In order to interpret CEMS-Flood (EFAS & GloFAS) model outputs in a correct way, you will need a number of auxiliary data, also referred to as the 'time invariant' data on the Climate Data Store (CDS). These data are part of the EFAS and GloFAS setups of the LISFLOOD model. This page summarises the auxiliary datasets made available through the CDS and how they should be used in combination with the model outputs.
EFAS Auxiliary Data
The auxiliary data are provided as small NetCDF files, and are available to download through the Climate Data Store (CDS) on the EFAS pages.
The following five datasets are available:
- Upstream area
- Elevation
- Soil depth (3 soil levels)
- Wilting point (3 soil levels)
- Field capacity (3 soil levels)
For version 4.0 and older they are in the INSPIRE compliant ETRS89 Lambert Azimuthal Equal Area Coordinate Reference System (ETRS-LAEA), also referred to as EPSG:3035. More information on the EFAS horizontal resolution is available in the model output page.
For version 5.0, they are in WGS84.
The Local Drain Direction (LDD) file is also available to download below (in both EPSG:3035 for versions 4.0 and older, and WGS84 for v5.0).
It is important for users to make sure they download the auxiliary data consistent with the dataset version of interest. This is because the auxiliary data sometimes change with a new EFAS cycle; for example, the upstream area is specific to the hydrological model configuration used which can change between cycles.
To provide an example, users accessing forecast data issued between 2019-05-13 and 2020-03-04 should use v3.0 of the auxiliary data, as forecasts issued during that period were produced with EFAS v3.0. All the version dates are shown in the table below:
Versions | For forecast data issued from: |
---|---|
EFAS version 4.0 | 2020-10-14 12 UTC to present |
EFAS version 3.5 | 2020-03-05 12 UTC and 2020-10-13 12 UTC |
EFAS version 3.0 | 2019-05-13 12 UTC and 2020-03-04 12 UTC |
EFAS version 2.0 | before 2019-05-13 12 UTC |
The upstream area file denotes the total upstream area for each river pixel, expressed in m2. It is defined as the catchment area for each river segment, i.e. the total area that contributes with water to the river at the specific grid point (or river pixel). The upstream area always includes the area of the pixel it is associated to.
The elevation (sometimes referred to as orography) file denotes the mean elevation for each pixel in the EFAS domain, expressed in m above sea level. It is defined for each grid point of the modelled domain.
The files for soil depth, wilting capacity, and field capacity are collectively known as the 'soil wetness index' files, and contain all the relevant information to calculate the soil wetness index from the volumetric soil moisture dataset model output. They are provided separately for each of the three soil layers represented in LISFLOOD.
They are defined as follows:
- Soil depth: The soil depth for each of the three soil layers at each grid point. The value is relative from the top of the land surface to the bottom of each layer respectively.
- Wilting point: The minimal amount of water in the soil that the plant requires not to wilt. If the soil water content decreases to this or any lower point a plant wilts and can no longer recover its turgidity when placed in a saturated atmosphere for 12 hours.
- Field capacity: The amount of soil moisture or water content held in the soil after excess water has drained away and the rate of downward movement has decreased.
More detail on the datasets and how they should be used to derive the soil moisture index is provided here.
The Local Drain Direction (LDD) in a hydrological model is the essential component to connect the grid cells in order to express the flow direction from one cell to another, and forming a river network from the springs to the mouth. LDD represents flow directions from each grid-cell to its steepest down-slope neighbor.
Geographical directions in the LDD file are coded with values from "1" to "9", with "5" representing pits (grid-cells with only inflow of water).
Download the LDD file for EFAS v4.0 and earlier here: ldd_efas.nc (1MB)
Download the LDD file for EFAS v5.0 here: ldd_efas_5.0.nc
GloFAS Auxiliary Data
The auxiliary data for GloFAS are provided as NetCDF files in WGS 84 (EPSG:4326), and are available to download below.
Three datasets are available to download:
- Upstream area
- Elevation
- The Local Drain Direction (LDD)
The three datasets provided here are applicable for GloFAS version 4.0, and can be used for forecasts produced from 2023-07-26 onwards.
For forecasts produced earlier than 2023-07-26, using GloFAS versions 1.0 to version 3.4, the appropriate auxiliary files can be viewed and downloaded by clicking the expand panel.
The upstream area file denotes the total upstream area for each river pixel, expressed in m2. The upstream area is defined as the catchment area for each river segment, in other words, the total area that contributes water to the river at the specific grid point. The upstream area always includes the area of the pixel.
Download the upstream area file here: uparea_glofas_v4_0.nc (87MB)
The elevation (sometimes referred to as orography) file denotes the mean elevation for each pixel in the GloFAS domain, expressed in m above sea level. It is defined for each grid point of the modelled domain.
Download the elevation file here: elevation_glofas_v4_0.nc (87MB)
The Local Drain Direction (LDD) in a hydrological model is the essential component to connect the grid cells in order to express the flow direction from one cell to another, and forming a river network from the springs to the mouth. LDD represents flow directions from each grid-cell to its steepest down-slope neighbor.
Geographical directions in the LDD file are coded with values from "1" to "9", with "5" representing pits (grid-cells with only inflow of water).
Download the LDD file here: ldd_glofas_v4_0.nc (21MB)