A New Analysis to Diagnose Ageostrophic Winds from Wind and Temperature Measurements Made by an Observational Network

Abstract

The present paper is devoted to a new analysis of winds and temperature measurements made by an observational network in order to provide the 3D ageostrophic circulations. This analysis may be used with data from instrumented networks providing wind measurements such as Doppler radars or ST (stratospheric-tropospheric) radars networks, as long as thermodynamic data are available. This analysis referred to as AVAG (analyse du vent agéostrophique) is mathematically described. An application of the method to simulated and to real data is also presented. The method consists in expanding the three ageostrophic wind components in terms of orthogonal functions. Physical constraints on the geostrophic part and on the ageostrophic part of the wind are also included in the analysis as variational constraints in order to improve the results. The data of any number of stations may be included in the analysis without reformulating the problem (allowing to deal with inhomogeneous datasets where, for example, the number of dynamic and thermodynamic measurements are different). This analysis may be also used in order to obtain the detailed structure of the temperature field from wind measurements provided that a few temperature measurements are available. In this case the analysis is used as an interpolation method (based on physical constraints) between sparse temperature measurements using the available dynamical information (case of a network that involves, for example, ST radars and radio-sounding stations providing continuous wind measurements and 12-h temperature measurements).