ICE DEPOLARIZATIONS ON KA BAND (20 GHZ) SATELLITE-TO-GROUND PATH AND CORRELATION WITH RADAR OBSERVATIONS

The ice depolarization events without appreciable copolarized attenuation are investigated using the CS-2 beacon signal (19.45 GHz) and the simultaneous radar observations. In these events, increase of instantaneous depolarizations of the beacon signal closely corresponds to appearance of intense radar echoes at the cloud top. Correlation of the time variations between the depolarizations and the radar echoes is, in general, found in the upper half of the ice region. In addition, the large depolarization events are primarily related to the radar echo intensities at 2.0-2.5 km above the bright band. In these heights the ice crystals may have the fastest growth rate around the temperature of -15-degrees-C. The impact of ice depolarizations on the satellite-to-ground path is shown to depend strongly upon the height and the background temperature at which ice crystals are first produced near the cloud top. This characteristic feature of ice depolarization is also confirmed in the stratus type events with considerable rain attenuation by theoretically subtracting the effects of raindrops from the total observed depolarization.