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Journal Article
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
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
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
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.

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
Tomita, H, Xie SP, Tokinaga H, Kawai Y.  2013.  Cloud response to the meandering Kuroshio extension front. Journal of Climate. 26:9393-9398.   10.1175/jcli-d-13-00133.1   AbstractWebsite

A unique set of observations on board research vessel (R/V) Mirai in April 2010 captured a striking cloud hole over a cold meander of the Kuroshio Extension (KE) east of Japan as corroborated by atmospheric soundings, ceilometer, shipboard radiation data, and satellite cloud images. Distinct differences were also observed between the warm meander farther to the north and warm water south of the KE. The atmosphere is highly unstable over the warm meander, promoting a well-mixed marine atmospheric boundary layer (MABL) and a layer of solid stratocumulus clouds capped by a strong inversion. Over the warm water south of the KE, MABL deepens and is decoupled from the ocean surface. Scattered cumulus clouds develop as captured by rapid variations in ceilometer-derived cloud base. The results show that the meandering KE front affects the entire MABL and the clouds. Such atmospheric response can potentially intensify the baroclinicity in the lower atmosphere.

Xie, SP, Ishiwatari M, Hashizume H, Takeuchi K.  1998.  Coupled ocean-atmospheric waves on the equatorial front. Geophysical Research Letters. 25:3863-3866. Abstract
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
Taguchi, B, Qiu B, Nonaka M, Sasaki H, Xie S-P, Schneider N.  2010.  Decadal variability of the Kuroshio Extension: mesoscale eddies and recirculations. Ocean Dynamics. 60:673-691.   10.1007/s10236-010-0295-1   Abstract
Taguchi, B, Xie SP, Schneider N, Nonaka M, Sasaki H, Sasai Y.  2007.  Decadal variability of the Kuroshio Extension: Observations and an eddy-resolving model hindcast. Journal of Climate. 20:2357-2377.   10.1175/jcli4142.1   Abstract
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.

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
Tokinaga, H, Xie SP, Mukougawa H.  2017.  Early 20th-century Arctic warming intensified by Pacific and Atlantic multidecadal variability. Proceedings of the National Academy of Sciences of the United States of America. 114:6227-6232.   10.1073/pnas.1615880114   AbstractWebsite

With amplified warming and record sea ice loss, the Arctic is the canary of global warming. The historical Arctic warming is poorly understood, limiting our confidence in model projections. Specifically, Arctic surface air temperature increased rapidly over the early 20th century, at rates comparable to those of recent decades despite much weaker greenhouse gas forcing. Here, we show that the concurrent phase shift of Pacific and Atlantic interdecadal variability modes is the major driver for the rapid early 20th-century Arctic warming. Atmospheric model simulations successfully reproduce the early Arctic warming when the interdecadal variability of sea surface temperature (SST) is properly prescribed. The early 20th-century Arctic warming is associated with positive SST anomalies over the tropical and North Atlantic and a Pacific SST pattern reminiscent of the positive phase of the Pacific decadal oscillation. Atmospheric circulation changes are important for the early 20th-century Arctic warming. The equatorial Pacific warming deepens the Aleutian low, advecting warm air into the North American Arctic. The extratropical North Atlantic and North Pacific SST warming strengthens surface westerly winds over northern Eurasia, intensifying the warming there. Coupled ocean-atmosphere simulations support the constructive intensification of Arctic warming by a concurrent, negative-to-positive phase shift of the Pacific and Atlantic interdecadal modes. Our results aid attributing the historical Arctic warming and thereby constrain the amplified warming projected for this important region.

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.

Hosoda, S, Xie SP, Takeuchi K, Nonaka M.  2001.  Eastern North Pacific Subtropical Mode Water in a general circulation model: Formation mechanism and salinity effects. Journal of Geophysical Research-Oceans. 106:19671-19681. Abstract
Xie, SP, Peng QH, Kamae Y, Zheng XT, Tokinaga H, Wang DX.  2018.  Eastern Pacific ITCZ Dipole and ENSO Diversity. Journal of Climate. 31:4449-4462.   10.1175/jcli-d-17-0905.1   AbstractWebsite

The eastern tropical Pacific features strong climatic asymmetry across the equator, with the intertropical convergence zone (ITCZ) displaced north of the equator most of time. In February- April (FMA), the seasonal warming in the Southern Hemisphere and cooling in the Northern Hemisphere weaken the climatic asymmetry, and a double ITCZ appears with a zonal rainband on either side of the equator. Results from an analysis of precipitation variability reveal that the relative strength between the northern and southern ITCZ varies from one year to another and this meridional seesaw results from ocean-atmosphere coupling. Surprisingly this meridional seesaw is triggered by an El Nino-Southern Oscillation (ENSO) of moderate amplitudes. Although ENSO is originally symmetric about the equator, the asymmetry in the mean climate in the preceding season introduces asymmetric perturbations, which are then preferentially amplified by coupled ocean-atmosphere feedback in FMA when deep convection is sensitive to small changes in cross-equatorial gradient of sea surface temperature. This study shows that moderate ENSO follows a distinct decay trajectory in FMA and southeasterly cross-equatorial wind anomalies cause moderate El Nino to dissipate rapidly as southeasterly cross-equatorial wind anomalies intensify ocean upwelling south of the equator. In contrast, extreme El Nino remains strong through FMA as enhanced deep convection causes westerly wind anomalies to intrude and suppress ocean upwelling in the eastern equatorial Pacific.

Pahnke, K, Sachs JP, Keigwin L, Timmermann A, Xie SP.  2007.  Eastern tropical Pacific hydrologic changes during the past 27,000 years from D/H ratios in alkenones. Paleoceanography. 22   10.1029/2007pa001468   Abstract
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
Tomita, T, Xie SP, Nonaka M.  2002.  Estimates of surface and subsurface forcing for decadal sea surface temperature variability in the mid-latitude North Pacific. Journal of the Meteorological Society of Japan. 80:1289-1300. Abstract
Shi, JR, Xie SP, Talley LD.  2018.  Evolving relative importance of the Southern Ocean and North Atlantic in anthropogenic ocean heat uptake. Journal of Climate. 31:7459-7479.   10.1175/jcli-d-18-0170.1   AbstractWebsite

Ocean uptake of anthropogenic heat over the past 15 years has mostly occurred in the Southern Ocean, based on Argo float observations. This agrees with historical simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5), where the Southern Ocean (south of 30 degrees S) accounts for 72% +/- 28% of global heat uptake, while the contribution from the North Atlantic north of 30 degrees N is only 6%. Aerosols preferentially cool the Northern Hemisphere, and the effect on surface heat flux over the subpolar North Atlantic opposes the greenhouse gas (GHG) effect in nearly equal magnitude. This heat uptake compensation is associated with weakening (strengthening) of the Atlantic meridional overturning circulation (AMOC) in response to GHG (aerosol) radiative forcing. Aerosols are projected to decline in the near future, reinforcing the greenhouse effect on the North Atlantic heat uptake. As a result, the Southern Ocean, which will continue to take up anthropogenic heat largely through the mean upwelling of water from depth, will be joined by increased relative contribution from the North Atlantic because of substantial AMOC slowdown in the twenty-first century. In the RCP8.5 scenario, the percentage contribution to global uptake is projected to decrease to 48% +/- 8% in the Southern Ocean and increase to 26% +/- 6% in the northern North Atlantic. Despite the large uncertainty in the magnitude of projected aerosol forcing, our results suggest that anthropogenic aerosols, given their geographic distributions and temporal trajectories, strongly influence the high-latitude ocean heat uptake and interhemispheric asymmetry through AMOC change.

Xie, SP, Nonaka M, Tanimoto Y, Tokinaga H, Xu HM, Kessler WS, Small RJ, Liu WT, Hafner J.  2004.  A fine view from space. Bulletin of the American Meteorological Society. 85:1060-1062. Abstract
Kamae, Y, Shiogama H, Imada Y, Mori M, Arakawa O, Mizuta R, Yoshida K, Takahashi C, Arai M, Ishii M, Watanabe M, Kimoto M, Xie SP, Ueda H.  2017.  Forced response and internal variability of summer climate over western North America. Climate Dynamics. 49:403-417.   10.1007/s00382-016-3350-x   AbstractWebsite

Over the past decade, anomalously hot summers and persistent droughts frequented over the western United States (wUS), the condition similar to the 1950s and 1960s. While atmospheric internal variability is important for mid-latitude interannual climate variability, it has been suggested that anthropogenic external forcing and multidecadal modes of variability in sea surface temperature, namely, the Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO), also affect the occurrence of droughts and hot summers. In this study, 100-member ensemble simulations for 1951-2010 by an atmospheric general circulation model were used to explore relative contributions of anthropogenic warming, atmospheric internal variability, and atmospheric response to PDO and AMO to the decadal anomalies over the wUS. By comparing historical and sensitivity simulations driven by observed sea surface temperature, sea ice, historical forcing agents, and non-warming counterfactual climate forcing, we found that large portions of recent increases in mean temperature and frequency of hot summers (66 and 82 %) over the wUS can be attributed to the anthropogenic global warming. In contrast, multidecadal change in the wUS precipitation is explained by a combination of the negative PDO and the positive AMO after the 2000s. Diagnostics using a linear baroclinic model indicate that AMO- and PDO-related diabatic heating anomalies over the tropics contribute to the anomalous atmospheric circulation associated with the droughts and hot summers over wUS on multidecadal timescale. Those anomalies are not robust during the periods when PDO and AMO are in phase. The prolonged PDO-AMO antiphase period since the late twentieth century resulted in the substantial component of multidecadal anomalies in temperature and precipitation over the wUS.

Yan, XH, Boyer T, Trenberth K, Karl TR, Xie SP, Nieves V, Tung KK, Roemmich D.  2016.  The global warming hiatus: Slowdown or redistribution? Earths Future. 4:472-482.   10.1002/2016ef000417   AbstractWebsite

Global mean surface temperatures (GMST) exhibited a smaller rate of warming during 1998-2013, compared to the warming in the latter half of the 20th Century. Although, not a "true" hiatus in the strict definition of the word, this has been termed the "global warming hiatus" by IPCC (2013). There have been other periods that have also been defined as the "hiatus" depending on the analysis. There are a number of uncertainties and knowledge gaps regarding the "hiatus." This report reviews these issues and also posits insights from a collective set of diverse information that helps us understand what we do and do not know. One salient insight is that the GMST phenomenon is a surface characteristic that does not represent a slowdown in warming of the climate system but rather is an energy redistribution within the oceans. Improved understanding of the ocean distribution and redistribution of heat will help better monitor Earth's energy budget and its consequences. A review of recent scientific publications on the "hiatus" shows the difficulty and complexities in pinpointing the oceanic sink of the "missing heat" from the atmosphere and the upper layer of the oceans, which defines the "hiatus." Advances in "hiatus" research and outlooks (recommendations) are given in this report.

Xie, S-P, Deser C, Vecchi GA, Ma J, Teng H, Wittenberg AT.  2010.  Global Warming Pattern Formation: Sea Surface Temperature and Rainfall. Journal of Climate. 23:966-986.   10.1175/2009jcli3329.1   Abstract