Association between Summer Activity Characteristic Indices of the South Asia High and the West Pacific Subtropical High and Precipitation Distribution in Eastern China

Abstract

In order to further study the characteristic indices and their interactive function based on ERA5 reanalysis data from the European Centre for Medium-term Weather Forecasts （ECMWF） from 2001 to 2020 with the horizontal resolution of 0.25°×0.25°， the intensity index， area index， ridge position and east-west extension ridge point of the South Asian High （SAH） and the West Pacific Subtropical High （WPSH） are calculated in summer by statistical methods.And the distance of the relative position of the longitude and latitude and the same strong and weak years in summer are selected.The influence of their cooperation on the summer precipitation in eastern China is studied by the comparative analysis.The results show as follow： （1） There is a good positive correlation between the intensity index and the area index of the SAH and the WPSH in summer.The pentad changes of the ridgeline position of the SAH is very well related to changes in its intensity and area indices.Better consistency， the more north （south） the SAH deviates， the larger （smaller） its intensity and area are.（2） The changes in pentad of the east-west ridge point between the WPSH and the SAH have a trend of "going towards each other and going away from each other".Under the temporal changes， the sudden change of the zonal position of the SAH is later than that of the meridional position.The interval time of the sudden change is about 4 pentads/20 days.（3） When the SAH and the WPSH are both strong （weak）， the rainfall in the middle and lower reaches of the Yangtze River is much （less）， and the rainfall in South China is less （much）.When their latitudes and longitudes are abnormally close， there is less precipitation in the overlapping area， more precipitation on the northern side of the overlapping area， and the precipitation band is generally zonal.The area from the lower reaches of the Yellow River to the sea estuary has more precipitation， and the precipitation in the south of the Yangtze River and South China less.When their latitude and longitude directions are abnormally far apart， there is more precipitation in South China， and less precipitation in the middle and lower reaches of the Yangtze River.

Keywords

• south asian high （sah）
• west pacific subtropical high （wpsh）
• precipitation
• characteristic index
• the changes in pentad