江淮流域梅雨过程识别及梅雨期分级降水时空特征

在全球气候变化背景下，近60 a江淮流域梅雨特征量及梅雨期分级降水的时空变化特征还不明晰。论文采用江淮流域1961—2020年239个气象站逐日降水、气温和NCEP/NCAR再分析资料识别梅雨过程，研究梅雨入出梅日期等特征量及梅雨期不同量级的雨日数等指标的时空特征，计算城市化对梅雨期强降水的贡献。结果表明：Ⅰ区(江南区)平均入出梅最早，Ⅱ区(长江中下游区)次之，Ⅲ区(江淮区)入出梅最晚，梅雨期长度依次为30、30和24 d，入出梅日和梅雨期长度趋势性均不明显。Ⅰ区平均梅雨雨强最大(367.6 mm)，Ⅱ区次之(298.4 mm)，Ⅲ区最小(253.5mm)；Ⅱ区梅雨雨强显著增加、平均梅雨强度指数最大，最易发生暴力梅，Ⅲ区梅雨强度指数变化最剧烈。江淮流域梅雨量Ⅰ、Ⅱ区中部较大，Ⅰ区雨日数最多，Ⅱ区次之，Ⅲ区最少。梅雨期小雨日数最多、降水发生率最高，中雨、大雨和暴雨依次减少。绝大多数站点小雨、中雨日数趋势性不明显，Ⅱ区中东部大雨、暴雨日数显著增加。绝大多数站点大雨、暴雨降水发生率趋势性不明显，Ⅱ区较多站点小雨、中雨发生率显著下降是其东部梅雨期降水发生率显著减少的原因。暴雨量占梅雨量比例最大...

Identification of Meiyu process and spatiotemporal characteristics of different precipitation levels during the Meiyu period over the Yangtze-Huai River Basin

The spatiotemporal characteristics of Meiyu intensity index and different precipitation levels during the Meiyu period over the Yangtze-Huai River Basin are still unclear during recent 60 years under global climate change. This study used observed daily precipitation and temperature data from 239 meteorological stations over the Yangtze-Huai River basin from 1961 to 2020 combined with NCEP/NCAR reanalysis data to identify the Meiyu process and investigate the spatiotemporal characteristics of Meiyu intensity index, the number of rainy days, precipitation amount, precipitation incidence rate, and precipitation contribution rate of different precipitation levels during the Meiyu period, and calculate the contribution rate of urbanization to heavy precipitation indices during the Meiyu period. It aimed to provide references for early warning of rainstorm and flood events, flood and drought disaster prevention, and water resources regulation in the Yangtze-Huai River Basin during the Meiyu Period. The research results show that: The average Meiyu onset date and ending date were the earliest in area I (Jiangnan area), followed by area II (middle and lower reaches of the Yangtze River) and area III (Jianghuai area), and the length of the Meiyu period was 30 days, 30 days, and 24 days respectively. There was no obvious trend for onset date, ending date, and length of the Meiyu period. The average Meiyu rain intensity in area I was the highest, at 367.6 mm, followed by area II at 298.4 mm and area III at 253.5 mm; the Meiyu rain intensity index in area II showed a significant increasing trend in recent 60 years, and the average Meiyu intensity index was the highest in area Ⅱ. Violent Meiyu are most likely to occur in area II, and the inter-annual variation of the Meiyu intensity index was the largest in area III. Meiyu precipitation amount in the central part of areas Ⅰ and Ⅱ was relatively high, with the highest number of rainy days in area Ⅰ, followed by area Ⅱ and the lowest was found in area Ⅲ. During the Meiyu period, the number of light rain days was the largest and the incidence of precipitation was the highest, while the corresponding indices of moderate rain, heavy rain, and rainstorm decreased in turn. The trend of light rain days and moderate rain days was not obvious for most stations, but the number of heavy rain days and rainstorm days in the central and eastern parts of area II increased significantly. The trend of the incidence of heavy rain and rainstorm was not obvious for most stations, but the incidence of light rain and moderate rain for many sites in area II decreased significantly, which is the reason for the significant decrease of the incidence of precipitation during the Meiyu period in eastern area Ⅱ. Rainstorm amount accounted for the largest proportion of precipitation during the Meiyu period, the contribution rate of rainstorm was also the largest, and heavy rain, moderate rain, and light rain decreased in turn. The significant increasing trend of heavy rain and rainstorm precipitation at the eastern stations in areas I and II is the reason for the significant increasing trend of Meiyu precipitation in this area. The trend of precipitation contribution rates of different magnitudes of precipitation was not obvious for most stations, and only 17 stations in the central and eastern parts of area II showed a significant decreasing trend of the contribution rates of light rain and moderate rain. Urbanization aggravates the increasing trend of heavy precipitation, and the contribution rate of urbanization to R95P and R99P was 10.59% and 17.39%, respectively.