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Task 1: Forecast error

Root-mean square error curves are often used to determine forecast error compared to the analysis.

In this task, all 4 forecast dates will be used.

Using the oper_rmse.mv icon, right-click, select 'Edit' and plot the RMSE curves for MSLP (mean-sea-level pressure) & wgust10 (10m wind gust).

Repeat for both geographical regions: mapType=0 and mapType=1.

Q. What do the RMSE curves show?
Q. How do they vary according to lead-time?

Task 2: Compare forecast to analysis

Use the oper_to_an_runs.mv icon (right-click -> Edit) and plot the MSLP and wind fields. This shows a comparison of each of the forecasts to the analysis.

Use the oper_to_an_diff.mv icon and plot the difference map between a forecast date (and the analysis.

code
Code Block
titleChange model run (forecast lead time) in oper_to_an_diff.mv
#Model run
run=2013-10-24

 

Task 3: Team working

As a team, discuss what the plots & parameters to use to address the questions above given what you see in the error growth curves and maps from task 2.

Then look Look at the difference between forecast and analysis to understand the error in the forecast, particularly the starting formation and final error.

Team members can look at particular dates and choose particular variables for team discussion.

Remember to save (or print) plots of interest for later group discussion.

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Exercise 3 : Visualize the ensemble forecasts and ensemble spread

Recap

Key points

  • Sources of forecast uncertainty: initial analysis and model error.
  • Initial analysis uncertainty: sampled by use of Singular Vectors (SV) and Ensemble Data Assimilation (EDA).
  • Model uncertainty: sampled by use of stochastic processes. In IFS this means Stochastically Perturbed Physical Tendencies (SPPT) and the spectral backscatter scheme (SKEB)
  • Singular Vectors: a way of representing the fastest growing modes.

  • Ensemble mean : this gives the average of all the ensemble members. Where the spread is high, small scale features can be smoothed out in the ensemble mean.
  • Ensemble spread: this gives the standard deviation of the ensemble members and represents how different the members are from the ensemble mean

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Ensemble exercise tasks

This exercise comprises more tasks than the previous two.

One of the difficul

Gliffy Diagram
nameensemble workflow

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