It is foreseen that ground based GPS observations due to their high time resolution will have the highest impact when assimilated using 4DVar assimilation systems. At both DMI and the Met Office, a 3DVar assimilation system is currently in operational use and 4DVar versions are under development.
operators enabling assimilation of ground based GPS observations in
be tested. Secondly a number of case studies shall be performed, in
GPS data is compared to simulations based on 3DVar analyses.
The observation operator
developed at the UK Met Office for assimilation of ZTD data in 3-
and 4DVar is described in this report:
A forward model for the assimilation of ZTD data in 3- or 4DVar systems. The report includes details on how corrections are done for the offsets between the GPS antenna heights and the model orography (model heights).