Description

Available from Delft-FEWS version 2023.02.

Computes from an ensemble the probability of occurence of an event.

Events are defined as 

  • the exceedance of a value (e.g., "water level higher than 3.0m")                             > a
  • window between two values (e.g., "water level between 2.0m and 3.0m")              > a  && < b
  • non-exceedance of a value (e.g., "discharge less than 800 m3/s")                           < b


eventprobability range can consist of a lower and upper boundary (both are optional) and can be configured in 3 ways:
Boundary values directly as a value, an attribute or obtained from a timeseries.

<event><lower><value>10</value></lower></event>
<event><lower><value>@my_lower_bound@</value></lower></event> ,properties are also possible using $my_lower_bound$ instead
<event><lower><variableId>my_lower_bound_timeseries</variableId></lower></event>

Use <inclusive> true for strict lower and upper bounds (>= and <=)

Value:

value
	<transformation id="compute_probability_of_exceedance_of_spi_equal_to_two">
		<statisticsEnsemble>
			<eventProbability>
				<inputVariable>
					<variableId>spi</variableId>
				</inputVariable>
				<includeMissingValues>false</includeMissingValues>
				<event>
					<lower><value>2</value></lower>
					<upper><value>5</value></upper>
				</event>
				<outputVariable>
					<variableId>probability_spi_gte_2</variableId>
				</outputVariable>
			</eventProbability>
		</statisticsEnsemble>
	</transformation>

Attribute:

attribute
	<transformation id="compute_probability_of_exceedance_of_spi_equal_to_two">
		<statisticsEnsemble>
			<eventProbability>
				<inputVariable>
					<variableId>spi</variableId>
				</inputVariable>
				<includeMissingValues>false</includeMissingValues>
				<event>
					<lower><value>@lowerEvent@</value></lower>
					<upper><value>@upperEvent@</value></upper>
				</event>
				<outputVariable>
					<variableId>probability_spi_gte_2</variableId>
				</outputVariable>
			</eventProbability>
		</statisticsEnsemble>
	</transformation>

Timeseries:

timeseries
	<transformation id="compute_probability_of_exceedance_of_spi_equal_to_two">
		<statisticsEnsemble>
			<eventProbability>
				<inputVariable>
					<variableId>spi</variableId>
				</inputVariable>
				<includeMissingValues>false</includeMissingValues>
				<event>
                    <lower><variableId>lower_boundaries</variableId></lower>
					<upper><variableId>upper_boundaries</variableId></upper>
                </event>
				<outputVariable>
					<variableId>probability_spi_gte_2</variableId>
				</outputVariable>
			</eventProbability>
		</statisticsEnsemble>
	</transformation>

Example

In below example, the probability of three events is computed.

  • Event 1 is the event where Q.forecast < 10 m3/s
  • Event 2 is the event where 10 <= Q.forecast < 20 m3/s
  • Event 3 is the event where Q >= 20 m3/s.

In this example, the events are chosen in such a way that they are mutually exclusive and collectively exhaustive. The combined probability should therefore sum to 1. The configuration file for this example can be downloaded from here. A timeseries plot for the results is shown below.

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