Display ensembles and statistics

Summary

DELFT-FEWS can deal with ensemble forecast for some time already. More recently extended ensemble statistics and area display options have been added.
The display ensemble results as areas two steps are needed:

  1. Determine statistical parameter of the ensemble (min/max/percentiles)
  2. Use these to draw an area in the DisplayGroups file

(Ensemble) statistics

This is a new feature in the transformation utility. This way you can in a single command determine the max/min for all the members in an ensemble or a percentile. As with all functions in the transformation utility the way to use this is o (1) define an import variable. This can be a number of timeseriesSets but also an ensemble. (2) Define the (statistical) function. And (3) define the timeseriesSet to store the results.

The following functions are available:
• max
• min
• kurtosis
• mean
• median
• percentile
• quartile
• rsquared
• skewness
• standardDeviation
• variance

For some functions an extra attribute (value) should be used. E.g. for the percentile function the percentile should be given. An example configuration is shown below:

	<transformationSet transformationId="Q33">
		<inputVariable variableId="Q">
			<timeSeriesSet>
				<moduleInstanceSetId>TCM</moduleInstanceSetId>
				<valueType>scalar</valueType>
				<parameterId>Q.simulated.forecast</parameterId>
				<locationSetId>HydrologicalTCMModels</locationSetId>
				<timeSeriesType>simulated forecasting</timeSeriesType>
				<timeStep unit="minute" multiplier="15"/>
				<relativeViewPeriod unit="hour" start="-12" end="36"/>
				<readWriteMode>read only</readWriteMode>
				<ensembleId>MOGREPS</ensembleId>
			</timeSeriesSet>
		</inputVariable>
		<statistics>
			<function outputVariableId="Q33" inputVariableId="Q" function="percentile" value="33"/>
		</statistics>
		<outputVariable variableId="Q33">
			<timeSeriesSet>
				<moduleInstanceId>MOGREPS_TCM_Statistics</moduleInstanceId>
				<valueType>scalar</valueType>
				<parameterId>Q.simulated.forecast.33</parameterId>
				<locationSetId>HydrologicalTCMModels</locationSetId>
				<timeSeriesType>simulated forecasting</timeSeriesType>
				<timeStep unit="minute" multiplier="15"/>
				<relativeViewPeriod unit="hour" start="-12" end="36"/>
				<readWriteMode>read only</readWriteMode>
			</timeSeriesSet>
		</outputVariable>
	</transformationSet>

Displaying ensemble results

Within NFFS ensembles can be displayed as 'spagetti plot's' However, as these are a bit hard to digest one can also use the statistics (max/min/ percentiles) to display the forecast results as areas.

These area graphs can only be made as pre-defined displays i.e. in the DisplayGroups file in the SystemConfigFiles directory.

The areas are configured by entering timeseriesSets in the area element. As a results the area between the max and min values for each time are filled with a single color. The areas are always displayed behind the other lines. The area is painted on top of areas already specified, so specify the largest areas first. As the areas are painted on top of the lines you should also specify an opaquenessPercentage < 100% to make sure the lines remain visible.

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