Differential Radiometric Methods for Measurements of the Vertical Profile of Water Vapor in the Troposphere and Stratosphere of the Earth

Abstract

Differential methods for determining the height profile of one of the most important greenhouse gases in the Earth’s atmosphere—water vapor—based on ground and satellite radio thermal microwave measurements in the absorption band of 22 GHz, are considered. The substantiation of a fundamentally new difference-differential method is carried out using the difference of differential signals on different slopes of the absorption line of the measured gas. This method makes it possible to increase the spatial selectivity of measurements and reduce the influence of clouds, precipitation, and third-party gases, as well as carry out measurements above the water surface. The results of the calculation of the kernels of integral equations are given for measurements in the absorption band of water vapor of 22 GHz. The selectivity of the kernels makes it possible to restore the water-vapor profile both in the lower troposphere layer to heights of 8 km and in the stratospheric–mesospheric layer of 30–80 km. The advantage of the proposed methods is the differential nature of the measurements, which does not require the absolute calibration of sources and long-term stability of the equipment.