A prototype upper-atmospheric data assimilation scheme based on optimal interpolation: 1. Theory

Introduced almost 40 years ago, the method of optimal interpolation (OI) ha s been successfully used in various forms for data analysis in meteorology and oceanography. At the same time upper-atmospheric applications of OI and other techniques based on optimal estimation have remained relatively limi ted. The theory of OI and related methods is reviewed. Properties of optima l estimation relevant to typical problems of data analysis in the upper atm osphere are highlighted. As a specific example, a simple one-dimensional sc heme of OI in time is considered. The scheme is devised to address an impor tant problem of the upper-atmospheric data analysis: extraction of periodic (tidal) components from observations covering a fraction of a day. Possibl e generalizations of the scheme are also briefly discussed. (C) 1999 Elsevi er Science Ltd. All rights reserved.