The Autumn 1999 Global Data Assimilation Upgrade Package
BELL, R.S. ; Dalby, T.D. ; Li and D. ; Saunders F.W.
Global 3DVAR (Lorenc et al 2000) was implemented in March 1999. As with any new system, there is ample scope for tuning. This paper described the revisions to the global data assimilation system which is planned for implementation on 19th October 1999. Some details of an interim revision, which was made to the system in July, are also presented. In brief the changes for July and October involve: Direct Assimilation of ATOVS Radiances replacing the assimilation of retrieved temperatures and an extension of the geographic coverage of ATOVS data; use of surface wind speed derived from the SSM/I microwave imager; improved derivation of Model Surface Pressure from Synop Station Pressure Reports; updating of the Statistics used for the Background Error Covariance Model and revising the formulation of the Model; thinning and revision of observation error of Aircraft Data; use of Wind Data from South Pole Station; thinning of Scatterometer Wind Observations and rejection of reports over Ice. The ...
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