| | 3 | There was nothing apparently odd with the data or the bg for this profile, although it (like the 1st) is sited in the S Hemisphere (~50S), which has higher bg err covs - see red line here: [[Image(cov.png)]] |
| | 4 | |
| | 5 | So I just reduced the SH errors to be the same as in the tropics (white line above), which implies a reduction in the sigmas by about 2/3. (This requires setting bg_covar_method= FSFC in the metoffice_refrac_1dvar.cf config file, and editing a local file.) |
| | 6 | |
| | 7 | This had little effect. So I artificially further reduced all the bgerr covs by a factor of 10 above 35km. The result is shown here: [[Image(Test2_reduced_bgerrcov.gif)]] |
| | 8 | |
| | 9 | Clearly, much more reasonable temp changes. |
| | 10 | |
| | 11 | This is not to say that these are the ''correct'' bg err covs to use in this case; merely that a reasonable change in them can produce drastic change in the retrievals. In other words, this is a data issue, not a ROPP issue. |
| | 12 | |
| | 13 | Interestingly, the original temperature increment is much reduced (to ~3K) by using the non-default LevMarq minimiser, rather than the default minropp - see here: [[Image(Test2_levmarq.gif)]] |
| | 14 | |
| | 15 | Again, it's resolved by reducing the bgerr covs at height: |
| | 16 | [[Image(Test2_levmarq_reduced_bgerrcov.gif)]] |
| | 17 | |
| | 18 | |
| | 19 | |
