Multivariate objective analysis of wind and height fields in the tropics

Abstract

The commonly used objective analysis scheme (Scheme-A) for the analysis of wind and geopotential height smoothen the divergent component of the wind which is rather important in the tropics, specifically over convective regions. To overcome this deficiency, a new analysis scheme in which divergent component is included in the statisti-cal model of the wind forecast errors, has been proposed by Daley (1985). Following this scheme, a new set of correla-tion functions of forecast errors for the Indian region during monsoon season which are suitable for analysing the tropical wind are obtained. This analysis scheme (Scheme-B) as well as Scheme-A were used to make analyses for the period from 4 July to 8 July 1979 (12 GMT) at 850, 700 and 200 hPa levels over an area bounded by 1.875°N to 39.375°N and 41.250°E to 108.750°E and subsequently divergent component, velocity potential are computed for both schemes. Results from both these schemes show that in the monsoon depression region the velocity potential and divergence have increased in the later case (Scheme-B). This suggests that the divergent component has been en-hanced in Scheme-B and that the objective of this study is realized to some extent.