NCEP再分析资料与江西强对流探空资料对比检验分析

Comparative Study on NCEP Data and Sounding Data of Strong Convective Processes in Jiangxi

选取2000—2016年江西省南昌、赣州两站及其附近半径为50km范围内的强对流天气过程个例,对比分析常规探空资料和NCEP再分析资料提取的温、湿、风垂直廓线及其输出量,检验NCEP再分析资料在江西省强对流天气分析的适用性。结果表明:1)NCEP再分析资料与探空资料温度差异非常小,500hPa高度层以下露点误差也在1℃以内,而500hPa高度层以上随着高度增加误差也明显的增大。基于温湿计算的大气能量物理量CAPE值可靠性较低,而基于中低层温湿条件计算的K指数和Δt850-500参考性较高。2)NCEP再分析资料与探空资料的垂直风速切变基本在1m/s之内,越往高层垂直风切变越小,差值在0.4m/s以下。两种资料计算的高低层风垂直切变均拟合的非常好。3)NCEP再分析资料显示低层偏干而中层略偏湿,低层偏干使CAPE偏小,中层偏湿不利于产生雷暴大风、冰雹等强对流天气,降低了灾害性强对流天气产生的概率。边界层风场预报偏弱也会弱化强对流辐合触发的条件的分析。总体来说,两种资料的基本物理量以及一些输出量偏差较小,可用于江西省强对流天气的分析。

Based on the strong convection processes occurred within 50 km around Nanchang and Ganzhou in Jiangxi province from 2000 to 2016, the profiles of temperature, humidity and wind extracted from conventional sounding data and NCEP reanalysis data were comparatively analyzed, and the applicability of NCEP reanalysis data for the analysis of strong convection in Jiangxi was also discussed. The results showed that: 1) The temperature difference between NCEP reanalysis data and sounding data was very small, and the dew point error below 500 hPa was less than 1 ℃, but the error above 500 hPa increased with height. The atmospheric energy physical quantity CAPE value calculated based on temperature and humidity calculation presented relatively low reliability, while the K index and Δ t 850-500 calculated based on the middle and low temperature and humidity conditions showed higher accuracy. 2) The wind speed difference between the NCEP reanalysis data and the sounding data was smaller than 1 m/s, and the difference decreased with the increase of layer level, which was below 0.4 m/s. The vertical shear of the high and low winds calculated by both data fitted very well. 3) The NCEP reanalysis data showed that the lower layer was relatively dry and the middle layer was slightly wet, which produced the relatively small CAPE value , and was bad for the generation of thunderstorms, hail and other strong convective weather, reduced the probability of severe convective weather. The poorer forecast of wind field in the boundary layer would also weaken the analysis of the conditions for strong convection convergence triggering. In the whole, the differences of basic physical characteristics and outputs between NCEP reanalysis data and sounding data were small, which can be used to the analysis of strong convective processes in Jiangxi.