Snow clouds observation using the airborne cloud radar (SPIDER)

The National Institute of Information and Communications Technology (NICT) has been conducted various airborne experiments using the 95GHz cloud radar (named SPIDER), and the observations of snow clouds were performed during Winter MCSs (Mesoscale Convective Systems) Observation over the Japan Sea 2001, 2002 and 2003 (WMO-01, WMO-02 and WMO-03). From these experiments, various developing stage of snow clouds were observed.

SPIDER is dual polarized radar using linear polarization and has dual receivers for dual polarizations. The pulse-pair processing capability is also provided. Therefore, multi-parameter data, such as Doppler velocity, ZDR, LDR, ρHV(0), in addition to Z factor can be obtained. The sea surface return data were also used because the experiments were done over ocean. The difference between expected and received surface returns was caused by attenuation by the atmosphere and cloud liquid (or snow/rain). The typical multi-parameter data of snow clouds are shown.

Updraft at the lower altitude and little attenuation are found at the initial stage of developing snow. Strong updraft and down draft at middle altitude and strong attenuation are found at the mature stage. Down draft only at the low and middle altitude and little attenuation are found at decaying stage. It is considered that the attenuation is caused by super-cooled droplet in clouds. Additional analysis will be shown. The method of the identification of cloud droplet phase will be developed.