Hence sensitivity area can be identified with respect to initial surface pressure field. If those sensitive area are over the ocean and include buoys reporting air pressure, we can expect that those buoys would have a higher impact upon the cost function than buoys in other area. The version of the adjoint model used did not permit to obtain normalised gradients of J. Only the sign of each of the components of the gradient was reliable. So sensitive area could be identified but the level of sensibility could not be estimated. The adjoint model of the linear tangent model used is a spectral model of truncation T63 with 19 levels.
Adjoint model is adiabatic.
Limited T63 resolution was used to save computer power and memory resources. Drawing verification analysis for final validation. Plotting buoys providing pressure observations in found sensitive area. Study was based on the UKMO case1 of 29 September 1995 where Grant, Graham, and Bader showed that a few buoys reporting from the Atlantic Ocean had a significant impact upon the quality of rain forecast over southern England. It was assumed that meteorological situation over southern England on the 29 September 1995 at 12h00 UTC was quite sensitive to atmospheric surface conditions in certain area of the Atlantic Ocean.