Peculiarities of vertical atmosphere absorption in the millimeter wave band

Abstract

[1] One complete year of continuous observations of vertical radiation of the atmosphere in two points of millimeter wave band (94 and 38 GHz) was conducted. The total vertical absorption, liquid and vapor water content of atmosphere, and average (effective) temperature of clouds are restored on the basis of these two-frequency radiometric data. Numerous cases of abnormal differences between experimental and theoretical values of cloud absorption at the two frequencies were observed. An analysis of the collection of direct and indirect features that accompany the abnormal events is carried out. It is shown that the main sources of observed abnormal differences between theoretical and experimental data are snow and ice particles in clouds and, probably, water droplets of large size. The possibility of using two-frequency radiometric data not only for retrieving of liquid and vapor water content of atmosphere but also for determining the effective temperature of clouds and for assessing hydrometeor microstructure is noted. For this purpose, polarization measurements are very useful.

Preface to special section: Remote Sensing of the Earth's Environment by Microwave Radiometers and Radar

“…Part 1 discusses the theory and accuracy of several measurement selections, and part 2 discusses the effects of measurement and absorption model errors on retrieval accuracy. In the paper by Ruzhentsev [2003], brightness temperature observations at 94 and 38 GHz are analyzed for a variety of cloudy conditions to infer cloud liquid content and temperature. Other ground-based papers to study the atmosphere include those by Bosisio and Drufuca [2003] (by a tomographic technique, angular scans from a ground-based radiometer are used to derive 2-D absorption structure), Kadygrov et al [2003] (several lowaltitude parameters are derived from a single-frequency scanning 5-mm radiometer), Kutuza [2003] (theoretical relations and experimental data are given to illustrate the temporal behavior of downwelling brightness temperature at 0.8 and 1.35 cm), Cimini et al [2003] (scanning microwave and infrared radiometers are used in a tropical ocean experiment to derive boundary layer and oceanic temperature).…”