雷电定位系统与人工观测雷暴日数统计比较

为了利用雷电定位系统 (lightning location system，LLS) 资料统计人工观测雷暴日数，采用湖北省2007—2012年LLS监测资料，选取25个气象站为圆心，统计其不同监测半径 (r) 圆区域内LLS监测的雷电日数，并与人工观测雷暴日数进行比较。结果表明:r≤7 km时，LLS监测平均年雷电日数小于人工观测平均年雷暴日数；r≥8 km时, LLS监测平均年雷电日数大于人工观测平均年雷暴日数；r=22 km圆区域内年平均雷电日数可替代最大年雷暴日数。根据r=7 km，r=8 km圆区域内LLS监测的年雷电日数、年平均地闪密度资料，分别采用直接替代法、地闪密度法和该文提出的二元法计算年雷暴日数，结果显示:二元法效果最好。二元法计算的2007—2012年25个站平均年雷暴日数与人工观测相等，平均差异为7.4%；二元法计算的2013年年雷暴日数与人工观测相差0.8 d，平均差异为12.3%。

Comparison of the Number of Thunderstorm Days from Lightning Location System and Artificial Observations

Using the lightning location system (LLS) monitoring data of Hubei Province from 2007 to 2012 and 1983-2012 artificial observations, 25 meteorological stations with theoretical detection efficiency above 95% are selected to make a relative analysis on the number of thunderstorm days monitored by LLS with different monitoring radius (r) and artificial observations. Results show that annual mean thunderstorm days of artificial observations and LLS monitoring data agree mostly in the radius which range from 6.4 km to 10.2 km. In the circular area when r=7, 8, 9 km, the difference is minimum, with the average difference of about 19%. When r≤7 km, the annual mean thunderstorm days from LLS monitoring data is less than that of artificial observation, while it is more than artificial observation when r≥8 km, and it can replace the number of maximum annual mean thunderstorm days of artificial observations when r=22 km. The ground flash density do not change significantly with the monitoring radius in the range of 2-40 km, the annual mean flash density is 3.9-4.1 times/(km2 ·a) and the average value is 4 times/(km2 ·a) for each monitoring radius. According to data of LLS, 3 methods are suggested to calculate the number of annual mean thunderstorm days of artificial observations. The first method is using the number of annual mean thunderstorm days of LLS monitoring data when r=7 km to represent the artificial observations directly, called direct substitution method. The second method is to calculate the number of annual mean thunderstorm days of artificial observations by the equation with one unknown quantity on the basis of the annual mean flash density data when r=8 km, called ground flash density method. The third method is using the binary equation to calculate the number of annual mean thunderstorm days of artificial observations on the basis of the number of annual mean thunderstorm days and the annual mean flash density data when r=8 km, called binary method. The examination shows that the binary method is the best, followed by the ground flash density method and the direct substitution method. The number of annual mean thunderstorm days of 25 stations calculated by binary method from 2007 to 2012 are equal to that of artificial observations, and the average difference is 7.4%. In 2013, the gap of the number of annual mean thunderstorm days between binary method and artificial observation is 0.8 d, and the average difference is 12.3%.