A diagnosis of the interannual variation of the summer hydrometeor based on ERA-interim over Eastern China

Abstract

Hydrometeor, which involves precipitation and cloud water net income, is the direct source of precipitation and the main component of cloud. It plays an important role in the climate system. In this study, we analyzed the climatology and interannual variation of the summer hydrometeor over Eastern China during 1979–2016 using ERA-Interim reanalysis datasets. The study region was divided into southern and northern sub-regions. Moreover, the hydrometeor budget analysis was diagnosed to further shed light on the formation and variation of the summer hydrometeor. The results showed that the summer hydrometeor pattern is more over the south and less over the north. In climatology, the hydrometeor is mainly contributed by evaporation and vertical moisture advection over the southern sub-region, while the most significant two contributions are evaporation and horizontal moisture advection over the northern sub-region. The interannual variation of hydrometeor over Eastern China exhibits the “north-south seesaw” pattern, which is mainly caused by atmospheric vertical motion. The hydrometeor interannual variation depends strongly on the vertical and horizontal moisture advections over the northern sub-region, but it is primarily contributed by vertical moisture advection over the southern sub-region. The anomalous anticyclone located over the southeast coast of China - the northwest Pacific is in favor of the northward shift of the Western Pacific Subtropical High (WPSH), leading to the hydrometeor increase over the northern sub-region and the opposite over the southern sub-region. It indicates that the hydrometeor distribution pattern over Eastern China is mainly regulated by the WPSH. Further analysis indicated that the interannual variation of horizontal moisture advection over the northern area and vertical moisture advection are mainly caused by the change of the dynamic component, while the horizontal moisture advection over the southern area has both dynamic and thermodynamic drives, which offset each other.