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Task 3: Changing geographical area
Right-click on 'an_1x1.mv' icon and select 'Edit'.
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Animating. If only one field on the 2x2 plot animates, make sure the menu item 'Animation -> Animate all scenes' is selected. Plotting may be slow depending on the computer used. This reads a lot of data files. |
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Q. What do you notice about the SST field? |
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The plot shows potential vorticity (PV), wind vectors and potential temperature roughly through the centre of the Hurricane and the cut-off low. The red line on the map of MSLP shows the location of the cross-section.
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Q. Look at the PV field, how do the vertical structures of Nadine and the cut-off low differ? |
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Repeat for both geographical regions: mapType=1 (Atlantic) and mapType=2 (France).
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1Q. What do the RMSE curves show? |
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Use the hres_to_an_diff.mv icon and plot the difference map between the HRES forecast and the analysis for z500 and mslp.
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1Q. What differences can be seen? |
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As for the analyses, the macros hres_1x1.mv, hres_2x2.mv and hres_xs.mv can be used to plot and animate fields or overlays of fields from the HRES forecast.
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Q. How does the timing and distribution of the precipitation from the forecast compare to the observations shown in the paper by Pantillon? |
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In these tasks, the performance of the ensemble forecast is studied.
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Q. How does the ensemble mean MSLP and Z500 fields compare to the HRES forecast and analysis? |
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Clustering will be used in later tasks.
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Q. How do the HRES, ensemble control forecast and ensemble mean compare? |
There might be some evidence of clustering in the ensemble plumes.
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#ENS members (use ["all"] or a list of members like [1,2,3] members=["all"] #[1,2,3,4,5] or ["all"] or ["cl.example.1"] |
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Q. How does the mean of the ensemble forecasts compare to the HRES & analysis? |
Task 3: Spaghetti plots - another way to visualise spread
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Use the stamp_diff.mv plot to look at the differences between the ensemble members and the analysis. It can be easier to understand the difference in the ensembles by using difference stamp maps.
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Q. Using the stamp and stamp difference maps, study the ensemble. Identify which ensembles produce "better" forecasts. |
Compare ensemble members to analysis
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Further analysis using ensembles
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This will show the forecasts from the ensemble members and also their difference with the ensemble control forecast. To animate the difference in MSLP with ensemble members '30' and '50', set:
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Find ensemble members that appear to produce a better forecast and look to see how the initial development in these members differs.
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Make sure useClusters='off'.
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Q. Compare the CDF from the different forecast ensembles; what can you say about the spread? |
Forecasting Forecasting during HyMEX : Work in teams for group discussion
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In this exercise you will:
- Construct your own qualitative clusters by choosing members for two clusters
- Generate clusters using principal component analysis (similar to Pantillon et al).
Task 1: Create own clusters
Clusters can be created manually from lists of the ensemble members.
Refer back to the plots from the previous exercise to choose Choose members for two clusters. The stamp maps are useful for this task.
From the stamp . map of z500 at 24/9/2012 (t+96), identify ensemble members that represent the two most likely forecast scenarios.
It is usual to create clusters from z500 as it represents the large-scale flow and is not a noisy field. However, for this particular case study, the stamp map of 'tp' (total precipitation) over France is also very indicative of the distinct forecast scenarios.
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Right-click 'ens_oper_cluster.example.txt' and select Edit. (or make a duplicate) The file contains two example lines:
The first line defines the list of members for 'Cluster 1': in this example, members 2, 3, 4, 9, 22, 33, 40. The second line defines the list of members for 'Cluster 2': in this example, members 10, 11, 12, 31, 49.Use the z500 stamp map at t+96 to create your two clusters with members that you consider represent the two most likely scenarios. Change these two lines!. You can create multiple cluster definitions by using the 'Duplicate' menu option to make a copy copies of the file for use in the plotting macros.. The filename is important. ! |
Use your own clusters:
RMSE curves
lot With this text file in place, now replot the:
RMSE curves
Stamp maps
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