The interplay of non uniform beam filling and multiple scattering in GPM-DPR observations: a notional study

Due to their large footprints (5x5 km2 close to nadir) the Global Precipitation Measuring Mission Dual-Frequency Precipitation Radar (DPR), especially in heavily precipitating convective clouds, is affected both by non uniform beam filling and multiple scattering effects. The interplay of the two makes the design of retrieval algorithms, which properly account for both effects, quite challenging. In this notional work, by using a high resolution 3D convective scenario simulated by a WRF model, we assess what is the combined effect of the two. DPR Reflectivities are forward modelled 1) by accounting for the full 3D-structure based on a MonteCarlo simulator (``exact simulation'') and 2) by adopting a hydrometeor profile obtained by weighting all profiles within the DPR antenna footprint based on a code which adopts a time-dependent two-stream approximation(``1D independent pixel approximation''). The differences between the two reflectivity profiles are then correlated to the inhomogeneity of the system. The exact simulation is then used as input in a retrieval model which adopts the two-stream approximation as forward model to assess the impact of non uniform beam filling effects.