双月刊

ISSN 1006-9895

CN 11-1768/O4

中国东部降水中大尺度环流和局地陆气相互作用的贡献:河南“21.7”强降水事件特征影响因子探究
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作者单位:

1.兰州大学大气科学学院;2.中国科学院大气物理研究所竺可桢—南森国际研究中心;3.国家气候中心气候研究开放实验室

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基金项目:

国家杰出青年科学基金 41925021,国家自然科学基金 41875106、41975088


Contributions of Large-Scale Circulation and Local Land-Atmosphere Interaction to Precipitation in Eastern China: Investigation on Influencing Factors of the July 2021 Heavy Precipitation Event in Henan Province
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1.Nansen-Zhu International Research Centre,Institute of Atmospheric Physics,Chinese Academy of Sciences;2.Laboratory for Climate Studies,National Climate Center,China Meteorological Administration

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    摘要:

    2021年7月河南省遭遇突破历史极值的极端强降雨,造成极大人员伤亡和经济损失,同时此次事件暴露出对中国东部汛期降水预测存在一定不足,提示我们需要加强汛期降水和传统影响因子不匹配的机理研究。本文首先利用再分析ERA5月资料识别了与今年7月有相似环流背景的中国东部夏季降水事件;进一步利用基于相似环流型的动力调整方法,对1979-2021年7月中国东部降水距平开展了大尺度环流动力影响和局地陆面作用分离;最后,量化研究了上述两个作用对此次极端降水事件的贡献。得到如下主要结论:2011年是2021年7月的500hPa环流相似年,然而相应降水场在华北到长江中下游地区呈现显著差异。利用动力调整方法从降水距平中分离出大气环流的影响,相关分析表明余项反映局地陆气反馈作用。降水余项是引起2021年7月江淮到长江下游地区的异常强降水的主要原因。归因分析表明,余项主要是由局地热力因子变化引起的,其中,蒸发加强,感热通量显著降低,增加了大气强对流不稳定能量,并通过影响大气相对湿度和边界层高度,使得降水增加。推广到1979-2021年7月降水的演变过程发现,中国东部降水余项的年际变率很强,极端降水异常主要体现在余项中,而环流分量相对稳定,结果强调了局地热力作用对夏季极端降水的重要影响。本研究表明,中国东部夏季降水的预测需要同时考虑大尺度大气环流特征和局地热力作用的贡献,后者对于极端降水预测的贡献尤为重要。

    Abstract:

    A record-breaking precipitation event happened in Henan Province in July 2021, which caused great casualties and economic losses. This event exposed some deficiencies of precipitation prediction in flood-season in Eastern China. This study applied the ERA5 reanalysis product and a dynamic adjustment (DA) approach to explore the respective contributions of large-scale circulation and local land-atmosphere interaction in this extreme precipitation event. In DA, the 500ha geopotential height constructed circulation analogs were used to separate the effects of large-scale circulation dynamics and local land surface effects on precipitation anomalies in Eastern China from 1979 to 2021. Finally, the contribution of these two effects to the extreme precipitation event is quantified. The main conclusions are as follows: 2011 is the similar year of 500hPa circulation with July 2021, while the corresponding precipitation fields show significant differences from North China to the middle and lower reaches of the Yangtze River. The influence of atmospheric circulation is separated from precipitation anomaly after DA. The correlation analysis shows that the residual component of precipitation anomaly reflects local land-atmosphere feedback. The residual is the main cause of the anomalous heavy precipitation from Jianghuai region to the lower Reaches of the Yangtze River in July 2021. Attribution analysis shows that the residual component is mainly caused by the change of local thermal factors, enhanced evaporation reduces sensible heat flux and increases precipitation by affecting atmospheric relative humidity and boundary layer height. Among them, evaporation is strengthened, sensible heat flux is significantly reduced, and the unstable energy of atmospheric strong convection is increased, and precipitation is increased by influencing atmospheric relative humidity and boundary layer height. Extended to the precipitation evolution process from 1979 to 2021 in July, it is found that the interannual variability of precipitation residual component is very strong, the extreme precipitation anomaly is mainly reflected in the residual component, and the circulation component is relatively stable. The results emphasize the important influence of local thermal effect on summer extreme precipitation. This study shows that taking both the characteristics of large-scale atmospheric circulation and the contribution of local thermal effects into consideration is necessary to improve the prediction of summer precipitation in Eastern China, and the latter is particularly important to the prediction of summer extreme precipitation.

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  • 收稿日期:2021-12-11
  • 最后修改日期:2022-08-02
  • 录用日期:2022-10-11
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