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Albedo, fAPAR, Land Surface Temperature, Light Use Efficiency (LUE), NDVI , Precipitation, Solar radiation, Statics and Weather data

Static Inputs

Static inputs are spatially varying, temporally static (global) maps.

WaPOR

Topography is an important land surface characteristic. Elevation, slope and aspect have a large impact on weather conditions and incoming solar radiation.

The Copernicus DEM is used to generate information on surface characteristics required for the algorithms. Elevation is an input to calculate the air temperature and solar radiation parameters. The latter also uses slope and aspect to calculate local levels of solar radiation.

Table 13: Overview of the intermediate data components related to elevation

Data component	Unit	Use	Temporal resolution
Elevation	M	Used to correct for meteorological effects in mountainous areas, and to retrieve surface characteristics	Static
Slope Rad	0-π	Used to calculate local solar radiation	Static
Aspect Rad	0-2π	Used to calculate local solar radiation	Static
Latitude, Longitude	rad	Used for radiation calculations	Static

The previous WaPOR versions used the digital elevation model (DEM) created by the Shuttle Radar Topography Mission (SRTM) at a resolution of 90m. For version 3 the Copernicus DEM GLO-30 (level 3) and GLO-90 (level 2) collections are used.

ETLook uses the following spatially varying, temporally static global maps:

Parameter	Description and link	Comment
lwoffset	Longwave radiation offset	Variable in FAO-56. Globally calibrated parameter, calibration updated with ERA5 for version 3
lwslope	Longwave radiation slope	Variable in FAO-56. Globally calibrated parameter, calibration updated with ERA5 for version 3
r0_bare	Soil moisture calculation	In the original Yang paper this is a constant. For WaPOR this has been calculated as the albedo value which coincides with the lowest NDVI value for the period of 2018-2022 (using Sentinel-2 for L2 and L3, and VIIRS for L1).
r0_full	Soil moisture calculation	In the original Yang paper this is a constant. For WaPOR this has been calculated as the albedo value which coincides with the highest NDVI value for the period of 2018-2022 (using Sentinel-2 for L2 and L3, and VIIRS for L1).
rn_offset	Soil heat water storage	Relationship is based on MERRA data of net radiation. It makes sure that the yearly soil heat water storage is equal to zero.
rn_slope	Soil heat water storage	Relationship is based on MERRA data of net radiation. It makes sure that the yearly soil heat water storage is equal to zero.
rs_min	Bulk stomatal resistance	Values are attributed to land cover.
t_amp_year [C]	Yearly air temperature amplitude used for calculation of the soil heat flux	The yearly amplitude for air temperature is based on climatological data and used for the seasonal changes of heat storage in the soil
t_opt [C]	Yearly air temperature amplitude optimum, a parameter for the temperature stress function	The Jarvis optimum temperature is defined as the optimum temperature for plant stomatal conductance. Is based on the most common air temperature based on climate dataset
vpd_slope	Parameter for the vapour stress function	The slope coefficient of the vapour pressure deficit stress curve
z_obst_max [m]	Used for calculating surface roughness length	Values are attributed to land cover.It takes into account the effect of a growing vegetation due to the relationship with NDVI.
z_oro [m]	Used for calculating surface roughness length	Values are attributed to the terrain. It takes into account the topographic relief of the Earth's surface.
z_coarse [m]	Used to correct the air temperature for the elevation by calculating the local difference between the actual elevation and coarse elevation.

The static layers can be found in the repository