Ukrainian Hydrometeorological Research Institute, Kyiv - Ukraine
In this paper we presented analysis of satellite derived parameters of heavy precipitated clouds over Ukraine in cold and warm period. We have used AVHRR(HRPT) images of NOAA satellites for retrieving of cloud parameters and Meteosat images for tracking of cloud systems. Cloud analysis algorithm consist of two steps: cloud detection and cloud analysis.
On the first step the observed radiance values were partitioned into those representing clear scenes and those representing cloudy scenes. We used statistical thresholds techniques for distinguishing the image on cloud and non-cloud pixels and cluster analysis of two dimensional histogram for distinguishing of cloud pixels belonging to different cloud types.
The second step involves in the quantitative determination of cloud properties from measured radiances. We used radiation transfer models to obtain cloud top temperature and height, liquid water content (LWC) and phase composition of mixed clouds. Analysis of obtained parameters show that in warm period of year heavy precipitated clouds (severe storms) have cloud top temperature low than -45 °C, cloud top heights up to 11 km and LWC greater than 0.8 kg/m2. Reflectivity in visible channels not exceed 65% because on the top of cloud there are many ice nonspherical particles, which effected on this value. In a cold period of year heavy precipitated clouds have cloud top temperature low than -30 °C, cloud top heights up to 4.5 km and LWCC greater than 0.4 kg/m2.
Obtained cloud parameters will be used in the warning information system of heavy precipitation and severe storms over Ukraine.