Accession Number : ADA302213

Title :   Performance of an Iterative Analysis-Initialization Scheme at Low Latitudes in NOGAPS.

Descriptive Note : Final rept.,

Corporate Author : NAVAL RESEARCH LAB MONTEREY CA

Personal Author(s) : VanTuyl, Andrew H.

PDF Url : ADA302213

Report Date : NOV 1995

Pagination or Media Count : 29

Abstract : In common with many atmospheric models, the Navy Operational Global Atmospheric Prediction System (NOGAPS) tends to reject low-latitude height and divergent-wind data, thus the information added to the analysis by this data is largely removed during initialization. This study addresses this problem by repeatedly iterating the multivariate optimum interpolation analysis and nonlinear normal mode initialization of NOGAPS, with the goal of obtaining a balanced initial state in reasonable agreement with the original analysis. The impact of various optimum interpolation parameters on the results is examined; these parameters determine such analysis properties as mass-wind balance, horizontal divergence, and the length scale over which observations influence grid points. Results show minimal impact of the iterative scheme on data rejection, for all selected values of analysis parameters. There is little improvement in data retention when the background error variance is decreased, although the individual analysis and initialization-produced changes become smaller. Diabatic normal mode initialization produces only marginal positive impact on data acceptance, because the initialized vertical modes are nearly barotropic in the troposphere, thus only weakly influenced diabatic forcing. (AN)

Descriptors :   *ATMOSPHERE MODELS, MATHEMATICAL MODELS, EQUATORIAL REGIONS, OPTIMIZATION, PREDICTIONS, PARAMETERS, MULTIVARIATE ANALYSIS, WIND, ATMOSPHERIC MOTION, METEOROLOGICAL DATA, GRIDS(COORDINATES), NONLINEAR SYSTEMS, INTERPOLATION, CONVERGENCE, ITERATIONS, TROPOSPHERE, LATITUDE.

Subject Categories : Atmospheric Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE