Interannual and Seasonal Variability of Lightning Flash Density and Related Meteorological Parameters over Sri Lanka (2003–2014)

Abstract

This study primarily examines the annual and seasonal variations in lightning flash density and associated meteorological parameters from 2003 to 2014. The trends in lightning flash density are analyzed in relation to meteorological variables such as aerosol optical depth (AOD), relative humidity (Rh), effective cloud droplet size (CDZ), Ångström exponent, and wind patterns. The study focuses on Sri Lanka, covering the region between 5.5°–10.0°N latitude and 79.0°–82.0°E longitude. Additionally, the study explores the complex relationship between lightning activity and AOD. The findings reveal that lightning occurred on 710 days, accounting for approximately one-fifth of the total study period. When AOD values were between 0.6 and 0.7, the maximum lightning flash density (2.92 × 10⁻⁴ flashes/km²/day) was recorded. Both lightning and AOD and cloud droplet size and lightning flash rate density were found to be negatively correlated. Furthermore, variations in relative humidity were found to influence lightning activity, with relative humidity increasing as AOD increased, and vice versa. These results underscore the significance of aerosol concentration in modulating relative humidity, which in turn affects lightning intensity.