ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 48 Issue 7 > 2022,48(7):801-812. DOI:10.7519/j.issn.1000-0526.2021.101201 Prev Next
Mesoscale Characteristics of a Local Severe Convective Rainstorm at the Eastern Foot of Helan Mountains
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Abstract:
The mesoscale characteristics of a local short-time severe convective rainstorm that occurred at the eastern foot of Helan Mountains in Ningxia in August 2019 are analyzed based on the data from Himawari-8 satellite, C-band Doppler radar, ERA5 hourly reanalysis, automatic weather station and conventional observation data. The results show that the southerly jet at 700 hPa, which was formed 6 h before the rainstorm and strengthened at night, contributed to the high temperature, the high humidity, the enhancement of atmospheric instability and the dynamic and thermal uplift mechanisms in the lower layers of the rainstorm area. It also helped mesoscale ground convergence line to trigger the meso-β scale convective system in the eastern slope of Helan Mountains and strengthen it into meso-α scale convective system, leading to the generation and development of the severe convective rainstorm eventually. The rainstorm occurred in the front-left of jet axis at 700 hPa, the high humidity area with water vapor flux ≥6 g·cm-1·s-1·hPa-1 at 700 hPa and specific humidity ≥12 g·kg-1 at 850 hPa, the high energy area with convective available potential energy (CAPE) ≥1 〖KG-*5〗500 J·kg-1, the high temperature area with θse ≥346 K at 850 hPa, the vertical upwarding area with central intensity ≤-1.2 Pa·s-1 at 800 hPa, and the front of cold cloud where the large gradient (G) of radiation brightness temperature (TBB) occurred. During the heaviest rainfall period, the jet axis was closest to the rainstorm area, the TBB ≤-66℃, G ≥27℃·km-1, the radar echo intensity (Z) ≥65 dBz, the echo heights (H) ≥10 km, the vertical integrated liquid water (VIL) ≥11 kg·m-2, and the area of the cold cloud below -52℃ was about 1/5 of mesoscale convective complex. The lower the TBB, the large the G, the higher the cooling rate and the more the hourly precipitation. The minimum TBB, the maximum G, the leap of Z and VIL, and the increase of echo height appeared 10-20 min earlier than the maximum rainfall, and the mesoscale ground convergence line appeared 30 min earlier than the rainfall.
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