2020年夏季江淮流域发生的超强梅雨造成了巨大的经济损失和人员伤亡，最新的研究从大气环流异常、海温异常等角度探究了此次超强梅雨发生的可能原因，但陆面过程的影响并未受到关注。为此，我院陆气相互作用研究团队陈海山教授指导的硕士研究生董寅硕基于观测分析和数值模拟探讨了陆面过程对这次超强梅雨的可能贡献，结果表明中南半岛前期的土壤湿度异常对这次超强梅雨具有十分重要的影响。
研究发现，5月中南半岛土壤湿度异常和6‒7月长江中下游地区降水量显著相关（图1），中南半岛地区前期干的土壤使地表温度升高，土壤的“记忆性”使得这种异常可以持续到梅雨期。增暖的地表导致感热通量增加从而加热低层大气，有利于位势高度抬升，使中南半岛到西北太平洋上空出现异常反气旋，西太副高西伸加强，长江中下游地区上空的西南风和垂直运动增强，并导致水汽输送和水汽辐合加强，最终造成梅雨期降水的显著增加。基于WRF模式的数值试验再现了观测的环流和降水异常（图2），结果表明中南半岛5月土壤湿度异常使6‒7月长江中下游地区降水量增加10.6%。中南半岛土壤湿度减少导致地表温度升高，更多的能量以感热的形式加热大气。尽管加热局限在中南半岛的陆面，但是被中南半岛地表加热的暖空气在背景气流西南风的作用下使下游大气升温，位势高度增加，同时暖平流使南北温度梯度增加，有利于持续性锋面降水的发生发展。
Fig. 1. First SVD mode of heterogeneous maps between (a) the SM in May and (b) precipitation during June and July. The black dotted areas are significant at the 5% significance level. (c) The expansion coefficients of the first SVD mode. (d) Time series of the standardized regional average SM over the ICP (black box in Fig. 4a) based on the ERA-5 (black solid line), ESA-CCI (red dash dotted line), and GLDAS (blue dashed line) data. All data are linearly detrended and standardized for the period of 1991–2020 before SVD analysis.
Fig. 2. (a) Daily precipitation (shaded; mm day−1), and 500-hPa wind (vector; m s−1) and geopotential height (red contour; gpm); (b) 700-hPa vertical velocity (shaded; Pa s−1), wind (vector; m s−1), and geopotential height (contour; gpm); (c) water vapor flux (vector; kg m−1 s−11) and its divergence (shaded; 10−1 kg m−1 s−1), vertically integrated from 1000 to 300 hPa; (d) 850-hPa temperature (shaded; Pa s−1), wind (vector; m s−1), and geopotential height (contour; gpm), which are obtained by subtracting CLIM from CTRL and averaged from 1 June to 31 July 2020. The black arrows and white dotted areas are significant at the 5% level.
文章信息：
Dong, Y. S., H. S. Chen, and X. Dong, 2023: Impact of antecedent soil moisture anomalies over the Indo-China Peninsula on the super Meiyu event in 2020. J. Meteor. Res., 37(2), 234–247, doi: 10.1007/s13351-023-2144-4