2020年7月一場梅雨暴雨的異常空間分布及形成機(jī)制

doi:10.12306/2022jms.0098

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2020年7月一場梅雨暴雨的異常空間分布及形成機(jī)制
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                        10.12306/2022jms.0098
                    
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中圖分類號:P458.3
基金項目:國家自然科學(xué)基金資助項目(42075027; 42075118; 41930969); 國家重點研發(fā)計劃資助項目(2020YFA0608901);大學(xué)生創(chuàng)新創(chuàng)業(yè)訓(xùn)練計劃(XJDC202210300005)

Abnormal precipitation pattern of a Meiyu rainstorm event and its dynamical and thermodynamically mechanism in July, 2020

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利用GPCP逐日降水資料、NCEP/NCAR和ERA5再分析資料,研究了2020年7月17—19日長江梅雨大暴雨異常空間分布及成因。結(jié)果表明,強(qiáng)降水主雨帶在長江下游呈緯向分布,與長江干流位置重合、走向一致、長江中游雨帶為西南—東北走向。中高層大氣環(huán)流出現(xiàn)"兩脊一槽"的異常大氣環(huán)流型,南亞高壓主體強(qiáng)盛東伸,副高西北側(cè)水汽通道持續(xù)維持,為暴雨的形成和維持提供了有利環(huán)流背景。17—18日高空西風(fēng)急流呈緯向分布、副高控制華南、低空西南急流持續(xù)加強(qiáng)并東移;19日高空西風(fēng)急流轉(zhuǎn)為"V"型分布,江淮氣旋形成,長江中下游位于高空急流入口區(qū)南側(cè)、副高的西北側(cè)和低空西南急流出口區(qū)北側(cè)。"兩脊一槽"和"V"型大氣環(huán)流配置結(jié)構(gòu)使得上層的"抽吸"作用和下層的抬升活動相重疊,伴有江淮氣旋的輻合作用,導(dǎo)致強(qiáng)烈的上升運動,易產(chǎn)生大暴雨。過程內(nèi)高低空急流和副高位置和形態(tài)的變化是暴雨空間分布出現(xiàn)變化的主要原因。診斷結(jié)果顯示,熱力因子對抬升活動起主要作用,位渦垂直輸送和非絕熱加熱隨氣壓變化項均有利于位渦增強(qiáng),假相當(dāng)位溫在500 hPa與850 hPa之差的峰值、強(qiáng)上升運動和位渦高值區(qū)與強(qiáng)降水中心重合為本次大暴雨形成提供了有利的熱力與動力條件。假相當(dāng)位溫在500 hPa與850 hPa之差的谷值具有較好前期預(yù)報指示意義。

Abstract:

Based on the GPCP daily precipitation data, the NCEP/NCAR and ERA5 reanalysis data, the abnormal spatial characteristics and the physical mechanism of a Meiyu rainstorm event in the middle and lower reaches of the Yangtze River on July 17-19, 2020 were analyzed. Results reveal that this heavy rainfall event forms a zonal main rain belt in the lower reaches of the Yangtze River, with an orientation similar to the main stream of the Yangtze River. The main rain belt shows a southwest-northeast orientation in the middle reaches of the Yangtze River. Correspondingly, the atmospheric circulation in middle and upper troposphere shows an abnormal spatial structure that is a V-shape pattern with two ridges and one trough over the Eurasian region. The atmospheric circulation pattern consists of a strong eastward-extending South Asian high at the 100 hPa level, a quasi-barotropic structure in the middle and upper troposphere at the middle and high latitudes, and a baroclinic structure in the middle troposphere. The strong vapor transport stably maintains along the northwest frank of the subtropical high. Particularly, the upper westerly jet shows a zonally pattern on July 17-18, 2020, with a subtropical high covering over the South China and a strengthened low-level southwest jet; the upper westerly jet transformed into a V-shaped structure, and the Jiang-huai cyclone formed on the July 19. The middle and lower reaches of the Yangtze River located on the south side of the upper westerly jet entrance and the northwest side of the subtropical high and the low-level jet. The "pumping" effects occurred in the upper troposphere owing to the atmospheric circulation structure of the V-shaped structure and overlapped with the uplifting activity in the lower troposphere, which is conducive to generating strong ascending motions and torrential rainfall. The position and shape of upper and lower jets and the subtropical high play an important role in determining the location, spatial distribution and intensity of heavy precipitation. The strong differences in pseudo-equivalent potential temperature between 500 and 850 hPa levels, the strong upward motions and the high potential vorticity values provided favorable thermodynamic and dynamic conditions for this Meiyu rainstorm event, in which thermal factors dominantly controlled the ascending motion and the vertical transport of the potential vorticity and the non-adiabatic heating term with the pressure are conducive to the enhancement of the potential vorticity according to the ω and potential vorticity tendency equations. The strong differences in pseudo-equivalent potential temperature between 500 and 850 hPa levels is a good significance indication for early prediction.

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何春楊,杜銀,謝志清.2020年7月一場梅雨暴雨的異?？臻g分布及形成機(jī)制.氣象科學(xué),2024,44(3):512-526 HE Chunyang, DU Yin, XIE Zhiqing. Abnormal precipitation pattern of a Meiyu rainstorm event and its dynamical and thermodynamically mechanism in July, 2020. Journal of the Meteorological Sciences,2024,44(3):512-526

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收稿日期:2022-08-25
最后修改日期:2022-11-15
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在線發(fā)布日期: 2024-07-16
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