Previous studies have shown that meridional displacement of the East Asian upper-tropospheric jet stream (EAJS) dominates interannual variability of the EAJS in the summer months.This study investigates the tropical P...Previous studies have shown that meridional displacement of the East Asian upper-tropospheric jet stream (EAJS) dominates interannual variability of the EAJS in the summer months.This study investigates the tropical Pacific sea surface temperature (SST) anomalies associated with meridional displacement of the monthly EAJS during the summer.The meridional displacement of the EAJS in June is significantly associated with the tropical central Pacific SST anomaly in the winter of previous years,while displacements in July and August are related to tropical eastern Pacific SST anomalies in the late spring and concurrent summer.The EAJS tends to shift southward in the following June (July and August) corresponding to a warm SST anomaly in the central (eastern) Pacific in the winter (late spring-summer).The westerly anomaly south of the Asian jet stream is a result of tropical central Pacific warm SST anomaly-related warming in the tropical troposphere,which is proposed as a possible reason for southward displacement of the EAJS in June.The late spring-summer warm SST anomaly in the tropical eastern Pacific,however,may be linked to southward displacement of the EAJS in July and August through a meridional teleconnection over the western North Pacific (WNP) and East Asia.展开更多
East Asian summer rainfall is affected by both the continental northern East Asian low （NEAL） and the western North Pacific subtropical high （WNPSH） in the lower troposphere. This study investigates the joint effe...East Asian summer rainfall is affected by both the continental northern East Asian low （NEAL） and the western North Pacific subtropical high （WNPSH） in the lower troposphere. This study investigates the joint effect of the two circulation factors on East Asian summer rainfall. It is found that the rainfall in East Asia behaves differently in the years with in-phase and out-of-phase variation between the NEAL and WNPSH. When the NEAL and WNPSH vary in phase, i.e. when they are both stronger, the rainfall anomaly shows a dipole pattern in East Asia and displays opposite changes between north and south of 30°N. When the two circulation factors vary out of phase, the rainfall anomaly is concentrated in the Yangtze River valley.展开更多
This study reveals a significant relationship, on the interannual timescale, between a dipole mode, the second leading mode, of spring sea-ice anomalies in the Barents Sea and the following-summer rainfall in East Asi...This study reveals a significant relationship, on the interannual timescale, between a dipole mode, the second leading mode, of spring sea-ice anomalies in the Barents Sea and the following-summer rainfall in East Asia. Related to the dipole mode, with the heavier sea ice in the north and lighter sea ice in the southeast Barents Sea in spring, the East Asian summer subtropical rainy belt tends to move northward. The significant relationship is established through a wave train over northern Eurasia in the lower troposphere in June. The wave train enhances the northern East Asian low, which induces more rainfall to the north of the East Asian subtropical rainy belt and then attracts the subtropical rainy belt to move northward. This study suggests that the dipole mode of spring sea-ice anomalies in the Barents Sea may be a good precursor for the prediction of East Asian summer rainfall.展开更多
The interannual variability of the east asian upper-tropospheric westerly jet（EAJ） in summer is characterized by the meridional displacement of its axis, or a seesaw pattern of zonal wind anomalies between the north...The interannual variability of the east asian upper-tropospheric westerly jet（EAJ） in summer is characterized by the meridional displacement of its axis, or a seesaw pattern of zonal wind anomalies between the northern and southern flanks of the EAJ. This study reveals a close relationship between the surface air temperature in the russian far east and the northern flank of the EAJ. Related to a warmer surface in the russian far east, the westerly decelerates in the northern flank of the EAJ. The relationship can be explained by a positive feedback mechanism between the surface air temperature in the russian far east and the overhead circulation： the anticyclonic circulation anomaly related to a weakened westerly in the northern flank of the EAJ induces surface warming in the russian far east and the warmer surface can in turn act as a heat source and induces a local anticyclonic circulation anomaly in the upper troposphere, therefore decelerating the westerly in the northern flank of the EAJ. The result implies that a better description of the summer surface condition in the russian far east may benefit seasonal forecasts of the EAJ and, subsequently, east asian summer climate.展开更多
The relationship between Indian and East Asian summer rainfall variations is non-stationary in observations as well as in historical simulations of climate models.Is this non-stationarity due to changes in effects of ...The relationship between Indian and East Asian summer rainfall variations is non-stationary in observations as well as in historical simulations of climate models.Is this non-stationarity due to changes in effects of external forcing or internal atmospheric processes？ Whilst ENSO is an important oceanic forcing of Indian and East Asian summer rainfall variations,its impacts cannot explain the observed long-term changes in the Indian-East Asian summer rainfall relationship.Monte Carlo test indicates that the role of random processes cannot be totally excluded in the observed longterm changes of the relationship.Analysis of climate model outputs shows that the Indian-North China summer rainfall relationship displays obvious temporal variations in both individual and ensemble mean model simulations and large differences among model simulations.This suggests an important role played by atmospheric internal variability in changes of the Indian-East Asian summer rainfall relationship.This point of view is supported by results from a 100-years AGCM simulation with climatological SST specified in the global ocean.The correlation between Indian and North China or southern Japan summer rainfall variations displays large fluctuations in the AGCM simulation展开更多
The East Asian summer climate is modulated by a low-pressure system over northern East Asia（NEAL） and a subtropical high over the western North Pacific. Many studies have focused on the subtropical high, but little ...The East Asian summer climate is modulated by a low-pressure system over northern East Asia（NEAL） and a subtropical high over the western North Pacific. Many studies have focused on the subtropical high, but little is known about NEAL, especially its change in the future under global warming scenarios. This study investigates the projected change in NEAL in the late twenty-first century, using the outputs of 20 models from Phase 5 of the Coupled Model Intercomparison Project — specifically, their historical climate simulations（HIST） and future climate projections under the Representative Concentration Pathway 4.5（RCP4.5） and 8.5（RCP8.5） scenarios. The results show that the models capture the NEAL well in HIST. The NEAL is weakened in the late twenty-first century under the two RCP scenarios, with a stronger weakening under RCP8.5 than under RCP4.5.The weakened NEAL increases the geopotential height zonal gradient in the west and causes a southerly anomaly, which may bring more moisture and rainfall to northern East Asia.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 40810059005)
文摘Previous studies have shown that meridional displacement of the East Asian upper-tropospheric jet stream (EAJS) dominates interannual variability of the EAJS in the summer months.This study investigates the tropical Pacific sea surface temperature (SST) anomalies associated with meridional displacement of the monthly EAJS during the summer.The meridional displacement of the EAJS in June is significantly associated with the tropical central Pacific SST anomaly in the winter of previous years,while displacements in July and August are related to tropical eastern Pacific SST anomalies in the late spring and concurrent summer.The EAJS tends to shift southward in the following June (July and August) corresponding to a warm SST anomaly in the central (eastern) Pacific in the winter (late spring-summer).The westerly anomaly south of the Asian jet stream is a result of tropical central Pacific warm SST anomaly-related warming in the tropical troposphere,which is proposed as a possible reason for southward displacement of the EAJS in June.The late spring-summer warm SST anomaly in the tropical eastern Pacific,however,may be linked to southward displacement of the EAJS in July and August through a meridional teleconnection over the western North Pacific (WNP) and East Asia.
基金supported by the National Natural Science Foundation of China[grant number 41375086]
文摘East Asian summer rainfall is affected by both the continental northern East Asian low （NEAL） and the western North Pacific subtropical high （WNPSH） in the lower troposphere. This study investigates the joint effect of the two circulation factors on East Asian summer rainfall. It is found that the rainfall in East Asia behaves differently in the years with in-phase and out-of-phase variation between the NEAL and WNPSH. When the NEAL and WNPSH vary in phase, i.e. when they are both stronger, the rainfall anomaly shows a dipole pattern in East Asia and displays opposite changes between north and south of 30°N. When the two circulation factors vary out of phase, the rainfall anomaly is concentrated in the Yangtze River valley.
基金supported by the National Natural Science Foundation of China[grant numbers 41375086 and 41775062]the National Natural Science Foundation of China[grant number 41630530]+1 种基金the Youth Innovation Promotion Association of the Chinese Academy of Sciences(CAS)supported by the Youth Innovation Promotion Association of CAS
文摘This study reveals a significant relationship, on the interannual timescale, between a dipole mode, the second leading mode, of spring sea-ice anomalies in the Barents Sea and the following-summer rainfall in East Asia. Related to the dipole mode, with the heavier sea ice in the north and lighter sea ice in the southeast Barents Sea in spring, the East Asian summer subtropical rainy belt tends to move northward. The significant relationship is established through a wave train over northern Eurasia in the lower troposphere in June. The wave train enhances the northern East Asian low, which induces more rainfall to the north of the East Asian subtropical rainy belt and then attracts the subtropical rainy belt to move northward. This study suggests that the dipole mode of spring sea-ice anomalies in the Barents Sea may be a good precursor for the prediction of East Asian summer rainfall.
基金supported by the National Natural Science Foundation of China(Grant Nos.41320104007,41775062,41375086,U1502233,and 41775083)
文摘The interannual variability of the east asian upper-tropospheric westerly jet（EAJ） in summer is characterized by the meridional displacement of its axis, or a seesaw pattern of zonal wind anomalies between the northern and southern flanks of the EAJ. This study reveals a close relationship between the surface air temperature in the russian far east and the northern flank of the EAJ. Related to a warmer surface in the russian far east, the westerly decelerates in the northern flank of the EAJ. The relationship can be explained by a positive feedback mechanism between the surface air temperature in the russian far east and the overhead circulation： the anticyclonic circulation anomaly related to a weakened westerly in the northern flank of the EAJ induces surface warming in the russian far east and the warmer surface can in turn act as a heat source and induces a local anticyclonic circulation anomaly in the upper troposphere, therefore decelerating the westerly in the northern flank of the EAJ. The result implies that a better description of the summer surface condition in the russian far east may benefit seasonal forecasts of the EAJ and, subsequently, east asian summer climate.
基金supported by the National Key Research and Development Program of China[grant number 2016YFA0600603]the National Key Basic Research Program of China[grant number 2014CB953902]the National Natural Science Foundation of China[grant number 41661144016],[grant number 41530425],[grant number 41475081],and[grant number 41275081]
文摘The relationship between Indian and East Asian summer rainfall variations is non-stationary in observations as well as in historical simulations of climate models.Is this non-stationarity due to changes in effects of external forcing or internal atmospheric processes？ Whilst ENSO is an important oceanic forcing of Indian and East Asian summer rainfall variations,its impacts cannot explain the observed long-term changes in the Indian-East Asian summer rainfall relationship.Monte Carlo test indicates that the role of random processes cannot be totally excluded in the observed longterm changes of the relationship.Analysis of climate model outputs shows that the Indian-North China summer rainfall relationship displays obvious temporal variations in both individual and ensemble mean model simulations and large differences among model simulations.This suggests an important role played by atmospheric internal variability in changes of the Indian-East Asian summer rainfall relationship.This point of view is supported by results from a 100-years AGCM simulation with climatological SST specified in the global ocean.The correlation between Indian and North China or southern Japan summer rainfall variations displays large fluctuations in the AGCM simulation
基金supported by the National Natural Science Foundation of China[grant number 41375086],[grant number41305063]
文摘The East Asian summer climate is modulated by a low-pressure system over northern East Asia（NEAL） and a subtropical high over the western North Pacific. Many studies have focused on the subtropical high, but little is known about NEAL, especially its change in the future under global warming scenarios. This study investigates the projected change in NEAL in the late twenty-first century, using the outputs of 20 models from Phase 5 of the Coupled Model Intercomparison Project — specifically, their historical climate simulations（HIST） and future climate projections under the Representative Concentration Pathway 4.5（RCP4.5） and 8.5（RCP8.5） scenarios. The results show that the models capture the NEAL well in HIST. The NEAL is weakened in the late twenty-first century under the two RCP scenarios, with a stronger weakening under RCP8.5 than under RCP4.5.The weakened NEAL increases the geopotential height zonal gradient in the west and causes a southerly anomaly, which may bring more moisture and rainfall to northern East Asia.
