Implications of wind field evolution characteristics at Maoershan Mountain on the intensity and location of pre-flood season rainstorms in Guilin

Based on hourly wind data from high-altitude meteorological station on Maoershan Mountain in Xing'an County of Guilin, hourly rainfall data from regional meteorological station across Guilin, Guilin station radiosonde records and ERA5 reanalysis data from April to June 2015-2024, this study explores precipitation and wind field features of Maoershan region. It analyzes the represent ativeness of high-altitude station wind observations for lower tropospheric wind and the indicative role of wind evolution on pre-flood rainstorms of Guilin. Main conclusions are as follows. (1) Windward slopes of Maoershan Mountain record higher daily rainfall and severe precipitation frequency than leeward slopes. Wind directions distribute evenly with low wind speeds at high-altitude station on leeward slopes. Stations on windward slopes are dominated by SSW-SW winds with larger wind speeds. (2) Wind direction and speed at high-altitude station on Maoershan Mountain show significant positive correlations with wind parameters at all vertical layers of Guilin radiosonde profiles. Hourly wind data from the 1250 m meteorological station on the southeast side of Maoershan Mountain can capture low-level jet evolution, so this station is set as the indicator station. (3) Hourly wind evolution at high-altitude station on Maoershan Mountain can indicate severe precipitation distribution and intensity. This paper analyzes two rainstorm events on 5 June and 21 June 2022 plus two groups of similar cases. Rainfall over central Guilin strengthens 5~8 hours after wind shifts from south to north at the indicator station. The rainfall over the upper reaches of the Lijiang River intensifies within 0~3 hours after the sharp rise of southerly wind component at the indicator station and the rainfall over central Guilin weakens 3~6 hours after this sharp rise. The results provide practical references for forecast and early warning work of the upper reaches of the Lijiang River and urban areas of Guilin.