The Operational Mesoscale Data Assimilation System 1999-2001: Implementation of 3DVar and Later Upgrades
Macpherson, Bruce ; Andrews, P. ; Harcourt [S.] ; Ingleby [N. Bruce] ; Renshaw, R. ; Parrett, Colin ; Anderson, Simon ; Sharpe, Martin ; Harrison, D. ; GIBSON, M.
The Mesoscale version of 3DVar was introduced operationally in October 1999, replacing the previous Analysis Correction (AC) scheme. Since then, it has undergone significant upgrades in June 2000 and February 2001. This technical report documents the various trials leading to the original implementation and subsequent enhancements. The contents of the upgrade 'packages' are specified, along with subjective and objective assessment of their impact on key forecast variables. The overall signal from the first version of 3DVar is probably best described as a slight benefit, with the main improvements coming in the analysis and short-period forecast of fog and prediction of light rain in summertime. The main impact of the June 2000 upgrade, involving a revision of the forecast error covariances, proved to be a slight improvement for precipitation. The February 2001 upgrade brought an improvement in screen temperature resulting from introduction of a soil temperature increment. It also saw the introduction of wind profilers and higher density Meteosat wind data. Alongside ...
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