Statistical-dynamical analysis of wind observations using a variational approach

In this paper, we present a variational analysis of wind and pressure data which takes into account statistical characteristics of the data and a line ar model describing the dynamical relations between the analysed variables. The variational approach is used to adjust the given data to the dynamical model and it will be shown that this adjustment process can be controlled in an uncomplicated, comprehensible, and reproducible way by very few param eters only. The dependence of the analysis results on these parameters is i nvestigated in theory and this theoretical conclusions are tested by an app lication. it is studied how effectively this method can be used to correct erroneous data. We apply the analysis to the GOADS (Comprehensive Ocean-Atm osphere Data Set) wind and pressure data of the Januaries 1951-1993 over th e North Atlantic and introduce the Ekman balance as a weak dynamical constr aint. This specific data set is chosen because several previous investigati ons suggested that there is a spurious trend in the GOADS wind speed of sim ilar to1 ms(-1) since the mid-century. The results show that the control parameters can be effectively used to shi ft the wind field continuously between the identity with the input data and the exact consistency with the dynamical model. But it has to be admitted that the Ekman balance is inadequate in the tropics and that it overestimat es the magnitude of the horizontal vector wind although this dynamical mode l is more suitable than the frequently used geostrophic balance.