The Spatial and Temporal Variability of Rain Microphysics

This work examines the spatial and temporal variability of rain microphysics during the Iowa Flood Studies (IFloodS) NASA GPM Ground Validation field campaign that took place in eastern Iowa during the summer of 2013. During the field campaign a dense network of disdrometers was deployed in the field of view of the NASA S-Band NPOL radar, as well as the NASA Ku/Ka -Band D3R radar. Based upon the measured drop size distributions from the network of disdrometers over one month of data collection, we calculate the radar parameters reflectivity, differential reflectivity, and specific differential phase by using T-Matrix scattering simulations. This work will address three different, but related issues. We start by examining the variability of the sampling by comparing the scattered moments from the disdrometers with nearby radar observations. After showing that these measurements agree very well, we then look at the spatial variability by using pairwise correlations between disdrometer measurements and cross compare these with pairwise correlations between radar measurements. The behavior of these correlations as a function of distance gives us vital information about the spatial variability of the moments. Estimation of this variability for different storm types has direct bearing on the assumptions involved in algorithm development for the GPM retrieval algorithms. Finally we finish up with a look at the temporal variability of the microphysics by using the decorrelation time of the measurements as a statistical proxy.