江苏副高型强对流天气特征及环境参数分析

Analysis of Subtropical High Convective Weather Characteristics and Environmental Parameters in Jiangsu Province

副热带高压控制下的强对流天气常常漏报和错报。为了提高此类天气的预报准确率,利用2007—2016年常规地面和高空观测资料以及地面区域自动站资料,运用统计分析方法,对苏南地区56例副高型强对流的天气特征和环境参数特征进行分析。结果表明:副高型强对流主要有短时强降水、雷暴大风、冰雹雷暴大风和强降水混合型,其中混合型出现频率最高(66%),雨强在30~79.9 mm/h的短时强降水频率(68%)最高,雷暴大风的风力多为8~9级(61%);强对流触发时间峰值在12:00—14:00时。静力稳定度方面,850与500 hPa的温差ΔT 85和沙氏指数S I的中位值分别为25℃和-1℃左右,3种类型强对流的差异不大;混合型强对流的对流有效位能C APE的中位值(2510 J/kg),远大于短时强降水(1570 J/kg)和雷暴大风(1220 J/kg);而对流抑制有效位能C IN的中位值则是雷暴大风(160 J/kg)的最高。3种类型强对流低层水汽条件相似,1000 hPa露点T d的中位值均在25℃左右;水汽条件差异主要在中层,中层大气越干、露点垂直递减率越大,越利于雷暴大风的发生,反之,则利于短时强降水的发生,混合型强对流介于两者。K指数的中位值,雷暴大风(32℃)、混合型(34℃)到短时强降水(36℃)是逐渐增大的。自由对流高度L FC和抬升凝结高度T CL,雷暴大风的25%值分别为650、910 hPa,远小于短时强降水的900、970 hPa,混合型强对流则位于两者。差异明显的环境参数,对副高型强对流天气的分类预报有一定的指导意义。

Severe convective weather under subtropical high pressure often misses and wrong reports.In order to improve the forecasting accuracy of such weather,the conventional ground and upper air observation data and the ground area automatic weather stations data from 2007 to 2016 was used in the research.Based on statistical analysis method,56 cases of subtropical high in south Jiangsu strong convective weather characteristics and characteristics of environment parameters were analyzed.Several results were got from the research.The subtropical high convection mainly includes short-time strong precipitation,thunderstorm gale,hail thunderstorm gale and strong precipitation mixed type,among which mixed convection has the highest frequency(66%),the intensity of short-term heavy precipitation is mainly between 30 mm/h to 79.9 mm/h(68%),and the wind force scale of thunderstorm gale is mostly from 8 to 9(61%).The peak of strong convection trigger time is at 12:00 to 14:00.In terms of static stability,theΔT 85(temperature difference between 850 and 500 hPa)and S I index,where the median value is about 25℃and-1℃respectively,and there is little difference between the three types of strong convection.The median C APE value of mixed strong convection(2510 J/kg),which is much higher than the short-time heavy precipitation(1570 J/kg)and thunderstorm gale(1220 J/kg),while the median value of C IN value is the highest for thunderstorm gale(160 J/kg).The conditions of water vapor in the lower layer of the three types of strong convection are similar,and the median value of 1000 hPa dew point T d is around 25℃.The difference of water vapor condition is mainly reflected in the middle layer.The drier the middle layer atmosphere is,the higher the vertical decline rate of dew point is,which is more conducive to the occurrence of thunderstorm wind.On the contrary,it is conducive to the occurrence of short-term heavy precipitation,and the mixed strong convection is between them.The median value of K index,thunderstorm gale(32℃),mixed type(34℃)to short-term heavy precipitation(36℃)are gradually increasing.The 25-percentile values of L FC(level of free convection)and T CL(lifting condensation level)of thunderstorm wind are 650 hPa and 910 hPa,respectively,which are much smaller than 900 hPa and 970 hPa of short-time heavy precipitation,while mixed severe convection is between them.Significantly different environmental parameters are indicative of classified forecasts of subtropical high strong convective weather.