Abstract

The use of a wavelet formulation and ensemble data assimilation is considered in this study, in order to specify flow‐dependent background‐error correlations for the Météo‐France global 4D‐Var system. This wavelet model is calibrated by using a temporal series of recent perturbed backgrounds, which is sampled in a sliding way. This approach is compared to a homogeneous and static spectral formulation of error correlations. Diagnostic studies are conducted in order to illustrate the representation of heterogeneous and flow‐dependent correlation features, corresponding for instance to smaller horizontal length‐scales in the vicinity of midlatitude lows and to larger vertical correlations in vertically unstable regions. The positive impact of the flow‐dependent wavelet formulation on the forecast quality is then shown during two contrasting three‐week periods. The impact of an increased ensemble size when using this approach is also illustrated, in terms of length‐scale dynamics and forecast quality.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.