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Kubota, H, Kosaka Y, Xie SP.  2016.  A 117-year long index of the Pacific-Japan pattern with application to interdecadal variability. International Journal of Climatology. 36:1575-1589.   10.1002/joc.4441   AbstractWebsite

The Pacific-Japan (PJ) pattern affects interannual variability in the East Asian and western North Pacific (WNP) summer monsoons. This teleconnection pattern is characterized by a meridional dipole of anomalous circulation and precipitation between the tropical WNP and the midlatitudes. This study develops a long index of the PJ pattern using station-based atmospheric pressure data to track the PJ variability from 1897 to 2013. This index is correlated with a wide array of climate variables including air temperature, precipitation, Yangtze River flow, Japanese rice yield and the occurrence of tropical cyclones over the WNP (especially those that make landfall on the Chinese and Korean coast). For the recent three decades, the PJ index reproduces well-known correlations with El Nino-Southern Oscillation (ENSO) in the preceding boreal winter and Indian Ocean temperature in the concurrent summer. For the 117-year period, this ENSO-PJ relationship varies on interdecadal time scales, with low correlations in the 1920s and from the 1940s to 1970s, and recurrences of significant correlations at the beginning of the 20th century and the 1930s. In accordance with the modulation, the magnitude and regional climate effect of the PJ variability have changed. These results highlight the importance of interdecadal modulations of climate anomalies in the summer WNP and the need of long-term observations to study such modulations.

Xie, SP, Saiki N.  1999.  Abrupt onset and slow seasonal evolution of summer monsoon in an idealized GCM simulation. Journal of the Meteorological Society of Japan. 77:949-968. Abstract
Xie, SP.  2013.  Advancing climate dynamics toward reliable regional climate projections. Journal of Ocean University of China. 12:191-200.   10.1007/s11802-013-2277-7   AbstractWebsite

With a scientific consensus reached regarding the anthropogenic effect on global mean temperature, developing reliable regional climate projections has emerged as a new challenge for climate science. A national project was launched in China in 2012 to study ocean's role in regional climate change. This paper starts with a review of recent advances in the study of regional climate response to global warming, followed by a description of the Chinese project including the rationale, objectives, and plan for field observations. The 15 research articles that follow in the special issue are highlighted, representing some of the initial results from the project.

Xie, SP, Xu HM, Kessler WS, Nonaka M.  2005.  Air-sea interaction over the eastern Pacific warm pool: Gap winds, thermocline dome, and atmospheric convection. Journal of Climate. 18:5-20. Abstract
Fu, G, Guo JT, Xie SP, Duane YH, Zhang MG.  2006.  Analysis and high-resolution modeling of a dense sea fog event over the Yellow Sea. Atmospheric Research. 81:293-303.   10.1016/j.atmosres.2006.01.005   Abstract
Kilpatrick, TJ, Xie S-P.  2015.  ASCAT observations of downdrafts from mesoscale convective systems. Geophysical Research Letters.   10.1002/2015GL063025   AbstractWebsite

Downdrafts of air cooled by evaporating raindrops are an essential component of mesoscale convective systems (MCSs). Here we use surface wind observations from the Advanced SCATterometer (ASCAT) to identify MCS downdrafts over the western equatorial Pacific Ocean as regions of horizontal wind divergence exceeding 10-4 s-1. More than 1300 downdrafts are identified over the observation period (2009–2014). The downdraft signal in the surface winds is validated with satellite measurements of brightness temperature and rainfall rate, and surface buoy measurements of air temperature; composite analysis with these measurements indicates ASCAT detects downdrafts that lag the peak convection by 8–12 h. While ASCAT resolves mesoscale downdrafts in regions of light rain, a composite against buoy air temperature indicates that ASCAT fails to resolve the stronger convective-scale downdrafts associated with heavy rainfall at squall fronts. Nevertheless, the global observations by the satellite scatterometer open a new avenue for studying MCSs.

Oouchi, K, Noda AT, Satoh M, Wang B, Xie SP, Takahashi HG, Yasunari T.  2009.  Asian summer monsoon simulated by a global cloud-system-resolving model: Diurnal to intra-seasonal variability. Geophysical Research Letters. 36   10.1029/2009gl038271   Abstract
Hu, KM, Huang G, Xie SP.  2019.  Assessing the internal variability in multi-decadal trends of summer surface air temperature over East Asia with a large ensemble of GCM simulations. Climate Dynamics. 52:6229-6242.   10.1007/s00382-018-4503-x   AbstractWebsite

This study investigates the impact of internal variability on East Asian summer (June-July-August) surface air temperature (SAT) trends on the multidecadal time scale based on a 30-member ensemble of simulations that share the same external forcing from 1970 to 2005. The ensemble-mean SAT in East Asia shows a positive trend, but the patterns and the magnitudes in the individual members are remarkably diverse, highlighting the strong effect of internal variability. The first two leading empirical orthogonal function (EOF) modes of the SAT trends among ensemble members are used to represent the leading patterns of internally generated SAT change in East Asia. The first EOF mode displays a south-north dipole structure, associated with a zonally banded circulation pattern over East Asia and the North Pacific. The second mode represents coherent trend in North China, Korea and Japan, accompanied by the Northern Hemisphere annular mode (NAM)-like circulation changes. A dynamical adjustment method is applied to reduce circulation-induced internal variability in SAT, and the adjusted SAT trends are much less variable among ensemble members and more in line with the ensemble mean than the raw trends. Observed evidences show that the summertime SAT in most of East Asia, especially in northern East Asia, has experienced rapid warming in recent decades. After dynamical adjustment, the residual trends of SAT in observations are weaker than the raw trends, especially at high and middle latitudes, suggesting the enhanced warming in northern East Asia over the recent decades was not entirely anthropogenic but partly caused by internal variability.

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.

Xu, H, Tokinaga H, Xie S-P.  2010.  Atmospheric Effects of the Kuroshio Large Meander during 2004-05. Journal of Climate. 23:4704-4715.   10.1175/2010jcli3267.1   Abstract
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
Minobe, S, Miyashita M, Kuwano-Yoshida A, Tokinaga H, Xie S-P.  2010.  Atmospheric Response to the Gulf Stream: Seasonal Variations. Journal of Climate. 23:3699-3719.   10.1175/2010jcli3359.1   Abstract
Inatsu, M, Mukougawa H, Xie SP.  2003.  Atmospheric response to Zonal variations in midlatitude SST: Transient and stationary eddies and their feedback. Journal of Climate. 16:3314-3329. Abstract
Kamae, Y, Mei W, Xie SP, Naoi M, Ueda H.  2017.  Atmospheric Rivers over the Northwestern Pacific: Climatology and Interannual Variability. Journal of Climate. 30:5605-5619.   10.1175/jcli-d-16-0875.1   AbstractWebsite

Atmospheric rivers (ARs), conduits of intense water vapor transport in the midlatitudes, are critically important for water resources and heavy rainfall events over the west coast of North America, Europe, and Africa. ARs are also frequently observed over the northwestern Pacific (NWP) during boreal summer but have not been studied comprehensively. Here the climatology, seasonal variation, interannual variability, and predictability of NWPARs (NWPARs) are examined by using a large ensemble, high-resolution atmospheric general circulation model (AGCM) simulation and a global atmospheric reanalysis. The AGCM captures general characteristics of climatology and variability compared to the reanalysis, suggesting a strong sea surface temperature (SST) effect on NWPARs. The summertime NWPAR occurrences are tightly related to El Ni (n) over tildeo-Southern Oscillation (ENSO) in the preceding winter through Indo-western Pacific Ocean capacitor (IPOC) effects. An enhanced East Asian summer monsoon and a low-level anticyclonic anomaly over the tropical western North Pacific in the post-El Ni (n) over tildeo summer reinforce low-level water vapor transport from the tropics with increased occurrence of NWPARs. The strong coupling with ENSO and IPOC indicates a high predictability of anomalous summertime NWPAR activity.

Tokinaga, H, Tanimoto Y, Nonaka M, Taguchi B, Fukamachi T, Xie SP, Nakamura H, Watanabe T, Yasuda I.  2006.  Atmospheric sounding over the winter Kuroshio Extension: Effect of surface stability on atmospheric boundary layer structure. Geophysical Research Letters. 33   10.1029/2005gl025102   Abstract
Kuwano-Yoshida, A, Taguchi B, Xie SP.  2014.  Baiu rainband termination in atmospheric and coupled atmosphere-ocean models. Journal of Climate. 26:10111-10124.   10.1175/jcli-d-13-00231.1   AbstractWebsite

The baiu rainband is a summer rainband stretching from eastern China through Japan toward the northwestern Pacific. The climatological termination of the baiu rainband is investigated using the Japanese 25-yr Reanalysis (JRA-25), a stand-alone atmospheric general circulation model (GCM) forced with observed sea surface temperature (SST) and an atmosphere-ocean GCM (AOGCM). The baiu rainband over the North Pacific abruptly shifts northward and weakens substantially in early July in the atmospheric GCM (AGCM), too early compared to observations (late July). The midtroposphere westerly jet and its thermal advection explain this meridional shift of the baiu rainband, but the ocean surface evaporation modulates the precipitation intensity. In AGCM, deep convection in the subtropical northwestern Pacific sets in prematurely, displacing the westerly jet northward over the cold ocean surface earlier than in observations. The suppressed surface evaporation over the cold ocean suppresses precipitation even though the midtropospheric warm advection and vertically integrated moisture convergence are similar to those before the westerly jet's northward shift. As a result, the baiu rainband abruptly weakens after the northward shift in JRA-25 and AGCM. In AOGCM, cold SST biases in the subtropics inhibit deep convection, delaying the poleward excursion of the westerly jet. As a result, the upward motion induced by both the strong westerly jet and the rainband persist over the northwestern Pacific through summer in the AOGCM. The results indicate that the westerly jet and the ocean evaporation underneath are important for the baiu rainband, the latter suggesting an oceanic effect on this important phenomenon.

Cronin, MF, Xie SP, Hashizume H.  2003.  Barometric pressure variations associated with Eastern Pacific tropical instability waves. Journal of Climate. 16:3050-3057. Abstract
Zeng, LL, Du Y, Xie SP, Wang DX.  2009.  Barrier layer in the South China Sea during summer 2000. Dynamics of Atmospheres and Oceans. 47:38-54.   10.1016/j.dynatmoce.2008.08.001   Abstract
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
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.

Xie, SP, Seki M.  1997.  Causes of equatorial asymmetry in sea surface temperature over the eastern Pacific. Geophysical Research Letters. 24:2581-2584. Abstract
Collins, M, Minobe S, Barreiro M, Bordoni S, Kaspi Y, Kuwano-Yoshida A, Keenlyside N, Manzini E, O'Reilly CH, Sutton R, Xie SP, Zolina O.  2018.  Challenges and opportunities for improved understanding of regional climate dynamics. Nature Climate Change. 8:101-108.   10.1038/s41558-017-0059-8   AbstractWebsite

Dynamical processes in the atmosphere and ocean are central to determining the large-scale drivers of regional climate change, yet their predictive understanding is poor. Here, we identify three frontline challenges in climate dynamics where significant progress can be made to inform adaptation: response of storms, blocks and jet streams to external forcing; basin-to-basin and tropical-extratropical teleconnections; and the development of non-linear predictive theory. We highlight opportunities and techniques for making immediate progress in these areas, which critically involve the development of high-resolution coupled model simulations, partial coupling or pacemaker experiments, as well as the development and use of dynamical metrics and exploitation of hierarchies of models.