Here is a brief overview of the EFAS data made available to the public and registered EFAS users. For a full overview of the EFAS system including its hydrological model LISFLOOD, please go to the dedicated pages on the EFAS web site www.efas.eu. You will find information on the latest releases here: EFAS operational system.
EFAS datasets
EFAS datasets are the time series produced by the operational forecasting system. In turn, those time series are post-processed to produce the forecast products displayed on the EFAS Information System.
Two types of EFAS datasets have been made available: operational medium-range forecasts and historical simulation forced with observations, both described below.
All data is provided as gridded time series data files generated using the latest EFAS operational configuration associated with the release date of the data. Please refer to the EFAS overview for more details on the EFAS modelling chain.
EFAS medium-range forecasts
EFAS forecasts are generated as a combination of Numerical Weather Prediction meteorological forecasts input and a hydrological model. Only EFAS medium-range forecasts, issued twice daily at 00:00UTC and 12:00UTC, are currently made available to the public as data files. Their configurations are detailed in table 1 below (for more details on the meteorological forcings please see https://www.efas.eu/en/meteorological-forecasts).
Table 1: EFAS medium-range forecast configuration
| Forcing | Description | Number of members | Forcing spatial resolution | Lead time | Time step | Comment |
|---|---|---|---|---|---|---|
| ECMWF-HRES | ECMWF high resolution forecast | 1 | ~9km | 10d | 6h | |
| ECMWF-ENS | ECMWF ensemble forecasts | 51 | ~18km | 15d | 24h | Only 24-hourly hydrological simulations are available |
| COSMO-LEPS | COSMO-LEPS ensemble forecasts | 20 | ~7km | 5d | 6h | |
| DWD-Det | COSMO-EU and ICON forecasts | 1 | ~6.5/13km | 1-3/4-7d | 6h | COSMO-EU is used for day1-3, ICON is used for day 4-7 |
| Gridded obs | Simulation forced with observation | 1 | 5km | 24h | 24h | Hydrological simulation used to initialise forecasts, available daily at 06:00UTC. It uses the same configuration as the EFAS operational forecasts and historical simulation forced with observations. |
EFAS Historical simulation forced with observations
EFAS historical simulation forced with observations is a long (at least 20 years) hydrological time series simulation. It is considered as a reference simulation for the system, and is generated every time a new EFAS operational configuration is released. It is used to calculate statistics against which to compare the forecasts, such as river flood magnitude for given return periods, or to verify the performance of the forecasts.
EFAS historical simulation forced with observations (historical SFO) is produced by forcing the EFAS operational modelling chain with consolidated gridded field of observed meteorological variables (precipitation and temperature) over a time period as long as possible; e.g. for EFAS3.0 the EFAS historical simulation spans 1990-2016.
From 2017 onward, simulations forced with observations make use of gridded field of observed meteorological variables from the operational EFAS and are identified as EFAS operational simulations forced with observations (operational SFO).
Users who want to full SFO time series are advised to download both historical SFO and operational SFO and merge them together.
As the initial conditions used to initialise EFAS historical SFO for the first day of the simulation correspond to averaged initial values (the model is so called 'cold-started'), EFAS historical simulation forced with observations is available from 1 January 1991, when the initial conditions don't influence the simulation results.
EFAS upstream area
In order to interpret the EFAS output in a correct way, you will need a number of using static data. These data are part of the EFAS setup of the LISFLOOD model.
This files denotes the total upstream area for each river pixel, describes in m2. This is defined as the catchment area for each river segment, meaning the total area that contributes with water to the river at the specific grid point. The upstream area always includes the area of the pixel. The upstream area is provided in the netCDF file if you retrieve the data from CDS and choose the format netCDF. You can also download the upstream area file as netCDF here:
EFAS variables
EFAS variables (called 'parameters' in ECMWF MARS) are the hydrological entities calculated by the modelling chain.
Three types of EFAS variables have been made available: river discharge, snow depth water equivalent and volumetric soil moisture content. A short description is given below in table 2 along metadata information associated.
Table 1. Available EFAS variables
EFAS Short Description | Unit | GRIB parameter ID | GRIB Short name | GRIB Name | Comment | GRIB description |
|---|---|---|---|---|---|---|
| River discharge | m3/s | 240023/ 240024 | dis06/ dis24 | Mean discharge in the last 6/ 24 hours | Average | Volume rate of water flow, including sediments, chemical and biological material, in the river channel averaged over a time step through a cross-section. |
| Snow depth water equivalent | kg/m2 (mm) | 228141 | sd | Snow depth water equivalent | Instantaneous | Snow depth water equivalent in kg m**-2 (mm) water equivalent |
| Volumetric soil moisture content | m3 /m3 | 260199 | vsw | Volumetric soil moisture | Instantaneous Available for three soil layers | Volumetric soil moisture for a layer |
| Soil depth | m | 260367 | sod | Soil depth | Set of three values. Depth from the surface to the bottom of each layer | Soil depth, positive downward. To be used with the type of level 'soil level' |
River discharge
EFAS variable discharge (dis) is stored as average over the time step of the model (6-hourly or 24-hourly), with time stamp (date and time of end of averaging period) explicit in the GRIB short name.
In EFAS, river discharge is calculated in each hydrological model grid box. However, not all grid boxes correspond to a river segments, and because of the relatively coarse resolution of the EFAS gridded domain, the modelled river network in EFAS might be associated with slightly different latitude-longitude than in the real world. It is hence essential that when extracting river discharge data, the user also checks the upstream area of the grid box of interest. Please look at the EFAS upstream area section on the left.
Some short scripts to use as examples are provided in the how to read EFAS data pages.
Snow depth water equivalent
Snow depth water equivalent is given as an instantaneous value, which represents the amount of water stored as ice and snow at the end of each model time step. The time stamp (date and time of end of averaging period) is explicit in the GRIB short name.
In EFAS, snow depth water equivalent in each grid box is calculated from three elevation-related bands (a, b and c) to account for the difference in the melting rate with snow condition. However, only the more directly usable composite snow map representing the total snow water equivalent for each grid box is made available.
Some short scripts to use as examples are provided in the how to read EFAS data pages.
Volumetric soil moisture content
Soil moisture content is given as an instantaneous value, which represent the amount of water stored in the soil layers at the end of each model time step. The time stamp (date and time of end of averaging period) is explicit in the GRIB short name.
EFAS soil moisture content in each grid box is calculated in three layers, top (1), intermediate (2) and bottom (3), each associated with a given soil depth (depth from top to bottom of that layer). Information for each 3 layers is provided as separate data field, the soil depth.
EFAS soil moisture information is stored as volumetric soil moisture content for each layer. The associated volume of water for that layer is volumetric soil moisture content multiplied by the layer thickness. The thickness of a specific layer is the difference between the depth of two consecutive layers.
The total volume soil moisture content is the sum of volume of water for each layer. Note that in EFAS-IS, only soil moisture of the first 2 layers is shown.
Some short scripts to use as examples are provided in the how to read EFAS data pages.