Analysis of precipitation background of "7.23" Shuicheng landslide

A huge landslide occurred in Chagou group, Pingdi village, Jichang Town, Shuicheng County in Guizhou Province (referred to as "7.23" Shuicheng landslide) at 21:20 on 23 July 2019. Houses were buried, 42 people were killed and 9 people were missing. In this study, the conventional observation data, the encrypted observation data, the FY-2G blackbody temperature (TBB) and the NCEP/NCAR FNL grid-ded reanalysis data are used to diagnose and analyze the environmental conditions of this event. Conclusions are as follows. (1) The landslide occurred 16 hours after the precipitation stopped, with the characteristics of precipitation lag. The main precipitation period occurred at 20-23 BT on 22 July. The maximum rain intensity at 960 m away from the landslide point is 19.5 mm·h^-1 (20-21 o'clock), and the maximum rain intensity at 2.7 km away from the landslide point is 56.9 mm·h^-1 (21-22 BT), which occurred about 24 h before the landslide. (2) There were three rounds of precipitation in the area one week before the landslide, which contributed to the increase of soil water content in the top 100 cm layer, but had weak infiltration effect below 100 cm. (3) The precipitation occurred in the night of 22 July was under the condition of the west-low and east-high on the west side of the subtropical high. Water vapor was abundant and it has some unstable energy. But the abil-ity of triggering uplift was weak. (4) The Meso-β scale convective cloud clusters are the direct influence system of precipitation, which in-creased from 20 to 23 BT on 22 July. The formation of surface Meso-β scale vortex stimulates the regeneration and development of the split convective cloud clusters. (5) The initial convection and precipitation are excited when the weak cold air approachs Shuicheng. The heavy precipitation strengthens on the warm region on the south side of the slow-moving weak cold air mass. (6) The local heavy rain increased the soil soil moisture content, but it is still difficult to judge whether the precipitation is the main cause of the huge landslide. The main cause of the landslide is likely the change of the rock structure of the hillside, which breaks the balance between gravity and supporting force.