Mesoscale Analyses of the Sichuan Flood Catastrophe, 11–15 July 1981

Abstract

Abstract During the period 11–15 July 1981, heavy rainfall occurred over the Sichuan basin in China, resulting in severe floods that took a large toll in human life and property damage. Synoptic analyses indicate that early in this period the southerly monsoon flow was particularly strong near the basin because of a favorable positioning of the Pacific subtropical high and the Indian monsoon depression. The passage of a deep midlatitude trough from the Lake Baikal region brought colder, drier air from Siberia into southwest China. The Siberian air stream met the monsoon current over the eastern plateau and the Sichuan basin, creating a region of large-scale, low-level convergence. Mesoscale analyses show that the flood was directly related to the extreme development of a long-lived mesoscale vortex [called south (SW) vortex by Chinese meteorologists] over the basin as it merged with another mesoscale vortex generated over the Tibetan Plateau. Mesoscale heat and moisture budgets suggest that the latent hea...