Outlook for a new wind field retrieval technique: The 4D-Var wind retrieval

In this paper we introduce the 4D-Var wind retrieval, which is inspired on four-dimensional variational assimilation, typically used in numerical weather models. We simulate simple wind scenarios, with single or double vortices, to get insight in radar measurements.We apply the linear wind model to radar measurements of IDRA radar measurements and identify some problems with the linear wind model retrieval technique. Then we apply the 4D-Var wind retrieval on the same IDRA measurements and the results are compared and discussed. In the implementation it is possible to specify correlation lengths for the horizontal wind speed and horizontal wind direction. With this option, it is possible to show the ambiguity of the wind field, that is associated with the radar measurements.