Climatological Characteristics of Hydrometeors in Precipitating Clouds over Eastern China and Their Relationship with Precipitation Based on ERA5 Reanalysis

Reanalysis data and satellite retrievals have been widely used in investigating the cloud water and cloud ice in non-precipitating clouds. However, the studies on the long-term characteristics of precipitating hydrometeors in precipitating clouds are quite lacking due to the limitations in observations of precipitating clouds. In this study, the long-term characteristics of four hydrometeor species (cloud water, cloud ice, rain, and snow) in precipitating clouds over eastern China [dividing into South China (SC), Jianghuai (JH), and North China (NC)] and their relationships with rainfall intensity are first investigated using the latest ERA5 hourly reanalysis dataset from May to August during 1979-2020. The ERA5 hydrometeor and precipitation data are quantitatively compared to the GPM retrieved hydrometeors and CMPAS hourly precipitation product. The results show that the cloud water path decreases significantly from south to north owing to the large-scale circulation and water vapor distribution, with the maximum value of 180 g m^-2 in SC and only half in NC. The slope in linear relationship between rain water path and precipitation intensity is the maximum (5.68 h^-1) in SC, implying the highest conversion rate from rain water to precipitation in this region. When the precipitation rate exceeds 15 mm h^-1, the ice-phase hydrometeor contents in SC become the largest among three regions, indicating the cold rain process is crucial to the heavy rainfall. The moisture-related processes play a dominant role in the surface rainfall intensity. Though the contribution of hydrometeor-related processes to precipitation is only between -5% and 5%, we found that it can jointly modulate the location of heavy rainfall. In addition, the peaks of cloud water path commonly appear 2-3 h ahead of precipitation in the diurnal cycles, while the peaks of ice-phase particles occur 2 h and 1 h behind the afternoon precipitation in SC and JH, and are the same phase in NC. This is attributed to the different structures of upward velocity and water vapor convergence in the middle-upper troposphere. These results are expected to advance our understanding of precipitation mechanisms from the perspective of hydrometeor climatology.

Tang, L., W. Gao*, L. Xue, G. Zhang, and J. Guo, (2023). Climatological Characteristics of Hydrometeors in Precipitating Clouds over Eastern China and Their Relationship with Precipitation Based on ERA5 Reanalysis. J. Appl. Meteorol. and Climatol., https://doi.org/10.1175/JAMC-D-22-0076.1.