Instability Indices as Predictors of Atmospheric Lightning - Moldova Region Study Case

Abstract

Large scale convective systems represent in the warm season the main contributors to the water resources on the ground, following intense episodes of showers and torrential rains. South-East Europe represents one of the regions with the highest annual spatial frequency of atmospheric lightning at continental level. Atmospheric lightning could be considered the main atmospheric phenomenon triggered by high atmospheric instability. The degree of atmospheric instability is properly assessed using a wide range of indexes. The most reliable source of data for instability indices is derived from the radio sounding observations. In this study, aiming to cover the region of Moldova, we analyzed radiosonde data from Bucharest (Romania) and Odessa (Ukraine). CAPE, SWEAT, LI, KI, TTI were used as instability indices. Lightning data were used from the free database available for contributors to the Blitzortung network observations, developed in the last decennia. In our study each day is ordered taking to account the degree of instability as reflected from the 2 radio sounding stations and for the 5 available indexes. Lightning frequency maps for the territory of Moldova were produced, those being compared to the monthly mean frequency maps which were realized as well. Specific features of the link between instability indices and lightning frequency are underlined. The study points out on the spatial representativity of instability indices derived from radio sounding stations as predictor for the general instability of the region. The results could be used to improve the weather forecast in the warm/convective season.

Keywords: atmospheric lightning, lightning density, instability indexes, Moldova region, instability season

JEL Classification: A00