25 ModifierTypes

A forecaster can modify a forecast with so-called Modifiers.  Within FEWS there are two types of modifiers: time series modifiers and parameter modifiers. Parameter modifiers can modify a parameter of a model or of a transformation.

Time series modifiers modify a time series. The original time series is stored in the database. However as soon as this time series is retrieved from the database the modifier will be applied to it. But it is important to note that the original time series is always available in the database.

Time series modifiers

Single value modifiers

A single value modifier is a modifier which modifies only one value at one time step in a time series. The display which is used for single value modifiers is shown below.

The user can enter a value in the text box by entering a value and by clicking on the spiner box next to it. The value can also be adjusted by the slider bar on the right side of FEWS.

In the example above we see the display of the single value modifier WECHNG. The WECHNG mod sets the value of the snow water equivalent in a specific snow model at one point in time.  Below the configuration of this modifier is shown.

<singleValueModifier id="wechng" name="WECHNG">

               <timeSeries>

                              <parameterId>WECHNG</parameterId>

               </timeSeries>

               <softLimits>

                              <maximumValue>5</maximumValue>

                              <minimumValue>0</minimumValue>

               </softLimits>

               <hardLimits>

                              <minimumValue>0</minimumValue>

               </hardLimits>

               <defaultTime>start run</defaultTime>

               <defaultValue>0</defaultValue>

</singleValueModifier>

First the id and name of the modifier is declared. The timeSeries-part identifies that this modifier can be applied to any time series which have the parameter WECHNG. The modifiers has some soft limits. These limits are used to limit the slider bar in the display. In this case the slider bar will start at 0 and end at 5. But these soft limits can be overruled by manually typing a value lower than zero or higher than 5. The hardLimits identify the upper and lower limit of the mod and they can not be overruled. This means that for this mod only the maximum value of the soft limit of 5 can be overruled.  A single value modifier is only applied at one time step. By default this is set to the start of the run in this modifier. The default value is set to 0.