engleski

Satellite-based overshooting top detection methods and an analysis of correlated weather conditions

The paper addresses two topics: the possibilities of satellite-based automatic detection of overshooting convective cloud tops and the connection between the overshootings and the occurrence of severe weather on the ground. Because the use of visible images is restricted to daytime, four detection methods based on the Meteosat Second Generation SEVIRI 10.8 μm infra- red window channel and the absorption channels of water vapor (6.2 μm), ozone (9.7 μm) and carbon dioxide (13.4 μm) in form of brightness temperature differences were used. The theoretical background of all four methods is explained, and the detection results are compared with daytime High Resolution Visible (HRV) satellite images to validate each method. Of the four tested methods, the best performance is found for the combination of brightness temperature differences 6.2-10.8 and 9.7-10.8 μm, which are correlated to overshootings in HRV images in 80% of the cases. The second part of the research is focused on determining whether the appearance of the overshooting top, a manifestation of a very strong updraft in the cloud, can be connected to an abrupt change of certain weather elements on the ground. For all overshooting tops found by the above-mentioned combined method, automatic station data within the range of 0.1 and available hail observations within 0.2 were analyzed. The results show that the overshootings are connected to precipitation in 80% and to wind gusts in 70% of the cases ; in contrast, a slightly lower correlation was found for temperature and humidity changes. Hail is observed in the vicinity of the overshooting in 38% of the cases.

overshooting tops; MSG SEVIRI data; brightness temperature difference; severe weather

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