A SIMPLE-MODEL OF LONG-PERIOD VARIABILITY OF ATMOSPHERIC MOISTURE WITH REFERENCE TO ITS INTERACTION WITH SOIL

The characteristic properties of the spectra of fluctuations in atmosp heric moisture content related to its interaction with soil moisture o n long-period (from a month to a few years) time scales have been reco nstructed on the basis of a simple stochastic model of interactions be tween atmospheric and soil moisture. The model is optimized to describ e advective precipitation. It is shown that the results of the reprodu ction of the spectra of atmospheric moisture fluctuations obtained wit h a complete three-dimensional climate model [1, 2] are explained by t he model's linear response to synoptically induced fluctuations in soi l moisture content for characteristic response times. The effect of gr owth of the spectrum of atmospheric moisture variability in the interm ediate frequency range, associated with nonlinear aspects of precipita tion formation, has been discovered and explained. The algorithm propo sed for calculations of the spectra of fluctuations in this region dir ectly relates the changes in mean values and fluctuation spectra.