In summer,the Yangtze River valley(YRV)in central–eastern China frequently suffers consecutive extreme rainfall(CER)events,causing floods and huge damages.On the daily timescale,our previous study has shown that the ...In summer,the Yangtze River valley(YRV)in central–eastern China frequently suffers consecutive extreme rainfall(CER)events,causing floods and huge damages.On the daily timescale,our previous study has shown that the Pacific–Japan(PJ)teleconnection is related to the CER events over the YRV,and is a source for long-term(lead time of about 10 days)forecasts of CER events.To facilitate extended-range(lead time of about 20 days)prediction of CER,in the present study,we use the band-pass filter for the PJ teleconnection to keep only the prolonged atmospheric circulation information at the intraseasonal timescale and try to identify more advanced precursors for the CER events over the YRV.Power spectrum analysis was implemented on 9-day sliding mean of the precipitation anomalies.It is found that summer precipitation in YRV has significant 10–40-day oscillations,and the CER events over the YRV are affected by the intraseasonal oscillation(ISO)of the PJ teleconnection.When the ISO of the PJ teleconnection enters its positive phase,it is favorable for CER events to occur.Dynamic diagnoses and model experiments demonstrate that the ISO of the PJ teleconnection is attributed to the intraseasonal convective activities and diabatic heating around the Philippines,which generate significant northward energy dispersion and propagation of Rossby waves up to 16 days prior to occurrences of the CER events in the YRV.The ISO of the PJ teleconnection and the convective activities in the tropical South Asia provide significant and earlier precursors for extended-range forecasts of the CER events along the YRV.展开更多
The unprecedented Zhengzhou heavy rainfall in July 2021 occurred under the background of a northward shift of the western Pacific subtropical high(WPSH).Although the occurrence of this extreme event could not be captu...The unprecedented Zhengzhou heavy rainfall in July 2021 occurred under the background of a northward shift of the western Pacific subtropical high(WPSH).Although the occurrence of this extreme event could not be captured by seasonal predictions,a skillful prediction of the WPSH variation might have warned us of the increased probability of extreme weather events in Central and Northern China.However,the mechanism for the WPSH variation in July 2021 and its seasonal predictability are still unknown.Here,the observed northward shift of the WPSH in July 2021 is shown to correspond to a meridional dipole pattern of the 850-hPa geopotential height to the east of China,the amplitude of which became the strongest since 1979.The meridional dipole pattern is two nodes of the Pacific–Japan pattern.To investigate the predictability of the WPSH variation,a 21-member ensemble of seasonal predictions initiated from the end of June 2021 was conducted.The predictable and unpredictable components of the meridional dipole pattern were identified from the ensemble simulations.Its predictable component is driven by positive precipitation anomalies over the tropical western Pacific.The positive precipitation anomalies are caused by positive horizonal advection of the mean moist enthalpy by southwesterly anomalies to the northwestern flank of anticyclonic anomalies excited by the existing La Niña,which is skillfully predicted by the model.The leading mode of the unpredictable component is associated with the atmospheric internal intraseasonal oscillations,which are not initialized in the simulations.The relative contributions of the predictable and unpredictable components to the observed northward shift of the WPSH at 850 hPa are 28.0%and 72.0%,respectively.展开更多
The northwestern Pacific （NWP） is a fog-prone area, especially the ocean east of the Kuril Islands. The present study analyzes how the Pacific-Japan （PJ） teleconnection pattern influences July sea fog in the fog-p...The northwestern Pacific （NWP） is a fog-prone area, especially the ocean east of the Kuril Islands. The present study analyzes how the Pacific-Japan （PJ） teleconnection pattern influences July sea fog in the fog-prone area using independent datasets. The covariation between the PJ index and sea fog frequency （SFF） index in July indicates a close correlation, with a coefficient of 0.62 exceeding the 99% confidence level. Composite analysis based on the PJ index, a case study, and model analysis based on GFDL-ESM2M, show that in high PJ index years the convection over the east of the Philippines strengthens and then triggers a Rossby wave, which propagates northward to maintain an anticyclonic anomaly in the midlatitudes, indicating a northeastward shift of the NWP subtropical high. The anticyclonic anomaly facilitates the formation of relatively stable atmospheric stratification or even an inversion layer in the lower level of the troposphere, and strengthens the horizontal southerly moisture transportation from the tropical-subtropical oceans to the fog-prone area. On the other hand, a greater meridional SST gradient over the cold flank of the Kuroshio Extension, due to ocean downwelling, is produced by the anticyclonic wind stress anomaly. Both of these two aspects are favorable for the warm and humid air to cool, condense, and form fog droplets, when air masses cross the SST front. The opposite circumstances occur in low PJ index years, which are not conducive to the formation of sea fog. Finally, a multi-model ensemble mean projection reveals a prominent downward trend of the PJ index after the 2030s, implying a possible decline of the SFF in this period.展开更多
This paper reviews the recent progress and research on the variability of tropical cyclones(TCs) at different time scales. Specific focus is placed on how different types of external forcings or climatic oscillations ...This paper reviews the recent progress and research on the variability of tropical cyclones(TCs) at different time scales. Specific focus is placed on how different types of external forcings or climatic oscillations contribute to TC variability in the western North Pacific(WNP). At the intraseasonal scale, recent advances on the distinctive impacts of the Madden–Julian Oscillation(MJO), the Quasi-biweekly Oscillation, and the asymmetric MJO modulation under different El Ni?o–Southern Oscillation(ENSO) states, as well as the influences of the Pacific–Japan teleconnection, are highlighted. Interannually, recent progress on the influences of the ENSO cycle, different flavors of ENSO, and impacts of Indian Ocean warming is presented. In addition, the uncertainty concerning interdecadal TC variations is discussed, along with the recently proposed modulation mechanisms related to the zonal sea surface temperature gradient, the North Pacific Gyre Oscillation, and the Pacific Decadal Oscillation(PDO). It is hoped that this study can deepen our understanding and provide information that the scientific community can use to improve the seasonal forecasting of TCs in the WNP.展开更多
In the past decades, with the increasing frequency of extreme weather and climate events, the world has suffered huge losses. Based on NCEP/NCAR reanalysis data and China regional precipitation data provided by China ...In the past decades, with the increasing frequency of extreme weather and climate events, the world has suffered huge losses. Based on NCEP/NCAR reanalysis data and China regional precipitation data provided by China Meteorological Administration, the extreme precipitation events in eastern China are defined by relative threshold method, and the temporal and spatial characteristics of summer extreme precipitation in eastern China from 1961 to 2016 are analyzed by empirical orthogonal function (EOF), and the reverse distribution of extreme precipitation in the middle and lower reaches of the Yangtze River and south China by Indian Ocean warm pool is revealed influence. The results show that the total amount and frequency of extreme precipitation in summer are concentrated in the Yangtze River Basin and south China. EOF1 decomposition of extreme precipitation reflects the interannual oscillation characteristics of reverse spatial distribution in the Yangtze River Basin and south China. The time series corresponding to EOF1 has significant interannual characteristics. The Pacific-Japan (PJ) teleconnection pattern is a circulation system that significantly affects the spatial-temporal pattern of extreme precipitation in southern China. When the PJ pattern is in the positive phase, the anticyclone controls the south China region, and restrains the convective activity, which results in the decrease of extreme precipitation. The anomalous southwest wind to the south of 30<span style="font-size:10.0pt;font-family:;" "=""><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">°</span></span>N and the anomalous northerly wind to the north of 30<span style="font-size:10.0pt;font-family:;" "=""><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">°</span></span>N converge in the middle and lower reaches of the Yangtze River. Combining with the sufficient water vapor carried by the anomalous southwest airflow at the edge of anticyclone, it is more conducive to the formation of extreme precipitation. The east propagating Kelvin wave in the warm pool of the Indian Ocean is an important reason for the formation of the PJ pattern and finally the formation of extreme precipitation anomalies in China.展开更多
Circulation anomalies in one region sometimes cause circulation anomalies in other regions,and the correlation between such regional circulation anomalies is referred to as the atmospheric teleconnection.Chinese scien...Circulation anomalies in one region sometimes cause circulation anomalies in other regions,and the correlation between such regional circulation anomalies is referred to as the atmospheric teleconnection.Chinese scientists have conducted extensive research on the atmospheric teleconnection patterns,particularly those related to the Asian-Pacific monsoon.This review first introduces the basic concepts and historical development of atmospheric teleconnections,and then presents an overview of the studies related to the Asian-Pacific monsoon in recent years,especially those on the subseasonal timescale.The paper systematically summarizes 26 teleconnection patterns,including their main features and associated pioneering works.Particular emphasis is placed on the East Asian-Pacific teleconnection pattern that propagates poleward along the low-level southwesterly monsoonal winds.The wave train-type teleconnection patterns propagating along the upper-level westerly jets are also briefly reviewed.展开更多
基金Supported by the Strategic Priority Research Program of Chinese Academy of Sciences(XDA20100300)National Key Research and Development Program of China(2019YFC1509101 and 2021YFC2802504)+2 种基金Basic Research Fund of Chinese Academy of Meteorological Sciences(2021Z007)National Natural Science Foundation of China(41375091 and 41205056)Jiangsu Collaborative Innovation Center for Climate Change。
文摘In summer,the Yangtze River valley(YRV)in central–eastern China frequently suffers consecutive extreme rainfall(CER)events,causing floods and huge damages.On the daily timescale,our previous study has shown that the Pacific–Japan(PJ)teleconnection is related to the CER events over the YRV,and is a source for long-term(lead time of about 10 days)forecasts of CER events.To facilitate extended-range(lead time of about 20 days)prediction of CER,in the present study,we use the band-pass filter for the PJ teleconnection to keep only the prolonged atmospheric circulation information at the intraseasonal timescale and try to identify more advanced precursors for the CER events over the YRV.Power spectrum analysis was implemented on 9-day sliding mean of the precipitation anomalies.It is found that summer precipitation in YRV has significant 10–40-day oscillations,and the CER events over the YRV are affected by the intraseasonal oscillation(ISO)of the PJ teleconnection.When the ISO of the PJ teleconnection enters its positive phase,it is favorable for CER events to occur.Dynamic diagnoses and model experiments demonstrate that the ISO of the PJ teleconnection is attributed to the intraseasonal convective activities and diabatic heating around the Philippines,which generate significant northward energy dispersion and propagation of Rossby waves up to 16 days prior to occurrences of the CER events in the YRV.The ISO of the PJ teleconnection and the convective activities in the tropical South Asia provide significant and earlier precursors for extended-range forecasts of the CER events along the YRV.
基金supported by the National Natural Science Foundation of China under Grant No.41988101the Chinese Academy of Sciences under Grant XDA20060102the China Postdoctoral Science Foundation under Grant No.2022T150638 and K.C.Wong Education Foundation.
文摘The unprecedented Zhengzhou heavy rainfall in July 2021 occurred under the background of a northward shift of the western Pacific subtropical high(WPSH).Although the occurrence of this extreme event could not be captured by seasonal predictions,a skillful prediction of the WPSH variation might have warned us of the increased probability of extreme weather events in Central and Northern China.However,the mechanism for the WPSH variation in July 2021 and its seasonal predictability are still unknown.Here,the observed northward shift of the WPSH in July 2021 is shown to correspond to a meridional dipole pattern of the 850-hPa geopotential height to the east of China,the amplitude of which became the strongest since 1979.The meridional dipole pattern is two nodes of the Pacific–Japan pattern.To investigate the predictability of the WPSH variation,a 21-member ensemble of seasonal predictions initiated from the end of June 2021 was conducted.The predictable and unpredictable components of the meridional dipole pattern were identified from the ensemble simulations.Its predictable component is driven by positive precipitation anomalies over the tropical western Pacific.The positive precipitation anomalies are caused by positive horizonal advection of the mean moist enthalpy by southwesterly anomalies to the northwestern flank of anticyclonic anomalies excited by the existing La Niña,which is skillfully predicted by the model.The leading mode of the unpredictable component is associated with the atmospheric internal intraseasonal oscillations,which are not initialized in the simulations.The relative contributions of the predictable and unpredictable components to the observed northward shift of the WPSH at 850 hPa are 28.0%and 72.0%,respectively.
基金supported by a "973" project (Grant No. 2012CB955602) Natural Science Foundation of China and the Shandong Joint Fund for Marine Science Research Centers (Grant No. U1406401)the NSFC (Grant No. 41175006)supported by the Fundamental Research Funds for the Central Universities
文摘The northwestern Pacific （NWP） is a fog-prone area, especially the ocean east of the Kuril Islands. The present study analyzes how the Pacific-Japan （PJ） teleconnection pattern influences July sea fog in the fog-prone area using independent datasets. The covariation between the PJ index and sea fog frequency （SFF） index in July indicates a close correlation, with a coefficient of 0.62 exceeding the 99% confidence level. Composite analysis based on the PJ index, a case study, and model analysis based on GFDL-ESM2M, show that in high PJ index years the convection over the east of the Philippines strengthens and then triggers a Rossby wave, which propagates northward to maintain an anticyclonic anomaly in the midlatitudes, indicating a northeastward shift of the NWP subtropical high. The anticyclonic anomaly facilitates the formation of relatively stable atmospheric stratification or even an inversion layer in the lower level of the troposphere, and strengthens the horizontal southerly moisture transportation from the tropical-subtropical oceans to the fog-prone area. On the other hand, a greater meridional SST gradient over the cold flank of the Kuroshio Extension, due to ocean downwelling, is produced by the anticyclonic wind stress anomaly. Both of these two aspects are favorable for the warm and humid air to cool, condense, and form fog droplets, when air masses cross the SST front. The opposite circumstances occur in low PJ index years, which are not conducive to the formation of sea fog. Finally, a multi-model ensemble mean projection reveals a prominent downward trend of the PJ index after the 2030s, implying a possible decline of the SFF in this period.
基金supported by the National Natural Science Foundation of China[grant number 41675062]the Hong Kong Research Grant Council(RGC)General Research Fund[grant number RGC GRF 11306417]
文摘This paper reviews the recent progress and research on the variability of tropical cyclones(TCs) at different time scales. Specific focus is placed on how different types of external forcings or climatic oscillations contribute to TC variability in the western North Pacific(WNP). At the intraseasonal scale, recent advances on the distinctive impacts of the Madden–Julian Oscillation(MJO), the Quasi-biweekly Oscillation, and the asymmetric MJO modulation under different El Ni?o–Southern Oscillation(ENSO) states, as well as the influences of the Pacific–Japan teleconnection, are highlighted. Interannually, recent progress on the influences of the ENSO cycle, different flavors of ENSO, and impacts of Indian Ocean warming is presented. In addition, the uncertainty concerning interdecadal TC variations is discussed, along with the recently proposed modulation mechanisms related to the zonal sea surface temperature gradient, the North Pacific Gyre Oscillation, and the Pacific Decadal Oscillation(PDO). It is hoped that this study can deepen our understanding and provide information that the scientific community can use to improve the seasonal forecasting of TCs in the WNP.
文摘In the past decades, with the increasing frequency of extreme weather and climate events, the world has suffered huge losses. Based on NCEP/NCAR reanalysis data and China regional precipitation data provided by China Meteorological Administration, the extreme precipitation events in eastern China are defined by relative threshold method, and the temporal and spatial characteristics of summer extreme precipitation in eastern China from 1961 to 2016 are analyzed by empirical orthogonal function (EOF), and the reverse distribution of extreme precipitation in the middle and lower reaches of the Yangtze River and south China by Indian Ocean warm pool is revealed influence. The results show that the total amount and frequency of extreme precipitation in summer are concentrated in the Yangtze River Basin and south China. EOF1 decomposition of extreme precipitation reflects the interannual oscillation characteristics of reverse spatial distribution in the Yangtze River Basin and south China. The time series corresponding to EOF1 has significant interannual characteristics. The Pacific-Japan (PJ) teleconnection pattern is a circulation system that significantly affects the spatial-temporal pattern of extreme precipitation in southern China. When the PJ pattern is in the positive phase, the anticyclone controls the south China region, and restrains the convective activity, which results in the decrease of extreme precipitation. The anomalous southwest wind to the south of 30<span style="font-size:10.0pt;font-family:;" "=""><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">°</span></span>N and the anomalous northerly wind to the north of 30<span style="font-size:10.0pt;font-family:;" "=""><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">°</span></span>N converge in the middle and lower reaches of the Yangtze River. Combining with the sufficient water vapor carried by the anomalous southwest airflow at the edge of anticyclone, it is more conducive to the formation of extreme precipitation. The east propagating Kelvin wave in the warm pool of the Indian Ocean is an important reason for the formation of the PJ pattern and finally the formation of extreme precipitation anomalies in China.
基金Supported by the National Natural Science Foundation of China(42205021 and 42475042)Yunnan Provincial Science and Technology Department(202505AB350001,202403AP140009,202302AN360006,and 202501CF070059)+2 种基金Yunnan Southwest United Graduate School Science and Technology Special Project(202302AP370003)Youth Program of the Institute of Atmospheric PhysicsChinese Academy of Sciences during the 14th Five-Year Plan Period。
文摘Circulation anomalies in one region sometimes cause circulation anomalies in other regions,and the correlation between such regional circulation anomalies is referred to as the atmospheric teleconnection.Chinese scientists have conducted extensive research on the atmospheric teleconnection patterns,particularly those related to the Asian-Pacific monsoon.This review first introduces the basic concepts and historical development of atmospheric teleconnections,and then presents an overview of the studies related to the Asian-Pacific monsoon in recent years,especially those on the subseasonal timescale.The paper systematically summarizes 26 teleconnection patterns,including their main features and associated pioneering works.Particular emphasis is placed on the East Asian-Pacific teleconnection pattern that propagates poleward along the low-level southwesterly monsoonal winds.The wave train-type teleconnection patterns propagating along the upper-level westerly jets are also briefly reviewed.
