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The Unprecedented Extreme Anticyclonic Anomaly over Northeast Asia in July 2021 and Its Climatic Impacts

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Advances in Atmospheric Sciences 2024年第4期41卷 608-618页

作者： Xingyan ZHOU Riyu LU Laboratory for Climate Studies National Climate CenterChina Meteorological AdministrationBeijing 100081China State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China

This study investigates the evolution of an extreme anomalous anticyclone(AA)event over Northeast Asia,which was one of the dominant circulation systems responsible for the catastrophic extreme precipitation event in July 2021 in Henan,and further explores the significant impact of this AA on surface temperatures beneath it.The results indicate that this AA event over Northeast Asia was unprecedented in terms of intensity and duration.The AA was very persistent and extremely strong for 10 consecutive days from 13 to 22 July 2021.This long-lived and unprecedented AA led to the persistence of warmer surface temperatures beyond the temporal span of the pronounced 500-hPa anticyclonic signature as the surface air temperatures over land in Northeast Asia remained extremely warm through 29 July 2021.Moreover,the sea surface temperatures in the Sea of Japan/East Sea were extremely high for 30 consecutive days from 13 July to 11 August 2021,persisting well after the weakening or departure of this AA.These results emphasize the extreme nature of this AA over Northeast Asia in July 2021 and its role in multiple extreme climate events,even over remote regions.Furthermore,possible reasons for this long-lasting AA are explored,and it is suggested to be a byproduct of a teleconnection pattern over extratropical Eurasia during the first half of its life cycle,and of the Pacific-Japan teleconnection pattern during the latter half.

关键词： anomalous anticyclone Northeast Asia surface air temperatures sea surface temperatures

Tropical Cyclones over the Western North Pacific Strengthen the East Asia–Pacific Pattern during Summer

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Advances in Atmospheric Sciences 2022年第2期39卷 249-259页

作者： Sining LING Riyu LU State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China

The contribution of tropical cyclones(TCs)to the East Asia–Pacific(EAP)teleconnection pattern during summer was investigated using the best track data of the Joint Typhoon Warning Center and NCEP-2 reanalysis datasets from 1979 to2018.The results showed that the TCs over the western North Pacific(WNP)correspond to a strengthened EAP pattern:During the summers of strong convection over the tropical WNP,TC days correspond to a stronger cyclonic circulation anomaly over the WNP in the lower troposphere,an enhanced seesaw pattern of negative and positive geopotential height anomalies over the subtropical WNP and midlatitude East Asia in the middle troposphere,and a more northward shift of the East Asian westerly jet in the upper troposphere.Further analyses indicated that two types of TCs with distinctly different tracks,i.e.,westward-moving TCs and northward-moving TCs,both favor the EAP pattern.The present results imply that TCs over the WNP,as extreme weather,can contribute significantly to summer-mean climate anomalies over the WNP and East Asia.

关键词： tropical cyclone East Asia–Pacific pattern teleconnection western North Pacific summer

Different Impacts of Intraseasonal Oscillations on Precipitation in Southeast China between Early and Late Summers

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Advances in Atmospheric Sciences 2022年第11期39卷 1885-1896页

作者： Junqi LIU Riyu LU State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100029China

This study investigates the influences of boreal summer intraseasonal oscillation(BSISO), which originates from the equatorial Indian Ocean and prevails over the Indo-Pacific region, on precipitation over Southeast China, including South China and Yangtze River Valley. The results indicate that the BSISO-related precipitation anomalies are remarkably different between early summer(May–June) and late summer(July–August). The BSISO-related precipitation anomalies tend to appear more northward in late summer in comparison with early summer. Accordingly, the BSISO is significantly related to precipitation anomalies over South China during many phases in early summer but related to very weak anomalies during all the phases in late summer. Such northward shifts of precipitation anomalies from early summer to late summer are clearest during phases 4 and 7, when the lower-tropospheric anticyclonic and cyclonic circulation anomalies dominate over the subtropical western North Pacific, respectively. Finally, we explain the differences between early and late summers through the seasonal northward migration of climatological equivalent potential temperature gradient, which is located in the South China during early summer but migrates northward to the YRV during late summer.

关键词： intraseasonal oscillation precipitation Southeast China

Monsoon Break over the South China Sea during Summer: Statistical Features and Associated Atmospheric Anomalies

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Advances in Atmospheric Sciences 2023年第10期40卷 1749-1765页

作者： Minghao BI Ke XU Riyu LU State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China

This study identifies break events of the South China Sea(SCS)summer monsoon(SCSSM)based on 42 years of data from 1979 to 2020,and investigates their statistical characteristics and associated atmospheric anomalies.A total of 214 break events are identified by examining the convection evolution during each monsoon season.It is found that most events occur between June and September and show a roughly even distribution.Short-lived events(3–7 days)are more frequent,accounting for about two thirds of total events,with the residual one third for long-lived events(8–24 days).The SCSSM break is featured by drastic variations in various atmospheric variables.Particularly,the convection and precipitation change from anomalous enhancement in adjoining periods to a substantial suppression during the break,with the differences being more than 60 W m−2 for outgoing longwave radiation(OLR)and 10 mm d−1 for precipitation.This convection/precipitation suppression is accompanied by an anomalous anticyclone in the lower troposphere,corresponding to a remarkable westward retreat of the monsoon trough from the Philippine Sea to the Indochina Peninsula,which reduces the transportation of water vapor into the SCS.Besides,the pseudo-equivalent potential temperature()declines sharply,mainly attributable to the local specific humidity reduction caused by downward dry advection.Furthermore,it is found that the suppressed convection and anomalous anticyclone responsible for the monsoon break form near the equatorial western Pacific and then propagate northwestward to the SCS.

关键词： South China Sea summer monsoon monsoon break atmospheric circulation convection

Contrasts between the Interannual Variations of Extreme Rainfall over Western and Eastern Sichuan in Mid-summer

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Advances in Atmospheric Sciences 2022年第6期39卷 999-1011页

作者： Mengyu DENG Riyu LU Chaofan LI State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Center for Monsoon System Research Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of the Chinese Academy of SciencesBeijing 100049China Institute of Plateau Meteorology China Meteorological Administration(CMA)Chengdu 610072China Heavy Rain and Drought-Flood Disasters in Plateau and Basin Key Laboratory of Sichuan Province Chengdu 610072China

Rainfall amount in mid-summer(July and August)is much greater over eastern than western Sichuan,which are characterized by basin and plateau,respectively.It is shown that the interannual variations of extreme rainfall over these two regions are roughly independent,and they correspond to distinct anomalies of both large-scale circulation and sea surface temperature(SST).The enhanced extreme rainfall over western Sichuan is associated with a southward shift of the Asian westerly jet,while the enhanced extreme rainfall over eastern Sichuan is associated with an anticyclonic anomaly in the upper troposphere over China.At low levels,on the other hand,the enhanced extreme rainfall over western Sichuan is related to two components of wind anomalies,namely southwesterly over southwestern Sichuan and northeasterly over northeastern Sichuan,which favor more rainfall under the effects of the topography.Relatively speaking,the enhanced extreme rainfall over eastern Sichuan corresponds to the low-level southerly anomalies to the east of Sichuan,which curve into northeasterly anomalies over the basin when they encounter the mountains to the north of the basin.Therefore,it can be concluded that the topography in and around Sichuan plays a crucial role in inducing extreme rainfall both over western and eastern Sichuan.Finally,the enhanced extreme rainfall in western and eastern Sichuan is related to warmer SSTs in the Maritime Continent and cooler SSTs in the equatorial central Pacific,respectively.

关键词： extreme rainfall Sichuan interannual variation topography large-scale circulation

A teleconnection pattern of upper-tropospheric circulation anomalies over the Eurasian continent associated with the interannual variability of atmospheric convection over the tropical western North Pacific in July

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Atmospheric and Oceanic Science Letters 2024年第3期17卷 20-24页

作者： Peishan Chen Riyu LU State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of Sciences BeijingChina College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijingChina

热带西北太平洋大气对流的年际变化对东亚夏季气候有着显著影响,而且受到前冬ENSO的影响.然而,还有相当多的西北太平洋对流年际变化不能由前冬ENSO解释.本文表明,7月西北太平洋对流受到欧亚大陆对流层上层遥相关型的显著影响,且这一影... 详细信息

热带西北太平洋大气对流的年际变化对东亚夏季气候有着显著影响,而且受到前冬ENSO的影响.然而,还有相当多的西北太平洋对流年际变化不能由前冬ENSO解释.本文表明,7月西北太平洋对流受到欧亚大陆对流层上层遥相关型的显著影响,且这一影响与前冬ENSO的影响程度相当.该遥相关型表现为位于欧洲的气旋式环流异常,中亚的反气旋式环流异常和东亚带状延伸的气旋式环流异常,并表现为7月对流层上层环流的第一主模态.基于本文的结果并结合前人的研究,作者认为这一遥相关型能通过亚洲急流出口区附近的罗斯贝波破碎引起西北太平洋对流异常.

关键词：遥相关大气对流西北太平洋年际变化

Decadal Change in the Influence of the Western North Pacific Subtropical High on Summer Rainfall over the Yangtze River Basin in the Late 1970s

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Advances in Atmospheric Sciences 2021年第11期38卷 1823-1834页

作者： Xinyu LI Riyu LU Key Laboratory of Marine Hazards Forecasting Ministry of Natural ResourcesHohai UniversityNanjing 210098China State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of the Chinese Academy of SciencesBeijing 100049China College of Oceanography Hohai UniversityNanjing 210098China

It is well known that on the interannual timescale,the westward extension of the western North Pacific subtropical high(WNPSH)results in enhanced rainfall over the Yangtze River basin(YRB)in summer,and vice versa.This study identifies that this correspondence experiences a decadal change in the late 1970s.That is,the WNPSH significantly affects YRB precipitation(YRBP)after the late 1970s(P2)but not before the late 1970s(P1).It is found that enhanced interannual variability of the WNPSH favors its effect on YRB rainfall in P2.On the other hand,after removing the strong WNPSH cases in P2 and making the WNPSH variability equivalent to that in P1,the WNPSH can still significantly affect YRB rainfall,suggesting that the WNPSH variability is not the only factor that affects the WNPSH-YRBP relationship.Further results indicate that the change in basic state of thermal conditions in the tropical WNP provides a favorable background for the enhanced WNPSH-YRBP relationship.In P2,the lower-tropospheric atmosphere in the tropical WNP gets warmer and wetter,and thus the meridional gradient of climatological equivalent potential temperature over the YRB is enhanced.As a result,the WNPSH-related circulation anomalies can more effectively induce YRB rainfall anomalies through affecting the meridional gradient of equivalent potential temperature over the YRB.

关键词： Yangtze River basin western North Pacific subtropical high rainfall interannual relationship decadal change

Projected Increase in Probability of East Asian Heavy Rainy Summer in the 21st Century by CMIP5 Models

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Advances in Atmospheric Sciences 2021年第10期38卷 1635-1650页

作者： Yuanhai FU Riyu LU Dong GUO Climate Change Research Center Chinese Academy of SciencesBeijing 100029China National Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China

In the summer of 1998,heavy rainfall persisted throughout the summer and resulted in a severe prolonged flooding event over East Asia.Will a similar rainy summer happen again?To date,many studies have investigated projected changes in the seasonality or daily extreme precipitation events over East Asia;however,few studies have focused on the changes in extreme summer-averaged East Asian rainfall.This type of summer is referred to as a“heavy rainy summer(HRS)”in this study,and an investigation of future changes in its probability is performed by analyzing CMIP5 model outputs in historical climate simulation(HIST)and under RCP4.5 and RCP8.5.All models project increased probabilities of HRS by a factor of two to three.The projected East Asian summer rainfall(EASR)(EASRRCPs−EASRHIST)in both climatology and HRS is expected to intensify significantly.The increased EASR could be attributed to significantly intensified water vapor transport(WVT)originating from the tropical Indian Ocean(TIO)and the eastern subtropical North Pacific(SNP),which is a result of the thermodynamic component.The WVT from the TIO would supply more moisture for EASR because of its stronger intensity and faster rate of increase.Meanwhile,the EASR anomaly in HRS relative to climatology(EASRHRS−EASRCLM)would increase by approximately 11%-33%.In HIST,the associated WVT anomaly,caused only by the dynamic component,converges moisture from adjacent land and ocean.However,under the RCPs,the WVT anomaly from the TIO,resulted from the thermodynamic component,would appear and increase by a factor of three to be comparable to the WVT anomaly from the eastern SNP.The latter would result from the dynamic component but increase by only half.

关键词： East Asian summer rainfall water vapor transport heavy precipitation climate change CMIP5

Vertical Structure of Interannual Variability in Cross-Equatorial Flows over the Maritime Continent and Indian Ocean in Boreal Summer

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Advances in Atmospheric Sciences 2020年第2期37卷 173-186页

作者： Xiaoxuan ZHAO Riyu LU State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China

This study investigates the vertical structure of variability in the cross-equatorial flows(CEFs)over the Maritime Continent and Indian Ocean in boreal summer,based on three reanalysis datasets:ERA-Interim,JRA-55 and NCEP-2.The results show a high consistency in the interannual variability among the reanalysis datasets,especially between ERAInterim and JRA-55,while great uncertainty exists in the decadal or long-term changes of CEFs.Further analyses on the interannual variability in CEFs indicate that there is a significant negative relationship between the upper-and lower-level CEFs over the Maritime Continent—that is,the northerlies at the upper level and southerlies at the lower level are both enhanced or weakened.This seesaw pattern is also significantly related to the CEFs over the Indian Ocean at the upper level and lower level(i.e.,the Somali jet).This close relationship between the upper-and lower-level CEFs and between the Maritime Continent and Indian Ocean is manifested as the leading mode of equatorial meridional winds in the vertical-zonal section over the Maritime Continent and Indian Ocean.Finally,it is found that ENSO is closely related to the vertical leading mode,and to all the CEFs at the upper and lower levels over the Maritime Continent and Indian Ocean.

关键词： cross-equatorial flows vertical structure interannual variability ENSO