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This study examines the possibility for a theoretical approach in the\udestimation of water vapour mixing ratios in the vicinity of polar mesospheric\udclouds (PMC) using satellite observations of Volume Scattering Radiances\ud(VSR) obtained at the wavelength of 553 nm. The PMC scattering properties\udperturb the underlying molecular Rayleigh scattered solar radiance of the\udbackground atmosphere. As a result, the presence of PMC leads to an\udenhancement in the observed VSR at the altitude of the layer; the PMC VSRs\udare superimposed on the exponentially decreasing with height Rayleigh VSR, of\udthe PMC-free atmosphere. The ratio between the observed and the Rayleigh VSR\udof the background atmosphere is used to simulate the environment in which the\udcloud layer is formed. In addition, a microphysical model of ice particle\udformation is employed to predict the PMC VSRs. The initial water vapour\udprofile is perturbed until the modelled VSRs match the observed, at which\udpoint the corresponding temperature and water vapour profiles can be\udconsidered as a first approximation of those describing the atmosphere at the\udtime of the observations. The role of temperature and water vapour in the\udcloud formation is examined by a number of sensitivity tests suggesting that\udthe water vapour plays a dominant role in the cloud formation in agreement\udwith experimental results. The estimated water vapour profiles are compared\udwith independent observations to examine the model capability in the context\udof this study. The results obtained are in a good agreement at the peak of\udthe PMC layer although the radiance rapidly decreases with height below the\udpeak. This simplified scenario indicates that the technique employed can give\uda first approximation estimate of the water vapour mixing ratio, giving rise\udto the VSR observed in the presence of PMC

Retrieving mesospheric water vapour from observations of volume scattering radiances