Gaoyuan qixiang (Jun 2024)

Application Analysis on the Characteristics of Doppler Radar V-shaped gap in Hail Forecasting and Warning

  • Laping LI,
  • Shuhua YANG,
  • Jieli LIU,
  • Qi ZHAO,
  • Xiaoqiang LI,
  • Jiayuan WANG

DOI
https://doi.org/10.7522/j.issn.1000-0534.2024.00008
Journal volume & issue
Vol. 43, no. 3
pp. 749 – 761

Abstract

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Using the basic data from four C-band Doppler weather radars and ground observation data in Shanxi province， the statistical analysis of the V-shaped gap features observed in Shanxi from 2009 to 2017 was conducted.The correspondence between V-shaped gap observed by Doppler radar and hailfall was investigated， and the forecasting and warning indicators for hail using V-shaped gap features were summarized.Real-time operational applications were carried out from 2018 to 2022 to validate and refine forecasting and warning indicators of the V-shaped gap.The results indicate that hailfall begins after the appearance of V-shaped gap and ends before their disappearance.There is no significant correlation between the probability of hailfall and the initial height of V-shaped gap.When the corresponding updraft height of V-shaped gap is ≤4 km， hailfall does not occur.The ideal observation elevation angle for V-shaped gap ranges from 2.4°to 6.0°， with 2.4°being the optimal angle.The strongest phase of hailfall is characterized by a "butterfly-shaped" intense echo region.The predictive indicators and focal points during the initial stage of hail forecasting and early warning include： （1） the presence of a weak or marginally weak echo region when a V-shaped gap appears； （2） a length of the V-shaped gap along the radial direction > 30 km， or an initial length of the V-shaped gap along the radial direction 50 dBZ and echo top > 10 km； （2） a slanted weak echo region corresponding to the V-shaped gap， with high-level divergence and low-level convergence characteristics in the average radial velocity field； （3） stable maintenance of the weak echo region or marginally weak echo region； （4） continuous occurrence of hail can be predicted when the V-shaped gap is observed at a 0.5° angle， and an increase in hail intensity can be foreseen when the strong echo region exhibits a "butterfly" shape； （5） When the maximum vertical liquid water content exceeds 22 kg·m-2， the vertical liquid water content jump increment exceeds 26 kg·m-2， and the vertical liquid water content density exceeds 3.6 g·m-3， the probability of hail is high.

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