Relationship between atmospheric heat source over the Tibetan Plateau and precipitation in the Sichuan–Chongqing region during summer

Abstract

NCEP–NCAR reanalysis data and a 47-yr daily precipitation dataset from a network of 42 rain gauges are used to analyze the atmospheric heat source ( ) anomaly over the Tibetan Plateau (TP) and its influence on the summer precipitation anomaly in the Sichuan–Chongqing region. Results show that the vertical advection of over the central TP is a major factor affecting summer precipitation in the Sichuan–Chongqing region. When the vertical advection of over the central TP is strengthened, the South Asian high shifts further than normal to the south and east, the western Pacific subtropical high shifts further than normal to the south and west, and the Indian low weakens. This benefits the transport of warm moist air from the low latitude oceans to the Sichuan–Chongqing region. Correspondingly, in the high latitudes, two ridges and one trough form, which lead to cool air moving southward. These two air masses converge over the Sichuan–Chongqing region, leading to significant precipitation. In contrast, when the vertical advection of over the central TP is weakened, the South Asian high moves to the north and west, the subtropical high moves eastward and northward, and the Indian low strengthens. This circulation pattern is unfavorable for warm air advection from the south to the Sichuan–Chongqing region, and the cool air further north cannot move southward because of the presence of two troughs and one ridge at high latitude. Thus, ascent over the Sichuan–Chongqing region is weakened, resulting in less precipitation.