HIGH-RESOLUTION IMAGING OF RAIN SYSTEMS WITH THE ADVANCED MICROWAVE PRECIPITATION RADIOMETER

An Advanced Microwave Precipitation Radiometer (AMPR) has been develop ed and flown in the NASA ER-2 high-altitude aircraft for imaging vario us atmospheric and surface processes, primarily the internal structure of rain clouds. The AMPR is a scanning four-frequency total power mic rowave radiometer that is externally calibrated with high-emissivity w arm and cold loads. Separate antenna systems allow the sampling of the 10.7- and 19.35-GHz channels at the same spatial resolution, while th e 37.1- and 85.5-GHz channels utilize the same multifrequency feedhorn as the 19.35-GHz channel. Spatial resolutions from an aircraft altitu de of 20-km range from 0.6 km at 85.5 GHz to 2.8 km at 19.35 and 10.7 GHz. All channels are sampled every 0.6 km in both along-track and cro ss-track directions, leading to a contiguous sampling pattern of the 8 5.5-GHz 3-dB beamwidth footprints, 2.3x oversampling of the 37.1-GHz d ata, and 4.4x oversampling of the 19.35- and 10.7-GHz data. Radiometer temperature sensitivities range from 0.2-degrees to 0.5-degrees-C. De tails of the system are described, including two different calibration systems and their effect on the data collected. Examples of oceanic r ain systems are presented from Florida and the tropical west Pacific t hat illustrate the wide variety of cloud water, rainwater, and precipi tation-size ice combinations that are observable from aircraft altitud es.