A Flexible Interpolation Package to Support Existing and Future ECMWF Model Developments

As a leading NWP centre, ECMWF operates a data archive (of over 200PB) and a real time data dissemination service for users to access model results. Both services provide basic post-processing, especially regridding to Lat/Lon grids. Most users are not equipped to handle the spectral spherical harmonics representation and reduced Gaussian grids which are native to ECMWF's models. The software responsible for spectral transforms and regridding became, after 30 years of use, hard to maintain and increasingly a limiting factor for the evolution of ECMWF's systems and developments. Therefore ECMWF undertook a project to replace its interpolation package within its operational data processing services.

This work is closely linked with activities and developments on the research side for ECMWF's Integrated Forecasting System to establish a close link for future developments. The aim is to have new grids which are explored by scientists at ECMWF, available immediately by ECMWF's archive and data dissemination systems, which will greatly speed-up ECMWF's turn around of new model developments. This work required a fundamental review of how interpolations were performed as well as a review of mathematical models and numerical methods applied to the large variety meteorological parameters. The overall design of the software was reviewed and implemented with an object-oriented extensible design.

The presentation will give an overview of the challenges faced in replacing an existing post-processing package in ECMWF services. The motivation for changes and the work necessary to set up a more flexible and easier to maintain system will be presented. The immediate benefits and long term possibilities will be discussed.