Background
In the current operational system, snow analysis is based on 2D-OI separated from the SEKF (for soil moisture analysis) and the 1D-OI (for soil temperature and snow temperature). As a first step towards a unified land data assimilation system, snow analysis has been implemented in the SEKF. This page shows details of the changes and the first result.
Branches
dako_CY48R1.1_SEKF_snow
- ifs-scripts: https://git.ecmwf.int/users/dako/repos/ifs-scripts/browse?at=refs%2Fheads%2Fdako_CY48R1.1_SEKF_snow
- ifs-source: https://git.ecmwf.int/users/dako/repos/ifs-source/browse?at=refs%2Fheads%2Fdako_CY48R1.1_SEKF_snow
- ifs-suites: https://git.ecmwf.int/users/dako/repos/ifs-suites/browse?at=refs%2Fheads%2Fdako_CY48R1.1_SEKF_snow
Configurations to analyse snow water equivalent in the SEKF
- Input increments from the 2D-OI for snow depth (arpifs/obs_preproc/obsgen.F90)
- Input additional EDA Jacobians related to snow (arpifs/sekf/sekf_geteda_jacobians.F90)
- Covariances between soil moisture and snow depth are set to 0
- Covariances between snow water equivalent and 2m temperature, relative humidity, soil moisture are also set to 0 (consider snow depth only)
- Jacobians between snow water equivalent and snow depth are based on the relationship in the model (set to 1/rsn)
- Analyse snow water equivalent using the increments and Jacobians (arpifs/sekf/sm_ekf_main.F90)
Result
Future work
- Input snow observations directly in the SEKF (the same task as soil moisture analysis using 2m temperature and relative humidity)
- Need to implement a localization in observation space
- Each QC should also be implemented in the SEKF
- Consider flow dependent background errorsÂ