An operational upper air analysis using the variational method

Abstract

An upper air objective analysis of wind and temperature has been developed for operational use at Fleet Numerical Weather Central. The primary feature of this analysis scheme is the vertical and horizontal extrapolation of information into the data-sparse regions from the data-rich surface and jet aircraft level. The extrapolation is based on Sasaki's recent extensions of the variational analysis method. The hydrostatic equation and horizontal momentum equations are used as dynamical constraints and these equations are combined to relate temperature and wind through a generalized thermal wind relationship. The governing analysis equations are elliptic and amenable to solution by the relaxation process. Vertical coupling of both wind and temperature is demonstrated through the detailed examination of a case study in the North Pacific.