A GLOBAL SPECTRAL ATMOSPHERIC MODEL WITH HIGH VERTICAL RESOLUTION

A. V. Frolov, A. I. Vazhnik, V. I. Tsvetkov, and E. D. Astakhova

An improved high-resolution (with a doubled number of σ-levels) version of the global spectral atmospheric model of the Hydrometeorological Center of Russia is developed and optimized for the CRAY Y-MP8E supercomputer with a vector-pipelined architecture. The roots of the orthogonal Chebyshev—Laguerre polynomials specified on a semi-infinite line are used to define σ-levels. This provides the highest algebraic accuracy of the quadratures and ensures a stable pro-cessing of the matrix of vertical structure of discrete analog of linearized dynamical model operator. The top computation level was moved from 25 hPa to 10 hPa. The problem of preparing accurate and consistent initial data was considered. The results show a considerable improvement of medium-range pressure forecasts for the entire upper troposphere, and lower and middle stratosphere. Large-scale circulation features, such as a structure of polar jet stream in the winter hemisphere and an intensity of circumpolar anticyclonic vortex, were simulated more adequately. It is noted that parametrizations of subgrid scale processes must be adjusted to high vertical resolution in order to improve the medium-term forecasts in a planetary boundary layer.