Publications

Export 100 results:
Sort by: Author [ Title  (Asc)] Type Year
A B C D E F G H I J K [L] M N O P Q R S T U V W X Y Z   [Show ALL]
A
Diao, Y, Xie SP, Luo DH.  2015.  Asymmetry of winter European surface air temperature extremes and the North Atlantic Oscillation. Journal of Climate. 28:517-530.   10.1175/jcli-d-13-00642.1   AbstractWebsite

Interannual variations of winter warm and cold extremes in Europe are investigated. It is found that the variations are closely connected to the phase of the North Atlantic Oscillation (NAO). The leading EOF of the winter cold (warm) surface air temperature (SAT) extreme frequency shows an enhanced occurrence over western (eastern) Europe. The SAT probability distribution function of the cold extreme winter exhibits both a decrease of the mean SAT and a marked increase in SAT variance, whereas it shows only a shift of the mean SAT to the warmer side for extreme warm winters. This study reveals an asymmetry in location between the cold and warm extremes, caused by the NAO modulations of blocking events and other submonthly variations. Winters with frequent cold extremes are mainly accompanied by the eastern Atlantic blocking. The circulation causes not only marked local cooling but also increased SAT gradient, resulting in both enhanced SAT variance and increased occurrence of cold extremes. By contrast, winters with frequent warm extremes are associated with the northeast-southwest tilted positive NAO pattern. The warm advection by the submonthly perturbations is responsible for the development of warm extremes. The reduced SAT gradient due to enhanced warm advection weakens SAT variance over northern Europe. Thus, the cold extremes are larger in terms of deviations from the monthly mean than the warm extremes.

Kamae, Y, Li XC, Xie SP, Ueda H.  2017.  Atlantic effects on recent decadal trends in global monsoon. Climate Dynamics. 49:3443-3455.   10.1007/s00382-017-3522-3   AbstractWebsite

Natural climate variability contributes to recent decadal climate trends. Specifically the trends during the satellite era since 1979 include Atlantic and Indian Ocean warming and Pacific cooling associated with phase shifts of the Atlantic Multidecadal Oscillation and the Pacific Decadal Oscillation, and enhanced global monsoon (GM) circulation and rainfall especially in the Northern Hemisphere. Here we evaluate effects of the oceanic changes on the global and regional monsoon trends by partial ocean temperature restoring experiments in a coupled atmosphere-ocean general circulation model. Via trans-basin atmosphere-ocean teleconnections, the Atlantic warming drives a global pattern of sea surface temperature change that resembles observations, giving rise to the enhanced GM. The tropical Atlantic warming and the resultant Indian Ocean warming favor subtropical deep-tropospheric warming in both hemispheres, resulting in the enhanced monsoon circulations and precipitation over North America, South America and North Africa. The extratropical North Atlantic warming makes an additional contribution to the monsoon enhancement via Eurasian continent warming and resultant land-sea thermal gradient over Asia. The results of this study suggest that the Atlantic multidecadal variability can explain a substantial part of global climate variability including the recent decadal trends of GM.

Li, XC, Xie SP, Gille ST, Yoo C.  2016.  Atlantic-induced pan-tropical climate change over the past three decades. Nature Climate Change. 6:275-+.   10.1038/nclimate2840   AbstractWebsite

During the past three decades, tropical sea surface temperature (SST) has shown dipole-like trends, with warming over the tropical Atlantic and Indo-western Pacific but cooling over the eastern Pacific. Competing hypotheses relate this cooling, identified as a driver of the global warming hiatus(1,2), to the warming trends in either the Atlantic(3,4) or Indian Ocean(5). However, the mechanisms, the relative importance and the interactions between these teleconnections remain unclear. Using a state-of-the-art climate model, we show that the Atlantic plays a key role in initiating the tropical-wide teleconnection, and the Atlantic-induced anomalies contribute similar to 55-75% of the tropical SST and circulation changes during the satellite era. The Atlantic warming drives easterly wind anomalies over the Indo-western Pacific as Kelvin waves and westerly anomalies over the eastern Pacific as Rossby waves. The wind changes induce an Indo-western Pacific warming through the wind-evaporation-SST effect(6,7), and this warming intensifies the La Nina-type response in the tropical Pacific by enhancing the easterly trade winds and through the Bjerknes ocean dynamical processes(8). The teleconnection develops into a tropical-wide SST dipole pattern. This mechanism, supported by observations and a hierarchy of climate models, reveals that the tropical ocean basins are more tightly connected than previously thought.

Yang, L, Liu JW, Ren ZP, Xie SP, Zhang SP, Gao SH.  2018.  Atmospheric conditions for advection-radiation fog over the western Yellow Sea. Journal of Geophysical Research-Atmospheres. 123:5455-5468.   10.1029/2017jd028088   AbstractWebsite

Advection fog occurs usually when warm and moist air flows over cold sea surface. It is occasionally reported that the fog air temperature falls below sea surface temperature (called here the sea fog with sea surface heating [ssH]) due to longwave radiation cooling at fog top. Using 8-year buoy observations, this study reveals that about 33% of the time, the advection fog is with ssH in the western Yellow Sea. By synthesizing long-term observations from meteorological stations, atmospheric soundings, and offshore buoys, this study further investigates the marine atmospheric boundary layer (MABL) structure and atmospheric circulation associated with the ssH sea fog. Composite analysis shows that a local anomalous high pressure favors widespread formation of the ssH sea fog. The subsidence in the high pressure intensifies the thermal and moist stratification between the MABL and free atmosphere through adiabatic warming. The dry air above helps cool the fog layer by enhancing the longwave radiative cooling at the fog top and the vertical mixing beneath, causing air temperature to drop below sea surface temperature. The ratio of sea fog with ssH to total sea fog decreases from spring to summer as the descending motion and MABL stratification both weaken. This study highlights the importance of longwave radiative cooling at the advection fog top and suggests a way to improve sea fog forecast in the Yellow Sea.

Liu, WT, Xie XS, Polito PS, Xie SP, Hashizume H.  2000.  Atmospheric manifestation of tropical instability wave observed by QuikSCAT and tropical rain measuring mission. Geophysical Research Letters. 27:2545-2548. Abstract
n/a
B
Xie, SP, Hafner J, Tanimoto Y, Liu WT, Tokinaga H, Xu HM.  2002.  Bathymetric effect on the winter sea surface temperature and climate of the Yellow and East China Seas. Geophysical Research Letters. 29   10.1029/2002gl015884   Abstract
n/a
C
Yang, Y, Xie SP, Wu LX, Kosaka Y, Li JP.  2017.  Causes of enhanced sst variability over the equatorial atlantic and its relationship to the Atlantic Zonal Mode in CMIP5. Journal of Climate. 30:6171-6182.   10.1175/jcli-d-16-0866.1   AbstractWebsite

A spurious band of enhanced sea surface temperature (SST) variance (SBEV) is identified over the northern equatorial Atlantic in the Geophysical Fluid Dynamics Laboratory (GFDL) Climate Model, version 2.1. The SBEV is especially pronounced in boreal spring owing to the combined effect of both anomalous atmospheric thermal forcing and oceanic vertical upwelling. The SBEV is a common bias in phase 5 of the Coupled Model Intercomparison Project (CMIP5), found in 14 out of 23 models. The SBEV in CMIP5 is associated with the atmospheric thermal forcing and the oceanic vertical upwelling, similar to GFDL CM2.1. While the tropical North Atlantic variability is only weakly correlated with the Atlantic zonal mode (AZM) in observations, the SBEV in CMIP5 produces conditions that drive and intensify the AZM variability via triggering the Bjerknes feedback. This partially explains why AZM is strong in some CMIP5 models even though the equatorial cold tongue and easterly trades are biased low.

Lin, L, Xu YY, Wang ZL, Diao CR, Dong WJ, Xie SP.  2018.  Changes in extreme rainfall over India and China attributed to regional aerosol-cloud interaction during the late 20th century rapid industrialization. Geophysical Research Letters. 45:7857-7865.   10.1029/2018gl078308   AbstractWebsite

Both mean and extreme rainfall decreased over India and Northern China during 1979-2005 at a rate of 0.2%/decade. The aerosol dampening effects on rainfall has also been suggested as a main driver of mean rainfall shift in India and China. Conflicting views, however, exist on whether aerosols enhance or suppress hazardous extreme heavy rainfall. Using Coupled Model Intercomparison Project phase 5 (CMIP5) multimodel ensemble, here we show that only a subset of models realistically reproduces the late-20th-century trend of extreme rainfall for the three major regions in Asia: drying in India and Northern China and wetting in Southern China, all consistent with mean rainfall change. As a common feature, this subset of models includes an explicit treatment of the complex physical processes of aerosol-cloud interaction (i.e., both cloud-albedo and cloud-lifetime effects), while simulation performance deteriorates in models that include only aerosol direct effect or cloud-albedo effect. The enhanced aerosol pollution during this rapid industrialization era is the leading cause of the spatially heterogeneous extreme rainfall change by dimming surface solar radiation, cooling adjacent ocean water, and weakening moisture transport into the continental region, while GHG warming or natural variability alone cannot explain the observed changes. Our results indicate that the projected intensification of regional extreme rainfall during the early-to-mid 21st-century, in response to the anticipated aerosol reduction, may be underestimated in global climate models without detailed treatment of complex aerosol-cloud interaction. Plain Language Summary Over Asia, a robust pattern of drying-wetting-drying trend over three most populated regions (India, South China, and North China, respectively) have been observed in the past few decades. Yet the cause of the 30-year trend is rather unclear, with conflicting arguments on the importance of natural variability, the greenhouse gas, land cover, and aerosols. Most of the previous studies, however, fail to provide a holistic explanation for all three major regions simultaneously. The aerosol-cloud interaction-induced oceanic cooling, as we show here, provides a critical piece in reproducing the past trend. Only a fraction of climate models with complex treatment of aerosol-cloud interaction capture the observed pattern; thus, unconstrained model data set provides biased outlook of extreme rainfall in this region.

Zhang, RS, Xie SP, Xu LX, Liu QY.  2016.  Changes in mixed layer depth and spring bloom in the Kuroshio extension under global warming. Advances in Atmospheric Sciences. 33:452-461.   10.1007/s00376-015-5113-8   AbstractWebsite

The mixed layer is deep in January-April in the Kuroshio Extension region. This paper investigates the response in this region of mixed layer depth (MLD) and the spring bloom initiation to global warming using the output of 15 models from CMIP5. The models indicate that in the late 21st century the mixed layer will shoal, and the MLD reduction will be most pronounced in spring at about 33A degrees N on the southern edge of the present deep-MLD region. The advection of temperature change in the upper 100 m by the mean eastward flow explains the spatial pattern of MLD shoaling in the models. Associated with the shoaling mixed layer, the onset of spring bloom inception is projected to advance due to the strengthened stratification in the warming climate.

Lintner, BR, Langenbrunner B, Neelin JD, Anderson BT, Niznik MJ, Li G, Xie SP.  2016.  Characterizing CMIP5 model spread in simulated rainfall in the Pacific Intertropical Convergence and South Pacific Convergence Zones. Journal of Geophysical Research-Atmospheres. 121:11590-11607.   10.1002/2016jd025284   AbstractWebsite

Current-generation climate models exhibit various errors or biases in both the spatial distribution and intensity of precipitation relative to observations. In this study, empirical orthogonal function analysis is applied to the space-model index domain of precipitation over the Pacific from Coupled Model Intercomparison Project Phase 5 (CMIP5) simulations to explore systematic spread of simulated precipitation characteristics across the ensemble. Two significant modes of spread, generically termed principal uncertainty patterns (PUPs), are identified in the December-January-February precipitation climatology: the leading PUP is associated with the meridional width of deep convection, while the second is associated with tradeoffs in precipitation intensity along the South Pacific Convergence Zone, the Intertropical Convergence Zone (ITCZ), and the spurious Southern Hemisphere ITCZ. An important factor distinguishing PUPs from the analogy to time series analysis is that the modes can reflect either true systematic intermodel variance patterns or internal variability. In order to establish that the PUPS reflect the former, three complementary tests are performed by using preindustrial control simulations: a bootstrap significance test for reproducibility of the intermodel spatial patterns, a check for robustness over very long climatological averages, and a test on the loadings of these patterns relative to interdecadal sampling. Composite analysis based on these PUPs demonstrates physically plausible relationships to CMIP5 ensemble spread in simulated sea surface temperatures (SSTs), circulation, and moisture. Further analysis of atmosphere-only, prescribed SST simulations demonstrates decreased spread in the spatial distribution of precipitation, while substantial spread in intensity remains. Key Points Systematic spread in CMIP5 simulation of Pacific region rainfall is investigated by using empirical mode reduction techniques Two significant modes of model spread are identified for the DJF rainfall climatology These modes are interpreted in terms of spread in simulated patterns of SST and circulation

Li, G, Xie SP, Du Y.  2015.  Climate model errors over the South Indian Ocean thermocline dome and their effect on the basin mode of interannual variability. Journal of Climate. 28:3093-3098.   10.1175/jcli-d-14-00810.1   AbstractWebsite

An open-ocean thermocline dome south of the equator is a striking feature of the Indian Ocean (IO) as a result of equatorial westerly winds. Over the thermocline dome, the El Nino-forced Rossby waves help sustain the IO basin (IOB) mode and offer climate predictability for the IO and surrounding countries. This study shows that a common equatorial easterly wind bias, by forcing a westward-propagating downwelling Rossby wave in the southern IO, induces too deep a thermocline dome over the southwestern IO (SWIO) in state-of-the-art climate models. Such a deep SWIO thermocline weakens the influence of subsurface variability on sea surface temperature (SST), reducing the IOB amplitude and possibly limiting the models' skill of regional climate prediction. To the extent that the equatorial easterly wind bias originates from errors of the South Asian summer monsoon, improving the monsoon simulation can lead to substantial improvements in simulating and predicting interannual variability in the IO.

Liu, C, Xie SP, Li PL, Xu LX, Gao WD.  2017.  Climatology and decadal variations in multicore structure of the North Pacific subtropical mode water. Journal of Geophysical Research-Oceans. 122:7506-7520.   10.1002/2017jc013071   AbstractWebsite

The pycnostad of the North Pacific subtropical mode water (STMW) often displays multiple vertical minima in the potential vorticity profile. Argo profile data from 2004 to 2015 are used to investigate interannual to decadal variations of the multicore structure. Climatologically, about 24% pycostads of STMW have multicore structure, and most of them distribute in the region west of 150 degrees E. STMW cores are classified into three submodes-the cold, middle, and warm ones with potential temperatures of 16.0-17 degrees C, 17-18 degrees C, and 18-19.5 degrees C, respectively. The Kuroshio Extension (KE) varies between stable and unstable states. The unstable KE with large meanders increases the subsurface stratification and shoals the winter mixed layer east of 150 degrees E with warmer temperatures. There, the dominant STMW type varies from the cold single type in stable KE years (making up 72% of the profiles with STMW) to the middle single one (53%) in unstable years. The variation of the dominant STMW type in the region east of 150 degrees E subsequently affects the multicore structure of STMW west of 150 degrees E. In a broad region between 130 degrees E and 180 degrees E, profiles with STMW are fewer in unstable years but the proportion of multicore profiles increases among STMW profiles. This might be due to the split recirculation gyre with a chaotic KE.

Wang, H, Xie SP, Liu QY.  2016.  Comparison of climate response to anthropogenic aerosol versus greenhouse gas forcing: Distinct patterns. Journal of Climate. 29:5175-5188.   10.1175/jcli-d-16-0106.1   AbstractWebsite

Spatial patterns of climate response to changes in anthropogenic aerosols and well-mixed greenhouse gases ( GHGs) are investigated using climate model simulations for the twentieth century. The climate response shows both similarities and differences in spatial pattern between aerosol and GHG runs. Common climate response between aerosol and GHG runs tends to be symmetric about the equator. This work focuses on the distinctive patterns that are unique to the anthropogenic aerosol forcing. The tropospheric cooling induced by anthropogenic aerosols is locally enhanced in the midlatitude Northern Hemisphere with a deep vertical structure around 40 degrees N, anchoring a westerly acceleration in thermal wind balance. The aerosol-induced negative radiative forcing in the Northern Hemisphere requires a cross-equatorial Hadley circulation to compensate interhemispheric energy imbalance in the atmosphere. Associated with a southward shift of the intertropical convergence zone, this interhemispheric asymmetric mode is unique to aerosol forcing and absent in GHG runs. Comparison of key climate response pattern indices indicates that the aerosol forcing dominates the interhemispheric asymmetric climate response in historical all-forcing simulations, as well as regional precipitation change such as the drying trend over the East Asian monsoon region. While GHG forcing dominates global mean surface temperature change, its effect is on par with and often opposes the aerosol effect on precipitation, making it difficult to detect anthropogenic change in rainfall from historical observations.

Zinke, J, Rountrey A, Feng M, Xie SP, Dissard D, Rankenburg K, Lough JM, McCulloch MT.  2014.  Corals record long-term Leeuwin current variability including Ningaloo Nino/Nina since 1795. Nature Communications. 5   10.1038/ncomms4607   AbstractWebsite

Variability of the Leeuwin current (LC) off Western Australia is a footprint of interannual and decadal climate variations in the tropical Indo-Pacific. La Nina events often result in a strengthened LC, high coastal sea levels and unusually warm sea surface temperatures (SSTs), termed Ningaloo Nino. The rarity of such extreme events and the response of the southeastern Indian Ocean to regional and remote climate forcing are poorly understood owing to the lack of long-term records. Here we use well-replicated coral SST records from within the path of the LC, together with a reconstruction of the El Nino-Southern Oscillation to hindcast historical SST and LC strength from 1795 to 2010. We show that interannual and decadal variations in SST and LC strength characterized the past 215 years and that the most extreme sea level and SST anomalies occurred post 1980. These recent events were unprecedented in severity and are likely aided by accelerated global ocean warming and sea-level rise.

Annamalai, H, Murtugudde R, Potemra J, Xie SP, Liu P, Wang B.  2003.  Coupled dynamics over the Indian Ocean: spring initiation of the Zonal Mode. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 50:2305-2330.   10.1016/s0967-0645(03)00058-4   Abstract
n/a
D
Liu, W, Lu J, Leung LR, Xie SP, Liu ZY, Zhu J.  2015.  The de-correlation of westerly winds and westerly-wind stress over the Southern Ocean during the Last Glacial Maximum. Climate Dynamics. 45:3157-3168.   10.1007/s00382-015-2530-4   AbstractWebsite

Motivated by indications from paleo-evidence, this paper investigates the changes of the Southern Westerly Winds (SWW) and westerly-wind stress between the Last Glacial Maximum (LGM) and pre-industrial in the PMIP3/CMIP5 simulations, highlighting the role of Antarctic sea ice in modulating the wind effect on ocean. Particularly, a de-correlation occurs between the changes in SWW and westerly-wind stress, caused primarily by an equatorward expansion of winter Antarctic sea ice that undermines the efficacy of wind in generating stress over the liquid ocean. Such de-correlation may reflect the LGM condition in reality, in view of the fact that the model which simulates this condition has most fidelity in simulating modern SWW and Antarctic sea ice. Therein two models stand out for their agreements with paleo-evidence regarding the change of SWW and the westerly-wind stress. They simulate strengthened and poleward-migrated LGM SWW in the atmosphere, consistent with the indications from dust records. Whilst in the ocean, they well capture an equatorward-shifted pattern of the observed oceanic front shift, with most pronounced equatorward-shifted westerly wind stress during the LGM.

Xie, S-P, Du Y, Huang G, Zheng X-T, Tokinaga H, Hu K, Liu Q.  2010.  Decadal Shift in El Nino Influences on Indo-Western Pacific and East Asian Climate in the 1970s. Journal of Climate. 23:3352-3368.   10.1175/2010jcli3429.1   Abstract
n/a
Li, JB, Xie SP, Cook ER, Chen FH, Shi JF, Zhang DD, Fang KY, Gou XH, Li T, Peng JF, Shi SY, Zhao YS.  2019.  Deciphering human contributions to Yellow River flow reductions and downstream drying using centuries-long tree ring records. Geophysical Research Letters. 46:898-905.   10.1029/2018gl081090   AbstractWebsite

The Yellow River flow has decreased substantially in recent decades, and the river often dried up in the lower reach and failed to reach the sea. Climate change and human disruption have been suggested as major causes of the flow reduction, but quantification of their relative contribution is challenging due to limited instrumental records and disturbance by dams. Here we use a basin-wide tree ring network to reconstruct the Yellow River flow for the past 1,200 years and show that the flow exhibits marked amplitude variations that are closely coupled to the hydrological mean state swings at multidecadal to centennial timescales. Recent flow should have increased to the highest level of the past 1,200 years if there were no human disruption. However, human activities have caused a loss of nearly half of natural flow since the late 1960s and are the main culprit for recent downstream flow reduction. Plain Language Summary Recent Yellow River flow reductions have had major impacts on China's economy and water policy. The short and heavily human-modified gauge records are unable to reveal natural flow variability now and in the past. Here we use tree rings to reconstruct long-term Yellow River flow, which enables an assessment of natural flow variability and the detection of human contributions to recent flow reductions. Our 1,200-year reconstruction reveals that under natural conditions the Yellow River flow should have increased markedly since the early twentieth century. However, the observed flow decreased since the late 1960s and such a decrease must be predominately caused by human interventions instead of climate change.

Wang, H, Xie SP, Tokinaga H, Liu Q, Kosaka Y.  2016.  Detecting cross-equatorial wind change as a fingerprint of climate response to anthropogenic aerosol forcing. Geophysical Research Letters. 43:3444-3450.   10.1002/2016gl068521   AbstractWebsite

Anthropogenic aerosols are amajor driver of the twetieth century climate change. In climate models, the aerosol forcing, larger in the Northern than Southern Hemispheres, induces an interhemispheric Hadley circulation. In support of the model result, we detected a robust change in the zonal mean cross-equatorial wind over the past 60 years from ship observations and reanalyses, accompanied by physically consistent changes in atmospheric pressure and marine cloud cover. Single-forcing experiments indicate that the observed change in cross-equatorial wind is a fingerprint of aerosol forcing. This zonal mean mode follows the evolution of global aerosol forcing that is distinct from regional changes in the Atlantic sector. Atmospheric simulations successfully reproduce this interhemispheric mode, indicating the importance of sea surface temperature mediation in response to anthropogenic aerosol forcing. As societies awaken to reduce aerosol emissions, a phase reversal of this interhemispheric mode is expected in the 21st century.

Shu, W, Lixin W, Qinyu L, Xie S-P.  2010.  Development processes of the Tropical Pacific Meridional Mode. Advances in Atmospheric Sciences. 27:95-99.   10.1007/s00376-009-8067-x   Abstract
n/a
Hashizume, H, Xie SP, Fujiwara M, Shiotani M, Watanabe T, Tanimoto Y, Liu WT, Takeuchi K.  2002.  Direct observations of atmospheric boundary layer response to SST variations associated with tropical instability waves over the eastern equatorial Pacific. Journal of Climate. 15:3379-3393. Abstract
n/a
Wang, H, Xie SP, Kosaka Y, Liu QY, Du Y.  2019.  Dynamics of Asian summer monsoon response to anthropogenic aerosol forcing. Journal of Climate. 32:843-858.   10.1175/jcli-d-18-0386.1   AbstractWebsite

Anthropogenic aerosols partially mask the greenhouse warming and cause the reduction in Asian summer monsoon precipitation and circulation. By decomposing the atmospheric change into the direct atmospheric response to radiative forcing and sea surface temperature (SST)-mediated change, the physical mechanisms for anthropogenic-aerosol-induced changes in the East Asian summer monsoon (EASM) and South Asian summer monsoon (SASM) are diagnosed. Using coupled and atmospheric general circulation models, this study shows that the aerosol-induced troposphere cooling over Asian land regions generates anomalous sinking motion between 20 degrees and 40 degrees N and weakens the EASM north of 20 degrees N without SST change. The decreased EASM precipitation and the attendant wind changes are largely due to this direct atmospheric response to radiative forcing, although the aerosol-induced North Pacific SST cooling also contributes. The SST-mediated change dominates the aerosol-induced SASM response, with contributions from both the north-south interhemispheric SST gradient and the local SST cooling pattern over the tropical Indian Ocean. Specifically, with large meridional gradient, the zonal-mean SST cooling pattern is most important for the Asian summer monsoon response to anthropogenic aerosol forcing, resulting in a reorganization of the regional meridional atmospheric overturning circulation. While uncertainty in aerosol radiative forcing has been emphasized in the literature, our results show that the intermodel spread is as large in the SST effect on summer monsoon rainfall, calling for more research into the ocean-atmosphere coupling.

E
Chang, CH, Xie SP, Schneider N, Qiu B, Small J, Zhuang W, Taguchi B, Sasaki H, Lin XP.  2012.  East Pacific ocean eddies and their relationship to subseasonal variability in Central American wind jets. Journal of Geophysical Research-Oceans. 117   10.1029/2011jc007315   Abstract

Subseasonal variability in sea surface height (SSH) over the East Pacific warm pool off Central America is investigated using satellite observations and an eddy-resolving ocean general circulation model. SSH variability is organized into two southwest-tilted bands on the northwest flank of the Tehuantepec and Papagayo wind jets and collocated with the thermocline troughs. Eddy-like features of wavelength similar to 600 km propagate southwestward along the high-variance bands at a speed of 9-13 cm/s. Wind fluctuations are important for eddy formation in the Gulf of Tehuantepec, with a recurring interval of 40-90 days. When forced by satellite wind observations, the model reproduces the two high-variance bands and the phase propagation of the Tehuantepec eddies. Our observational analysis and model simulation suggest the following evolution of the Tehuantepec eddies. On the subseasonal timescale, in response to the gap wind intensification, a coastal anticyclonic eddy forms on the northwest flank of the wind jet and strengthens as it propagates offshore in the following two to three weeks. An energetics analysis based on the model simulation indicates that besides wind work, barotropic and baroclinic instabilities of the mean flow are important for the eddy growth. Both observational and model results suggest a re-intensification of the anticyclonic eddy in response to the subsequent wind jet event. Off Papagayo, ocean eddy formation is not well correlated with local wind jet variability. In both the Gulfs of Tehuantepec and Papagayo, subseasonal SSH variability is preferentially excited on the northwest flank of the wind jet. Factors for this asymmetry about the wind jet axis as well as the origins of wind jet variability are discussed.

Timmermann, A, Lorenz SJ, An SI, Clement A, Xie SP.  2007.  The effect of orbital forcing on the mean climate and variability of the tropical Pacific. Journal of Climate. 20:4147-4159.   10.1175/jcli4240.1   Abstract
n/a