THE 2ND-MOMENT CLIMATOLOGY OF THE GATE RAIN RATE DATA

The first part of this paper presents the description of the GARP (Glo bal Atmospheric Research Program) Atlantic Tropical Experiment 1 rain- rate data and its two-dimensional spectral and correlation characteris tics, which have made it possible to accomplish the following: to show the concentration of a significant power along the frequency axis in the spatiotemporal spectra; to detect a diurnal cycle (which has a ran ge of variation of about 3.4-5.4 mm h(-1)) as one of the sources of bi as in the rain statistics of satellite data; to study the distinction between the north-south and east-west transport of spatial rain-rate f ield and character of its anisotropy; to evaluate the scales of the di stinction between second-moment estimates associated with ground and s atellite samples; and to determine the appropriate spatial and tempora l scales of simple linear stochastic models fitted to averaged rain-ra te fields. The second part of this paper is devoted to an analysis of the diffusion of the rain rate by establishing a relationship between the parameters of the multivariate autoregressive model and the coeffi cients of a diffusion equation. This analysis]ed to the use of rain da ta to estimate the rain advection velocity as well as other coefficien ts of the diffusion equation of the corresponding field. The results o btained can be used for comparison with corresponding estimates of oth er sources of data (satellite, Tropical Oceans Global Atmosphere Coupl ed Ocean-Atmosphere Response Experiment, or simulated by physical mode ls), for generating multiple samples of any size, for solving the inve rse problems of some of the hydrodynamic equations, and in some other areas of rain data analysis and modeling.