Multiple scattering identi cation in W-band measurements of deep convective cores

CloudSat observations have indicated that multiple scattering affects 94 GHz spaceborne radar observations. The upcoming ESA EarthCARE explorer mission will also deploy a spaceborne 94 GHz radar to collect a vertical motion dataset on a global scale. Vertical velocity measurements will be collected in all cloud conditions, including deep convection where multiple-scattering is expected to contaminate the signal. Thus, it is imperative to develop a method to identify radar range gates contaminated by multiple scattering contributions.

Based on notional simulations, a criterion to identify the onset of multiple scattering is presented in this paper; the cumulative integrated reflectivity from the top of the atmosphere is a proxy of the multiple scattering enhancement and can be confidently used to detect the onset of multiple scattering. A statistical analysis conducted on two months of CloudSat data reveals that, for deep convective cores, the onset of multiple scattering typically occurs in the region around 9/10 km and more than 35% of the pixels above the freezing level height are not affected by multiple scattering. A fortiori, this assessment should be conservative for the EarthCARE spaceborne radar since such system is expected to have reduced multiple scattering contamination due to its smaller field of view.

By identifying the presence of multiple scattering in CloudSat/EarthCARE radar observations of deep convective cores this contribution has two major outcomes: 1) it allows to constrain the region of validity of currently developed CloudSat products based on single scattering theory (e.g. 2B-CWC-RO, 2B-CWC-RVOD and 2B-FLXHR); 2) it represents a mandatory first step for filtering out multiple scattering affected pixels in any analysis aimed at the assessment of the feasibility and of the accuracy of the EarthCARE Doppler estimates within deep convective cores.