KAZR-CloudSat analysis of snowing profiles at the North Slope of Alaska: implications of the satellite radar blind zone

Spaceborne radars provide near-global observations of clouds and precipitation, but ground 19 clutter can result in a satellite radar blind zone as high as 2 km above the surface. As 20 a result, satellite radars may underestimate snowfall from shallow clouds and incorrectly 21 flag snow virga as snowfall at the surface. Ground-based radar observations provide in22 valuable tools to assess satellite observations of clouds and precipitation. This study in23 vestigates snowfall regimes using observations from 2011-2021 at the Department of En24 ergy Atmospheric Radiation Measurement North Slope of Alaska atmospheric observa25 tory. Snowfall events identified in the Ka-band ARM Zenith Radar (KAZR) are sepa26 rated into regimes based on the cloud/precipitation layer characteristics: deep snowfall, 27 shallow snowfall, and snow virga. The shallow snowfall regime accounts for nearly half 28 of the regime occurrence (48%) followed by snow virga (28%) and deep snowfall (23%). 29 However, more than half (62%) of the shallow snowfall is likely under-estimated and/or 30 undetected within the satellite radar blind zone. Snow virga is incorrectly flagged as snow31 fall for 7% of the total annual occurrence, but increases to 12% in October. The KAZR 32 regimes and vertical structure are qualitatively compared to collocated CloudSat obser33 vations with snow certain/possible flags; the deep and shallow snowfall regime show sim34 ilarities between the ground-based and spaceborne radar observations . An assessment 35 of observable snowfall occurrence and accumulation at varying reflectivity thresholds in 36 KAZR and CloudSat provide a reference for detection characteristics for current and planned 37 spaceborne radars.