What caused the Extreme Storm Season over the North Atlantic and the UK in Winter 2013-14?

NASA Astrophysics Data System (ADS)

Leckebusch, G. C.; Wild, S.; Befort, D. J.

2015-12-01

In winter 2013-2014, the UK experienced exceptional stormy and rainy weather conditions. Concurrently, surface temperatures over large parts of central North America fell to near record minimum values. One potential driver for these cold conditions is discussed to be the increasingly warm surface waters of the tropical west Pacific. It has been suggested these increasing sea surface temperatures could also be the cause for extreme weather over the British Isles. Testing this hypothesis, we investigate mechanisms linking the tropical west Pacific and European wind storm activity. We focus on two research questions. Firstly: Was a chain of anomaly patterns with origin in the west Pacific present in the winter 2013-14? And secondly: Can centres of action along such a chain be identified with a strong interannual relationship in the recent past? Our results, using primarily ERA-Interim Reanalysis from 1979 to 2014, show an absolute maximum of wind storm frequency over the northeast Atlantic and the British Isles in winter 2013-14. We also find absolute minimum surface temperatures in central North America and increased convective activity over the tropical west Pacific in the same season. The winter 2013-14 was additionally characterized by anomalous warm sea surface temperatures over the subtropical northwest Atlantic. Although the interannual variability of wind storms in the northeast Atlantic and surface temperatures in North America are significantly anti-correlated, we cannot directly relate wind storm frequency with tropical west Pacific anomalies. We thus conclude that the conditions over the Pacific in winter 2013-14 were favourable but not sufficient to explain the record number of wind storms in this season. Instead, we suggest that warm north Atlantic sea surface temperature anomalies in combination with cold surface temperatures over North America played a more important role for generating higher wind storm counts over the northeast Atlantic and the UK.

Are we near the predictability limit of tropical Indo-Pacific sea surface temperatures?

NASA Astrophysics Data System (ADS)

Newman, Matthew; Sardeshmukh, Prashant D.

2017-08-01

The predictability of seasonal anomalies worldwide rests largely on the predictability of tropical sea surface temperature (SST) anomalies. Tropical forecast skill is also a key metric of climate models. We find, however, that despite extensive model development, the tropical SST forecast skill of the operational North American Multi-Model Ensemble (NMME) of eight coupled atmosphere-ocean models remains close both regionally and temporally to that of a vastly simpler linear inverse model (LIM) derived from observed covariances of SST, sea surface height, and wind fields. The LIM clearly captures the essence of the predictable SST dynamics. The NMME and LIM skills also closely track and are only slightly lower than the potential skill estimated using the LIM's forecast signal-to-noise ratios. This suggests that the scope for further skill improvement is small in most regions, except in the western equatorial Pacific where the NMME skill is currently much lower than the LIM skill.

El Nino-Induced Tropical Ocean/Land Energy Exchange in MERRA-2 and M2AMIP

NASA Technical Reports Server (NTRS)

Bosilovich, Michael G.; Robertson, Franklin R.

2017-01-01

Studies have shown the correlation and connection of surface temperatures across the globe, ocean and land, related to Tropical SSTs especially El Nino. This climate variability greatly influences regional weather and hydroclimate extremes (e.g. drought and flood). In this paper, we evaluate the relationship of temperatures across the tropical oceans and continents in MERRA-2, and also in a newly developed MERRA-2 AMIP ensemble simulation (M2AMIP). M2AMIP uses the same model and spatial resolution as MERRA-2, producing the same output diagnostics over 10 ensemble members. Composite El Nino temperature data are compared with observations to evaluate the land/sea contrast, variations and phase relationship. The temperature variations are related to surface heat fluxes and the atmospheric temperatures and transport, to identify the processes that lead to the lagged redistribution of heat in the tropics and beyond. Discernable cloud, radiation and data assimilation changes accompany the onset of El Nino affecting continental regions through the progression to and following the peak values. While the model represents these variations in general, regional strengths and weaknesses can be identified.

A Note on the Relationship of Temperature and Water Vapor over Oceans, as well as the Sea Surface Temperature Impact

NASA Technical Reports Server (NTRS)

Shie, C.-L.; Tao, W.-K.; Simpson, J.

2005-01-01

This note follows up on a recent study by Shie et al. (2005) and extends the investigation of the domain-averaged moisture-temperature (Q-T) relationship from the Tropics (i.e., the previous study) to the tropical Pacific, Atlantic and Indian Oceans. The Q and T data examined in this study are obtained from the GEOS-3 [Goddard Earth Observing System Version-3] global re-analysis monthly products. Similar to what was found earlier in the Tropics, Q is also found to increase with T over the entire oceanic region; however, Q increases faster with T over oceans than over the Tropics. The Q-T distribution for the Tropics is in a quasi-linear relationship, which is embedded in a global Q-T distribution that is, however, in a more complex curvilinear relationship. The Q-T distribution over the oceanic regions seems to fall within the lower bound (ie., the relatively colder and driver regime) of the tropical Q-T distribution. T over oceans is also found increasing with SST (sea surface temperature), which seemingly implies that an air mass might have gained heat more readily from a warmer ocean as compared to a colder ocean. Q is also found to increase with SST in a manner that quantitatively resembles an earlier finding by Stevens (1990). We also found that relative humidity exhibits similar behaviors for oceanic and tropical regions, respectively, i.e., it increases with both SST and T over oceans and increases with T in the Tropics (Shie et al. 2005). All these similar features found between oceanic and tropical regions seem to inform us that oceans occupy most of the Tropics and so play a key role in determining what have happened in the Tropics.

Clouds, surface temperature, and the tropical and subtropical radiation budget

NASA Technical Reports Server (NTRS)

Dhuria, Harbans L.; Kyle, H. Lee

1980-01-01

Solar energy drives both the Earth's climate and biosphere, but the absorbed energy is unevenly distributed over the Earth. The tropical regions receive excess energy which is then transported by atmospheric and ocean currents to the higher latitudes. All regions at a given latitude receive the same top of the atmosphere solar irradiance (insolation). However, the net radiation received from the Sun in the tropics and subtropics varies greatly from one region to another depending on local conditions. Over land, variations in surface albedo are important. Over both land and ocean, surface temperature, cloud amount, and cloud type are also important. The Nimbus-7 cloud and Earth radiation budget (ERB) data sets are used to examine the affect of these parameters.

The annual and interannual variabilities of precipitable water, surface wind speed, and sea surface temperature over the tropical Pacific

NASA Technical Reports Server (NTRS)

Liu, W. Timothy

1989-01-01

The Nimbus-7 Scanning Multichannel Microwave Radiometer (SSMR) provided simultaneous measurements of three geophysical parameters, each of which describing a certain aspect of the evolution of the 1982-1983 ENSO: the sea-surface temperature (T), precipitable water (W), and surface-wind speed (U). In this paper, values derived from the SSMR were compared with in situ measurements from ships, research buoys, and operational island stations in the tropical Pacific between January 1980 and October 1983, demonstrating the temporal and spatial coherence of the SSMR measurements. The results show that the variabilities of the surface convergence, sea surface temperature, and precipitable water are related. It was found that W anomalies were not always colocated with T anomalies, and that W anomalies were often associated with negative U anomalies, interpreted as surface convergence.

Tropical Convection and Climate Processes in a Cumulus Ensemble Model

NASA Technical Reports Server (NTRS)

Sui, Chung-Hsiung

1999-01-01

Local convective-radiative equilibrium states of the tropical atmosphere are determined by the following external forcing: 1) Insolation, 2) Surface heat and moisture exchanges (primarily radiation and evaporation), 3) Heating and moistening induced by large-scale circulation. Understanding the equilibrium states of the tropical atmosphere in different external forcing conditions is of vital importance for studying cumulus parameterization, climate feedbacks, and climate changes. We extend our previous study using the Goddard Cumulus Ensemble (GCE) Model which resolves convective-radiative processes more explicitly than global climate models do. Several experiments are carried out under fixed insolation and sea surface temperature. The prescribed SST consists of a uniform warm pool (29C) surrounded by uniform cold SST (26C). The model produces "Walker"-type circulation with the ascending branch of the model atmosphere more humid than the descending part, but the vertically integrated temperature does not show a horizontal gradient. The results are compared with satellite measured moisture by SSM/I (Special Sensor Microwave/Imager) and temperature by MSU in the ascending and descending tropical atmosphere. The vertically integrated temperature and humidity in the two model regimes are comparable to the observed values in the tropics.

Comparison of eastern tropical Pacific TEX86 and Globigerinoides ruber Mg/Ca derived sea surface temperatures: Insights from the Holocene and Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Hertzberg, Jennifer E.; Schmidt, Matthew W.; Bianchi, Thomas S.; Smith, Richard W.; Shields, Michael R.; Marcantonio, Franco

2016-01-01

The use of the TEX86 temperature proxy has thus far come to differing results as to whether TEX86 temperatures are representative of surface or subsurface conditions. In addition, although TEX86 temperatures might reflect sea surface temperatures based on core-top (Holocene) values, this relationship might not hold further back in time. Here, we investigate the TEX86 temperature proxy by comparing TEX86 temperatures to Mg/Ca temperatures of multiple species of planktonic foraminifera for two sites in the eastern tropical Pacific (on the Cocos and Carnegie Ridges) across the Holocene and Last Glacial Maximum. Core-top and Holocene TEX86H temperatures at both study regions agree well, within error, with the Mg/Ca temperatures of Globigerinoides ruber, a surface dwelling planktonic foraminifera. However, during the Last Glacial Maximum, TEX86H temperatures are more representative of upper thermocline temperatures, and are offset from G. ruber Mg/Ca temperatures by 5.8 °C and 2.9 °C on the Cocos Ridge and Carnegie Ridge, respectively. This offset between proxies cannot be reconciled by using different TEX86 temperature calibrations, and instead, we suggest that the offset is due to a deeper export depth of GDGTs at the LGM. We also compare the degree of glacial cooling at both sites based on both temperature proxies, and find that TEX86H temperatures greatly overestimate glacial cooling, especially on the Cocos Ridge. This study has important implications for applying the TEX86 paleothermometer in the eastern tropical Pacific.

Skilful multi-year predictions of tropical trans-basin climate variability

PubMed Central

Chikamoto, Yoshimitsu; Timmermann, Axel; Luo, Jing-Jia; Mochizuki, Takashi; Kimoto, Masahide; Watanabe, Masahiro; Ishii, Masayoshi; Xie, Shang-Ping; Jin, Fei-Fei

2015-01-01

Tropical Pacific sea surface temperature anomalies influence the atmospheric circulation, impacting climate far beyond the tropics. The predictability of the corresponding atmospheric signals is typically limited to less than 1 year lead time. Here we present observational and modelling evidence for multi-year predictability of coherent trans-basin climate variations that are characterized by a zonal seesaw in tropical sea surface temperature and sea-level pressure between the Pacific and the other two ocean basins. State-of-the-art climate model forecasts initialized from a realistic ocean state show that the low-frequency trans-basin climate variability, which explains part of the El Niño Southern Oscillation flavours, can be predicted up to 3 years ahead, thus exceeding the predictive skill of current tropical climate forecasts for natural variability. This low-frequency variability emerges from the synchronization of ocean anomalies in all basins via global reorganizations of the atmospheric Walker Circulation. PMID:25897996

Skilful multi-year predictions of tropical trans-basin climate variability.

PubMed

Chikamoto, Yoshimitsu; Timmermann, Axel; Luo, Jing-Jia; Mochizuki, Takashi; Kimoto, Masahide; Watanabe, Masahiro; Ishii, Masayoshi; Xie, Shang-Ping; Jin, Fei-Fei

2015-04-21

Tropical Pacific sea surface temperature anomalies influence the atmospheric circulation, impacting climate far beyond the tropics. The predictability of the corresponding atmospheric signals is typically limited to less than 1 year lead time. Here we present observational and modelling evidence for multi-year predictability of coherent trans-basin climate variations that are characterized by a zonal seesaw in tropical sea surface temperature and sea-level pressure between the Pacific and the other two ocean basins. State-of-the-art climate model forecasts initialized from a realistic ocean state show that the low-frequency trans-basin climate variability, which explains part of the El Niño Southern Oscillation flavours, can be predicted up to 3 years ahead, thus exceeding the predictive skill of current tropical climate forecasts for natural variability. This low-frequency variability emerges from the synchronization of ocean anomalies in all basins via global reorganizations of the atmospheric Walker Circulation.

Reassessment of ice-age cooling of the tropical ocean and atmosphere

USGS Publications Warehouse

Hostetler, S.W.; Mix, A.C.

1999-01-01

The CLIMAP project's reconstruction of past sea surface temperature inferred limited ice-age cooling in the tropical oceans. This conclusion has been controversial, however, because of the greater cooling indicated by other terrestrial and ocean proxy data. A new faunal sea surface temperature reconstruction, calibrated using the variation of foraminiferal species through time, better represents ice-age faunal assemblages and so reveals greater cooling than CLIMAP in the equatorial current systems of the eastern Pacific and tropical Atlantic oceans. Here we explore the climatic implications of this revised sea surface temperature field for the Last Glacial Maximum using an atmospheric general circulation model. Relative to model results obtained using CLIMAP sea surface temperatures, the cooler equatorial oceans modify seasonal air temperatures by 1-2??C or more across parts of South America, Africa and southeast Asia and cause attendant changes in regional moisture patterns. In our simulation of the Last Glacial Maximum, the Amazon lowlands, for example, are cooler and drier, whereas the Andean highlands are cooler and wetter than the control simulation. Our results may help to resolve some of the apparent disagreements between oceanic and continental proxy climate data. Moreover, they suggest a wind-related mechanism for enhancing the export of water vapour from the Atlantic to the Indo-Pacific oceans, which may link variations in deep-water production and high-latitude climate changes to equatorial sea surface temperatures.

The Carbon Cycle Response to Two El Nino Types: Observational Study

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

Chylek, Petr; Tans, Pieter; Christy, John

Here, we analyze monthly tropical near surface air temperature and Mauna Loa Observatory carbon dioxide (CO 2) data within 1960-2016 to identify different carbon cycle responses for two El Nino types: El Ninos originating in the central tropical Pacific (CP El Nino) and El Ninos originating in the eastern tropical Pacific (EP El Nino). We find significant differences between the two types of El Nino events with respect to time delay of the CO 2 rise rate that follows the increase in tropical near surface air temperatures caused by El Nino events. The average time lag of the CP Elmore » Nino is 4.0±1.7 months, while the mean time lag of EP El Nino is found to be 8.5±2.3 months. The average lag of all considered 1960-2016 El Ninos is 5.2±2.7 months. In contrast the sensitivity of CO2 growth rate to tropical near surface air temperature increase is determined to be about the same for both El Nino types equal to 2.8±0.9 ppmyr -1K -1 (or 5.9±1.9 GtCyr -1K -1). Our results should be useful for the understanding of the carbon cycle and constraining it in climate models.« less

The Carbon Cycle Response to Two El Nino Types: Observational Study

DOE PAGES

Chylek, Petr; Tans, Pieter; Christy, John; ...

2017-11-22

Here, we analyze monthly tropical near surface air temperature and Mauna Loa Observatory carbon dioxide (CO 2) data within 1960-2016 to identify different carbon cycle responses for two El Nino types: El Ninos originating in the central tropical Pacific (CP El Nino) and El Ninos originating in the eastern tropical Pacific (EP El Nino). We find significant differences between the two types of El Nino events with respect to time delay of the CO 2 rise rate that follows the increase in tropical near surface air temperatures caused by El Nino events. The average time lag of the CP Elmore » Nino is 4.0±1.7 months, while the mean time lag of EP El Nino is found to be 8.5±2.3 months. The average lag of all considered 1960-2016 El Ninos is 5.2±2.7 months. In contrast the sensitivity of CO2 growth rate to tropical near surface air temperature increase is determined to be about the same for both El Nino types equal to 2.8±0.9 ppmyr -1K -1 (or 5.9±1.9 GtCyr -1K -1). Our results should be useful for the understanding of the carbon cycle and constraining it in climate models.« less

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.

Interannual-to-decadal air-sea interactions in the tropical Atlantic region

NASA Astrophysics Data System (ADS)

Ruiz-Barradas, Alfredo

2001-09-01

The present research identifies modes of atmosphere-ocean interaction in the tropical Atlantic region and the mechanisms by which air-sea interactions influence the regional climate. Novelties of the present work are (1)the use of relevant ocean and atmosphere variables important to identity coupled variability in the system. (2)The use of new data sets, including realistic diabatic heating. (3)The study of interactions between ocean and atmosphere relevant at interannual-to-decadal time scales. Two tropical modes of variability are identified during the period 1958-1993, the Atlantic Niño mode and the Interhemispheric mode. Those modes have defined structures in both ocean and atmosphere. Anomalous sea surface temperatures and winds are associated to anomalous placement of the Intertropical Convergence Zone (ITCZ). They develop maximum amplitude during boreal summer and spring, respectively. The anomalous positioning of the ITCZ produces anomalous precipitation in some places like Nordeste, Brazil and the Caribbean region. Through the use of a diagnostic primitive equation model, it is found that the most important terms controlling local anomalous surface winds over the ocean are boundary layer temperature gradients and diabatic heating anomalies at low levels (below 780 mb). The latter is of particular importance in the deep tropics in producing the anomalous meridional response to the surface circulation. Simulated latent heat anomalies indicate that a thermodynamic feedback establishes positive feedbacks at both sides of the equator and west of 20°W in the deep tropics and a negative feedback in front of the north west coast of Africa for the Interhemispheric mode. This thermodynamic feedback only establishes negative feedbacks for the Atlantic Niño mode. Transients establish some connection between the tropical Atlantic and other basins. Interhemispheric gradients of surface temperature in the tropical Atlantic influence winds in the midlatitude North Atlantic but winds and heating of the midlatitude North Atlantic have little impact on the deep tropics. The remote influence of El Niño-Southern Oscillation in the tropical Atlantic, similar to the Interhemispheric mode, is the result of two mechanisms triggered by anomalous warming in the central and eastern tropical Pacific: enhancement of the Atlantic Walker circulation, and coupled intrusion of negative 200 mb geopotential height anomalies and negative sea level pressure anomalies that induce southwesterly surface wind anomalies in the northern tropical Atlantic.

NASA Tropical Rainfall Measurement Mission (TRMM): Effects of tropical rainfall on upper ocean dynamics, air-sea coupling and hydrologic cycle

NASA Technical Reports Server (NTRS)

Lagerloef, Gary; Busalacchi, Antonio J.; Liu, W. Timothy; Lukas, Roger B.; Niiler, Pern P.; Swift, Calvin T.

1995-01-01

This was a Tropical Rainfall Measurement Mission (TRMM) modeling, analysis and applications research project. Our broad scientific goals addressed three of the seven TRMM Priority Science Questions, specifically: What is the monthly average rainfall over the tropical ocean areas of about 10(exp 5) sq km, and how does this rain and its variability affect the structure and circulation of the tropical oceans? What is the relationship between precipitation and changes in the boundary conditions at the Earth's surface (e.g., sea surface temperature, soil properties, vegetation)? How can improved documentation of rainfall improve understanding of the hydrological cycle in the tropics?

Closing the Seasonal Ocean Surface Temperature Balance in the Eastern Tropical Oceans from Remote Sensing and Model Reanalyses

NASA Technical Reports Server (NTRS)

Roberts, J. Brent; Clayson, Carol A.

2012-01-01

The Eastern tropical ocean basins are regions of significant atmosphere-ocean interaction and are important to variability across subseasonal to decadal time scales. The numerous physical processes at play in these areas strain the abilities of coupled general circulation models to accurately reproduce observed upper ocean variability. Furthermore, limitations in the observing system of important terms in the surface temperature balance (e.g., turbulent and radiative heat fluxes, advection) introduce uncertainty into the analyses of processes controlling sea surface temperature variability. This study presents recent efforts to close the surface temperature balance through estimation of the terms in the mixed layer temperature budget using state-of-the-art remotely sensed and model-reanalysis derived products. A set of twelve net heat flux estimates constructed using combinations of radiative and turbulent heat flux products - including GEWEX-SRB, ISCCP-SRF, OAFlux, SeaFlux, among several others - are used with estimates of oceanic advection, entrainment, and mixed layer depth variability to investigate the seasonal variability of ocean surface temperatures. Particular emphasis is placed on how well the upper ocean temperature balance is, or is not, closed on these scales using the current generation of observational and model reanalysis products. That is, the magnitudes and spatial variability of residual imbalances are addressed. These residuals are placed into context within the current uncertainties of the surface net heat fluxes and the role of the mixed layer depth variability in scaling the impact of those uncertainties, particularly in the shallow mixed layers of the Eastern tropical ocean basins.

Tropical Storm Ernesto over Cuba

NASA Image and Video Library

2006-08-28

This infrared image shows Tropical Storm Ernesto over Cuba, from the Atmospheric Infrared Sounder AIRS on NASA Aqua satellite in August, 2006. Because infrared radiation does not penetrate through clouds, AIRS infrared images show either the temperature of the cloud tops or the surface of the Earth in cloud-free regions. The lowest temperatures (in purple) are associated with high, cold cloud tops that make up the top of the storm. In cloud-free areas the AIRS instrument will receive the infrared radiation from the surface of the Earth, resulting in the warmest temperatures (orange/red). http://photojournal.jpl.nasa.gov/catalog/PIA00510

Tropical Pacific Imagery - Satellite Products and Services Division/Office

Science.gov Websites

of Satellite and Product Operations Skip Navigation Link NESDIS banner image and link to NESDIS Home Page Default Office of Satellite and Product Operations banner image and link to OSPO DOC / NOAA Bleaching -- Ocean Color -- Sea/Lake Ice -- Sea Surface Height -- Sea Surface Temperatures -- Tropical

Tropical Atlantic Imagery - Satellite Products and Services Division/Office

Science.gov Websites

of Satellite and Product Operations Skip Navigation Link NESDIS banner image and link to NESDIS Home Page Default Office of Satellite and Product Operations banner image and link to OSPO DOC / NOAA Bleaching -- Ocean Color -- Sea/Lake Ice -- Sea Surface Height -- Sea Surface Temperatures -- Tropical

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

NASA Astrophysics Data System (ADS)

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

2014-09-01

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 forests tend to be warmer than grasslands and croplands because forest albedos tend to be lower than non-forest albedos. A lower forest albedo results in higher absorption of solar radiation and increased sensible warming that is not offset by the cooling effects of carbon uptake in extra-tropical regions. However, comparison of forest warming potential in the context of climate models is based on a coarse classification system of tropical, temperate, and boreal. There is considerable variation in climate within the broad latitudinal zonation of tropical, temperate, and boreal, and the relationship between biophysical (albedo) and biogeochemical (carbon uptake) mechanisms may not be constant within these broad zones. We compared wintertime forest and non-forest surface temperatures for the southeastern United States and found that forest surface temperatures shifted from being warmer than non-forest surface temperatures north of approximately 36°N to cooler south of 36°N. Our results suggest that the biophysical aspects of forests' influence on climate reinforce the biogeochemical aspects of forests' influence on climate south of 36°N. South of 36°N, both biophysical and biogeochemical properties of forests appear to support forestation as a climate mitigation policy. We also provide some quantitative evidence that evergreen forests tend to have cooler wintertime surface temperatures than deciduous forests that may be attributable to greater evapotranspiration rates.

The anomalous circulation associated with the ENSO-related west Pacific sea surface temperature gradient

USGS Publications Warehouse

Hoell, Andrew; Funk, Christopher C.

2013-01-01

The temporal evolution and distribution of Pacific SST as well as the near-surface tropical Pacific zonal wind, tropical divergence and vertical velocity are considerably different during ENSO events partitioned according to the strength of the WPG. Modifications to the tropical circulation result in changes to the Indo-west Pacific precipitation and vertically integrated energy budgets and are linked to strong and consistent circulation and precipitation modifications throughout the Northern Hemisphere during winter.

Microwave Imager Measures Sea Surface Temperature Through Clouds

NASA Technical Reports Server (NTRS)

2002-01-01

This image was acquired over Tropical Atlantic and U.S. East Coast regions on Aug. 22 - Sept. 23, 1998. Cloud data were collected by the Geostationary Operational Environmental Satellite (GOES). Sea Surface Temperature (SST) data were collected aboard the NASA/NASDA Tropical Rainfall Measuring Mission (TRMM) satellite by The TRMM Microwave Imager (TMI). TMI is the first satellite microwave sensor capable of accurately measuring sea surface temperature through clouds, as shown in this scene. For years scientists have known there is a strong correlation between sea surface temperature and the intensity of hurricanes. But one of the major stumbling blocks for forecasters has been the precise measurement of those temperatures when a storm begins to form. In this scene, clouds have been made translucent to allow an unobstructed view of the surface. Notice Hurricane Bonnie approaching the Carolina Coast (upper left) and Hurricane Danielle following roughly in its path (lower right). The ocean surface has been falsely colored to show a map of water temperature--dark blues are around 75oF, light blues are about 80oF, greens are about 85oF, and yellows are roughly 90oF. A hurricane gathers energy from warm waters found at tropical latitudes. In this image we see Hurricane Bonnie cross the Atlantic, leaving a cooler trail of water in its wake. As Hurricane Danielle followed in Bonnie's path, the wind speed of the second storm dropped markedly, as available energy to fuel the storm dropped off. But when Danielle left Bonnie's wake, wind speeds increased due to temperature increases in surface water around the storm. As a hurricane churns up the ocean, it's central vortex draws surface heat and water into the storm. That suction at the surface causes an upwelling of deep water. At depth, tropical ocean waters are significantly colder than water found near the surface. As they're pulled up to meet the storm, those colder waters essentially leave a footprint in the storm's wake which might last as long as two weeks. Forecasters can quantify the difference in surface temperatures between this footprint and the surrounding temperatures and use that information to better predict storm intensity. If another storm intersects with this cold water trail, it is likely to lose significant strength due to the fact that the colder water does not contain as much potential energy as warm water. TRMM Fact Sheet Predicting Hurricane Intensity Far from Land Remote Sensing Systems Image courtesy TRMM Project, Remote Sensing Systems, and Scientific Visualization Studio, NASA Goddard Space Flight Center

Extreme warmth and heat-stressed plankton in the tropics during the Paleocene-Eocene Thermal Maximum.

PubMed

Frieling, Joost; Gebhardt, Holger; Huber, Matthew; Adekeye, Olabisi A; Akande, Samuel O; Reichart, Gert-Jan; Middelburg, Jack J; Schouten, Stefan; Sluijs, Appy

2017-03-01

Global ocean temperatures rapidly warmed by ~5°C during the Paleocene-Eocene Thermal Maximum (PETM; ~56 million years ago). Extratropical sea surface temperatures (SSTs) met or exceeded modern subtropical values. With these warm extratropical temperatures, climate models predict tropical SSTs >35°C-near upper physiological temperature limits for many organisms. However, few data are available to test these projected extreme tropical temperatures or their potential lethality. We identify the PETM in a shallow marine sedimentary section deposited in Nigeria. On the basis of planktonic foraminiferal Mg/Ca and oxygen isotope ratios and the molecular proxy [Formula: see text], latest Paleocene equatorial SSTs were ~33°C, and [Formula: see text] indicates that SSTs rose to >36°C during the PETM. This confirms model predictions on the magnitude of polar amplification and refutes the tropical thermostat theory. We attribute a massive drop in dinoflagellate abundance and diversity at peak warmth to thermal stress, showing that the base of tropical food webs is vulnerable to rapid warming.

Relationship Between Sea Surface Temperature and Surface Heat Balance Trends in the Tropical Oceans: The Crucial Role of Surface Wind Trends

NASA Astrophysics Data System (ADS)

Cook, K. H.; Vizy, E. K.; Sun, X.

2016-12-01

Multiple atmospheric and ocean reanalyses are analyzed for 1980-2015 to understand annual-mean adjustments of the surface heat balance over the tropical oceans as the climate warms. Linear trends are examined, with statistical significance evaluated. While surface heat budgets and sea surface temperatures are mutually adjusted fields, insights into the physical processes of this adjustment and the implications for temperature trends can be identified. Two second-generation reanalyses, ERA-Interim and JRA-55, agree well on the distributions and magnitudes of trends in the net heat flux from the atmosphere to the ocean. Trends in the net longwave and sensible heat fluxes are generally small, and trends in solar radiation absorbed are only influential regionally and vary among the reanalyses. The largest contribution is from latent heat flux trends. Contributions to these trends associated with surface temperature (thermal-driving), 10-m wind (dynamical-driving) and specific humidity (hydrological-driving) trends are estimated. The dynamically-driven latent heat flux dominates and explains much of the regionality of the multi-decadal heat flux trends. However, trends in the net surface heat flux alone do not match the observed SSTs trends well, indicating that the redistribution of heat within the ocean mixed layer is also important. Ocean mixed layer heat budgets in various ocean reanalyses are examined to understand this redistribution, and we again identify a crucial role for changes in the surface wind. Acceleration of the tropical easterlies is associated with strengthening of the equatorial undercurrents in both the tropical Pacific and Atlantic. In the Pacific, where the EUC is also shoaling, the result is enhanced warm-water advection into the central Pacific. This advective warming is superimposed on cooling due to enhanced evaporation and equatorial upwelling, which are also associated with wind trends, to determine the observed pattern of SST trends.

Tropical Depression 6 Florence in the Atlantic

NASA Image and Video Library

2006-09-03

This infrared image shows Tropical Depression 6 Florence in the Atlantic, from the Atmospheric Infrared Sounder AIRS on NASA Aqua satellite in September, 2006. Because infrared radiation does not penetrate through clouds, AIRS infrared images show either the temperature of the cloud tops or the surface of the Earth in cloud-free regions. The lowest temperatures (in purple) are associated with high, cold cloud tops that make up the top of the storm. In cloud-free areas the AIRS instrument will receive the infrared radiation from the surface of the Earth, resulting in the warmest temperatures (orange/red). http://photojournal.jpl.nasa.gov/catalog/PIA00512

Synchronous interhemispheric Holocene climate trends in the tropical Andes

PubMed Central

Polissar, Pratigya J.; Abbott, Mark B.; Wolfe, Alexander P.; Vuille, Mathias; Bezada, Maximiliano

2013-01-01

Holocene variations of tropical moisture balance have been ascribed to orbitally forced changes in solar insolation. If this model is correct, millennial-scale climate evolution should be antiphased between the northern and southern hemispheres, producing humid intervals in one hemisphere matched to aridity in the other. Here we show that Holocene climate trends were largely synchronous and in the same direction in the northern and southern hemisphere outer-tropical Andes, providing little support for the dominant role of insolation forcing in these regions. Today, sea-surface temperatures in the equatorial Pacific Ocean modulate rainfall variability in the outer tropical Andes of both hemispheres, and we suggest that this mechanism was pervasive throughout the Holocene. Our findings imply that oceanic forcing plays a larger role in regional South American climate than previously suspected, and that Pacific sea-surface temperatures have the capacity to induce abrupt and sustained shifts in Andean climate. PMID:23959896

Origin of low-frequency (intraseasonal) oscillations in the tropical atmosphere. II - Structure and propagation of mobile wave-CISK modes and their modification by lower boundary forcings

NASA Technical Reports Server (NTRS)

Sui, Chung-Hsiung; Lau, Ka-Ming

1989-01-01

An improved treatment of diabatic heating due to moist convection is introduced into the dynamical model of Lau and Peng (1987) to study the origin of intraseasonal oscillations in the tropics. It is found that the periods of slow-moving wave-CISK disturbances in the tropical troposphere with fixed sea surface temperature vary from 20 to 50 days. The results suggest that heating in the lower troposphere may be important in slowing down the wave-CISK modes. Also, it is shown that the intraseasonal oscillation can propagate around the globe even when the associated deep convection is only confined over warm sea surface temperatures.

The Interrelationship Between Temperature Changes in the Free Atmosphere and Sea Surface Temperature Changes

NASA Astrophysics Data System (ADS)

Newell, Reginald E.; Wu, Zhong-Xiang

1992-03-01

Fields of sea surface temperature anomalies from the Global Ocean Surface Temperature Atlas (GOSTA) and microwave sounding measurements (MSU) of temperature in the troposphere are examined separately and together for the 1979-1988 period. Global correlation patterns of both sets of fields are investigated at a range of leads and lags up to 6 months and exhibit a wide range of correlation structure. There are regions, such as the tropical eastern Pacific, where sea surface temperature anomalies persist for several months and are associated with local air temperature anomalies; in this particular example, about 0.7°C air temperature change is associated with a 1.0°C sea temperature change. By contrast, some ocean regions and many atmospheric regions, mostly in middle and high latitude, show only local spatial correlations that disappear completely in a month or two. The most persistent and extensive spatial correlation patterns are quite different for the sea and the air. In the sea the "butterfly" pattern of the Pacific is the most important and reverses sign between the eastern equatorial Pacific and the western Pacific and subtropics. In the warm phase the temperature anomalies associated with this pattern are similar to the correlation pattern. For the atmosphere the main correlation pattern is an equatorial belt with no sign changes in the tropics; this pattern is linked to the oceanic El Niño mode. In the warm phase the temperature anomalies show peak values on both sides of the equator in the eastern and central Pacific. Based mainly on the results from the spatial patterns, certain regions are selected for intercomparison of time series. In the tropical eastern Pacific the sea leads the air by about a month while in the Gulf Stream and Kuroshio regions the sequence is reversed.

Temporal Changes in the Observed Relationship between Cloud Cover and Surface Air Temperature.

NASA Astrophysics Data System (ADS)

Sun, Bomin; Groisman, Pavel Ya.; Bradley, Raymond S.; Keimig, Frank T.

2000-12-01

The relationship between cloud cover and near-surface air temperature and its decadal changes are examined using the hourly synoptic data for the past four to six decades from five regions of the Northern Hemisphere: Canada, the United States, the former Soviet Union, China, and tropical islands of the western Pacific. The authors define the normalized cloud cover-surface air temperature relationship, NOCET or dT/dCL, as a temperature anomaly with a unit (one-tenth) deviation of total cloud cover from its average value. Then mean monthly NOCET time series (night- and daytime, separately) are area-averaged and parameterized as functions of surface air humidity and snow cover. The day- and nighttime NOCET variations are strongly anticorrelated with changes in surface humidity. Furthermore, the daytime NOCET changes are positively correlated to changes in snow cover extent. The regionally averaged nighttime NOCET varies from 0.05 K tenth1 in the wet Tropics to 1.0 K tenth1 at midlatitudes in winter. The daytime regional NOCET ranges from 0.4 K tenth1 in the Tropics to 0.7 K tenth1 at midlatitudes in winter.The authors found a general strengthening of a daytime surface cooling during the post-World War II period associated with cloud cover over the United States and China, but a minor reduction of this cooling in higher latitudes. Furthermore, since the 1970s, a prominent increase in atmospheric humidity has significantly weakened the effectiveness of the surface warming (best seen at nighttime) associated with cloud cover.The authors apportion the spatiotemporal field of interactions between total cloud cover and surface air temperature into a bivariate relationship (described by two equations, one for daytime and one for nighttime) with surface air humidity and snow cover and two constant factors. These factors are invariant in space and time domains. It is speculated that they may represent empirical estimates of the overall cloud cover effect on the surface air temperature.

Air temperature change in the northern and southern tropical Andes linked to North-Atlantic stadials and Greenland interstadials

NASA Astrophysics Data System (ADS)

Urrego, Dunia H.; Hooghiemstra, Henry

2016-04-01

We use eight pollen records reflecting climatic and environmental change from northern and southern sites in the tropical Andes. Our analysis focuses on the signature of millennial-scale climate variability during the last 30,000 years, in particular the Younger Dryas (YD), Heinrich stadials (HS) and Greenland interstadials (GI). We identify rapid responses of the vegetation to millennial-scale climate variability in the tropical Andes. The signature of HS and the YD are generally recorded as downslope migrations of the upper forest line (UFL), and are likely linked to air temperature cooling. The GI1 signal is overall comparable between northern and southern records and indicates upslope UFL migrations and warming in the tropical Andes. Our marker for lake level changes indicates a north to south difference that could be related to moisture availability. The direction of air temperature change recorded by the Andean vegetation is consistent with millennial-scale cryosphere and sea surface temperature records from the American tropics, but suggests a potential difference between the magnitude of temperature change in the ocean and the atmosphere.

Tropical Pacific variability as a key pacemaker of the global warming staircase

NASA Astrophysics Data System (ADS)

Kosaka, Y.; Xie, S. P.

2016-12-01

Global-mean surface temperature (GMST) has increased since the 19th century with notable interdecadal accelerations and slowdowns, forming the global-warming "staircase". The last step of this staircase is the surface warming slowdown since the late 1990s, for which the transition of the Interdecadal Pacific Oscillation (IPO) from a positive to negative state has been suggested as the leading mechanism. To examine the role of IPO in the entire warming staircase, a long pacemaker experiment is performed with a coupled climate model where tropical Pacific sea surface temperatures are forced to follow the observed evolution since the late 19th century. The pacemaker experiment successfully reproduces the staircase-like global warming remarkably well since 1900. Without the tropical Pacific effect, the same model produces a continual warming from the 1900s to the 1960 followed by rapid warming. The successful reproduction identifies the tropical Pacific decadal variability as a key pacemaker of the GMST staircase. We further propose a method to remove internal variability from observed GMST changes for real-time monitoring of anthropogenic warming.

Causes of Upper-Ocean Temperature Anomalies in the Tropical North Atlantic

NASA Astrophysics Data System (ADS)

Rugg, A.; Foltz, G. R.; Perez, R. C.

2016-02-01

Hurricane activity and regional rainfall are strongly impacted by upper ocean conditions in the tropical North Atlantic, defined as the region between the equator and 20°N. A previous study analyzed a strong cold sea surface temperature (SST) anomaly that developed in this region during early 2009 and was recorded by the Pilot Research Array in the Tropical Atlantic (PIRATA) moored buoy at 4°N, 23°W (Foltz et al. 2012). The same mooring shows a similar cold anomaly in the spring of 2015 as well as a strong warm anomaly in 2010, offering the opportunity for a more comprehensive analysis of the causes of these events. In this study we examine the main causes of the observed temperature anomalies between 1998 and 2015. Basin-scale conditions during these events are analyzed using satellite SST, wind, and rain data, as well as temperature and salinity profiles from the NCEP Global Ocean Data Assimilation System. A more detailed analysis is conducted using ten years of direct measurements from the PIRATA mooring at 4°N, 23°W. Results show that the cooling and warming anomalies were caused primarily by wind-driven changes in surface evaporative cooling, mixed layer depth, and upper-ocean vertical velocity. Anomalies in surface solar radiation acted to damp the wind-driven SST anomalies in the latitude bands of the ITCZ (3°-8°N). Basin-scale analyses also suggest a strong connection between the observed SST anomalies and the Atlantic Meridional Mode, a well-known pattern of SST and surface wind anomalies spanning the tropical Atlantic.

An 800-Year Tropical Atlantic Sea Surface Temperature Variability Record From the Cariaco Basin, Venezuela

NASA Astrophysics Data System (ADS)

Black, D. E.; Thunell, R. C.; Kaplan, A.; Abahazi, M. A.; Tappa, E. J.

2007-05-01

Here we present an eight century tropical Atlantic SST record based on foraminiferal Mg/Ca recovered from Cariaco Basin sediments that have been calibrated to historical instrumental SSTs. Spatial correlations indicate that the proxy record is representative of SSTs over much of the Caribbean and tropical Atlantic. The Mg/Ca-SST record also correlates well with global land and sea surface temperature anomalies, and captures decadal-scale variations in Atlantic tropical storm and hurricane frequency over the late-19th and 20th centuries. The long-term record displays a surprising amount of variability for a tropical location under essentially modern boundary conditions. The tropical North Atlantic does not appear to have experienced a pronounced Medieval Warm Period relative to the complete record. However, strong Little Ice Age cooling of as much as 3 °C occurred between A. D. 1525 and 1625. Spring SSTs gradually rose between A. D. 1650 and 1900 followed by a 2.5 °C warming over the twentieth century. Viewed in the context of the complete record, twentieth century temperatures are not the warmest in the entire record on average, but they do show the largest increase in magnitude and fastest rate of SST change over the last eight hundred years. Spectral analysis of the Mg/Ca-SST data suggests that 2-5 and ~13 year SST variability that is characteristic of tropical Atlantic instrumental records may change through time.

A PV view of the zonal mean distribution of temperature and wind in the extratropical troposphere

NASA Technical Reports Server (NTRS)

Sun, De-Zheng; Lindzen, Richard S.

1994-01-01

The dependence of the temperature and wind distribution of the zonal mean flow in the extratropical troposphere on the gradient of pontential vorticity along isentropes is examined. The extratropics here refer to the region outside the Hadley circulation. Of particular interest is whether the distribution of temperature and wind corresponding to a constant potential vorticity (PV) along isentropes resembles the observed, and the implications of PV homogenization along isentropes for the role of the tropics. With the assumption that PV is homogenized along isentropes, it is found that the temperature distribution in the extratropical troposphere may be determined by a linear, first-order partial differential equation. When the observed surface temperature distribution and tropical lapse rate are used as the boundary conditions, the solution of the equation is close to the observed temperature distribution except in the upper troposphere adjacent to the Hadley circulation, where the troposphere with no PV gradient is considerably colder. Consequently, the jet is also stronger. It is also found that the meridional distribution of the balanced zonal wind is very sensitive to the meridional distribution of the tropopause temperature. The result may suggest that the requirement of the global momentum balance has no practical role in determining the extratropical temperature distribution. The authors further investigated the sensitivity of the extratropical troposphere with constant PV along isentropes to changes in conditions at the tropical boundary (the edge of the Hadley circulation). It is found that the temperature and wind distributions in the extratropical troposphere are sensitive to the vertical distribution of PV at the tropical boundary. With a surface distribution of temperature that decreases linearly with latitude, the jet maximum occurs at the tropical boundary and moves with it. The overall pattern of wind distribution is not sensitive to the change of the position of the tropical boundary. Finally, the temperature and wind distributions of an extratropical troposphere with a finite PV gradient are calculated. It is found that the larger the isentropic PV gradient, the warmer the troposphere and the weaker the jet.

Regional patterns of the change in annual-mean tropical rainfall under global warming

NASA Astrophysics Data System (ADS)

Huang, P.

2013-12-01

Projection of the change in tropical rainfall under global warming is a major challenge with great societal implications. The current study analyzes the 18 models from the Coupled Models Intercomparison Project, and investigates the regional pattern of annual-mean rainfall change under global warming. With surface warming, the climatological ascending pumps up increased surface moisture and leads rainfall increase over the tropical convergence zone (wet-get-wetter effect), while the pattern of sea surface temperature (SST) increase induces ascending flow and then increasing rainfall over the equatorial Pacific and the northern Indian Ocean where the local oceanic warming exceeds the tropical mean temperature increase (warmer-get-wetter effect). The background surface moisture and SST also can modify warmer-get-wetter effect: the former can influence the moisture change and contribute to the distribution of moist instability change, while the latter can suppress the role of instability change over the equatorial eastern Pacific due to the threshold effect of convection-SST relationship. The wet-get-wetter and modified warmer-get-wetter effects form a hook-like pattern of rainfall change over the tropical Pacific and an elliptic pattern over the northern Indian Ocean. The annual-mean rainfall pattern can be partly projected based on current rainfall climatology, while it also has great uncertainties due to the uncertain change in SST pattern.

Comparison of cropland and forest surface temperatures across the conterminous United States

EPA Science Inventory

Global climate models (GCM) investigating the effects of land cover on climate have found that replacing extra-tropical forest with cropland promotes cooling. We compared cropland and forest surface temperatures across the continental United States in 16 cells that were approxim...

Interannual Rainfall Variability in North-East Brazil: Observation and Model Simulation

NASA Astrophysics Data System (ADS)

Harzallah, A.; Rocha de Aragão, J. O.; Sadourny, R.

1996-08-01

The relationship between interannual variability of rainfall in north-east Brazil and tropical sea-surface temperature is studied using observations and model simulations. The simulated precipitation is the average of seven independent realizations performed using the Laboratoire de Météorologie Dynamique atmospheric general model forced by the 1970-1988 observed sea-surface temperature. The model reproduces very well the rainfall anomalies (correlation of 091 between observed and modelled anomalies). The study confirms that precipitation in north-east Brazil is highly correlated to the sea-surface temperature in the tropical Atlantic and Pacific oceans. Using the singular value decomposition method, we find that Nordeste rainfall is modulated by two independent oscillations, both governed by the Atlantic dipole, but one involving only the Pacific, the other one having a period of about 10 years. Correlations between precipitation in north-east Brazil during February-May and the sea-surface temperature 6 months earlier indicate that both modes are essential to estimate the quality of the rainy season.

Quantifying Tropical Glacier Mass Balance Sensitivity to Climate Change Through Regional-Scale Modeling and The Randolph Glacier Inventory

NASA Astrophysics Data System (ADS)

Malone, A.

2017-12-01

Quantifying mass balance sensitivity to climate change is essential for forecasting glacier evolution and deciphering climate signals embedded in archives of past glacier changes. Ideally, these quantifications result from decades of field measurement, remote sensing, and a hierarchy modeling approach, but in data-sparse regions, such as the Himalayas and tropical Andes, regional-scale modeling rooted in first principles provides a first-order picture. Previous regional-scaling modeling studies have applied a surface energy and mass balance approach in order to quantify equilibrium line altitude sensitivity to climate change. In this study, an expanded regional-scale surface energy and mass balance model is implemented to quantify glacier-wide mass balance sensitivity to climate change for tropical Andean glaciers. Data from the Randolph Glacier Inventory are incorporated, and additional physical processes are included, such as a dynamic albedo and cloud-dependent atmospheric emissivity. The model output agrees well with the limited mass balance records for tropical Andean glaciers. The dominant climate variables driving interannual mass balance variability differ depending on the climate setting. For wet tropical glaciers (annual precipitation >0.75 m y-1), temperature is the dominant climate variable. Different hypotheses for the processes linking wet tropical glacier mass balance variability to temperature are evaluated. The results support the hypothesis that glacier-wide mass balance on wet tropical glaciers is largely dominated by processes at the lowest elevation where temperature plays a leading role in energy exchanges. This research also highlights the transient nature of wet tropical glaciers - the vast majority of tropical glaciers and a vital regional water resource - in an anthropogenic warming world.

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

Xiang, Baoqiang; Zhao, Ming; Held, Isaac M.

The severity of the double Intertropical Convergence Zone (DI) problem in climate models can be measured by a tropical precipitation asymmetry index (PAI), indicating whether tropical precipitation favors the Northern Hemisphere or the Southern Hemisphere. Examination of 19 Coupled Model Intercomparison Project phase 5 models reveals that the PAI is tightly linked to the tropical sea surface temperature (SST) bias. As one of the factors determining the SST bias, the asymmetry of tropical net surface heat flux in Atmospheric Model Intercomparison Project (AMIP) simulations is identified as a skillful predictor of the PAI change from an AMIP to a coupledmore » simulation, with an intermodel correlation of 0.90. Using tropical top-of-atmosphere (TOA) fluxes, the correlations are lower but still strong. However, the extratropical asymmetries of surface and TOA fluxes in AMIP simulations cannot serve as useful predictors of the PAI change. Furthermore, this study suggests that the largest source of the DI bias is from the tropics and from atmospheric models.« less

Model finds bigger, stronger tropical cyclones with warming seas

NASA Astrophysics Data System (ADS)

Schultz, Colin

2014-03-01

In the wake of powerful tropical cyclones such as Hurricanes Sandy and Katrina and Typhoon Haiyan, questions about the likely effect of climate change on tropical cyclone activity are on the public's mind. The interactions between global warming and cyclone activity, however, are complex, with rising sea surface temperatures, changing energy distributions, and altered atmospheric dynamics all having some effect.

The Teleconnection Between Atlantic Sea Surface Temperature and Eastern Pacific Tropical Cyclones

NASA Astrophysics Data System (ADS)

Patricola, C. M.; Saravanan, R.; Chang, P.

2016-12-01

The El Niño-Southern Oscillation (ENSO) is a major source of seasonal tropical cyclone (TC) predictability, in both local and remote ocean basins. Unusually warm eastern tropical Pacific sea-surface temperature (SST) during El Niño tends not only to enhance local TC activity in the eastern North Pacific (ENP) but also to suppress Atlantic TCs via well-known teleconnections. Here, we demonstrate that Atlantic SST variability likewise exerts a significant influence on remote TC activity in the eastern Pacific basin using observations and 27 km resolution tropical channel model simulations. Observed and simulated accumulated cyclone energy in the ENP is substantially reduced during the positive phase of the Atlantic Meridional Mode (AMM), which is characterized by warm and cool SST anomalies in the northern and southern tropical Atlantic respectively, and vice versa during the cool AMM phase. We find that the observed anti-correlation in seasonal TC activity between the Atlantic and ENP basins is driven by interannual climate variability in both the tropical Pacific (ENSO) and Atlantic (AMM). The physical mechanisms that drive the teleconnection between Atlantic SST and ENP TC activity will also be presented. This work provides information that can be used to improve seasonal forecasts and future projections of ENP tropical cyclone activity.

Comparison of cropland and forest surface temperatures across the conterminous United States

Treesearch

James D. Wickham; Timothy G. Wade; Kurt H. Riitters

2012-01-01

Global climate models (GCM) investigating the effects of land cover on climate have found that replacing extra-tropical forest with cropland promotes cooling. We compared cropland and forest surface temperatures across the continental United States in 16 cells that were approximately 1◦ × 2◦ using 1 km2 MODIS land surface...

Predicting the severity of spurious “double ITCZ” problem in CMIP5 coupled models from AMIP simulations [Tropical versus extratropical origins of the spurious 'double ITCZ' in coupled climate models

DOE PAGES

Xiang, Baoqiang; Zhao, Ming; Held, Isaac M.; ...

2017-02-13

The severity of the double Intertropical Convergence Zone (DI) problem in climate models can be measured by a tropical precipitation asymmetry index (PAI), indicating whether tropical precipitation favors the Northern Hemisphere or the Southern Hemisphere. Examination of 19 Coupled Model Intercomparison Project phase 5 models reveals that the PAI is tightly linked to the tropical sea surface temperature (SST) bias. As one of the factors determining the SST bias, the asymmetry of tropical net surface heat flux in Atmospheric Model Intercomparison Project (AMIP) simulations is identified as a skillful predictor of the PAI change from an AMIP to a coupledmore » simulation, with an intermodel correlation of 0.90. Using tropical top-of-atmosphere (TOA) fluxes, the correlations are lower but still strong. However, the extratropical asymmetries of surface and TOA fluxes in AMIP simulations cannot serve as useful predictors of the PAI change. Furthermore, this study suggests that the largest source of the DI bias is from the tropics and from atmospheric models.« less

Response to "The Iris Hypothesis: A Negative or Positive Cloud Feedback?"

NASA Technical Reports Server (NTRS)

Chou, Ming-Dah; Lindzen, Richard S.; Hou, Arthur Y.; Lau, William K. M. (Technical Monitor)

2001-01-01

Based on radiance measurements of Japan's Geostationary Meteorological Satellite, Lindzen et al. found that the high-level cloud cover averaged over the tropical western Pacific decreases with increasing sea surface temperature. They further found that the response of high-level clouds to the sea surface temperature had an effect of reducing the magnitude of climate change, which is referred as a negative climate feedback. Lin et al. reassessed the results found by Lindzen et al. by analyzing the radiation and clouds derived from the Tropical Rainfall Measuring Mission Clouds and the Earth's Radiant Energy System measurements. They found a weak positive feedback between high-level clouds and the surface temperature. We have found that the approach taken by Lin et al. to estimating the albedo and the outgoing longwave radiation is incorrect and that the inferred climate sensitivity is unreliable.

Spatial and Temporal Inter-Relationship between Anomalies and Trends of Temperature, Moisture, Cloud Cover and OLR as Observed by AIRS/AMSU on Aqua

NASA Technical Reports Server (NTRS)

Susskind, Joel; Molnar, Gyula

2009-01-01

AIRS/AMSU is the advanced IR/MW atmospheric sounding system launched on EOS Aqua in May 2002. Products derived from AIRS/AMSU by the AIRS Science Team include surface skin temperature and atmospheric temperature profiled; atmospheric humidity profiles, fractional cloud clover and cloud top pressure, and OLR. Products covering the period September 2002 through the present have been derived from AIRS/AMSU using the AIRS Science Team Version 5 retrieval algorithm. In this paper, we will show results covering the time period September 2006 - November 2008. This time period is marked by a substantial warming trend of Northern Hemisphere Extra-tropical land surface skin temperatures, as well as pronounced El Nino - La Nina episodes. These both influence the spatial and temporal anomaly patterns of atmospheric temperature and moisture profiles, as well as of cloud cover and Clear Sky and All Sky OLR. The relationships between temporal and spatial anomalies of these parameters over this time period, as determined from AIRS/AMSU observations, will be shown with particular emphasis on which contribute significantly to OLR anomalies in each of the tropics and extra-tropics. Results will also be shown to evaluate the anomalies and trends of temperature profiles and OLR as determined from analysis of AIRS/AMSU data. Global and regional trends during the 6 1/3 year time period are not necessarily indicative of what has happened in the past, or what may happen in the future. Nevertheless, the inter-relationships of spatial and temporal anomalies of atmospheric geophysical parameters with those of surface skin temperature are indicative of climate processes, and can be used to test the performance of climate models when driven by changes in surface temperatures.

Advancing decadal-scale climate prediction in the North Atlantic sector.

PubMed

Keenlyside, N S; Latif, M; Jungclaus, J; Kornblueh, L; Roeckner, E

2008-05-01

The climate of the North Atlantic region exhibits fluctuations on decadal timescales that have large societal consequences. Prominent examples include hurricane activity in the Atlantic, and surface-temperature and rainfall variations over North America, Europe and northern Africa. Although these multidecadal variations are potentially predictable if the current state of the ocean is known, the lack of subsurface ocean observations that constrain this state has been a limiting factor for realizing the full skill potential of such predictions. Here we apply a simple approach-that uses only sea surface temperature (SST) observations-to partly overcome this difficulty and perform retrospective decadal predictions with a climate model. Skill is improved significantly relative to predictions made with incomplete knowledge of the ocean state, particularly in the North Atlantic and tropical Pacific oceans. Thus these results point towards the possibility of routine decadal climate predictions. Using this method, and by considering both internal natural climate variations and projected future anthropogenic forcing, we make the following forecast: over the next decade, the current Atlantic meridional overturning circulation will weaken to its long-term mean; moreover, North Atlantic SST and European and North American surface temperatures will cool slightly, whereas tropical Pacific SST will remain almost unchanged. Our results suggest that global surface temperature may not increase over the next decade, as natural climate variations in the North Atlantic and tropical Pacific temporarily offset the projected anthropogenic warming.

Determination of tropical cyclone surface pressure and winds from satellite microwave data

NASA Technical Reports Server (NTRS)

Kidder, S. Q.

1979-01-01

An approach to the problem of deducing wind speed and pressure around tropical cyclones is presented. The technique, called the Surface Wind Inference from Microwave data (SWIM technique, uses satellites microwave sounder data to measure upper tropospheric temperature anomalies which may then be related to surface pressure anomalies through the hydrostatic and radiative transfer equations. Surface pressure gradients outside of the radius of maximum wind are estimated for the first time. Future instruments may be able to estimate central pressure with + or - 0/1 kPa accuracy.

Role of internal variability in recent decadal to multidecadal tropical Pacific climate changes

NASA Astrophysics Data System (ADS)

Bordbar, Mohammad Hadi; Martin, Thomas; Latif, Mojib; Park, Wonsun

2017-05-01

While the Earth's surface has considerably warmed over the past two decades, the tropical Pacific has featured a cooling of sea surface temperatures in its eastern and central parts, which went along with an unprecedented strengthening of the equatorial trade winds, the surface component of the Pacific Walker Circulation (PWC). Previous studies show that this decadal trend in the trade winds is generally beyond the range of decadal trends simulated by climate models when forced by historical radiative forcing. There is still a debate on the origin of and the potential role that internal variability may have played in the recent decadal surface wind trend. Using a number of long control (unforced) integrations of global climate models and several observational data sets, we address the question as to whether the recent decadal to multidecadal trends are robustly classified as an unusual event or the persistent response to external forcing. The observed trends in the tropical Pacific surface climate are still within the range of the long-term internal variability spanned by the models but represent an extreme realization of this variability. Thus, the recent observed decadal trends in the tropical Pacific, though highly unusual, could be of natural origin. We note that the long-term trends in the selected PWC indices exhibit a large observational uncertainty, even hindering definitive statements about the sign of the trends.