河北省南部强对流天气的时空分布及对流参数统计特征

Spatial and Temporal Distributions of Severe Convective Events and Statistical Characteristics of Convection Parameters over the Southern Part of Hebei Province

摘要: 利用河北南部石家庄、邢台、邯郸三个地区50个县(市)气象站1999~2008年10年的雷暴、大风、冰雹和暴雨等观测资料以及由MICAPS3探空资料导出的同期对流参数，对这一区域强对流天气事件的时空变化特征及相应对流参数的统计特征进行了分析总结。结果表明，1999~2008期间河北南部年平均雷暴日数为74.8 d，其中雷暴大风有28.2 d，冰雹有9.4 d，暴雨天气有12.3 d；10年中1、2和12月份均未出现强对流天气，雷暴和暴雨天气最多出现在7月份，而雷暴大风和冰雹天气则最多出现在6月份；一般而言，午后到傍晚为强对流天气的高发时段。研究区域西部的雷暴和冰雹天气明显多于东部，雷暴大风多见于中部的平原上，而西北和东南部则是暴雨的高发区。表征对流的参数中，热力能量类参数，如总指数TT、K指数、T850~500和对流有效位能CAPE等，总是在强对流天气出现的时候取值更大，但暴雨的T850~500取值却明显较小，表明垂直方向上温度的强梯度不是发生对流性暴雨的必要条件；表征强对流天气的动力参数——强天气威胁指数(SWEAT)在强对流事件中均表现为较高的数值，瑞士雷暴(SWISS)指数则相反，取值明显较低，进一步分析表明动力类对流参数可被用作强对流潜势预报的参考指标；表征层结稳定度的参数——沙氏指数较小(SI ≤ 1)、θse850~500较大(≥5)是强对流天气比较显著的特征；对流凝结高度(CCL)在雷暴、冰雹和暴雨事件中取值较低，在雷暴大风事件中则取值较高。不同月份强对流天气的对流参数对比，7月份的对流参数大多表现出强于其它月份的特征。

Abstract: Using the observational thunderstorm, thunderstorm gale, hail and rainstorm data at 50 meteorological sta-tions in Xingtai, Shijiazhuang, Handan Districts of Hebei Province, China, and the convection parameters drawn from the MICAPS3 system during 1999-2008, spatial and temporal distributions of the severe convective events and several convective parameters have been analyzed. It has been shown that, on average, there are 74.8 thunderstorm days in a year over South Hebei, including 28.2 thunderstorm gale days, 9.4 hail days, and 12.3 rainstorm days. Strong convec-tive weather does not appear in January, February and December. Most thunderstorm and heavy rain events appear in July, and most thunderstorm gale and hail appear in June. Strong convective weather usually occurs in the afternoon. Apparently, compared to the eastern part, more thunderstorm and hail events appear in the western region of the study area. Thunderstorm gales often appear in the central part, and the heavy rain events in the northwestern and southeastern parts. For the strong convective weather, the thermal and energy convection parameters, such as TT, K, T850~500 and CAPE, are all numerically higher. But the parameter of T850~500 for rainstorm is relatively small, indicating that the rain-storm occurrence is not caused by any strong vertical temperature variation. The dynamical parameter of the strong weather threaten index is always showing a larger value, but the Switzerland thunderstorm index always appears to be smaller, indicating those power parameters may be used as reference indexes to forecast strong convection potential. The small SI stability index (no larger than 1) and large θse850~500 (no less than 5) can always characterize the strong convection events. In addition, the convection-condensation height is lower, that is, the CCL value is larger for thunder-storm, hail and heavy rain events, but higher for thunderstorm gales. The heights where the temperature reaches 0 and −20 Degrees Celsius can be regarded as characterized heights for hail. The parameters show that convection seems to be stronger in July than in other months.