Estimate of the tropospherical water vapor through microwave attenuation measurements in atmosphere

The objective of this paper is to proceed, by investigating the statistics of simulated measurements based on a large dataset of radiosonde profiles, to assess the feasibility of active systems providing water vapor profile information based on Earth-satellite multifrequency differential attenuation measurements made in the 18-22-GHz range. Recently, in fact, we pointed out the potential and the advantages of such measurements, showing in particular how a spectral sensitivity parameter could be exploited to provide the total water vapor content and further information about the shape of its vertical profile. In this work, we present an in-depth statistical analysis of the relationship between the spectral sensitivity parameter and the water vapor content at different tropospheric layers. Furthermore, we discuss the performance of a simple amplitude modulation transmit-receive system that could be adopted to provide the sensitivity measurements. It is shown that a dual-frequency system can directly provide with good accuracy the columnar water vapor content separately from the content of the 3-9 km atmospheric layer