气象   2020, Vol. 46 Issue (11): 1440-1449.  DOI: 10.7519/j.issn.1000-0526.2020.11.005

### 引用本文 [复制中英文]

[复制中文]
XU Haolin, ZHENG Jiafeng, JIANG Tao, et al, 2020. Analysis of Water Vapor Variation and Transformation During the Two Airport Thunderstorms in Urumqi and Chengdu[J]. Meteorological Monthly, 46(11): 1440-1449. DOI: 10.7519/j.issn.1000-0526.2020.11.005.
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### 文章历史

2019年10月15日收稿
2020年8月1日收修定稿

1. 成都信息工程大学大气科学学院，高原大气与环境四川省重点实验室，成都 610225
2. 中国气象局交通气象重点开放实验室，南京 210008
3. 黑龙江陆军预备役步兵师，牡丹江 157011
4. 兰州中心气象台，兰州 730020
5. 福建省气象局气象信息中心，福州 360001

Analysis of Water Vapor Variation and Transformation During the Two Airport Thunderstorms in Urumqi and Chengdu
XU Haolin1, ZHENG Jiafeng1,2, JIANG Tao3, LI Qian4, ZENG Zhengmao5, ZHANG Jie1, ZHU Keyun1
1. Plateau Atmosphere and Environment Key Laboratory of Sichuan Province, School of Atmospheric Sciences, Chengdu University of Information Technology, Chengdu 610225;
2. Key Laboratory of Transportation Meteorology of CMA, Nanjing 210008;
3. Infantry Division of Heilongjiang Army Reserve, Mudanjiang 157011;
4. Lanzhou Central Meteorological Centre, Lanzhou 730020;
5. Fujian Meteorological Information Centre, Fuzhou 360001
Abstract: The high-temporal-resolution water vapor density, integral water vapor content (V) and liquid water path (L) measured by ground-based microwave radiometer have important application potential and value in the prediction and research of severe convective precipitation. The paper uses these data to study the water vapor distribution, evolution and vapor-liquid conversion in different stages before and after the two thunderstorms that happened in Urumqi and Chengdu airports, respectively. During the July 4 thunderstorm in Urumqi, under the action of water vapor transport and vertical motion, the low-level water vapor density significantly increased before precipitation and recovered rapidly after precipitation. Before the July 15 thunderstorm precipitation in Chengdu, the whole-layer water vapor experienced the evolution process of increasing first and then decreasing. During the process of water vapor accumulation, the maximum increment was 4.99 g·m-3. During the process of water vapor conversion, the whole-layer water vapor decreased rapidly, of which the water vapor density decreased more significantly at the height of clouds. The cloud water vapor content (IWVc) inversion in the text is better than V and L in indicating the onset and end of precipitation. Before the Urumqi July 4 precipitation, IWVc increased by 1.8 times and 2.2 times, respectively. After the end of precipitation, IWVc decreased rapidly. Before the precipita-tion in Chengdu on July 15, IWVc increased by 1.3 times and 1.5 times, respectively. During the severe precipitation, the growth rate of water vapor in the cloud was lower than that of water vapor conversion. In addition, the increase or decrease of IWVc can also be good indicators for the precipitation intensity of the two thunderstorm processes. For the stable precipitation of the Urumqi July 4 thunderstorm, as the IWVc increased, the surface precipitation intensity increased. Moreover, the greater the increment of water vapor in clouds, the higher the surface precipitation intensity. In the period when the IWVc decreased, the precipitation amount was less than 0.01 mm. For the showery precipitation during the Chengdu July 15 thunderstorm, the accumulation of IWVc was ahead of the occurrence of surface precipitation. The more the IWVc accumulated, the severer the surface precipitation happened. After turning into stable precipitation, the relationship between IWVc and surface precipitation returned to the corresponding increase or decrease, and the decline of IWVc increment or decrement also indicated the weakening and end of the precipitation.
Key words: microwave radiometer    thunderstorm precipitation    liquid water    water vapor content in the cloud

1 资料与方法

 $V = \int_0^{{z_0}} {{\rho _{\rm{v}}}} \left(z \right){\rm{d}}z$ (1)
 $L = \int_0^{{z_0}} {{\rm{d}}{m_{\rm{L}}}}$ (2)

 $IWVc = \int_{CBH}^{CTH} {{\rho _{\rm{v}}}\left(z \right){\rm{d}}z}$ (3)

2 实况介绍

2018年7月4—5日，乌鲁木齐地窝堡机场发生一次在高空槽线影响下生成的雷暴降水过程。此次雷暴降水过程(以下简称为乌鲁木齐“7·4”雷暴过程)主要分为两个时段，22:25—22:35为第一降水时段，降水量为0.4 mm；23:52至次日01:35为第二降水时段，降水量为5.6 mm，该个例为地窝堡机场当年夏季雷暴降水过程中降水量最大的个例。2018年7月15—16日，成都双流机场在低空切变线影响下出现一次雷暴降水过程(以下简称为成都“7·15”雷暴过程)，此次降水也分为两时段，第一时段降水为22:56—23:42，降水量为0.2 mm，次日00:47—04:27为第二时段降水，降水量为35 mm。

3 两次雷暴过程的水汽分布和演变特征分析

 图 1 2018年7月4日20时至5日04时地窝堡机场(a)以及7月15日21时至16日06时成都双流机场(b)0~10 km的水汽密度垂直分布 (图中虚线划分了降水的两个时段) Fig. 1 Vertical distribution of 0-10 km water vapor density at Diwopu Airport from 20:00 BT 4 to 04:00 BT 5 July 2018 (a) and at Chengdu Shuangliu Airport from 21:00 BT 15 to 06:00 BT 16 July 2018 (b) (The dashed line divides the two periods of precipitation)

 图 2 乌鲁木齐“7·4”雷暴过程第一时段降水前(a)、第二时段降水前(b)水汽变化曲线 Fig. 2 Variation curves of water vapor before the first period of thunderstorm process (a) and before the second period of precipitation (b) during the July 4 thunderstorm in Urumqi

 图 3 成都“7·15”雷暴过程第二时段降水前15日(a)、16日(b)水汽变化曲线 Fig. 3 Variation curves of water vapor on the 15th (a) and 16th (b) before the precipitation during the second period of the July 15 thunderstorm in Chengdu

VL能反映测站上空0~10 km垂直柱内总体的水汽和液态水含量，由图 4可见，降水时VL总的变化趋势较为一致，都对应峰值。乌鲁木齐“7·4”雷暴过程如图 4a所示，第一时段降水发生前，VL在21:42—22:15迅速增长，分别达到峰值(36.1、1.3 kg·m-2)。第二时段降水发生在VL的峰值期，但在降水前，两值也有提前突增现象，V于降水前3 min开始增大，达45.5 kg·m-2时降水开始，L于降水前15 min显著增大，增长到2.7 kg·m-2时降水开始。降水期间，VL随着降水强度的变化，呈显著的双峰型增减变化，两值均在降水减弱后迅速减小。

 图 4 2018年7月4日21时至5日02时(a)及7月15日22时至16日05时(b)的V和L演变 Fig. 4 The evolution of V and L from 21:00 BT 4 to 02:00 BT 5 July 2018 (a) and from 22:00 BT 15 to 05:00 BT 16 July 2018 (b)

4 云中水汽演变特征和地面降水关系分析

 图 5 2018年7月4日21时至5日04时(a)及7月15日22时至16日05时(b)的IWVc演变 (图中虚线划分了降水的两个阶段) Fig. 5 The evolution of IWVc from 21:00 BT 4 to 04:00 BT 5 July 2018 (a) and from 22:00 BT 15 to 05:00 BT 16 July 2018 (b) (The dashed line divides the two stages of precipitation)

 图 6 2018年7月4日23:40至5日01:30(a)和2018年7月16日00—05时(b)辐射计传感器实时降水量、IWVc的10 min累积值演变 Fig. 6 Evolutions of radiometer sensor real-time precipitation and 10 min accumulation value of IWVc from 23:40 BT 4 to 01:30 BT 5 July 2018 (a) and from 00:00 BT to 05:00 BT 16 July 2018 (b)

5 结论

(1) 由于气候差异，乌鲁木齐地窝堡和成都双流机场水汽垂直分布存在明显差异，前者水汽分布在0~7 km，而后者水汽分布在0~9 km，且低空的水汽比前者高出6~8 g·m-3。乌鲁木齐“7·4”过程降水前，在水汽输送和垂直运动的作用下，低层0.1 km处水汽密度迅速达到10 g·m-3以上，降水后高低层水汽密度迅速恢复。成都“7·15”降水前，整层水汽经历了先增加后减小的演变过程，水汽积累过程中，水汽密度在0~4.3 km增长，最大增量达4.99 g·m-3；水汽转化过程中，整层水汽密度迅速减小，其中云层高度上(0.5、3.3 km)水汽密度的减小量达5.3 g·m-3，高于其他层次。

(2) 文中定义的云中水汽含量(IWVc)对不同强度降水起止的指示效果优于积分水汽含量V和积分液态水路径L。乌鲁木齐“7·4”过程降水前，IWVc分别增大1.8倍和2.2倍，降水结束后，IWVc迅速减小到20 kg·m-2以下；成都过程“7·15”降水前，IWVc分别增大1.3倍和1.5倍，降水结束后，IWVc的10 min变化量低于10 kg·m-2

(3) IWVc的增减与两地地面降水量指示效果较好。对两次过程的第二时段降水进行分析，乌鲁木齐“7·4”过程中，IWVc增加，地面降水强度随之增大，且IWVc增量越大，地面降水强度越大；IWVc减小时段，降水量很小，均低于0.01 mm。成都“7·15”过程中，降水前期，IWVc与地面降水呈反向变化，降水前IWVc累积的越多，之后地面降水越强；降水后期，IWVc的10 min变化量低于10 kg·m-2，此时IWVc和地面降水呈同增减的关系，预示了地面降水的减弱和结束。