Assessing the impacts of the spring sensible heat flux over the Tibetan Plateau on Asian summer monsoon rainfall using observational and reanalysis data

Abstract

The influence of the spring sensible heat flux (SHF) over the Tibetan Plateau (TP) on the Asian summer monsoon rainfall (ASMR) has been widely investigated. Previous efforts have mainly used the SHF at meteorological stations located over the central and eastern TP. The relationship between the SHF over the entire TP and the ASMR over a time period of two decades is poorly known. Based on observational and reanalysis datasets, we analysed the impact of SHF anomalies on the ASMR from 1984 to 2007. Lag correlation analysis showed that the May SHF and atmospheric heat source (AHS) anomalies over the TP can persist until June and June–July, respectively. Partial correlation analysis, which removed the effects of the El Niño Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO), was performed. Summer rainfall in northern China and northern India were positively correlated with the late spring SHF, while in western India and southern China, it was negatively correlated. The mechanism of these associations was demonstrated by composite analysis of winds and water vapour transport in the years of anomalously high and low SHF over the TP. The results highlight the importance of the changes in the surface and atmospheric conditions in late spring over the TP, which exert a significant influence on the ASMR through sensible heat anomalies.