The impact on Forecast Skill of Using Wind Observations from Different Scatterometer Processing Methods
Berney, A. ; CANDY, B. ; Li and D.
For over six years wind observations from scatterometers flown on the ERS satellite series have been assimilated into the UKMO global Numerical Weather Prediction (NWP) model. Since its implementation the observations have been used at a density which is much higher than the analysis resolution. The first part of this study looks at the effect of thinning the scatterometer observations to 1 per analysis gridpoint which results in improved convergence within the assimilation scheme. Backscatter measurements from the ocean surface are processed to wind vectors using an in-house scheme whilst an alternative scatterometer wind product is available from the European Space Agency (ESA). In the second part of the study we compare the effect on the forecast skill of the model when winds are assimilated from either wind product. Results show that assimilation of the UK wind product leads to a large positive impact on the forecast score (0.7% on the global index), mainly in the Southern Hemisphere. However nearly all of this impact is lost if we switch to using the ESA product.
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