Correction phase A in 4d Var. ('gradient')
- Gradients of the observation part of the cost function with respect to pressure and potential temperature fields (model level 22 shown) are advected backwards in time (12 timesteps).
- The observation that we are interested in occurs at t=7.
- The gradient fields at t=0 show which regions of the atmosphere influence the model observation. There is thus information in the ATOVS observation to allow these regions to be modified (there are a few other observations also present in this 4d Var. run).
d(Jobs)/d(Pressure) (left) d(Jobs)/d(Potential temperature) (right)
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