基于溃变理论的v-3θ图在陇东强对流天气中的应用

Application of v-3θ Diagram Based on Collapse Theory in Severe Convective Weather in the Eastern Gansu

[目的]验证v-3θ图在陇东地区强对流天气预报中的适用性。[方法]利用常规观测资料、灾情月报及上游平凉站的探空资料,对庆阳市2012-2018年172个强对流天气样本的v-3θ图特征进行分析,通过箱线图确定了湿度阈值,并对比不同类型强对流天气发生前v-3θ图与T-ln P图特征。[结果]v-3θ图对于陇东地区的对流性天气的指示意义较好;超低温、θ曲线有拐点及θsed和θ^*与T轴成钝角可作为强对流天气的起报条件;就滚流效应而言,冰雹天气过程最明显,对流性暴雨、阵性大风、干雷暴依次减弱;对流性暴雨及阵性大风发生前低层湿度条件好,但前者湿层伸展高度高;当起报条件满足时,首先利用低层θ^*-θsed判断对流天气类型:其数值≥10℃时,若滚流效应较为显著,则预报冰雹,否则为干雷暴;其数值≤3℃时,则需进一步分析湿层伸展的高度,位于700 hPa以下则预报阵性大风,否则为对流性暴雨;对流强度越弱时,v-3θ图相较于T-ln P图优势越突出。[结论]该研究为提高该地区的强对流天气预报准确率提供依据。

[Objective]The research aimed to verify the applicability of v-3θdiagram in severe convective weather prediction in the eastern Gansu.[Method]Using conventional observation data,disaster monthly report and sounding data of upstream Pingliang station,the v-3θdiagram characteristics of 172 severe convective weather samples from 2012 to 2018 in Qingyang City were analyzed.The humidity threshold is determined by the box plot and the characteristics of the v-3θand T-ln P maps before the occurrence of different types of severe convective weather are compared.[Result]The v-3θdiagram was a good indicator of convective weather in the eastern Gansu;cryogenic,inflection point on theθcurve andθsed andθ^*parallel obtuse angles to the T axis could be used as initial conditions for severe convective weather;in terms of rolling effect,hail weather process was the most obvious,convective rainstorm,gusty wind,dry thunderstorm weakened successively;before the occurrence of convective rainstorm and gusty wind,low level humidity condition was well,but the former wet layer extends higher;when reporting conditions were met,firstly,use the lower stageθsed-θ^*to determine the type of convective weather:when the value is greater than or equal to 10℃,if the rolling effect was more significant,hail was predicted;otherwise,it was a dry thunderstorm;When its value was less than or equal to 3℃,the height of wet layer extension needs to be further analyzed.If it was below 700 hPa,gusty wind was predicted;otherwise,it was a convective rainstorm;When the convective intensity was weaker,the advantage of v-3θdiagram over T-ln P diagram was more prominent.[Conclusion]This study provides a basis for improving the accuracy of strong convective weather forecasting in the region.