Intensified Tibetan Plateau Spring Warming Exacerbate Summer Extreme Precipitation in Central Asia Since the 2000s

Abstract

Spring warming trends over the Tibetan Plateau (TP) have accelerated, coinciding with a significant increase in summer extreme precipitation (June–July) in Central Asia (EPCA), after 2000. This study attempts to throw detailed light on how spring TP warming influences EPCA, with a particular focus on the role of the Indian summer monsoon (ISM) as an intermediary. Warming in central TP since 2000 has altered meridional temperature gradients at the surface and troposphere, shifting the East Asian jet northward and resulting an anomalous anticyclone over the TP and a cyclonic anomaly over western TP. Concurrently, the weakening of the Middle East jet has triggered a cyclonic anomaly over the Arabian Sea and Indian Peninsula (IP), enhancing moisture convergence and increasing precipitation over northeastern IP. The associated diabatic heating has further intensified the cyclonic anomaly over central IP, which persists into June and promotes northward moisture transportation. Combined with the anomalous cyclone over western TP, these changes have contributed to the observed increase in EPCA. In July, the cyclonic anomaly over central IP, located further west, facilitates eastward moisture transport across northern IP. These anomalies, situated west of the monsoon trough, reflect a seasonal westward shift of the ISM and a strengthening of the South Asian High (SAH). This shift drives the development of cyclonic anomalies over eastern Central Asia and anticyclonic anomalies over western Central Asia. Meanwhile, increased low-latitude moisture transportation to the central-western TP and Central Asia further enhances precipitation in central TP, promoting an increase in EPCA.