...
This task focuses on the fate of Nadine and examines vertical PV cross-sections of Nadine and the cutoff at different forecast times to characterize the diabatic warm core PV tower of Nadine compared to the upper level PV cold core of the cutoff.
Right-click on the icon 'hres_xs.mv' icon, select 'Edit' and push the play 
button.
...
| Panel | ||||
|---|---|---|---|---|
| ||||
Q. How does the ensemble mean MSLP and Z500 fields compare to the HRES forecast? |
Task 1: Ensemble spread
Use the ens_maps.mv icon and plot the MSLP and z500. This will produce plots showing: the mean of all the ensemble forecasts, the spread of the ensemble forecasts and the operational HRES deterministic forecast.
...
| Panel | ||
|---|---|---|
| ||
Q. How much uncertainty is there in the precipitation forecast over southern France? |
Compare ensemble members to the deterministic and control forecast
After visualizing the stamp maps, it can be useful to animate a comparison of individual ensemble members to the HRES and ensemble control deterministic forecastforecasts.
This can help in identifying individual ensemble members that produce a better different forecast than the control or HRES forecast.
Icons Use the ens_to_ref_diff.mv and icon to compare an ensemble member to the HRES forecast. Use pf_to_cf_diff.mvcan be used to compare ensemble members to the control forecast.
| Panel | ||||
|---|---|---|---|---|
| ||||
To animate the difference in MSLP of an individual ensemble member 30 to the analysisHRES forecast, edit the lines:
and visualise the plot. To compare the control forecast, change:
|
Further analysis using ensembles
| Panel | ||
|---|---|---|
| ||
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:
|
Sea-surface temperature
| Panel | ||||
|---|---|---|---|---|
| ||||
Compare the control forecast scenario to the HRES: Q. Try to identify ensemble members which are the closest and furthest to the HRES forecast. |
Sea-surface temperature
Compare the Compare the SST parameter used for the ens_oper and ens_2016 ensemble forecasts. The 2016 reforecast of this case study used a coupled ocean model unlike the 2012 ensemble and HRES forecast that used climatology for the first 5 days.
...
To show a cross-section of a particular ensemble member, use the macro ens_xs.mv.
This works in the same way as the hres_xs.mv macros.
Identifying sensitive regions
Find ensemble members that appear to produce a better forecast and look to see how the initial development in these members differs.
...
ens_xs.mv.
This works in the same way as the hres_xs.mv macros.
...
| borderColor | red |
|---|
...
Exercise 4: CDF, percentiles and probabilities
...
In this part of the task, redo the plots from the previous exercise which looked at ways of plotting ensemble data, but this time with clustering enabled.
|
...
Stamp maps: the stamp maps will be reordered such at the ensemble members will be grouped according to their cluster. This will make it easier to see the forecast scenarios according to your clustering. | |
| Spaghetti maps: with clusters enabled, two additional maps are produced which show the contour lines for each cluster. |
Use the clusters of ensemble members you have created in ens_oper_cluster.example.txt.
...
If you choice of clustering is accurate, you should see a clear separation of precipitation over France between the two clusters.
| Panel | ||
|---|---|---|
| ||
Q. What date/time does the impact of the different clusters become apparent? |
Task 2: Empirical orthogonal functions / Principal component analysis
...
| Panel | ||
|---|---|---|
| ||
Q. What do the EOFs plotted by eof.mv show? |
Plot Plot ensemble and cluster maps
Use the cluster definition file computed by eof.mv to the plot ensembles and maps with clusters enabled (as above, but this time with the 'eof' cluster file).
The macro cluster_to_ref.mv can be used to plot maps of parameters as clusters and compared to the analysis and HRES forecastsforecast.
Use cluster_to_ref.mv to plot z500 and MSLP maps of the two clusters created by the EOF analysis.
Edit cluster_to_ref.mv and set:
| Code Block | ||
|---|---|---|
| ||
#ENS members (use ["all"] or a list of members like [1,2,3] members_1=["cl.eof.1"] members_2=["cl.eof.2"] |
Run the macro.
If time also look at other parameters such as PV/320K.
Cluster 1 corresponds to a cutoff low moving eastward over Europe and cluster 2 to a weak ridge over western Europe. Cluster 1 exhibits a weak
| Panel | ||
|---|---|---|
| ||
| Panel | ||
| borderColor | redQ. What are the two scenarios proposed by the two clusters? |
...
cutoff low in the two clusters? |
|
If time, change the date/time used to compute the clusters. How does the variance explained by the first two clusters change?
...
Is geopotential the best parameter to use?
Changing the number of clusters
...