伊犁河谷春季极端暴雨水汽特征与不稳定机制分析

doi:10.11755/j.issn.1006-7639(2024)-03-0395

摘要/Abstract

摘要：

2022年5月4—6日，新疆伊犁河谷出现极端暴雨天气，多站降水量突破历史极值。使用地面自动站逐时降水资料、美国国家环境预报中心/美国国家大气研究中心（National Centers for Environmental Prediction/National Center for Atmospheric Research，NCEP/NCAR）1°×1°再分析资料，分析此次极端暴雨事件的水汽特征和不稳定机制。结果表明：1）在500 hPa中纬度短波和低层辐合切变环流背景下，伊犁河谷可能发生极端暴雨天气，向西开口的“喇叭口”地形特征导致地形辐合和强迫抬升，增强了局地暴雨发生的动力触发机制。2）水汽主要来源于地中海、红海及里咸海地区，存在偏西和西南两条主要输送路径。低层偏西路径水汽输送强度大于中高层的西南路径，西边界为主要水汽输入边界，水汽输入贡献比约为85%，且从地面至700 hPa的强水汽辐合有利于水汽快速积聚。3）降水前对流层低层存在对流不稳定为暴雨天气积聚不稳定能量，对强降水的发生起重要作用；降水期间，对流层低层受对流不稳定影响，而对流层中高层受条件对称不稳定影响，这两种不稳定机制共同作用造成此次极端暴雨事件的发生。

关键词: 极端暴雨, 水汽输送, 水汽收支, 不稳定机制, 伊犁河谷

Abstract:

From May 4 to 6, 2022, an extreme rainstorm event appeared in the Yili River Valley of Xinjiang, recording historical maximum precipitation values at many stations. Using hourly precipitation data of automatic ground stations and the NCEP/NCAR 1°×1° reanalysis data, the paper analyzed the water vapor characteristics and instability mechanisms of this extreme rainstorm event. The results are as follows: 1) Under the background of a mid-latitude shortwave at 500 hPa and low-level convergent shear circulation, extreme rainstorms may occur in the Yili River Valley. The westward-opening “horn mouth”terrain feature leads to topographic convergence and forced ascent, enhancing the dynamic trigger mechanism for local rainstorms. 2) Water vapor mainly originates from the Mediterranean, Red Sea and Caspian Sea, with two main transport pathways in the west and southwest. The intensity of water vapor transportation along the low-level westward pathway is stronger than that of the mid-to-upper-level southwestern pathway. The western boundary serves as the main water vapor input boundary, contributing approximately 85% of the total water vapor input. Strong water vapor convergence from the surface to 700 hPa facilitates rapid water vapor accumulation. 3) Before precipitation, convective instability in the lower troposphere accumulated unstable energy, playing a crucial role in the occurrence of the heavy rainfall. During precipitation, the lower troposphere was affected by convective instability, while the middle and upper troposphere were affected by conditional symmetric instability. The combined effects of these two instability mechanisms led to this extreme rainstorm event.

Key words: extreme rainstorm, water vapor transportation, water vapor budget, mechanisms of instability, the Yili River Valley

中图分类号:

P458.1+21.1

魏娟娟, 万瑜, 潘宁, 肖俊安. 伊犁河谷春季极端暴雨水汽特征与不稳定机制分析[J]. 干旱气象, 2024, 42(3): 395-404.

WEI Juanjuan, WAN Yu, PAN Ning, XIAO Junʼan. Analysis of water vapor characteristics and unstable mechanism of extreme rainstorm in spring in Yili River Valley[J]. Journal of Arid Meteorology, 2024, 42(3): 395-404.

图/表 7

图1 2022年5月4日20:00—6日20:00降水等级实况（a，彩色圆点；灰色填充区为地形高度，单位：m）及5日11:00—6日11:00暴雨代表站逐小时降水量（b）

Fig.1 Precipitation level from 20:00 on May 4 to 20:00 on May 6, 2022 (a, color dot; the gray filled area is topographic height, Unit: m), hourly precipitation at the representative stations with heavy rain from 11:00 on May 5 to 11:00 on May 6, 2022 (b)

图2 2022年5月5日14:00 500 hPa位势高度场（等值线，单位：dagpm）和风场（风矢，单位：m·s-1）（a）、850 hPa风场（风矢，单位：m·s-1）和地形抬升速度（等值线，单位：Pa·s-1）（b）及5日20:00沿44°N的散度（等值线，单位：10-5 s-1）、涡度平流（填色，单位：10-9 s-2）、风场（风矢，单位：m·s-1）（c）与垂直速度（填色，单位：Pa·s-1）和流场（流线）（d）的剖面（灰色填充区为地形）

Fig.2 The 500 hPa geopotential height field (isolines, Unit: dagpm), wind field (wind vectors, Unit: m·s-1) (a) and 850 hPa wind field (wind vectors, Unit: m·s-1), terrain uplift velocity (isolines, Unit: Pa·s-1) (b) at 14:00 on May 5, 2022, the cross sections of divergence (isolines, Unit:10-5 s-1), vorticity advection (the color shaded, Unit: 10-9 s-2), wind field (wind vectors, Unit: m·s-1) (c) and vertical velocity (the color shaded, Unit: Pa·s-1), flow field (streamlines) (d) at 20:00 on May 5, 2022 along 44°N (The gray filled area is terrain)

图3 2022年5月5日08:00 1 000~300 hPa整层水汽通量（填色，单位：kg·m-1·s-1）和风场（风矢，单位：m·s-1）（a）及3—6日伊宁站水汽通量（填色，单位：g·cm-1·hPa-1·s-1）与水汽通量散度（等值线，单位：10-5 g·cm-2·hPa-1·s-1）（b）

Fig.3 The water vapor flux from 1 000 to 300 hPa throughout the layer (the color shaded, Unit: kg·m-1·s-1), wind field (wind vectors, Unit: m·s-1) at 08:00 on May 5, 2022 (a), water vapor flux (the color shaded, Unit: g·cm-1·hPa-1·s-1), water vapor flux divergence (isolines, Unit: 10-5 g·cm-2·hPa-1·s-1) at Yining Station from May 3 to 6, 2022 (b)

图4 2022年5月3—7日伊犁河谷整层水汽收支（a）和整层西、东、南、北边界水汽输送量（b）

Fig.4 Water vapor budget of the entire layer (a), the transport volume of the western, eastern, southern and northern boundaries of the entire layer (b) over the Yili River Valley from May 3 to 7, 2022

图5 2022年5月3—7日伊犁河谷西（a）、东（b）、南（c）、北（d）边界不同层次水汽输送量

Fig.5 Water vapor transport at different levels at the western (a), eastern (b), southern (c) and northern (d) boundaries of the Yili River Valley from May 3 to 7, 2022

图6 2022年5月4日20:00（a）、5日20:00（b）沿44°N的温度平流（填色，单位：10-5 K·s-1）、假相当位温（等值线，单位：K）及风场（风矢，单位：m·s-1）剖面与3—6日伊宁站温度平流（填色，单位：10-5 K·s-1）、假相当位温（等值线，单位：K）及风场（风矢量，单位：m·s-1）（c）（灰色填充区为地形）

Fig.6 The cross sections of temperature advection (the color shaded, Unit: 10-5 K·s-1), potential pseudo-equivalent temperature (isolines, Unit: K), wind field (wind vectors, Unit: m·s-1) along the 44°N at 20:00 on May 4 (a) and 20:00 on May 5, 2022 (b), temperature advection (the color shaded, Unit: 10-5 K·s-1), potential pseudo-equivalent temperature (isolines, Unit: K) and wind field (wind vectors, Unit: m·s-1) at Yining Station from May 3 to 6, 2022 (c) (The gray filled area is terrain)

图7 2022年5月4日20:00（a）、5日20:00（b）MPV（填色）、MPV1（黑色等值线）、MPV2（红色等值线）沿44°N的垂直分布及3—6日伊宁站MPV（填色）、MPV1（黑色等值线）、MPV2（红色等值线）变化（c）（单位：10-7 km2·s-1·kg-1）（灰色填充区为地形）

Fig.7 Vertical distribution of MPV (the color shaded), MPV1 (black isolines), MPV2 (red isolines) along 44°N at 20:00 on May 4 (a) and May 5 (b), 2022 and variation of MPV (the color shaded), MPV1 (black isolines), MPV2 (red isolines) at Yining Station from May 3 to 6, 2022 (c) (Unit: 10-7 km2·s-1·kg-1) (The gray filled area is terrain)

参考文献 20

[1]	曾勇, 杨莲梅, 2018. 新疆西部一次极端暴雨事件的成因分析[J]. 高原气象, 37(5): 1 220-1 232.
[2]	曾勇, 杨莲梅, 2020. 新疆西部“6.16”强降水过程的中尺度分析[J]. 暴雨灾害, 39(1): 41-51.
[3]	曾勇, 周玉淑, 杨莲梅, 2019. 新疆西部一次大暴雨形成机理的数值模拟初步分析[J]. 大气科学, 43(2): 372-388.
[4]	陈颖, 马禹, 2021. 新疆不同等级暴雨洪涝灾害的时空变化特征[J]. 干旱区地理, 44(6): 1 515-1 524.
[5]	冯瑶, 阿依先木·尼牙孜, 热依拉·玉努斯, 2021. 新疆哈密“7·31”极端大暴雨过程成因分析[J]. 干旱气象, 39(3): 426-435.
[6]	胡素琴, 希热娜依·铁里瓦尔地, 李娜, 等, 2022. 南疆西部干旱区两次极端暴雨过程对比分析[J]. 大气科学, 46(5): 1 177-1 197.
[7]	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.
[8]	李海燕, 2014. 天山山区暴雨过程的多尺度综合分析及动力诊断[D]. 兰州: 兰州大学.
[9]	刘晶, 周雅蔓, 杨莲梅, 等, 2019. 伊犁河谷“7.31”极端暴雨过程不稳定性及其触发机制研究[J]. 大气科学, 43(6): 1 204-1 218.
[10]	刘晶, 刘兆旭, 张晋茹, 等, 2022. 东天山哈密地区典型暴雨事件对流触发机制对比分析[J]. 大气科学, 46(4): 965-988.
[11]	吕新生, 周雅蔓, 余行杰, 等, 2021. 1961—2019年新疆暴雨山洪灾害损失的时空变化特征[J]. 沙漠与绿洲气象, 15(4): 42-49.
[12]	王妮, 崔彩霞, 刘艳, 2020. 新疆暴雨洪涝灾害损失的时空特征及其影响因素[J]. 干旱区研究, 37(2): 325-330.
[13]	吴国雄, 蔡雅萍, 唐晓菁, 1995. 湿位涡和倾斜涡度发展[J]. 气象学报, 53(4): 387-405.
[14]	肖开提·多莱特, 2005. 新疆降水量级标准的划分[J]. 新疆气象, 28(3): 7-8.
[15]	杨霞, 周鸿奎, 赵逸舟, 等, 2021. 新疆夏季暴雨精细化特征分析[J]. 气象, 47(12): 1 501-1 511.
[16]	姚秀萍, 肖峰, 马嘉理, 2023. 新疆地区夏季降水研究进展与展望[J]. 沙漠与绿洲气象, 17(1): 1-9.
[17]	张云惠, 于碧馨, 王智楷, 等, 2018. 伊犁河谷夏季两次极端暴雨过程的动力机制与水汽输送特征[J]. 暴雨灾害, 37(5): 435-444.
[18]	朱乾根, 林锦瑞, 寿绍文, 等, 2000. 天气学原理和方法[M]. 北京: 气象出版社.
[19]	庄晓翠, 李博渊, 秦榕, 等, 2020. 新疆东部一次区域极端暴雨环境场特征[J]. 高原气象, 39(5): 947-959. DOI
[20]	庄晓翠, 李博渊, 赵江伟, 等, 2022. 天山南坡暖季暴雨过程的水汽来源及输送特征[J]. 干旱气象, 40(1): 30-40. DOI