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

Abstract

Abstract The long-term characteristics of four 15 hydrometeor species (cloud water, cloud ice, rain, and snow) in precipitating clouds over eastern China (dividing into South China, Jianghuai, and North China) and their relationships with surface rainfall are first investigated using the fifth generation European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis (ERA5) hourly dataset from May to August during 1979-2020. 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 South China and only half in North China. The slope in linear relationship between rain water path and precipitation intensity is the maximum (5.68 h−1) in South China, 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 South China 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 precipitation intensity. Though the contribution of hydrometeor advection to precipitation is generally 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, while the peaks of ice-phase particles occur 2 h and 1 h behind the afternoon precipitation onset in South China and Jianghuai, which is mainly attributed to the different upward velocity and water vapor convergence in the middle-upper troposphere.