Forecast
Rameau is able to run an ensemble forecast. Forecast can be activated in the TOML configuration file.
[forecast]
forecast = true
Forecast settings
Emission date
The date and time for which to issue a forecast is defined through the
emission_date key. If omitted, the default value corresponds to the last
date of the meteorological input data.
[forecast]
emission_date = 2009-01-01
Scope
The scope key is the time between the emission_date and the end of
the probabilistic forecast.
Default value is one day.
[forecast]
scope = { days = 30 } # Format : { days = 30, minutes = 0, hours = 0, seconds = 0 }
Ensemble forecast members
Rameau uses the past climatology to produce the ensemble forecast members.
Each year of the past climatology corresponds to a member. The years to consider
to form the forecast ensemble members are provided through the year_members
key. If not provided, all years in record are considered.
For example, we consider a 30-day forecast issued on 2009-01-01. Inputs provide meteorological data from 2000-01-01 to 2009-12-31. Therefore, the forecast ensemble will consists in 10 simulations all starting from 2009-01-02 using the following meteorological inputs:
1st member: from 2000-01-02 to 2000-01-31
2nd member: from 2001-01-02 to 2001-01-31
…
…
10th member: from 2009-01-02 to 2009
We could have also used the year_members key for selecting specific
years, for example 2000 and 2001 to have a 2-members ensemble forecast.
[forecast]
year_members = [2000, 2001]
No rain member
An additional member using a rain-free scenario can be added to the ensemble
by turning the norain key to true.
Default value is false.
[forecast]
norain = false
Quantiles output
By default, Rameau provides river flow and groundwater level forecast
outputs for each member. If the quantiles_output key is set to
true, outputs correspond to quantiles defined by the quantiles key.
Default value to false for quantiles_outputs.
Default values for quantiles are 10%, 20%, 50%, 80% and 90%.
[forecast]
quantiles_output = false
quantiles = [10, 20, 50, 80, 90]
Forecast correction method
Two correction methods are available for the ensemble forecast. The key
correction can be set to one of the following:
“no” does not apply any correction
“halflife” applies a correction to the forecast : the forecast values are corrected to match the observed values on the emission date. The initial correction is then propagated through time by applying a decay factor to the difference between the forecasted and observed values.
Default value is “no”.
[forecast]
correction = "no"
Pumping date to consider
Pumping can be applied to the forecast ensemble members. The pumping_date
key is used to define the date from which to apply the pumping.
[forecast]
pumping_date = 1999-07-01
Forecast correction parameters
Forecast correction parameters correspond to the halflife times of the
output correction method when issuing a forecast. Two keys
forecast.river.halflife and forecast.groundwater.halflife
for river flows and groundwater levels, respectively, can be set for
each watershed of the model. These keys accept float values. A
value of zero means no half-life correction.
Default values are 0.
[watershed.1]
forecast.river.halflife = 2
forecast.groundwater.halflife = 1
[watershed.2]
forecast.river.halflife = 0
forecast.groundwater.halflife = 1
Note that these parameters are taken into account only if the key correction
is set to halflife in the forecast settings.
A full example
The example below set the forecast settings for a 30-day forecast issued on 2009-01-01 using the years 2000 and 2001 as ensemble members. A rain-free scenario is added to the ensemble. The forecast outputs are quantiles 25%, 50%, and 75%. Halflife output method is applied to groundwater level and river flow for watershed 1, and only to river flow for watershed 2.
[forecast]
forecast = true
emision_date = 2009-01-01
scope = { days = 30 }
year_members = [2000, 2001]
norain = true
quantiles_output = true
quantiles = [25, 50, 75]
correction = "halflife"
pumping_date = 1999-07-01
[watershed.1]
forecast.river.halflife = 1
forecast.groundwater.halflife = 1
[watershed.2]
forecast.river.halflife = 2
forecast.groundwater.halflife = 0