Optimal radii for data of the World Wide Lightning Location Network sampling in climatology of thunderstorm activity.

To study the climatology of thunderstorm activity (TA) in the south of the Russian Far East according to data of 34 weather stations and data of the World Wide Lightning Location Network (WWLLN) for 2009–2018, the optimal radii of the circular area of the WWLLN data sample centered at each station were obtained. The optimal radii, at which the correspondence between data of thunderstorm observations and lightning detections at weather stations is maximum, were estimated by two statistical methods based on the calculation of the Threat Score and the difference of days with TA. Taking into account the previously published results, the values of the optimal radii vary from 5 to 39 km and, on average, in the south of the Russian Far East are 23 km. Differences in the estimates of radii for the mainland, coastal, and island (Sakhalin) stations were noted, the average values for which were 25 km, 23 km, and 19.5 km, respectively, as well as for nighttime and daytime. In the south of the Far East as a whole and at the mainland and coastal stations separately, the "nighttime" optimal radii are on average larger than the "daytime" ones, on Sakhalin—on the contrary. The values of optimal radii obtained by two methods were used to estimate the average annual number of lightning WWLLN days for each weather station, which were compared with the average annual number of thunderstorm days based on human observations. It was found that the difference between them at all stations was within ±6 days/year and up to 1.3 days/year, the root mean square deviations were 2.4 days/year and 0.4 days/year for the first and second methods, respectively. It is shown that the WWLLN data reflect the main features of the intra-annual TA variation according to weather station data, and also make it possible to identify individual thunderstorms during TA variation at a diurnal scale, including those not noted in the reports of weather stations, and mesoscale structures formed by cumulus clouds in the spatial distribution of lightning. [ABSTRACT FROM AUTHOR]