Spatial distribution of lightning associated with low-shear thunderstorm environments in the central Appalachian region.

Differential heating, the preferential warming of terrain by insolation based on its gradient and aspect, has been observed to play an instrumental role in thunderstorm formation in weak flow regimes. In this study, spatiotemporal cluster analysis was used to group total lightning observations into likely thunderstorms, which were then categorized into lightning-defined (LD) storm modes. Flashes associated with the 351 LD single-cell storms identified were then imported into a geographic information system to compare their frequency against the presence of east- and south-facing surfaces with above-average gradients, termed "enhanced diurnal heating surfaces"(EDHSs). The influence of EDHSs on LD single-cell total lightning and storm frequency was examined via a series of pooled t-tests at eight different spatial scales. The results indicate that EDHSs possessed a significantly greater frequency of LD single-cell storms, 37.6% greater than non-EDHSs, with the relationship best observed at a 15-km resolution. The analysis was then repeated but with terrain aspect ignored. The elimination of aspect as an EDHS requirement removed all statistical significance from the initial results, suggesting that aspect is indeed a key contributor to single-cell thunderstorm formation within areas of complex terrain. [ABSTRACT FROM AUTHOR]