暴雨灾害 (Jun 2022)
Analysis of early warning of extreme downbursts induced by two supercell storms in the border area between Hebei and Henan Provinces
Abstract
A severe convective weather event that was caused by multiple supercell storms occurred in the border area between the Hebei and Henan provinces at 16-22 Beijing Time of 31 July 2021. The two of these supercell storms (hereinafter referred to as Handan supercell and Puyang supercell, respectively) with the longest life time affected successively southern Hebei and northern Henan, resulting in five extreme downbursts. Using the observational data from regional automatic weather stations and the Doppler weather radar data, we performed the analysis of the radar early warning effect of thunderstorm gale induced by these five extreme downbursts in the border area based on the radar echo early warning index of the downbursts induced by supercell storms. The main results are as follow: (1) The radar echo characteristics such as refectivity core height, middle altitude radial convergence, and radial velocity at the lowest elevation for the supercell storms in the five extreme downbursts all meet the criterias of early warning. On average, twelve echo features related to thunderstorm gale, of which the strength reach maximum before the strongest downbursts, appeared before each extreme downburst. Among these features, the ones related to convective storm downdraft and near-surface strong wind can be used as the warning signals 10-37 minutes in advance for the downbursts. (2) The refectivity factor core, mesocyclonecore, and mesocyclone bottom height were all decreased before the first extreme downburst induced by the two supercell storms, which may be used as the warning signals 19-22 minutes in advance, respectively. (3) The Handan supercell storm is a classic isolated supercell, while the Puyang supercell storm is embeded in multicells. The former has the clearer echo structure and is easier to be identified than the latter. The relevant echo features or characteristic quantities are also better be used for early warning of downburst. (4) One supercell storm can bring several extreme downbursts during its lifetime, so it is necessary to pay attention to the changes of relevant radar echo characteristics after its occurrence, especially in its dissipating stage.
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