Cloud Liquid Content Retrieval Errors Related to the Flat-layered Cloudfield Model Usage

• Published in: 2021 Photonics & Electromagnetics Research Symposium (PIERS) pp. 1978 - 1984
• Main Authors: Egorov, D. P., Ilyushin, Ya. A., Kutuza, B. G., Koptsov, Ya. V.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 21.11.2021
• Subjects: Atmospheric modeling; Brightness temperature; Clouds; Computational modeling; Liquids; Sea surface; Systematics
• ISSN: 2694-5053
• DOI: 10.1109/PIERS53385.2021.9695037

A problem of atmospheric moisture content distribution retrieval by means of dual-frequency radiometric method is considered. Systematic errors in cloud liquid water content retrieval related to the use of a homogeneous flat-layered cloudfield model, which ignores discontinuous and inhomogeneous structure of real cloudiness, are being investigated. To estimate these errors, a simulation of microwave spatial field of brightness temperature of the "ocean-atmosphere" system with discontinuous cumulus cloudiness taken into account is performed on the basis of Planck's model for random cloud fields generation, the standard atmosphere model, and the smooth water surface reflection model. An extensive database of simulated brightness temperature 2D-distributions has been precomputed for different values of Planck's model parameters. Fast software algorithms have been developed to process the data. That makes it possible to analyze mentioned systematic errors comprehensively for various initial cloud cover percentage while changing the size of antenna's resolution (or averaging) element by means of which a picture of discontinuous cloudiness is being reduced to a set of plane-layered approximations. The dependencies obtained are presented for various pairs of frequencies used in dual-frequency method and may be approximated, for example, by polynomials. The numerical simulation shows that for any Plank's distribution with a given cloud cover percentage the relative error of area-averaged liquid water content retrieval grows when the resolution element of antenna increases in size. It also shows that for any fixed size of the resolution element, if clouds are distributed in accordance to Plank's model, a decrease of cloud cover percentage (while all the other model parameters stay the same) leads to an increase in the relative error of area-averaged liquid water content retrieval.