in the average thermal structure of the middle mesosphere (70 - 80 km) from analysis of 40- to 92-km SME global temperature profiles

NASA Technical Reports Server (NTRS)

Clancy, R. Todd; Rusch, David W.; Callan, Michael T.

1994-01-01

Global temperatures have been derived for the upper stratosphere and mesosphere from analysis of Solar Mesosphere Explorer (SME) limb radiance profiles. The SME temperature represent fixed local time observations at 1400 - 1500 LT, with partial zonal coverage of 3 - 5 longitudes per day over the 1982-1986 period. These new SME temperatures are compared to the COSPAR International Ionosphere Reference Atmosphere 86 (CIRA 86) climatology (Fleming et al., 1990) as well as stratospheric and mesospheric sounder (SAMS); Barnett and Corney, 1984), National Meteorological Center (NMC); (Gelman et al., 1986), and individual lidar and rocket observations. Significant areas of disagreement between the SME and CIRA 86 mesospheric temperatures are 10 K warmer SME temperatures at altitudes above 80 km. The 1981-1982 SAMS temperatures are in much closer agreement with the SME temperatures between 40 and 75 km. Although much of the SME-CIRA 86 disagreement probably stems from the poor vertical resolution of the observations comprising the CIRA 86 modelm, some portion of the differences may reflect 5- to 10-year temporal variations in mesospheric temperatures. The CIRA 86 climatology is based on 1973-1978 measurements. Relatively large (1 K/yr) 5- to 10-year trends in temperatures as functions of longitude, latitude, and altitude have been observed for both the upper stratosphere (Clancy and Rusch, 1989a) and mesosphere (Clancy and Rusch, 1989b; Hauchecorne et al., 1991). The SME temperatures also exhibit enhanced amplitudes for the semiannual oscillation (SAO) of upper mesospheric temperatures at low latitudes, which are not evident in the CIRA 86 climatology. The so-called mesospheric `temperature inversions' at wintertime midlatitudes, which have been observed by ground-based lidar (Hauschecorne et al., 1987) and rocket in situ measurements (Schmidlin, 1976), are shown to be a climatological aspect of the mesosphere, based on the SME observations.

Modeled aerosol nitrate formation pathways during wintertime in the Great Lakes region of North America

NASA Astrophysics Data System (ADS)

Kim, Yoo Jung; Spak, Scott N.; Carmichael, Gregory R.; Riemer, Nicole; Stanier, Charles O.

2014-11-01

Episodic wintertime particle pollution by ammonium nitrate is an important air quality concern across the Midwest U.S. Understanding and accurately forecasting PM2.5 episodes are complicated by multiple pathways for aerosol nitrate formation, each with uncertain rate parameters. Here, the Community Multiscale Air Quality model (CMAQ) simulated regional atmospheric nitrate budgets during the 2009 LADCO Winter Nitrate Study, using integrated process rate (IPR) and integrated reaction rate (IRR) tools to quantify relevant processes. Total nitrate production contributing to PM2.5 episodes is a regional phenomenon, with peak production over the Ohio River Valley and southern Great Lakes. Total nitrate production in the lower troposphere is attributed to three pathways, with 57% from heterogeneous conversion of N2O5, 28% from the reaction of OH and NO2, and 15% from homogeneous conversion of N2O5. TNO3 formation rates varied day-to-day and on synoptic timescales. Rate-limited production does not follow urban-rural gradients and NOx emissions due, to counterbalancing of urban enhancement in daytime HNO3 production with nocturnal reductions. Concentrations of HNO3 and N2O5 and nighttime TNO3 formation rates have maxima aloft (100-500 m), leading to net total nitrate vertical flux during episodes, with substantial vertical gradients in nitrate partitioning. Uncertainties in all three pathways are relevant to wintertime aerosol modeling and highlight the importance of interacting transport and chemistry processes during ammonium nitrate episodes, as well as the need for additional constraint on the system through field and laboratory experiments.

Maintenance of skeletal muscle energy homeostasis during prolonged wintertime fasting in the raccoon dog (Nyctereutes procyonoides).

PubMed

Kinnunen, Sanni; Mänttäri, Satu; Herzig, Karl-Heinz; Nieminen, Petteri; Mustonen, Anne-Mari; Saarela, Seppo

2015-05-01

The raccoon dog (Nyctereutes procyonoides) is a canid species with autumnal fattening and prolonged wintertime fasting. Nonpathological body weight cycling and the ability to tolerate food deficiency make this species a unique subject for studying physiological mechanisms in energy metabolism. AMP-activated protein kinase (AMPK) is a cellular energy sensor regulating energy homeostasis. During acute fasting, AMPK promotes fatty acid oxidation and enhances glucose uptake. We evaluated the effects of prolonged fasting on muscle energy metabolism in farm-bred raccoon dogs. Total and phosphorylated AMPK and acetyl-CoA carboxylase (ACC), glucose transporter 4 (GLUT 4), insulin receptor and protein kinase B (Akt) protein expressions of hind limb muscles were determined by Western blot after 10 weeks of fasting. Plasma insulin, leptin, ghrelin, glucose and free fatty acid levels were measured, and muscle myosin heavy chain (MHC) isoform composition analyzed. Fasting had no effects on AMPK phosphorylation, but total AMPK expression decreased in m. rectus femoris, m. tibialis anterior and m. extensor digitorum longus resulting in a higher phosphorylation ratio. Decreased total expression was also observed for ACC. Fasting did not influence GLUT 4, insulin receptor or Akt expression, but Akt phosphorylation was lower in m. flexor digitorum superficialis and m. extensor digitorum longus. Three MHC isoforms (I, IIa and IIx) were detected without differences in composition between the fasted and control animals. The studied muscles were resistant to prolonged fasting indicating that raccoon dogs have an effective molecular regulatory system for preserving skeletal muscle function during wintertime immobility and fasting.

Understanding High Wintertime Ozone Events over an Oil and Natural Gas Production Region from Air Quality Model Perspective

NASA Astrophysics Data System (ADS)

Ahmadov, R.; McKeen, S. A.; Trainer, M.; Banta, R. M.; Brown, S. S.; Edwards, P. M.; Frost, G. J.; Gilman, J.; Helmig, D.; Johnson, B.; Karion, A.; Koss, A.; Lerner, B. M.; Oltmans, S. J.; Roberts, J. M.; Schnell, R. C.; Veres, P. R.; Warneke, C.; Williams, E. J.; Wild, R. J.; Yuan, B.; Zamora, R. J.; Petron, G.; De Gouw, J. A.; Peischl, J.

2014-12-01

The huge increase in production of oil and natural gas has been associated with high wintertime ozone events over some parts of the western US. The Uinta Basin, UT, where oil and natural gas production is abundant experienced high ozone concentrations in winters of recent years, when cold stagnant weather conditions were prevalent. It has been very challenging for conventional air quality models to accurately simulate such wintertime ozone pollution cases. Here, a regional air quality model study was successfully conducted for the Uinta Basin by using the WRF-Chem model. For this purpose a new emission dataset for the region's oil/gas sector was built based on atmospheric in-situ measurements made during 2012 and 2013 field campaigns in the Uinta Basin. The WRF-Chem model demonstrates that the major factors driving high ozone in the Uinta Basin in winter are shallow boundary layers with light winds, high emissions of volatile organic compounds (VOC) compared to nitrogen oxides emissions from the oil and natural gas industry, enhancement of photolysis rates and reduction of O3 dry deposition due to snow cover. We present multiple sensitivity simulations to quantify the contribution of various factors driving high ozone over the Uinta Basin. The emission perturbation simulations show that the photochemical conditions in the Basin during winter of 2013 were VOC sensitive, which suggests that targeting VOC emissions would be most beneficial for regulatory purposes. Shortcomings of the emissions within the most recent US EPA (NEI-2011, version 1) inventory are also discussed.

Linking atmospheric synoptic transport, cloud phase, surface energy fluxes, and sea-ice growth: observations of midwinter SHEBA conditions

NASA Astrophysics Data System (ADS)

Persson, P. Ola G.; Shupe, Matthew D.; Perovich, Don; Solomon, Amy

2017-08-01

Observations from the Surface Heat Budget of the Arctic Ocean (SHEBA) project are used to describe a sequence of events linking midwinter long-range advection of atmospheric heat and moisture into the Arctic Basin, formation of supercooled liquid water clouds, enhancement of net surface energy fluxes through increased downwelling longwave radiation, and reduction in near-surface conductive heat flux loss due to a warming of the surface, thereby leading to a reduction in sea-ice bottom growth. The analyses provide details of two events during Jan. 1-12, 1998, one entering the Arctic through Fram Strait and the other from northeast Siberia; winter statistics extend the results. Both deep, precipitating frontal clouds and post-frontal stratocumulus clouds impact the surface radiation and energy budget. Cloud liquid water, occurring preferentially in stratocumulus clouds extending into the base of the inversion, provides the strongest impact on surface radiation and hence modulates the surface forcing, as found previously. The observations suggest a minimum water vapor threshold, likely case dependent, for producing liquid water clouds. Through responses to the radiative forcing and surface warming, this cloud liquid water also modulates the turbulent and conductive heat fluxes, and produces a thermal wave penetrating into the sea ice. About 20-33 % of the observed variations of bottom ice growth can be directly linked to variations in surface conductive heat flux, with retarded ice growth occurring several days after these moisture plumes reduce the surface conductive heat flux. This sequence of events modulate pack-ice wintertime environmental conditions and total ice growth, and has implications for the annual sea-ice evolution, especially for the current conditions of extensive thinner ice.

Particulate pollutants in the Brazilian city of São Paulo: 1-year investigation for the chemical composition and source apportionment

NASA Astrophysics Data System (ADS)

Martins Pereira, Guilherme; Teinilä, Kimmo; Custódio, Danilo; Gomes Santos, Aldenor; Xian, Huang; Hillamo, Risto; Alves, Célia A.; Bittencourt de Andrade, Jailson; Olímpio da Rocha, Gisele; Kumar, Prashant; Balasubramanian, Rajasekhar; de Fátima Andrade, Maria; de Castro Vasconcellos, Pérola

2017-10-01

São Paulo in Brazil has relatively relaxed regulations for ambient air pollution standards and often experiences high air pollution levels due to emissions of particulate pollutants from local sources and long-range transport of air masses impacted by biomass burning. In order to evaluate the sources of particulate air pollution and related health risks, a year-round sampling was done at the University of São Paulo campus (20 m a.g.l.), a green area near an important expressway. The sampling was performed for PM2. 5 ( ≤ 2. 5 µm) and PM10 ( ≤ 10 µm) in 2014 through intensive (everyday sampling in wintertime) and extensive campaigns (once a week for the whole year) with 24 h of sampling. This year was characterized by having lower average precipitation compared to meteorological data, and high-pollution episodes were observed all year round, with a significant increase in pollution level in the intensive campaign, which was performed during wintertime. Different chemical constituents, such as carbonaceous species, polycyclic aromatic hydrocarbons (PAHs) and derivatives, water-soluble ions, and biomass burning tracers were identified in order to evaluate health risks and to apportion sources. The species such as PAHs, inorganic and organic ions, and monosaccharides were determined using chromatographic techniques and carbonaceous species using thermal-optical analysis. Trace elements were determined using inductively coupled plasma mass spectrometry. The risks associated with particulate matter exposure based on PAH concentrations were also assessed, along with indexes such as the benzo[a]pyrene equivalent (BaPE) and lung cancer risk (LCR). High BaPE and LCR were observed in most of the samples, rising to critical values in the wintertime. Also, biomass burning tracers and PAHs were higher in this season, while secondarily formed ions presented low variation throughout the year. Meanwhile, vehicular tracer species were also higher in the intensive campaign, suggesting the influence of lower dispersion conditions in that period. Source apportionment was performed using positive matrix factorization (PMF), which indicated five different factors: road dust, industrial emissions, vehicular exhaust, biomass burning and secondary processes. The results highlighted the contribution of vehicular emissions and the significant input from biomass combustion in wintertime, suggesting that most of the particulate matter is due to local sources, in addition to the influence of pre-harvest sugarcane burning.

On the wintertime low bias of Northern Hemisphere carbon monoxide found in global model simulations

NASA Astrophysics Data System (ADS)

Stein, O.; Schultz, M. G.; Bouarar, I.; Clark, H.; Huijnen, V.; Gaudel, A.; George, M.; Clerbaux, C.

2014-09-01

Despite the developments in the global modelling of chemistry and of the parameterization of the physical processes, carbon monoxide (CO) concentrations remain underestimated during Northern Hemisphere (NH) winter by most state-of-the-art chemistry transport models. The consequential model bias can in principle originate from either an underestimation of CO sources or an overestimation of its sinks. We address both the role of surface sources and sinks with a series of MOZART (Model for Ozone And Related Tracers) model sensitivity studies for the year 2008 and compare our results to observational data from ground-based stations, satellite observations, and vertical profiles from measurements on passenger aircraft. In our base case simulation using MACCity (Monitoring Atmospheric Composition and Climate project) anthropogenic emissions, the near-surface CO mixing ratios are underestimated in the Northern Hemisphere by more than 20 ppb from December to April, with the largest bias of up to 75 ppb over Europe in January. An increase in global biomass burning or biogenic emissions of CO or volatile organic compounds (VOCs) is not able to reduce the annual course of the model bias and yields concentrations over the Southern Hemisphere which are too high. Raising global annual anthropogenic emissions with a simple scaling factor results in overestimations of surface mixing ratios in most regions all year round. Instead, our results indicate that anthropogenic CO and, possibly, VOC emissions in the MACCity inventory are too low for the industrialized countries only during winter and spring. Reasonable agreement with observations can only be achieved if the CO emissions are adjusted seasonally with regionally varying scaling factors. A part of the model bias could also be eliminated by exchanging the original resistance-type dry deposition scheme with a parameterization for CO uptake by oxidation from soil bacteria and microbes, which reduces the boreal winter dry deposition fluxes. The best match to surface observations, satellite retrievals, and aircraft observations was achieved when the modified dry deposition scheme was combined with increased wintertime road traffic emissions over Europe and North America (factors up to 4.5 and 2, respectively). One reason for the apparent underestimation of emissions may be an exaggerated downward trend in the Representative Concentration Pathway (RCP) 8.5 scenario in these regions between 2000 and 2010, as this scenario was used to extrapolate the MACCity emissions from their base year 2000. This factor is potentially amplified by a lack of knowledge about the seasonality of emissions. A methane lifetime of 9.7 yr for our basic model and 9.8 yr for the optimized simulation agrees well with current estimates of global OH, but we cannot fully exclude a potential effect from errors in the geographical and seasonal distribution of OH concentrations on the modelled CO.

Overview of VOC emissions and chemistry from PTR-TOF-MS measurements during the SusKat-ABC campaign: high acetaldehyde, isoprene and isocyanic acid in wintertime air of the Kathmandu Valley

NASA Astrophysics Data System (ADS)

Sarkar, Chinmoy; Sinha, Vinayak; Kumar, Vinod; Rupakheti, Maheswar; Panday, Arnico; Mahata, Khadak S.; Rupakheti, Dipesh; Kathayat, Bhogendra; Lawrence, Mark G.

2016-03-01

The Kathmandu Valley in Nepal suffers from severe wintertime air pollution. Volatile organic compounds (VOCs) are key constituents of air pollution, though their specific role in the valley is poorly understood due to insufficient data. During the SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley-Atmospheric Brown Clouds) field campaign conducted in Nepal in the winter of 2012-2013, a comprehensive study was carried out to characterise the chemical composition of ambient Kathmandu air, including the determination of speciated VOCs, by deploying a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) - the first such deployment in South Asia. In the study, 71 ion peaks (for which measured ambient concentrations exceeded the 2σ detection limit) were detected in the PTR-TOF-MS mass scan data, highlighting the chemical complexity of ambient air in the valley. Of the 71 species, 37 were found to have campaign average concentrations greater than 200 ppt and were identified based on their spectral characteristics, ambient diel profiles and correlation with specific emission tracers as a result of the high mass resolution (m / Δm > 4200) and temporal resolution (1 min) of the PTR-TOF-MS. The concentration ranking in the average VOC mixing ratios during our wintertime deployment was acetaldehyde (8.8 ppb) > methanol (7.4 ppb) > acetone + propanal (4.2 ppb) > benzene (2.7 ppb) > toluene (1.5 ppb) > isoprene (1.1 ppb) > acetonitrile (1.1 ppb) > C8-aromatics ( ˜ 1 ppb) > furan ( ˜ 0.5 ppb) > C9-aromatics (0.4 ppb). Distinct diel profiles were observed for the nominal isobaric compounds isoprene (m / z = 69.070) and furan (m / z = 69.033). Comparison with wintertime measurements from several locations elsewhere in the world showed mixing ratios of acetaldehyde ( ˜ 9 ppb), acetonitrile ( ˜ 1 ppb) and isoprene ( ˜ 1 ppb) to be among the highest reported to date. Two "new" ambient compounds, namely formamide (m / z = 46.029) and acetamide (m / z = 60.051), which can photochemically produce isocyanic acid in the atmosphere, are reported in this study along with nitromethane (a tracer for diesel exhaust), which has only recently been detected in ambient studies. Two distinct periods were selected during the campaign for detailed analysis: the first was associated with high wintertime emissions of biogenic isoprene and the second with elevated levels of ambient acetonitrile, benzene and isocyanic acid from biomass burning activities. Emissions from biomass burning and biomass co-fired brick kilns were found to be the dominant sources for compounds such as propyne, propene, benzene and propanenitrile, which correlated strongly with acetonitrile (r2 > 0.7), a chemical tracer for biomass burning. The calculated total VOC OH reactivity was dominated by acetaldehyde (24.0 %), isoprene (20.2 %) and propene (18.7 %), while oxygenated VOCs and isoprene collectively contributed to more than 68 % of the total ozone production potential. Based on known secondary organic aerosol (SOA) yields and measured ambient concentrations in the Kathmandu Valley, the relative SOA production potential of VOCs were benzene > naphthalene > toluene > xylenes > monoterpenes > trimethylbenzenes > styrene > isoprene. The first ambient measurements from any site in South Asia of compounds with significant health effects such as isocyanic acid, formamide, acetamide, naphthalene and nitromethane have been reported in this study. Our results suggest that mitigation of intense wintertime biomass burning activities, in particular point sources such biomass co-fired brick kilns, would be important to reduce the emission and formation of toxic VOCs (such as benzene and isocyanic acid) in the Kathmandu Valley.

Global emissions of refrigerants HCFC-22 and HFC-134a: Unforeseen seasonal contributions

PubMed Central

Xiang, Bin; Montzka, Stephen A.; Miller, Scot M.; Elkins, James W.; Moore, Fred L.; Atlas, Elliot L.; Miller, Ben R.; Weiss, Ray F.; Prinn, Ronald G.; Wofsy, Steven C.

2014-01-01

HCFC-22 (CHClF2) and HFC-134a (CH2FCF3) are two major gases currently used worldwide in domestic and commercial refrigeration and air conditioning. HCFC-22 contributes to stratospheric ozone depletion, and both species are potent greenhouse gases. In this work, we study in situ observations of HCFC-22 and HFC-134a taken from research aircraft over the Pacific Ocean in a 3-y span [HIaper-Pole-to-Pole Observations (HIPPO) 2009–2011] and combine these data with long-term ground observations from global surface sites [National Oceanic and Atmospheric Administration (NOAA) and Advanced Global Atmospheric Gases Experiment (AGAGE) networks]. We find the global annual emissions of HCFC-22 and HFC-134a have increased substantially over the past two decades. Emissions of HFC-134a are consistently higher compared with the United Nations Framework Convention on Climate Change (UNFCCC) inventory since 2000, by 60% more in recent years (2009–2012). Apart from these decadal emission constraints, we also quantify recent seasonal emission patterns showing that summertime emissions of HCFC-22 and HFC-134a are two to three times higher than wintertime emissions. This unforeseen large seasonal variation indicates that unaccounted mechanisms controlling refrigerant gas emissions are missing in the existing inventory estimates. Possible mechanisms enhancing refrigerant losses in summer are (i) higher vapor pressure in the sealed compartment of the system at summer high temperatures and (ii) more frequent use and service of refrigerators and air conditioners in summer months. Our results suggest that engineering (e.g., better temperature/vibration-resistant system sealing and new system design of more compact/efficient components) and regulatory (e.g., reinforcing system service regulations) steps to improve containment of these gases from working devices could effectively reduce their release to the atmosphere. PMID:25422438

Population-Level Seasonality in Cardiovascular Mortality, Blood Pressure, BMI and Inflammatory Cells in UK Biobank.

PubMed

Wyse, Cathy A; Celis Morales, Carlos A; Ward, Joey; Lyall, Donald; Smith, Daniel J; Mackay, Daniel; Curtis, Annie M; Bailey, Mark E S; Biello, Stephany; Gill, Jason M R; Pell, J P

2018-05-03

Introduction The risk of mortality from cardiovascular disease (CVD) is higher in wintertime throughout the world, but it is not known if this reflects annual changes in diet or lifestyle, or an endogenous photoperiodic mechanism that is sensitive to changes in daylength. Methods Phenotypic data on cardiometabolic and lifestyle factors were collected throughout a 4 year time period from 502,642 middle-aged participants in UK Biobank. To assess the impact of seasonal environmental changes on cardiovascular risk factors, we linked these data to the outdoor temperature and day length at the time of assessment. Self-reported information on physical activity, diet and disease status were used to adjust for confounding factors related to health and lifestyle. Results Mortality related to CVD was higher in winter, as were risk factors for this condition including blood pressure, markers of inflammation and BMI. These seasonal rhythms were significantly related to day length after adjustment for other factors that might affect seasonality including physical activity, diet and outdoor temperature. Conclusions The risk of CVD may be modulated by day length at temperate latitudes, and the implications of seasonality should be considered in all studies of human cardiometabolic health.

Decreasing but still significant facilitation effect of cold-season macrophytes on wetlands purification function during cold winter.

PubMed

Zou, Xiangxu; Zhang, Hui; Zuo, Jie; Wang, Penghe; Zhao, Dehua; An, Shuqing

2016-06-01

To identify the facilitation effect of a cool-season aquatic macrophyte (FEam) for use in effluent purification via constructed floating wetlands (CFWs) and to determine the possible pathways used during a winter period with an average temperature of less than 5 °C, pilot-scale CFWs were planted with the cold-season macrophyte Oenanthe clecumbens and were operated as batch systems. Although some leaves withered, the roots retained relatively high levels of activity during the winter, which had average air and water temperatures of 3.63 and 5.04 °C, respectively. The N and P removal efficiencies in CFWs decreased significantly in winter relative to those in late autumn. The presence of cool-season plants resulted in significant improvements in N and P removal, with a FEam of 15.23-25.86% in winter. Microbial N removal accounted for 71.57% of the total N removed in winter, and the decrease in plant uptake was the dominant factor in the wintertime decrease in N removal relative to that in late autumn. These results demonstrate the importance of cold-season plants in CFWs for the treatment of secondary effluent during cold winters.

Climate Simulations with an Isentropic Finite Volume Dynamical Core

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

Chen, Chih-Chieh; Rasch, Philip J.

2012-04-15

This paper discusses the impact of changing the vertical coordinate from a hybrid pressure to a hybrid-isentropic coordinate within the finite volume dynamical core of the Community Atmosphere Model (CAM). Results from a 20-year climate simulation using the new model coordinate configuration are compared to control simulations produced by the Eulerian spectral and FV dynamical cores of CAM which both use a pressure-based ({sigma}-p) coordinate. The same physical parameterization package is employed in all three dynamical cores. The isentropic modeling framework significantly alters the simulated climatology and has several desirable features. The revised model produces a better representation of heatmore » transport processes in the atmosphere leading to much improved atmospheric temperatures. We show that the isentropic model is very effective in reducing the long standing cold temperature bias in the upper troposphere and lower stratosphere, a deficiency shared among most climate models. The warmer upper troposphere and stratosphere seen in the isentropic model reduces the global coverage of high clouds which is in better agreement with observations. The isentropic model also shows improvements in the simulated wintertime mean sea-level pressure field in the northern hemisphere.« less

Actual and future trends of extreme values of temperature for the NW Iberian Peninsula

NASA Astrophysics Data System (ADS)

Taboada, J.; Brands, S.; Lorenzo, N.

2009-09-01

It is now very well established that yearly averaged temperatures are increasing due to anthropogenic climate change. In the area of Galicia (NW Spain) this trend has also been determined. The main objective of this work is to assess actual and future trends of different extreme indices of temperature, which are of curcial importance for many impact studies. Station data for the study was provided by the CLIMA database of the regional government of Galicia (NW Spain). As direct GCM-output significantly underestimates the variance of daily surface temperature variables in NW Spain, these variables are obtained by applying a statistical downscaling technique (analog method), using 850hPa temperature and mean sea level pressure as combined predictors. The predictor fields have been extracted from three GCMs participating in the IPCC AR4 under A1, A1B and A2 scenarios. The definitions of the extreme indices have been taken from the joint CCl/CLIVAR/JCOMM Expert Team (ET) on Climate Change Detection and Indices (ETCCDI) This group has defined a set of standard extreme values to simplify intercomparisons of data from different regions of the world. For the temperatures in the period 1960-2006, results show a significant increase of the number of days with maximum temperatures above the 90th percentile. Furthermore, a significant decrease of the days with maximum temperatures below the 10th percentile has been found. The tendencies of minimum temperatures are reverse: less nights with minimum temperatures below 10th percentile, and more with minimum temperatures above 90th percentile. Those tendencies can be observed all over the year, but are more pronounced in summer. We have also calculated the relationship between the above mentioned extreme values and different teleconnection patterns appearing in the North Atlantic area. Results show that local tendencies are associated with trends of EA (Eastern Atlantic) and SCA (Scandinavian) patterns. NAO (North Atlantic Oscillation) has also some relationship with these tendencies, but only related with cold days and nights in winter. The results of the applied statistical downscaling technique indicate that observed trends in maximum and minimum temperatures in NW Spain are expected to continue in the next decades because of anthropogenic climate change. The common tendency is that hot days increase while cold nights diminish all over the year. As expected, these tendencies change between different scenarios: they are more marked for A2 and A1B scenarios than for the for the B1 scenario. Moreover, the three models behave different under the same scenario, leaving a great uncertainty for the future. Nevertheless, we conclude that more frequent hot days, as well as an increasing probability of summertime heat waves are to be expected in the next decades. Cold days tend to diminish, decreasing the probability of wintertime cold waves and leaving a greater part of the area under study without frost days throughout the year.

Arctic Ocean Circulation Patterns Revealed by GRACE

NASA Astrophysics Data System (ADS)

Peralta-Ferriz, Cecilia; Morison, James H.; Wallace, John M.; Bonin, Jennifer A.; Zhang, Jinlun

2013-04-01

EOF analysis of non-seasonal, month-to-month variations in GRACE derived Arctic Ocean bottom pressure (OBP) yield three dominant modes. The first mode is a wintertime basin wide variation in mass associated with high atmospheric pressure (SLP) over Scandinavia. The second mode is a shift of mass from the central Arctic Ocean to the Siberian shelves due to low pressure over the basins, associated with the strength of the Arctic Oscillation. The third mode is a shift in mass between the Eastern and Western Siberian shelves, related to strength of the Beaufort High mainly in summer, and to eastward alongshore winds on the Barents Sea in winter. The PIOMAS and ECCO2 modeled OBP are consistent with the form of these modes and provide context in terms of variations in sea surface height. The models are used to investigate the ocean dynamics associated with each mode of OBP variability.

The Mars water cycle

NASA Technical Reports Server (NTRS)

Davies, D. W.

1981-01-01

A model has been developed to test the hypothesis that the observed seasonal and latitudinal distribution of water on Mars is controlled by the sublimation and condensation of surface ice deposits in the Arctic and Antarctic, and the meridional transport of water vapor. Besides reproducing the observed water vapor distribution, the model correctly reproduces the presence of a large permanent ice cap in the Arctic and not in the Antarctic. No permanent ice reservoirs are predicted in the temperate or equatorial zones. Wintertime ice deposits in the Arctic are shown to be the source of the large water vapor abundances observed in the Arctic summertime, and the moderate water vapor abundances in the northern temperate region. Model calculations suggest that a year without dust storms results in very little change in the water vapor distribution. The current water distribution appears to be the equilibrium distribution for present atmospheric conditions.

Regional temperature and precipitation changes under high-end (≥4°C) global warming.

PubMed

Sanderson, M G; Hemming, D L; Betts, R A

2011-01-13

Climate models vary widely in their projections of both global mean temperature rise and regional climate changes, but are there any systematic differences in regional changes associated with different levels of global climate sensitivity? This paper examines model projections of climate change over the twenty-first century from the Intergovernmental Panel on Climate Change Fourth Assessment Report which used the A2 scenario from the IPCC Special Report on Emissions Scenarios, assessing whether different regional responses can be seen in models categorized as 'high-end' (those projecting 4°C or more by the end of the twenty-first century relative to the preindustrial). It also identifies regions where the largest climate changes are projected under high-end warming. The mean spatial patterns of change, normalized against the global rate of warming, are generally similar in high-end and 'non-high-end' simulations. The exception is the higher latitudes, where land areas warm relatively faster in boreal summer in high-end models, but sea ice areas show varying differences in boreal winter. Many continental interiors warm approximately twice as fast as the global average, with this being particularly accentuated in boreal summer, and the winter-time Arctic Ocean temperatures rise more than three times faster than the global average. Large temperature increases and precipitation decreases are projected in some of the regions that currently experience water resource pressures, including Mediterranean fringe regions, indicating enhanced pressure on water resources in these areas.

Decadal Trends and Variability of Tropospheric Ozone over Oil and Gas Regions over 2005 - 2015

NASA Astrophysics Data System (ADS)

Zhou, Y.; Mao, H.; Sive, B. C.

2017-12-01

Tropospheric ozone (O3), which is produced largely by photochemical oxidation of nitrogen oxides (NOx) and volatile organic compounds, is a serious and ubiquitous air pollutant with strong negative health effects. Recent technological innovations such as horizontal drilling and hydraulic fracturing have accelerated oil and natural gas production in the U.S. since 2005. The additional input of O3 precursors from expanding natural gas production might prolong the effort to comply the current O3 standard (70 ppbv). The objective of this study is to investigate the impact of oil and gas extractions on variability and long term trends of O3 in the intermountain west under varying meteorological conditions. We investigated long-term O3 trends at 13 rural sites, which were within 100 km of the shale play in the U.S. intermountain west. Significant decreasing trends (-0.35 - -3.38 ppbv yr-1) were found in seasonal O3 design values at six sites in spring, summer, or fall, while no trends were found in wintertime O3 at any sites. Wintertime O3 at each site showed strong and consistent interannual variation over 2006 - 2015, and was negatively correlated with the Arctic Oscillation (AO) Index. The negative correlation was a result of multiple factors, such as in situ O3 photochemical production, stratospheric intrusion, and transport from the Arctic and California. In summer, wildfire emissions were the dominate driver to the interannual variations of high percentiles O3 at each site, while meteorological conditions (i.e., temperature and relative humidity) determined the interannual variations of low percentiles O3. Box model simulations indicated that O3 production rates were 31.51 ppbv h-1 over winters of 2012 - 2014 and 32.12 ppbv h-1 in summer 2014 around shale gas extraction regions.

Comparison of Wintertime Ozone Production Associated With Oil and Gas Extraction Activity in Wyoming and Utah

NASA Astrophysics Data System (ADS)

Oltmans, S. J.; Schnell, R. C.; Mefford, T. K.; Neely, R. R., III

2012-12-01

The wintertime cold, reduced sunlight conditions of the mid-latitudes of continental interior locations are normally not considered to be conducive to significant ozone production. Recent observations have shattered this expectation with hourly ozone mixing ratios regularly exceeding 100 ppb measured in January, February and March in the states of Wyoming and Utah in the United States. Maximum daily eight hour average ozone mixing ratios have exceeded 100 ppb, far exceeding the U.S. threshold of 75 ppb. Conditions under which this dramatic ozone production takes place include a mix of high levels of ozone precursors (NOx and VOCs), a very stable and shallow boundary layer, snow cover providing enhanced UV radiation, and air confining terrain features. The high levels of precursors have been tied to oil and gas extraction activities in the affected regions. Under the requisite meteorological conditions where high pressure, low winds, and snow-covered ground are present extremely stable and shallow (~50-200 m) boundary layers persist. The highly reflective snow cover provides enhanced photolysis rates that in February can exceed those in June. For several winters in Utah and Wyoming with large ozone enhancements, the time series of various meteorological (wind, temperature, solar radiation, snow cover) and chemical parameters (ozone and NOx) show a somewhat different progression of high ozone events between the two locations. In the Unitah Basin of Utah high ozone formation conditions are more persistent throughout the winter than in the Pinedale Anticline region of Wyoming. This is likely a function of the differing topography of the two areas. However, for individual events the two sites show a similar progression of rapid ozone formation each day. Sites in both Utah and Wyoming just outside the oil and gas extraction activity areas show little or no enhanced ozone. Winters without the requisite meteorological conditions also do not experience high ozone events.

Global Emissions of Refrigerants HCFC-22 and HFC-134a: Unforeseen Seasonal Contributions

NASA Astrophysics Data System (ADS)

Xiang, B.; Patra, P. K.; Montzka, S. A.; Miller, S. M.; Elkins, J. W.; Moore, F.; Atlas, E. L.; Miller, B. R.; Prinn, R. G.; Wofsy, S. C.

2014-12-01

HCFC-22 (CHClF2) and HFC-134a (CH2FCF3) are two major gases currently used worldwide in domestic and commercial refrigeration and air conditioning. HCFC-22 contributes to stratospheric ozone depletion and both species are potent greenhouse gases, and their global emissions continue to rise at the present. In this work, we study aircraft based in-situ observations of HCFC-22 and HFC-134a over the Pacific Ocean in a three-year span (HIaper Pole-to-Pole Observation of carbon cycle and greenhouse gases study, HIPPO 2009-2011) and combine these data with long-term observations from global surface sites (NOAA and AGAGE networks). We find a steady increase in global annual emissions of HCFC-22 and HFC-134a for the past two decades (on average 3% and 4% per year, respectively). Emissions of HFC-134a since 2000 are consistently higher, with 60% more in recent years (2009-2011), compared to the United Nations Framework Convention on Climate Change (UNFCCC) inventory. Using both HIPPO and surface data, we quantify and verify enhanced summertime emissions of HFC-134a and HCFC-22 that are about three times those in the wintertime. This unforeseen large seasonal contribution indicates unaccounted mechanisms controlling refrigerant gas emissions, missing in the existing inventory estimates. Possible mechanisms for greater refrigerant leakages in the summer are: 1) higher vapor pressure in the sealed compartment of the system at summer high temperatures (saturated vapor pressure is ~ 3 times at 303 K compared to that at 273 K for both species), and 2) more frequent use of refrigeration and air conditioners in the summer (vapor pressure in the compressor line is higher when in use than not in use). Our results suggest that the engineering of the refrigeration and air conditioning systems can greatly influence the release of these two species to the atmosphere.

A Process-Based Insight into the Severity of 'Super' Storm Desmond

NASA Astrophysics Data System (ADS)

Matthews, Tom; Murphy, Conor; Gerard, McCarthy; Rob, Wilby

2017-04-01

Climate warming is projected to increase winter rainfall and societally-impactful flood frequency across the British-Irish Isles (BI). The dynamical explanation for this change is linked to the North Atlantic (NA) storm track, with projections indicating both an enhanced frequency of wintertime extratropical cyclones ('cyclones'), and an increase in their average precipitation. The latter is, in part, a result of more intense moisture transport in cyclones' warm sectors by 'Atmospheric Rivers' (ARs), thermodynamically-driven by enhanced absolute humidity consistent with the Clausius-Clapeyron relation. It is against this backdrop that we scrutinise the physical drivers of the record-breaking rain and flood event associated with 'Storm Desmond' in December, 2015. We find that more than 3,500 km2 experienced rainfall in excess of the mean annual maximum during the storm's passage. The exceptional rain amounts were due to an AR more intense than any other in our observational record (1979-2015). However, we find that its unparalleled strength was as much a consequence of strong wind speeds as high humidity, so its severity cannot be attributed so simply to climate warming. This position is made clearer through a Lagrangian air mass tracking procedure, where we show that most (67%) of the moisture that precipitated out over BI during Desmond's passage evaporated from sea surfaces that were cooler than their 1951-1980 average. We therefore conclude that 1) the process-based observational approach applied here can provide valuable insight into climate change attribution assessments; and 2) Storm Desmond - despite being the most severe on record - was perhaps moderated by the anomalously cool NA sea-surface temperatures, which may have suppressed evaporation and vapour transport. The capacity for an even more impactful AR should SSTs in the sub-polar NA return to even their 20th Century averages, given otherwise identical synoptic circulation, should therefore be appreciated by planners and policy makers alike.

Warm season heavy rainfall events over the Huaihe River Valley and their linkage with wintertime thermal condition of the tropical oceans

NASA Astrophysics Data System (ADS)

Li, Laifang; Li, Wenhong; Tang, Qiuhong; Zhang, Pengfei; Liu, Yimin

2016-01-01

Warm season heavy rainfall events over the Huaihe River Valley (HRV) of China are amongst the top causes of agriculture and economic loss in this region. Thus, there is a pressing need for accurate seasonal prediction of HRV heavy rainfall events. This study improves the seasonal prediction of HRV heavy rainfall by implementing a novel rainfall framework, which overcomes the limitation of traditional probability models and advances the statistical inference on HRV heavy rainfall events. The framework is built on a three-cluster Normal mixture model, whose distribution parameters are sampled using Bayesian inference and Markov Chain Monte Carlo algorithm. The three rainfall clusters reflect probability behaviors of light, moderate, and heavy rainfall, respectively. Our analysis indicates that heavy rainfall events make the largest contribution to the total amount of seasonal precipitation. Furthermore, the interannual variation of summer precipitation is attributable to the variation of heavy rainfall frequency over the HRV. The heavy rainfall frequency, in turn, is influenced by sea surface temperature anomalies (SSTAs) over the north Indian Ocean, equatorial western Pacific, and the tropical Atlantic. The tropical SSTAs modulate the HRV heavy rainfall events by influencing atmospheric circulation favorable for the onset and maintenance of heavy rainfall events. Occurring 5 months prior to the summer season, these tropical SSTAs provide potential sources of prediction skill for heavy rainfall events over the HRV. Using these preceding SSTA signals, we show that the support vector machine algorithm can predict HRV heavy rainfall satisfactorily. The improved prediction skill has important implication for the nation's disaster early warning system.

Quantifying wintertime boundary layer ozone production from frequent profile measurements in the Uinta Basin, UT, oil and gas region

NASA Astrophysics Data System (ADS)

Schnell, Russell C.; Johnson, Bryan J.; Oltmans, Samuel J.; Cullis, Patrick; Sterling, Chance; Hall, Emrys; Jordan, Allen; Helmig, Detlev; Petron, Gabrielle; Ahmadov, Ravan; Wendell, James; Albee, Robert; Boylan, Patrick; Thompson, Chelsea R.; Evans, Jason; Hueber, Jacques; Curtis, Abigale J.; Park, Jeong-Hoo

2016-09-01

As part of the Uinta Basin Winter Ozone Study, January-February 2013, we conducted 937 tethered balloon-borne ozone vertical and temperature profiles from three sites in the Uinta Basin, Utah (UB). Emissions from oil and gas operations combined with snow cover were favorable for producing high ozone-mixing ratios in the surface layer during stagnant and cold-pool episodes. The highly resolved profiles documented the development of approximately week-long ozone production episodes building from regional backgrounds of 40 ppbv to >165 ppbv within a shallow cold pool up to 200 m in depth. Beginning in midmorning, ozone-mixing ratios increased uniformly through the cold pool layer at rates of 5-12 ppbv/h. During ozone events, there was a strong diurnal cycle with each succeeding day accumulating 4-8 ppbv greater than the previous day. The top of the elevated ozone production layer was nearly uniform in altitude across the UB independent of topography. Above the ozone production layer, mixing ratios decreased with height to 400 m above ground level where they approached regional background levels. Rapid clean-out of ozone-rich air occurred within a day when frontal systems brought in fresh air. Solar heating and basin topography led to a diurnal flow pattern in which daytime upslope winds distributed ozone precursors and ozone in the Basin. NOx-rich plumes from a coal-fired power plant in the eastern sector of the Basin did not appear to mix down into the cold pool during this field study.

Arctic sea ice loss and recent extreme cold winter in Eurasia

NASA Astrophysics Data System (ADS)

Mori, Masato; Watanabe, Masahiro; Ishii, Masayoshi; Kimoto, Masahide

2014-05-01

Extreme cold winter over the Eurasia has occurred more frequently in recent years. Observational evidence in recent studies shows that the wintertime cold anomalies over the Eurasia are associated with decline of Arctic sea ice in preceding autumn to winter season. However, the tropical and/or mid-latitude sea surface temperature (SST) anomalies have great influence on the mid- and high-latitude atmospheric variability, it is difficult to isolate completely the impacts of sea ice change from observational data. In this study, we examine possible linkage between the Arctic sea ice loss and the extreme cold winter over the Eurasia using a state-of-the-art MIROC4 (T106L56) atmospheric general circulation model (AGCM) to assess the pure atmospheric responses to sea ice reduction. We perform two sets of experiments with different realistic sea ice boundary conditions calculated by composite of observed sea ice concentration; one is reduced sea ice extent case (referred to as LICE run) and another is enhanced case (HICE run). In both experiments, the model is integrated 6-month from September to February with 100-member ensemble under the climatological SST boundary condition. The difference in ensemble mean of each experiment (LICE minus HICE) shows cold anomalies over the Eurasia in winter and its spatial pattern is very similar to corresponding observation, though the magnitude is smaller than observation. This result indicates that a part of observed cold anomaly can be attributed to the Arctic sea ice loss. We would like to introduce more important results and mechanisms in detail in my presentation.

Non-methane volatile organic compounds in Africa: A view from space

NASA Astrophysics Data System (ADS)

Marais, Eloise Ann

Isoprene emissions affect human health, air quality, and the oxidative capacity of the atmosphere. Globally anthropogenic non-methane volatile organic compounds (NMVOC) emissions are lower than that of isoprene, but local hotspots are hazardous to human health and air quality. In Africa the tropics are a large source of isoprene, while Nigeria appears as a large contributor to regional anthropogenic NMVOC emissions. I make extensive use of space-based formaldehyde (HCHO) observations from the Ozone Monitoring Instrument (OMI) and the chemical transport model (CTM) GEOS-Chem to estimate and examine seasonality of isoprene emissions across Africa, and identify sources and air quality consequences of anthropogenic NMVOC emissions in Nigeria. To estimate isoprene emissions I first developed a filtering scheme to remove (1) contamination from biomass burning and anthropogenic influences; and (2) displacement of HCHO from the isoprene emission source diagnosed with the GEOS-Chem CTM. Conversion to isoprene emissions is with NOx-dependent GEOS-Chem HCHO yields, obtained as the local sensitivity S of the HCHO column ΩHCHO to a perturbation Delta in isoprene emissions EISOP (S = DeltaΩHCHO/DeltaE ISOP). The error in OMI-derived isoprene emissions is 40% at low levels of NOx and 40-90% under high-NOx conditions and is reduced by spatial and temporal averaging to the extent that errors are random. Weak isoprene emission seasonality in equatorial forests is driven predominantly by temperature, while large seasonality in northern and southern savannas is driven by temperature and leaf area index. The largest contribution of African isoprene emissions to surface ozone and particulate matter, determined with GEOS-Chem, of 8 ppbv and 1.5 μg m-3, respectively, is over West Africa. The OMI HCHO data feature a large enhancement over Nigeria that is due to anthropogenic NMVOC emissions. With the OMI HCHO data, coincident satellite observations of atmospheric composition, aircraft measurements, and GEOS-Chem I estimate Nigerian NMVOC emissions that are higher per capita than China (5.7 Tg C a-1). Should Nigeria develop its electricity sector to sustain economic growth with local natural gas and coal reserves NO x emissions will exacerbate wintertime (December-February) surface ozone pollution that exceeds 90 ppbv due to poor ventilation and the Harmattan inversion layer.

The Wintertime Covariation of CO2 and Criteria Pollutants in an Urban Valley of the Western United States

NASA Astrophysics Data System (ADS)

Bares, Ryan; Lin, John C.; Hoch, Sebastian W.; Baasandorj, Munkhbayar; Mendoza, Daniel L.; Fasoli, Ben; Mitchell, Logan; Catharine, Douglas; Stephens, Britton B.

2018-03-01

Numerous mountain valleys experience wintertime particulate pollution events, when persistent cold air pools (PCAPs) develop and inhibit atmospheric mixing, leading to the accumulation of pollutants. Here we examine the relationships between trace gases and criteria pollutants during winter in Utah's Salt Lake Valley, in an effort to better understand the roles of transport versus chemical processes during differing meteorological conditions as well as insights into how targeted reductions in greenhouse gases will impact local air quality in varying meteorological conditions. CO2 is a chemically inert gas that is coemitted during fossil fuel combustion with pollutants. Many of these coemitted pollutants are precursors that react chemically to form secondary particulate matter. Thus, CO2 can serve as a stable tracer and potentially help distinguish transport versus chemical influences on pollutants. During the winter of 2015-2016, we isolated enhancements in CO2 over baseline levels due to urban emissions ("CO2ex"). CO2ex was paired with similar excesses in other pollutant concentrations. These relationships were examined during different wintertime conditions and stages of pollution episodes: (a) Non-PCAP, (b) beginning, and (c) latter stages of an episode. We found that CO2ex is a good indicator of the presence of gaseous criteria pollutants and a reasonable indicator of PM2.5. Additionally, the relationships between CO2ex and criteria pollutants differ during different phases of PCAP events which provide insight into meteorological and transport processes. Lastly, we found a slight overestimation of CO:CO2 emission ratios and a considerable overestimation of NOx:CO2 by existing inventories for the Salt Lake Valley.

Composition and sources of winter haze in the Bakken oil and gas extraction region

NASA Astrophysics Data System (ADS)

Evanoski-Cole, A. R.; Gebhart, K. A.; Sive, B. C.; Zhou, Y.; Capps, S. L.; Day, D. E.; Prenni, A. J.; Schurman, M. I.; Sullivan, A. P.; Li, Y.; Hand, J. L.; Schichtel, B. A.; Collett, J. L.

2017-05-01

In the past decade increased use of hydraulic fracturing and horizontal drilling has dramatically expanded oil and gas production in the Bakken formation region. Long term monitoring sites have indicated an increase in wintertime aerosol nitrate and sulfate in this region from particulate matter (PM2.5) measurements collected between 2000 and 2010. No previous intensive air quality field campaign has been conducted in this region to assess impacts from oil and gas development on regional fine particle concentrations. The research presented here investigates wintertime PM2.5 concentrations and composition as part of the Bakken Air Quality Study (BAQS). Measurements from BAQS took place over two wintertime sampling periods at multiple sites in the United States portion of the Bakken formation and show regionally elevated episodes of PM2.5 during both study periods. Ammonium nitrate was a major contributor to haze episodes. Periods of air stagnation or recirculation were associated with rapid increases in PM2.5 concentrations. Volatile organic compound (VOC) signatures suggest that air masses during these episodes were dominated by emissions from the Bakken region itself. Formation rates of alkyl nitrates from alkanes revealed an air mass aging timescale of typically less than a day for periods with elevated PM2.5. A thermodynamic inorganic aerosol model (ISORROPIA) was used to investigate gas-particle partitioning and to examine the sensitivity of PM2.5 concentrations to aerosol precursor concentrations. Formation of ammonium nitrate, the dominant component, was most sensitive to ammonia concentrations during winter and to nitric acid concentrations during early spring when ammonia availability increases. The availability of excess ammonia suggests capacity for further ammonium nitrate formation if nitrogen oxide emissions increase in the future and lead to additional secondary formation of nitric acid.

Constraining ammonia dairy emissions during NASA DISCOVER-AQ California: surface and airborne observation comparisons with CMAQ simulations

NASA Astrophysics Data System (ADS)

Miller, D. J.; Liu, Z.; Sun, K.; Tao, L.; Nowak, J. B.; Bambha, R.; Michelsen, H. A.; Zondlo, M. A.

2014-12-01

Agricultural ammonia (NH3) emissions are highly uncertain in current bottom-up inventories. Ammonium nitrate is a dominant component of fine aerosols in agricultural regions such as the Central Valley of California, especially during winter. Recent high resolution regional modeling efforts in this region have found significant ammonium nitrate and gas-phase NH3 biases during summer. We compare spatially-resolved surface and boundary layer gas-phase NH3 observations during NASA DISCOVER-AQ California with Community Multi-Scale Air Quality (CMAQ) regional model simulations driven by the EPA NEI 2008 inventory to constrain wintertime NH3 model biases. We evaluate model performance with respect to aerosol partitioning, mixing and deposition to constrain contributions to modeled NH3 concentration biases in the Central Valley Tulare dairy region. Ammonia measurements performed with an open-path mobile platform on a vehicle are gridded to 4 km resolution hourly background concentrations. A peak detection algorithm is applied to remove local feedlot emission peaks. Aircraft NH3, NH4+ and NO3- observations are also compared with simulations extracted along the flight tracks. We find NH3 background concentrations in the dairy region are underestimated by three to five times during winter and NH3 simulations are moderately correlated with observations (r = 0.36). Although model simulations capture NH3 enhancements in the dairy region, these simulations are biased low by 30-60 ppbv NH3. Aerosol NH4+ and NO3- are also biased low in CMAQ by three and four times respectively. Unlike gas-phase NH3, CMAQ simulations do not capture typical NH4+ or NO3- enhancements observed in the dairy region. In contrast, boundary layer height simulations agree well with observations within 13%. We also address observational constraints on simulated NH3 deposition fluxes. These comparisons suggest that NEI 2008 wintertime dairy emissions are underestimated by a factor of three to five. We test sensitivity to emissions by increasing the NEI 2008 NH3 emissions uniformly across the dairy region and evaluate the impact on modeled concentrations. These results are applicable to improving predictions of ammoniated aerosol loading and highlight the value of mobile platform spatial NH3 measurements to constrain emission inventories.

Asymmetric seasonal march from autumn to the next spring in East Asia (Toward interdisciplinary education on the climate systems and the "seasonal feeling" such as around the Japan Islands area)

NASA Astrophysics Data System (ADS)

Kato, Kuranoshin; Kato, Haruko; Sato, Sari; Akagi, Rikako; Haga, Yuichi; Miyake, Shoji

2014-05-01

There are many steps of seasonal transitions in East Asia, greatly influenced by the considerable phase differences of seasonal cycle among the Asian monsoon subsystems, resulting in the variety of "seasonal feeling" around the Japan Islands. For example, the "wintertime pressure pattern" begins to prevail already from November due to the seasonal development of the Siberian Air mass and the Siberian High, although the air temperature around the Japan Islands is still rather higher than in midwinter. On the other hand, since the southward retreat of the warm moist air mass in the western Pacific area delays rather greatly to the advances of those northern systems. Thus it would be interesting to re-examine the whole seasonal cycle around the Japan Islands at the view point of how the phase differences among seasonal marches of the Asian monsoon subsystems affect the variety of the seasonal cycle there, together with their effects on the "seasonal feeling". As such, the present study will examine the asymmetric seasonal march from autumn to the next spring through midwinter around the Japan Islands as an interesting example, and will also report the joint activity with music, and so on, toward the development of an interdisciplinary study plan on such topics for the students in junior high school, high school and the faculty of education of the university. The wintertime weather pattern, i.e., precipitation in the Japan Sea side and clear day in the Pacific side of the Japan Islands, prevails from early November to early March, reflected by the seasonal cycle of the Siberian Air Mass and the Siberian High. However, the air temperature shows the minimum from late January to early February around the Japan Islands. In other words, although the dominant weather patterns around November and in early March are nearly the same as each other, air temperature is still lower in early March (early spring). In spite of that, the solar radiation is rather stronger in early March. Comparison of "seasonal feeling" expressed in the Japanese classic poems called "Wa-Ka", the Japanese school songs, and so on, between those seasons was also made, referring to the asymmetric seasonal march as just mentioned above. We would like to introduce also the results of the trial of the class at Kurashiki-Seiryo High School or Faculty of Education of Okyama University. We should note that the present joint activity might also contribute to providing the study materials for the cultural understanding, which is one of the important elements for the ESD (Education for Sustainable Development).

RADIOCARBON MEASUREMENTS ON PM 2.5 AMBIENT AEROSOL FROM NASHVILLE, TN

EPA Science Inventory

Radiocarbon (Carbon-14) measurements provide an estimate of the fraction of carbon in a sample that is biogenic. The methodology has been extensively used in past wintertime studies to quantify the contribution of wood smoke to ambient aerosol. In summertime such measurements...

RADIOCARBON MEASUREMENTS ON PM-2.5 AMBIENT AEROSOL

EPA Science Inventory

Radiocarbon (14C) measurements provide an estimate of the fraction of carbon in a sample that is biogenic. The methodology has been extensively used in past wintertime studies to quantify the contribution of wood smoke to ambient aerosol. In summertime such measurements can p...

A Midwinter Minimum in North Atlantic Storm Track Intensity in Years of a Strong Jet

NASA Astrophysics Data System (ADS)

Afargan, H.; Kaspi, Y.

2017-12-01

This study investigates the occurrence of a midwinter suppression in synoptic eddy activity within the North Atlantic storm track. It is found that eddy kinetic energy over the Atlantic is reduced during winter relative to fall and spring, despite the stronger wintertime jet and enhanced baroclinicity. This behavior is similar to the well-known Pacific midwinter minimum, yet the reduction over the Atlantic is smaller and persists for a shorter period. To examine the conditions favorable for this phenomenon, we present an analysis of years with stronger jet intensity versus years of weaker jets over the Atlantic and Pacific basins. When the wintertime jet is stronger, the midwinter suppression of eddy activity is more pronounced, and the jet is more equatorward. Since the climatological Atlantic jet is weaker relative to the Pacific jet, the conditions for a midwinter suppression in the Atlantic are generally less favorable, yet a midwinter suppression often occurs in years of a strong jet.

The seasonal variation of nonmethane hydrocarbons in the free troposphere over the North Atlantic Ocean - Possible evidence for extensive reaction of hydrocarbons with the nitrate radical

NASA Astrophysics Data System (ADS)

Penkett, S. A.; Blake, N. J.; Lightman, P.; Marsh, A. R. W.; Anwyl, P.; Butcher, G.

1993-02-01

Observations of the buildup in wintertime of a substantial concentration of hydrocarbons in the free troposphere over the North Atlantic Ocean are extended to the seasonal cycles of a much wider range of hydrocarbons, from C2 to C8. A large seasonal variation was found in the hydrocarbon content in the free troposphere over the north Atlantic Ocean. The maximum carbon concentration occurs in winter and is of the order of 20 ppbv in the form of reactive carbon compounds with lifetimes of days to months. The hydrocarbon content of air in winter over the Atlantic depends greatly on its source area, with polar maritime air containing much higher concentrations than air with a tropical maritime origin. There is evidence from detailed hydrocarbon data that NO3 chemistry may play a significant role in the removal of hydrocarbons from the atmosphere. This is more evident in the wintertime, when the hydroxyl chemistry is less dominant.

Evidence for S(IV) compounds other than dissolved SO2 in precipitation

NASA Astrophysics Data System (ADS)

Chapman, E. G.

1986-12-01

Preliminary results from a study characterizing S(IV) compounds in wintertime precipitation samples indicate that bisulfite ion is not the primary form of S(IV), as previously believed. By employing a differencing technique that permits estimation of both SO2 aq and non-SO2 aq compound concentrations, it was found that, on an average, more than 60 percent of the total S(IV) is present in a form other than dissolved SO2. Formaldehyde analyses on selected samples suggest that the most likely form of the S(IV) is hydroxymethanesulfonate, although other aldehyde-S(IV) adducts may also be present. The non-SO2 compounds represented a significant portion of the total sulfur concentrations present in the samples analyzed, with contributions ranging from 1.2 to 27 percent. Because of the stability and oxidation resistance of these S(IV) compounds, sulfur deposition estimates that are based solely on sulfate measurements are undoubtedly low, especially for wintertime events. The study underscores the importance of S(IV) compounds in atmospheric scavenging processes.

Numerical Study of the Wintertime Planetary Boundary Layer Development in the Urban Area of Sao Paulo - Brazil

NASA Astrophysics Data System (ADS)

Ribeiro, F. N. D.; Soares, J.; Oliveira, A. P.; Miranda, R. M.; Chen, F.

2015-12-01

The gradual replacement of natural by built surfaces and the ongoing emission of particulate matter and other pollutants that happens in urban environments, besides degrading the environment, influence the local weather and climate patterns. Urban areas have different albedo, heat and hydraulic capacity and conductivity, roughness, emissivity, and transmissivity, when compared to naturally vegetated areas. This set of characteristics may change the surface energy budget, air temperature, humidity, atmospheric chemical composition, wind direction and velocity, and therefore the planetary boundary layer (PBL) development. The effects of urbanization on the PBL have been studied in many mid-latitude areas, however in the tropical or subtropical areas they are scarce. The MCITY Brazil project developed in 2 cities of Brazil, Sao Paulo (23°32' S) and Rio de Janeiro (latitude 22° 55' S), has provided the necessary data to properly investigate the effects of urbanization in these two cities. The project included a campaign of soundings launched every 3 hours for 10 consecutive days in August (Austral winter) from an airport at the north part of the city of Sao Paulo, that allowed the study of the PBL development, and also the measurements of the components of the energy budget equation by micrometeorological towers. Therefore, the goal of this work is to simulate the development of the PBL in the metropolitan area of Sao Paulo during winter, comparing its characteristics in urbanized and non urbanized sites, in order to assess the impact of urbanization on the development of the PBL in this area. The model used is the Weather Research and Forecast (WRF) with a single layer urban canopy parameterization (SLUCM) and realistic anthropogenic heat diurnal evolution. Preliminary results showed that the model is able to reproduce the PBL development during the campaign, including the passage of a cold-frontal system. The urban PBL reaches greater heights during the day than the PBL in non urban sites, suggesting that the urban sites generate more turbulence. Daytime urban PBL height reaches up to 2000 m and nighttime is usually less than 200 m. The surface turbulent fluxes and the energy budget near the surface will also be compared to observations and discussed.

Impact of Future Emissions and Climate Change on Surface Ozone over China

NASA Astrophysics Data System (ADS)

Ma, C. T.; Westervelt, D. M.; Fiore, A. M.; Rieder, H. E.; Kinney, P.; Wang, S.; Correa, G. J. P.

2017-12-01

China's immense ambient air pollution problem and world-leading greenhouse gas emissions place it at the forefront of global efforts to address these related environmental concerns. Here, we analyze the impact of ECLIPSE (Evaluating the Climate and Air Quality Impacts of Short-Lived Pollutants) future emissions scenarios representative of current legislation (CLE) and maximum technically feasible emissions reductions (MFR) on surface ozone (O3) concentrations over China in the 2030s and 2050s, in the context of a changing climate. We use a suite of simulations performed with the NOAA Geophysical Fluid Dynamics Laboratory's AM3 global chemistry-climate model. To estimate the impact of climate change in isolation on Chinese air quality, we hold emissions of air pollutants including O3 precursors fixed at 2015 levels but allow climate (global sea surface temperatures and sea ice cover) to change according to decadal averages for the years 2026-2035 and 2046-2055 from a three-member ensemble of GFDL-CM3 simulations under the RCP8.5 high warming scenario. Evaluation of the present-day simulation (2015 CLE) with observations from 1497 chiefly urban air quality monitoring stations shows that simulated surface O3 is positively biased by 26 ppb on average over the domain of China. Previous studies, however, have shown that the modeled ozone response to changes in NOx emissions over the Eastern United States mirrors the magnitude and structure of observed changes in maximum daily average 8-hour (MDA8) O3 distributions. Therefore, we use the model's simulated changes for the 2030s and 2050s to project changes in policy-relevant MDA8 O3 concentrations. We find an overall increase in MDA8 O3 for CLE scenarios in which emissions of NOx precursors are projected to increase, and under MFR scenarios, an overall decrease, with the highest changes occurring in summertime for both 2030 and 2050 MFR. Under climate change alone, the model simulates a mean summertime decrease of 1.3 ppb and wintertime increase of 3.3 ppb by 2050. Adjustment of the observed site-level MDA8 O3 distribution to reflect regionally interpolated projected changes from AM3 allows us to examine changes in the number of days in exceedance of MDA8 O3 Level I (50 ppb) and Level II (80 ppb) Chinese national ambient air quality standards.

Antarctic Ocean Nutrient Conditions During the Last Two Glacial Cycles

NASA Astrophysics Data System (ADS)

Studer, A.; Sigman, D. M.; Martinez-Garcia, A.; Benz, V.; Winckler, G.; Kuhn, G.; Esper, O.; Lamy, F.; Jaccard, S.; Wacker, L.; Oleynik, S.; Gersonde, R.; Haug, G. H.

2014-12-01

The high concentration of the major nutrients nitrate and phosphate in the Antarctic Zone of the Southern Ocean dictates the nature of Southern Ocean ecosystems and permits these nutrients to be carried from the deep ocean into the nutrient-limited low latitudes. Incomplete nutrient consumption in the Antarctic also allows the leakage of deeply sequestered carbon dioxide (CO2) back to the atmosphere, and changes in this leakage may have driven glacial/interglacial cycles in atmospheric CO2. In a sediment core from the Pacific sector of the Antarctic Ocean, we report diatom-bound N isotope (δ15Ndb) records for total recoverable diatoms and two assemblages of diatom species. These data indicate tight coupling between the degree of nitrate consumption and Antarctic climate across the last two glacial cycles, with δ15Ndb (and thus the degree of nitrate consumption) increasing at each major Antarctic cooling event. Measurements in the same sediment core indicate that export production was reduced during ice ages, pointing to an ice age reduction in the supply of deep ocean-sourced nitrate to the Antarctic Ocean surface. The reduced export production of peak ice ages also implies a weaker winter-to-summer decline (i.e. reduced seasonality) in mixed layer nitrate concentration, providing a plausible explanation for an observed reduction in the inter-assemblage δ15Ndb difference during these coldest times. Despite the weak summertime productivity, the reduction in wintertime nitrate supply from deep waters left the Antarctic mixed layer with a low nitrate concentration, and this wintertime change also would have reduced the outgassing of CO2. Relief of light limitation fails to explain the intermediate degree of nitrate consumption that characterizes early glacial conditions, as improved light limitation coincident with reduced nitrate supply would drive nitrate consumption to completion. Thus, the data favor iron availability as the dominant control on annual Antarctic Ocean export production over glacial cycles.

Extreme Precipitation and Emergency Room Visits for Influenza in Massachusetts: A Case-Crossover Analysis

EPA Science Inventory

BACKGROUND: Influenza peaks during the wintertime in temperate regions and during the annual rainy season in tropical regions – however reasons for the observed differences in disease ecology are poorly understood. We hypothesize that episodes of extreme precipitation also result...

RESULTS FROM EXPOSURE MONITORING PERFORMED DURING THE 1997 BALTIMORE PM PILOT STUDY

EPA Science Inventory

An eighteen day winter-time ambient and personal exposure monitoring study of particulate matter (PM) was conducted as part of an.integrated epidemiological-exposure pilot study of an aged population. Goals of the study were to determine the feasibility of performing active per...

IRIS Toxicological Review and Summary Documents for Methyl Tert-Butyl Ether (MTBE)

EPA Science Inventory

MTBE is a volatile organic chemical used to oxygenate gasoline. Oxygenated gasoline improves the exhaust emissions from gasoline engines. Since 1992 it has been used to comply with the Federal Reformulated Gasoline (begun in 1995) and Wintertime Oxygenated Fuel (begun in 1992) p...

Earth Observation during STS-113

NASA Image and Video Library

2002-12-07

STS113-332-030 (14 December 2002) --- The STS-113 crewmembers used a 35mm still camera to record this image of Mt. Etna Volcano erupting on the island of Sicily. The south-looking oblique sunset view shows snowy, winter-time Mt. Etna with a brown smutty ash plume.

Calculating surface ocean pCO2 from biogeochemical Argo floats equipped with pH: An uncertainty analysis

NASA Astrophysics Data System (ADS)

Williams, N. L.; Juranek, L. W.; Feely, R. A.; Johnson, K. S.; Sarmiento, J. L.; Talley, L. D.; Dickson, A. G.; Gray, A. R.; Wanninkhof, R.; Russell, J. L.; Riser, S. C.; Takeshita, Y.

2017-03-01

More than 74 biogeochemical profiling floats that measure water column pH, oxygen, nitrate, fluorescence, and backscattering at 10 day intervals have been deployed throughout the Southern Ocean. Calculating the surface ocean partial pressure of carbon dioxide (pCO2sw) from float pH has uncertainty contributions from the pH sensor, the alkalinity estimate, and carbonate system equilibrium constants, resulting in a relative standard uncertainty in pCO2sw of 2.7% (or 11 µatm at pCO2sw of 400 µatm). The calculated pCO2sw from several floats spanning a range of oceanographic regimes are compared to existing climatologies. In some locations, such as the subantarctic zone, the float data closely match the climatologies, but in the polar Antarctic zone significantly higher pCO2sw are calculated in the wintertime implying a greater air-sea CO2 efflux estimate. Our results based on four representative floats suggest that despite their uncertainty relative to direct measurements, the float data can be used to improve estimates for air-sea carbon flux, as well as to increase knowledge of spatial, seasonal, and interannual variability in this flux.

Convection and the seeding of the North Atlantic bloom

NASA Astrophysics Data System (ADS)

D'Asaro, Eric A.

Observations of vertical velocities in deep wintertime mixed layers using neutrally buoyant floats show that the convectively driven vertical velocities, roughly 1000 m per day, greatly exceed the sinking velocities of phytoplankton, 10 m or less per day. These velocities mix plankton effectively and uniformly across the convective layer and are therefore capable of returning those that have sunk to depth back into the euphotic zone. This mechanism cycles cells through the surface layer during the winter and provides a seed population for the spring bloom. A simple model of this mechanism applied to immortal phytoplankton in the subpolar Labrador Sea predicts that the seed population in early spring will be a few percent of the fall concentration if the plankton sink more slowly than the mean rate at which the surface well-mixed layer grows over the winter. Plankton that sink faster than this will mostly sink into the abyss with only a minute fraction remaining by spring. The shallower mixed layers of mid-latitudes are predicted to be much less effective at maintaining a seed population over the winter, limiting the ability of rapidly sinking cells to survive the winter.

An assessment of air pollution and its attributable mortality in Ulaanbaatar, Mongolia.

PubMed

Allen, Ryan W; Gombojav, Enkhjargal; Barkhasragchaa, Baldorj; Byambaa, Tsogtbaatar; Lkhasuren, Oyuntogos; Amram, Ofer; Takaro, Tim K; Janes, Craig R

2013-03-01

Epidemiologic studies have consistently reported associations between outdoor fine particulate matter (PM 2.5 ) air pollution and adverse health effects. Although Asia bears the majority of the public health burden from air pollution, few epidemiologic studies have been conducted outside of North America and Europe due in part to challenges in population exposure assessment. We assessed the feasibility of two current exposure assessment techniques, land use regression (LUR) modeling and mobile monitoring, and estimated the mortality attributable to air pollution in Ulaanbaatar, Mongolia. We developed LUR models for predicting wintertime spatial patterns of NO 2 and SO 2 based on 2-week passive Ogawa measurements at 37 locations and freely available geographic predictors. The models explained 74% and 78% of the variance in NO 2 and SO 2 , respectively. Land cover characteristics derived from satellite images were useful predictors of both pollutants. Mobile PM 2.5 monitoring with an integrating nephelometer also showed promise, capturing substantial spatial variation in PM 2.5 concentrations. The spatial patterns in SO 2 and PM, seasonal and diurnal patterns in PM 2.5 , and high wintertime PM 2.5 /PM 10 ratios were consistent with a major impact from coal and wood combustion in the city's low-income traditional housing (ger) areas. The annual average concentration of PM 2.5 measured at a centrally located government monitoring site was 75 μg/m 3 or more than seven times the World Health Organization's PM 2.5 air quality guideline, driven by a wintertime average concentration of 148 μg/m 3 . PM 2.5 concentrations measured in a traditional housing area were higher, with a wintertime mean PM 2.5 concentration of 250 μg/m 3 . We conservatively estimated that 29% (95% CI, 12-43%) of cardiopulmonary deaths and 40% (95% CI, 17-56%) of lung cancer deaths in the city are attributable to outdoor air pollution. These deaths correspond to nearly 10% of the city's total mortality, with estimates ranging to more than 13% of mortality under less conservative model assumptions. LUR models and mobile monitoring can be successfully implemented in developing country cities, thus cost-effectively improving exposure assessment for epidemiology and risk assessment. Air pollution represents a major threat to public health in Ulaanbaatar, Mongolia, and reducing home heating emissions in traditional housing areas should be the primary focus of air pollution control efforts.

Extreme cyclone events in the Arctic: Wintertime variability and trends

NASA Astrophysics Data System (ADS)

Rinke, A.; Maturilli, M.; Graham, R. M.; Matthes, H.; Handorf, D.; Cohen, L.; Hudson, S. R.; Moore, J. C.

2017-09-01

Typically 20-40 extreme cyclone events (sometimes called ‘weather bombs’) occur in the Arctic North Atlantic per winter season, with an increasing trend of 6 events/decade over 1979-2015, according to 6 hourly station data from Ny-Ålesund. This increased frequency of extreme cyclones is consistent with observed significant winter warming, indicating that the meridional heat and moisture transport they bring is a factor in rising temperatures in the region. The winter trend in extreme cyclones is dominated by a positive monthly trend of about 3-4 events/decade in November-December, due mainly to an increasing persistence of extreme cyclone events. A negative trend in January opposes this, while there is no significant trend in February. We relate the regional patterns of the trend in extreme cyclones to anomalously low sea-ice conditions in recent years, together with associated large-scale atmospheric circulation changes such as ‘blockinglike’ circulation patterns (e.g. Scandinavian blocking in December and Ural blocking during January-February).

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.

IMPACT OF AN UPDATED CARBON BOND MECHANISM ON PREDICTIONS FROM THE CMAQ MODELING SYSTEM: PRELIMINARY ASSESSMENT

EPA Science Inventory

An updated and expanded Carbon Bond mechanism (CB05) has been incorporated into the Community Multiscale Air Quality modeling system to more accurately simulate wintertime, pristine, and high altitude situations. The CB05 mechanism has nearly twice the number of reactions compare...

77 FR 9690 - Willamette Valley National Wildlife Refuge Complex, Corvallis, OR; Final Comprehensive...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-17

... sanctuary or for any other management purpose, for migratory birds * * * to conserve and protect migratory... program to provide forage for wintering Canada geese; Managing wetland habitats and providing sanctuary... area closed to wintertime public access to provide sanctuary during the wintering waterfowl season...

77 FR 75896 - Atlantic Highly Migratory Species; 2013 Atlantic Shark Commercial Fishing Season

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-26

... FMP, we established a shark research fishery to maintain time series data for stock assessments and to... time-series of wintertime abundance for shark species or collecting vital biological and regional data... the first time NMFS anticipates using the inseason adjustments. The October 2012 proposed rule...

Eocene Antarctic seasonality inferred from high-resolution stable isotope profiles of fossil bivalves and driftwood

NASA Astrophysics Data System (ADS)

Judd, E. J.; Ivany, L. C.; Miklus, N. M.; Uveges, B. T.; Junium, C. K.

2017-12-01

The Eocene Epoch was a time of large-scale global climate change, experiencing both the warmest temperatures of the Cenozoic and the onset of southern hemisphere glaciation. The record of average global temperatures throughout this transition is reasonably well constrained, however considerably less is known about the accompanying changes in seasonality. Seasonally resolved temperature data provide a wealth of information not readily available from mean annual temperature data alone. These data are particularly important in the climatically sensitive high latitudes, as they can elucidate the means by which climate changes and the conditions necessary for the growth of ice sheets. Several recent studies, however, have suggested the potential for monsoonal precipitation regimes in the early-middle Eocene high latitudes, which complicates interpretation of seasonally resolved oxygen isotope records in shallow nearshore marine settings. Seasonal precipitation and runoff could create a brackish, isotopically depleted lens in these environments, depleting summertime δ18Ocarb and thereby inflating the inferred mean and range of isotope-derived temperatures. Here, we assess intra-annual variations in temperature in shallow nearshore Antarctic waters during the middle and late Eocene, inferred from high-resolution oxygen isotope profiles from accretionary bivalves of the La Meseta Formation, Seymour Island, Antarctica. To address concerns related to precipitation and runoff, we also subsample exceptionally preserved fossil driftwood from within the formation and use seasonal differences in δ13Corg values to estimate the ratio of summertime to wintertime precipitation. Late Eocene oxygen isotope profiles exhibit strongly attenuated seasonal amplitudes and more enriched mean annual values in comparison with data from the middle Eocene. Preliminary fossil wood data are not indicative of a strongly seasonal precipitation regime, implying that intra-annual variation in oxygen isotope profiles dominantly reflects changes in temperature. Collectively, these results indicate that the late Eocene was cooler and dramatically less seasonal than the middle Eocene and suggest that high latitude Eocene cooling was achieved primarily through a preferential decrease in summertime temperatures.

Trends in snowfall versus rainfall in the western United States

USGS Publications Warehouse

Knowles, N.; Dettinger, M.D.; Cayan, D.R.

2006-01-01

The water resources of the western United States depend heavily on snowpack to store part of the wintertime precipitation into the drier summer months. A well-documented shift toward earlier runoff in recent decades has been attributed to 1) more precipitation falling as rain instead of snow and 2) earlier snowmelt. The present study addresses the former, documenting a regional trend toward smaller ratios of winter-total snowfall water equivalent (SFE) to winter-total precipitation (P) during the period 1949-2004. The trends toward reduce d SFE are a response to warming across the region, with the most significant reductions occurring where winter wet-day minimum temperatures, averaged over the study period, were warmer than -5??C. Most SFE reductions were associated with winter wet-day temperature increases between 0?? and +3??C over the study period. Warmings larger than this occurred mainly at sites where the mean temperatures were cool enough that the precipitation form was less susceptible to warming trends. The trends toward reduced SFE/P ratios w ere most pronounced in March regionwide and in January near the West Coast, corresponding, to widespread warming in these months. While mean temperatures in March were sufficiently high to allow the warming, trend to produce SFE/P declines across the study region, mean January temperatures were cooler. with the result that January SFE/P impacts were restricted to the lower elevations near the West Coast. Extending the analysis back to 1920 sho ws that although the trends presented here may be partially attributable to interdecadal climate variability associated with the Pacific decadal oscillation. they also appear to result from still longer-term climate shifts.

Physical Processes Controlling the Spatial Distributions of Relative Humidity in the Tropical Tropopause Layer Over the Pacific

NASA Technical Reports Server (NTRS)

Jensen, Eric J.; Thornberry, Troy D.; Rollins, Andrew W.; Ueyama, Rei; Pfister, Leonhard; Bui, Thaopaul; Diskin, Glenn S.; Digangi, Joshua P.; Hintsa, Eric; Gao, Ru-Shan;

Aircraft NOx and O3 measurements during wintertime temperature inversions in Salt Lake City, Utah

NASA Astrophysics Data System (ADS)

Womack, C.; Fibiger, D. L.; McDuffie, E. E.; Franchin, A.; Goldberger, L.; Moravek, A.; Middlebrook, A. M.; Thornton, J. A.; Murphy, J. G.; Baasandorj, M.; Brown, S. S.

2017-12-01

The topography of northern Utah results in several multi-day persistent cold-air pools (PCAPs) each winter, during which a temperature inversion prevents the mix-out of anthropogenic emissions. Pollutant levels rise over the course of several days, resulting in particulate matter (PM2.5) levels exceeding the US National Ambient Air Quality Standard of 35 µg/m3, often reaching 60-70 µg/m3 or higher. However, there is significant variability within individual valleys, whose emissions are predominately urban (as in Salt Lake City Valley), agricultural (as in Cache Valley), or a combination of the two. The Utah Winter Fine Particulate Matter Study (UWFPS 2017) was a ground- and aircraft-based field campaign that took place in Jan-Feb 2017 with the aim of better characterizing the complex chemistry involved in the buildup of PM2.5. On board the NOAA Twin Otter aircraft was a cavity ringdown instrument for measuring nitrogen oxides and ozone, an I- CIMS for gas phase oxidized reactive nitrogen, an AMS that measured particulate phase nitrate, and a mid-infrared absorption instrument for NH3. We report vertical and horizontal distributions of NOx, NOy, and O3, and their variation with meteorological conditions and time of day, in the urban and rural valleys of northern Utah.

New climate change scenarios for the Netherlands.

PubMed

van den Hurk, B; Tank, A K; Lenderink, G; Ulden, A van; Oldenborgh, G J van; Katsman, C; Brink, H van den; Keller, F; Bessembinder, J; Burgers, G; Komen, G; Hazeleger, W; Drijfhout, S

2007-01-01

A new set of climate change scenarios for 2050 for the Netherlands was produced recently. The scenarios span a wide range of possible future climate conditions, and include climate variables that are of interest to a broad user community. The scenario values are constructed by combining output from an ensemble of recent General Climate Model (GCM) simulations, Regional Climate Model (RCM) output, meteorological observations and a touch of expert judgment. For temperature, precipitation, potential evaporation and wind four scenarios are constructed, encompassing ranges of both global mean temperature rise in 2050 and the strength of the response of the dominant atmospheric circulation in the area of interest to global warming. For this particular area, wintertime precipitation is seen to increase between 3.5 and 7% per degree global warming, but mean summertime precipitation shows opposite signs depending on the assumed response of the circulation regime. Annual maximum daily mean wind speed shows small changes compared to the observed (natural) variability of this variable. Sea level rise in the North Sea in 2100 ranges between 35 and 85 cm. Preliminary assessment of the impact of the new scenarios on water management and coastal defence policies indicate that particularly dry summer scenarios and increased intensity of extreme daily precipitation deserves additional attention in the near future.

D/H Ratios From Sierra Nevada Varved Lake Sediments Record Decadal Hydroclimate Variability During The Medieval Period

NASA Astrophysics Data System (ADS)

Roach, L. D.; Cayan, D. R.; Sessions, A. L.; Charles, C. D.; Anderson, R. S.

2009-12-01

Assessment of the risks of persistent drought requires multiple realizations of decadal and centennial scale hydroclimate variability that extend beyond the relatively short period of instrumental record. Much remains to be learned about the so called “mega droughts” in the Sierra Nevada Mountains, where various lines of evidence point toward the occurrence of severe, decades-long droughts during Medieval times, approximately 900-1400 AD. Here we present a continuous, decadal scale record of hydroclimate variability in the Sierra Nevada Mountains that extends through the heart of the purported Medieval mega droughts. Previous work on the stable hydrogen isotope (D/H) ratios of refractory plant lipid compounds stored in lake sediments demonstrated that these compounds reflect the D/H values of lake water and/or shallow ground water--reservoirs both fed by local precipitation. Lake sediment D/H can therefore reflect the processes that determine D/H of precipitation, including temperature, humidity and moisture source. We have measured D/H of aquatic and terrestrial plant fatty acids extracted from a suite of sediment cores collected at Swamp Lake (elevation: 1554m), in Yosemite National Park, along the Sierra Nevada crest. Measurements with biennial resolution were made for two time periods: the 20th century and the 13th-15th centuries. D/H fluctuations in 20th century sediment contain relatively strong decadal structure. Comparison with instrumentally recorded climate variability reveals that lower D/H concentrations are associated with years of higher than normal annual precipitation, cooler than normal wintertime temperatures, and positive April 1 Snow Water Equivalent (SWE) anomalies throughout the Sierra Nevada, (and conversely for elevated D/H concentrations). The range of variability is approximately 50‰. These associations may be driven by the variable mass-balance impact of evaporation on the isotopic composition of lake water and shallow groundwater in the Swamp Lake watershed, depending on the extent to which these reservoirs are replenished seasonally by wintertime precipitation. Throughout the Medieval period, we observe significant (>30‰), reproducible D/H variability that also fluctuates on multi-year to decadal time scales, with mean values falling within the same range as those recorded over the 20th century. Strong covariance among the aquatic and terrestrial plant fatty acids analyzed, along with the mean values, lends confidence that primary isotopic signatures have been retained. These results can therefore be compared directly to other measures of hydroclimate variability throughout the last millennium, offering a unique new perspective on the mega-drought intervals.

Evaluating the relationship between biomass, percent groundcover and remote sensing indices across six winter cover crop fields in Maryland, United States

NASA Astrophysics Data System (ADS)

Prabhakara, Kusuma; Hively, W. Dean; McCarty, Gregory W.

2015-07-01

Winter cover crops are an essential part of managing nutrient and sediment losses from agricultural lands. Cover crops lessen sedimentation by reducing erosion, and the accumulation of nitrogen in aboveground biomass results in reduced nutrient runoff. Winter cover crops are planted in the fall and are usually terminated in early spring, making them susceptible to senescence, frost burn, and leaf yellowing due to wintertime conditions. This study sought to determine to what extent remote sensing indices are capable of accurately estimating the percent groundcover and biomass of winter cover crops, and to analyze under what critical ranges these relationships are strong and under which conditions they break down. Cover crop growth on six fields planted to barley, rye, ryegrass, triticale or wheat was measured over the 2012-2013 winter growing season. Data collection included spectral reflectance measurements, aboveground biomass, and percent groundcover. Ten vegetation indices were evaluated using surface reflectance data from a 16-band CROPSCAN sensor. Restricting analysis to sampling dates before the onset of prolonged freezing temperatures and leaf yellowing resulted in increased estimation accuracy. There was a strong relationship between the normalized difference vegetation index (NDVI) and percent groundcover (r2 = 0.93) suggesting that date restrictions effectively eliminate yellowing vegetation from analysis. The triangular vegetation index (TVI) was most accurate in estimating high ranges of biomass (r2 = 0.86), while NDVI did not experience a clustering of values in the low and medium biomass ranges but saturated in the higher range (>1500 kg/ha). The results of this study show that accounting for index saturation, senescence, and frost burn on leaves can greatly increase the accuracy of estimates of percent groundcover and biomass for winter cover crops.

Evaluating the relationship between biomass, percent groundcover and remote sensing indices across six winter cover crop fields in Maryland, United States

USGS Publications Warehouse

Prabhakara, Kusuma; Hively, W. Dean; McCarty, Greg W.

2015-01-01

Winter cover crops are an essential part of managing nutrient and sediment losses from agricultural lands. Cover crops lessen sedimentation by reducing erosion, and the accumulation of nitrogen in aboveground biomass results in reduced nutrient runoff. Winter cover crops are planted in the fall and are usually terminated in early spring, making them susceptible to senescence, frost burn, and leaf yellowing due to wintertime conditions. This study sought to determine to what extent remote sensing indices are capable of accurately estimating the percent groundcover and biomass of winter cover crops, and to analyze under what critical ranges these relationships are strong and under which conditions they break down. Cover crop growth on six fields planted to barley, rye, ryegrass, triticale or wheat was measured over the 2012–2013 winter growing season. Data collection included spectral reflectance measurements, aboveground biomass, and percent groundcover. Ten vegetation indices were evaluated using surface reflectance data from a 16-band CROPSCAN sensor. Restricting analysis to sampling dates before the onset of prolonged freezing temperatures and leaf yellowing resulted in increased estimation accuracy. There was a strong relationship between the normalized difference vegetation index (NDVI) and percent groundcover (r2 = 0.93) suggesting that date restrictions effectively eliminate yellowing vegetation from analysis. The triangular vegetation index (TVI) was most accurate in estimating high ranges of biomass (r2 = 0.86), while NDVI did not experience a clustering of values in the low and medium biomass ranges but saturated in the higher range (>1500 kg/ha). The results of this study show that accounting for index saturation, senescence, and frost burn on leaves can greatly increase the accuracy of estimates of percent groundcover and biomass for winter cover crops.

Characterization of Arctic elemental carbon in Barrow, AK using radiocarbon source apportionment

NASA Astrophysics Data System (ADS)

Barrett, T. E.; Usenko, S.; Robinson, E. M.; Sheesley, R. J.

2013-12-01

Currently, the Arctic is one of the fastest warming regions on earth with surface temperatures increasing at a rate nearly double the global mean over recent decades. Despite the fact that atmospheric concentrations of elemental carbon (EC) are lower in the Arctic than in lower latitudes, deposition of EC on snow and ice may exacerbate regional warming by simultaneously decreasing albedo and increasing melt rates. Due to the intensifying Arctic oil exploration in areas such as the Beaufort and Chukchi seas, the impact of new emission sources such as heavy fuel and heavy diesel combustion on regional carbon needs to be assessed. The first step in developing mitigation strategies for reducing current and future EC emissions in the Arctic is to determine emission source contributions. This study aims to determine the relative contributions of fossil fuel and biomass combustion and to identify major source regions of EC to the Arctic. Radiocarbon analysis of both total organic carbon (TOC) and EC combined with organic tracer and back trajectory analysis has been applied to a set of wintertime coarse particulate matter (PM10) samples from Barrow, AK. Preliminary apportionment for January 2013 indicates roughly half of TOC is from biogenic/biomass burning emissions and one third of EC is due to biomass burning emissions. The radiocarbon results will be combined with organic tracer analysis (polycyclic aromatic hydrocarbons, petroleum biomarkers and normal alkanes), increasing the specificity of the relative contribution of both the fossil and modern (biogenic/biomass burning) carbon emission sources. This research represents the first reported radiocarbon values for Arctic EC, providing highly conclusive source apportionment prior to the influence of increased drilling operations and ship traffic in the Beaufort and Chukchi seas.

Arctic lead detection using a waveform unmixing algorithm from CryoSat-2 data

NASA Astrophysics Data System (ADS)

Lee, S.; Im, J.

2016-12-01

Arctic areas consist of ice floes, leads, and polynyas. While leads and polynyas account for small parts in the Arctic Ocean, they play a key role in exchanging heat flux, moisture, and momentum between the atmosphere and ocean in wintertime because of their huge temperature difference In this study, a linear waveform unmixing approach was proposed to detect lead fraction. CryoSat-2 waveforms for pure leads, sea ice, and ocean were used as end-members based on visual interpretation of MODIS images coincident with CryoSat-2 data. The unmixing model produced lead, sea ice, and ocean abundances and a threshold (> 0.7) was applied to make a binary classification between lead and sea ice. The unmixing model produced better results than the existing models in the literature, which are based on simple thresholding approaches. The results were also comparable with our previous research using machine learning based models (i.e., decision trees and random forest). A monthly lead fraction was calculated, dividing the number of detected leads by the total number of measurements. The lead fraction around Beaufort Sea and Fram strait was high due to the anti-cyclonic rotation of Beaufort Gyre and the outflows of sea ice to the Atlantic. The lead fraction maps produced in this study were matched well with monthly lead fraction maps in the literature. The areas with thin sea ice identified from our previous research correspond to the high lead fraction areas in the present study. Furthermore, sea ice roughness from ASCAT scatterometer was compared to a lead fraction map to see the relationship between surface roughness and lead distribution.

Diagnosis of extratropical variability in seasonal integrations of the ECMWF model

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

Ferranti, L.; Molteni, F.; Brankovic, C.

1994-06-01

Properties of the general circulation simulated by the ECMWF model are discussed using a set of seasonal integrations at T63 resolution. For each season, over the period of 5 years, 1986-1990, three integrations initiated on consecutive days were run with prescribed observed sea surface temperature (SST). This paper presents a series of diagnostics of extratropical variability in the model, with particular emphasis on the northern winter. Time-filtered maps of variability indicate that in this season there is insufficient storm track activity penetrating into the Eurasian continent. Related to this the maximum of lower-frequency variability for northern spring are more realistic.more » Blocking is defined objectively in terms of the geostrophic wind at 500 mb. Consistent with the low-frequency transience, in the Euro-Atlantic sector the position of maximum blocking in the model is displaced eastward. The composite structure of blocks over the Pacific is realistic, though their frequency is severely underestimated at all times of year. Shortcomings in the simulated wintertime general circulation were also revealed by studying the projection of 5-day mean fields onto empirical orthogonal functions (EOFs) of the observed flow. The largest differences were apparent for statistics of EOFs of the zonal mean flow. Analysis of weather regime activity, defined from the EOFs, suggested that regimes with positive PNA index were overpopulated, while the negative PNA regimes were underpopulated. A further comparison between observed and modeled low-frequency variance revealed that underestimation of low-frequency variability occurs along the same axes that explain most of the spatial structure of the error in the mean field, suggesting a common dynamical origin for these two aspects of the systematic error. 17 refs., 17 figs., 4 tabs.« less

Emissions from oil and natural gas operations in northeastern Utah

NASA Astrophysics Data System (ADS)

Petron, G.; Kofler, J. D.; Frost, G. J.; Miller, B. R.; Edwards, P. M.; Dube, W. P.; Montzka, S. A.; Helmig, D.; Hueber, J.; Karion, A.; Sweeney, C.; Conley, S. A.; Brown, S. S.; Geiger, F.; Warneke, C.; Martin, R. S.; Andrews, A. E.; Dlugokencky, E. J.; Lang, P. M.; Trainer, M.; Hardesty, R.; Schnell, R. C.; Tans, P. P.

2012-12-01

The Uintah oil and natural gas Basin in Northeastern Utah experienced several days of high ozone levels in early 2011 during cold temperature inversions. To study the chemical and meteorological processes leading to these wintertime ozone pollution events, the State of Utah, EPA region 8 and oil and gas operators pulled together a multi-agency research team, including NOAA ESRL/CIRES scientists. The data gathering took place between January 15 and February 29, 2012.To document the chemical signature of various sources in the Basin, we outfitted a passenger van with in-situ analyzers (Picarro: CH4, CO2, CO, H2O, 13CH4; NOxCaRD: NO, NOx, 2B & NOxCaRD: O3) meteorological sensors, GPS units, discrete flask sampling apparatus, as well as a data logging and "real-time" in-situ data visualization system. The instrumented van, called Mobile Lab, also hosted a KIT Proton Transfer Reaction Mass Spectrometer (suite of VOCs in situ measurements) for part of the campaign. For close to a month, the Mobile Lab traveled the roads of the oil and gas field, documenting ambient levels of several tracers. Close to 180 valid air samples were collected in February by the Mobile Lab for future analysis in the NOAA and CU/INSTAAR labs in Boulder. At the same time as the surface effort was going on, an instrumented light aircraft conducted transects over the Basin collecting air samples mostly in the boundary layer and measuring in situ the following species CH4, CO2, NO2, O3. We will present some of the data collected by the Mobile Lab and the aircraft and discuss analysis results.

Influence of meteorological conditions on RSV infection in Portugal

NASA Astrophysics Data System (ADS)

Oliveira-Santos, M.; Santos, J. A.; Soares, J.; Dias, A.; Quaresma, M.

2016-12-01

Acute viral bronchiolitis is a common cause for infant hospital admissions. Of all etiological agents, respiratory syncytial virus (RSV) is commonly the most frequent. The present study assesses relationships between atmospheric factors and RSV infections in under 3-year-old patients admitted to the Inpatient Paediatric Service of Vila Real (North of Portugal). For this purpose, (1) clinical files of children admitted with a diagnosis of acute bronchiolitis from September 2005 to December 2015 (>10 years) were scrutinised and (2) local daily temperature/precipitation series, as well as six weather types controlling meteorological conditions in Portugal, were used. Fifty-five percent of all 770 admitted children were effectively infected with a given virus, whilst 48 % (367) were RSV+, i.e. 87 % of virus-infected children were RSV+. The bulk of incidence is verified in the first year of age (82 %, 302), slightly higher in males. RSV outbreaks are typically from December to March, but important inter-annual variability is found in both magnitude and shape. Although no clear connections were found between monthly temperatures/precipitation and RSV outbreaks apart from seasonality, a linkage to wintertime cold spells is apparent on a daily basis. Anomalously low minimum temperatures from the day of admittance back to 10 days before are observed. This relationship is supported by anomalously high occurrences of the E and AA weather types over the same period, which usually trigger dry and cold weather. These findings highlight some predictability in the RSV occurrences, revealing potential for modelling and risk assessments.

The influence of a heat and moisture exchanger on tracheal climate in a cold environment.

PubMed

Zuur, J Karel; Muller, Sara H; Vincent, Andrew; Sinaasappel, Michiel; de Jongh, Frans H C; Hilgers, Frans J M

2009-09-01

The incidence of pulmonary complaints, severe tracheitis and lung function deterioration is increased during wintertime in laryngectomized individuals. We analyzed how a heat and moisture exchanger (HME) performs in cold and dry ambient circumstances, and how its efficiency in this environmental climate might be improved. Randomized crossover. Intra-tracheal temperature and humidity were measured in 10 laryngectomized patients with and without HME, in a cold (mean, 4.7 degrees C) and dry (mean, 4.5 mgH2O/L) room. Presence of an HME causes the intra-tracheal mean humidity minima and maxima to increase with 4.2 mgH2O/L (95%CI: 3.3-5.0 mgH2O/L; p<0.001) and 2.4 mgH2O/L (95%CI: 1.7-3.1 mgH2O/L; p<0.001), respectively. The intra-tracheal mean temperature minima and maxima increased with 3.9 degrees C (95%CI: 2.7-5.1 degrees C; p<0.001) and 1.2 degrees C (95%CI: 0.8-1.2 degrees C; p<0.001), respectively. In the majority of patients, the calculated relative humidity values appear to reach well above 100% during inspiration. In a cold environment, presence of an HME significantly increases both inspiratory and expiratory temperature and humidity values. Relative humidity calculations suggest the formation of condense droplets during inspiration. To further increase its effectiveness, improvement of the HME's thermal capacity should be aimed for.

Investigating Lateral Boundary Forcing of Weather Research and Forecasting (WRF) Model Forecasts for Artillery Mission Support

DTIC Science & Technology

2013-01-01

the internal variability, such as the storm track or rainfall pattern (8). Arguments have emerged for the use of small domains in certain cases as...Sensitivity experiments were performed with the WRF-ARW over Meiningen, Germany for two strong wintertime extratropical cyclones. These cases were chosen

Stratospheric HTO perturbations 1980-1983

NASA Astrophysics Data System (ADS)

Mason, A. S.

1985-02-01

Three perturbations of the stratospheric tritiated water burden have occurred. An atmospheric nuclear detonation in 1980 injected about 2.1 MCi. The massive eruptions of the volcano El Chichon may have contributed to a doubling of the removal rate in 1982. An unusually large wintertime exchange with the upper stratosphere may have occurred between 1982 and 1983.

75 FR 45209 - Federal Implementation Plans To Reduce Interstate Transport of Fine Particulate Matter and Ozone

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-02

... 1. What is the source of EPA's authority for this action? 2. What air quality problems does this... non-attainment or maintenance problems, the remaining exceedances occur almost entirely in the winter... to which this wintertime problem is caused by emissions transported from upwind states. Further study...

ASSESSMENT OF THE WINTER-TIME PERFORMANCE OF DEVELOPMENTAL PARTICULATE MATTER FORECASTS WITH THE ETA-CMAQ MODELING SYSTEM

EPA Science Inventory

It is desirable for local air quality agencies to accurately forecast tropospheric PM_2.5 concentrations to alert the sensitive population of the onset, severity and duration of unhealthy air, and to encourage the public and industry to reduce emissions-producing activi...

LABORATORY AND FIELD EVALUATION OF CRYSTALLIZED DOW 704 OIL ON THE PERFORMANCE OF THE PM2.5 WINS FRACTIONATOR

EPA Science Inventory

Subsequent to the PM2.5 FRM's 1997 promulgation, technicians at the CT Dept. of Env. Protection observed that the DOW 704 diffusion oil used in the method's WINS fractionator would occasionally crystallize during field use - particularly under wintertime conditions. While the f...

DETERMINING COARSE PARTICULATE MATTER CONCENTRATIONS: A PERFORMANCE EVALUATION OF CANDIDATE METHODOLOGIES UNDER WINTERTIME CONDITIONS

EPA Science Inventory

The main objective of this study is to evaluate the performance of sampling methods for potential use as a Federal Reference Method (FRM) capable of providing an estimate of coarse particle (PMc: particulate matter with an aerodynamic diameter between 2.5 um and 10 um) mass con...

Dependence of Lunar Tide of the Equatorial Electrojet on the Wintertime Polar Vortex, Solar Flux, and QBO

NASA Astrophysics Data System (ADS)

Siddiqui, T. A.; Yamazaki, Y.; Stolle, C.; Lühr, H.; Matzka, J.; Maute, A.; Pedatella, N.

2018-05-01

The lower atmospheric forcing effects on the ionosphere are particularly evident during extreme meteorological events known as sudden stratospheric warmings (SSWs). During SSWs, the polar stratosphere and ionosphere, two distant atmospheric regions, are coupled through the SSW-induced modulation of atmospheric migrating and nonmigrating tides. The changes in the migrating semidiurnal solar and lunar tides are the major source of ionospheric variabilities during SSWs. In this study, we use 55 years of ground-magnetometer observations to investigate the composite characteristics of the lunar tide of the equatorial electrojet (EEJ) during SSWs. These long-term observations allow us to capture the EEJ lunar tidal response to the SSWs in a statistical sense. Further, we examine the influence of solar flux conditions and the phases of quasi-biennial oscillation (QBO) on the lunar tide and find that the QBO phases and solar flux conditions modulate the EEJ lunar tidal response during SSWs in a similar way as they modulate the wintertime Arctic polar vortex. This work provides first evidence of modulation of the EEJ lunar tide due to QBO.

Ionospheric acoustic and gravity wave activity above low-latitude thunderstorms

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

Lay, Erin Hoffmann

In this report, we study the correlation between thunderstorm activity and ionospheric gravity and acoustic waves in the low-latitude ionosphere. We use ionospheric total electron content (TEC) measurements from the Low Latitude Ionospheric Sensor Network (LISN) and lightning measurements from the World- Wide Lightning Location Network (WWLLN). We find that ionospheric acoustic waves show a strong diurnal pattern in summer, peaking in the pre-midnight time period. However, the peak magnitude does not correspond to thunderstorm area, and the peak time is significantly after the peak in thunderstorm activity. Wintertime acoustic wave activity has no discernable pattern in these data. Themore » coverage area of ionospheric gravity waves in the summer was found to increase with increasing thunderstorm activity. Wintertime gravity wave activity has an observable diurnal pattern unrelated to thunderstorm activity. These findings show that while thunderstorms are not the only, or dominant source of ionospheric perturbations at low-latitudes, they do have an observable effect on gravity wave activity and could be influential in acoustic wave activity.« less

Double-diffusive layers in the Adriatic Sea

NASA Astrophysics Data System (ADS)

Carniel, Sandro; Sclavo, Mauro; Kantha, Lakshmi; Prandke, Hartmut

2008-01-01

A microstructure profiler was deployed to make turbulence measurements in the upper layers of the southern Adriatic Sea in the Mediterranean during the Naval Research Laboratory (NRL) DART06A (Dynamics of the Adriatic in Real Time) winter cruise in March 2006. Measurements in the Po river plume along the Italian coast near the Gargano promontory displayed classic double-diffusive layers and staircase structures resulting from the relatively colder and fresher wintertime Po river outflow water masses overlying warmer and more saline water masses from the Adriatic Sea. We report here on the water mass and turbulence structure measurements made both in the double-diffusive interfaces and the adjoining mixed layers in the water columns undergoing double-diffusive convection (DDC). This dataset augments the relatively sparse observations available hitherto on the diffusive layer type of DDC. Measured turbulence diffusivities are consistent with those from earlier theoretical and experimental formulations, suggesting that the wintertime Po river plume is a convenient and easily accessible place to study double diffusive convective processes of importance to mixing in the interior of many regions of the global oceans.

Response of the North Pacific Oscillation to global warming in the models of the Intergovernmental Panel on Climate Change Fourth Assessment Report

NASA Astrophysics Data System (ADS)

Chen, Zheng; Gan, Bolan; Wu, Lixin

2017-09-01

Based on 22 of the climate models from phase 3 of the Coupled Model Intercomparison Project, we investigate the ability of the models to reproduce the spatiotemporal features of the wintertime North Pacific Oscillation (NPO), which is the second most important factor determining the wintertime sea level pressure field in simulations of the pre-industrial control climate, and evaluate the NPO response to the future most reasonable global warming scenario (the A1B scenario). We reveal that while most models simulate the geographic distribution and amplitude of the NPO pattern satisfactorily, only 13 models capture both features well. However, the temporal variability of the simulated NPO could not be significantly correlated with the observations. Further analysis indicates the weakened NPO intensity for a scenario of strong global warming is attributable to the reduced lower-tropospheric baroclinicity at mid-latitudes, which is anticipated to disrupt large-scale and low-frequency atmospheric variability, resulting in the diminished transfer of energy to the NPO, together with its northward shift.

Modeling winter ozone episodes near oil and natural gas fields in Wyoming

NASA Astrophysics Data System (ADS)

Wu, Yuling; Rappenglück, Bernhard; Pour-Biazar, Arastoo; Field, Robert A.; Soltis, Jeff

2017-04-01

Wintertime ozone episodes have been reported in the oil and natural gas (O&NG) producing fields in Uintah Basin, Utah and the Upper Green River Basin (UGRB) in Wyoming in recent years. High concentrations of ozone precursors facilitated by favorable meteorological conditions, including low wind and shallow boundary layer (BL), were found in these episodes, although the exact roles of these precursor species in different O&NG fields are to be determined. Meanwhile, snow cover is also found to play an important role in these winter ozone episodes as the cold snow covered surface enhances the inversion, further limits the BL and the high snow albedo greatly boosts photolysis reactions that are closely related to ozone chemistry. In this study, we utilize model simulation to explore the role of chemical compositions, in terms of different VOC groups and NOx, and that of the enhanced photolysis due to snow cover in the UGRB ozone episodes in the late winter of 2011.

Winter crop CO2 uptake inferred from CONTRAIL measurements over Delhi, India

NASA Astrophysics Data System (ADS)

Umezawa, Taku; Niwa, Yosuke; Sawa, Yousuke; Machida, Toshinobu; Matsueda, Hidekazu

2016-11-01

Recent studies have shown the impact of expanding agricultural activities on atmospheric CO2 variations and the global carbon cycle. In this study, we show clear evidence of the measureable impact of Indian wintertime crops (mainly wheat) on the regional carbon budget using high-frequency atmospheric CO2 measurements by Comprehensive Observation Network for Trace gases by Airliners (CONTRAIL) over Delhi; this phenomenon is not detected by the existing network of surface CO2 sites. While a general increase in the vertical profiles of CO2 toward the ground in the boundary layer was observed throughout December-April, we frequently observed sharp decreases below 2 km during January-March. Seasonal circulations during these 3 months indicated influences from neighboring croplands (with patchy urban areas) located upwind. We conclude that the observed CO2 decrease is attributable to active uptake by the crops grown in winter and that the uptake exceeds in magnitude the urban CO2 emissions from the Delhi metropolitan area.

Airborne Observations of Urban-Derived Water Vapor and Potential Impacts on Chemistry and Clouds

NASA Astrophysics Data System (ADS)

Salmon, O. E.; Shepson, P. B.; Grundman, R. M., II; Stirm, B. H.; Ren, X.; Dickerson, R. R.; Fuentes, J. D.

2015-12-01

Atmospheric conditions typical of wintertime, such as lower boundary layer heights and reduced turbulent mixing, provide a unique environment for anthropogenic pollutants to accumulate and react. Wintertime enhancements in water vapor (H2O) have been observed in urban areas, and are thought to result from fossil fuel combustion and urban heat island-induced evaporation. The contribution of urban-derived water vapor to the atmosphere has the potential to locally influence atmospheric chemistry and weather for the urban area and surrounding region due to interactions between H2O and other chemical species, aerosols, and clouds. Airborne observations of urban-derived H2O, carbon dioxide (CO2), methane, nitrogen dioxide (NO2), ozone, and aerosols were conducted from Purdue University's Airborne Laboratory for Atmospheric Research (ALAR) and the University of Maryland's (UMD) Twin Cessna research aircraft during the winter of 2015. Measurements were conducted as part of the collaborative airborne campaign, Wintertime INvestigation of Transport, Emissions, and Reactivity (WINTER), which investigated seasonal trends in anthropogenic emissions and reactivity in the Northeastern United States. ALAR and the UMD aircraft participated in mass balance experiments around Washington D.C.-Baltimore to determine total city emission rates of H2O and other greenhouse gases. Average enhancements in H2O mixing ratio of 0.048%, and up to 0.13%, were observed downwind of the urban centers on ten research flights. In some cases, downwind H2O concentrations clearly track CO2 and NO2 enhancements, suggesting a strong combustion signal. Analysis of Purdue and UMD data collected during the WINTER campaign shows an average urban-derived H2O contribution of 5.3%, and as much as 13%, to the local boundary layer from ten research flights flown in February and March of 2015. In this paper, we discuss the potential chemical and physical implications of these results.

Daily and peak 1 h indoor air pollution and driving factors in a rural Chinese village.

PubMed

Fischer, Susan L; Koshland, Catherine P

2007-05-01

We investigate wintertime indoor air quality and personal exposures to carbon monoxide (CO) in a rural village in Jilin province, where relatively homogeneous climatic and sociocultural factors facilitate investigation of household structural, fuel-related, and behavioral determinants of air pollution as well as relationships between different measures of air quality. Our time-resolved wintertime measurements of carbon monoxide and respirable particles (RSP) enable exploration of peak pollution periods in a village in Jilin Province, China, characterized by household use of both coal and biomass, as well as several "improved" (gas or electric) fuels. Our data indicate a 6-fold increase in peak 1 h PM (1.9 mg/m3) concentrations relative to 24 h mean PM (0.31 mg/m3). Peak 1 h CO concentrations (20.5 ppm) routinely approached and often (27%) exceeded the World Health Organization's 1 h guideline of 26 ppm, although the vast majority (95%) of kitchens were within China's residential indoor air quality guideline for CO on a 24 h basis. Choice of heating fuel and household smoking status were significant predictors of indoor air quality. Whether solid or "improved" (gas or electric) fuel was used for cooking had an even stronger effect, but in the opposite direction from expected, on both peak and daily average measures of air pollution. Peak pollution period concentrations of CO and PM were strongly correlated to daily concentrations of CO and RSP, respectively. Our results suggestthat due to the primary role of heating as a determinant of wintertime indoor air quality in northern Chinese villages, health-oriented interventions limited to provision of improved cooking fuel are insufficient. Our results illustrate that peak pollution periods may routinely exceed exposure regulations and evacuation limits, although this and previous studies document typical 24 h CO concentrations in rural Chinese kitchens to be within guidelines. Within a given village and for a given pollutant, daily pollutant concentrations may be strong predictors of peak pollution period concentrations.

Dicarboxylic acids and levoglucosan in aerosols from Indo-Gangetic Plain: Inferences from day night variability during wintertime.

PubMed

Sorathia, Fena; Rajput, Prashant; Gupta, Tarun

2018-05-15

This study assesses daytime and nighttime atmospheric abundance and molecular distribution of dicarboxylic acids (DCA: C 2 -C 10 ) and biomass burning tracers (levoglucosan and biomass burning derived potassium: K + BB ) in PM 10 (particulate matter with aerodynamic diameter≤10μm) from an urban location, Kanpur (in central Indo-Gangetic Plain: IGP) during wintertime (December 2015-February 2016). In this study, PM 10 varied from 130 to 242 and 175-388μgm -3 during daytime and nighttime, respectively. The average ratios of OC/EC (day: 12.3; night: 9.3) and WSOC/OC (day: 0.74; night: 0.48) were relatively high during daytime (OC: organic carbon; EC: elemental carbon; WSOC: water-soluble organic carbon). Strong linear correlations (R 2 ≥0.6; p<0.05) of OC with levoglucosan and K + BB suggest biomass burning emission as predominant source of organic aerosols over the IGP. The measured concentrations of total DCA (ΣC 2 -C 10 ) showed pronounced diurnal variability with a higher concentration during nighttime (2510±1025ngm -3 ) as compared to that in daytime (1499±562ngm -3 ). Concentrations of oxalic acid (C 2 ), succinic acid (C 4 ) and malonic acid (C 3 ) were predominantly high as compared to other congeners of DCA (C 2 -C 10 ) over central IGP. Relatively higher mass fraction (73.4%) of C 2 in total DCA during nighttime than that in daytime (61.5%) indicates role of secondary organic aerosols (SOAs) formation involving aqueous-phase chemistry. Strong linear correlations of C 2 with C 3 and C 4 plausibly suggest that C 2 can have predominant formation pathways via decomposition of higher congeners of DCA. Overall, strong linear correlations of C 2 with levoglucosan and sulphate suggest that biomass burning emission and secondary transformations are predominant sources of DCA over IGP during wintertime. Copyright © 2017 Elsevier B.V. All rights reserved.

Evaluation of Clear-Air Turbulence Diagnostics: GTG in Korea

NASA Astrophysics Data System (ADS)

Kim, J.-H.; Chun, H.-Y.; Jang, W.; Sharman, R. D.

2009-04-01

Turbulence forecasting algorithm, the Graphical Turbulence Guidance (GTG) system developed at NCAR (Sharman et al., 2006), is evaluated with available turbulence observations (e.g. pilot reports; PIREPs) reported in South Korea during the recent 4 years (2003-2007). Clear-air turbulence (CAT) is extracted from PIREPs by using cloud-to-ground lightning flash data from Korean Meteorological Administration (KMA). The GTG system includes several steps. First, 45 turbulence indices are calculated in the East Asian region near Korean peninsula using the Regional Data Assimilation and Prediction System (RDAPS) analysis data with 30 km horizontal grid spacing provided by KMA. Second, 10 CAT indices that performed ten best forecasting score are selected. The scoring method is based on the probability of detection, which is calculated using PIREPs exclusively of moderate-or-greater intensity. Various statistical examinations and sensitivity tests of the GTG system are performed by yearly and seasonally classified PIREPs in South Korea. Performance of GTG is more consistent and stable than that of any individual diagnostic in each year and season. In addition, current-year forecasting based on yearly PIREPs is better than adjacent-year forecasting and year-after-year forecasting. Seasonal forecasting is generally better than yearly forecasting, because selected CAT indices in each season represent meteorological condition much more properly than applying the selected CAT indices to all seasons. Wintertime forecasting is the best among the four seasonal forecastings. This is likely due to that the GTG system consists of many CAT indices related to jet stream, and turbulence associated with the jet can be most activated in wintertime under strong jet magnitude. On the other hand, summertime forecasting skill is much less than in wintertime. To acquire better performance for summertime forecasting, it is likely to develop more turbulence indices related to, for example, convections. By sensitivity test to the number of combined indices, it is found that yearly and seasonal GTG is the best when about 7 CAT indices are combined.

Evaluation of interventions to reduce air pollution from biomass smoke on mortality in Launceston, Australia: retrospective analysis of daily mortality, 1994-2007.

PubMed

Johnston, Fay H; Hanigan, Ivan C; Henderson, Sarah B; Morgan, Geoffrey G

2013-01-08

To assess the effect of reductions in air pollution from biomass smoke on daily mortality. Age stratified time series analysis of daily mortality with Poisson regression models adjusted for the effects of temperature, humidity, day of week, respiratory epidemics, and secular mortality trends, applied to an intervention and control community. Central Launceston, Australia, a town in which coordinated strategies were implemented to reduce pollution from wood smoke and central Hobart, a comparable city in which there were no specific air quality interventions. 67,000 residents of central Launceston and 148,000 residents of central Hobart (at 2001 census). Community education campaigns, enforcement of environmental regulations, and a wood heater replacement programme to reduce ambient pollution from residential wood stoves started in the winter of 2001. Changes in daily all cause, cardiovascular, and respiratory mortality during the 6.5 year periods before and after June 2001 in Launceston and Hobart. Mean daily wintertime concentration of PM(10) (particulate matter with particle size <10 µm diameter) fell from 44 µg/m(3) during 1994-2000 to 27 µg/m(3) during 2001-07 in Launceston. The period of improved air quality was associated with small non-significant reductions in annual mortality. In males the observed reductions in annual mortality were larger and significant for all cause (-11.4%, 95% confidence interval -19.2% to -2.9%; P=0.01), cardiovascular (-17.9%, -30.6% to -2.8%; P=0.02), and respiratory (-22.8%, -40.6% to 0.3%; P=0.05) mortality. In wintertime reductions in cardiovascular (-19.6%, -36.3% to 1.5%; P=0.06) and respiratory (-27.9%, -49.5% to 3.1%; P=0.07) mortality were of borderline significance (males and females combined). There were no significant changes in mortality in the control city of Hobart. Decreased air pollution from ambient biomass smoke was associated with reduced annual mortality in males and with reduced cardiovascular and respiratory mortality during winter months.

Isolating the atmospheric circulation response to Arctic sea-ice loss in the coupled climate system

NASA Astrophysics Data System (ADS)

Kushner, Paul; Blackport, Russell

2017-04-01

In the coupled climate system, projected global warming drives extensive sea-ice loss, but sea-ice loss drives warming that amplifies and can be confounded with the global warming process. This makes it challenging to cleanly attribute the atmospheric circulation response to sea-ice loss within coupled earth-system model (ESM) simulations of greenhouse warming. In this study, many centuries of output from coupled ocean/atmosphere/land/sea-ice ESM simulations driven separately by sea-ice albedo reduction and by projected greenhouse-dominated radiative forcing are combined to cleanly isolate the hemispheric scale response of the circulation to sea-ice loss. To isolate the sea-ice loss signal, a pattern scaling approach is proposed in which the local multidecadal mean atmospheric response is assumed to be separately proportional to the total sea-ice loss and to the total low latitude ocean surface warming. The proposed approach estimates the response to Arctic sea-ice loss with low latitude ocean temperatures fixed and vice versa. The sea-ice response includes a high northern latitude easterly zonal wind response, an equatorward shift of the eddy driven jet, a weakening of the stratospheric polar vortex, an anticyclonic sea level pressure anomaly over coastal Eurasia, a cyclonic sea level pressure anomaly over the North Pacific, and increased wintertime precipitation over the west coast of North America. Many of these responses are opposed by the response to low-latitude surface warming with sea ice fixed. However, both sea-ice loss and low latitude surface warming act in concert to reduce storm track strength throughout the mid and high latitudes. The responses are similar in two related versions of the National Center for Atmospheric Research earth system models, apart from the stratospheric polar vortex response. Evidence is presented that internal variability can easily contaminate the estimates if not enough independent climate states are used to construct them. References: Blackport, R. and P. Kushner, 2017: Isolating the atmospheric circulation response to Arctic sea-ice loss in the coupled climate system. J. Climate, in press. Blackport, R. and P. Kushner, 2016: The Transient and Equilibrium Climate Response to Rapid Summertime Sea Ice Loss in CCSM4. J. Climate, 29, 401-417, doi: 10.1175/JCLI-D-15-0284.1.

Can Email Prompting Minimize the Decrease in Wintertime Physical Activity Levels?

ERIC Educational Resources Information Center

Liguori, Gary; Mozumdar, Arupendra

2007-01-01

The primary purpose of this study is to evaluate the effectiveness of using email prompts to attenuate the decrease of physical activity in adults during a winter season. In addition, the secondary purposes were (1) to evaluate the effectiveness of email prompts at increasing motivation towards physical activity and (2) to evaluate the awareness…

Distribution, abundance, and habitat use of territorial male Boreal Owls (Aegolius funereus) in northeast Minnesota

Treesearch

William H. Lane; David E. Andersen; Thomas H. Nicholls

1997-01-01

We conducted nocturnal auditory surveys from 1987-1992 to determine the distribution, abundance, and habitat use of Boreal Owls (Aegolius funereus) in northeast Minnesota. We concentrated our efforts in areas where documented nesting attempts by the owls had occurred, along roadways maintained for winter-time access by motor vehicles, and by...

Nitrogen, Aerosol Composition, and Halogens on a Tall Tower (NACHTT): Overview of a wintertime air chemistry field study in the front range urban corridor of Colorado

NASA Astrophysics Data System (ADS)

Brown, Steven S.; Thornton, Joel A.; Keene, William C.; Pszenny, Alexander A. P.; Sive, Barkley C.; Dubé, William P.; Wagner, Nicholas L.; Young, Cora J.; Riedel, Theran P.; Roberts, James M.; VandenBoer, Trevor C.; Bahreini, Roya; Öztürk, Fatma; Middlebrook, Ann M.; Kim, Saewung; Hübler, Gerhard; Wolfe, Daniel E.

2013-07-01

The Nitrogen, Aerosol Composition, and Halogens on a Tall Tower (NACHTT) field experiment took place during late winter, 2011, at a site 33 km north of Denver, Colorado. The study included fixed-height measurements of aerosols, soluble trace gases, and volatile organic compounds near surface level, as well as vertically resolved measurements of nitrogen oxides, aerosol composition, soluble gas-phase acids, and halogen species from 3 to 270 m above ground level. There were 1928 individual profiles during the three-week campaign to characterize trace gas and aerosol distributions in the lower levels of the boundary layer. Nitrate and ammonium dominated the ionic composition of aerosols and originated primarily from local or regional sources. Sulfate and organic matter were also significant and were associated primarily with longer-range transport to the region. Aerosol chloride was associated primarily with supermicron size fractions and was always present in excess of gas-phase chlorine compounds. The nighttime radical reservoirs, nitryl chloride, ClNO2, and nitrous acid, HONO, were both consistently present in nighttime urban air. Nitryl chloride was especially pronounced in plumes from large point sources sampled aloft at night. Nitrous acid was typically most concentrated near the ground surface and was the dominant contributor (80%) to diurnally averaged primary OH radical production in near-surface air. Large observed mixing ratios of light alkanes, both in near-surface air and aloft, were attributable to local emissions from oil and gas activities.

Comparisons of Rain Estimates from Ground Radar and Satellite Over Mountainous Regions

NASA Technical Reports Server (NTRS)

Lin, Xin; Kidd, Chris; Tao, Jing; Barros, Ana

2016-01-01

A high-resolution rainfall product merging surface radar and an enhanced gauge network is used as a reference to examine two operational surface radar rainfall products over mountain areas. The two operational rainfall products include radar-only and conventional-gauge-corrected radar rainfall products. Statistics of rain occurrence and rain amount including their geographical, seasonal, and diurnal variations are examined using 3-year data. It is found that the three surface radar rainfall products in general agree well with one another over mountainous regions in terms of horizontal mean distributions of rain occurrence and rain amount. Frequency of rain occurrence and fraction of rain amount also indicate similar distribution patterns as a function of rain intensity. The diurnal signals of precipitation over mountain ridges are well captured and joint distributions of coincident raining samples indicate reasonable correlations during both summer and winter. Factors including undetected low-level precipitation, limited availability of gauges for correcting the Z-R relationship over the mountains, and radar beam blocking by mountains are clearly noticed in the two conventional radar rainfall products. Both radar-only and conventional-gauge-corrected radar rainfall products underestimate the rain occurrence and fraction of rain amount at intermediate and heavy rain intensities. Comparison of PR and TMI against a surface radar-only rainfall product indicates that the PR performs equally well with the high-resolution radar-only rainfall product over complex terrains at intermediate and heavy rain intensities during the summer and winter. TMI, on the other hand, requires improvement to retrieve wintertime precipitation over mountain areas.

The role of horizontal thermal advection in regulating wintertime mean and extreme temperatures over the central United States during the past and future

NASA Astrophysics Data System (ADS)

Wang, F.; Vavrus, S. J.

2017-12-01

Horizontal temperature advection plays an especially prominent role in affecting winter climate over continental interiors, where both climatological conditions and extreme weather are strongly regulated by transport of remote air masses. Central North America is one such region, and it experienced a major cold-air outbreak (CAO) a few years ago that some have related to amplified Arctic warming. Despite the known importance of dynamics in shaping the winter climate of this sector and the potential for climate change to modify heat transport, limited attention has been paid to the regional impact of thermal advection. Here, we use a reanalysis product and output from the Community Earth System Model's Large Ensemble to quantify the roles of zonal and meridional temperature advection over the central U. S. during winter, both in the late 20th and 21st centuries. We frame our findings as a "tug of war" between opposing influences of the two advection components and between these dynamical forcings vs. thermodynamic changes under greenhouse warming. For example, Arctic amplification leads to much warmer polar air masses, causing a moderation of cold-air advection into the central U. S., yet the model also simulates a wavier mean circulation and stronger northerly flow during CAOs, favoring lower regional temperatures. We also compare the predominant warming effect of zonal advection and overall cooling effect of meridional temperature advection as an additional tug of war. During both historical and future periods, zonal temperature advection is stronger than meridional advection over the Central U. S. The model simulates a future weakening of both zonal and meridional temperature advection, such that westerly flow provides less warming and northerly flow less cooling. On the most extreme warm days in the past and future, both zonal and meridional temperature advection have positive (warming) contributions. On the most extreme cold days, meridional cold air advection is more important than zonal warm air advection. CAOs in the future feature stronger northerly flow but less extreme temperatures (even relative to the warmer climate), exemplifying the complex competition between thermodynamic and dynamic influences.

Northern Hemisphere Autumn and Winter Climate Responses to Realistic Tibetan Plateau and Mongolia Snow Anomalies

NASA Astrophysics Data System (ADS)

Wu, Q.; Yao, Y.; Liu, S.

2017-12-01

The impact of the Eurasian snow cover extent (SCE) on the Northern Hemisphere (NH) circulation is first investigated by applying a lagged maximum covariance analysis (MCA) to monthly satellite-derived SCE and NCEP reanalysis data. Wintertime atmospheric signals significantly correlated with persistently autumn-early winter SCE anomalies are found in the leading two MCA modes. The first MCA mode indicates the effect of Eurasian snow cover anomalies on the Arctic Oscillation/North Atlantic Oscillation (AO/NAO). The second MCA mode links a persistent dipole of autumn and winter SCE anomalies over the Tibetan Plateau (TP) and Mongolia with winter Pacific-North America (PNA)-like atmospheric variations. A modeling study further investigates atmospheric responses to above TP and Mongolia snow forcings using multiple ensemble transient integrations of the CAM4 and CLM4.0 models. Model boundary conditions are based on climatological sea ice extent (SIE) and sea surface temperature (SST), and satellite observations of SCE and snow water equivalent (SWE) over the TP and Mongolia from October to March in 1997/98 (heavy TP and light Mongolia snow) and 1984/85 (light TP and heavy Mongolia snow), with model derived SCE and SWE elsewhere. In various forcing experiments, the ensemble-mean difference between simulations with these two extreme snow states identifies local, distant, concurrent, and delayed climatic responses. The main atmospheric responses to a dipole of high TP and low Mongolia SCE persisting from October to March (versus the opposite extreme) are strong TP surface cooling, warming in the surrounding China and Mongolia region, and a winter positive PNA-like response. The localized response is maintained by persistent diabatic cooling or heating, and the remote PNA response results mainly from the increased horizontal eastward propagation of stationary Rossby wave energy due to persistent TP snow forcing and also a winter transient eddy feedback mechanism. With a less persistent dipole anomaly in autumn or winter only, local responses are similar depending on the specific anomalies, but the winter PNA-like response is nearly absent or noticeably reduced.

Multi-RCM ensemble downscaling of global seasonal forecasts (MRED)

NASA Astrophysics Data System (ADS)

Arritt, R.

2009-04-01

Regional climate models (RCMs) have long been used to downscale global climate simulations. In contrast the ability of RCMs to downscale seasonal climate forecasts has received little attention. The Multi-RCM Ensemble Downscaling (MRED) project was recently initiated to address the question, Does dynamical downscaling using RCMs provide additional useful information for seasonal forecasts made by global models? MRED is using a suite of RCMs to downscale seasonal forecasts produced by the National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFS) seasonal forecast system and the NASA GEOS5 system. The initial focus is on wintertime forecasts in order to evaluate topographic forcing, snowmelt, and the usefulness of higher resolution for near-surface fields influenced by high resolution orography. Each RCM covers the conterminous U.S. at approximately 32 km resolution, comparable to the scale of the North American Regional Reanalysis (NARR) which will be used to evaluate the models. The forecast ensemble for each RCM is comprised of 15 members over a period of 22+ years (from 1982 to 2003+) for the forecast period 1 December - 30 April. Each RCM will create a 15-member lagged ensemble by starting on different dates in the preceding November. This results in a 120-member ensemble for each projection (8 RCMs by 15 members per RCM). The RCMs will be continually updated at their lateral boundaries using 6-hourly output from CFS or GEOS5. Hydrometeorological output will be produced in a standard netCDF-based format for a common analysis grid, which simplifies both model intercomparison and the generation of ensembles. MRED will compare individual RCM and global forecasts as well as ensemble mean precipitation and temperature forecasts, which are currently being used to drive macroscale land surface models (LSMs). Metrics of ensemble spread will also be evaluated. Extensive process-oriented analysis will be performed to link improvements in downscaled forecast skill to regional forcings and physical mechanisms. Our overarching goal is to determine what additional skill can be provided by a community ensemble of high resolution regional models, which we believe will define a strategy for more skillful and useful regional seasonal climate forecasts.

Development of a Lunar Borehole Seismometer

NASA Astrophysics Data System (ADS)

Passmore, P. R.; Siegler, M.; Malin, P. E.; Passmore, K.; Zacny, K.; Avenson, B.; Weber, R. C.; Schmerr, N. C.; Nagihara, S.

2017-12-01

Nearly all seismic stations on Earth are buried below the ground. Burial provides controlled temperatures and greater seismic coupling at little cost. This is also true on the Moon and other planetary bodies. Burial of a seismometer under just 1 meter of lunar regolith would provide an isothermal environment and potentially reduce signal scattering noise by an order of magnitude. Here we explain how we will use an existing NASA SBIR and PIDDP funded subsurface heat flow probe deployment system to bury a miniaturized, broadband, optical seismometer 1 meter below the lunar surface. The system is sensitive, low mass and low power. We believe this system offers a compelling architecture for NASA's future seismic exploration of the solar system. We will report on a prototype 3-axis, broadband seismometer package that has been tested under low pressure conditions in lunar-regolith simulant. The deployment mechanism reaches 1m depth in less than 25 seconds. Our designed and tested system: 1) Would be deployed at least 1m below the lunar surface to achieve isothermal conditions without thermal shielding or heaters, increase seismic coupling, and decrease noise. 2) Is small (our prototype probe is a cylinder 50mm in diameter, 36cm long including electronics, potentially as small as 10 cm with sensors only). 3) Is low-mass (each sensor is 0.1 kg, so an extra redundancy 4-component seismograph plus 1.5 kg borehole sonde and recorder weighs less than 2 kg and is feasibly smaller with miniaturized electronics). 4) Is low-power (our complete 3-sensor borehole seismographic system's power consumption is about half a Watt, or 7% of Apollo's 7.1 W average and 30% of the InSight SEIS's 1.5W winter-time heating system). 5) Is broadband and highly sensitive (the "off the shelf" sensors have a wide passband: 0.005-1000 Hz - and high dynamic range of 183 dB (or about 10-9g Hz-1/2, with hopes for simple modifications to be at least an order of magnitude better). Burial also aids the sensitivity, by decreasing scattered noise through the upper, extremely low density lunar regolith.

Investigation of wintertime cold-air pools and aerosol layers in the Salt Lake Valley using a lidar ceilometer

NASA Astrophysics Data System (ADS)

Young, Joseph Swyler

This thesis investigates the utility of lidar ceilometers, a type of aerosol lidar, in improving the understanding of meteorology and air quality in persistent wintertime stable boundary layers, or cold-air pools, that form in urbanized valley and basin topography. This thesis reviews the scientific literature to survey the present knowledge of persistent cold-air pools, the operating principles of lidar ceilometers, and their demonstrated utility in meteorological investigations. Lidar ceilometer data from the Persistent Cold-Air Pool Study (PCAPS) are then used with meteorological and air quality data from other in situ and remote sensing equipment to investigate cold-air pools that formed in Utah's Salt Lake Valley during the winter of 2010-2011. The lidar ceilometer is shown to accurately measure aerosol layer depth and aerosol loading, when compared to visual observations. A linear relationship is found between low-level lidar backscatter and surface particulate measurements. Convective boundary layer lidar analysis techniques applied to cold-air pool ceilometer profiles can detect useful layer characteristics. Fine-scale waves are observed and analyzed within the aerosol layer, with emphasis on Kelvin-Helmholz waves. Ceilometer aerosol backscatter profiles are analyzed to quantify and describe mixing processes in persistent cold-air pools. Overlays of other remote and in-situ observations are combined with ceilometer particle backscatter to describe specific events during PCAPS. This analysis describes the relationship between the aerosol layer and the valley inversion as well as interactions with large-scale meteorology. The ceilometer observations of hydrometers are used to quantify cloudiness and precipitation during the project, observing that 50% of hours when a PCAP was present had clouds or precipitation below 5 km above ground level (AGL). Then, combining an objective technique for determining hourly aerosol layer depths and correcting this subjectively during periods with low clouds or precipitation, a time series of aerosol depths was obtained. The mean depth of the surface-based aerosol layer during PCAP events was 1861 m MSL with a standard deviation of 135 m. The aerosol layer depth, given the approximate 1300 m altitude of the valley floor, is thus about 550 m, about 46% of the basin depth. The aerosol layer is present during much of the winter and is removed only during strong or prolonged precipitation periods or when surface winds are strong. Nocturnal fogs that formed near the end of high-stability PCAP episodes had a limited effect on aerosol layer depth. Aerosol layer depth was relatively invariant during the winter and during the persistent cold-air pools, while PM10 concentrations at the valley floor varied with bulk atmospheric stability associated primarily with passage of large-scale high- and low-pressure weather systems. PM10 concentrations also increased with cold-air pool duration. Mean aerosol loading in the surface-based aerosol layer, as determined from ceilometer backscatter coefficients, showed weaker variations than those of surface PM10 concentrations, suggesting that ineffective vertical mixing and aerosol layering are present in the cold-air pools. This is supported by higher time-resolution backscatter data, and it distinguishes the persistent cold-air pools from well-mixed convective boundary layers where ground-based air pollution concentrations are closely related to time-dependent convective boundary layer/aerosol depths. These results are discussed along with recommendations for future explorations of the ceilometer and cold-air pool topics.

Approaching the 2015 Arctic Sea Ice Minimum

NASA Image and Video Library

2017-12-08

As the sun sets over the Arctic, the end of this year’s melt season is quickly approaching and the sea ice cover has already shrunk to the fourth lowest in the satellite record. With possibly some days of melting left, the sea ice extent could still drop to the second or third lowest on record. Arctic sea ice, which regulates the planet’s temperature by bouncing solar energy back to space, has been on a steep decline for the last two decades. This animation shows the evolution of Arctic sea ice in 2015, from its annual maximum wintertime extent, reached on February 25, to September 6. Credit: NASA Scientific Visualization Studio DOWNLOAD THIS VIDEO HERE: svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=11999 NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Changes in the relationship NAO-Northern Hemisphere Temperature due to solar activity

NASA Astrophysics Data System (ADS)

de La Torre, L.; Gimeno, L.; Añel, J. A.; Nieto, R.; Tesouro, M.; Ribera, P.; García, R.; Hernández, E.

2003-04-01

The influence of the North Atlantic Oscillation (NAO) on wintertime Northern Hemisphere Temperature (NHT) is investigated. To check the hypothesis that the solar cycle is modulating this relationship, the sample was divided into two groups, one included the years corresponding to the three consecutive lowest values of sunspots number for every 11-years cycle (43 years) and the other the ones corresponding to the three consecutive highest numbers (39 years) for every 11-years cycle. If the data of each year were independent, the correlation coefficients between NAO index and NHT for 43 (39) years would be 0.30 (0.32) at 95% confidence level. Correlation index corresponding to the solar minimum phases was -0.17 and to the solar maximum phases was 0.35. The second result is statistically significant and indicates that there are periods when a positive phase of the NAO is related to positive anomalies of NHT- result that supports our current idea of the influence of the NAO on temperature- but there are other periods when NAO and NHT are not correlated. So, results suggest that this relationship has different sign according to the phase of the solar cycle. For solar maximum phases NAO and NHT are positively correlated -result assumed up to the moment- but for solar minimum phases correlations are not significant or even negative. This result is in agreement with the different extension of the NAO for solar cycle phases [1] - almost hemispheric for maximum phases and confined to the eastern Atlantic for minimum phases-.

CHARACTERIZATION OF THE WINTERTIME BOISE, IDAHO, AIR SHED: A COMPREHENSIVE FIELD STUDY REPORT FOR THE U.S. EPA OFFICE OF AIR QUALITY PLANNING AND STANDARDS

EPA Science Inventory

A large-scale ambient monitoring program vas conducted in Boise, Idaho, during the 1986-1987 winter heating season to evaluate the impact of residential wood combustion (RWC) and automotive emissions on the local air shed. onsecutive 12-h particle, organic, and gaseous samples we...

Effects of Exterior Insulation on Moisture Performance of Wood-Frame Walls in the Pacific Northwest: Measurements and Hygrothermal Modeling

Treesearch

Samuel V. Glass; Borjen Yeh; Benjamin J. Herzog

2016-01-01

Continuous exterior insulation on above-grade walls is becoming more common in many parts of North America. It is generally accepted that exterior insulation provides advantages for energy performance, by reducing thermal bridging, and for moisture performance, by warming the wood structural members, thereby reducing the potential for wintertime moisture accumulation....

Carcass addition does not enhance juvenile salmonid biomass, growth, or retention in six Northwestern California streams.

Treesearch

Bret Harvey; Margaret A. Wilzbach

2010-01-01

Fisheries managers commonly consider the addition of salmon carcasses when seeking to enhance salmonid populations. However, the range of environmental conditions under which the technique is effective remains poorly defined. We addressed this issue by measuring the effects of wintertime addition of salmon carcasses on the biomass, growth, and retention of juvenile...

FREE AND COMBINED AMINO COMPOUNDS IN ATMOSPHERIC FINE PARTICLES (PM2.5) AND FOG WATERS FROM NORTHERN CALIFORNIA. (R825433)

EPA Science Inventory

Atmospheric fine particles (PM_2.5) collected during August 1997–July 1998 and wintertime fog waters collected during 1997–1999 at Davis, California were analyzed for free and combined amino compounds. In both PM_2.5 and fog waters, the averag...

Winter sky brightness and cloud cover at Dome A, Antarctica

NASA Astrophysics Data System (ADS)

Moore, Anna M.; Yang, Yi; Fu, Jianning; Ashley, Michael C. B.; Cui, Xiangqun; Feng, Long Long; Gong, Xuefei; Hu, Zhongwen; Lawrence, Jon S.; Luong-Van, Daniel M.; Riddle, Reed; Shang, Zhaohui; Sims, Geoff; Storey, John W. V.; Tothill, Nicholas F. H.; Travouillon, Tony; Wang, Lifan; Yang, Huigen; Yang, Ji; Zhou, Xu; Zhu, Zhenxi

2013-01-01

At the summit of the Antarctic plateau, Dome A offers an intriguing location for future large scale optical astronomical observatories. The Gattini Dome A project was created to measure the optical sky brightness and large area cloud cover of the winter-time sky above this high altitude Antarctic site. The wide field camera and multi-filter system was installed on the PLATO instrument module as part of the Chinese-led traverse to Dome A in January 2008. This automated wide field camera consists of an Apogee U4000 interline CCD coupled to a Nikon fisheye lens enclosed in a heated container with glass window. The system contains a filter mechanism providing a suite of standard astronomical photometric filters (Bessell B, V, R) and a long-pass red filter for the detection and monitoring of airglow emission. The system operated continuously throughout the 2009, and 2011 winter seasons and part-way through the 2010 season, recording long exposure images sequentially for each filter. We have in hand one complete winter-time dataset (2009) returned via a manned traverse. We present here the first measurements of sky brightness in the photometric V band, cloud cover statistics measured so far and an estimate of the extinction.

Overview of VOC emissions and chemistry from PTR-TOF-MS measurements during the SusKat-ABC campaign: high acetaldehyde, isoprene and isocyanic acid in wintertime air of the Kathmandu Valley

NASA Astrophysics Data System (ADS)

Sarkar, C.; Sinha, V.; Kumar, V.; Rupakheti, M.; Panday, A.; Mahata, K. S.; Rupakheti, D.; Kathayat, B.; Lawrence, M. G.

2015-09-01

The Kathmandu Valley in Nepal suffers from severe wintertime air pollution. Volatile organic compounds (VOCs) are key constituents of air pollution, though their specific role in the Valley is poorly understood due to insufficient data. During the SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley-Atmospheric Brown Clouds) field campaign conducted in Nepal in the winter of 2012-2013, a comprehensive study was carried out to characterize the chemical composition of ambient Kathmandu air, including the determination of speciated VOCs by deploying a Proton Transfer Reaction Time of Flight Mass Spectrometer (PTR-TOF-MS)-the first such deployment in South Asia. 71 ion peaks (for which measured ambient concentrations exceeded the 2 σ detection limit) were detected in the PTR-TOF-MS mass scan data, highlighting the chemical complexity of ambient air in the Valley. Of the 71 species, 37 were found to have campaign average concentrations greater than 200 ppt and were identified based on their spectral characteristics, ambient diel profiles and correlation with specific emission tracers as a result of the high mass resolution (m/Δm > 4200) and temporal resolution (1 min) of the PTR-TOF-MS. The highest average VOC mixing ratios during the measurement period were (in rank order): acetaldehyde (8.8 ppb), methanol (7.4 ppb), acetone (4.2 ppb), benzene (2.7 ppb), toluene (1.5 ppb), isoprene (1.1 ppb), acetonitrile (1.1 ppb), C8-aromatics (~ 1 ppb), furan (~ 0.5 ppb), and C9-aromatics (0.4 ppb). Distinct diel profiles were observed for the nominal isobaric compounds isoprene (m/z = 69.070) and furan (m/z = 69.033). Comparison with wintertime measurements from several locations elsewhere in the world showed mixing ratios of acetaldehyde (~ 9 ppb), acetonitrile (~ 1 ppb) and isoprene (~ 1 ppb) to be among the highest reported till date. Two "new" ambient compounds namely, formamide (m/z = 46.029) and acetamide (m/z = 60.051), which can photochemically produce isocyanic acid in the atmosphere, are reported in this study along with nitromethane (a tracer for diesel exhaust) which has only recently been detected in ambient studies. Two distinct periods were selected during the campaign for detailed analysis: the first was associated with high wintertime emissions of biogenic isoprene, and the second with elevated levels of ambient acetonitrile, benzene and isocyanic acid from biomass burning activities. Emissions from biomass burning and biomass co-fired brick kilns were found to be the dominant sources for compounds such as propyne, propene, benzene and propanenitrile which correlated strongly with acetonitrile (r2 > 0.7), a chemical tracer for biomass burning. The calculated total VOC OH reactivity was dominated by acetaldehyde (24.0 %), isoprene (20.2 %) and propene (18.7 %), while oxygenated VOCs and isoprene collectively contributed to more than 68 % of the total ozone production potential. Based on known SOA yields and measured ambient concentrations in the Kathmandu Valley, the relative SOA production potential of VOCs were: benzene > naphthalene > toluene > xylenes > monoterpenes > trimethyl-benzenes > styrene > isoprene. The first ambient measurements from any site in South Asia of compounds with significant health effects such as isocyanic acid, formamide, acetamide, naphthalene and nitromethane have been reported in this study. Our results suggest that mitigation of intense wintertime biomass burning activities, in particular point sources such biomass co-fired brick kilns, would be important to reduce the emission and formation of toxic VOCs (such as benzene and isocyanic acid) in the Kathmandu Valley and improve its air quality.

MEASUREMENT OF EXHALED BREATH AND VENOUS BLOOD TO DEVELOP A PHYSIOLOGICALLY BASED PHARMACOKINETIC MODEL FOR HUMAN EXPOSURE TO METHYL TERTIARY-BUTYL ETHER AND THE PRODUCTION OF THE BIOMARKER TERTIARY-BUTYL ALCOHOL

EPA Science Inventory

Methyl tertiary-butyl ether (MTBE) is a common fuel additive used to increase the availability of oxygen in gasoline to reduce winter-time carbon monoxide emissions from automobiles. Also, MTBE boosts gasoline "octane" rating and, as such, allows reduction of benzene...

Emissions of Volatile Organic Compounds from Oil and Gas Operations in Northeastern Oklahoma - Wintertime Ambient Air Studies from Three Consecutive Years

NASA Astrophysics Data System (ADS)

Ghosh, B.

2017-12-01

Volatile organic compounds (VOCs) are emitted into the atmosphere from a variety of sources including oil and gas (O&G) operations, vehicle exhausts, industrial processes, and biogenic sources. Understanding of emission sources and their air quality impact is crucial for effective environmental policymaking and its implementation. Three consecutive wintertime campaigns to study ambient air were conducted in Northeastern Oklahoma during February-March of 2015, 2016, and 2017. The goals of these campaigns were to study ambient VOCs in the region, estimate their air quality impact, and understand how the impact changes over a span of three years. This presentation highlights results from the 2017 campaign. In-situ measurements of methane, ethane, and CO were conducted by an Aerodyne Dual QCL Analyzer while ozone and NOx were measured using Teledyne monitors. In addition, 392 whole air samples were collected and non-methane hydrocarbons (NMHCs) in the samples were analyzed using GC-MS (Agilent). High levels of methane (> 8 ppm) were observed during the study. Correlation with ethane indicated that methane primarily originated from O&G operations with little biogenic contributions. Among NMHCs, C2-C5 alkanes were the most dominant with mean mixing ratios ranging from 0.9 to 6.8 ppb. Chemical tracers (propane, ethyne, CO) and isomeric ratios (iC5/nC5, Figure 1) identified oil and gas activity as the primary source of NMHCs. Photochemical age was calculated to estimate emission source composition. Ozone showed strong diurnal variation characteristic of photochemical production with a maximum mixing ratio of 58 ppb. The results from the 2017 study will be compared with results from studies in 20151 and 20162 and their significance on local air quality will be discussed. References Ghosh, B.; Volatile Organic Compound Emissions from Oil and Gas Production Sources: A Pilot Study in Northeastern Oklahoma; Poster presentation at AGU Fall Meeting; 2015; A11M-0249; (Link) Ghosh, B.; Hydrocarbon Emission from Oil and Gas Production Activity in Northeastern Oklahoma - Wintertime Measurements in 2015 and 2016; Oral Presentation at AGU Fall Meeting; 2016; A14A-08; (Link)

Robotic observations of high wintertime carbon export in California coastal waters

NASA Astrophysics Data System (ADS)

Bishop, James K. B.; Fong, Michael B.; Wood, Todd J.

2016-05-01

Biologically mediated particulate organic and inorganic carbon (POC and PIC) export from surface waters is the principal determinant of the vertical oceanic distribution of pH and dissolved inorganic carbon and thus sets the conditions for air-sea exchange of CO2; exported organic matter also provides the energy fueling communities in the mesopelagic zone. However, observations are temporally and spatially sparse. Here we report the first hourly-resolved optically quantified POC and PIC sedimentation rate time series from an autonomous Lagrangian Carbon Flux Explorer (CFE), which monitored particle flux using an imaging optical sedimentation recorder (OSR) at depths below 140 m in the Santa Cruz Basin, CA, in May 2012, and in January and March 2013. Highest POC vertical flux ( ˜ 100-240 mmol C m-2 d-1) occurred in January, when most settling material was millimeter- to centimeter-sized aggregates but when surface biomass was low; fluxes were ˜ 18 and ˜ 6 mmol C m-2 d-1, respectively, in March and May, under high surface biomass conditions. An unexpected discovery was that January 2013 fluxes measured by CFE were 20 times higher than that measured by simultaneously deployed surface-tethered OSR; multiple lines of evidence indicate strong undersampling of aggregates larger than 1 mm in the latter case. Furthermore, the January 2013 CFE fluxes were about 10 times higher than observed during multiyear sediment trap observations in the nearby Santa Barbara and San Pedro basins. The strength of carbon export in biologically dynamic California coastal waters is likely underestimated by at least a factor of 3 and at times by a factor of 20.

Coincident Observations of Surface Ozone and NMVOCs over Abu Dhabi

NASA Astrophysics Data System (ADS)

Abbasi, Naveed; Majeed, Tariq; Iqbal, Mazhar; Tarasick, David; Davies, Jonathan; Riemer, Daniel; Apel, Eric

2016-07-01

The vertical profiles of ozone are measured coincidently with non-methane volatile organic compounds (NMVOCs) at the meteorological site located at the Abu Dhabi international airport (latitude 24.45N; longitude 54.22E) during the years 2012 - 2014. Some of the profiles show elevated surface ozone >95 ppbv during the winter months (December, January and February). The ground-level NMVOCs obtained from the gas chromatography-flame ionization detection/mass spectrometry system also show elevated values of acetylene, ethane, propane, butane, pentane, benzene, and toluene. NMVOCs and ozone abundances in other seasons are much lower than the values in winter season. NMVOCs are emitted from an extensive number of sources in urban environments including fuel production, distribution, and consumption, and serve as precursor of ozone. Transport sources contribute a substantial portion of the NMVOC burden to the urban atmosphere in developed regions. Abu Dhabi is located at the edge of the Arabian Gulf and is highly affected by emissions from petrochemical industries in the neighboring Gulf region. The preliminary results indicate that wintertime enhancement in ozone is associated with large values of NMVOCs at Abu Dhabi. The domestic production of surface ozone is estimated from the combination of oxygen recombination and NMVOCs and compared with the data. It is estimated that about 40-50% of ozone in Abu Dhabi is transported from the neighbouring petrochemical industries. We will present ozone sounding and NMVOCs data and our model estimates of surface ozone, including a discussion on the high levels of the tropospheric ozone responsible for contaminating the air quality in the UAE. This work is supported by National Research Foundation, UAE.

Interannual variability of ammonia concentrations over the United States: sources and implications

NASA Astrophysics Data System (ADS)

Schiferl, Luke D.; Heald, Colette L.; Van Damme, Martin; Clarisse, Lieven; Clerbaux, Cathy; Coheur, Pierre-François; Nowak, John B.; Neuman, J. Andrew; Herndon, Scott C.; Roscioli, Joseph R.; Eilerman, Scott J.

2016-09-01

The variability of atmospheric ammonia (NH3), emitted largely from agricultural sources, is an important factor when considering how inorganic fine particulate matter (PM2.5) concentrations and nitrogen cycling are changing over the United States. This study combines new observations of ammonia concentration from the surface, aboard aircraft, and retrieved by satellite to both evaluate the simulation of ammonia in a chemical transport model (GEOS-Chem) and identify which processes control the variability of these concentrations over a 5-year period (2008-2012). We find that the model generally underrepresents the ammonia concentration near large source regions (by 26 % at surface sites) and fails to reproduce the extent of interannual variability observed at the surface during the summer (JJA). Variability in the base simulation surface ammonia concentration is dominated by meteorology (64 %) as compared to reductions in SO2 and NOx emissions imposed by regulation (32 %) over this period. Introduction of year-to-year varying ammonia emissions based on animal population, fertilizer application, and meteorologically driven volatilization does not substantially improve the model comparison with observed ammonia concentrations, and these ammonia emissions changes have little effect on the simulated ammonia concentration variability compared to those caused by the variability of meteorology and acid-precursor emissions. There is also little effect on the PM2.5 concentration due to ammonia emissions variability in the summer when gas-phase changes are favored, but variability in wintertime emissions, as well as in early spring and late fall, will have a larger impact on PM2.5 formation. This work highlights the need for continued improvement in both satellite-based and in situ ammonia measurements to better constrain the magnitude and impacts of spatial and temporal variability in ammonia concentrations.

Influence of Mesoscale Eddies on New Production in the Sargasso Sea

NASA Technical Reports Server (NTRS)

McGillicuddy, D. J., Jr.; Robinson, A. R.; Siegel, D. A.; Jannasch, H. W.; Johnson, R.; Dickey, T. D.; McNeil, J.; Michaels, A. F.; Knap, A. H.

1998-01-01

It is problematic that geochemical estimates of new production, that fraction of total primary production in surface waters fueled by externally supplied nutrients, in oligotrophic waters of the open ocean surpass that which can be sustained by the traditionally accepted mechanisms of nutrient supply. In the cam of the Sargasso Sea, for example, these mechanisms account for less than half of the annual nutrient requirement indicated by new production estimates based on three independent transient-tracer techniques. Specifically, approximately one-quarter to one-third of the annual nutrient requirement can be supplied by entrainment into the mixed layer during wintertime convection, with minor contributions from mixing in the thermocline and wind-driven transport (the potentially important role of nitrogen fixation- for which estimates vary by an order of magnitude in this region- is excluded from this budget). Here we present four lines of evidence-eddy-resolving model simulations, high-resolution observations from moored instrumentation, shipboard surveys and satellite data-which suggest that the vertical flux of nutrients induced by the dynamics of mesoscale eddies is sufficient to balance the nutrient budget in the Sargasso Sea.

Continental shelves as a variable but increasing global sink for atmospheric carbon dioxide.

PubMed

Laruelle, Goulven G; Cai, Wei-Jun; Hu, Xinping; Gruber, Nicolas; Mackenzie, Fred T; Regnier, Pierre

2018-01-31

It has been speculated that the partial pressure of carbon dioxide (pCO 2 ) in shelf waters may lag the rise in atmospheric CO 2 . Here, we show that this is the case across many shelf regions, implying a tendency for enhanced shelf uptake of atmospheric CO 2 . This result is based on analysis of long-term trends in the air-sea pCO 2 gradient (ΔpCO 2 ) using a global surface ocean pCO 2 database spanning a period of up to 35 years. Using wintertime data only, we find that ΔpCO 2 increased in 653 of the 825 0.5° cells for which a trend could be calculated, with 325 of these cells showing a significant increase in excess of +0.5 μatm yr -1 (p < 0.05). Although noisier, the deseasonalized annual data suggest similar results. If this were a global trend, it would support the idea that shelves might have switched from a source to a sink of CO 2 during the last century.

Wintertime Air-Sea Gas Transfer Rates and Air Injection Fluxes at Station Papa in the NE Pacific

NASA Astrophysics Data System (ADS)

McNeil, C.; Steiner, N.; Vagle, S.

2008-12-01

In recent studies of air-sea fluxes of N2 and O2 in hurricanes, McNeil and D'Asaro (2007) used a simplified model formulation of air-sea gas flux to estimate simultaneous values of gas transfer rate, KT, and air injection flux, VT. The model assumes air-sea gas fluxes at high to extreme wind speeds can be explained by a combination of two processes: 1) air injection, by complete dissolution of small bubbles drawn down into the ocean boundary layer by turbulent currents, and 2) near-surface equilibration processes, such as occurs within whitecaps. This analysis technique relies on air-sea gas flux estimates for two gases, N2 and O2, to solve for the two model parameters, KT and VT. We present preliminary results of similar analysis of time series data collected during winter storms at Station Papa in the NE Pacific during 2003/2004. The data show a clear increase in KT and VT with increasing NCEP derived wind speeds and acoustically measured bubble penetration depth.

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

Bishop, James K.B.; Wood, Todd

Three Carbon Explorer (CE) floats profiling to kilometer depths in the Southern Ocean tracked dawn-dusk variations of mixing/stratification, particulate organic carbon (POC), and light scattering and sedimentation at 100, 250, and 800 m continuously from January 2002 to April 2003. Data were analyzed in conjunction with contemporaneous satellite winds and chlorophyll and derived subsurface light fields. The CE deployed at 66{sup o}S 172{sup o}W operated in the ice edge zone in absence of light. Two CEs deployed at 55{sup o}S 172{sup o}W recorded wintertime mixing to {approx}400 m, yet observed very different bloom dynamics and sedimentation the following spring. Fourmore » hypotheses are explored. The strongest is that shallow transient stratification of the deep winter mixed layer to shallower than photosynthetic critical depth occurred more frequently in the non-bloom/higher sedimentation case. The lower particle export to 800 m under the bloom was hypothesized to be due to higher interception of sinking carbon by a relatively starved over wintering zooplankton population. In the Southern Ocean surface phytoplankton biomass may counter indicate particle flux at kilometer depths.« less

Estimation of Surface Air Temperature from MODIS 1km Resolution Land Surface Temperature Over Northern China

NASA Technical Reports Server (NTRS)

Shen, Suhung; Leptoukh, Gregory G.; Gerasimov, Irina

2010-01-01

Surface air temperature is a critical variable to describe the energy and water cycle of the Earth-atmosphere system and is a key input element for hydrology and land surface models. It is a very important variable in agricultural applications and climate change studies. This is a preliminary study to examine statistical relationships between ground meteorological station measured surface daily maximum/minimum air temperature and satellite remotely sensed land surface temperature from MODIS over the dry and semiarid regions of northern China. Studies were conducted for both MODIS-Terra and MODIS-Aqua by using year 2009 data. Results indicate that the relationships between surface air temperature and remotely sensed land surface temperature are statistically significant. The relationships between the maximum air temperature and daytime land surface temperature depends significantly on land surface types and vegetation index, but the minimum air temperature and nighttime land surface temperature has little dependence on the surface conditions. Based on linear regression relationship between surface air temperature and MODIS land surface temperature, surface maximum and minimum air temperatures are estimated from 1km MODIS land surface temperature under clear sky conditions. The statistical errors (sigma) of the estimated daily maximum (minimum) air temperature is about 3.8 C(3.7 C).

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.

Potential Impact of Land Use Change on Future Regional Climate in the Southeastern U.S.: Reforestation and Crop Land Conversion

NASA Technical Reports Server (NTRS)

Trail, M.; Tsimpidi, A. P.; Liu, P.; Tsigaridis, Konstantinos; Hu, Y.; Nenes, A.; Stone, B.; Russell, A. G.

2013-01-01

The impact of future land use and land cover changes (LULCC) on regional and global climate is one of the most challenging aspects of understanding anthropogenic climate change. We study the impacts of LULCC on regional climate in the southeastern U.S. by downscaling the NASA Goddard Institute for Space Studies global climate model E to the regional scale using a spectral nudging technique with the Weather Research and Forecasting Model. Climate-relevant meteorological fields are compared for two southeastern U.S. LULCC scenarios to the current land use/cover for four seasons of the year 2050. In this work it is shown that reforestation of cropland in the southeastern U.S. tends to warm surface air by up to 0.5 K, while replacing forested land with cropland tends to cool the surface air by 0.5 K. Processes leading to this response are investigated and sensitivity analyses conducted. The sensitivity analysis shows that results are most sensitive to changes in albedo and the stomatal resistance. Evaporative cooling of croplands also plays an important role in regional climate. Implications of LULCC on air quality are discussed. Summertime warming associated with reforestation of croplands could increase the production of some secondary pollutants, while a higher boundary layer will decrease pollutant concentrations; wintertime warming may decrease emissions from biomass burning from wood stoves

Sea Ice Retreat and its Impact on the Intensity of Open-Ocean Convection in the Greenland and Iceland Seas

NASA Astrophysics Data System (ADS)

Moore, K.; Våge, K.; Pickart, R. S.; Renfrew, I.

2016-12-01

The air-sea transfer of heat and freshwater plays a critical role in the global climate system. This is particularly true for the Greenland and Iceland Seas, where these fluxes drive ocean convection that contributes to Denmark Strait Overflow Water, the densest component of the lower limb of the Atlantic Meridional Overturning Circulation (AMOC). This buoyancy transfer is most pronounced during the winter downstream of the ice edge, where the cold and dry Arctic air first comes in contact with the relatively warm ocean surface. Here we show that the wintertime retreat of sea ice in the region, combined with different rates of warming for the atmosphere and sea surface of the Greenland and Iceland Seas, has resulted in statistically significant reductions of approximately 20% in the magnitude of the winter air-sea heat fluxes since 1979. Furthermore, it is demonstrated that modes of climate variability other than the North Atlantic Oscillation (NAO) are required to fully characterize the regional air-sea interaction in this region. Mixed-layer model simulations imply that a continued decrease in atmospheric forcing will exceed a threshold for the Greenland Sea whereby convection will become depth limited, reducing the ventilation of mid-depth waters in the Nordic Seas. In the Iceland Sea, further reductions have the potential to decrease the supply of the densest overflow waters to the AMOC.

Testing Extensions of Our Quantitative Daily of San Joaquin Wintertime Aerosols Using MAIAC and Meteorology Without Transport/Transformation Assumptions

NASA Technical Reports Server (NTRS)

Chatfield, Robert B.; Sorek Hamer, Meytar; Esswein, Robert F.

2017-01-01

The Western US and many regions globally present daunting difficulties in understanding and mapping PM2.5 episodes. We evaluate extensions of a method independent of source-description and transport/transformation. These regions suffer frequent few-day episodes due to shallow mixing; low satellite AOT and bright surfaces complicate the description. Nevertheless, we expect residual errors in our maps of less than 8 ug/m^3 in episodes reaching 60-100 ug/m^3; maps which detail pollution from Interstate 5. Our current success is due to use of physically meaningful functions of MODIS-MAIAC-derived AOD, afternoon mixed-layer height, and relative humidity for a basin in which the latter are correlated. A mixed-effects model then describes a daily AOT-to-PM2.5 relationship. (Note: in other published mixed-effects models, AOT contributes minimally. We seek to extend on these to develop useful estimation methods for similar situations. We evaluate existing but more spotty information on size distribution (AERONET, MISR, MAIA, CALIPSO, other remote sensing). We also describe the usefulness of an equivalent mixing depth for water vapor vs meteorological boundary layer height. Each has virtues and limitations. Finally, we begin to evaluate methods for removing the complications due to detached but polluted layers (which don't mix to the surface) using geographical, meteorological, and remotely sensed data.

Model representation of salinity anomalies and the stability of the North Atlantic overturning circulation

NASA Astrophysics Data System (ADS)

Megann, A.; New, A.; Blaker, A.

2012-04-01

Vellinga and Wu (2004) and others have identified feedback cycles governing the decadal variability of the North Atlantic overturning circulation, in which modulation of tropical rainfall creates near-surface salinity anomalies that propagate northward to the winter convection regions, where they affect the wintertime convection through changes in surface density. Freshwater "hosing" experiments, in which 0.1 Sv of extra freshwater is added to the convection region, are described using two climate models: the UK Met Office's HadCM3; and CHIME, which is identical to HadCM3 except for the replacement of the z-coordinate ocean component of HadCM3 with the hybrid isopycnic model HYCOM. While HadCM3 shows an unambiguous weakening of the meridional overturning circulation (MOC) by 5 Sv, the MOC in CHIME initially starts to decrease but returns to a value close to that in the control experiment after 40-50 years even though the hosing flux is still being applied. It will be shown that the recovery of the overturning in CHIME is mainly due to enhanced advective transport of salt from the subtropics by salinity anomalies. These are found to be substantially more coherent meridionally in CHIME than in HadCM3, consistent with the known superior ability of the isopycnic model formulation to preserve watermass properties over long distances.

On the role of hydrophobic Si-based protective coatings in limiting mortar deterioration.

PubMed

Cappelletti, G; Fermo, P; Pino, F; Pargoletti, E; Pecchioni, E; Fratini, F; Ruffolo, S A; La Russa, M F

2015-11-01

In order to avoid both natural and artificial stone decay, mainly due to the interaction with atmospheric pollutants (both gases such as NOx and SO2 and particulate matter), polymeric materials have been widely studied as protective coatings enable to limit the penetration of fluids into the bulk material. In the current work, an air hardening calcic lime mortar (ALM) and a natural hydraulic lime mortar (HLM) were used as substrates, and commercially available Si-based resins (Alpha®SI30 and Silres®BS16) were adopted as protective agents to give hydrophobicity features to the artificial stones. Surface properties of coatings and their performance as hydrophobic agents were studied using different techniques such as contact angle measurements, capillary absorption test, mercury intrusion porosimetry, surface free energy, colorimetric measurements and water vapour permeability tests. Finally, some exposure tests to UV radiation and to real polluted atmospheric environments (a city centre and an urban background site) were carried out during a wintertime period (when the concentrations of the main atmospheric pollutants are higher) in order to study the durability of the coating systems applied. The effectiveness of the two commercial resins in reducing salt formation (sulphate and nitrate), induced by the interaction of the mortars with the atmospheric pollutants, was demonstrated in the case of the HLM mortar. Graphical Abstract ᅟ.

Detection of deep water formation from remote sensing chlorophyll in the NW Mediterranean Sea

NASA Astrophysics Data System (ADS)

Bernardello, Raffaele; Bahamon, Nixon; Ahumada, Miguel-Angel; Martin, Adrian; Henson, Stephanie

2015-04-01

The Northwestern Mediterranean Sea is one of the few regions in the world where Deep Water Formation (DWF) occurs. During wintertime cold and dry winds that typically occur in strong bursts lasting a few days, are able to erode the near-surface stability over this area, exposing the weakly stratified underwaters and initiate a phase of violent mixing and deep convection. DWF is not a steady-state process that recurs every year. Variations in wind stress and heat flux over the winter can induce a marked interannual variability: during some years the process is specially intense and completely absent during others. The extent of the area over which DWF occurs is also uncertain. The interannual variability of the DWF process is also associated to the variability in the seasonal phytoplankton dynamics over the area. The extent of the vertical mixing set the total amount of nutrients available for the phytoplankton during the following spring bloom. However, before the bloom, when deep convection is still active, surface chlorophyll (an index for phytoplankton biomass) is vertically diluted showing low surface concentration. The occurrence of these patches of anomalously low chlorophyll concentration can, in principle, be associated to the presence of active deep convection. In this study we investigate the possibility of exploiting such association in order to quantify the duration of deep convection and the extent of the area over which it occurs. These goals will be achieved through the analysis of remote sensing chlorophyll data and in-situ Argo-floats profiles.

Importance of Ekman transport and gyre circulation change on seasonal variation of surface dissolved iron in the western subarctic North Pacific

NASA Astrophysics Data System (ADS)

Nakanowatari, Takuya; Nakamura, Tomohiro; Uchimoto, Keisuke; Nishioka, Jun; Mitsudera, Humio; Wakatsuchi, Masaaki

2017-05-01

Iron (Fe) is an essential nutrient for marine phytoplankton and it constitutes an important element in the marine carbon cycle in the ocean. This study examined the mechanisms controlling seasonal variation of dissolved Fe (dFe) in the western subarctic North Pacific (WSNP), using an ocean general circulation model coupled with a simple biogeochemical model incorporating a dFe cycle fed by two major sources (atmospheric dust and continental shelf sediment). The model reproduced the seasonal cycle of observed concentrations of dFe and macronutrients at the surface in the Oyashio region with maxima in winter (February-March) and minima in summer (July-September), although the simulated seasonal amplitudes are a half of the observed values. Analysis of the mixed-layer dFe budget indicated that both local vertical entrainment and lateral advection are primary contributors to the wintertime increase in dFe concentration. In early winter, strengthened northwesterly winds excite southward Ekman transport and Ekman upwelling over the western subarctic gyre, transporting dFe-rich water southward. In mid to late winter, the southward western boundary current of the subarctic gyre and the outflow from the Sea of Okhotsk also bring dFe-rich water to the Oyashio region. The contribution of atmospheric dust to the dFe budget is several times smaller than these ocean transport processes in winter. These results suggest that the westerly wind-induced Ekman transport and gyre circulation systematically influence the seasonal cycle of WSNP surface dFe concentration.

Balloon-Borne Aerosol Particle Counter Measurements Made in Wintertime at Grafenwoehr, West Germany.

DTIC Science & Technology

1976-06-01

n ~~t * 4* M S.0* ’W i’’ C1t LI J L N C.4 P- L ’ .:.-- t..4w f~ PO1Jt C4a ~ I)..4C t-N.O tt. MCJ WIJt .’ L) IC,,1" MI’) (.4~tt I’l.Ii I It C M M Inr"M

Reduced Snow Cover Increases Wintertime Nitrous Oxide (N 2O) Emissions from an Agricultural Soil in the Upper U.S. Midwest

DOE PAGES

Ruan, Leilei; Robertson, G. Philip

2016-11-21

Throughout most of the northern hemisphere, snow cover decreased in almost every winter month from 1967 to 2012. Because snow is an effective insulator, snow cover loss has likely enhanced soil freezing and the frequency of soil freeze–thaw cycles, which can disrupt soil nitrogen dynamics including the production of nitrous oxide (N 2O). Here, we used replicated automated gas flux chambers deployed in an annual cropping system in the upper Midwest US for three winters (December–March, 2011–2013) to examine the effects of snow removal and additions on N 2O fluxes. Diminished snow cover resulted in increased N2O emissions each year;more » over the entire experiment, cumulative emissions in plots with snow removed were 69% higher than in ambient snow control plots and 95% higher than in plots that received additional snow (P < 0.001). Higher emissions coincided with a greater number of freeze–thaw cycles that broke up soil macroaggregates (250–8000 µm) and significantly increased soil inorganic nitrogen pools. We conclude that winters with less snow cover can be expected to accelerate N 2O fluxes from agricultural soils subject to wintertime freezing.« less

Autonomous Gliders Observed Physical and Biogeochemical Interplay at Submesoscale during Deep Convection in the Gulf of Lions (NW Mediterranean)

NASA Astrophysics Data System (ADS)

Bosse, A.; Testor, P.; Damien, P.; D'Ortenzio, F.; Prieur, L. M.; Estournel, C.; Marsaleix, P.; Mortier, L.

2016-02-01

Since 2010, sustained observations of the circulation and water properties of the NW Mediterranean Sea have been carried out by gliders in the framework of the MOOSE observatory (Mediterranean Ocean Observatory System for the Environment: http://www.moose-network.fr/). They regularly sampled the wintertime Northern Current (NC), the deep convection zone as well as the North Balearic Front (NBF) collecting a great amount of physical and biogeochemical measurements.During periods of deep convection, the offshore mixed layer can reach great depths (>2300 m) in the Gulf of Lions. Baroclinic fronts then become very intense and reveal a lot of variability at submesoscale in the upper 500 m or so. In terms of process, symmetric instability has been evidenced to occurr during strong wind events by gliders measurements. Complementary analysis performed with the help of a high-resolution regional model (dx,dy=1 km) highlight the prominent role of downfront winds in triggering this instability. Important vertical exchanges of oceanic tracers at the front approximately aligned with isopycnals of magnitude O(100m/day) occur in response to this strong atmospheric forcing. Finally, gliders measurements of Chl-a fluorescence show how this frontal instability seems to stimulate phytoplankton growth in frontal regions during harsh wintertime conditions.

Modeling study of secondary organic aerosol in winter in China using NAQPMS

NASA Astrophysics Data System (ADS)

Yang, W.; Li, J.

2017-12-01

The concentration of organic aerosol (OA) in the central and eastern China is much higher than that in Europe and America. Compared with the observation, the current numerical modeling studies largely underestimated the concentration of OA, especially the secondary component. Based on the volatility basis set framework, a secondary organic aerosol (SOA) module was developed, which considering the multi-generation oxidation of volatile organic compounds (VOCs), semi-volatile POA and intermediate volatility organic compounds (IVOCs). The newly developed SOA module was coupled into the NAQPMS, and the performance of the simulation was validated by the observation with high temporal resolution. In wintertime, the OA concentration in the central and eastern China was maintained above 15-20 μg·m-3, and SOA accounted for 50-65% of OA concentration. The OA concentration even reached 40 μg·m-3 in the provinces emitting most pollutants (such as Hunan, Hubei, Henan, Anhui, Jiangsu, Shandong and Hubei province). IVOCs were important precursors of SOA in China, and could reduce the great discrepancy between simulation and observation. In wintertime, the contribution from IVOCs accounted for 60-80% of SOA formation. The aging of semi-volatile POA had less impact on the SOA formation, which maintained only 2-8% over central and eastern China.

Constraining wintertime sources of inorganic chlorine over the northeast United States

NASA Astrophysics Data System (ADS)

Haskins, J.; Jaegle, L.; Shah, V.; Lopez-Hilfiker, F.; Lee, B. H.; Campuzano Jost, P.; Schroder, J. C.; Day, D. A.; Fiddler, M. N.; Holloway, J. S.; Sullivan, A.; Veres, P. R.; Weber, R. J.; Dibb, J. E.; Brown, S. S.; Jimenez, J. L.; Thornton, J. A.

2017-12-01

Wintertime multiphase chlorine chemistry is thought to play a significant role in the regional distribution of oxidants, the lifetime of VOCs, and the transport of NOx downwind of urban sources. However, the sources and chemistry of reactive chlorine remain highly uncertain. During the WINTER 2015 aircraft campaign, the inorganic chlorine budget was dominated by HCl (g) and total particulate chloride, accounting for greater than 85% of the total chlorine budget within the boundary layer. The total concentration of inorganic chlorine compounds found over marine regions was 1014 pptv and 609 pptv over continental regions with variability found to be driven by changes in meteorological conditions, particle liquid water content, particle pH, and proximity to large anthropogenic sources. However, displacement of particle chloride was often not a large enough source to fully explain the concentrations of gas phase Cly compounds. We use the GEOS-Chem global chemical transport model to simulate the emissions, gas-particle partitioning, and downwind transport and deposition of Cly during winter. Simulated concentrations of HCl, particle chloride, and other dominant Cly compounds are compared to measurements made during the WINTER aircraft campaign. The relative roles of Cly sources from sea-salt aerosol and anthropogenic sources such as power plants, biomass burning and road salt are explored.

The other side of the coin: urban heat islands as shields from extreme cold

NASA Astrophysics Data System (ADS)

Yang, J.; Bou-Zeid, E.

2017-12-01

Extensive studies focusing on urban heat islands (UHIs) during hot periods create a perception that UHIs are invariably hazardous to human health and the sustainability of cities. Consequently, cities have invested substantial resources to try to mitigate UHIs. These urban policies can have serious repercussions since the health risks associated with cold weather are in fact higher than for heat episodes, yet wintertime UHIs have hardly been explored. We combine ground observations from 12 U.S. cities and high-resolution simulations to show that UHIs not only warm urban areas in the winter, but also further intensify during cold waves by up to 1.32 ± 0.78 oC (mean ± standard deviation) at night. Urban heat islands serve as shelters against extreme colds and provide invaluable benefits of reducing health risks and heating demand. More importantly, our simulations indicate that standard UHI mitigation measures such as green or cool roofs reduce these cold time amenities to different extents. Cities, particularly in cool and cold temperate climates, should hence revisit policies and efforts that are only desgined for hot periods. A paradigm shift is urgently needed to give an equal weight to the wintertime benefits of UHIs in the sustainability and resilience blueprints of cities.

The possible roles of solar ultraviolet-B radiation and vitamin D in reducing case-fatality rates from the 1918–1919 influenza pandemic in the United States

PubMed Central

Giovannucci, Edward

2009-01-01

Deaths during the 1918–1919 influenza pandemic have been linked to both the influenza virus and secondary bacterial lung infections. Case fatality rates and percentage of influenza cases complicated by pneumonia were available from survey data for twelve United States locations in the 1918–1919 pandemic. This study analyzes case fatality rates and cases complicated by pneumonia with respect to estimated summertime and wintertime solar ultraviolet-B (UVB) doses as indicators of population mean vitamin D status. Substantial correlations were found for associations of July UVB dose with case fatality rates (r = −0.72, p = 0.009) and rates of pneumonia as a complication of influenza (r = −0.77, p = 0.005). Similar results were found for wintertime UVB. Vitamin D upregulates production of human cathelicidin, LL-37, which has both antimicrobial and antiendotoxin activities. Vitamin D also reduces the production of proinflammatory cytokines, which could also explain some of the benefit of vitamin D since H1N1 infection gives rise to a cytokine storm. The potential role of vitamin D status in reducing secondary bacterial infections and loss of life in pandemic influence requires further evaluation. PMID:20592793

Ammonia Partitioning into the Condensed Phase in Winter Time Conditions

NASA Astrophysics Data System (ADS)

Green, J. R.; Bililign, S.; Fiddler, M. N.; Leen, J. B.; Holloway, J. S.; Fibiger, D. L.; McDuffie, E. E.; Thornton, J. A.; Brown, S. S.

2015-12-01

Secondary aerosol (SOA) formation has been linked to health problems and environmental damage in regions impacted by the emission of gaseous NH3 and SO2. SOA formation, (NH4)2SO4 and NH4NO3, in the presence of NO NO2, is favored under high relative humidity and low temperature and low temperature conditions. In the East and Mid Atlantic regions of the United States humidity is low in wintertime. Utilizing ambient concentration data of gaseous NO, NO2, SO2 and NH3 collected aboard a survey aircraft we examined the partitioning of gaseous NH3 towards aerosol products. The calculated mixing ratio of gaseous SO2/NH3 correlated with relative humidity will give an indication of the potential SOA formation when the mixing ratio of other reactants is small in the region of interest. The data obtained originates from a series of night and day survey flights on a C-130 aircraft that occurred from February 3 to March 13, 2015 over the Eastern coastal region of the United States extending from New York to Florida. NOx was obtained from the Airborne Ring-down Nitrogen Oxide Laser Detector (ARNOLD) instrument (NOAA) and Thermal Dissociation-Laser Induced Fluorescence (TD-LIF) (UC Berkley). SO2 measurements were done using the TECO 43C SO2 analyzer and for NH3 measurements the an Ammonia Analyzer - Trace (NH3) (Los Gatos Research). Estimates of aerosol dry deposition fluxes are presented.

Relationships between teleconnection patterns and Turkish climatic extremes

NASA Astrophysics Data System (ADS)

Baltacı, H.; Akkoyunlu, B. O.; Tayanç, M.

2017-12-01

This is a study on the effects of teleconnection patterns (TPs) on the extremes of temperature and precipitation over Turkey. Relationships between five teleconnection patterns, North Atlantic Oscillation (NAO), Arctic Oscillation (AO), East Atlantic-Western Russia (EAWR), East Atlantic (EA), and Scandinavian (SCA) patterns, and 11 climate extreme indices were studied by using 94 uniformly distributed meteorological stations over Turkey for the period of 1965-2014. Analyzing strong positive and negative temperature deviations from the 50-year-winter means shows that such extremes can often be explained by using AO and EAWR patterns. During the negative AO, generally more warm days occur over Black Sea (r = -0.6) and Aegean regions (r = -0.7). This phase of AO also generates above-normal precipitation in the western parts of the Anatolian Peninsula (r around - 0.5). Winter-time negative AO is mainly associated with the presence of a deepened Genoa cyclone over Italy that can transport warm and moist air mass from Mediterranean Sea towards Turkey by strong westerly winds. In contrast, positive EAWR is mainly connected to cold nights over Black Sea (r = 0.6) and Aegean regions (r = 0.6) together with positive precipitation anomalies at the seaside stations of the eastern Black Sea region. On the other hand, when positive EAWR prevails, Azores high-pressure center expands towards continental Europe bringing cold air by strong northerly winds together with higher moisture transport from the Black Sea. These results could pave the way for new possibilities regarding the projection of extremes in downscaling techniques.

US surface ozone extremes and trends over 1980-2015: Quantifying the roles of rising Asian emissions, wildfires, biosphere-atmosphere couplings, and climate

NASA Astrophysics Data System (ADS)

Lin, M.; Horowitz, L. W.; Payton, R.; Fiore, A. M.; Tonnesen, G.

2017-12-01

US surface O3 responds to varying global-to-regional precursor emissions, climate, extreme heat and drought, with implications for designing effective air quality control policies. We examine these conjoined processes with observations and global chemistry-climate model (GFDL-AM3) hindcasts over 1980-2015. The model captures the salient features of observed trends in daily maximum 8-hour average O3: (1) springtime increases at western US (WUS) rural sites (0.2-0.5 ppb yr-1), (2) summertime decreases, largest at the 95th percentile, and (3) wintertime increases in the 50th to 5th percentiles over the eastern US (EUS). Many prior studies show that models have difficulty simulating O3 increases observed at remote sites. We reconcile observed and simulated O3 trends with a baseline sampling approach. Asian NOx emissions tripled since 1990, contributing as much as 65% to modeled springtime background O3 increases (0.3-0.5 ppb yr-1) over the WUS, outpacing O3 decreases attained via 50% US NOx emission controls. Notably, springtime O3 in Denver has increased at a rate similar to remote rural sites. During summer, wildfire emissions can enhance monthly mean O3 at individual sites by 2-8 ppb. However, the observed interannual correlation between O3 and wildfires reflects common underlying correlation with temperature rather than a causal relationship of fire with O3. Over the EUS, our model captures the observed O3 enhancements during the summer heat waves of 1995, 1999, 2011 and 2012. However, O3 deposition sink to vegetation must be reduced by 35% for the model to match observed O3 anomalies during the severe drought of 1988. Droughts can promote stomatal closure in plant leaves and reduce O3 deposition sink to vegetation, leading to an increase in surface O3 concentrations. Regional NOx reductions alleviated the O3 buildup during the recent heat waves of 2011 and 2012 relative to the earlier heat waves of 1988 and 1995. The O3 decreases driven by NOx controls were more pronounced in the Southeast US, where the seasonal onset of biogenic isoprene emissions and NOx-sensitive O3 production occurs earlier than in the Northeast. Without emission controls, the 95th percentile summertime O3 in the EUS would have increased by 0.2-0.4 ppb yr-1 over 1988-2014 due to more frequent hot extremes and rising biogenic isoprene emissions.

Radical observations during the Clean air for London project

NASA Astrophysics Data System (ADS)

Whalley, L. K.; Stone, D.; Clancy, N.; Lee, J. D.; Laufs, S.; Kleffmann, J.; Heard, D. E.

2012-12-01

With greater than 50 % of the global population residing in urban conurbations, poor urban air quality has a demonstrable effect on human health. OH and HO2 radicals, (collectively termed HOx) together with RO2 radicals, mediate virtually all of the oxidative chemistry in the atmosphere, being responsible for the transformation of primary emissions into secondary pollutants such as NO2, O3 and particulates. Understanding the chemistry of free-radicals in the atmosphere is essential in improving predictions of the lifetimes of pollutants and spatial scales of their transport within urban areas. Results from earlier field campaigns in urban and polluted regions have demonstrated the significance of HONO photolysis and alkene ozonolysis in the production of HOx radicals. In many cases, however, measurements of HONO have not been made, reducing the ability to evaluate model successes for OH in these environments. Here we present measurements of OH, HO2, RO2 and OH reactivity taken during the wintertime (January - February, 2012) and summertime (July - August, 2012) as part of the Clean air for London (ClearfLo) project in London. RO2 was detected using a newly developed flow-reactor laser-induced fluorescence technique which is able to discriminate between HO2 and organic peroxy radicals [1]. Low concentrations of radicals were observed during the wintertime, midday [OH], [HO2] and [RO2] were ~ 0.04, 0.8 and 1.5 pptv respectively, comparable to observations of radicals at other urban locations in winter [2,3,4], and which displayed a negative correlation with NO concentrations. OH reactivity was high and largely tracked the diurnal profiles of NOx and CO, with the highest reactivity ~100 s-1 observed during the morning rush hour. Analysis of factors controlling OH concentrations during the wintertime suggests that the formation of OH from the photolysis of O3 and subsequent reaction of O(1D) with H2O is a minor contribution both under high and low NOx conditions owing to the low rate of photolysis experienced and instead OH from photolysis of HONO (measured during ClearfLo using the LOPAP technique) [5], ozonolysis of alkenes and the reaction of HO2 with NO dominated the oxidative capacity of this urban location. Summertime observations coincided with the London 2012 Olympics. During this observational period, a number of high pollution events were observed where meteorological conditions favoured sustained, elevated ozone production (peaking at 100 ppbv). Radical concentrations were elevated during these episodes, with [OH], [HO2] and [RO2] peaking at ~ 0.16, 14 and 10 pptv respectively. The influence of HO2 and RO2 radicals on ozone production during these episodes will be presented along with a comparison of factors influencing modelled radical concentrations during the summer and wintertime. [1] Fuchs, H. et al., Review of Scientific Instruments, 79, 084104, 2008 [2] Heard, D.E. et al., Geophysical Research Letters, 13, L18112, 2004 [3] Ren, X. et al., Atmospheric Environment, 40, S252-S263, 2006 [4] Kanaya, Y. et al., Journal of Geophysical Research - Atmospheres, 112, D21312, 2007 [5] Kleffmann, J. et al., Atmospheric Environment, 40, 3640-3652, 2006

Elevated Wintertime Ozone in Utah's Uinta Basin

NASA Astrophysics Data System (ADS)

Martin, R. S.; Moore, K. D.; Hill, S.; Harper, K.

2011-12-01

Seemingly anomalous elevated wintertime ozone (O3) levels were first observed in Wyoming's Upper Green River Basin (UGRB) in 2005 and have been recorded most in subsequent winters. While research continues, it has been hypothesized that the unacceptable levels are a unique combination of stagnant meteorology, enhanced insolation due to relatively high elevations and snow increased albedo, and abundant precursor sources owing to the region's recent rapid expansion of oil and gas exploration and production. The UGRB area has over 4,700 recorded gas/oil wells and sits mostly in rural Sublette County which has an estimated population of 7,925, an area of 12,644 km2, and a basin floor elevation around 2200 m asl, surrounded on three sides with mountains up to 4,200 km asl. Similarly, the Uinta Basin in northeastern Utah is a rural area prone to frequent low-level wintertime inversion episodes and persistent snow cover, with an expanding economy significantly based on gas and oil development and production (approximately 11,500 wells, with an estimated 17,000 more planned in the future years). The Basin lies primarily in Duchesne and Uintah Counties which have a combined population of approximately 51,200 and an area of about 19,982 km2. The floor of the Basin has a typical elevation around 1,560 m asl and is surrounded by mountains up to 4,120 m asl. Ambient measurements at four sites in the winter of 2009-2010 found many instances of ozone concentrations well above the current U.S. National Ambient Air Quality Standard (NAAQS; 75 ppb, 8-hr average, 4th highest value). To more fully characterize the behavior and geographical extent of the Uinta Basin's wintertime O3 issue, the Uintah Impact Mitigation Special Service District (UIMSSD) funded a study which included deploying 10 portable O3 monitors (2B Technologies, Inc., Model 205, Dual Beam) throughout the Basin. Furthermore, cooperative partners including the USEPA, BLM, UDAQ, NPS, and Golder Associates provided access to an additional six monitoring locations within the Basin. The sites were operated from late December 2010 through mid-March 2011. Several stagnant, inversion episodes and associated periods of Basin-wide elevated ozone were captured. The highest 1-hr O3 concentration observed was 149.0 ppb, with 12 of the total 16 sites recording 1-hr values greater than 100 ppb. Of the 16 sites, only four were found not to exceed the current NAAQS regulation. The highest 8-hr averaged concentration recorded was 139.1 ppb. However, the U.S. standards specify that an area is regulated at the 4th highest values and the maximum value under this criterion during the observed winter period was 121.6 ppb. Two sites exceeded the NAAQS 25 days over the three month observation period, while five other locations exceed the NAAQS between 18 and 22 times. The sites with the highest O3 concentrations and the greatest number of daily exceedances were generally associated with the highest density of known oil and/or gas well locations. The sites with the fewest number of exceedances were at higher elevations or geographically peripheral locations.

The Aleutian Low and Winter Climatic Conditions in the Bering Sea. Part I: Classification

NASA Astrophysics Data System (ADS)

Rodionov, S. N.; Overland, J. E.; Bond, N. A.

2005-01-01

The Aleutian low is examined as a primary determinant of surface air temperature (SAT) variability in the Bering Sea during the winter (December-January-February-March (DJFM)) months. The Classification and Regression Tree (CART) method is used to classify five types of atmospheric circulation for anomalously warm months (W1-W5) and cold months (C1-C5). For the Bering Sea, changes in the position of the Aleutian low are shown to be more important than changes in its central pressure. The first two types, W1 and C1, account for 51% of the "warm" and 37% of the "cold" months. The W1-type pattern is characterized by the anomalously deep Aleutian low shifted west and north of its mean position. In this situation, an increased cyclonic activity occurs in the western Bering Sea. The C1-type pattern represents a split Aleutian low with one center in the northwestern Pacific and the other in the Gulf of Alaska. The relative frequency of the W1 to C1 types of atmospheric circulation varies on decadal time scales, which helps to explain the predominance of fluctuations on these time scales in the weather of the Bering Sea. Previous work has noted the prominence of multidecadal variability in the North Pacific. The present study finds multidecadal variations in frequencies of the W3 and C3 patterns, both of which are characterized by increased cyclonic activity south of 51°N. In general, the CART method is found to be a suitable means for characterizing the wintertime atmospheric circulation of the North Pacific in terms of its impact on the Bering Sea. The results show that similar pressure anomaly patterns for the North Pacific as a whole can actually result in different conditions for the Bering Sea, and that similar weather conditions in the Bering Sea can arise from decidedly different large-scale pressure patterns.

Effects of sea-ice and biogeochemical processes and storms on under-ice water fCO2 during the winter-spring transition in the high Arctic Ocean: Implications for sea-air CO2 fluxes

NASA Astrophysics Data System (ADS)

Fransson, Agneta; Chierici, Melissa; Skjelvan, Ingunn; Olsen, Are; Assmy, Philipp; Peterson, Algot K.; Spreen, Gunnar; Ward, Brian

2017-07-01

We performed measurements of carbon dioxide fugacity (fCO2) in the surface water under Arctic sea ice from January to June 2015 during the Norwegian young sea ICE (N-ICE2015) expedition. Over this period, the ship drifted with four different ice floes and covered the deep Nansen Basin, the slopes north of Svalbard, and the Yermak Plateau. This unique winter-to-spring data set includes the first winter-time under-ice water fCO2 observations in this region. The observed under-ice fCO2 ranged between 315 µatm in winter and 153 µatm in spring, hence was undersaturated relative to the atmospheric fCO2. Although the sea ice partly prevented direct CO2 exchange between ocean and atmosphere, frequently occurring leads and breakup of the ice sheet promoted sea-air CO2 fluxes. The CO2 sink varied between 0.3 and 86 mmol C m-2 d-1, depending strongly on the open-water fractions (OW) and storm events. The maximum sea-air CO2 fluxes occurred during storm events in February and June. In winter, the main drivers of the change in under-ice water fCO2 were dissolution of CaCO3 (ikaite) and vertical mixing. In June, in addition to these processes, primary production and sea-air CO2 fluxes were important. The cumulative loss due to CaCO3 dissolution of 0.7 mol C m-2 in the upper 10 m played a major role in sustaining the undersaturation of fCO2 during the entire study. The relative effects of the total fCO2 change due to CaCO3 dissolution was 38%, primary production 26%, vertical mixing 16%, sea-air CO2 fluxes 16%, and temperature and salinity insignificant.

Water Quality and optical properties of Crater Lake, Oregon

USGS Publications Warehouse

Larson, Gary L.; Hoffman, Robert L.; McIntire, C.D.; Buktenica, M.W.; Girdner, Scott

2007-01-01

We examine observations of key limnological properties (primarily temperature, salinity, and dissolved oxygen), measured over a 14-year period in Crater Lake, Oregon, and discuss variability in the hypolimnion on time scales of days to a decade. During some years (e.g., 1994a??1995), higher-than-average wintertime deep convection and ventilation led to the removal of significant amounts of heat and salt from the hypolimnion, while dissolved oxygen concentrations increase. In other years, such as the winter of 1996a??1997, heat and salt concentrations increase throughout the year and dissolved oxygen levels drop, indicating conditions were dominated by the background geothermal inputs and dissolved oxygen consumption by bacteria (i.e., minimal deep convection). Over the entire 14 year period, no statistically significant trend was observed in the annual hypolimnetic heat and salt content. Measurements from several thermistors moored in the hypolimnion provide new insight into the time and space scales of the deep convection events. For some events, cool water intrusions are observed sequentially, from shallower depths to deeper depths, suggesting vertical mixing or advection from above. For other events, the cooling is observed first at the deepest sensors, suggesting a thin, cold water pulse that flows along the bottom and mixes more slowly upwards into the basin. In both cases, the source waters must originate from the epilimnion. Conditions during a strong ventilation year (1994a??1995) and a weak ventilation year (1996a??1997) were compared. The results suggest the major difference between these 2 years was the evolution of the stratification in the epilimnion during the first few weeks of reverse stratification such that thermobaric instabilities were easier to form during 1995 thana?#1997. Thus, the details of surface cooling and wind-driven mixing during the early stages ofa?#reverse stratification may determine the neta?#amount of ventilation possible during a particular year.

Photochemical aging of volatile organic compounds associated with oil and natural gas extraction in the Uintah Basin, UT, during a wintertime ozone formation event

NASA Astrophysics Data System (ADS)

Koss, A. R.; de Gouw, J.; Warneke, C.; Gilman, J. B.; Lerner, B. M.; Graus, M.; Yuan, B.; Edwards, P.; Brown, S. S.; Wild, R.; Roberts, J. M.; Bates, T. S.; Quinn, P. K.

2015-05-01

High concentrations of volatile organic compounds (VOCs) associated with oil and natural gas extraction were measured during a strong temperature inversion in the winter of 2013 at a rural site in the Uintah Basin, Utah. During this period, photochemistry enhanced by the stagnant meteorological conditions and concentrated VOCs led to high ozone mixing ratios (150 ppbv). A simple analysis of aromatic VOCs measured by proton-transfer-reaction mass-spectrometry (PTR-MS) is used to estimate (1) VOC emission ratios (the ratio of two VOCs at the time of emission) relative to benzene, (2) aromatic VOC emission rates, and (3) ambient OH radical concentrations. These quantities are determined from a best fit to VOC : benzene ratios as a function of time. The main findings are that (1) emission ratios are consistent with contributions from both oil and gas producing wells; (2) the emission rate of methane (27-57 x 103 kg methane h-1), extrapolated from the emission rate of benzene (4.1 ± 0.4 x 105 molecules cm-3 s-1), agrees with an independent estimate of methane emissions from aircraft measurements in 2012; and (3) calculated daily OH concentrations are low, peaking at 1 x 106 molecules cm-3, and are consistent with Master Chemical Mechanism (MCM) modeling. The analysis is extended to photochemical production of oxygenated VOCs measured by PTR-MS and is able to explain daytime variability of these species. It is not able to completely reproduce nighttime behavior, possibly due to surface deposition. Using results from this analysis, the carbon mass of secondary compounds expected to have formed by the sixth day of the stagnation event was calculated, then compared to the measured mass of primary and secondary compounds. Only 17% of the expected secondary carbon mass is accounted for by gas phase, aerosol, and snow organic carbon measurements. The disparity is likely due to substantial amounts of unquantified oxygenated products.

Photochemical aging of volatile organic compounds associated with oil and natural gas extraction in the Uintah Basin, UT, during a wintertime ozone formation event

NASA Astrophysics Data System (ADS)

Koss, A. R.; de Gouw, J.; Warneke, C.; Gilman, J. B.; Lerner, B. M.; Graus, M.; Yuan, B.; Edwards, P.; Brown, S. S.; Wild, R.; Roberts, J. M.; Bates, T. S.; Quinn, P. K.

2015-03-01

High concentrations of volatile organic compounds (VOCs) associated with oil and natural gas extraction were measured during a strong temperature inversion in winter of 2013 at a rural site in the Uintah Basin, Utah. During this period, photochemistry enhanced by the stagnant meteorological conditions and concentrated VOCs led to high ozone mixing ratios (150 ppbv). A simple analysis of aromatic VOCs measured by proton-transfer-reaction mass-spectrometry (PTR-MS) is used to estimate (1) VOC emission ratios (the ratio of two VOCs at the time of emission) relative to benzene, (2) aromatic VOC emission rates, and (3) ambient OH radical concentrations. These quantities are determined from a best fit to VOC : benzene ratios as a function of time. The main findings are that (1) emission ratios are consistent with contributions from both oil and gas producing wells, (2) the emission rate of methane (27-57 × 103 kg methane h-1), extrapolated from the emission rate of benzene (4.1 ± 0.4 × 105 molecules cm-3 s-1), agrees with an independent estimate of methane emissions from aircraft measurements in 2012, and (3) calculated daily OH concentrations are low, peaking at 1× 106 molecules cm-3, and are consistent with Master Chemical Mechanism (MCM) modeling. The analysis is extended to photochemical production of oxygenated VOCs measured by PTRMS and is able to explain daytime variability of these species. It is not able to completely reproduce nighttime behavior, possibly due to surface deposition. Using results from this analysis, the carbon mass of secondary compounds expected to have formed by the sixth day of the stagnation event was calculated, then compared to the measured mass of primary and secondary compounds. Only 17% of the expected secondary carbon mass is accounted for by gas phase, aerosol, and snow organic carbon measurements. The disparity is likely due to substantial amounts of unquantified oxygenated products.

Process-scale modeling of elevated wintertime ozone in Wyoming.

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

Kotamarthi, V. R.; Holdridge, D. J.; Environmental Science Division

2007-12-31

Measurements of meteorological variables and trace gas concentrations, provided by the Wyoming Department of Environmental Quality for Daniel, Jonah, and Boulder Counties in the state of Wyoming, were analyzed for this project. The data indicate that highest ozone concentrations were observed at temperatures of -10 C to 0 C, at low wind speeds of about 5 mph. The median values for nitrogen oxides (NOx) during these episodes ranged between 10 ppbv and 20 ppbv (parts per billion by volume). Measurements of volatile organic compounds (VOCs) during these periods were insufficient for quantitative analysis. The few available VOCs measurements indicated unusuallymore » high levels of alkanes and aromatics and low levels of alkenes. In addition, the column ozone concentration during one of the high-ozone episodes was low, on the order of 250 DU (Dobson unit) as compared to a normal column ozone concentration of approximately 300-325 DU during spring for this region. Analysis of this observation was outside the scope of this project. The data analysis reported here was used to establish criteria for making a large number of sensitivity calculations through use of a box photochemical model. Two different VOCs lumping schemes, RACM and SAPRC-98, were used for the calculations. Calculations based on this data analysis indicated that the ozone mixing ratios are sensitive to (a) surface albedo, (b) column ozone, (c) NOx mixing ratios, and (d) available terminal olefins. The RACM model showed a large response to an increase in lumped species containing propane that was not reproduced by the SAPRC scheme, which models propane as a nearly independent species. The rest of the VOCs produced similar changes in ozone in both schemes. In general, if one assumes that measured VOCs are fairly representative of the conditions at these locations, sufficient precursors might be available to produce ozone in the range of 60-80 ppbv under the conditions modeled.« less

Evaluation of Surface Fatigue Strength Based on Surface Temperature

NASA Astrophysics Data System (ADS)

Deng, Gang; Nakanishi, Tsutomu

Surface temperature is considered to be an integrated index that is dependent on not only the load and the dimensions at the contact point but also the sliding velocity, rolling velocity, surface roughness, and lubrication conditions. Therefore, the surface durability of rollers and gears can be evaluated more exactly and simply by the use of surface temperature rather than Hertzian stress. In this research, surface temperatures of rollers under different rolling and sliding conditions are measured using a thermocouple. The effects of load P, mean velocity Vm and sliding velocity Vs on surface temperature are clarified. An experimental formula, which expresses the linear relationship between surface temperature and the P0.86Vs1.31Vm-0.83 value, is used to determine surface temperature. By comparing calculated and measured temperature on the tooth surface of a gear, this formula is confirmed to be applicable for gear tooth surface temperature calculation.

Eye surface temperature detects stress response in budgerigars (Melopsittacus undulatus).

PubMed

Ikkatai, Yuko; Watanabe, Shigeru

2015-08-05

Previous studies have suggested that stressors not only increase body core temperature but also body surface temperature in many animals. However, it remains unclear whether surface temperature could be used as an alternative to directly measure body core temperature, particularly in birds. We investigated whether surface temperature is perceived as a stress response in budgerigars. Budgerigars have been used as popular animal models to investigate various neural mechanisms such as visual perception, vocal learning, and imitation. Developing a new technique to understand the basic physiological mechanism would help neuroscience researchers. First, we found that cloacal temperature correlated with eye surface temperature. Second, eye surface temperature increased after handling stress. Our findings suggest that eye surface temperature is closely related to cloacal temperature and that the stress response can be measured by eye surface temperature in budgerigars.

Wintertime nitric acid chemistry - Implications from three-dimensional model calculations

NASA Technical Reports Server (NTRS)

Rood, Richard B.; Kaye, Jack A.; Douglass, Anne R.; Allen, Dale J.; Steenford, Stephen

1990-01-01

A three-dimensional simulation of the evolution of HNO3 has been run for the winter of 1979. Winds and temperatures are taken from a stratospheric data assimilation analysis, and the chemistry is based on Limb Infrared Monitor of the Stratosphere (LIMS) observations. The model is compared to LIMS observations to investigate the problem of 'missing' nitric acid chemistry in the winter hemisphere. Both the model and observations support the contention that a nitric acid source is needed outside of the polar vortex and north of the subtropics. Observations suggest that HNO3 is not dynamically controlled in middle latitudes. The model shows that given the time scales of conventional chemistry, dynamical control is expected. Therefore, an error exists in the conventional chemistry or additional processes are needed to bring the model and data into agreement. Since the polar vortex is dynamically isolated from the middle latitudes, and since the highest HNO3 values are observed in October and November, a source associated solely with polar stratospheric clouds cannot explain the deficiencies in the chemistry. The role of heterogeneous processes on background aerosols is reviewed in light of these results.

Variability of IN measured with the Fast Ice Nucleus Chamber (FINCH) at the high altitude research station Jungfraujoch during wintertime 2013

NASA Astrophysics Data System (ADS)

Frank, Fabian; Nillius, Björn; Bundke, Ulrich; Curtius, Joachim

2014-05-01

Ice nuclei (IN) are an important component of the atmospheric aerosol. Despite their low concentrations in the atmosphere, they have an influence on the formation of ice crystals in mixed-phase clouds and therefore on precipitation. The Fast Ice Nucleus CHamber (FINCH)1, a counter for ice nucleating particles developed at the Goethe University Frankfurt am Main allows long-term measurements of the IN number concentration. In FINCH the ice activation of the aerosol particles is achieved by mixing air flows with different temperature and humidity. The IN number concentration measurements at different meteorological conditions during the INUIT-JFJ campaign at the high altitude research station Jungfraujoch in Switzerland are presented and its variability are discussed. The good operational performance of the instrument allowed up to 10 hours of continuous measurements. Acknowledgment: This work was supported by the German Research Foundation, DFG Grant: BU 1432/3-2 BU 1432/4-1 in the framework of INUIT (FOR 1525) and SPP 1294 HALO. 1- Bundke, U., Nillius, B., Jaenicke, R., Wetter, T., Klein, H., and Bingemer, H. (2008). The fast ice nucleus chamber finch. Atmospheric Research, 90:180-186.

Convective Influence and Transport Pathways Controlling the Tropical Distribution of Carbon Monoxide at 100 Hpa

NASA Technical Reports Server (NTRS)

Jensen, Eric; Bergman, John; Pfister, Leonard; Ueyama, Rei; Kinnison, Doug

2014-01-01

Trajectory calculations with convective influence diagnosed from geostationary-satellite cloud measurements are used to evaluate the relative importance of different Tropical Tropopause Layer (TTL) transport pathways for establishing the distribution of carbon monoxide (CO) at 100 hPa as observed by the Microwave Limb Sounder (MLS) on board the Aura satellite. Carbon monoxide is a useful tracer for investigating TTL transport and convective influence because the CO lifetime is comparable to the time require for slow ascent through the TTL (a couple of months). Offline calculations of TTL radiative heating are used to determine the vertical motion field. The simple trajectory model does a reasonable job of reproducing the MLS CO distributions during Boreal wintertime and summertime. The broad maximum in CO concentration over the Pacific is primarily a result of the strong radiative heating (indicating upward vertical motion) associated with the abundant TTL cirrus in this region. Sensitivity tests indicate that the distinct CO maximum in the Asian monsoon anticyclone is strongly impacted by extreme convective systems with detrainment of polluted air above 360 K potential temperature. The relative importance of different CO source regions will also be discussed.

Fog Chemistry at Different Altitudes in the Swiss Alps

NASA Astrophysics Data System (ADS)

Michna, P.; Eugster, W.; Wanner, H.

2010-07-01

During two extended summer seasons in 2006 and 2007, we installed two battery driven versions of the Caltech active strand cloud water collector (MiniCASCC) at the Niesen mountain in the northern Swiss Alps. Along, we measured air temperature, relative humidity, wind, and visibility. During these two field operation phases we gained weekly samples of fogwater, where we analysed the major anions and cations, and the stable water isotopes δD and δ18O. The fog collectors were installed at an altitude of 2300 and 1600 m asl to resolve altitudinal differences in fog chemistry. We found a large variability between the events, but no clear altitudinal gradient. At both sites, the most important ions were nitrate, ammonium, and sulphate. Higher concentrations occured preferably in late spring (start of sampling period) and in autumn (end of sampling). Compared to previous studies at lower elevations in the Swiss Plateau during wintertime, our measurements showed considerable lower ion loads in the fogwater. The combination of these results suggest that lowest ion loads are found in convective clouds with a short lifetime and that the highest ion loads occur during radiation fog events at lower elevations.

Weather Effects on Crop Diseases in Eastern Germany

NASA Astrophysics Data System (ADS)

Conradt, Tobias

2017-04-01

Since the 1970s there are several long-term monitoring programmes for plant diseases and pests in Germany. Within the framework of a national research project, some otherwise confidential databases comprising 77 111 samples from numerous sites accross Eastern Germany could be accessed and analysed. The pest data covered leaf rust (Puccinia triticina) and powdery mildew (Blumeria graminis) in winter wheat, aphids (Aphididae, four genera) on wheat and other cereal crops, late blight (Phytophthora infestans) in potatoes, and pollen beetles (Brassicogethes aeneus) on rape. These data were complemented by daily weather observations from the German Weather Service (DWD). In a first step, Pearson correlations between weather variables and pest frequencies were calculated for seasonal time periods of different start months and durations and ordered into so-called correlograms. This revealed principal weather effects on disease spread - e. g. that wind is favourable for mildew throughout the year or that rape pollen beetles like it warm, but not during wintertime. Secondly, the pest frequency samples were found to resemble gamma distributions, and a generalised linear model was fitted to describe their parameter shift depending on end-of-winter temperatures for aphids on cereals. The method clearly shows potential for systematic pest risk assessments regarding climate change.

Detection of Northern Hemisphere Transient Baroclinic Eddies in REMS Pressure Data at Gale Crater Mars

NASA Astrophysics Data System (ADS)

Haberle, Robert; Kahre, Melinda A.; De la Torre, Manuel; Kass, David M.; Mars Science Laboratory Science Team

2016-10-01

Wintertime transient baroclinic eddies in the northern midlatitudes of Mars were identified in Viking Lander 2 (VL2, 48.3N, 134.0E) surface pressure data back in the early 1980s. Here we report the results of an analysis of REMS surface pressure data acquired by the Curiosity Rover in Gale Crater (4.5S, 137.4E) that suggests the meridional scale of these eddies is so large that the disturbances in the surface pressure fields they create extend across the equator and into the southern hemisphere. A power spectrum analysis of the seasonally detrended REMS pressure data from Ls=240-280 shows dominant periods of ~ 6 sols and ~2.2 sols (though with greatly reduced power) which are close the dominant periods of the transient eddies observed by VL2 at this season. Analysis of the surface pressure fields from the Ames Mars GCM for the same season also shows dominant periods at the grid points closest to VL2 and Gale Crater similar to those observed. In the model, the disturbances responsible for these oscillations are eastward traveling baroclinic eddies whose amplitudes are greatest at northern mid latitudes at this season, but whose meridional extent does indeed extend into the low latitudes of the southern hemisphere. REMS appears to be seeing the signature of these eddies, not only for this season but for the early fall and late winter seasons as well. While orbital images of the so called "flushing storms", which more closely correspond to the shorter period waves, show dust-lifting frontal systems that cross the equator, REMS data - even though acquired at a longitude of comparatively weak storm activity - provide the first in-situ evidence that northern hemisphere transient eddies can be detected at the surface in low latitudes of the southern hemisphere.

An Ice Core Perspective on Aleutian Low Variability over the Common Era

NASA Astrophysics Data System (ADS)

Osterberg, E. C.; Winski, D.; Kreutz, K. J.; Wake, C. P.; Ferris, D. G.; Campbell, S.; Introne, D.

2016-12-01

The Aleutian Low (ALow) is the dominant feature of atmospheric circulation in the North Pacific, strongly influencing wintertime temperature, precipitation and wind patterns in Alaska and the Yukon Territory, as well as further downstream in North America via atmospheric teleconnections. Changes in ALow strength are known to impact marine ecosystems by contributing to the multi-decadal sea-surface temperature mode in the North Pacific known as the Pacific Decadal Oscillation (PDO). Meteorological records show that in addition to distinct PDO-like variability, the ALow has intensified over the 20th century. However, ALow variability prior to the instrumental period remains unclear due to generally poor correlations among published ALow and PDO reconstructions, including the Mt. Logan ice core ALow record. An improved understanding of past ALow variability is critical for evaluating natural ALow forcing mechanisms, placing the 20th century intensification in context, and improving ALow projections under increased anthropogenic forcing. Here we combine ALow-sensitive time series from the new Denali ice core and the Mt. Logan ice core to develop a high-resolution (1-3 year) multi-ice-core record of ALow variability over the past 1500 years. The Denali ice core was collected from the summit plateau (3900 m) of Mt. Hunter in 2013, and was sampled using the Dartmouth continuous melter system with discrete sampling for major ion (IC), trace element (ICP-MS), and stable isotope ratios (Picarro), as well as continuous flow analyses for dust size and concentration (Klotz Abakus). We focus here on the sea-salt sodium time series, and calibrate our record over the 20th century with reanalysis wind speed and pressure data. The Denali sodium record of ALow strength strongly resembles the Mt. Logan ALow record, with both showing a recent intensification of the ALow that started in the late 1600s and continues into the 20th century. Both records reveal that the ALow was stronger during the late 19th to 20th centuries than earlier in the last millennium, and both show a previous strong ALow period from ca. 500-900 AD. We compare our mutli-core ALow record to other ALow-sensitive ice core time series, as well as to ALow records from other proxy archives and General Circulation Models.

Increased wintertime CO2 loss as a result of sustained tundra warming

NASA Astrophysics Data System (ADS)

Webb, Elizabeth E.; Schuur, Edward A. G.; Natali, Susan M.; Oken, Kiva L.; Bracho, Rosvel; Krapek, John P.; Risk, David; Nickerson, Nick R.

2016-02-01

Permafrost soils currently store approximately 1672 Pg of carbon (C), but as high latitudes warm, this temperature-protected C reservoir will become vulnerable to higher rates of decomposition. In recent decades, air temperatures in the high latitudes have warmed more than any other region globally, particularly during the winter. Over the coming century, the arctic winter is also expected to experience the most warming of any region or season, yet it is notably understudied. Here we present nonsummer season (NSS) CO2 flux data from the Carbon in Permafrost Experimental Heating Research project, an ecosystem warming experiment of moist acidic tussock tundra in interior Alaska. Our goals were to quantify the relationship between environmental variables and winter CO2 production, account for subnivean photosynthesis and late fall plant C uptake in our estimate of NSS CO2 exchange, constrain NSS CO2 loss estimates using multiple methods of measuring winter CO2 flux, and quantify the effect of winter soil warming on total NSS CO2 balance. We measured CO2 flux using four methods: two chamber techniques (the snow pit method and one where a chamber is left under the snow for the entire season), eddy covariance, and soda lime adsorption, and found that NSS CO2 loss varied up to fourfold, depending on the method used. CO2 production was dependent on soil temperature and day of season but atmospheric pressure and air temperature were also important in explaining CO2 diffusion out of the soil. Warming stimulated both ecosystem respiration and productivity during the NSS and increased overall CO2 loss during this period by 14% (this effect varied by year, ranging from 7 to 24%). When combined with the summertime CO2 fluxes from the same site, our results suggest that this subarctic tundra ecosystem is shifting away from its historical function as a C sink to a C source.

On the Evolution of Precipitation Associated with a Wintertime East Coast Cyclone: A GALE Preliminary Study.

DTIC Science & Technology

1985-01-01

CYCLES (CYCLone Extratropical Storms project), a more elaborate study of precipitation structure, has been carried out by Hobbs and his collaborators...toward the heavily populated northeast portion of the country. The disruption of human activity caused by these often poorly forecast storms is...daily synoptic maps over a century ago permitted analysis of the structure and behavior of extratropical cyclones. Since then considerable literature

NASA Astrophysics Data System (ADS)

2018-01-01

The test dataset was also useful to compare visual range estimates carried out by the Koschmieder equation and visibility measured at the Milano-Linate airport. It is worthy to note that in this work the test dataset was used primarily for checking the proposed methodology and it was not meant to give an assessment of bext and VR in Milan for a wintertime period as done by Vecchi et al., [in press], who applied the tailored equation to a larger aerosol dataset.

The EUSTACE project: delivering global, daily information on surface air temperature

NASA Astrophysics Data System (ADS)

Rayner, Nick

2017-04-01

Day-to-day variations in surface air temperature affect society in many ways; however, daily surface air temperature measurements are not available everywhere. A global daily analysis cannot be achieved with measurements made in situ alone, so incorporation of satellite retrievals is needed. To achieve this, in the EUSTACE project (2015-June 2018, https://www.eustaceproject.eu) we are developing an understanding of the relationships between traditional (land and marine) surface air temperature measurements and retrievals of surface skin temperature from satellite measurements, i.e. Land Surface Temperature, Ice Surface Temperature, Sea Surface Temperature and Lake Surface Water Temperature. Here we discuss the science needed to produce a fully-global daily analysis (or ensemble of analyses) of surface air temperature on the centennial scale, integrating different ground-based and satellite-borne data types. Information contained in the satellite retrievals is used to create globally-complete fields in the past, using statistical models of how surface air temperature varies in a connected way from place to place. As the data volumes involved are considerable, such work needs to include development of new "Big Data" analysis methods. We will present recent progress along this road in the EUSTACE project: 1. providing new, consistent, multi-component estimates of uncertainty in surface skin temperature retrievals from satellites; 2. identifying inhomogeneities in daily surface air temperature measurement series from weather stations and correcting for these over Europe; 3. estimating surface air temperature over all surfaces of Earth from surface skin temperature retrievals; 4. using new statistical techniques to provide information on higher spatial and temporal scales than currently available, making optimum use of information in data-rich eras. Information will also be given on how interested users can become involved.

The EUSTACE project: delivering global, daily information on surface air temperature

NASA Astrophysics Data System (ADS)

Ghent, D.; Rayner, N. A.

2016-12-01

Day-to-day variations in surface air temperature affect society in many ways; however, daily surface air temperature measurements are not available everywhere. A global daily analysis cannot be achieved with measurements made in situ alone, so incorporation of satellite retrievals is needed. To achieve this, in the EUSTACE project (2015-June 2018, https://www.eustaceproject.eu) we are developing an understanding of the relationships between traditional (land and marine) surface air temperature measurements and retrievals of surface skin temperature from satellite measurements, i.e. Land Surface Temperature, Ice Surface Temperature, Sea Surface Temperature and Lake Surface Water Temperature. Here we discuss the science needed to produce a fully-global daily analysis (or ensemble of analyses) of surface air temperature on the centennial scale, integrating different ground-based and satellite-borne data types. Information contained in the satellite retrievals is used to create globally-complete fields in the past, using statistical models of how surface air temperature varies in a connected way from place to place. As the data volumes involved are considerable, such work needs to include development of new "Big Data" analysis methods. We will present recent progress along this road in the EUSTACE project, i.e.: • providing new, consistent, multi-component estimates of uncertainty in surface skin temperature retrievals from satellites; • identifying inhomogeneities in daily surface air temperature measurement series from weather stations and correcting for these over Europe; • estimating surface air temperature over all surfaces of Earth from surface skin temperature retrievals; • using new statistical techniques to provide information on higher spatial and temporal scales than currently available, making optimum use of information in data-rich eras. Information will also be given on how interested users can become involved.

The Passy-2015 field experiment: wintertime atmospheric dynamics and air quality in a narrow alpine valley

NASA Astrophysics Data System (ADS)

Paci, Alexandre; Staquet, Chantal

2016-04-01

Wintertime anticyclonic conditions lead to the formation of persistent stable boundary layers which may induce severe air pollution episodes in urban or industrialized area, particularly in mountain regions. The Arve river valley in the Northern Alps is very sensitive to this phenomenon, in particular close to the city of Passy (Haute-Savoie), 20 km down valley past Chamonix. This place is indeed one of the worst place in France regarding air quality, the concentration of fine particles and Benzo(a)pyrene (a carcinogenic organic compound) regularly exceeding the EU legal admissible level during winter. Besides air quality measurements, such as the ones presently carried in the area by the local air quality agency Air Rhône-Alpes or in the DECOMBIO project led by LGGE, it is crucial to improve our knowledge of the atmospheric boundary layer dynamics and processes at the valley scale under these persistent stable conditions in order to improve our understanding on how it drives pollutant dispersion. These issues motivated the Passy-2015 field experiment which took place during the winter 2014-2015. A relatively large set-up of instruments was deployed on a main measurement site in the valley center and on four other satellite sites. It includes several remote sensing instruments, a surface flux station, a 10 m instrumented tower, a large aperture scintillometer, a fog monitoring station among others. Most of the instruments were present from early January to the end of February. During two intensive observation periods, 6-14 February and 17-20 February, the instrumental set-up was completed on the main site with high frequency radio-soundings (up to one per 1h30), a tethered balloon, a remote controlled drone quadcopter and a sodar. The field campaign, the instruments, the meteorological situations observed and preliminary results will be presented. This field experiment is part of the Passy project funded by ADEME through the French national programme LEFE/INSU and by METEO FRANCE. The project involves teams from Air Rhône-Alpes, CNRM-GAME, LEGI, LGGE, LTHE and NCAS (UK). The field experiment was led by CNRM-GAME while LEGI is the principal investigator of the LEFE project.

A multi-model evaluation of aerosols over South Asia: common problems and possible causes

NASA Astrophysics Data System (ADS)

Pan, X.; Chin, M.; Gautam, R.; Bian, H.; Kim, D.; Colarco, P. R.; Diehl, T. L.; Takemura, T.; Pozzoli, L.; Tsigaridis, K.; Bauer, S.; Bellouin, N.

2015-05-01

Atmospheric pollution over South Asia attracts special attention due to its effects on regional climate, water cycle and human health. These effects are potentially growing owing to rising trends of anthropogenic aerosol emissions. In this study, the spatio-temporal aerosol distributions over South Asia from seven global aerosol models are evaluated against aerosol retrievals from NASA satellite sensors and ground-based measurements for the period of 2000-2007. Overall, substantial underestimations of aerosol loading over South Asia are found systematically in most model simulations. Averaged over the entire South Asia, the annual mean aerosol optical depth (AOD) is underestimated by a range 15 to 44% across models compared to MISR (Multi-angle Imaging SpectroRadiometer), which is the lowest bound among various satellite AOD retrievals (from MISR, SeaWiFS (Sea-Viewing Wide Field-of-View Sensor), MODIS (Moderate Resolution Imaging Spectroradiometer) Aqua and Terra). In particular during the post-monsoon and wintertime periods (i.e., October-January), when agricultural waste burning and anthropogenic emissions dominate, models fail to capture AOD and aerosol absorption optical depth (AAOD) over the Indo-Gangetic Plain (IGP) compared to ground-based Aerosol Robotic Network (AERONET) sunphotometer measurements. The underestimations of aerosol loading in models generally occur in the lower troposphere (below 2 km) based on the comparisons of aerosol extinction profiles calculated by the models with those from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) data. Furthermore, surface concentrations of all aerosol components (sulfate, nitrate, organic aerosol (OA) and black carbon (BC)) from the models are found much lower than in situ measurements in winter. Several possible causes for these common problems of underestimating aerosols in models during the post-monsoon and wintertime periods are identified: the aerosol hygroscopic growth and formation of secondary inorganic aerosol are suppressed in the models because relative humidity (RH) is biased far too low in the boundary layer and thus foggy conditions are poorly represented in current models, the nitrate aerosol is either missing or inadequately accounted for, and emissions from agricultural waste burning and biofuel usage are too low in the emission inventories. These common problems and possible causes found in multiple models point out directions for future model improvements in this important region.

The EUSTACE project: delivering global, daily information on surface air temperature

NASA Astrophysics Data System (ADS)

Ghent, D.; Rayner, N. A.

2017-12-01

Day-to-day variations in surface air temperature affect society in many ways; however, daily surface air temperature measurements are not available everywhere. A global daily analysis cannot be achieved with measurements made in situ alone, so incorporation of satellite retrievals is needed. To achieve this, in the EUSTACE project (2015-2018, https://www.eustaceproject.eu) we have developed an understanding of the relationships between traditional (land and marine) surface air temperature measurements and retrievals of surface skin temperature from satellite measurements, i.e. Land Surface Temperature, Ice Surface Temperature, Sea Surface Temperature and Lake Surface Water Temperature. Here we discuss the science needed to produce a fully-global daily analysis (or ensemble of analyses) of surface air temperature on the centennial scale, integrating different ground-based and satellite-borne data types. Information contained in the satellite retrievals is used to create globally-complete fields in the past, using statistical models of how surface air temperature varies in a connected way from place to place. This includes developing new "Big Data" analysis methods as the data volumes involved are considerable. We will present recent progress along this road in the EUSTACE project, i.e.: • identifying inhomogeneities in daily surface air temperature measurement series from weather stations and correcting for these over Europe; • estimating surface air temperature over all surfaces of Earth from surface skin temperature retrievals; • using new statistical techniques to provide information on higher spatial and temporal scales than currently available, making optimum use of information in data-rich eras. Information will also be given on how interested users can become involved.

Differences between near-surface equivalent temperature and temperature trends for the Eastern United States. Equivalent temperature as an alternative measure of heat content

USGS Publications Warehouse

Davey, C.A.; Pielke, R.A.; Gallo, K.P.

2006-01-01

There is currently much attention being given to the observed increase in near-surface air temperatures during the last century. The proper investigation of heating trends, however, requires that we include surface heat content to monitor this aspect of the climate system. Changes in heat content of the Earth's climate are not fully described by temperature alone. Moist enthalpy or, alternatively, equivalent temperature, is more sensitive to surface vegetation properties than is air temperature and therefore more accurately depicts surface heating trends. The microclimates evident at many surface observation sites highlight the influence of land surface characteristics on local surface heating trends. Temperature and equivalent temperature trend differences from 1982-1997 are examined for surface sites in the Eastern U.S. Overall trend differences at the surface indicate equivalent temperature trends are relatively warmer than temperature trends in the Eastern U.S. Seasonally, equivalent temperature trends are relatively warmer than temperature trends in winter and are relatively cooler in the fall. These patterns, however, vary widely from site to site, so local microclimate is very important. ?? 2006 Elsevier B.V. All rights reserved.

An Examination of Intertidal Temperatures Through Remotely Sensed Satellite Observations

NASA Astrophysics Data System (ADS)

Lakshmi, V.

2010-12-01

MODIS Aqua and Terra satellites produce both land surface temperatures and sea surface temperatures using calibrated algorithms. In this study, the land surface temperatures were retrieved during clear-sky (non-cloudy) conditions at a 1 km2 resolution (overpass time at 10:30 am) whereas the sea surface temperatures are also retrieved during clear-sky conditions at approximately 4 km resolution (overpass time at 1:30 pm). The purpose of this research was to examine remotely sensed sea surface (SST), intertidal (IST), and land surface temperatures (LST), in conjunction with observed in situ mussel body temperatures, as well as associated weather and tidal data. In Strawberry Hill, Oregon, it was determined that intertidal surface temperatures are similar to but distinctly different from land surface temperatures although influenced by sea surface temperatures. The air temperature and differential heating throughout the day, as well as location in relation to the shore, can greatly influence the remotely sensed surface temperatures. Therefore, remotely sensed satellite data is a very useful tool in examining intertidal temperatures for regional climatic changes over long time periods and may eventually help researchers forecast expected climate changes and help determine associated biological implications.

Enhanced Ozone Production at Low Temperatures due to Ethanol (E85)

NASA Astrophysics Data System (ADS)

Ginnebaugh, D. L.; Livingstone, P. L.; Jacobson, M. Z.

2009-12-01

The increased use of ethanol in transportation fuels warrants an investigation of its consequences. An important component of such an investigation is the temperature-dependence of ethanol and gasoline exhaust chemistry. We use the near-explicit Master Chemical Mechanism (MCM, version 3.1, LEEDS University) with the SMVGEAR II chemical ordinary differential solver to provide the speed necessary to simulate explicit chemistry to examine such effects. The MCM has over 13,500 organic reactions and 4,600 species. SMVGEAR II is a sparse-matrix Gear solver that reduces the computation time significantly while maintaining any specified accuracy. Although for this study we use a box model, we determined that the speed of the MCM with the SMVGEAR solver will allow the MCM to be modeled in 3-dimensions. We also verified the accuracy of the model with comparisons to smog chamber data. We use species-resolved tailpipe emissions data for E85 (15% gasoline, 85% ethanol fuel blend) and gasoline vehicles to compare the impact of each on ozone and carcinogenic organic gases as a function of ambient temperature and background concentrations, using Los Angeles in 2020 as a base case. We use two different emissions sets - one is a compilation of data taken at near 24 C and the other from data taken at -7 C - to determine how atmospheric chemistry and emissions are affected by temperature. We include diurnal effects by examining 2 day and 5 day scenarios. We find that for both emission data sets, the average ozone concentrations through the range of temperatures tested are higher with E85 than with gasoline by 8 parts per billion volume (ppbv) at higher temperatures to 55 ppbv at low temperatures and low sunlight (winter conditions) for an area with a high nitrogen oxides (NOx) to non-methane organic gases (NMOG) ratio. The results suggest that E85's effect on health through ozone formation becomes increasingly more significant relative to gasoline as temperatures decreased due to the change in emission composition at lower temperature. This could have implications for the wintertime use of E85. Some carcinogenic species increase while others decrease when using E85 instead of gasoline, implying that the cancer risk is approximately the same for warmer temperatures but may be slightly higher for E85 for cold temperatures. Peroxy acetyl nitrate (PAN), another air pollutant of concern, increases with E85 by 0.4 to 20 ppbv. The sensitivity of the results to background emissions, NOx emissions, and water vapor was also examined.

The levels, variation characteristics, and sources of atmospheric non-methane hydrocarbon compounds during wintertime in Beijing, China

NASA Astrophysics Data System (ADS)

Liu, Chengtang; Ma, Zhuobiao; Mu, Yujing; Liu, Junfeng; Zhang, Chenglong; Zhang, Yuanyuan; Liu, Pengfei; Zhang, Hongxing

2017-09-01

Atmospheric non-methane hydrocarbon compounds (NMHCs) were measured at a sampling site in Beijing city from 15 December 2015 to 14 January 2016 to recognize their pollution levels, variation characteristics, and sources. We quantified 53 NMHCs, and the proportions of alkanes, alkenes, acetylene, and aromatics to the total NMHCs were 49.8-55.8, 21.5-24.7, 13.5-15.9, and 9.3-10.7 %, respectively. The variation trends in the NMHC concentrations were basically identical and exhibited remarkable fluctuation, which was mainly ascribed to the variation in meteorological conditions, especially wind speed. The diurnal variations in NMHCs on clear days exhibited two peaks during the morning and evening rush hours, whereas the rush hours' peaks diminished or even disappeared on the haze days, implying that the relative contribution of the vehicular emissions to atmospheric NMHCs depended on the pollution status. Two evident peaks of the propane / propene ratios appeared in the early morning before sun rise and at noontime on clear days, whereas only one peak occurred in the afternoon during the haze days, which were attributed to the relatively fast reactions of propene with OH, NO3, and O3. Based on the chemical kinetic equations, the daytime OH concentrations were calculated to be in the range of 3. 47 × 105-1. 04 × 106 molecules cm-3 on clear days and 6. 42 × 105-2. 35 × 106 molecules cm-3 on haze days. The nighttime NO3 concentrations were calculated to be in the range of 2. 82 × 109-4. 86 × 109 molecules cm-3 on clear days. The correlation coefficients of typical hydrocarbon pairs (benzene / toluene, o-xylene / m,p-xylene, isopentane / n-pentane, etc.) revealed that vehicular emissions and coal combustion were important sources for atmospheric NMHCs in Beijing during the wintertime. Five major emission sources for atmospheric NMHCs in Beijing during the wintertime were further identified by positive matrix factorization (PMF), including gasoline-related emissions (gasoline exhaust and evaporation), coal combustion, diesel exhaust, acetylene-related emissions, and consumer and household products. Coal combustion (probably domestic coal combustion) was found to make the greatest contribution (29.6-33.4 %) to atmospheric NMHCs during haze days.

Impacts of Four SO2 Oxidation Pathways on Wintertime Sulfate Concentrations

NASA Astrophysics Data System (ADS)

Sarwar, G.; Fahey, K.; Zhang, Y.; Kang, D.; Mathur, R.; Xing, J.; Wei, C.; Cheng, Y.

2017-12-01

Air quality models tend to under-estimate winter-time sulfate concentrations compared to observed data. Such under-estimations are particularly acute in China where very high concentrations of sulfate have been measured. Sulfate is produced by oxidation of sulfur dioxide (SO2) in gas-phase by hydroxyl radical and in aqueous-phase by hydrogen peroxide, ozone, etc. and most air quality models employ such typical reactions. Several additional SO2 oxidation pathways have recently been proposed. Heterogeneous reaction on dust has been suggested to be an important sink for SO2. Oxidation of SO2 on fine particles in presence of nitrogen dioxide (NO2) and ammonia (NH3) at high relative humidity has been implicated for sulfate formation in Chinese haze and London fog. Reactive nitrogen chemistry in aerosol water has also been suggested to produce winter-time sulfate in China. Specifically, high aerosol water can trap SO2 which can be subsequently oxidized by NO2 to form sulfate. Aqueous-phase (in-cloud) oxidation of SO2 by NO2 can also produce sulfate. Here, we use the hemispheric Community Multiscale Air Quality (CMAQ) modeling system to examine the potential impacts of these SO2 oxidation pathways on sulfate formation. We use anthropogenic emissions from the Emissions Database for Global Atmospheric Research and biogenic emissions from Global Emissions InitiAtive. We performed simulations without and with these SO2 oxidation pathways for October-December of 2014 using meteorological fields obtained from the Weather Research and Forecasting model. The standard CMAQ model contains one gas-phase chemical reaction and five aqueous-phase chemical reactions for SO2 oxidation. We implement four additional SO2 oxidation pathways into the CMAQ model. Our preliminary results suggest that the dust chemistry enhances mean sulfate over parts of China and Middle-East, the in-cloud SO2 oxidation by NO2 enhances sulfate over parts of western Europe, oxidation of SO2 by NO2 and NH3 on fine particles enhances sulfate only over parts of China, and SO2 oxidation by NO2 in aerosol water enhances sulfate only over parts of China by >5%. We will present a detailed analysis of the results and a comparison of model predictions with available observed data.

Hydroxyl radical observations during the wintertime in Beijing and comparison with steady state model calculations.

NASA Astrophysics Data System (ADS)

Slater, E.; Whalley, L.; Woodward-Massey, R.; Ye, C.; Crilley, L.; Kramer, L. J.; Vu, T.; Bloss, W.; Squires, F. A.; Dunmore, R.; Lee, J. D.; Heard, D. E.

2017-12-01

In Beijing poor urban air quality has a demonstrable effect on human health. During the wintertime, anthropogenic emissions from fossil fuel combustion can lead to high aerosol loadings and haze events. A high oxidation capacity on hazy days has previously been inferred from the significant contribution secondary organic aerosol (SOA) make to total PM2.5 (Huang et al., 2014). The hydroxyl radical (OH) mediates virtually all of the oxidative chemistry in the atmosphere, being responsible for the transformation of primary emissions into secondary pollutants such as NO2, O3 and SOA. Understanding the sources and sinks of OH in the atmosphere is essential in improving predictions of the lifetimes and chemical processing of pollutants and their transport within urban areas. We will present OH and HO2 measurements made in central Beijing during the recent `An Integrated Study of AIR Pollution PROcesses in Beijing (AIRPRO)' project which took place in November and December 2016. OH measurements were made using the FAGE (Fluorescence Assay by Gas Expansion) technique, with the use of an inlet pre injector (IPI) which provides an alternative method to determine the background by injecting a scavenger (propane) to remove ambient OH. The OH measurements were made over a range of meteorological conditions including a number of haze days, with the average maximum OH concentration measured for the campaign being 2.5 x 106 cm-3 and for haze days the OH concentration reached levels of 3.5 x 106 cm-3 which is comparable to OH levels in non-haze days. We will compare the OH observations to steady state calculations constrained to the total OH reactivity and key OH precursors that were measured alongside OH. Through this comparison we will identify the major OH sources which sustain the wintertime oxidation capacity. The current understanding is that gas-phase oxidation via the OH radical becomes less important in haze events due to lower light and ozone levels, making photochemistry less important (Wang et al.,(2016). However, we will present evidence by comparing the dependence of the OH radical concentrations with PM2.5 levels that the OH concentration persists throughout haze events, and that there may be a missing source of HOx under haze conditions. This finding implies an uncertainty in oxidation capacity during haze events.

Inventory of File nam.t00z.smartpr12.tm00.grib2

Science.gov Websites

Temperature [K] 002 surface DPT 12 hour fcst Dew Point Temperature [K] 003 surface SPFH 12 hour fcst Specific 11 hour fcst Temperature [K] 032 surface TMP 10 hour fcst Temperature [K] 033 surface DPT 11 hour fcst Dew Point Temperature [K] 034 surface DPT 10 hour fcst Dew Point Temperature [K] 035 surface TMAX

Inventory of File nam.t00z.smartak12.tm00.grib2

Science.gov Websites

Temperature [K] 002 surface DPT 12 hour fcst Dew Point Temperature [K] 003 surface SPFH 12 hour fcst Specific 11 hour fcst Temperature [K] 032 surface TMP 10 hour fcst Temperature [K] 033 surface DPT 11 hour fcst Dew Point Temperature [K] 034 surface DPT 10 hour fcst Dew Point Temperature [K] 035 surface TMAX

Inventory of File nam.t00z.smarthi12.tm00.grib2

Science.gov Websites

Temperature [K] 002 surface DPT 12 hour fcst Dew Point Temperature [K] 003 surface SPFH 12 hour fcst Specific 11 hour fcst Temperature [K] 032 surface TMP 10 hour fcst Temperature [K] 033 surface DPT 11 hour fcst Dew Point Temperature [K] 034 surface DPT 10 hour fcst Dew Point Temperature [K] 035 surface TMAX

Inventory of File nam.t00z.smartconus03.tm00.grib2

Science.gov Websites

Temperature [K] 002 surface DPT 3 hour fcst Dew Point Temperature [K] 003 surface SPFH 3 hour fcst Specific Temperature [K] 026 surface TMP 1 hour fcst Temperature [K] 027 surface DPT 2 hour fcst Dew Point Temperature [K] 028 surface DPT 1 hour fcst Dew Point Temperature [K] 029 surface TMAX 0-3 hour acc Maximum

Inventory of File gfs.t06z.smartguam18.tm00.grib2

Science.gov Websites

Temperature [K] 002 surface DPT 18 hour fcst Dew Point Temperature [K] 003 surface SPFH 18 hour fcst Specific TMP 17 hour fcst Temperature [K] 022 surface TMP 16 hour fcst Temperature [K] 023 surface DPT 17 hour fcst Dew Point Temperature [K] 024 surface DPT 16 hour fcst Dew Point Temperature [K] 025 surface TMAX

Inventory of File gfs.t06z.smartguam03.tm00.grib2

Science.gov Websites

Temperature [K] 002 surface DPT 3 hour fcst Dew Point Temperature [K] 003 surface SPFH 3 hour fcst Specific surface 4LFTX 3 hour fcst Best (4 layer) Lifted Index [K] 019 surface TMP 2 hour fcst Temperature [K] 020 surface TMP 1 hour fcst Temperature [K] 021 surface DPT 2 hour fcst Dew Point Temperature [K] 022 surface

Improving Geothermal Heat Pump Air Conditioning Efficiency with Wintertime Cooling using Seasonal Thermal Energy Storage (STES). Application Manual

DTIC Science & Technology

2016-11-01

Defense. Reference herein to any specific commercial product , process, or service by trade name, trademark, manufacturer, or otherwise, does not...1 1.3 Cooling-Dominated Buildings and MCAS Beaufort Case Study 4 1.4 Potential Approach for Mitigating Heat Buildup -- Hybrid Geothermal Heat...the ground through another well. This type of system can be very effective, but it requires access to a productive aquifer with associated

Wintertime Overnight NOx Removal in a Southeastern United States Coal-Fired Power Plant Plume: A Model for Understanding Winter NOx Processing and Its Implications

NASA Technical Reports Server (NTRS)

Fibiger, Dorothy L.; McDuffie, Erin E.; Dube, William P.; Aikin, Kenneth C.; Lopez-Hilifiker, Felipe D.; Lee, Ben H.; Green, Jaime R.; Fiddler, Marc N.; Holloway, John S.; Ebben, Carlena;

Identification of Major Sources of Atmospheric NH3 in an Urban Environment in Northern China During Wintertime.

PubMed

Teng, Xiaolin; Hu, Qingjing; Zhang, Leiming; Qi, Jiajia; Shi, Jinhui; Xie, Huan; Gao, Huiwang; Yao, Xiaohong

2017-06-20

To assess the relative contributions of traffic emission and other potential sources to high levels of atmospheric ammonia (NH 3 ) in urban areas in the wintertime, atmospheric NH 3 and related pollutants were measured at an urban site, ∼300 m from a major traffic road, in northern China in November and December 2015. Hourly average NH 3 varied from 0.3 to 10.8 ppb with an average of 2.4 ppb during the campaign. Contrary to the common perspective in literature, traffic emission was demonstrated to be a negligible contributor to atmospheric NH 3 . Atmospheric NH 3 correlated well with ambient water vapor during many time periods lasting from tens of hours to several days, implying NH 3 released from water evaporation is an important source. Emissions from local green space inside the urban areas were identified to significantly contribute to the observed atmospheric NH 3 during ∼60% of the sampling times. Evaporation of predeposited NH x through wet precipitation combined with emissions from local green space likely caused the spikes of atmospheric NH 3 mostly occurring 1-4 h after morning rush hours or after and during slight shower events. There are still ∼30% of the data samples with appreciable NH 3 level for which major contributors are yet to be identified.

Wintertime Overnight NOx Removal in a Southeastern United States Coal-fired Power Plant Plume: A Model for Understanding Winter NOx Processing and its Implications

NASA Astrophysics Data System (ADS)

Fibiger, Dorothy L.; McDuffie, Erin E.; Dubé, William P.; Aikin, Kenneth C.; Lopez-Hilfiker, Felipe D.; Lee, Ben H.; Green, Jaime R.; Fiddler, Marc N.; Holloway, John S.; Ebben, Carlena; Sparks, Tamara L.; Wooldridge, Paul; Weinheimer, Andrew J.; Montzka, Denise D.; Apel, Eric C.; Hornbrook, Rebecca S.; Hills, Alan J.; Blake, Nicola J.; DiGangi, Josh P.; Wolfe, Glenn M.; Bililign, Solomon; Cohen, Ronald C.; Thornton, Joel A.; Brown, Steven S.

2018-01-01

Nitric oxide (NO) is emitted in large quantities from coal-burning power plants. During the day, the plumes from these sources are efficiently mixed into the boundary layer, while at night, they may remain concentrated due to limited vertical mixing during which they undergo horizontal fanning. At night, the degree to which NO is converted to HNO3 and therefore unable to participate in next-day ozone (O3) formation depends on the mixing rate of the plume, the composition of power plant emissions, and the composition of the background atmosphere. In this study, we use observed plume intercepts from the Wintertime INvestigation of Transport, Emissions and Reactivity campaign to test sensitivity of overnight NOx removal to the N2O5 loss rate constant, plume mixing rate, background O3, and background levels of volatile organic compounds using a 2-D box model of power plant plume transport and chemistry. The factor that exerted the greatest control over NOx removal was the loss rate constant of N2O5. At the lowest observed N2O5 loss rate constant, no other combination of conditions converts more than 10% of the initial NOx to HNO3. The other factors did not influence NOx removal to the same degree.

Remote sensing in Iowa agriculture: Identification and classification of Iowa's crops, soils and forestry resources using ERTS-1 and complimentary underflight imagery

NASA Technical Reports Server (NTRS)

Mahlstede, J. P. (Principal Investigator); Carlson, R. E.; Fenton, T. E.; Thomson, G. W.

1974-01-01

The author has identified the following significant results. Springtime ERTS-1 imagery covering pre-selected test sites in Iowa showed considerable detail with respect to broad soil and land use patterns. Additional imagery has been incorporated into a state mosaic. The mosaic was used as a base for soil association lines transferred from an existing map. The regions of greatest contrast are between the Clarion-Nicollet-Webster soil association area and adjacent areas. Landscape characteristics in this area result in land use patterns with a high percentage of pasture, hay, and timber. The soil association areas of the state that have patterns interpreted to be associated with intensive row crop production are: Moody, Galva-Primghar-Sac, Clarion-Nicollet-Webter, Tama-Muscatine, Dinsdale-Tama, Cresco-Lourdes, Clyde, Kenyon-Floyd-Clyde, and the Luton-Onawa-Salix area on the Missouri River floodplain. Forestland estimates have been attained for an area in central Iowa using wintertime ERTS-1 imagery. Visual analysis of multispectral, temporal imagery indicates that temporal analysis for cropland identification and acreage analyses procedures may be a very useful tool. Combinations of wintertime, springtime, and summertime ERTS-1 imagery separate most vegetation types. Timing can be critical depending upon crop development and harvesting times because of the dynamic nature of agricultural production.

Southern Ocean acidification: A tipping point at 450-ppm atmospheric CO2

PubMed Central

McNeil, Ben I.; Matear, Richard J.

2008-01-01

Southern Ocean acidification via anthropogenic CO2 uptake is expected to be detrimental to multiple calcifying plankton species by lowering the concentration of carbonate ion (CO32−) to levels where calcium carbonate (both aragonite and calcite) shells begin to dissolve. Natural seasonal variations in carbonate ion concentrations could either hasten or dampen the future onset of this undersaturation of calcium carbonate. We present a large-scale Southern Ocean observational analysis that examines the seasonal magnitude and variability of CO32− and pH. Our analysis shows an intense wintertime minimum in CO32− south of the Antarctic Polar Front and when combined with anthropogenic CO2 uptake is likely to induce aragonite undersaturation when atmospheric CO2 levels reach ≈450 ppm. Under the IPCC IS92a scenario, Southern Ocean wintertime aragonite undersaturation is projected to occur by the year 2030 and no later than 2038. Some prominent calcifying plankton, in particular the Pteropod species Limacina helicina, have important veliger larval development during winter and will have to experience detrimental carbonate conditions much earlier than previously thought, with possible deleterious flow-on impacts for the wider Southern Ocean marine ecosystem. Our results highlight the critical importance of understanding seasonal carbon dynamics within all calcifying marine ecosystems such as continental shelves and coral reefs, because natural variability may potentially hasten the onset of future ocean acidification. PMID:19022908

Southern Ocean acidification: a tipping point at 450-ppm atmospheric CO2.

PubMed

McNeil, Ben I; Matear, Richard J

2008-12-02

Southern Ocean acidification via anthropogenic CO(2) uptake is expected to be detrimental to multiple calcifying plankton species by lowering the concentration of carbonate ion (CO(3)(2-)) to levels where calcium carbonate (both aragonite and calcite) shells begin to dissolve. Natural seasonal variations in carbonate ion concentrations could either hasten or dampen the future onset of this undersaturation of calcium carbonate. We present a large-scale Southern Ocean observational analysis that examines the seasonal magnitude and variability of CO(3)(2-) and pH. Our analysis shows an intense wintertime minimum in CO(3)(2-) south of the Antarctic Polar Front and when combined with anthropogenic CO(2) uptake is likely to induce aragonite undersaturation when atmospheric CO(2) levels reach approximately 450 ppm. Under the IPCC IS92a scenario, Southern Ocean wintertime aragonite undersaturation is projected to occur by the year 2030 and no later than 2038. Some prominent calcifying plankton, in particular the Pteropod species Limacina helicina, have important veliger larval development during winter and will have to experience detrimental carbonate conditions much earlier than previously thought, with possible deleterious flow-on impacts for the wider Southern Ocean marine ecosystem. Our results highlight the critical importance of understanding seasonal carbon dynamics within all calcifying marine ecosystems such as continental shelves and coral reefs, because natural variability may potentially hasten the onset of future ocean acidification.

Regional and hemispheric influences on temporal variability in baseline carbon monoxide and ozone over the Northeast US

NASA Astrophysics Data System (ADS)

Zhou, Y.; Mao, H.; Demerjian, K.; Hogrefe, C.; Liu, J.

2017-09-01

Interannual variability in baseline carbon monoxide (CO) and ozone (O3), defined as mixing ratios under minimal influence of recent and local emissions, was studied for seven rural sites in the Northeast US over 2001-2010. Annual baseline CO exhibited statistically significant decreasing trends (-4.3 to -2.3 ppbv yr-1), while baseline O3 did not display trends at any site. In examining the data by season, wintertime and springtime baseline CO at the two highest sites (1.5 km and 2 km asl) did not experience significant trends. Decadal increasing trends (∼2.55 ppbv yr-1) were found in springtime and wintertime baseline O3 in southern New Hampshire, which was associated with anthropogenic NOx emission reductions from the urban corridor. Biomass burning emissions impacted summertime baseline CO with ∼38% variability from wildfire emissions in Russia and ∼22% from Canada at five sites and impacted baseline O3 at the two high elevation sites only with ∼27% variability from wildfires in both Russia and Canada. The Arctic Oscillation was negatively correlated with summertime baseline O3, while the North Atlantic Oscillation was positively correlated with springtime baseline O3. This study suggested that anthropogenic and biomass burning emissions, and meteorological conditions were important factors working together to determine baseline O3 and CO in the Northeast U.S. during the 2000s.

A note on sea level variability at Clipperton Island from GEOSAT and in-situ observations

NASA Astrophysics Data System (ADS)

Maul, George A.; Hansen, Donald V.; Bravo, Nicolas J.

During the 1986-1989 Exact Repeat Mission (ERM) of GEOSAT, in-situ observations of sea level at Clipperton Island (10°N/109°W) and satellite-tracked free-drifting drogued buoys in the eastern tropical Pacific Ocean are concurrently available. A map of the standard deviations of GEOSAT sea surface heights (2.9 years) shows a variance maximum along ˜12°N from Central America, past Clipperton to ˜160°W. Sea floor pressure gauge observations from a shallow (10m depth) site on Clipperton Island and an ERM crossover point in deep water nearby show a correlation of r = 0.76 with a residual of ±6.7 cm RMS. Approximately 17% of the difference (GEOSAT minus sea level) is characterized by a 4 cm amplitude 0° phase annual harmonic, which is probably caused by unaccounted-for tropospheric water vapor affecting the altimeter and/or ERM orbit error removal. Wintertime anticyclonic mesoscale eddies advecting past Clipperton Island each year have GEOSAT sea surface height and in-situ sea level signals of more than 30 cm, some of which are documented by the satellite-tracked drifters. Meridional profiles of the annual harmonic of zonal geostrophic current from GEOSAT and from the drifters both show synchronous maxima in the North Equatorial Countercurrent and the North Equatorial Current. Other Clipperton sea level maxima seen during late spring of each year may involve anticyclonic vortices formed along Central America the previous winter.

Differential response of surface temperature and atmospheric temperature to the biogeophysical effects of deforestation

NASA Astrophysics Data System (ADS)

Winckler, J.; Reick, C. H.; Lejeune, Q.; Pongratz, J.

2017-12-01

Deforestation influences temperature locally by changing the water, energy and momentum balance. While most observation-based studies and some modeling studies focused on the effects on surface temperature, other studies focused on the effects on near-surface air temperature. However, these two variables may respond differently to deforestation because changes in albedo and surface roughness may alter the land-atmosphere coupling and thus the vertical temperature distribution. Thus it is unclear whether it is possible to compare studies that assess the impacts of deforestation on these two different variables. Here, we analyze the biogeophysical effects of global-scale deforestation in the climate model MPI-ESM separately for surface temperature, 2m-air temperature and temperature the lowest atmospheric model layer. We investigate why the response of these variables differs by isolating the effects of only changing surface albedo and only changing surface roughness and by separating effects that are induced at the location of deforestation (local effects) from effects that are induced by advection and changes in circulation (nonlocal effects). Concerning surface temperature, we find that the local effects of deforestation lead to a global mean warming which is overcompensated by the nonlocal effects (up to 0.1K local warming versus -0.3K nonlocal cooling). The surface warming in the local effects is largely driven by the change in surface roughness while the cooling in the nonlocal effects is largely driven by the change in surface albedo. The nonlocal effects are largely consistent across surface temperature, 2m-air temperature, and the temperature of the lowest atmospheric layer. However, the local effects strongly differ across the three considered variables. The local effects are strong for surface temperature, but substantially weaker in the 2m-air temperature and largely absent in the lowest atmospheric layer. We conclude that studies focusing on the deforestation effects on surface temperature should not be compared to studies focusing on the effects on air temperature. While the local effects on surface temperature are useful for model evaluation, they might be less relevant for local adaptation and mitigation than previously thought because they might largely be absent in the atmosphere.

The influence of canopy shading of snow on effective albedo in forested environments

NASA Astrophysics Data System (ADS)

Webster, C.; Jonas, T.

2017-12-01

The overlap of highly reflective snow and absorbent forested areas creates strong heterogeneity in the effective surface albedo compared to forest-free areas. Current errors in calculations of effective forest snow albedo arise due to uncertainties in how models should treat masking of snow by vegetation but improvement of local and large scale models is currently limited by a lack of measurements that demonstrate both spatial and temporal variability over forests. We present above-canopy measurements of winter-time effective forest snow albedo using up- and down-looking radiometers mounted on an octocopter UAV for a total of fifteen flights on eight different days. Ground-view fractions across the flight path were between 0.12 and 0.81. Correlations between effective albedo and both ground-view fraction and canopy height were statistically significant during 14 out of 15 flights, but varied between flights due to solar angle and snow cover. Measured effective albedo across the flight path differed by up to 0.33 during snow-on canopy conditions. A comparison between maximum interception and no interception showed effective albedo varied by up 0.17, which was the same variation between effective albedo during high (46°) and low (23°) solar elevation angles. Temporal and spatial variations in effective albedo caused by canopy shading of the snow surface are therefore as important as temporal variations caused by interception of snow by the canopy. Calculation of effective albedo over forested areas therefore requires careful consideration of canopy height, canopy coverage, solar angle and interception load. The results of this study should be used to inform snow albedo and canopy structure parametrisations in local and larger scale land surface models.

Nitrous acid (HONO) measurements during winter haze events in Beijing

NASA Astrophysics Data System (ADS)

Bloss, W.; Kramer, L. J.; Crilley, L.; Lee, J. D.; Squires, F. A.; Tong, S.

2017-12-01

Daytime HONO levels can reach several parts per billion in megacities during winter haze events and hence act as the dominant (primary) precursor to OH radicals in the urban boundary layer, and affect NOx abundance. Understanding the sources of HONO is therefore important to quantify atmospheric oxidative capacity and secondary pollutant formation during such haze events. Despite decades of research, there are still large uncertainties in HONO formation mechanisms, and as a result models often substantially underestimate peak HONO levels. In this study, measurements of HONO were performed at the Institute of Atmospheric Physics (IAP) site located in central Beijing during Nov/Dec 2016, across both haze and non-haze events. Using a commercial long-path absorption photometer (LOPAP), vertical profiles of HONO concentrations up to a height of 260 m on the IAP Meteorological Tower were performed, as well as continuous near-surface measurements. Preliminary results showed that HONO levels near the ground were very high during the winter haze events with concentrations over 10 ppbV observed. Typically, during the vertical profiles a negative gradient was observed, indicating a large HONO source close to the surface. However, during some of the profiles elevated HONO concentrations were also observed at higher altitudes pointing to a strong source within the boundary layer. Co-located NOx and SO2 measurements are used to elucidate potential HONO sources from direct emissions, homogeneous gas phase reactions and heterogeneous conversion of NO2 on surfaces. Results from ground level HONO/NOx ratios show a midday peak during clean periods indicating a photo-enhanced process, which was not apparent during hazy days. The potential impact of these findings on the OH radical budget in wintertime Beijing will be discussed.

Influence of oxygen partial pressure on surface tension and its temperature coefficient of molten iron

NASA Astrophysics Data System (ADS)

Ozawa, S.; Suzuki, S.; Hibiya, T.; Fukuyama, H.

2011-01-01

Influences of oxygen partial pressure, PO2, of ambient atmosphere and temperature on surface tension and its temperature coefficient for molten iron were experimentally investigated by an oscillating droplet method using an electromagnetic levitation furnace. We successfully measured the surface tension of molten iron over a very wide temperature range of 780 K including undercooling condition in a well controlled PO2 atmosphere. When PO2 is fixed at 10-2 Pa at the inlet of the chamber, a "boomerang shape" temperature dependence of surface tension was experimentally observed; surface tension increased and then decreased with increasing temperature. The pure surface tension of molten iron was deduced from the negative temperature coefficient in the boomerang shape temperature dependence. When the surface tension was measured under the H2-containing gas atmosphere, surface tension did not show a linear relationship against temperature. The temperature dependence of the surface tension shows anomalous kink at around 1850 K due to competition between the temperature dependence of PO2 and that of the equilibrium constant of oxygen adsorption.

Mesosphere-Stratosphere Coupling: Implications for Climate Variability and Trends

NASA Technical Reports Server (NTRS)

Baldwin, Mark P.

2004-01-01

A key aspect of this project is the establishment of a causal link from circulation anomalies in the lower mesosphere and stratopause region downward through the stratosphere to the troposphere. The observational link for stratospheric sudden warmings and surface climate is fairly clear. However, our understanding of the dynamics is incomplete. We have been making significant progress in the area of dynamical mechanisms by which circulation anomalies in the stratosphere affect the troposphere. We are trying to understand the details and sequence of events that occur when a middle atmosphere (wind) anomaly propagates downward to near the tropopause. The wind anomaly could be caused by a warming or solar variations in the low-latitude stratopause region, or could have other causes. The observations show a picture that is consistent with a circulation anomaly that descends to the tropopause region, and can be detected as low as the mid-troposphere. Processes near the stratopause in the tropics appear to be important precursors to the wintertime development of the northern polar vortex. This may affect significantly our understanding of the process by which low-latitude wind anomalies in the low mesosphere and upper stratosphere evolve through the winter and affect the polar vortex.

Influence of Mesoscale Eddies on New Production in the Sargasso Sea

NASA Technical Reports Server (NTRS)

McGillicuddy , Dennis J., Jr.; Robinson, A. R.; Siegel, D. A.; Jannasch, H. W.; Johnson, R.; Dickey, T. D.; McNeil, J.; Michaels, A. F.; Knap, A. H.

1998-01-01

It is problematic that geochemical estimates of new production - that fraction of total primary production in surface waters fueled by externally supplied nutrients - in oligotrophic waters of the open ocean surpass that which can be sustained by the traditionally accepted mechanisms of nutrient supply. In the case of the Sargasso Sea, for example, these mechanisms account for less than half of the annual nutrient requirement indicated by new production estimates based on three independent transient-tracer techniques. Specifically, approximately one-quarter to one-third of the annual nutrient requirement can be supplied by entrainment into the mixed layer during wintertime convection, with minor contributions from mixing in the thermocline and wind-driven transport (the potentially important role of nitrogen fixation - for which estimates vary by an order of magnitude in this region - is excluded from this budget). Here we present four lines of evidence - eddy-resolving model simulations, high-resolution observations from moored instrumentation, shipboard surveys, and satellite data - which suggest that the vertical flux of nutrients induced by the dynamics of mesoscale eddies is sufficient to balance the nutrient budget in the Sargasso Sea. Additional information is contained in the original extended abstract.

Evaluation of the Main Ceos Pseudo Calibration Sites Using Modis Brdf/albedo Products

NASA Astrophysics Data System (ADS)

Kharbouche, Said; Muller, Jan-Peter

2016-06-01

This work describes our findings about an evaluation of the stability and the consistency of twenty primary PICSs (Pseudo-Invariant Calibration Sites). We present an analysis of 13 years of 8-daily MODIS products of BRDF parameters and white-sky-albedos (WSA) over the shortwave band. This time series of WSA and BRDFs shows the variation of the "stability" varies significantly from site to site. Using a 10x10 km window size over all the sites, the change in of WSA stability is around 4% but the isotropicity, which is an important element in inter-satellite calibration, can vary from 75% to 98%. Moreover, some PICS, especially, Libya-4 which is one of the PICS which is most employed, has significant and relatively fast changes in wintertime. PICS observations of BRDF/albedo shows that the Libya-4 PICS has the best performance but it is not too far from some sites such as Libya-1 and Mali. This study also reveals that Niger-3 PICS has the longest continuous period of high stability per year, and Sudan has the most isotropic surface. These observations have important implications for the use of these sites.

No snow for Christmas: the impact of the 2015 extreme winter on CO2 fluxes in European mountain grasslands

NASA Astrophysics Data System (ADS)

Cremonese, Edoardo; Galvagno, Marta; Hammerle, Albin; Filippa, Gianluca; Wohlfahrt, Georg

2016-04-01

The increasing frequency in extreme climate events is very likely to impact the Alps since this region is characterized by very sensitive ecosystems. Typical alpine ecosystems such as mountain grasslands, show a strong seasonality in carbon uptake and release mostly driven by the onset and the end of the snow season. Extreme climate events, such as long warm and/or dry periods, could change typical snow cover temporal pattern, thereby altering the duration of the period of CO2 uptake and release. In recent years many studies have analyzed the impact of delayed or anticipated snowmelt on alpine plant phenology, growth and carbon cycling. However, little is known on the effects of a delayed onset of the snow season. During 2015 the whole planet witnessed several record-breaking warm spells which exceptionally warmed the Alps where the temperature anomaly reached +4°C during both the autumn and winter periods. In particular, the onset of the 2015 winter in the Alps was marked by one of the most prolonged lack of snow in years. In this study, we investigate and discuss the impact of the altered temperature and precipitation pattern during the autumn/winter 2015 on the net ecosystem CO2 exchange of mountain grasslands at high and low altitudes measured by means of the eddy covariance method. In particular we test the following hypotheses: (i) The presence of a snowpack impedes plant photosynthesis, while without a snowpack, plant net CO2 uptake may be possible even during wintertime provided temperatures are warm enough. (ii) Below a snowpack, soil temperatures are around zero degrees Celsius, allowing for microbial activity resulting in intermediate soil respiration; without a snow cover soil temperatures may be either lower or higher than zero degrees Celsius, decreasing or increasing soil respiration. The magnitude and direction of the net ecosystem CO2 exchange of mountain grassland ecosystems is governed by the complex interplay of the factors addressed in hypothesis (i) and (ii).

Recent Climate Changes in Northwestern Qaidam Basin Inferred from Geothermal Gradients

NASA Astrophysics Data System (ADS)

Liu, J.; Zhang, T.

2014-12-01

Temperature perturbations under the ground surface are direct thermal response to ground surface temperature changes. Thus ground surface temperature history can be reconstructed from borehole temperature measurements using borehole paleothermometry inversion method. In this study, we use seven borehole temperature profiles to reconstruct the ground surface temperature variation of the past 500 years of the Qaidam basin, northwestern China. Borehole transient temperature measurement from seven sites in northwestern Qaidam basin were separated from geothermal gradients and analyzed by functional space inversion method to determine past ground surface temperature variations in this region. All temperature profiles show the effects of recent climatic disturbances. Inversion shows an overall increase in ground surface temperature by an averaged 1.2℃ (-0.11~2.21℃) during the last 500 years. Clear signs of a cold period between 1500 and 1900 A.D., corresponding to the Little Ice Age, have been found. Its coldest period was between 1780~1790 A.D. with the ground surface temperature of 5.4℃. During the 19th and the 20th century, reconstructed ground surface temperature shows a rising trend, and in the late 20th century, the temperature started to decrease. However, the highest temperature in 1990s broke the record of the past 500 years. This reconstructed past ground surface temperature variation is verified by the simulated annual surface air temperature computed by EdGCM and the cooling trend is also confirmed by other reconstruction of winter half year minimum temperatures using tree rings on the northeastern Tibetan Plateau.

Inventory of File nam.t00z.smartconus06.tm00.grib2

Science.gov Websites

Temperature [K] 002 surface DPT 6 hour fcst Dew Point Temperature [K] 003 surface SPFH 6 hour fcst Specific Index [K] 027 surface HINDEX 6 hour fcst Haines Index [Numeric] 028 surface TMP 5 hour fcst Temperature [K] 029 surface TMP 4 hour fcst Temperature [K] 030 surface DPT 5 hour fcst Dew Point Temperature [K

Inventory of File gfs.t06z.smartguam12.tm00.grib2

Science.gov Websites

Temperature [K] 002 surface DPT 12 hour fcst Dew Point Temperature [K] 003 surface SPFH 12 hour fcst Specific Best (4 layer) Lifted Index [K] 020 surface TMP 11 hour fcst Temperature [K] 021 surface TMP 10 hour fcst Temperature [K] 022 surface DPT 11 hour fcst Dew Point Temperature [K] 023 surface DPT 10 hour

Inventory of File nam.t00z.smartak06.tm00.grib2

Science.gov Websites

Temperature [K] 002 surface DPT 6 hour fcst Dew Point Temperature [K] 003 surface SPFH 6 hour fcst Specific Haines Index [Numeric] 029 surface TMP 5 hour fcst Temperature [K] 030 surface TMP 4 hour fcst Temperature [K] 031 surface DPT 5 hour fcst Dew Point Temperature [K] 032 surface DPT 4 hour fcst Dew Point

Inventory of File nam.t00z.smartconus12.tm00.grib2

Science.gov Websites

Temperature [K] 002 surface DPT 12 hour fcst Dew Point Temperature [K] 003 surface SPFH 12 hour fcst Specific hour fcst Haines Index [Numeric] 030 surface TMP 11 hour fcst Temperature [K] 031 surface TMP 10 hour fcst Temperature [K] 032 surface DPT 11 hour fcst Dew Point Temperature [K] 033 surface DPT 10 hour

Simulation of Relationship between ENSO and winter precipitation over Western Himalayas: Application of Regional climate model (RegT-Band)

NASA Astrophysics Data System (ADS)

Tiwari, P. R.; Mohanty, U. C.; Dey, S.; Acharaya, N.; Sinha, P.

2012-12-01

Precipitation over the Western Himalayas region during winter is mainly associated with the passage of midlatitude synoptic systems known as western disturbances (WDs). Recently, many observational and modeling studies reported that the relationship of the Indian southwest monsoon rainfall with El Niño- Southern Oscillation (ENSO) has weakened since around 1980. But, in contrast, only very few observational studies are reported so far to examine the relationship between ENSO and the winter precipitation over the Western Himalayas region from December to February (DJF). But there is a huge gap of modeling this phenomenon. So keeping in view of the absence of modeling studies, an attempt is made to simulate the relationship between wintertime precipitations associated with large scale global forcing of ENSO over the Western Himalayas. In the present study, RegT-Band, a tropical band version of the regional climate model RegCM4 is integrated for a set of 5 El Niño (1986-87, 1991-92, 1997-98, 2002-03, 2009-10) and 4 La Niña (1984-85, 1988-89, 1999-2000, 2007-08) years with the observed sea-surface temperature and lateral boundary condition. The domain extends from 50° S to 50° N and covers the entire tropics at a grid spacing of about 45 km, i.e. it includes lateral boundary forcing only at the southern and northern boundaries. The performance evaluation of the model in capturing the large scale fields followed by ENSO response with wintertime precipitation over the Western Himalayas region has been carried out by using National Center for Environmental Prediction (NCEP)-Department of Energy (DOE) reanalysis 2 (NNRP2) data (2.5° x 2.5°) and Aphrodite precipitation data (0.25° x 0.25°). The model is able to delineate the mean circulation associated with ENSO over the region during DJF reasonably well and shows strong southwesterly to northwesterly wind flow, which is there in verification analysis also. The vertical structure of the low as well as upper level air circulation for the ENSO regimes has been also studied. For this purpose, a longitudional cross-section of the seasonal sectorial mean of the zonal and meridional winds is analyzed form NNRP2 and RegT-Band model simulations. The model simulated zonal wind is in good agreement with verification analysis however core speed of subtropical Westerly Jet Stream in upper level (around 150 hPa) is overestimated by the model. Further, the sectorial cross section of meridional wind indicates that the wind around 200 hPa is stronger during ENSO years, and this feature is emphasized well in the model simulation. So the upper and lower level sartorial components of wind supports the argument of strengthening of circulation associated with ENSO, and hence enhanced precipitation during ENSO-winter precipitation relationship. So our preliminary study indicates that the tropical band version of the regional climate model can be effectively used for the better understanding of these large scale global forcing's. This can improve the predictability of precipitation over this region and so it might help to come out with better socio-economic tools. Key words: Winter precipitation, El-Nino-southern oscillation, RegCM4, ENSO response and RegT-Band.

Cross-scale modeling of surface temperature and tree seedling establishment inmountain landscapes

USGS Publications Warehouse

Dingman, John; Sweet, Lynn C.; McCullough, Ian M.; Davis, Frank W.; Flint, Alan L.; Franklin, Janet; Flint, Lorraine E.

2013-01-01

Abstract: Introduction: Estimating surface temperature from above-ground field measurements is important for understanding the complex landscape patterns of plant seedling survival and establishment, processes which occur at heights of only several centimeters. Currently, future climate models predict temperature at 2 m above ground, leaving ground-surface microclimate not well characterized. Methods: Using a network of field temperature sensors and climate models, a ground-surface temperature method was used to estimate microclimate variability of minimum and maximum temperature. Temperature lapse rates were derived from field temperature sensors and distributed across the landscape capturing differences in solar radiation and cold air drainages modeled at a 30-m spatial resolution. Results: The surface temperature estimation method used for this analysis successfully estimated minimum surface temperatures on north-facing, south-facing, valley, and ridgeline topographic settings, and when compared to measured temperatures yielded an R2 of 0.88, 0.80, 0.88, and 0.80, respectively. Maximum surface temperatures generally had slightly more spatial variability than minimum surface temperatures, resulting in R2 values of 0.86, 0.77, 0.72, and 0.79 for north-facing, south-facing, valley, and ridgeline topographic settings. Quasi-Poisson regressions predicting recruitment of Quercus kelloggii (black oak) seedlings from temperature variables were significantly improved using these estimates of surface temperature compared to air temperature modeled at 2 m. Conclusion: Predicting minimum and maximum ground-surface temperatures using a downscaled climate model coupled with temperature lapse rates estimated from field measurements provides a method for modeling temperature effects on plant recruitment. Such methods could be applied to improve projections of species’ range shifts under climate change. Areas of complex topography can provide intricate microclimates that may allow species to redistribute locally as climate changes.

Temperature distribution and heat radiation of patterned surfaces at short wavelengths.

PubMed

Emig, Thorsten

2017-05-01

We analyze the equilibrium spatial distribution of surface temperatures of patterned surfaces. The surface is exposed to a constant external heat flux and has a fixed internal temperature that is coupled to the outside heat fluxes by finite heat conductivity across the surface. It is assumed that the temperatures are sufficiently high so that the thermal wavelength (a few microns at room temperature) is short compared to all geometric length scales of the surface patterns. Hence the radiosity method can be employed. A recursive multiple scattering method is developed that enables rapid convergence to equilibrium temperatures. While the temperature distributions show distinct dependence on the detailed surface shapes (cuboids and cylinder are studied), we demonstrate robust universal relations between the mean and the standard deviation of the temperature distributions and quantities that characterize overall geometric features of the surface shape.

Temperature distribution and heat radiation of patterned surfaces at short wavelengths

NASA Astrophysics Data System (ADS)

Emig, Thorsten

2017-05-01

We analyze the equilibrium spatial distribution of surface temperatures of patterned surfaces. The surface is exposed to a constant external heat flux and has a fixed internal temperature that is coupled to the outside heat fluxes by finite heat conductivity across the surface. It is assumed that the temperatures are sufficiently high so that the thermal wavelength (a few microns at room temperature) is short compared to all geometric length scales of the surface patterns. Hence the radiosity method can be employed. A recursive multiple scattering method is developed that enables rapid convergence to equilibrium temperatures. While the temperature distributions show distinct dependence on the detailed surface shapes (cuboids and cylinder are studied), we demonstrate robust universal relations between the mean and the standard deviation of the temperature distributions and quantities that characterize overall geometric features of the surface shape.

Near-surface temperature inversion during summer at Summit, Greenland, and its relation to MODIS-derived surface temperatures

NASA Astrophysics Data System (ADS)

Adolph, Alden C.; Albert, Mary R.; Hall, Dorothy K.

2018-03-01

As rapid warming of the Arctic occurs, it is imperative that climate indicators such as temperature be monitored over large areas to understand and predict the effects of climate changes. Temperatures are traditionally tracked using in situ 2 m air temperatures and can also be assessed using remote sensing techniques. Remote sensing is especially valuable over the Greenland Ice Sheet, where few ground-based air temperature measurements exist. Because of the presence of surface-based temperature inversions in ice-covered areas, differences between 2 m air temperature and the temperature of the actual snow surface (referred to as skin temperature) can be significant and are particularly relevant when considering validation and application of remote sensing temperature data. We present results from a field campaign extending from 8 June to 18 July 2015, near Summit Station in Greenland, to study surface temperature using the following measurements: skin temperature measured by an infrared (IR) sensor, 2 m air temperature measured by a National Oceanic and Atmospheric Administration (NOAA) meteorological station, and a Moderate Resolution Imaging Spectroradiometer (MODIS) surface temperature product. Our data indicate that 2 m air temperature is often significantly higher than snow skin temperature measured in situ, and this finding may account for apparent biases in previous studies of MODIS products that used 2 m air temperature for validation. This inversion is present during our study period when incoming solar radiation and wind speed are both low. As compared to our in situ IR skin temperature measurements, after additional cloud masking, the MOD/MYD11 Collection 6 surface temperature standard product has an RMSE of 1.0 °C and a mean bias of -0.4 °C, spanning a range of temperatures from -35 to -5 °C (RMSE = 1.6 °C and mean bias = -0.7 °C prior to cloud masking). For our study area and time series, MODIS surface temperature products agree with skin surface temperatures better than previous studies indicated, especially at temperatures below -20 °C, where other studies found a significant cold bias. We show that the apparent cold bias present in other comparisons of 2 m air temperature and MODIS surface temperature may be a result of the near-surface temperature inversion. Further investigation of how in situ IR skin temperatures compare to MODIS surface temperature at lower temperatures (below -35 °C) is warranted to determine whether a cold bias exists for those temperatures.

Inventory of File nam.t00z.smartak03.tm00.grib2

Science.gov Websites

Temperature [K] 002 surface DPT 3 hour fcst Dew Point Temperature [K] 003 surface SPFH 3 hour fcst Specific fcst Haines Index [Numeric] 026 surface TMP 2 hour fcst Temperature [K] 027 surface TMP 1 hour fcst Temperature [K] 028 surface DPT 2 hour fcst Dew Point Temperature [K] 029 surface DPT 1 hour fcst Dew Point

Retrieval of surface temperature by remote sensing. [of earth surface using brightness temperature of air pollutants

NASA Technical Reports Server (NTRS)

Gupta, S. K.; Tiwari, S. N.

1976-01-01

A simple procedure and computer program were developed for retrieving the surface temperature from the measurement of upwelling infrared radiance in a single spectral region in the atmosphere. The program evaluates the total upwelling radiance at any altitude in the region of the CO fundamental band (2070-2220 1/cm) for several values of surface temperature. Actual surface temperature is inferred by interpolation of the measured upwelling radiance between the computed values of radiance for the same altitude. Sensitivity calculations were made to determine the effect of uncertainty in various surface, atmospheric and experimental parameters on the inferred value of surface temperature. It is found that the uncertainties in water vapor concentration and surface emittance are the most important factors affecting the accuracy of the inferred value of surface temperature.

Density, Demography, and Influential Environmental Factors on Overwintering Populations of Sogatella furcifera (Hemiptera: Delphacidae) in Southern Yunnan, China

PubMed Central

Hu, Shao-Ji; Fu, Da-Ying; Han, Zhong-Liang; Ye, Hui

2015-01-01

Sogatella furcifera (Horváth) (Hemiptera: Delphacidae) is the most serious pest on rice in southwestern China. Yunnan province is within this region and is a major overwintering area for S. furcifera in China. This field study was carried out over 4 yr (2010–2013) and focused on S. furcifera distribution, population density, and demography, as well as the relationship between various environmental factors and the distribution and density of overwintering S. furcifera in Yunnan. Our study demonstrated that overwintering populations of S. furcifera mainly occurred in valleys and lowlands below 25.02°N and 1,680 m above sea level (a.s.l.), where ratooning rice was present. The overwintering range of S. furcifera has expanded in Yunnan compared with 20 yr ago, and regional climate change is believed to be the main contributing cause for this expansion. Environmental factor analysis showed that the mean air temperature of the coldest quarter and precipitation of the coldest quarter were two key factors that were strongly linked to the overwintering distribution and density of S. furcifera in Yunnan. Wintertime temperature was the principal influencing factor to determine the distribution and density of S. furcifera, while the effect of precipitation was indirect in that it influenced the insect’s distribution via its host. This study documented the major overwintering areas of S. furcifera in Yunnan, which can be used to predict outbreak potential in the following spring. Hence, key climatic factors, overwintering distribution, and density of S. furcifera should be used when forecasting outbreaks in spring. PMID:25978998

Spatial and temporal distributions of Martian north polar cold spots before, during, and after the global dust storm of 2001

USGS Publications Warehouse

Cornwall, C.; Titus, T.N.

2009-01-01

In the 1970s, Mariner and Viking observed features in the Mars northern polar region that were a few hundred kilometers in diameter with 20 fj,m brightness temperatures as low as 130 K (considerably below C02 ice sublimation temperatures). Over the past decade, studies have shown that these areas (commonly called "cold spots") are usually due to emissivity effects of frost deposits and occasionally to active C02 snowstorms. Three Mars years of Mars Global Surveyor Thermal Emission Spectrometer data were used to observe autumn and wintertime cold spot activity within the polar regions. Many cold spots formed on or near scarps of the perennial cap, probably induced by adiabatic cooling due to orographic lifting. These topographically associated cold spots were often smaller than those that were not associated with topography. We determined that initial grain sizes within the cold spots were on the order of a few millimeters, assuming the snow was uncontaminated by dust or water ice. On average, the half-life of the cold spots was 5 Julian days. The Mars global dust storm in 2001 significantly affected cold spot activity in the north polar region. Though overall perennial cap cold spot activity seemed unaffected, the distribution of cold spots did change by a decrease in the number of topographically associated cold spots and an increase in those not associated with topography. We propose that the global dust storm affected the processes that form cold spots and discuss how the global dust storm may have affected these processes. ?? 2009 by the American Geophysical Union.

Surface Emissivity Effects on Thermodynamic Retrieval of IR Spectral Radiance

NASA Technical Reports Server (NTRS)

Zhou, Daniel K.; Larar, Allen M.; Smith, William L.; Liu, Xu

2006-01-01

The surface emissivity effect on the thermodynamic parameters (e.g., the surface skin temperature, atmospheric temperature, and moisture) retrieved from satellite infrared (IR) spectral radiance is studied. Simulation analysis demonstrates that surface emissivity plays an important role in retrieval of surface skin temperature and terrestrial boundary layer (TBL) moisture. NAST-I ultraspectral data collected during the CLAMS field campaign are used to retrieve thermodynamic properties of the atmosphere and surface. The retrievals are then validated by coincident in-situ measurements, such as sea surface temperature, radiosonde temperature and moisture profiles. Retrieved surface emissivity is also validated by that computed from the observed radiance and calculated emissions based on the retrievals of surface temperature and atmospheric profiles. In addition, retrieved surface skin temperature and emissivity are validated together by radiance comparison between the observation and retrieval-based calculation in the window region where atmospheric contribution is minimized. Both simulation and validation results have lead to the conclusion that variable surface emissivity in the inversion process is needed to obtain accurate retrievals from satellite IR spectral radiance measurements. Retrieval examples are presented to reveal that surface emissivity plays a significant role in retrieving accurate surface skin temperature and TBL thermodynamic parameters.

Rapid aqueous phase SO2 oxidation in winter fog in the Indo-Gangetic Plain

NASA Astrophysics Data System (ADS)

Sachan, Himanshu; Sarkar, Chinmoy; Sinha, Baerbel

2013-04-01

Sulphate and sulphur dioxide play an important role in environmental chemistry and climate. The majority of anthropogenic sulphur is released directly as SO2, and a significant fraction of biogenic and natural sulphur emissions are also either directly released as SO2 or oxidised to SO2 in the atmosphere (e.g. H2S, OCS, DMS). Around 50% of global atmospheric sulphur dioxide is then oxidised to sulphate, while the rest is lost through dry and wet deposition. The pathway by which SO2 is oxidised to sulphate is critical in determining the climate forcing and environmental effects of sulphate. Gas-phase oxidation of SO2 by OH radicals or criegee intermediates produces H2SO4 (g), which plays an important role in controlling new particle formation in the troposphere and also modifies the surface properties of hydrophobic particles such as soot and mineral dust. Heterogeneous oxidation of SO2 is considered to occur primarily in cloud droplets, although oxidation on sea salt aerosols and mineral dust surfaces are considered to be regionally important. Heterogeneous oxidation leads to the formation of fewer and larger particles with shorter atmospheric lifetime. The major oxidation pathways which are considered to contribute to sulphate formation in the aqueous phase are oxidation by H2O2 and oxidation by O3 and the lifetime of SO2 with respect to all known loss processes combined is considered to be 1-2 days. Here we report measurements of SO2 measurements from IISER Mohali - Ambient Air Quality Station (30.67°N, 76.73°E), a station located at a suburban site in the Indo Gangetic Basin (IGB) during wintertime (10th Dec. 2011 to 29th Feb. 2012). We use a strong point source of SO2 with known SO2/CO emission ratio (brick kiln) located 6.5 km east of our measurement site to estimate the loss rate of SO2 in wintertime fog in the IGB. We consider the transport from the source to the receptor site to be Lagrangian and use the measured CO concentration at the receptors site to account for changes in the emission intensity (activity pattern) and the dilution of the plume during transport. We see a linear correlation between the measured SO2/CO ratio and the transport time. Binning the data on the basis of relative humidity and applying first order kinetics to SO2 loss within each humidity bin we find the SO2 loss rate with respect to aqueous phase oxidation at our sites varies between > 2.2 x 10-3 mol/cm3/s at 96 % RH and 3.8 x 10-4 mol/cm3/s at 47 % RH. Simple box model calculations reveal that neither oxidation by H2O2 nor oxidation by O3 can account for such rapid SO2 oxidation in the fog water. Considering the high mineral dust loadings are our station (PM 10 typically > 300 μg/m3) we propose that transition metal catalysis by TMI leached from natural mineral dust and resuspended road dust may be responsible for the rapid oxidation of SO2 in the fog water. However, the observed lifetime with respect to aqueous phase oxidation in wintertime fog is a factor 150-800 times shorter than the lifetime of SO2 with respect to TMI catalyzed oxidation currently implemented in global atmospheric chemistry models. During 2012-2013 winter season we will measure TMI concentrations in the fog water and verify the rates coefficients estimated from the ambient observation by conducting controlled experiments both using collected fog water and different TMI mixtures. If confirmed through laboratory studies our findings have major implications for the SO2 lifetime over the IGP (and possibly other regions with high mineral dust loadings) and will significantly alter the regional direct and indirect aerosol forcing estimates due to anthropogenic SO2 emissions. Acknowledgement: We thank the IISER Mohali Atmospheric Chemistry Facility for data and the Ministry of Human Resource Development (MHRD), India and IISER Mohali for funding the facility. Himanshu acknowledges the DST-INSPIRE Fellowship program. Chinmoy Sarkar thanks the Max Planck-DST India Partner Group on Tropospheric OH reactivity and VOCs for funding the research.

An Examination of Body Temperature for the Rocky Intertidal Mussel species, Mytilus californianus, Using Remotely Sensed Satellite Observations

NASA Astrophysics Data System (ADS)

Price, J.; Liff, H.; Lakshmi, V.

2012-12-01

Temperature is considered to be one of the most important physical factors in determining organismal distribution and physiological performance of species in rocky intertidal ecosystems, especially the growth and survival of mussels. However, little is known about the spatial and temporal patterns of temperature in intertidal ecosystems or how those patterns affect intertidal mussel species because of limitations in data collection. We collected in situ temperature at Strawberry Hill, Oregon USA using mussel loggers embedded among the intertidal mussel species, Mytilus californianus. Remotely sensed surface temperatures were used in conjunction with in situ weather and ocean data to determine if remotely sensed surface temperatures can be used as a predictor for changes in the body temperature of a rocky intertidal mussel species. The data used in this study was collected between January 2003 and December 2010. The mussel logger temperatures were compared to in situ weather data collected from a local weather station, ocean data collected from a NOAA buoy, and remotely sensed surface temperatures collected from NASA's sun-synchronous Moderate Resolution Imaging Spectroradiometer aboard the Earth Observing System Aqua and EOS Terra satellites. Daily surface temperatures were collected from four pixel locations which included two sea surface temperature (SST) locations and two land surface temperature (LST) locations. One of the land pixels was chosen to represent the intertidal surface temperature (IST) because it was located within the intertidal zone. As expected, all surface temperatures collected via satellite were significantly correlated to each other and the associated in situ temperatures. Examination of temperatures from the off-shore NOAA buoy and the weather station provide evidence that remotely sensed temperatures were similar to in situ temperature data and explain more variability in mussel logger temperatures than the in situ temperatures. Our results suggest that temperatures (surface temperature and air temperature) are similar across larger spatial scales even when the type of data collection is different. Mussel logger temperatures were strongly correlated to SSTs and were not significantly different than SSTs. Sea surface temperature collected during the Aqua overpass explained 67.1% of the variation in mean monthly mussel logger temperature. When SST, LST, and IST were taken into consideration, nearly 73% of the variation in mussel logger temperature was explained. While in situ monthly air temperature and water temperature explained only 28-33% of the variation in mussel logger temperature. Our results suggests that remotely sensed surface temperatures are reliable and important measurements that can be used to better understand the effects temperature may have on intertidal mussel species in Strawberry Hill, Oregon. Remotely sensed surface temperature could act as a relative indicator of change and may be used to predict general habitat trends and drivers that could directly affect organism body temperature.

The relationship between surface temperature, tissue temperature, microbubble formation, and steam pops.

PubMed

Thompson, Nathaniel; Lustgarten, Daniel; Mason, Bryan; Mueller, Enkhtuyaa; Calame, James; Bell, Stephen; Spector, Peter

2009-07-01

It has been proposed that microbubble (MB) monitoring can be used to safely titrate radiofrequency (RF) power. However, MB formation has been found to be an insensitive indicator of tissue temperature during RF delivery. We hypothesized that MB formation corresponds to surface-not tissue--temperature, and therefore would be an insensitive predictor of steam pops. An in vitro bovine heart model was used to measure surface and tissue temperatures during RF delivery under conditions designed to cause steam pops. Sensitivity of type II MB (MBII) formation as a predictor of steam pops and for surface temperatures more than 80 degrees C was calculated. Of 105 lesions delivered, 99 steam pops occurred. Twenty-one steam pops were preceded by MBII. MBII were seen in 26 lesions, five of which were not associated with steam pop. Surface temperature at onset of MBII was 87 +/- 9 degrees C versus a tissue temperature of 78 +/- 23 degrees C (P = 0.044). Surface temperature at the time of steam pops was 71 +/- 17 degrees C versus a tissue temperature of 102 +/- 17 degrees C (P < 0.0001). The sensitivity of MBII for steam pops was 21%, and 58% for detecting surface temperature in excess of 80 degrees C. MBII correlated better with surface temperature than with tissue temperature; steam pops, on the other hand, correlated better with tissue temperature. MBII was an insensitive marker of steam pops and surface temperature in excess of 80 degrees C. Therefore, MBII should not be used to titrate RF power.

Active radiometer for self-calibrated furnace temperature measurements

DOEpatents

Woskov, Paul P.; Cohn, Daniel R.; Titus, Charles H.; Wittle, J. Kenneth; Surma, Jeffrey E.

1996-01-01

Radiometer with a probe beam superimposed on its field-of-view for furnace temperature measurements. The radiometer includes a heterodyne millimeter/submillimeter-wave receiver including a millimeter/submillimeter-wave source for probing. The receiver is adapted to receive radiation from a surface whose temperature is to be measured. The radiation includes a surface emission portion and a surface reflection portion which includes the probe beam energy reflected from the surface. The surface emission portion is related to the surface temperature and the surface reflection portion is related to the emissivity of the surface. The simultaneous measurement of surface emissivity serves as a real time calibration of the temperature measurement.

Sediment-Overlying Water Relationships Affecting Wintertime Dissolved Oxygen Conditions in the Big Eau Pleine Reservoir, Wisconsin.

DTIC Science & Technology

1992-07-01

22202-4302. and to the Office of Managel ent and Bidget . P worki Reduction Pfo4ect(07T4-016 Wahington. DC 20S03. -1. AGENCY USE ONLY (Leave blank) 2...higher pool elevation can not be maintained, it is likely that additional aerators must be installed for incremental use to meet periodic heavy oxygen...install additional aerators throughout the reservoir for incremental use as needed to enhance oxygen diffusion processes. The difficulty with this

Life cycles of persistent anomalies. I - Evolution of 500 mb height fields

NASA Technical Reports Server (NTRS)

Dole, Randall M.

1989-01-01

The life cycles of persistent anomalies of the extratropical Northern Hemisphere wintertime circulation are studied, focusing on the typical characteristics of the 500 mb height anomaly and flow patterns accompanying the development and breakdown of large-scale flow anomalies in the eastern North Atlantic and the northern Soviet Union. Following onset, anomaly centers develop and intensify in sequence downstream from the main center, forming a quasi-stationary wavetrain pattern. From development through decay, corresponding positive and negative patterns have similar evolutions.

STS-42 Earth observation of New York City (NYC), New York

NASA Image and Video Library

1992-01-30

STS-42 Earth observation taken aboard Discovery, Orbiter Vehicle (OV) 103, is of New York City (NYC), New York (41.0N, 74.0W). Snow cover highlights the large areas of development and the many reservoirs in this wintertime scene of the metropolitan NYC area. Features such as Central Park in Manhattan, the George Washington Bridge connecting Manhattan with New Jersey, street patterns in most of the boroughs, La Guardia and JFK airports in Queens, and the extensive harbor system are easily identified.

STS-42 Earth observation of New York City (NYC), New York

NASA Technical Reports Server (NTRS)

1992-01-01

STS-42 Earth observation taken aboard Discovery, Orbiter Vehicle (OV) 103, is of New York City (NYC), New York (41.0N, 74.0W). Snow cover highlights the large areas of development and the many reservoirs in this wintertime scene of the metropolitan NYC area. Features such as Central Park in Manhattan, the George Washington Bridge connecting Manhattan with New Jersey, street patterns in most of the boroughs, La Guardia and JFK airports in Queens, and the extensive harbor system are easily identified.

Classroom Demonstrations Of Atmosphere-ocean Dynamics: Baroclinic Instability

NASA Astrophysics Data System (ADS)

Aurnou, Jonathan; Nadiga, B. T.

2008-09-01

Here we will present simple hands-on experimental demonstrations that show how baroclinic instabilities develop in rotating fluid dynamical systems. Such instabilities are found in the Earth's oceans and atmosphere as well as in the atmospheres and oceans of planetary bodies throughout the solar system and beyond. Our inexpensive experimental apparatus consists of a vinyl-record player, a wide shallow pan, and a weighted, dyed block of ice. Most directly, these demonstrations can be used to explain winter-time atmospheric weather patterns observed in Earth's mid-latitudes.

Assimilation of Surface Temperature in Land Surface Models

NASA Technical Reports Server (NTRS)

Lakshmi, Venkataraman

1998-01-01

Hydrological models have been calibrated and validated using catchment streamflows. However, using a point measurement does not guarantee correct spatial distribution of model computed heat fluxes, soil moisture and surface temperatures. With the advent of satellites in the late 70s, surface temperature is being measured two to four times a day from various satellite sensors and different platforms. The purpose of this paper is to demonstrate use of satellite surface temperature in (a) validation of model computed surface temperatures and (b) assimilation of satellite surface temperatures into a hydrological model in order to improve the prediction accuracy of soil moistures and heat fluxes. The assimilation is carried out by comparing the satellite and the model produced surface temperatures and setting the "true"temperature midway between the two values. Based on this "true" surface temperature, the physical relationships of water and energy balance are used to reset the other variables. This is a case of nudging the water and energy balance variables so that they are consistent with each other and the true" surface temperature. The potential of this assimilation scheme is demonstrated in the form of various experiments that highlight the various aspects. This study is carried over the Red-Arkansas basin in the southern United States (a 5 deg X 10 deg area) over a time period of a year (August 1987 - July 1988). The land surface hydrological model is run on an hourly time step. The results show that satellite surface temperature assimilation improves the accuracy of the computed surface soil moisture remarkably.