Abstract:

On the basis of the meteorological observation data and the National Centers for Environmental Prediction reanalysis data and using water vapor flux diagnosis analysis and the hybrid single-particle lagrangian integrated trajectory model, two extreme rainstorms that occurred on May 5—7, 2020 (the “05·06”rainstorm), and June 14—17, 2021 (the “06·15”rainstorm), in the Hotan Prefecture, Xinjiang in the north slope of Kunlun Mountains, China were analyzed to study the transport mechanism of water vapor and its budget in the process. The results revealed that (1) the influence system of the two rainstorms was the Central Asian vortex, and they both received water vapor from the Caspian Sea and Aral Sea. During the two rainstorms, there was a clear easterly jet in the lower troposphere, and the strongest water vapor convergence was at the level of 700-850 hPa. (2) The difference between the two rainstorms was that in the “05·06” rainstorm, the South Asia High was banded. Its water vapor transport path was from the west and east, and mainly from the west, because the west path contributed 88% of the total water vapor transport. However, in the “06·15” rainstorm, the South Asia High was bimodal. Its water vapor transport path was from the north and south, and mainly from the south, which contributed 78% of the total water vapor transport. (3) The southerly flow from the Arabian Sea and Bay of Bengal transported water vapor to the north. When the atmospheric precipitable water in the Hotan region increases, particularly exceeding the average state, heavy precipitation may occur. Rainstorm or extreme rainstorm is more likely to occur when the precipitable water is ≥20 mm.

Key words: extreme rainstorm, north slope of Kunlun Mountains, water vapor source, water vapor transport, vapor budget