An interdecadal shift in the onset date of the South China Sea summer monsoon(SCSSM) is identified during the late 1990 s by using the European Centre for Medium-Range Weather Forecasts Interim Reanalysis dataset. The...An interdecadal shift in the onset date of the South China Sea summer monsoon(SCSSM) is identified during the late 1990 s by using the European Centre for Medium-Range Weather Forecasts Interim Reanalysis dataset. The mean onset date was brought forward by two pentads during 1999–2013 compared to that during 1979–1998. The large-scale atmospheric and oceanic change associated with this shift exhibits a significant interdecadal variation signal around 1998/1999, indicating that the shift during the late 1990 s is robust. Different from the well-known mid-1990 s shift, this shift carried more important systematical significance. Diagnostic analysis suggests that the earlier outbreak of the SCSSM was due to the interdecadal warming of the warm pool, which brought stronger convection anomalies and led to a weak western Pacific subtropical high(WPSH) during boreal spring(March–May). The earlier retreat of the WPSH was a direct cause of this shift.展开更多
The present study documents the variability of surface sensible heat flux over Northwest China using station observations for the period 1961 2000.It is found that the afternoon and nighttime sensible heat flux variat...The present study documents the variability of surface sensible heat flux over Northwest China using station observations for the period 1961 2000.It is found that the afternoon and nighttime sensible heat flux variations are remarkably different.The variability of the instant flux in the afternoon is much larger than in the nighttime.The afternoon and nighttime flux anomalies tend to be opposite.The diurnal and seasonal dependence of sensible heat flux variations is closely related to the diurnal cycle of mean land-air temperature difference.The relationship of sensible heat flux with land-air temperature difference based on the instant value differs from that based on the daily mean.The present study indicates the importance for the models to properly simulate mean land-air temperature difference and its diurnal and seasonal variations in order to capture surface sensible heat flux variability over Northwest China and predicts its plausible impacts on climate.展开更多
In this paper, we mainly summarize and review the progresses in recent climatological studies(by CMSR,IAP/CAS and some associated domestic and international institutions) on the interannual and interdecadal variabilit...In this paper, we mainly summarize and review the progresses in recent climatological studies(by CMSR,IAP/CAS and some associated domestic and international institutions) on the interannual and interdecadal variabilities of monsoon troughs and their impacts on tropical cyclones and typhoons(TCs) geneses over the western North Pacific Ocean. The climatological characteristics of monsoon troughs and four types of circulation patterns favorable to TCs genesis over the western North Pacific Ocean in summer and autumn are given in this paper. It is also shown in this paper that the monsoon trough over the western North Pacific Ocean has obvious interannual and interdecadal variabilities. Especially, it is revealed in this paper that the interannual and interdecadal variabilities of the monsoon trough over the western North Pacific Ocean influence the TCs genesis not only through the impact on distributions of the vorticity in the lower troposphere and the divergence in the upper troposphere, the water vapor in the mid-and lower troposphere and the vertical shear of wind fields between the upper and lower troposphere over the western North Pacific Ocean, but also through the dynamical effects of the transition between convectively coupled tropical waves and providing disturbance energy. Besides, some climatological problems associated with TCs activity over the western North Pacific Ocean that need to be studied further are also pointed out in this paper.展开更多
In present study,EOF analysis and extended singular value decomposition (ESVD) analysis are performed to explore the relationship between the winter tropical sea surface temperature anomalies (SSTAs) in the Pacific an...In present study,EOF analysis and extended singular value decomposition (ESVD) analysis are performed to explore the relationship between the winter tropical sea surface temperature anomalies (SSTAs) in the Pacific and the following summer rainfall anomalies in China.The two leading modes of winter tropical SSTAs in the Pacific are the SSTAs pattern characterized by "positive anomalies in the East and negative anomalies in the West" like the typical eastern Pacific El Nio and negative anomalies in the West and the central Pacific warming pattern characterized by "positive anomalies in the central region but negative anomalies in the East and West".The intraseasonal variations of the rainfall anomalies during the following summer in China that are associated with the eastern Pacific warming mode are characterized by positive anomalies south of the Yangtze River and negative anomalies in the Yangtze-Huai River Valley in June,and negative anomalies in South China and positive anomalies in the Yangtze River Valley and North China in July and August.In contrast,after the central Pacific warming mode,the corresponding intraseasonal variations of China’s summer rainfall are characterized by a nearly consistent pattern during the three summer months,which is positive in the South China coast and North China and negative in the Yangtze River Valley except for the positive anomalies in the Yangtze-Huai River Valley in July.These results may provide a reference for the seasonal prediction of the summer drought and flood distributions in China.展开更多
This study evaluates the seasonal cycle of the activity of convectively coupled equatorial waves(CCEWs),including mixed Rossby-gravity(MRG) and tropical depression-type(TD-type) waves,based on the twentieth century ex...This study evaluates the seasonal cycle of the activity of convectively coupled equatorial waves(CCEWs),including mixed Rossby-gravity(MRG) and tropical depression-type(TD-type) waves,based on the twentieth century experiments of 18 global climate models(GCMs) from the Coupled Model Intercomparison Project phase 3(CMIP3).The ensemble result of the 18 GCMs shows that the observed seasonal cycle of MRG and TD-type wave activity cannot be well reproduced.The seasonal transition of wave activity from the southern hemisphere to the northern hemisphere is delayed from April in the observations to May in the simulations,indicating that the simulated active season of tropical waves in the northern hemisphere is delayed and shortened.This delayed seasonal transition of tropical wave activity is associated with a delayed seasonal transition of simulated mean precipitation.The mean precipitation in April and May shows a double-ITCZ problem,and the horizontal resolution is important to the delayed seasonal transition of wave activity.Because of the coincident seasonal cycle of MRG and TD-type wave activity and tropical cyclone(TC) geneses,the delayed seasonal transition of wave activity may imply a similar problem of TC genesis in the GCMs,namely,a delayed and shortened TC season in the northern hemisphere.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.41461164005,41375065,and 41230527)
文摘An interdecadal shift in the onset date of the South China Sea summer monsoon(SCSSM) is identified during the late 1990 s by using the European Centre for Medium-Range Weather Forecasts Interim Reanalysis dataset. The mean onset date was brought forward by two pentads during 1999–2013 compared to that during 1979–1998. The large-scale atmospheric and oceanic change associated with this shift exhibits a significant interdecadal variation signal around 1998/1999, indicating that the shift during the late 1990 s is robust. Different from the well-known mid-1990 s shift, this shift carried more important systematical significance. Diagnostic analysis suggests that the earlier outbreak of the SCSSM was due to the interdecadal warming of the warm pool, which brought stronger convection anomalies and led to a weak western Pacific subtropical high(WPSH) during boreal spring(March–May). The earlier retreat of the WPSH was a direct cause of this shift.
基金supported by the National Basic Research Program of China (Grant No. 2009CB421405)the National Natural Science Foundation of China (Grant Nos.40905027 and 40730952)Program of Knowledge Innovationfor the 3rd period of Chinese Academy of Sciences (Grant No.KZCX2-YW-220)
文摘The present study documents the variability of surface sensible heat flux over Northwest China using station observations for the period 1961 2000.It is found that the afternoon and nighttime sensible heat flux variations are remarkably different.The variability of the instant flux in the afternoon is much larger than in the nighttime.The afternoon and nighttime flux anomalies tend to be opposite.The diurnal and seasonal dependence of sensible heat flux variations is closely related to the diurnal cycle of mean land-air temperature difference.The relationship of sensible heat flux with land-air temperature difference based on the instant value differs from that based on the daily mean.The present study indicates the importance for the models to properly simulate mean land-air temperature difference and its diurnal and seasonal variations in order to capture surface sensible heat flux variability over Northwest China and predicts its plausible impacts on climate.
基金National Natural Science Foundation of China(41375065)National Natural Science Foundation of China(41461164005,41230527)National Key Research and Development Program of China(2016YFA0600603)
文摘In this paper, we mainly summarize and review the progresses in recent climatological studies(by CMSR,IAP/CAS and some associated domestic and international institutions) on the interannual and interdecadal variabilities of monsoon troughs and their impacts on tropical cyclones and typhoons(TCs) geneses over the western North Pacific Ocean. The climatological characteristics of monsoon troughs and four types of circulation patterns favorable to TCs genesis over the western North Pacific Ocean in summer and autumn are given in this paper. It is also shown in this paper that the monsoon trough over the western North Pacific Ocean has obvious interannual and interdecadal variabilities. Especially, it is revealed in this paper that the interannual and interdecadal variabilities of the monsoon trough over the western North Pacific Ocean influence the TCs genesis not only through the impact on distributions of the vorticity in the lower troposphere and the divergence in the upper troposphere, the water vapor in the mid-and lower troposphere and the vertical shear of wind fields between the upper and lower troposphere over the western North Pacific Ocean, but also through the dynamical effects of the transition between convectively coupled tropical waves and providing disturbance energy. Besides, some climatological problems associated with TCs activity over the western North Pacific Ocean that need to be studied further are also pointed out in this paper.
基金supported by the National Basic Research Program of China (Grant No.2009CB421405)the Major Research Plan of the National Natural Science Foundation of China (Grant No.40890151)+1 种基金the National Natural Science Foundation of China (Grant No.40730952)the Key Projects in the National Science & Technology Pillar Program in the Eleventh Five-year Plan Period (Grant No.2006BAC03B03)
文摘In present study,EOF analysis and extended singular value decomposition (ESVD) analysis are performed to explore the relationship between the winter tropical sea surface temperature anomalies (SSTAs) in the Pacific and the following summer rainfall anomalies in China.The two leading modes of winter tropical SSTAs in the Pacific are the SSTAs pattern characterized by "positive anomalies in the East and negative anomalies in the West" like the typical eastern Pacific El Nio and negative anomalies in the West and the central Pacific warming pattern characterized by "positive anomalies in the central region but negative anomalies in the East and West".The intraseasonal variations of the rainfall anomalies during the following summer in China that are associated with the eastern Pacific warming mode are characterized by positive anomalies south of the Yangtze River and negative anomalies in the Yangtze-Huai River Valley in June,and negative anomalies in South China and positive anomalies in the Yangtze River Valley and North China in July and August.In contrast,after the central Pacific warming mode,the corresponding intraseasonal variations of China’s summer rainfall are characterized by a nearly consistent pattern during the three summer months,which is positive in the South China coast and North China and negative in the Yangtze River Valley except for the positive anomalies in the Yangtze-Huai River Valley in July.These results may provide a reference for the seasonal prediction of the summer drought and flood distributions in China.
基金supported financially by the National Basic Research Program of China (Grant No.2010CB950403)the National Natural Science Foundation of China (Major Research,Grant No. 40890151+2 种基金Grant Nos.40921160379 and 41105047)supported by the National Science Council (Grant No. NSC98-2745-M-001-005-MY3)supported by the National Science Foundation and the Office of Science (BER) of the U.S. Department of Energy
文摘This study evaluates the seasonal cycle of the activity of convectively coupled equatorial waves(CCEWs),including mixed Rossby-gravity(MRG) and tropical depression-type(TD-type) waves,based on the twentieth century experiments of 18 global climate models(GCMs) from the Coupled Model Intercomparison Project phase 3(CMIP3).The ensemble result of the 18 GCMs shows that the observed seasonal cycle of MRG and TD-type wave activity cannot be well reproduced.The seasonal transition of wave activity from the southern hemisphere to the northern hemisphere is delayed from April in the observations to May in the simulations,indicating that the simulated active season of tropical waves in the northern hemisphere is delayed and shortened.This delayed seasonal transition of tropical wave activity is associated with a delayed seasonal transition of simulated mean precipitation.The mean precipitation in April and May shows a double-ITCZ problem,and the horizontal resolution is important to the delayed seasonal transition of wave activity.Because of the coincident seasonal cycle of MRG and TD-type wave activity and tropical cyclone(TC) geneses,the delayed seasonal transition of wave activity may imply a similar problem of TC genesis in the GCMs,namely,a delayed and shortened TC season in the northern hemisphere.
