Data from an S-band polarimetric radar (NASA-NPOL) located at a mid-latitude, coastal location are used to compare two different methods for identifying stratiform and convective rain regions. The first method entails the retrievals of two (main) parameters of the rain drop size distributions (DSD) using the radar reflectivity and the differential reflectivity. The second technique is a well-known texture-based method which utilizes the radar reflectivity and its spatial variability. For the DSD-based method, an empirically improved retrieval technique was used, and the separation of the rain types was based on the estimated mass-weighted mean diameter and the normalized intercept parameter. Further, an additional category was also introduced for the DSD-based method to represent ‘mixed’ (or ‘transition’) rain type.

A widespread event with an embedded line convection, which occurred on 30 April 2020, was used as an initial test case. The two methods were compared using 500m by 500m pixel resolution gridded data (120 km by 120 km) constructed from the NPOL radar volume scan taken at 21:05 UTC. The comparison resulted in (a) 56% of the radar pixels being categorized as stratiform rain by both methods; (b) 21% as convective rain by both methods; and (c) a further 11% as the ‘mixed’ category from the DSD-based method. For the remaining 12% of the pixels, there was disagreement between the two methods which largely occurred in regions adjacent to (b).

The rain types are retrieved from data only at the lowest gridded level; however, it will be shown that they all have unique vertical structures indicative of contributions to latent heating through the column. Results will be presented for the gridded data and the error sources corresponding to each of the methods will be discussed.