Pressure wind adjustment relationships during dynamic initialization process with tropical wind data

Abstract

In an attempt to understand the kind of balance the initially imbalanced low latitude mass and motion fields tend to adjust to during an iterative dynamic initialization process we carry out a systematic investigation of the pressure-wind adjustment laws. This is achieved by comparing, through root mean square differences, the mass field (z) from the initialization process with each of the three other mass fields (z) obtained, using motion fields from initialization process, from diagnostic expressions which relate mass and motion fields. The diagnostic relationships used in this study are the nonlinear, linear and quasi-geostrophic balances equations. The results from these investigations show thatz fields from nonlinear balance approximation are closets to thez fields accruing from the initialization process. Next in closeness is the linear balancez fields which appear to be not very different from the nonlinear balance approximation. The last in closeness is the quasi-geostrophic balance approximation which appears to be 2–3 times, in terms of rms values, as far away as the nonlinear approximation. In fact, the root mean square differences betweenz fields from the initialization process and those from nonlinear balance equation are about 10 metres and the root mean square differences involving thez fields from the quasi-geostrophic balance equation are 30 metres.

In the initialization scheme we have used primtive equation model. We therefore hope that the pressure-wind adjustments that are being effected by the initialization process would be representative of those in real atmosphere. On this premise, the results indicate further that nonlinear and linear balance equations approximate reasonably well to the balance between large scale motions and pressure fields in the tropical regions.