General maps
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Area mask & land use mask maps.
The mask maps in the hydrological model are used to detect where model should perform computations and where it shouldn’t (skip the grid-cell). Area and land use masks are both Boolean maps which define model boundaries and land use calculation domain respectively. -
Grid-cell length & grid-cell area maps.
The grid-cell length and grid-cell area maps are used in LISFLOOD model to accurately compute the areal sums over grid-cells (e.g. the upstream area of the river when areas of all connected grid-cells are summed together or the rainfall amount over a certain grid-cell). If projection properties are in meters these maps become optional.
Area mask and land use mask maps
General map information and possible source data
| Map name | File name;type | Units; range | Description |
|---|---|---|---|
| Mask map | area.nc; Type: Float32 |
Units: -; Range: NoData or 1 |
Boolean map that defines model boundaries |
| Land use mask | landuse.nc; Type: Float32 |
Units: -; Range: NoData or 1 |
Boolean map for land use calculations |
| Source data | Reference/preparation | Temporal coverage | Spatial information |
|---|---|---|---|
| Any available map of the region of interest (e.g. digital elevation map, flow direction map) |
NA | NA | Global, 1’ and 3’ |
Methodology
To create a mask field (mask map or land use mask), source data (e.g. elevation or flow direction) values are changed to ‘1’ and the variable type is forced to be Byte for the mask map (area.nc), and Float32 for the land use mask (lusemask.nc).
If the source data is at a higher resolution and/or is larger than the required model domain, it needs to be re-scaled to the required grid-cell resolution and/or clipped to the required model domain.
Results (examples)
Figure 1: Mask map at 1 arc min horizontal resolution for European domain (left) and at 3 arc min horizontal resolution for Global domain (right) with coloured areas showing land pixel.
Figure 2: Land use mask map at 1 arc min horizontal resolution for European domain (left) and at 3 arc min horizontal resolution for Global domain (right) with coloured areas showing land pixel.
Grid-cell length and grid-cell area maps
General map information and possible source data
| Map name | File name;type | Units; range | Description |
|---|---|---|---|
| Pixel length | pixleng.nc; Type: Float32 |
Units: -; Range: >0 |
Map with grid-cell (pixel) length along the latitude, the only pixel size to change (along the longitude the length is constant) |
| Pixel area | pixarea.nc; Type: Float32 |
Units: m2; Range: >0 |
Map with grid-cell (pixel) area |
| Source data | Reference/preparation | Temporal coverage | Spatial information |
|---|---|---|---|
| Mask map | Can be prepared following the instructions provided here | NA | Global, 1’ and 3’ |
Methodology
To create the grid-cell area, the ee.Image.pixelArea() function in Google Earth Engine can be used, that computes the value of each grid-cell in square meters considering all curves of the Globe, and specify the needed grids resolution (e.g. 1 and 3 arc min) along the longitude in meters.
Grid-cell length is computed dividing grid-cell area by its resolution along the longitude in meters.
Note: The pixel area and pixel length maps are given to the whole domain (i.e. not applying the ocean mask map).
Results (examples)
Figure 3: Pixel length map at 1 arc min horizontal resolution for European domain (left) and at 3 arc min horizontal resolution for Global domain (right).
Figure 4: Pixel area map at 1 arc min horizontal resolution for European domain (left) and at 3 arc min horizontal resolution for Global domain (right).