Yes, in most cases the forecast fields at time 0 are the same as the analysis fields. The exceptions are:
- Soil temperature lev2 (over ocean)
- Soil temperature lev3 (over ocean)
- Soil temperature lev4 (over ocean)
- 2m temperature
- 2m dew-point temperature
- Sea ice cover (southwards of 75.5 South)
- Sea surface temperature (over lakes)
Soil temperature lev2, 3 and 4 are identical over land; however, over sea there are differences due to the re-computation of the sea-ice mixed temperature, using the new SST and ice fraction provided by the analysis.
The difference between the 2m temperature and the 2m dewpoint temperature is due to the nature of these two fields: they are diagnostic fields, computed at each forecast step (including step =0) as an interpolated value between the lowest level and the surface, whereas the analysed values are the result of a separate computation of the 2m analysis.
Sea ice cover is identical northwards of 75.5 South, and between there and the ice shelf off Antarctic they differ due to our current NEMO ORCA0.25 grid not covering this area.
Sea surface temperature (SST) is consistent over oceans and differs only over lakes. For "small" lakes, the SST values in the model come from the lake model FLAKE, whereas the values in the analysis come from climatology. Over larger lakes, i.e. the Great Lakes, Caspian Sea, and Azov Sea, satellite information is used. The difference between the analysis and fc step 0 is due to the initialisation procedure of FLAKE whereby the SST value used by FLAKE is nudged towards the satellite data in the analysis field.