2020年8月11日至12日阿拉善地区暴雨螺旋度特征分析

Analysis of Helicity Characteristics of rainstorm in Alashan Area from August 11 to 12,2020

利用阿拉善地区地面观测资料和NCEP再分析资料分析2020年8月11日—12日阿拉善地区暴雨螺旋度特征,为今后短时强降水预报及其暴雨量级降水预报提供参考依据。分析结果:暴雨发生前,h_(p)中心值>310×10^(-6) Pa/s~2,h_(xy)强度为100×10^(-2) Pa/s~2,沿40.2°N作垂直螺旋度剖面图可见,700 h Pa在105°E正值中心增大至360×10^(-6) Pa/s~2,400 h Pa附近有负值中心,中心值为-30×10^(-6) Pa/s~2,低层辐合,高层辐散。从散度、垂直速度和相对湿度来看,最强辐合中心位于850 h Pa附近,散度中心值达-14×10^(-9) g/(cm~2·h Pa·s),500~650 h Pa为辐散区,最强上升速度出现在700 h Pa,垂直速度达-8 Pa/s,700 h Pa在104°E相对湿度达到100%。垂直螺旋度变化与强降水发生时段对应,垂直螺旋度正值中心和强度的增强时,降水区雨量也增大。

This paper used the surface observation data and NCEP reanalysis data in the Alashan area to analyze the vertical helicity of the rainstorm process that occurred in the Alashan area from August 11 to 12,2020,providing a reference for the short-term heavy precipitation forecast and the rainstorm magnitude precipitation forecast in the future.Analysis results:Before the rainstorm,the h_(p) center value was greater than 310 · 10~(-6) Pa/s~2,h_(xy) strength 100 · 10~(-2) Pa/s~2,as shown in the vertical helicity profile along 40.2■N,700 h Pa increases to 360 at the positive center of 105■E.There was a negative center near 10~(-6) Pa/s~2 400 h Pa,with a center value of-30·10~(-6) Pa/s~2,low-level convergence,high-level divergence.From the perspective of divergence,vertical velocity,and relative humidity,the strongest convergence center is located near 850 h Pa,with a divergence center value of-14×10~(-9) g/(cm~2·h Pa·s)-1 500~650 h Pa,with the strongest upward velocity occurring at 700 h Pa and a vertical velocity of~-8 Pa/s,700 h Pa,reaching 100% relative humidity at 104■E.The change in vertical helicity corresponds to the period of heavy precipitation,and when the center and intensity of the positive vertical helicity increase,the rainfall in the precipitation area also increases.