Rainrate-reflectivity relationships based on the Classified Window Probability Matching Method (CWPMM) have been determined as a function of range, cloud type (convective or stratiform), and convective organization (e.g. squall line, tropical cyclone, etc.) using the WSR-88D data from Houston, Texas from 1993-1997. In all, more than 30 mesoscale convective systems (MCSs) were included in the data analysis.
The results show that there are distinctively different relationships for convective vs. stratiform precipitation with stratiform rain needing more reflectivity for a given rainrate. Moreover, the organization of the convection did seem to affect the relationship. Squall lines had statistically different Z-to-R conversions than other types of MCSs. Range dependency was most evident in unorganized, scattered convective storms as radar beam spreading reduced the peak magnitudes of the reflectivity that were associated with heavy rainfall. For our data set, organized tropical storm systems had essentially the same Z-to-R relationship as generic "embedded convection"-- i.e. convection that was embedded in stratiform rain.
These results represent the most exhaustive application of the CWPMM to date and provide strong evidence for the need of multiple Z-to-R conversions for radar based rainfall estimates