Analysis of Precipitation Characteristics and Spectrum Distribution Fitting of Laser Raindrop Spectra

The study of raindrop size distributions (DSDs) is crucial for a deeper understanding of the precipitation formation mechanisms and microphysical characteristics of clouds. It also provides valuable data and practical experience for the development of numerical precipitation forecasting products. This study utilizes one-minute laser raindrop spectrum data from 77 stations in Hebei Province during 2019–2020. Ten precipitation events of different intensities were selected for statistical analysis and microphysical parameter calculations. The drop size spectra were fitted using the Marshall–Palmer (M–P) distribution. Results show that the average DSDs of precipitation events at different intensity levels exhibit parallel similarity. The stronger the rainfall intensity, the broader the spectral shape and the higher the number density. Most precipitation events exhibit a significant peak in the small-drop region, a distinct concave pattern in the mid-size range, and fluctuations in the large-drop region. The small-drop region also features high number density and steep spectral slopes. The trend of spectral concentration correlates well with rainfall intensity, and their peaks are aligned. The variation of rainfall intensity (R) and radar reflectivity factor (Z) generally shows consistent behavior. During stratiform cloud precipitation, the M–P fitted spectra effectively represent the actual distribution of raindrops, with higher correlation coefficients. However, they tend to underestimate small droplets. The fitting is more stable for mid-size droplets but performs poorly in convective precipitation scenarios.