D24    HIRLAM 4DVar results.

Responsible partner
Due date

This report is part of work-package 4100, the purpose of which is
·        Enable assimilation of ground based GPS data into 4DVar data assimilation systems.
Investigate impact of ground based GPS data when assimilated using 4DVar data assimilation systems.

Capability for operational assimilation of GPS data in 4DVAR.

Methodology/Work Description:
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.

The operators enabling assimilation of ground based GPS observations in 4DVar shall be tested. Secondly a number of case studies shall be performed, in which 4DVar assimilation of
GPS data is compared to simulations based on 3DVar analyses.

The 4DVar data assimilation simulations and results performed by DMI are reported in in the deliverable D24-HIRLAM-4dvar-results.pdf
Notice that the same deliverables contains the DMI reporting on their experiment in workpackage 3000 on correcting in 4DVar for the
temporal error correlations of GPS ZTDs.