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Many people have contributed to this exercise and their contributions are acknowledged, in particular from ECMWF: Glenn Carver, Linus Magnusson, Sandor Kertesz, Martin Leutbecher, Iain Russell, Filip Vana, Erland Kallen. From University of Oxford: Aneesh Subramanian, Peter Dueben, Peter Watson, Hannah Christensen, Antje Weisheimer.
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NOTES
These will disappear in the final handout.
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- Difference maps : to plot fc - an and ens member - control ( or ens member(i) - ensemble member(j) )
- step animation of spaghetti plots etc to see spread developing.
- Linus' vortex centre & tracking plot
Retrieve data from MARS for all apart from the OpenIFS experiment the participants will run themselves.
Note that operational ensemble runs at T319 are also available if we want to use them to compare 40r1 with OpenIFS? (see Linux for MARS script)
wind gust data is not simply max windspeed over 6hr period, it includes convective component (as well as conversion from windspeed to gust speed).
need to fake windgust data!
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In exercise 1, the aim is to study the error between the forecast and the analysis. Key points: The forecast developed the storm too early, even for the forecast on the 27th. Storm was too far west. plot Z200 to see position of the jetstream. For the ensemble, plotting the mean will remove some features - might be useful for class to see this. Note how spread is small for northerly low centre where uncertainty is much less. Make sure they use 4 frame layout and plot 25th, 26th, 27th + analysis. Also, 25th, 26th & their difference |
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Question. How best to organise the experiments? Each user has an account or use one account with multiple directories? Linus suggested running a script that reorders the data to have 1 file with all ensemble members for each field of interest. Do this after all members have run? |
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Suggests doing 2 more runs: EDA only and SV only. The perturbations from these have different characteristics and as we don't yet know what the results look like it might be useful to have these runs. (I may not have all the details right - check with Linus who apparently did a PhD thesis on this) Relate the perturbations to the baroclinic zones (ie. large scale flow). While the cyclone is developing the baroclinicity will be high and the EDA/SV perturbations will be more significant than when the storm is more developed with fronts when it will be more stable. Should see that SV are quite artificial, some pertubations will grow rapidly and then die out. By contrast the perturbations in the EDA will be larger in the initial conditions. Maybe we should plot the Eady index? Erland says very important to plot these and see what we get in order to refine the questions and direction we want participants to take. |
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Linus explained that with the OpenIFS runs will have differing amounts of uncertainty, so the spread should noticeably change for points near the track in the analysis. This is particularly because of (a) timing error between the analysis & fc, (b) the ensemble tracks being more to the north of the analysis track. So Amsterdam for instance should see much less spread as the uncertainty in the ensemble is reduced. Parameters that do not have a Gaussian like distribution in the ensemble can be problematic. |