Analysis on water vapor characteristics of the "8·18" short-duration heavy rainfall event in Qinghai

A short-duration heavy rainfall event occurred in northeast Qinghai from August 17 to 18, 2022, causing serious casualties and property loss in several cities (counties). The characteristics of atmospheric precipatable water (P_wv), water vapor transport and budget of this short-duration heavy precipitation process were discussed based on the hourly rain gauge records, water vapor dataset from ground-based Global Navigation Satellite System (GNSS) and the ERA5 reanalysis dataset. The results are as follows. (1) The evolution of P_wv has a good indicator for the occurrence and end of heavy precipitation. The 1~2 h before heavy precipitation, there is a sharp rise in P_wv until its peak, while 1~2 h before the end of the heavy precipitation, P_wv decreases suddenly. (2) Before the heavy precipitation, the total column water vapor convergence in the study area increased dramatically, along with an increase in the vertical ascending motion of the airflow at 500 hPa, which laid the foundation for the formation of heavy precipitation. (3) The upper westerly water vapor transport (16.03×10⁶ kg·s⁻¹) is the main water vapor transport channel during the heavy precipitation process. The improvement of water vapor conditions in the early stage of heavy precipitation in northern part of the study area mainly depends on the low-level easterly and southerly winds water vapor transport, while the water vapor transport in southern part of the study area in the early stage of heavy precipitation also depends on the low-level northerly wind water vapor transport.