用探空资料检验中尺度数值模式对强对流天气的诊断分析能力

提高对流天气临近预报准确率的关键问题之一是了解大气的垂直稳定度和垂直风切变。中尺度数值模式产品提供了高时空分辨率的大气稳定度和垂直风切变信息，需要首先检验其精度才能进一步考虑其在对流天气预报中的应用。利用北京加密探空资料检验北京市气象局3km分辨率的MM5模式结果，对强对流天气的背景参数包括温湿风垂直廓线、对流有效位能CAPE和垂直风切变进行模式分析和预报与探空对比检验。结果表明：模式模拟的各种大气廓线中，风廓线和温度廓线都具有一定的参考价值，与实况有较好的一致性，但在廓线出现转折的地方，如：逆温层和风向转折时，模式预报较差。露点（湿度）廓线的预报误差较大，不能反映出真实水汽场的分布。因此，模式预报的深层（地面至500hPa）垂直风切变与探空具有较好的一致性，而模式给出的对流有效位能CAPE由于露点预报结果不理想，其值与实际偏差较大。因此模式输出的对流有效位能CAPE必须经过适当订正才能用于诊断强对流天气发生的可能性。

Evaluation of Convective Parameters Derived from Mesoscale Numerical Model by Sounding Data

To improve the accuracy of convection weather forecast, one of the key issues is to find out the atmospheric vertical stability and wind shear. The mesoscale numerical model provides information on the atmospheric vertical stability and wind shear with high spatial and temporal resolution, and the reliability of the parameters derived from model output need to be well checked for the further application to the convection weather forecast. Using the radiosonde data of Beijing weather station, the convective parameters from mesoscale numerical model MM5 with a resolution of 3km run in Beijing Meteorological Bureau are carefully checked. The convective parameters are compared between the forecast results and the soundings. Results show that wind and temperature profiles produced by the model are useful to some extent,while when inversion or strong shift of wind direction occur, simulation results are much poorer. The forecast dew point profiles show very large errors, indicating the model gives a very poor water vapor distribution. The predicted deep layer vertical wind shear (from ground to 500hPa) shows good consistence with the radiosonde data, while the simulated CAPE is totally different from the observed value because of the errors in predicted temperature and dew point . The simulated CAPE value must be properly revised in order to diagnose the possible occurrence of the strong convective weather.