The establishment of the upper-level South Asian high （SAH） over the Indo-China Peninsula （ICP） during late boreal spring and its possible causes are investigated using long-term NCEP-NCAR and ERA-40 reanalysis an...The establishment of the upper-level South Asian high （SAH） over the Indo-China Peninsula （ICP） during late boreal spring and its possible causes are investigated using long-term NCEP-NCAR and ERA-40 reanalysis and satellite-observed OLR data. Results show that, from early March to mid-April, deep convection stays south of -6°N over the northern Sumatran islands. As the maximum solar radiation moves over the latitudes of the ICP （10-20°N） in late April, the air over the ICP becomes unstable. It ascends over the ICP and descends over the adjacent waters to the east and west. This triggers deep convection over the ICP that induces large latent heating and strong updrafts and upper-level divergence, leading to the formation of an upper-level anticyclonic circulation and the SAH over the ICE During early to mid-May, deep convection over the ICP intensifies and extends northwards to the adjacent waters. Strong latent heating from deep convection enhances and maintains the strong updrafts and upper-level divergence, and the SAH is fully established by mid-May. Thus, the seasonal maximum solar heating and the land-sea contrast around the ICP provide the basic conditions for deep convection to occur preferentially over the ICP, which leads to the formation of the SAH over the ICP from late April to mid-May. Simulations using RegCM4 also indicate that the diabatic heating over the ICP is conducive to the generation and development of upper-level anticyclonic circulation, which leads to an earlier establishment of the SAH.展开更多
The thermal characteristics during the South China Sea (SCS) summer monsoon onset period near the Indo-China Peninsula are analyzed by using the South China Sea Monsoon Experiment (SCSMEX) reanalysis data from 1 May t...The thermal characteristics during the South China Sea (SCS) summer monsoon onset period near the Indo-China Peninsula are analyzed by using the South China Sea Monsoon Experiment (SCSMEX) reanalysis data from 1 May to 31 August 1998 and the NCEP/ NCAR pentad-mean reanalysis data from January 1980 to December 1995. The possible relationships between the anomaly of thermal features near the Indo-China Peninsula and the SCS monsoon onset are investigated, and the mechanism causing the SCS summer monsoon onset is also discussed. Results from the 1998 SCSMEX reanalysis data show that there exists a strong persistent surface sensible heating near the Indo-China Peninsula prior to the SCS monsoon onset, which has apparent low frequency oscillation features. This sensible healing leads lo a warmer center in the lower atmosphere near the Indo-China Peninsula and strong local horizontal temperature and geopotential height gradients which are favorable to strengthening the southwest wind over the Indo-China Peninsula. It is also found that stronger convergent winds at lower levels and stronger divergent winds at high levels appear, which provide a favorable configuration for the development of vertical motion, enhancement of precipitation, and onset of the SCS monsoon. These results can be verified by analysis of the multi-year mean data. Additionally, it is found that the temperature at 850 hPa increases more rapidly over the Indo-China Peninsula than the South China Sea prior to the SCS monsoon onset, which leads to a strengthening of the temperature difference between the Indo-China Peninsula and the South China Sea. Moreover, results from the analysis of the longitudinal temperature and geopotential height differences show that the eastern retreat of the subtropical high over the Indo-China Peninsula during the period of SCS monsoon onset is associated with the temperature increase over the Indo-China Peninsula and the eastern extension of low trough over the Bay of Bengal.展开更多
Seasonal prediction of summer precipitation over eastern China is closely linked to the East Asian monsoon circulation,which is largely affected by the El Niño-Southern Oscillation(ENSO).In this study,results sho...Seasonal prediction of summer precipitation over eastern China is closely linked to the East Asian monsoon circulation,which is largely affected by the El Niño-Southern Oscillation(ENSO).In this study,results show that spring soil moisture(SM)over the Indo-China peninsula(ICP)could be a reliable seasonal predictor for eastern China summer precipitation under non-ENSO conditions.When springtime SM anomalies are present over the ICP,they trigger a structured response in summertime precipitation over most of eastern China.The resultant south-to-north,tri-polar configuration of precipitation anomalies has a tendency to yield increased(decreased)precipitation in the Yangtze River basin and decreased(increased)in South and North China with a drier(wetter)spring soil condition in the ICP.The analyses show that ENSO exerts a powerful control on the East Asian circulation system in the ENSO-decaying summer.In the case of ENSO forcing,the seasonal predictability of the ICP spring SM for eastern China summer precipitation is suppressed.However,in the absence of the influence of ENSO sea surface temperature anomalies from the preceding winter,the SM anomalies over the ICP induce abnormal local heating and a consequent geopotential height response owing to its sustained control on local temperature,which could,in turn,lead to abnormal eastern China summer precipitation by affecting the East Asian summer monsoon circulation.The present findings provide a better understanding of the complexity of summer climate predictability over eastern China,which is of potential significance for improving the livelihood of the people.展开更多
Each year, during the dry season that precedes the summer wind and rainfall Indo-China Peninsula (ICP), significant biomass burning occurs and reaches its peak from March to April. This biomass burning generates large...Each year, during the dry season that precedes the summer wind and rainfall Indo-China Peninsula (ICP), significant biomass burning occurs and reaches its peak from March to April. This biomass burning generates large amounts of aerosols that impact East Asia and surrounding areas through the Asian monsoon. This study aims to investigate the potential connection between biomass burning over the ICP and precipitation in South China during May, along with the physical processes involved. The analysis is based on GLDAS soil moisture reanalysis data and CPC (NOAA) precipitation data covering the period from 1980 to 2021. The research findings indicate a negative (positive) correlation between biomass burning in the ICP region during spring and precipitation in the same region (South China) during May. The circulation patterns corresponding to years with biomass-burning emission anomalies are further investigated, and the impact of biomass-burning emissions in spring on soil moisture and temperature is examined. The results suggest that biomass-burning emissions can significantly affect atmospheric circulation and precipitation, ultimately leading to anomalous precipitation in South China.展开更多
The Asian-Australian “land bridge” is an area with the most vigorous convection in Asian monsoon region in boreal spring, where the onset and march of convection are well associated with the onset of East Asian summ...The Asian-Australian “land bridge” is an area with the most vigorous convection in Asian monsoon region in boreal spring, where the onset and march of convection are well associated with the onset of East Asian summer monsoon. The convection occurs over Indo-China Peninsula as early as mid-April, which exerts critical impact on the evolution of monsoon circulation. Before mid-April there are primarily sensible heatings to the atmosphere over Indo-China Peninsula and Indian Peninsula, so the apparent heating ratios over them decrease with height. However, after mid-April it changes into latent heating over Indo-China Peninsula due to the onset of convection, and the apparent heating ratio increases with height in mid- and lower troposphere. The vertical distribution of heating ratio and its differences between Indo-China Peninsula and Indian Peninsula are the key factors leading to the splitting of boreal subtropical high belt over the Bay of Bengal. Such mechanism is strongly supported by the fact that the evolution of the vertical heating ratio gradient above Indo-China Peninsula leads that of 850 hPa vorticity over the Bay of Bengal. Convections over Indo-China Peninsula and its surrounding areas further increase after the splitting. Since then, there is a positive feedback lying among the convective heating, the eastward retreat of the subtropical high and the march of monsoon, which is a possible mechanism of the advance of summer monsoon and convection from Indo-China Peninsula to South China Sea.展开更多
In the summer of 2020,a super Meiyu event occurred in the Yangtze River basin(YRB),causing enormous economic losses and human casualties.Recent studies have investigated the possible causes of this super Meiyu event f...In the summer of 2020,a super Meiyu event occurred in the Yangtze River basin(YRB),causing enormous economic losses and human casualties.Recent studies have investigated the possible causes of this super Meiyu event from the perspective of anomalous atmospheric circulation activities and sea surface temperature(SST)anomalies;however,the influence of land surface processes has not garnered considerable attention.This study investigates the possible contributions of land surface processes to this extreme event based on observational analysis and numerical simulations,and shows that antecedent soil moisture(SM)anomalies over the Indo-China Peninsula(ICP)may have had a vital influence on the super Meiyu in 2020.Negative SM anomalies in May over the ICP increased the surface temperature and sensible heat flux.The“memory”of soil allowed the anomalies to persist into the Meiyu period.The heating of the lower atmosphere by the surface strengthened the western Pacific subtropical high,which caused an anomalous anticyclone from the ICP to Northwest Pacific and thus enhanced the southwesterly winds and vertical motion over the YRB.Consequently,the water vapor flux and convergence were strengthened.Sensitivity experiments based on the Weather Research and Forecasting(WRF)model further confirmed the results of observational analysis and indicated that the warm air heated by the ICP surface significantly warmed the lower troposphere from the ICP to Northwest Pacific under the influence of the background wind,thus increasing the geopotential height and inducing an anticyclone.The results of the sensitivity experiments showed that the SM anomalies in May over the ICP increased the precipitation by 10.6%from June to July over the YRB.These findings can improve our understanding of the mechanism of the super Meiyu event in 2020 and facilitate the prediction of extreme Meiyu events.展开更多
The seasonal and interannual variations of the thermal contrast between Indo-China Peninsula （ICP） and South China Sea （SCS） were analyzed using the pentad mean NCEP/NCAR reanalysis data during 1958-1998 and the p...The seasonal and interannual variations of the thermal contrast between Indo-China Peninsula （ICP） and South China Sea （SCS） were analyzed using the pentad mean NCEP/NCAR reanalysis data during 1958-1998 and the pentad mean outgoing long-wave radiation （OLR） data during 1975-1998, along with the effects of such a thermal contrast on the SCS monsoon onset （SCSMO）. It is shown that there exists significant seasonal evolution for such a thermal contrast. The surface temperature of ICP is higher than that of SCS from pentad 3 to pentad 25 due to the sensible heating of the ICP. After pentad 25, such a thermal gradient reverses due to the temperature decrease resulted from the convection and rainfall over the ICP from pentad 22 to pentad 23. Furthermore, the above seasonal evolution of the discussed thermal contrast also demonstrates a remarkable interannual change which plays an important role in the SCSMO. On one hand, the reversion happens prior to （or simultaneously with） the SCSMO each year during 1958- 1998, thus becoming a precondition for the SCSMO. On the other hand, the earlier （later） the date when the surface temperature of ICP becomes higher （lower） than that of the SCS, the later the SCSMO.展开更多
The Openness based on DEM emphasizes the terrain convexity and concavity. It facilitates the interpretation of detailed landforms on the Earth＇s surface. Compared with the layer stacking of ETM＋ with less three-dime...The Openness based on DEM emphasizes the terrain convexity and concavity. It facilitates the interpretation of detailed landforms on the Earth＇s surface. Compared with the layer stacking of ETM＋ with less three-dimensionality and visualizability and with indefinite details of linear images in the deep cutting or deep covered region, the Openness is used for accurate interpretation of tectonic geomorphic units and linear structures. In this paper, the ETM＋ images（741 RGB） and RRIM based on Openness combined with the field geological investigation are used to trace the escaping structure in SE Asia. The east boundary is Ailaoshan shear zone and the west boundary is Uttaradit-Dien Bien Phu fault, which together form the southwards extruding wedge block. The arc boundary surface of the southern Khorat Plateau is jutted to the north. The NW and NE sides of Khorat Plateau are traversed by Uttaradit-Dien Bien Phu fault and Thakhek-Da Nang fault, respectively, resulting in a blocked escaping structure. The SE margins of Truong Son structure belt and Song Ma structure belt are both arcs jutting to SE. These arc structures clamped by faults or related to the fault on one side indicating the material flow direction obviously, are the most specific manifestation of escaping structures. Moreover, these push units are extruded from south to north successively.展开更多
Based on TBB data from GMS of Japan,NCEP/NCAR reanalysis data and precipitation data from CMAP(CPC Merged Analysis of Precipitation),an investigation is carried out of seasonal changes of precipitation and convection ...Based on TBB data from GMS of Japan,NCEP/NCAR reanalysis data and precipitation data from CMAP(CPC Merged Analysis of Precipitation),an investigation is carried out of seasonal changes of precipitation and convection over Asian-Australian 'land bridge' areas and its possible factors.The results show that the precipitation and convection over Sumatra take on clearly seasonal changes with abundant (less) rainfall in winter (summer).The convection over Sumatra moves northwestward rapidly along 'land bridge' in the late-April and the early-May (the 25th pentad) and the rainfall shows similar variations.It is the accelerating of the convection moving that affects directly the subsequent enhancement of the convection over Indo-China Peninsula (ICP) area followed by the rupture of the subtropical high (SH) bands in this region leading to South China Sea (SCS) summer monsoon establishment.The zonal wind at lower troposphere in the equatorial Indian Ocean and the cross-equatorial flow in 105~E are the main factors associated with the accelerating of the convection moving northwestward along 'land bridge'.The further study suggests that the intensity of Sumatra convection has a close relation to the SST:when the central-east equatorial Pacific SST is warmer (colder),i.e.E1 Nino (La Nina) events,the SST in West Pacific warm pool is colder (warmer),Sumatra convection is weaker (stronger).展开更多
基金jointly supported by the Major Program of the Natural Science Researches for Colleges and Universities in Jiangsu Province(Grant No.14KJA170004)the Natural Science Foundation of Jiangsu Province(Grant No.BK20131432)+5 种基金the“333”Project of Jiangsu Province“Qing Lan”Project of Jiangsu Provincethe Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)supported by the U.S.National Science Foundation(Grant No.AGS-1353740)the U.S.Department of Energy’s Office of Science(Grant No.DE-SC0012602)the U.S.National Oceanic and Atmospheric Administration(Grant No.NA15OAR4310086)
文摘The establishment of the upper-level South Asian high （SAH） over the Indo-China Peninsula （ICP） during late boreal spring and its possible causes are investigated using long-term NCEP-NCAR and ERA-40 reanalysis and satellite-observed OLR data. Results show that, from early March to mid-April, deep convection stays south of -6°N over the northern Sumatran islands. As the maximum solar radiation moves over the latitudes of the ICP （10-20°N） in late April, the air over the ICP becomes unstable. It ascends over the ICP and descends over the adjacent waters to the east and west. This triggers deep convection over the ICP that induces large latent heating and strong updrafts and upper-level divergence, leading to the formation of an upper-level anticyclonic circulation and the SAH over the ICE During early to mid-May, deep convection over the ICP intensifies and extends northwards to the adjacent waters. Strong latent heating from deep convection enhances and maintains the strong updrafts and upper-level divergence, and the SAH is fully established by mid-May. Thus, the seasonal maximum solar heating and the land-sea contrast around the ICP provide the basic conditions for deep convection to occur preferentially over the ICP, which leads to the formation of the SAH over the ICP from late April to mid-May. Simulations using RegCM4 also indicate that the diabatic heating over the ICP is conducive to the generation and development of upper-level anticyclonic circulation, which leads to an earlier establishment of the SAH.
基金This study is supported by the Nationul Natural Science Foundation of China under Grant No. 40175021is purtly funded by the Ministry of Education through the start-up project for scientists who have returned from abroud.
文摘The thermal characteristics during the South China Sea (SCS) summer monsoon onset period near the Indo-China Peninsula are analyzed by using the South China Sea Monsoon Experiment (SCSMEX) reanalysis data from 1 May to 31 August 1998 and the NCEP/ NCAR pentad-mean reanalysis data from January 1980 to December 1995. The possible relationships between the anomaly of thermal features near the Indo-China Peninsula and the SCS monsoon onset are investigated, and the mechanism causing the SCS summer monsoon onset is also discussed. Results from the 1998 SCSMEX reanalysis data show that there exists a strong persistent surface sensible heating near the Indo-China Peninsula prior to the SCS monsoon onset, which has apparent low frequency oscillation features. This sensible healing leads lo a warmer center in the lower atmosphere near the Indo-China Peninsula and strong local horizontal temperature and geopotential height gradients which are favorable to strengthening the southwest wind over the Indo-China Peninsula. It is also found that stronger convergent winds at lower levels and stronger divergent winds at high levels appear, which provide a favorable configuration for the development of vertical motion, enhancement of precipitation, and onset of the SCS monsoon. These results can be verified by analysis of the multi-year mean data. Additionally, it is found that the temperature at 850 hPa increases more rapidly over the Indo-China Peninsula than the South China Sea prior to the SCS monsoon onset, which leads to a strengthening of the temperature difference between the Indo-China Peninsula and the South China Sea. Moreover, results from the analysis of the longitudinal temperature and geopotential height differences show that the eastern retreat of the subtropical high over the Indo-China Peninsula during the period of SCS monsoon onset is associated with the temperature increase over the Indo-China Peninsula and the eastern extension of low trough over the Bay of Bengal.
基金supported by the National Natural Science Foundation of China (Grant No. 41831175)the Fundamental Research Funds for the Central Universities (Grant No. B210201029)+2 种基金the Key Scientific and Technological Project of the Ministry of Water Resources, P. R. China (SKS2022001)the Joint Open Project of the KLME and CIC-FEMD (Grant No. KLME202202)the Open Research Fund of the State Key Laboratory of Tropical Oceanography (South China Sea Institute of Oceanology, Chinese Academy of Sciences) (Grant No. LTO2110)
文摘Seasonal prediction of summer precipitation over eastern China is closely linked to the East Asian monsoon circulation,which is largely affected by the El Niño-Southern Oscillation(ENSO).In this study,results show that spring soil moisture(SM)over the Indo-China peninsula(ICP)could be a reliable seasonal predictor for eastern China summer precipitation under non-ENSO conditions.When springtime SM anomalies are present over the ICP,they trigger a structured response in summertime precipitation over most of eastern China.The resultant south-to-north,tri-polar configuration of precipitation anomalies has a tendency to yield increased(decreased)precipitation in the Yangtze River basin and decreased(increased)in South and North China with a drier(wetter)spring soil condition in the ICP.The analyses show that ENSO exerts a powerful control on the East Asian circulation system in the ENSO-decaying summer.In the case of ENSO forcing,the seasonal predictability of the ICP spring SM for eastern China summer precipitation is suppressed.However,in the absence of the influence of ENSO sea surface temperature anomalies from the preceding winter,the SM anomalies over the ICP induce abnormal local heating and a consequent geopotential height response owing to its sustained control on local temperature,which could,in turn,lead to abnormal eastern China summer precipitation by affecting the East Asian summer monsoon circulation.The present findings provide a better understanding of the complexity of summer climate predictability over eastern China,which is of potential significance for improving the livelihood of the people.
文摘Each year, during the dry season that precedes the summer wind and rainfall Indo-China Peninsula (ICP), significant biomass burning occurs and reaches its peak from March to April. This biomass burning generates large amounts of aerosols that impact East Asia and surrounding areas through the Asian monsoon. This study aims to investigate the potential connection between biomass burning over the ICP and precipitation in South China during May, along with the physical processes involved. The analysis is based on GLDAS soil moisture reanalysis data and CPC (NOAA) precipitation data covering the period from 1980 to 2021. The research findings indicate a negative (positive) correlation between biomass burning in the ICP region during spring and precipitation in the same region (South China) during May. The circulation patterns corresponding to years with biomass-burning emission anomalies are further investigated, and the impact of biomass-burning emissions in spring on soil moisture and temperature is examined. The results suggest that biomass-burning emissions can significantly affect atmospheric circulation and precipitation, ultimately leading to anomalous precipitation in South China.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.40305005 and 40225012)the National Key Program for Developing Basic Sciences(Grant No.2004CB418302).
文摘The Asian-Australian “land bridge” is an area with the most vigorous convection in Asian monsoon region in boreal spring, where the onset and march of convection are well associated with the onset of East Asian summer monsoon. The convection occurs over Indo-China Peninsula as early as mid-April, which exerts critical impact on the evolution of monsoon circulation. Before mid-April there are primarily sensible heatings to the atmosphere over Indo-China Peninsula and Indian Peninsula, so the apparent heating ratios over them decrease with height. However, after mid-April it changes into latent heating over Indo-China Peninsula due to the onset of convection, and the apparent heating ratio increases with height in mid- and lower troposphere. The vertical distribution of heating ratio and its differences between Indo-China Peninsula and Indian Peninsula are the key factors leading to the splitting of boreal subtropical high belt over the Bay of Bengal. Such mechanism is strongly supported by the fact that the evolution of the vertical heating ratio gradient above Indo-China Peninsula leads that of 850 hPa vorticity over the Bay of Bengal. Convections over Indo-China Peninsula and its surrounding areas further increase after the splitting. Since then, there is a positive feedback lying among the convective heating, the eastward retreat of the subtropical high and the march of monsoon, which is a possible mechanism of the advance of summer monsoon and convection from Indo-China Peninsula to South China Sea.
基金Supported by the National Key Research and Development Program of China(2022YFF0801603)。
文摘In the summer of 2020,a super Meiyu event occurred in the Yangtze River basin(YRB),causing enormous economic losses and human casualties.Recent studies have investigated the possible causes of this super Meiyu event from the perspective of anomalous atmospheric circulation activities and sea surface temperature(SST)anomalies;however,the influence of land surface processes has not garnered considerable attention.This study investigates the possible contributions of land surface processes to this extreme event based on observational analysis and numerical simulations,and shows that antecedent soil moisture(SM)anomalies over the Indo-China Peninsula(ICP)may have had a vital influence on the super Meiyu in 2020.Negative SM anomalies in May over the ICP increased the surface temperature and sensible heat flux.The“memory”of soil allowed the anomalies to persist into the Meiyu period.The heating of the lower atmosphere by the surface strengthened the western Pacific subtropical high,which caused an anomalous anticyclone from the ICP to Northwest Pacific and thus enhanced the southwesterly winds and vertical motion over the YRB.Consequently,the water vapor flux and convergence were strengthened.Sensitivity experiments based on the Weather Research and Forecasting(WRF)model further confirmed the results of observational analysis and indicated that the warm air heated by the ICP surface significantly warmed the lower troposphere from the ICP to Northwest Pacific under the influence of the background wind,thus increasing the geopotential height and inducing an anticyclone.The results of the sensitivity experiments showed that the SM anomalies in May over the ICP increased the precipitation by 10.6%from June to July over the YRB.These findings can improve our understanding of the mechanism of the super Meiyu event in 2020 and facilitate the prediction of extreme Meiyu events.
基金the Climate Change Project of China Meteorological Administration under Grant No.CCSF2007-2the National Natural Science Foundation of China under Grant No.40633018.
文摘The seasonal and interannual variations of the thermal contrast between Indo-China Peninsula （ICP） and South China Sea （SCS） were analyzed using the pentad mean NCEP/NCAR reanalysis data during 1958-1998 and the pentad mean outgoing long-wave radiation （OLR） data during 1975-1998, along with the effects of such a thermal contrast on the SCS monsoon onset （SCSMO）. It is shown that there exists significant seasonal evolution for such a thermal contrast. The surface temperature of ICP is higher than that of SCS from pentad 3 to pentad 25 due to the sensible heating of the ICP. After pentad 25, such a thermal gradient reverses due to the temperature decrease resulted from the convection and rainfall over the ICP from pentad 22 to pentad 23. Furthermore, the above seasonal evolution of the discussed thermal contrast also demonstrates a remarkable interannual change which plays an important role in the SCSMO. On one hand, the reversion happens prior to （or simultaneously with） the SCSMO each year during 1958- 1998, thus becoming a precondition for the SCSMO. On the other hand, the earlier （later） the date when the surface temperature of ICP becomes higher （lower） than that of the SCS, the later the SCSMO.
基金supported by the National Natural Science Foundation of China (Nos.41172202,41190073,and 41402075)the China Geological Survey (No.1212011121256)the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan (No.MSFGPMR201502)
文摘The Openness based on DEM emphasizes the terrain convexity and concavity. It facilitates the interpretation of detailed landforms on the Earth＇s surface. Compared with the layer stacking of ETM＋ with less three-dimensionality and visualizability and with indefinite details of linear images in the deep cutting or deep covered region, the Openness is used for accurate interpretation of tectonic geomorphic units and linear structures. In this paper, the ETM＋ images（741 RGB） and RRIM based on Openness combined with the field geological investigation are used to trace the escaping structure in SE Asia. The east boundary is Ailaoshan shear zone and the west boundary is Uttaradit-Dien Bien Phu fault, which together form the southwards extruding wedge block. The arc boundary surface of the southern Khorat Plateau is jutted to the north. The NW and NE sides of Khorat Plateau are traversed by Uttaradit-Dien Bien Phu fault and Thakhek-Da Nang fault, respectively, resulting in a blocked escaping structure. The SE margins of Truong Son structure belt and Song Ma structure belt are both arcs jutting to SE. These arc structures clamped by faults or related to the fault on one side indicating the material flow direction obviously, are the most specific manifestation of escaping structures. Moreover, these push units are extruded from south to north successively.
基金supported by the National Natural Science Foundation of China (No.40305005 and N0.40135020)
文摘Based on TBB data from GMS of Japan,NCEP/NCAR reanalysis data and precipitation data from CMAP(CPC Merged Analysis of Precipitation),an investigation is carried out of seasonal changes of precipitation and convection over Asian-Australian 'land bridge' areas and its possible factors.The results show that the precipitation and convection over Sumatra take on clearly seasonal changes with abundant (less) rainfall in winter (summer).The convection over Sumatra moves northwestward rapidly along 'land bridge' in the late-April and the early-May (the 25th pentad) and the rainfall shows similar variations.It is the accelerating of the convection moving that affects directly the subsequent enhancement of the convection over Indo-China Peninsula (ICP) area followed by the rupture of the subtropical high (SH) bands in this region leading to South China Sea (SCS) summer monsoon establishment.The zonal wind at lower troposphere in the equatorial Indian Ocean and the cross-equatorial flow in 105~E are the main factors associated with the accelerating of the convection moving northwestward along 'land bridge'.The further study suggests that the intensity of Sumatra convection has a close relation to the SST:when the central-east equatorial Pacific SST is warmer (colder),i.e.E1 Nino (La Nina) events,the SST in West Pacific warm pool is colder (warmer),Sumatra convection is weaker (stronger).
