Historical La Nia events since 1950 are divided into Eastern Pacific(EP) type and Central Pacific(CP) type,and the SSTA developing features as well as the different responses of the tropical atmosphere are further ana...Historical La Nia events since 1950 are divided into Eastern Pacific(EP) type and Central Pacific(CP) type,and the SSTA developing features as well as the different responses of the tropical atmosphere are further analyzed by using multiple datasets.Classification of different types La Nia is based on the normalized Ni o3 and Ni o4 indices and the SSTA distribution pattern during the mature phase.The minimum negative SSTA for CP La Nia is located over the equatorial central Pacific near the dateline,more westward than that of EP La Nia.It has stronger intensity and larger east-west zonal difference of SSTA over the equatorial Pacific than EP La Nia.Influenced by the different SSTA distribution pattern,CP La Nia induces more westward location of the anomalous sinking motion and the anomalous low-level divergent and high-level convergent winds over the equatorial eastern Pacific.The different response of the tropical atmospheric circulation between EP and CP La Nia is more significant in the upper troposphere than in the lower troposphere.However,the tropical precipitation patterns during the mature phase of EP and CP La Nia are much similar,except the less(more) precipitation over the equatorial central Pacific(eastern Indian Ocean-western Pacific) during CP La Nia than during EP La Nia.展开更多
The relationship between sea surface temperature (SST) east of Australia and tropical cyclone frequency over the western North Pacific (WNPTCF) is analyzed by use of observation data.The WNPTCF from June to October is...The relationship between sea surface temperature (SST) east of Australia and tropical cyclone frequency over the western North Pacific (WNPTCF) is analyzed by use of observation data.The WNPTCF from June to October is correlated negatively to spring SST east of Australia.When the spring SST is in the positive phase,a cyclonic circulation anomaly in the upper troposphere and an anticyclonic circulation anomaly in the lower troposphere prevail over the western North Pacific from June to October,concurrent with an anomalous atmospheric subsidence and an enlarged vertical zonal wind shear.These conditions are unfavorable for tropical cyclone genesis,and thus WNPTCF decreases.The negative phase of the spring SST east of Australia leads to more tropical cyclones over the western North Pacific.The spring SST east of Australia may give rise to simultaneous change in tropical atmospheric circulation via the teleconnection wave train,and then subsequently affect atmospheric circulation variation over the western North Pacific.展开更多
A destructive extreme heat attacked Northeast Asia(NEA)in the midsummer of 2018,characterized by the average midsummer Tmax(daily maximum air temperature at 2 m)ranking first during the study period.The current study ...A destructive extreme heat attacked Northeast Asia(NEA)in the midsummer of 2018,characterized by the average midsummer Tmax(daily maximum air temperature at 2 m)ranking first during the study period.The current study indicates that the cyclonic anomaly over the western North Pacific(WNP)was an important cause,which presents an anomaly of two standard deviations.The cyclonic anomaly over the WNP was accompanied by anomalous convection,which favored descending and anticyclonic anomalies over NEA through a local meridional cell.The anticyclonic anomaly over NEA corresponds to the northwestward extension of the WNP subtropical high and facilitated the occurrence of extreme heat.The tropical sea surface temperature anomaly(SSTA)presents a La Ni?a decaying episode,but the SSTA over the tropical Pacific and North Indian Ocean was weak in the summer.In contrast,the southeastern tropical Indian Ocean(SETIO)was obviously cool,which was the coolest after detrending.The SETIO cooling triggered a low-level southeasterly anomaly,which turned into a southwesterly after crossing the equator,due to the Coriolis force.The southwesterly anomaly extended eastwards and favored the cyclonic anomaly over the WNP.Meanwhile,the circulation anomalies over the SETIO and WNP were connected via a local meridional cell,with the ascending branch over the WNP.Moreover,the above mechanism also operates for the climate statistics,verifying the robust in?uence of the SETIO SSTA.Considering the consistency of the SETIO SSTA,it could be a potential predictor for the climate over the WNP and NEA.展开更多
基金supported by the Young Scientists Fund of the National Natural Science Foundation of China(41005038 and 41065004)the Chinese Public Sector(Meteorology) Research and Special Project (GYHY200906016)the National Key Technology Research and Development Program of China(2009BAC51B01)
文摘Historical La Nia events since 1950 are divided into Eastern Pacific(EP) type and Central Pacific(CP) type,and the SSTA developing features as well as the different responses of the tropical atmosphere are further analyzed by using multiple datasets.Classification of different types La Nia is based on the normalized Ni o3 and Ni o4 indices and the SSTA distribution pattern during the mature phase.The minimum negative SSTA for CP La Nia is located over the equatorial central Pacific near the dateline,more westward than that of EP La Nia.It has stronger intensity and larger east-west zonal difference of SSTA over the equatorial Pacific than EP La Nia.Influenced by the different SSTA distribution pattern,CP La Nia induces more westward location of the anomalous sinking motion and the anomalous low-level divergent and high-level convergent winds over the equatorial eastern Pacific.The different response of the tropical atmospheric circulation between EP and CP La Nia is more significant in the upper troposphere than in the lower troposphere.However,the tropical precipitation patterns during the mature phase of EP and CP La Nia are much similar,except the less(more) precipitation over the equatorial central Pacific(eastern Indian Ocean-western Pacific) during CP La Nia than during EP La Nia.
基金supported by the National Natural Science Foundation of China(40805029)the National Basic Research Program of China(2009CB421407)the Knowledge Innovation Program of the Chinese Academy of Sciences(IAP09302)
文摘The relationship between sea surface temperature (SST) east of Australia and tropical cyclone frequency over the western North Pacific (WNPTCF) is analyzed by use of observation data.The WNPTCF from June to October is correlated negatively to spring SST east of Australia.When the spring SST is in the positive phase,a cyclonic circulation anomaly in the upper troposphere and an anticyclonic circulation anomaly in the lower troposphere prevail over the western North Pacific from June to October,concurrent with an anomalous atmospheric subsidence and an enlarged vertical zonal wind shear.These conditions are unfavorable for tropical cyclone genesis,and thus WNPTCF decreases.The negative phase of the spring SST east of Australia leads to more tropical cyclones over the western North Pacific.The spring SST east of Australia may give rise to simultaneous change in tropical atmospheric circulation via the teleconnection wave train,and then subsequently affect atmospheric circulation variation over the western North Pacific.
基金supported by the National Key R&D Program of China [grant number 2016YFA0600601]the National Natural Science Foundation of China [grant numbers41605027,41530530,and 41721004]the Fundamental Research Funds for the Central Universities
文摘A destructive extreme heat attacked Northeast Asia(NEA)in the midsummer of 2018,characterized by the average midsummer Tmax(daily maximum air temperature at 2 m)ranking first during the study period.The current study indicates that the cyclonic anomaly over the western North Pacific(WNP)was an important cause,which presents an anomaly of two standard deviations.The cyclonic anomaly over the WNP was accompanied by anomalous convection,which favored descending and anticyclonic anomalies over NEA through a local meridional cell.The anticyclonic anomaly over NEA corresponds to the northwestward extension of the WNP subtropical high and facilitated the occurrence of extreme heat.The tropical sea surface temperature anomaly(SSTA)presents a La Ni?a decaying episode,but the SSTA over the tropical Pacific and North Indian Ocean was weak in the summer.In contrast,the southeastern tropical Indian Ocean(SETIO)was obviously cool,which was the coolest after detrending.The SETIO cooling triggered a low-level southeasterly anomaly,which turned into a southwesterly after crossing the equator,due to the Coriolis force.The southwesterly anomaly extended eastwards and favored the cyclonic anomaly over the WNP.Meanwhile,the circulation anomalies over the SETIO and WNP were connected via a local meridional cell,with the ascending branch over the WNP.Moreover,the above mechanism also operates for the climate statistics,verifying the robust in?uence of the SETIO SSTA.Considering the consistency of the SETIO SSTA,it could be a potential predictor for the climate over the WNP and NEA.
