2020 and 1998 are the strongest Meiyu years in recent decades. The characteristics of the super-strong Meiyu precipitation and water vapor sources in 2020 and 1998 were compared, and the atmospheric circulation anomalies and the forcing factor SST were examined. (1) In 2020, the Meiyu duration, accumulated precipitation, and number of rainstorm days were greater than in 1998, and the highest since 1961. The Meiyu period in 2020 experienced 11 rainstorm processes. In 1998, a typical “second Meiyu” phenomenon occurred, and the area of heavy rainfall in 1998 was located further southward than that in 2020 (2) The contribution of the Bay of Bengal-South China Sea (BOB-SCS) to the total supply of water vapor in 2020 and 1998 was 43.0% and 42.0%, respectively, i.e., much higher than that of the climatological mean (25.5%). In 2020, the sources that provide most water vapor were the BOB, SCS, and central Pacific Ocean, while in 1998 were the Arabian Sea, BOB, and the western Pacific Ocean. (3) During the Meiyu period in 2020 and 1998, the position of atmospheric circulation pattern “two ridges and one trough” are different. Analysis of the vertical structure revealed that the specific humidity intensity above the area of heavy rainfall in 1998 was weaker than that in 2020, and the low-level convergence zone was further south and not as strong as in 2020. The positions of the western Pacific subtropical high (WPSH) and the western North Pacific anticyclone (WNPAC) in 1998 were both further south than those in 2020, which resulted in the more southerly locations of the southwesterly jet stream and rain belt. It should be pointed out that, the important contributions of the SST anomalies in the equatorial central eastern Pacific and the tropical Indian Ocean to the anomalous WNPAC in 1998 and 2020, respectively.

中文翻译：

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2020年与1998年超强梅雨期水汽输送特征及环流异常分析对比*

2020年和1998年是近几十年来最强劲的梅雨年。对比2020年和1998年超强梅雨降水和水汽来源特征，考察大气环流异常和强迫因子海表温度。（1）2020年梅雨持续时间、累计降水量、暴雨日数均大于1998年，为1961年以来最高。2020年梅雨期间共经历11次暴雨过程。1998年出现了典型的“二次梅雨”现象，1998年强降雨区域较2020年偏南（2）孟加拉湾—南海（BOB-SCS）对总降雨量的贡献2020年和1998年水汽供应量分别为43.0%和42.0%，远高于气候平均值（25.5%）。2020年，提供最多水汽的来源是BOB、南海和中太平洋，而1998年是阿拉伯海、BOB和西太平洋。(3)2020年和1998年梅雨期间，大气环流格局“两脊一槽”的位置不同。垂直结构分析表明，1998年强降雨区上方比湿强度较2020年弱，低层辐合带进一步南移，强度不及2020年。 西太平洋位置1998年副热带高压（WPSH）和西北太平洋反气旋（WNPAC）均较2020年偏南，导致西南急流和雨带位置更偏南。需要指出的是，赤道中东太平洋和热带印度洋的海温异常分别对1998年和2020年西太平洋异常有重要贡献。