A Year-Long Total Lightning Forecast over Italy with a Dynamic Lightning Scheme and WRF

Abstract

Lightning is an important threat to life and properties and its forecast is important for several applications. In this paper, we show the performance of the “dynamic lightning scheme” for next-day total strokes forecast. The predictions were compared against strokes recorded by a ground observational network for a forecast period spanning one year. Specifically, a total of 162 case studies were selected between 1 March 2020 and 28 February 2021, characterized by at least 3000 observed strokes over Italy. The events span a broad range of lightning intensity from about 3000 to 600,000 strokes in one day: 69 cases occurred in summer, 46 in fall, 18 in winter, and 29 in spring. The meteorological driver was the Weather Research and Forecasting (WRF) model (version 4.1) and we focused on the next-day forecast. Strokes were simulated by adding three extra variables to WRF, namely, the potential energies for positive and negative cloud to ground flashes and intracloud strokes. Each potential energy is advected by WRF, it is built by the electrification processes occurring into the cloud, and it is dissipated by lightning. Observed strokes were remapped onto the WRF model grid with a 3 km horizontal resolution for comparison with the strokes forecast. Results are discussed for the whole year and for different seasons. Moreover, statistics are presented for the land and the sea. In general, the results of this study show that lightning forecast with the dynamic lightning scheme and WRF model was successful for Italy; nevertheless, a careful inspection of forecast performance is necessary for tuning the scheme. This tuning is dependent on the season. A numerical experiment changing the microphysics scheme used in WRF shows the sensitivity of the results according to the choice of the microphysics scheme.

Performance of Lightning Potential Index, Lightning Threat Index, and the Product of CAPE and Precipitation in the WRF Model

“…(2022) and Federico et al. (2022). Table 2 summarizes the model configurations and physical parameterizations, the selection of which is based on previous studies (e.g., Gharaylou et al., 2019; Yair et al., 2010).…”

“…The first 12 hr of each simulation are considered the spin-up time, which is consistent with recent similar studies conducted by Guo et al (2022) and Federico et al (2022). Table 2 summarizes the model configurations and physical parameterizations, the selection of which is based on previous studies (e.g., Gharaylou et al, 2019;Yair et al, 2010).…”

Study of the Intense Meteorological Event Occurred in September 2022 over the Marche Region with WRF Model: Impact of Lightning Data Assimilation on Rainfall and Lightning Prediction

“…The total lightning, i.e., the sum of positive, negative, and intracloud lightning, is considered for comparison with observations. Federico et al [43] showed an extensive application of the Lynn et al [44] lightning scheme to the central Mediterranean area (162 cases). Among their results, a considerable sensitivity of the number of lightning strikes predicted by the scheme to the parameterised current was shown, and, for a resolution of 3 km, the configuration with a parametrised current of 0.75 × 10 −4 A was found to be the best setting.…”

“…For lightning forecast verification, we upscaled the model output from 2 km to 24 km, following the procedure discussed in [43]. In particular, we considered 12 grid cells in both horizontal directions, and we remapped both observed and predicted strokes onto this grid, verifying the results on a 24 * 24 km 2 grid.…”

“…Recently, Federico et al [43] showed a successful experiment with lightning forecasting over the Central Mediterranean without performing LDA. In previous studies over the United States, Lynn et al [44][45][46] showed the capability of LDA to improve the lightning forecast.…”