Rain events on 22 October 2006 in León (Spain): Drop size spectra

Abstract

This paper presents the physical characteristics of the precipitation of the rainiest day in 2006 in León, Spain. The aim is to analyze the situation of the atmosphere during a period of 24 h using different techniques (synoptic situation, satellite imagery, sounding balloons, and radar imagery) to determine the causes of this extreme precipitation event. The relationship between the atmospheric conditions and the characteristics of the precipitation (measured with a rain gauge and with a disdrometer) has also been studied. The precipitation was observed to be of the stratiform type during the whole day, except for two episodes of convective precipitation, which have been analyzed in greater detail. The analysis of the Z– R relation ( Z = 139.6 R 1.34) confirms the existence of a mixture of different types of precipitation during the day, and about half of the volume was of convective origin. The radar images were compared with precipitation data registered at surface level. The radar reflectivities have been found to coincide with the ones estimated by the disdrometer. In addition, the drop size distribution of the precipitation registered was studied in the case of the two convective events, and compared with the distribution during the rest of the day. Assuming an exponential distribution, the parameters of the distribution were calculated and it was found that the values were slightly lower in the two convective episodes ( λ = 2.22 and 2.73 mm − 1 ), which implies that the drops were larger during these episodes.