The Relationship Between The Cross Equatorial Flow And The Asian Tropical Summer Monsoon

The whole India summer rainfall data set from The Indian Institute of Tropical Meteorology,monthly Reanalysis data set from European Center for Medium-Range Weather Forecasts(ECMWF),Japan Meteorological Agency/Japan(JRA-55)and National Center for Environment Prediction/National Center for Atmospheric Research(NCEP/NCAR)during 1958-2014 are used to study the characteristics of the cross-equatorial flow and its relationship with Asian tropical summer monsoon.The results indicated that:There are 7 equatorial air currents in the global low level in summer.Their centers are basically distributed at 45 degree E,90 degree E,105 degree E,125 degree E,150 degree E,95 degree W and 1 degree W.The cross equatorial flow in the eastern hemisphere is stronger than the Western Hemisphere,and the cross equatorial flow in Somalia,Bay of Bengal and Philippines has interdecadal changes.Before 1982,there is a strong positive correlation between the India summer monsoon and the Somali equatorial flow,but the correlation significant decline after 1983,due to the effect of Somali equatorial flow from Indian northwest move to the southernmost,and the relationship between Somali equatorial flow and South Asian high pressure is significantly weakened.Before 1986,India summer monsoon has negative correlation with the equatorial airflow of barnsley,but it weakened after 1987 due to the anomalous strong barnsley equatorial flow no longer corresponds to the abnormal strong easterly in the Arabia sea and the west coast of India,and its relationship with the high height field is moved from the tropics to the middle latitude of the northern hemisphere.Therefore,the interdecadal variation of the relationship between the cross equatorial flow and the India summer monsoon is mainly caused by the link change with the high and low level circulation.In addition,India summer monsoon has a little associated with the equatorial flow in the Bay of Bengal and Indochina,and there is no obvious connection between the equatorial airflow in Philippines and the Western Hemisphere;Before 1980,the correlation between the East Asian tropical summer monsoon and the Bay of Bengal equatorial flow was not obvious,but largerly strengthened after 1981.Before 1987,the relationship between the East Asian tropical summer monsoon and the Indochina and Philippines equatorial flow is not obvious,but after 1988 them has interdecadal increased.In addition,there is no obvious connection between the East Asian tropical summer monsoon and the cross equatorial flow in Somalia,barnsley and the Western Hemisphere.The correlation between the cross equatorial flow and the East Asian tropical summer monsoon is enhanced because the cross equatorial flow is strengthened and the influence of the abnormal strong equatorial flow can reach the South China Sea-Northwest Pacific region,and the negative anomaly of the subtropical high in the Northwest Pacific makes the East Asian tropical summer monsoon strengthen.So the relationship between the equatorial flow and the East Asian tropical summer monsoon has interdecadal change is mainly caused by the link change of the circulation in the middle and low level.