engleski

Analysis of lightning activity during thunderstorms with the overshooting tops

Thunderstorms’ updraft area, frequently manifested by the appearance of the overshooting tops (OT), is linked to the electric activity of the storm, in a way that updraft surges coincide with an increase in flash rate. Analysis of lightning activity in the thunderstorms with OTs was done for the warm part of the year (May - September) during 2009 and 2010, over the region from approximately 41°N 8°E to 49.5°N 24°E. Deep convective clouds with OTs were detected from the Meteosat 9 SEVIRI data, using method based on the infrared window (IRW, 10.8 μm) channel and the absorption channels of water vapor (WV, 6.2 μm) and ozone (O3, 9.7 μm) in form of brightness temperature differences. Locations and times of the detected OTs were compared to the distribution and types of the lightning strokes, provided by LINET Lightning Location System. The results show that spatial distribution of lightning activity coincides well with the spatial distribution of the detected OTs. The largest numbers of lightning strokes, as well as OTs were detected in the western Hungary, southeastern Germany, northern Adriatic and southern Adriatic coastal region at the slopes of the Dinaric Alps. In general, the largest number of OTs occur between 14 and 21 UTC, while from 06 to 10 UTC OT detections are rather rare. Lightning activity shows similar temporal distribution. Sharp increase in lightning activity and larger values of the electric current are evident at the time of the OT detections. At that times, lightnings occur well above the tropopause, being clearly related to the OT parts of the Cumulonimbus cloud.

convection; lightning; overshooting tops; SEVIRI brightness temperature differences

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