The Relationships Of Anomalous Convective Activity Between Tropical Northwest Pacific And The Southeast Tropical Indian Ocean During Boreal Summer

Using the outgoing longwave radiation(OLR)data from NOAA and the NCEP/NCAR reanalysis along with CMAP precipitation data,we have performed the composite analysis to investigate the relationships of convective activities between the tropical northwest Pacific(10°-20°N,125°-140°E)and the tropical southeast India Ocean(5°-15°S,90°-105°E).The results demonstrate that the variations of OLR anomalies in the tropical northwest Pacific and southeast Indian Ocean in the summer are characterized by in-phase and anti-phase patterns.When the OLR anomalies in both two regions are positively signed,there occur the same circulation patterns in the tropical Northwest Pacific Ocean and the southeast Indian Ocean,indicating the anomalous convergence in upper troposphere along with the anomalous divergence in lower troposphere.As a consequence,the weak negative precipitation anomalies are found in the Maritime Continent whereas positive precipitation anomalies are found in eastern China,suggesting the important influences on the climate of north China and Australia.When the OLR anomalies in the tropical northwest Pacific Ocean are positive and the OLR anomalies in the tropical southeast Indian Ocean are negative,the upper level divergence and lower level convergence are found in the tropical southeast Indian Ocean,and the scenario in the tropical Northwest Pacific is opposite.The opposite circulation patterns in these two regions suggest that it may have important influence on the climate of south China coast and the MC region.The in-phase and anti-phase configurations of OLR anomalies in the tropical northwest Pacific Ocean and the southeast Indian Ocean are associated with ENSO and IOD.When the distribution of the OLR anomalies between the tropical northwest Pacific Ocean and the southeast Indian Ocean are in-phase,the SST anomalies of equatorial eastern Pacific Ocean show the ENSO characteristics while the tropical Indian Ocean also featuring with an IOD.When the distribution of the OLR anomalies of the tropical northwest Pacific Ocean and the southeast Indian Ocean are anti-phase,the slanted vertical circulation between the tropical northwest Pacific and southeast Indian Ocean weakens the anomalous Walker circulation,and thus weakens the connection with ENSO.There are significant interdecadal variations in convective activity between the tropical northwest Pacific and the south-eastern Indian Ocean,with a significant positive correlation period from 1980 s through to 1990 s,and a significant negative correlation period from the1990 s through to the beginning of the twenty-first century,and another positive correlation period after 2004.When the convective activities in the tropical Northwest Pacific and the Southeast Indian Ocean are positively correlated,there are two anti-cyclonic circulations overthese two regions,respectively,which lead to weak convective activity in these two places.When the convective activities in the tropical Northwest Pacific and the southeastern Indian Ocean are negatively correlated,the distinctly different circulation anomalies are observed in these two regions.Accordingly,during the negative correlation period,the positive sea temperature anomalies are found in the tropical Southeast Indian Ocean where the upper level divergence and lower level convergence facilitate the anomalous strong convections and more than normal precipitation.This scenario is opposite in the tropical Northwest Pacific.The slanted vertical circulation between the tropical Northwest Pacific and the tropical Southeast Indian Ocean connects these two regions,which induces the negative correlation between convection activities over the two regions.