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Use the large geographical area for this task. It is only possible to use the MSLP parameter for this task as it is the only one provided for the ensemble.
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Task 4.
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Non-linear development
Ensemble perturbations are applied in positive and negative pairs. For each perturbation computed, the initial fields are CNTL +/- PERT. (need a diagram here)This is done to centre the perturbations about the control forecast.
So, for each computed perturbation, two perturbed initial fields are created e.g. ensemble members 1 & 2 are a pair, where number 1 is a positive difference compared to the control and 2 is a negative difference.
- Choose an odd & even ensemble member from one of the 3 OpenIFS forecasts (e.g. members 9 and 10). For different forecast steps, compute the difference of each member from the control forecast and then subtract those differences. (i.e. centre the differences about the control forecast).
- What is the result? Do you get zero? If not why not? Use Z200 & Z500? MSLP?
- Repeat looking at one of the other forecasts. How does it vary between the different forecasts?
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