Wavelet analysis of simulated tropical convective cloud systems. Part I: Basic analysis

A wavelet analysis of a three-dimensional 7-day explicit simulation of the tropical cloud systems in the Global Atmosphere Research Programme (GARP) A tlantic Tropical Experiment Phase III is performed. Three physically distin ct regimes (squall line, nonsquall cloud cluster, and scattered convection) in a doubly periodic domain are analyzed using discrete Meyer wavelets. Th ese wavelets are complete and facilitate the inversion of the decomposed mo des. The full wavelet spectra well characterize the spatial localization of each physical variable, in particular, the vertical velocity and the condensate fields. The probability distribution of the wavelet coefficients is non-Ga ussian despite the horizontal winds, the temperature, and humidity being cl osely Gaussian in physical space. This demonstrates the effectiveness of th e wavelet basis for analyzing cloud system organization. The full wavelet s pectrum also selects a preferred spatial orientation of the convective orga nization in physical space. A pseudospectrum is defined by taking the maximum absolute value of the wav elet coefficients for a given horizontal wavenumber vector as the spectrum coefficient. Unlike the conventional spectrum, this pseudospectrum objectiv ely selects the observed convective-scale and mesoscale structure character istic of observed mesoscale convective systems. The results demonstrate the broad utility of discrete Meyer wavelet analysi s for objectively characterizing the structure and organization of multisca le convective cloud systems in an objective way.