The interannual variations of rainfall over southwest China(SWC) during spring and its relationship with sea surface temperature anomalies(SSTAs) in the Pacific are analyzed, based on monthly mean precipitation data f...The interannual variations of rainfall over southwest China(SWC) during spring and its relationship with sea surface temperature anomalies(SSTAs) in the Pacific are analyzed, based on monthly mean precipitation data from 26 stations in SWC between 1961 and 2010, NCEP/NCAR re-analysis data, and Hadley global SST data. Sensitivity tests are conducted to assess the response of precipitation in SWC to SSTAs over two key oceanic domains, using the global atmospheric circulation model ECHAM5. The interannual variation of rainfall over SWC in spring is very significant.There are strong negative(positive) correlation coefficients between the anomalous precipitation over SWC and SSTAs over the equatorial central Pacific(the mid-latitude Pacific) during spring. Numerical simulations show that local rainfall in the northwest of the equatorial central Pacific is suppressed, and a subtropical anticyclone circulation anomaly is produced, while a cyclonic circulation anomaly in the mid-latitude western Pacific occurs, when the equatorial Pacific SSTAs are in a cold phase in spring. Anomalous northerly winds appear in the northeastern part of SWC in the lower troposphere. Precipitation increases over the Maritime Continent of the western equatorial Pacific, while a cyclonic circulation anomaly appears in the northwest of the western equatorial Pacific. A trough over the Bay of Bengal enhances the southerly flow in the south of SWC. The trough also enhances the transport of moisture to SWC. The warm moisture intersects with anomalous cold air over the northeast of SWC, and so precipitation increases during spring. On the interannual time scale, the impacts of the mid-latitude Pacific SSTAs on rainfall in SWC during spring are not significant, because the mid-latitude Pacific SSTAs are affected by the equatorial central Pacific SSTAs; that is,the mid-latitude Pacific SSTAs are a feedback to the circulation anomaly caused by the equatorial central Pacific SSTAs.展开更多
This research analyzes the variations of the South Asian Summer Monsoon Rainfall Anomaly(SASMRA)between the first development year(Y0)and the following year(Y1)of all multi-year La Ni?a events from 1958 to 2022.During...This research analyzes the variations of the South Asian Summer Monsoon Rainfall Anomaly(SASMRA)between the first development year(Y0)and the following year(Y1)of all multi-year La Ni?a events from 1958 to 2022.During Y0,monsoon precipitation surpasses climatological values,presenting a tripole spatial pattern,whereas Y1 is characterized by below-normal precipitation with a dipole pattern.In certain regions,the difference in precipitation between Y0 and Y1 reaches up to 3 mm day–1.This work provides further insight into the key tropical ocean regions driving the precipitation distinction,and elucidates their coupling mechanisms with large-scale atmospheric circulation anomalies.Influenced by the development of earlier ocean-atmosphere anomaly patterns,the Tropical Indian Ocean and Western Pacific(TIO-WP)warming(cooling)is significant during the summer of Y0(Y1).The elevated sea surface temperature(SST)in Y0 supports an anomalous Western North Pacific(WNP)anticyclone via a Kelvin-wave-induced Ekman divergence mechanism.This anomalous anticyclone intensifies the suppressed convection over the WNP,which results in increased divergence in the upper-level troposphere over the Indian Ocean and South Asian regions,thereby boosting convection.Simultaneously,the easterly winds associated with the strengthened equatorial latitude SST anomaly(SSTA)gradient and the anomalous anticyclone intensified,transporting a large amount of water vapor to the west.The combined moisture and dynamic conditions support the enhanced precipitation in the South Asian region.展开更多
基金National Natural Science Foundation of China(41575083)National Basic Research Program of China(973 Program)(2015CB453200)
文摘The interannual variations of rainfall over southwest China(SWC) during spring and its relationship with sea surface temperature anomalies(SSTAs) in the Pacific are analyzed, based on monthly mean precipitation data from 26 stations in SWC between 1961 and 2010, NCEP/NCAR re-analysis data, and Hadley global SST data. Sensitivity tests are conducted to assess the response of precipitation in SWC to SSTAs over two key oceanic domains, using the global atmospheric circulation model ECHAM5. The interannual variation of rainfall over SWC in spring is very significant.There are strong negative(positive) correlation coefficients between the anomalous precipitation over SWC and SSTAs over the equatorial central Pacific(the mid-latitude Pacific) during spring. Numerical simulations show that local rainfall in the northwest of the equatorial central Pacific is suppressed, and a subtropical anticyclone circulation anomaly is produced, while a cyclonic circulation anomaly in the mid-latitude western Pacific occurs, when the equatorial Pacific SSTAs are in a cold phase in spring. Anomalous northerly winds appear in the northeastern part of SWC in the lower troposphere. Precipitation increases over the Maritime Continent of the western equatorial Pacific, while a cyclonic circulation anomaly appears in the northwest of the western equatorial Pacific. A trough over the Bay of Bengal enhances the southerly flow in the south of SWC. The trough also enhances the transport of moisture to SWC. The warm moisture intersects with anomalous cold air over the northeast of SWC, and so precipitation increases during spring. On the interannual time scale, the impacts of the mid-latitude Pacific SSTAs on rainfall in SWC during spring are not significant, because the mid-latitude Pacific SSTAs are affected by the equatorial central Pacific SSTAs; that is,the mid-latitude Pacific SSTAs are a feedback to the circulation anomaly caused by the equatorial central Pacific SSTAs.
基金Guangdong Major Project of Basic and Applied Basic Research(2020B0301030004)National Key Research and Development Program of China(2023YFF0805300)Civilian Space Programme of China(D040305)。
文摘This research analyzes the variations of the South Asian Summer Monsoon Rainfall Anomaly(SASMRA)between the first development year(Y0)and the following year(Y1)of all multi-year La Ni?a events from 1958 to 2022.During Y0,monsoon precipitation surpasses climatological values,presenting a tripole spatial pattern,whereas Y1 is characterized by below-normal precipitation with a dipole pattern.In certain regions,the difference in precipitation between Y0 and Y1 reaches up to 3 mm day–1.This work provides further insight into the key tropical ocean regions driving the precipitation distinction,and elucidates their coupling mechanisms with large-scale atmospheric circulation anomalies.Influenced by the development of earlier ocean-atmosphere anomaly patterns,the Tropical Indian Ocean and Western Pacific(TIO-WP)warming(cooling)is significant during the summer of Y0(Y1).The elevated sea surface temperature(SST)in Y0 supports an anomalous Western North Pacific(WNP)anticyclone via a Kelvin-wave-induced Ekman divergence mechanism.This anomalous anticyclone intensifies the suppressed convection over the WNP,which results in increased divergence in the upper-level troposphere over the Indian Ocean and South Asian regions,thereby boosting convection.Simultaneously,the easterly winds associated with the strengthened equatorial latitude SST anomaly(SSTA)gradient and the anomalous anticyclone intensified,transporting a large amount of water vapor to the west.The combined moisture and dynamic conditions support the enhanced precipitation in the South Asian region.
