Analysis of 3 years of precipitation measurements from the Micro Rain Radar located at the Geophysical Institute

Abstract

An analysis of three years of vertically pointing Micro Rain Radar (MRR) data from the measurement platform at the Geophysical Institute has been performed. The measurement period started at 13.04.2010 and ended at 12.04.2013. The main motivation was to investigate the performance of the MRR in comparison to the rain gauge measurements by MET Norway and to investigate the validity of the Z-R relationships published in literature for the situation in Bergen. A comparison of the MRR and gauge raw data showed an annual overestimation by the MRR of 17% composed by a distinct overestimation of precipitation by the MRR in the cold season and an underestimation in the warm season. Based on 3 hour precipitation amounts separated by the air temperature at Florida, the largest overestimation by a factor 2-2.5 was found for temperatures between 0-3 grader celsius. At this temperature interval the melting layer with its increased reflectivity is likely to be located in the range bin for rain rate determination. For temperatures above 6 grader celsius an underestimation of 25-30% occurs more or less independently of temperature. The a-and b-values in the Z-R relationship showed a large variability, not only on a seasonal and synoptic scale, but also from hour to hour. For the overall three year period the a-values vary between 0 and 1000 and the b-values vary mainly between 0 and 2. The overall mean and median values of a and b can not fully confirm the reported values in the literature. The a-values are generally in the mid-range of the published ones, but the b-values are on average distinctly lower.