Rain-associated microwave radiometric signatures in the frequency range of 90-220 GHz

Radiometric measurements were made by a microwave radiometer at the frequencies of 89, 150, 183.3±1, 183.3±3, 183.3±7, and 220 GHz aboard the NASA ER-2 aircraft at an altitude of -20 km over a rain storm in the Pacific Ocean on January 19, 1993. Nearly simultaneous measurements were made along the same flight path by another radiometer at the frequencies of 90, 183.3±2, 183.3±5, and 183.3±9 GHz aboard the NASA DC-8 aircraft at an altitude of ~11 km. Both data sets were examined and compared with the results of radiative transfer calculations based on existing cloud models. It was found that, mostly, the observations compared well with the calculated results. However, over a particular rain cell, a presence of frozen hydrometeors up to the height of ~16 km was needed in the model calculations to explain the observed radiometric signatures