Statistical characterization of cloud-to-ground lightning data and meteorological modelling of cloud-to-ground lightning days for the warm season in the province of León (northwest Spain)

Abstract

This study presents the characteristics of cloud-to-ground lightning in the province of León (Spain), based on data collected via the lightning detection network of the Spanish Meteorological Agency. A total of 146 081 flashes and 279 220 strokes were recorded between 2000 and 2010. Spatial analysis (total, negative and positive flash density, and mean peak currents of positive and negative flashes) was performed at a resolution of 1 km. The maximum density recorded for total negative and positive flashes was 2.0 flashes km−2 year−1; 2.3 for negative flashes only and 0.178 for positive flashes. There was a different spatial distribution for positive compared with negative flashes, resulting from meteorological mechanisms involved with their polarities. The density distribution corresponding to both total and negative flashes appears to be clearly associated with topography. Interestingly, there is a clear inverse spatial correlation between the density and peak current parameters, which has important implications for constructing risk maps of lightning activity. This correlation has been quantified and confirmed for both positive and negative flashes by two separate regression equations. In the second part of the present study, a statistical model was constructed to predict lightning in the province of León, using a quadratic discriminant function that encompasses three meteorological variables obtained from National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis: lifted index, K-index and precipitable water. To construct the model, data were used from May to September over 2002–2007, and then applied to an independent sample of years from 2008 to 2010. Results were verified using skill scores probability of detection, false alarm rate, critical success index and true skill statistic. Scores obtained for the samples were 0.79, 0.45, 0.48 and 0.53 (respectively) for model construction, and 0.78, 0.14, 0.69 and 0.65 (respectively) for application to the independent sample.