Analysis of the causation and multi-source observations of an extreme rainfall process in warm sector in Anhui Province in 2023

The automatic weather station data,sounding data,ERA5 reanalysis data,dual-polarization radar data and laser raindrop spectra data were used to analyze the causation and characteristics of a heavy precipitation process occurred in Dabie mountainous and the region along Yangtze River during 26-27 May 2023 in Anhui Province.The results show that the precipitation process belonged to the warm-sector heavy rainfall.The strongly uplifted areas,horizontal convergence zone,high-value region of water vapor flux correspond well with heavy rainfall areas.The sounding data at 08:00 on the 27th showed that the stratocumulus curve was rising along the humid adiabatic line,reaching a state of saturation or super-saturation.Affected by the release of latent heat of the condensation of water vapor,the mid-air layer of the atmosphere warmed up rapidly during the night and was significantly higher than that of neighboring areas,forming the warm-core structure.The dual-polarization radar parametric analysis showed the Tongling heavy precipitation rain mass has a high suspended reflectivity factor core and ZDR column,and the HCL product identifies heavy rain and high suspended hailstones,with larger particles of precipitation dominating the rain mass.The Anqing heavy precipitation rain mass had a larger reflectivity factor and K_DP value,a smaller ZDR value,and strong-echo stretch height and lower mass center,with dense small droplets predominating in the rain mass.The average D_m was larger and lg(N_w) was slightly smaller during the peak precipitation period at Tongling station,which was in favor of continental precipitation.The average D_m was smaller and lg(N_w) was larger during the peak precipitation period at Anqing station,and the average spectral width of raindrops with different rainfall intensities was narrower.The increase in rainfall intensity was mainly caused by the increase in the density of particles with different diameters.Thus,the nature of the precipitation was more inclined to oceanic precipitation.