Modulation of Coupled Modes of Tibetan Plateau Heating and Indian Summer Monsoon on Summer Rainfall over Central Asia

Abstract

Abstract It has been suggested that summer rainfall over central Asia (CA) is significantly correlated with the summer thermal distribution of the Tibetan Plateau (TP) and the Indian summer monsoon (ISM). However, relatively few studies have investigated their synergistic effects of different distribution. This study documents the significant correlations between precipitation in CA and the diabatic heating of TP and the ISM in summer based on the results of statistical analysis and numerical simulation. Summer precipitation in CA is dominated by two water vapor transport branches from the south that are related to the two primary modes of anomalous diabatic heating distribution contributed by the TP and ISM precipitation, that is, the “+−” dipole mode in the southeastern TP and the Indian subcontinent (IS), and the “+−+” tripole mode in the southeastern TP, the IS, and southern India. Both modes exhibit obvious midlatitude Silk Road pattern (SRP) wave trains with cyclone anomalies over CA, but with different transient and stationary eddies over South Asia. The different locations of anomalous anticyclones over India govern two water vapor transport branches to CA, which are from the Arabian Sea and the Bay of Bengal. The water vapor flux climbs while being transported northward and can be transported to CA with the cooperation of cyclonic circulation. The convergent water vapor and ascending motion caused by cyclonic anomalies favor the precipitation in CA. Further analysis corroborates the negative south Indian Ocean dipole in February could affect the tripole mode distribution of TP heating and ISM via the atmospheric circulation, water vapor transport, and anomalous Hadley cell circulation. The results indicate a reliable prediction reference for summer precipitation in CA.