Diagnostic analysis of moist potential vorticity for two local rainstorm events on the eastern foot of Helan Mountain
XIAO Yunqing1,2, SHEN Xinyong3,4, ZHANG Xiaolu1,2, YANG Yuanyuan1,2, ZHANG Jianrong1,2, ZHANG Chi3, LI Xiaofan5
1. Key Laboratory for Meteorological Disaster Monitoring and Early Warning and Risk Management of Characteristic Agriculture in Arid Regions, CMA, Yinchuan 7500113;
2. Yinchuan Meteorological Administration, Yinchuan 750011;
3. Key Laboratory of Meteorological Disaster, Ministry of Education/Joint International Research Laboratory of Climate and Environment Change/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, Nanjing 210044;
4. Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai), Zhuhai 519082;
5. School of Earth Sciences, Zhejiang University, Hangzhou 310027
Based on the rainfall data from the automatic weather stations, the conventional data accessed by MICAPS4 and NCEP reanalysis data, we have conducted a comparative analysis of two local heavy rainstorm events on the eastern foot of Helan Mountain in Ningxia occurred respectively on 21 August 2016 and 22 July 2018 in terms of their precipitation characteristics, circulation background and other conditions, with focus on the diagnostic analysis of the moist potential vortex field in the two events. The results indicate that both events can be divided into two stages. In both cases, the first stage are warm-area precipitation, showing the feature such as small range, short time and high intensity. Comparing with the first stage, their second stage of precipitation present larger range and less rain intensity. The severe precipitation during the two events both occurred in the pseudo-equivalent potential temperature (θse) isoline areas, and both of them are distributed along the main axis of the low-level jet. The period of severe precipitation is consistent with the occurrence time of θse maximum. Rainstorm zones are basically located near the center of negative potential vortex (PV), and the trigger and development of rainstorm is consistent with the movement of the negative PV center, whose strengthening, weakening and moving direction can guide the prediction of local heavy rainstorm. The positive large value areas of barotropic term (MPV1) of moist potential vorticity above 500 hPa troposphere are corresponding with the negative large value areas of MPV1 below 700 hPa, and the vertical superposition of positive and negative MPV1 center area is conducive to the occurrence and development of rainstorm. It is found in the vertical section that there are negative extreme areas of baroclinic term (MPV2) of moist potential vorticity at 600 hPa in the two events. The intensity, duration and variation of negative MPV2 extreme areas in the lower and middle troposphere can be used as indicators for the prediction of local heavy rainstorm.
ZHANG Xiaolu, et al
.2020. Diagnostic analysis of moist potential vorticity for two local rainstorm events on the eastern foot of Helan Mountain[J].
Torrential Rain and Disasters, 39(2): 148-157.