Remote measurements of snowfalls in Wakasa Bay, Japan with Airborne Millimeter-wave Imaging Radiometer and Cloud Radar

Results of concurrent airborne measurements of snowfalls with the Millimeter-wave Imaging Radiometer (MIR) and the Airborne Cloud Radar (ACR) are reported in this paper. The measurements were obtained during January-February 2003 in a field experiment in Wakasa Bay, Japan. The MIR is an imaging radiometer that measures radiation at seven channels between 89 GHz and 340 GHz. The ACR operates at 94 GHz and provides nadir-viewing radar reflectivity profiles with very good accuracy. Three days of snowfall events were observed during this field deployment. It was found that the MIR brightness temperature depressions at the frequencies of 183.3±1, 183.3±3, 183.3±7, and 340 GHz strongly correlate with the ACR reflectivity profiles during these snow events. Radiometric signatures from the remaining less opaque channels of the MIR (89, 150 and 220 GHz) showed ambiguity in snowfall detection due to variation in surface emissivities. An attempt to retrieve the ice water path and the median mass equivalent sphere diameter of the snowfalls would be described and results discussed.