Page 157 - 《高原气象》2022年第5期

高 原 气 象 41 卷
1250

Diagnosis of Different Definitions Potential Vorticity in an Extreme

Rainstorm in the Western Sichuan Basin

1，2
GUO Yunyun ，KANG Lan ，DENG Liantang ，ZHOU Yi ，WANG Chenxi 5
3，4
1，2
1，2
（1. Sichuan Meteorological Observatory，Chengdu 610072，Sichuan，China；
2. Heavy Rain and Drought-Flood Disasters in Plateau and Basin Key Laboratory of Sichuan Province，Chengdu 610072，Sichuan，China；
3. National Meteorological Center，Beijing 100081，China；
4. Numerical Weather Prediction Center Of China Meteorological Administration，Beijing 100081，China；
5. Sichuan Meteorological Disasters Prevention Technology Center，Chengdu 610072，Sichuan，China）

Abstract：The data of NCEP reanalysis（1°×1°），national ground automatic stations，radiosonde and Sichuan
encrypted automatic stations were used to diagnose the three definitions potential temperature and potential vor‐
ticity in an extreme rainstorm which occurred in the western Sichuan Basin during August 15-18，2020. The re‐
sults indicate that：Rainfall occurs in the‘high east and low west’circulation in the 500 hPa，the low-level shear
line and vortex are the favorable dynamic conditions. There is an obvious pseudo-equivalent potential tempera‐
ture and generalized potential temperature（θ ）gradient in the heavy rain area，but potential temperature is not.
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Potential vorticity（PV）anomaly area corresponds well to the precipitation area near 500 hPa and 800 hPa. In the
mid-low troposphere，the overlapping area of the negative vertical component（MPV）and horizontal component
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（MPV）of moist potential vorticity，and negative MPV in lower level，positive in higher level are warning areas
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1
of the storm. Meanwhile，the rainfall center is close to the negative and positive junction area of MPV ，and the
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rainstorm was mainly affected by convective instability in the low troposphere. The generalized moist potential
vorticity（GMPV）abnormal disturbance area in 800~600 hPa can be used as the rainstorm warning area，and its
positively correlated with the change of low-level water vapor. The space-time distribution of three definitions po‐
tential vorticity and precipitation have a good correspondence in a single station，and the precipitation intensity is
positively correlated with the disturbance intensity. The indicated height of PV，MPV and GMPV is 650~550
*
hPa，600~500 hPa and 800 hPa. Three definitions potential temperature has obvious difference，which theθ can
best reflect the high-water vapor of rainstorm.
Key words：Potential temperature；potential vorticity；relative humidity；extreme rainstorm