Verification of an algorithm (DWSR 2500C) for hail detection



The aim of this paper is to determine the real-time forecast and warning critera for hail events, using height of maximum reflectivity (Hmax), vertically integrated liquid water (VIL), hail occurrence probability (HailP) and reflectivity radar products (PPIZ). In addition, criteria were sought for use in estimating the size of hail stones. The study is based on data supplied by the Bucharest C-band weather radar along with observation data during the 2001-2008 period. The following radar products: HailP, Hmax, (PPIZ) and VIL, have been determined for each hail event reported by the weather station. A number of 320 cases have been analyzed when hail was determined for 20 weather stations in Muntenia area, Romania. One related result is that in situations when the 0 ºC isotherm is between 3000 and 4000 m, the frequency of hail events certified on the ground is 50%. Another conclusion is that if the maximum reflectivity appears at heights between 7000 and 8000 m, there is an approximately 20% chance of hail events. The HailP, Hmax, Reflectivity and VIL were computed both for the exact locations where hail was reported and for an area of 5 km around those locations. The performed analysis showed that both obtained data sets can be used with confidence. A comparison was performed regarding the year 2008 between the values of HailP from the Bucharest vertical sounding and those extracted from the Aladin model, using its requested parameters. The results show an overestimate of the hail occurrence probability (HailP) when the Aladin model was used.


hail; size of hail; radar products; C-band weather radar; Aladin model

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