中国区域性骤发干旱特征分析
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P466

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国家重点研发计划重点专项(2018YFC1507704)


Analysis of the characteristics of regional flash drought in China
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    摘要:

    基于国家气象信息中心2 400多个观测站的候平均日最高气温、GLDAS 2.0/2.1的土壤湿度、蒸散发资料和ERA5的500 hPa位势高度、925 hPa风场再分析资料,定义了格点骤发干旱指数,在分析1979—2017年4—9月中国区域骤发干旱气候特征和骤发干旱指数的经验正交展开空间模态的基础上,确定骤发干旱发生频繁及变率大的区域,给出了区域性骤发干旱事件的识别标准,并对其演变过程进行合成分析,最后分析了典型个例的要素和环流特征。结果表明:骤发干旱多发于我国南方夏季,其中7月最多,以湖南和浙江地区发生最为频繁,这两个区域也是骤发干旱发生气候变率最大的区域。合成分析显示,高温是两个区域骤发干旱爆发的主要驱动因素:干旱爆发前一候,气温迅速升高,蒸散发快速增大,土壤湿度下降明显。2013年6—7月在湖南区域爆发了两次骤发干旱事件。第一次干旱爆发前,湖南地区500 hPa位势高度迅速增大,异常下沉气流导致降水减少和绝热增温,蒸散发随气温升高而增加,使土壤湿度减少,这次干旱由高温驱动;第二次干旱爆发前期,明显偏西、偏北且稳定的西北太平洋副热带高压使地表太阳净辐射通量增强、近地层的偏南气流使高温维持,蒸散发随降水而变化,这次干旱为降水减少所驱动,高温起促进作用。

    Abstract:

    Based on the climatological average daily maximum temperature of more than 2 400 observation stations of the National Meteorological Information Center, the soil moisture and evapotranspiration data of GLDAS 2.0/2.1, the reanalysis data of 500 hPa geopotential height and 925 hPa wind field of ERA5, the grid sudden drought index was defined. And on the basis of the analysis of the climate characteristics of flash drought and the spatial mode of empirical orthogonal expansion of abrupt drought index in China from April to September during 1979-2017, the regions with frequent flash droughts and high variability were determined, the identification criteria of regional flash drought events were given, and the evolution process was analyzed synthetically. Finally, the elements and circulation characteristics of typical cases were analyzed. Results show that flash droughts occur mostly in summer of southern China, and most frequently in July, especially in Hunan and Zhejiang, which are also the regions with the largest climate variability. Synthetic analysis shows that high temperature is the main driving factor of flash drought outbreak in the two regions: before the drought outbreak, the temperature and the evapotranspiration increases rapidly, and the soil moisture decreases significantly. Two flash drought events occurred in Hunan Province from June to July in 2013. Before the first drought, the 500 hPa geopotential height over Hunan increased rapidly, the abnormal downdraft resulted in the decreasing of precipitation and adiabatic warming, and the evapotranspiration increased with the increasing of temperature, all of which result in the decreasing of soil moisture. So this drought was driven by high temperature; in the early stage of the second drought, the Northwest Pacific subtropical high, which is obviously westward, northward and stable, enhanced the surface net solar radiation flux, maintained the high temperature due to the southerly airflow near the stratum, and the evapotranspiration changed with the precipitation. The drought was driven by the decreasing of precipitation, and the high temperature played a promoting role.

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叶天,余锦华,叶梦茜,谢洁宏.中国区域性骤发干旱特征分析.气象科学,2021,41(3):295-303 YE Tian, YU Jinhua, YE Mengxi, XIE Jiehong. Analysis of the characteristics of regional flash drought in China. Journal of the Meteorological Sciences,2021,41(3):295-303

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  • 收稿日期:2019-10-25
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  • 在线发布日期: 2021-07-05
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