Diagnosis of the Mesoscale Vortex Development Mechanism in a Heavy Rain Event
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摘要: 中尺度涡旋可以持续激发新对流，是造成局地持续性降水的重要系统。基于经典涡度方程的诊断无法描述热力信息对于涡旋发展的贡献。本文采用Boussinesq近似对涡度方程进行整理，将方程唯一强迫项定义为垂直速度位涡，其形式与位涡类似，利用垂直速度替换位温。进一步在垂直速度位涡倾向方程中，以气压水平梯度的形式引入热力过程的间接作用，定量描述动热力配置的贡献。以2021年6月15日发生在南疆的一次极端暴雨为例，利用高分辨率数值模拟资料，初步分析了低层动热力强迫作用向垂直涡度的传递。结果表明，垂直速度位涡的局地变化主要来自热力强迫项中低层垂直风切变与低层冷池的耦合作用，两者在降水区前侧产生大范围的正值区。该区域与垂直速度位涡的正值区重叠，促进垂直速度位涡的增长，进而维持降水前缘的正涡度，有利于产生较强的上升运动，触发新对流并造成持续性降水。Abstract: Mesoscale vortex usually stimulates local convection, which is an important system for persistent precipitation. The solution to the classical vorticity equation cannot directly describe and quantify the contribution of thermodynamic information to the development of vortices. In this study, the Boussinesq approximation is adopted to rewrite the vorticity equation, and the only forcing term employed is the vertical velocity potential vorticity. The form of this forcing term is similar to that of potential vorticity; however, vertical velocity is used instead of the potential temperature. Furthermore, the indirect effect of the thermodynamic process is introduced in the form of the horizontal pressure gradient to quantitatively describe the contribution of the dynamic and thermodynamic configurations to the vertical velocity potential vorticity equation. A heavy rain event, which occurred in southern Xinjiang on June 15, 2021, was selected as a case to analyze the transfer of low-level thermodynamic forcing to vertical vorticity using high-resolution numerical simulation data. The results showed that the local variation of the vertical velocity potential vorticity mainly originates from the coupling effect of the low-level vertical wind shear and low-level cold pool in the thermodynamic term, which contributed to a wide region of positive values ahead of the rainband. This pattern promotes the growth of vertical velocity potential vorticity in the corresponding region. The distribution and tendency of vertical velocity potential vorticity help maintain the positive vorticity ahead of the rainband, thereby making it conducive to the generation of strong ascending motion and new convection, directly leading to continuous precipitation.
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图 1 模式区域设置，阴影区表示湖泊或者海洋
Figure 1. Computational domain used in WRF simulation. Shaded areas indicate lakes or oceans
图 2 2021年6月15日00:00（协调世界时，下同）至16日00:00（a）观测和（b）模拟的24 h累计降水量（单位：mm）分布
Figure 2. Distribution of 24-h cumulative precipitation (units: mm) of (a) observation and (b) simulation from June 15 to June 16, 2021
图 3 2021年6月15日（a）04:00、（b）04:40、（c）05:20、（d）06:00、（e）06:40、（f）07:20、（g）08:00、（h）08:40和（i）09:20模拟的1.5 km高度风场（单位：m s−1）和组合反射率水平分布（单位：dBZ）
Figure 3. Simulated composite radar reflectivity (color shaded, units: dBZ) and wind field at 1.5 km (units: m s−1) at (a) 0400 UTC, (b) 0440 UTC, (c) 0520 UTC, (d) 0600 UTC, (e) 0640 UTC, (f) 0720 UTC, (g) 0800 UTC, (h) 0840 UTC, and (i) 0920 UTC 15 June 2021
图 4 2021年6月15日（a、b）05:00、（c、d）06:00和（e、f）08:00模拟的1.5 km高度垂直涡度（左列，填色，单位：10−3 s−1）和水平散度（右列，填色，单位：10−3 s−1）并叠加风场（风矢量，单位：m s−1）和20分钟累计降水量（等值线，单位：mm）的水平分布
Figure 4. Horizontal distributions of vertical vorticity (left column, shaded, units: s−1) and horizontal divergence (right, shaded, units: s−1) superposed with wind field (vectors, units: m s−1) and 20-min cumulative precipitation (contour lines, units: mm) at 1.5 km at (a, b) 0500 UTC, (c, d) 0600 UTC, and (e, f) 0800 UTC on June 15, 2021
图 5 2021年6月15日（a）05:00和（b）08:00模拟的1.5 km高度垂直速度位涡（填色，单位：10−6 s−2）叠加水平风场（风矢量，单位：m s−1）和20分钟累计降水（等值线，单位：mm）的水平分布
Figure 5. Horizontal distributions of vertical velocity potential vorticity (shaded, units: 10−6 s−2) superposed with wind field (vectors, units: m s−1) and 20-min cumulative precipitation (contour lines, units: mm) at 1.5 km at (a) 0500 UTC and (b) 0800 UTC on June 15, 2021
图 6 2021年6月15日05:00（左列）和08:00（右列）模拟的1.5 km高度垂直速度位涡强迫项（单位：10−8 s−3）叠加水平风场（风矢量，单位：m s−1）的水平分布：（a、b）平流项；（c、d）动力强迫项；（e、f）热力强迫项
Figure 6. Horizontal distribution of vertical velocity potential vorticity term (units: 10−8 s−3) superposed with wind field (vectors, units: m s−1) at 1.5 km at 0500 UTC (left column) and 0800 UTC (right column) on June 15, 2021: (a, b) Advective term; (c, d) dynamic term; (e, f) thermodynamic term
图 7 同图6但为（a、b）热力强迫项G1及其分量（c、d）G11和（e、f）G12
Figure 7. Same as Fig. 6, but for (a, b) the thermodynamic term G1 and its components (c, d) G11 and (e, f) G12
图 8 2021年6月15日05:00沿79.35°E（a）垂直涡度（单位：10−3 s−1）、（b）垂直速度（单位：m s−1）、（c）垂直速度位涡（单位：10−6 s−2），和（d）热力强迫项G1（单位：10−8 s−3）的经向—垂直分布。其中绿色实线表示20分钟累计降水量（单位：mm），黑色阴影表示地形（单位：km）
Figure 8. Meridional cross sections of (a) vertical vorticity (units: 10−3 s−1), (b) vertical velocity (units: m s−1), (c) vertical velocity potential vorticity (units: 10−6 s−2), and (d) thermodynamic term G1 (units: 10−8 s−3) along 79.35°E at 0500 UTC on June 15, 2021. The green line denotes precipitation in 20 min (units: mm) and the black shading denotes terrain (units: km)
图 9 2021年6月15日05:00沿79.35°E的（a）热力强迫项分量G11（单位：10−8 s−3）、（b）热力强迫项分量G12（单位：10−8 s−3）、（c）经向速度（单位：m s−1）、（d）纬向速度（单位：m s−1）、（e）纬向气压梯度（单位：10−3 Pa m−1）和（f）经向气压梯度（单位：10−3 Pa m−1）的垂直剖面。其中绿色实线表示20分钟累计降水量（单位：mm），黑色阴影表示地形（单位：km）
Figure 9. Meridional cross sections of (a) thermodynamic term component G11 (units: 10−8 s−3), (b) thermodynamic term component G12 (units: 10−8 s−3), (c) meridional wind component (units: m s−1), (d) zonal wind component (units: m s−1), (e) zonal pressure gradient (units: 10−3 Pa m−1), and (f) meridional pressure gradient (units: 10−3 Pa m−1) along 79.35°E at 0500 UTC on June 15, 2021. The green line denotes precipitation in 20 min (unit: mm) and the black shading denotes terrain (units: km)
图 10 2021年6月15日05:00模拟的1.5 km高度（a）温度（单位：K）和（b）气压（单位：hPa）叠加水平风场（风矢量，单位：m s−1）和20分钟累计降水量（等值线，单位：mm）的水平分布
Figure 10. Horizontal distributions of (a) temperature (shaded, units: K) and (b) pressure (shaded, units: hPa) superposed with wind field (vectors, units: m s−1) and 20-min cumulative precipitation (contour lines, units: mm) at 1.5 km at 0500 UTC on June 15, 2021
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[1] Chen S S, Frank W M. 1993. A numerical study of the genesis of extratropical convective mesovortices. Part I: Evolution and dynamics [J]. J. Atmos. Sci., 50(15): 2401−2426. doi:10.1175/1520-0469(1993)050<2401:ANSOTG>2.0.CO;2 [2] Chen M, Zheng Y G. 2004. Vorticity budget investigation of a simulated long-lived mesoscale vortex in South China [J]. Adv. Atmos. Sci., 21(6): 928−940. doi: 10.1007/BF02915595 [3] Li N, Ran L N, Gao S T. 2020. On the interactions of vorticity, divergence and deformation in a meso-α-scale vortex [J]. Meteorol Atmos Phys, 132(2): 203−223. doi: 10.1007/s00703-019-00674-9 [4] 陈明轩, 王迎春. 2012. 低层垂直风切变和冷池相互作用影响华北地区一次飑线过程发展维持的数值模拟 [J]. 气象学报, 70(3): 371−386. doi: 10.11676/qxxb2012.033Chen Mingxuan, Wang Yingchun. 2012. Numerical simulation study of interactional effects of the low-level vertical wind shear with the cold pool on a squall line evolution in North China [J]. Acta Meteorologica Sinica (in Chinese), 70(3): 371−386. doi: 10.11676/qxxb2012.033 [5] Davis C A, Galarneau T J Jr. 2009. The vertical structure of mesoscale convective vortices [J]. J. Atmos. Sci., 66(3): 686−704. doi: 10.1175/2008JAS2819.1 [6] Galarneau T J Jr, Bosart L F, Davis C A, et al. 2009. Baroclinic transition of a long-lived mesoscale convective vortex [J]. Mon. Wea. Rev., 137(2): 562−584. doi: 10.1175/2008MWR2651.1 [7] 窦慧敏, 丁治英, 沈新勇, 等. 2019. 东北冷涡下一次飑线和MCV的形成与水平涡度的关系 [J]. 热带气象学报, 35(5): 709−720. doi: 10.16032/j.issn.1004-4965.2019.064Dou Huimin, Ding Zhiying, Shen Xinyong, et al. 2019. The relationship between the formation of a squall line and MCV and the horizontal vorticity under cold vortex in Northeast China [J]. Journal of Tropical Meteorology (in Chinese), 35(5): 709−720. doi: 10.16032/j.issn.1004-4965.2019.064 [8] 高守亭, 周玉淑. 2019. 近年来中尺度涡动力学研究进展 [J]. 暴雨灾害, 38(5): 431−439. doi: 10.3969/j.issn.1004-9045.2019.05.005Gao Shouting, Zhou Yushu. 2019. Progress in dynamics of mesoscale vortex in recent years [J]. Torrential Rain and Disasters (in Chinese), 38(5): 431−439. doi: 10.3969/j.issn.1004-9045.2019.05.005 [9] 黄文娟. 2017. 江淮梅雨锋上典型中尺度对流涡旋诊断与模拟[D]. 华东师范大学硕士学位论文, 48ppHuang Wenjuan. 2017. Diagnosis and simulation of a typical mesoscale convective vortex over the Meiyu front [D]. M. S. thesis (in Chinese), East China Normal University, 48pp. [10] 黄昕, 周玉淑, 冉令坤, 等. 2021. 一次新疆伊犁河谷特大暴雨过程的环境场及不稳定条件分析 [J]. 大气科学, 45(1): 148−164. doi: 10.3878/j.issn.1006-9895.1912.19219Huang Xin, Zhou Yushu, Ran Lingkun, et al. 2021. Analysis of the environmental field and unstable conditions on a rainstorm event in the Ili valley of Xinjiang [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 45(1): 148−164. doi: 10.3878/j.issn.1006-9895.1912.19219 [11] 焦宝峰. 2021. 台风“彩虹”(2015)近海及登陆过程中能量演变特征和转化机制分析[D]. 南京信息工程大学博士学位论文, 141ppJiao Baofeng. 2021. Analysis of energy evolution characteristics and transformation mechanism of typhoon Mujigae (2015) offshore and during landfall [D]. Ph. D. dissertation (in Chinese), Nanjing University of Information Science & Technology, 141pp. doi: 10.27248/d.cnki.gnjqc.2021.000029 [12] 乔娜. 2019. 两种尺度低涡背景下MCS中β尺度强对流带的成因分析[D]. 南京信息工程大学硕士学位论文, 60ppQiao Na. 2019. The reason of the meso-β scale severe convection in MCS under two scales of vortexes [D]. M. S. thesis (in Chinese), Nanjing University of Information Science & Technology, 60pp. doi: 10.27248/d.cnki.gnjqc.2019.000245 [13] 冉令坤, 李娜, 崔晓鹏. 2014. 登陆台风莫拉克(2009)的涡度拟能收支分析 [J]. 气象学报, 72(6): 1118−1134. doi: 10.11676/qxxb2014.088Ran Lingkun, Li Na, Cui Xiaopeng. 2014. Analysis of the budget of enstrophy during the landing of typhoon Morakot (2009) [J]. Acta Meteorologica Sinica (in Chinese), 72(6): 1118−1134. doi: 10.11676/qxxb2014.088 [14] 冉令坤, 李书文, 周玉淑, 等. 2021. 2021年河南“7.20”极端暴雨动、热力和水汽特征观测分析 [J]. 大气科学, 45(6): 1366–1383. Ran Lingkun, Li Shuwen, Zhou Yushu, et al. 2021. Observational analysis of the dynamic, thermal, and water vapor characteristics of the “7.20” extreme rainstorm event in Henan Province, 2021 [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 45(6): 1366−1383. doi: 10.3878/j.issn.1006-9895.2109.21160 [15] 沈新勇, 张弛, 肖云清, 等. 2020. 一次东北冷涡背景下MCS过程多尺度能量相互作用研究 [J]. 大气科学学报, 43(3): 447−457. doi: 10.13878/j.cnki.dqkxxb.20191109001Shen Xinyong, Zhang Chi, Xiao Yunqing, et al. 2020. Multi-scale energy interaction study in the MCS process under a Northeast cold vortex [J]. Transactions of Atmospheric Sciences (in Chinese), 43(3): 447−457. doi: 10.13878/j.cnki.dqkxxb.20191109001 [16] 孙晓蕾, 闵锦忠, 王仕奇, 等. 2020. 中尺度对流系统的动热力特征及其演变对风垂直切变的响应 [J]. 热带气象学报, 36(3): 401−415. doi: 10.16032/j.issn.1004-4965.2020.038Sun Xiaolei, Min Jinzhong, Wang Shiqi, et al. 2020. Dynamic and thermodynamic characteristics of mesoscale convective system and the impact of its evolution on vertical wind shear [J]. Journal of Tropical Meteorology (in Chinese), 36(3): 401−415. doi: 10.16032/j.issn.1004-4965.2020.038 [17] 唐滢. 2019. 江推地区暖季γ-中尺度涡旋的统计特征研究[D]. 南京大学硕士学位论文, 83ppTang Ying. 2019. Characteristics of meso-γ-scale vortices in the warm season over the Yangtze and Huai River basin [D]. M. S. thesis (in Chinese), Nanjing University, 83pp. [18] 王金鑫, 潘益农, 束宇, 等. 2014. 中尺度对流涡旋(MCV)近30a来的研究进展 [J]. 气象科学, 34(3): 343−354. doi: 10.3969/2013jms.0003Wang Jinxin, Pan Yinong, Shu Yu, et al. 2014. Advance in research on MCV in recent thirty years [J]. Journal of the Meteorological Sciences (in Chinese), 34(3): 343−354. doi: 10.3969/2013jms.0003 [19] 吴国雄. 2001. 全型涡度方程和经典涡度方程比较 [J]. 气象学报, 59(4): 385−392. doi: 10.3321/j.issn:0577-6619.2001.04.001Wu Guoxiong. 2001. Comparison between the complete-form vorticity equation and the traditional vorticity equation [J]. Acta Meteorologica Sinica (in Chinese), 59(4): 385−392. doi: 10.3321/j.issn:0577-6619.2001.04.001 [20] 徐双柱, 陈静静, 王青霞. 2018. 南岳山、庐山高山站风场对长江流域梅雨锋暴雨的指示作用 [J]. 暴雨灾害, 37(3): 213−218. doi: 10.3969/j.issn.1004-9045.2018.03.003Xu Shuangzhu, Chen Jingjing, Wang Qingxia. 2018. The indicative effect of the wind field at the Mount Nanyue and Mount Lu stations on the plum rain front rainstorm in the Yangtze River basin [J]. Torrential Rain and Disasters (in Chinese), 37(3): 213−218. doi: 10.3969/j.issn.1004-9045.2018.03.003 [21] 周昆, 潘益农, 王东勇, 等. 2007. 大别山区地形对春季冷锋附近中尺度对流系统影响的数值模拟研究 [J]. 南京大学学报(自然科学), 43(5): 535−543.Zhou Kun, Pan Yinong, Wang Dongyong, et al. 2007. Numerical simulations of the orographic effects of the Dabie mountains on the mesoscale convective system of a spring cold front [J]. Journal of Nanjing University (Natural Science) (in Chinese), 43(5): 535−543. [22] 周括, 冉令坤, 蔡仁, 等. 2022. 地形追随垂直运动方程在南疆极端暴雨中的诊断分析 [J]. 大气科学, 已录用. Zhou Kuo, Ran Lingkun, Cai Ren, et al. 2022. Diagnostic analysis of terrain following vertical motion equation in southern Xinjiang extreme rainstorm [J]. Chinese Journal of Atmospheric Sciences (in Chinese), in press. doi: 10.3878/j.issn.1006-9895.2201.21194 -
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