Snowfall-Rate Retrieval for K- and W-Band Radar Measurements Designed in Hyytiala, Finland, and Tested at Ny-angstrom lesund, Svalbard, Norway

Two power-law relations linking equivalent radar reflectivity factor Z(e) and snowfall rate S are derived for a K-band Micro Rain Radar (MRR) and for a W-band cloud radar. For the development of these Z(e)-S relationships, a dataset of calculated and measured variables is used. Surface-based video-disdrometer measurements were collected during snowfall events over five winters at the high-latitude site in Hyytiala, Finland. The data from 2014 to 2018 include particle size distributions (PSD) and their fall velocities, from which snowflake masses were derived. The K- and W-band Z(e) values are computed using these surface-based observations and snowflake scattering properties as provided by T-matrix and single-particle scattering tables, respectively. The uncertainty analysis shows that the K-band snowfall-rate estimation is significantly improved by including the intercept parameter N-0 of the PSD calculated from concurrent disdrometer measurements. If N-0 is used to adjust the prefactor of the Z(e)-S relationship, the RMSE of the snowfall-rate estimate can be reduced from 0.37 to around 0.11 mm h(-1). For W-band radar, a Z(e)-S relationship with constant parameters for all available snow events shows a similar uncertainty when compared with the method that includes the PSD intercept parameter. To demonstrate the performance of the proposed Z(e)-S relationships, they are applied to measurements of the MRR and the W-band microwave radar for Arctic clouds at the Arctic research base operated by the German Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI) and the French Polar Institute Paul Emile Victor (IPEV) (AWIPEV) in Ny-angstrom lesund, Svalbard, Norway. The resulting snowfall-rate estimates show good agreement with in situ snowfall observations while other Z(e)-S relationships from literature reveal larger differences