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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 step towards a an unified land data assimilation system (de Rosnay et al., 2022), snow analysis has been implemented in the SEKF. This page shows details of the changes and the first result.
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- Input analysed snow depth from the 2D-OI (arpifs/obs_preproc/obsgen.F90)
- Calculate and input additional EDA Jacobians related to snow (gen/fetchmars, arpifs/sekf/sekf_geteda_jacobians.F90)
- Covariances between soil moisture (CV) and snow depth (OBS) are set to 0
- Covariances between snow water equivalent (CV) and 2m temperature, relative humidity, soil moisture (OBS) are also set to 0
- These 2 settings mean that observations to analyse each control variable are similar to the current systemsnow and soil moisture analysis are independent each other at the moment
- Jacobians between snow water equivalent (CV) and snow depth (OBS) are set to 1/rsn (based on the relationship in the model)
- Analyse snow water equivalent using the analysed snow depth and Jacobians (arpifs/sekf/sm_ekf_main.F90)
- σo=0.01 [m]
- σb=2.0 [kg/m2] (=0.01 [m] if rsn=200 [kg/m3])
- So far, increments for snow water equivalent are not reflected to the analysis field (offline calculation only)
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- Similar pattern is seen between the analysis increments for SWE in (1) the 2D-OI and (2) the SEKF.
- Note that large differences are seen in some regions due to inconsistency of snow density between the 2D-OI analysis and trajectory (lower limit of 100kg/m3 in the 2D-OI but 50kg/m3 in the model).
- When SWE from the 2D-OI is assimilated directly in the SEKF (3), such differences are not seen.
- (The trial branch: dako_CY48R1.1_SEKF_tmp)
- This will be not an issue in the future when snow depth observations are assimilated directly in the SEKF
| sekf_inc_l1.grib(SM1) | sekf_inc_l2.grib(SM2) | sekf_inc_l3.grib(SM3) | |
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Cntl (hzx1) |
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Test (i5eq) |
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- Analysis increments for soil moisture are similar the same (bit-identical) between before and after the changes.
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- Input snow observations directly in the SEKF (the same task similar work as soil moisture analysis using analysed 2m temperature and relative humidity)Need to implement a localization in observation space
- Each QC also should be implemented in the SEKF
- Consider flow-dependent background errors
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