Climatic change of summer rainstorms and the water vapor budget in the Sichuan Basin

Abstract This study aims to examine the variation characteristics of summer rainstorms and water vapor budget in the Sichuan Basin by using the daily precipitation observation data and the monthly mean ERA-Interim reanalysis data during 1979–2016. The results show that the spatial and temporal distribution of rainstorms in the Sichuan Basin is the result of the interaction between the special topography of the Sichuan Basin and different water vapor transports at low latitudes. The precipitation amount and frequency of rainstorms are mainly affected by the water vapor transports and budgets in different regions, and the intensity of rainstorms is mainly affected by the dynamic effects of regional and local topography, especially in the western and northern basin. The main reasons for the change of summer rainstorms in the Sichuan Basin include the atmospheric circulation over the key area of the air-sea interaction in the tropical region, the anomalies of regional circulation and water vapor transports in the eastern China and the Sichuan Basin. A conceptual model for the summer rainstorm anomaly in the Sichuan Basin is proposed. With the establishments of the consistent easterly (westerly) airflow in the low-latitude tropical area (130–180°E, 0–10°N) and the anticyclone (cyclone) on its north, an anomalous southeasterly (easterly) airflow and a water vapor divergence (convergence) maintain over the eastern and southern China, while an anomalous southeasterly (northeasterly) airflow and a water vapor convergence (divergence) appear over the Sichuan Basin. So, more (fewer) summer rainstorms occur in this region.