复杂山地环境下雷暴天气中的地基微波辐射计影响距离分析

ANALYSIS OF EFFECTIVE DETECTION DISTANCE OF GROUND-BASED MICROWAVE RADIOMETER IN THUNDERSTORM WEATHER IN COMPLEX MOUNTAINOUS TERRAINS

关键词:  微波辐射计  K指数  雷暴  影响距离  山地

Key words:  tropical storm density  Subseasonal to Seasonal  debiased Brier skill score

摘要:

利用2017年2月—2018年10月地基微波辐射计和无线电探空仪、闪电和雷达数据，首先评估了微波辐射计温度和绝对湿度在不同高度的探测性能，微波辐射计和无线电探空仪不同高度的温度的相关系数为0.800~0.985，绝对湿度的相关系数为0.600~0.916；微波辐射计温度的标准差为3.9~6.1 ℃，绝对湿度的标准差为0~4 g/m3，无线电探空仪温度的标准差为4.2~6.1 ℃，绝对湿度的标准差为0.1~4.2 g/m3；微波辐射计和无线电探空仪温度绝对误差的标准差为1.06~2.90 ℃，绝对湿度绝对误差的标准差为0.08~2.02 g/m3。二者K指数相关系数为0.945。其次利用K指数上升和下降到35 ℃的时次和不同距离闪电开始和结束时次做相关性分析，结果表明在30 km处具有最大的相关系数(0.864)，这可能就是微波辐射计温度和湿度在复杂山地下雷暴天气中能够代表的大气层结的有效距离。最后统计分析了微波辐射计K指数上升达35 ℃时，90%上游移向微波辐射计的雷暴回波(30 dBZ雷达回波超过-15 ℃高度层)距离微波辐射计平均距离为35.3 km，移到微波辐射计附近平均需要92.8分钟，局地雷暴(40 km以内)生成需要138.2分钟。

Abstract:

To assess the potential of tropical storm forecasting on Subseasonal to Seasonal (S2S) timescales, the forecast skill of tropical storm is evaluated using S2S Prediction Project Database. The evaluation period is from May 1 to Oct 31 during 1999—2010. To evaluate the forecast skill of tropical storm on S2S timescales, tropical storm density, defined as the probability of tropical storm occurrence within 500 km, is used to describe the generation and movement of tropical storms. Tropical storm density is computed from the ensemble forecasts from six operational centers including BoM, CMA, ECMWF, JMA, CNRM and NCEP. The debiased Brier skill score is used to compare the tropical storm density forecast skill of these models. The ECMWF model shows positive debiased Brier skill score when forecast lead time is from 11 to 30 days, indicating better tropical storm forecast than reference forecast based on climatology.