Method for Remote Sensing of Precipitable Water Vapor and Liquid in the Atmosphere Using a 22-GHz Radiometer

摘要

Q well known method for retrieving the precipitable water vapor (v) and liquid (l) in a nonprecipitating atmosphere utilizes a dual channel radiometer operating at 20.6 adn 31.6 ghz. Statistical retrieval algorithms are used for the determination of V and L. In this study a somewhat different method for retrieval of the quantities V and L, using a radiometer, is described. The atmospheric opacities are determined at three frequencies, (nu1, nu2,nu3) near the water vapor line, from emission measurements. The frequency nu2 is the line center, and the frequencies, nu1, and nu3 are chosen such that (nu2)sq. = (nu1)sq + (nu3)sq. From these three measurements, a differential opacity which is dependent only on the resonant part of the water vapor absorption is derived. From this quantity, estimates of V and the clear atmosphere attenuation are obtained. The cloud opacity is obtained by subtracting the clear atmosphere attenuation from the total attenuation. In light rain the quantity V can be retrieved using this technique.