Passive microwave imagery of a tropical storm near 118 GHz thermal and precipitation structure

An imaging microwave radiometer with eight double-sideband channels centered on the 118.75-GHz (1-)oxygen resonance was flown on a NASA ER-2 high altitude aircraft over a tropical cyclone in the Coral Sea, east of Australia. An eyewall of strong convection and a warm core within the eye are clearly visible. Brightness temperatures observed within the eye are approximately 10K warmer than those observed in clear air 100 km away. This warming extends somewhat beyond the eyewall in the highest (most opaque) channel. Two passes three hours apart may reveal a slight weakening of the convective activity. This flight provides the first known calibrated high-resolution 18.75 GHz imagery of a tropical storm. Temperature profiles and cloud-top altitudes may be inferred from the data. >