Relationship Between Convective Storm Properties and Lightning Over the Western Ghats

Abstract

X-band radar observations are integrated with lightning location network observations to investigate the relationship between convective storm properties and lightning over the Western Ghats during a monsoon season (June–September 2014). Convective storms (cells) were identified using an objective-tracking method and instantaneous lightning strikes within the radar domain were then linked with observed storms. This spatio-temporal sampling of individual convective cells and lightning has facilitated process-based study of electrified convection over the Ghats for the first time. Storm and lightning occurrences are typically high during monsoon onset and withdrawal months of June and September, respectively. A spatial correspondence between deep-intense storms, lightning, and intense convective cores indicated presence of large hydrometeors in the mixed-phase region of storm supported by strong updrafts and is essential for lightning. The large-scale instability that peaked during afternoon hours was a key factor in the formation of deep-intense storms and lightning. Results show that majority of lightning-producing storms are located on the leeward side as opposed to the windward side. These storms have deeper top-heights, larger areas and vertically integrated liquid, and an enhanced hail probability than those devoid of lightning. Warm season convection in the study area is accompanied by the preponderance of negative Cloud to Ground (−CG) flashes over positive Cloud to Ground (+CG) lightning. Storms with +CG features exhibited much higher (>2 times) vertical airmass flux in the mid-troposphere (6–9 km) than storms without +CG features. Furthermore, for majority of +CG storms, intracloud flash occurrences increased significantly above the freezing level.