Each variable is computed using terra,
stars and/or gdalwarp. In the following table
only others packages or functions are mentioned.
Solar radiation is calculated on equinox day (20th March).
Protected area are extracted from protectedplanet.net, enable to extract only countries.
| Name | Unit | Description | Particular package or function | Source |
|---|---|---|---|---|
| elevation | m | Elevation | gdalbuildvrt | srtm.csi.cgiar.org |
| aspect | degrees | Aspect | gdaldem slope | srtm.csi.cgiar.org |
| roughness | m | Roughness is the largest inter-cell difference of a central pixel and its surrounding cell, as defined in Wilson et al (2007, Marine Geodesy 30:3-35) | gdaldem roughness | srtm.csi.cgiar.org |
| slope | degrees | slope values are in degrees | gdaldem slope | srtm.csi.cgiar.org |
| srad | \(Wh.m^{-2}\) | Solar irradiance : computes direct, diffuse and reflected solar irradiation from elevation, slope, roughness, aspect | rgrass (r.in.gdal, r.out.gdal, r.sun) | |
| SoilType | category | Types of soils according to World Reference Base (2006) Soil Groups | gdalbuildvrt gdal_translate | soilgrids.org |
| forest | binary | Forest/No forest layer | gdal_translate | forestatrisk.cirad.fr |
| distanceForest | m | Minimal distance to forest | gdal_proximity | forestatrisk.cirad.fr |
| distanceSea | m | Minimal distance to sea compute from elevation layer | gdal_proximity | elevation layer |
| distanceRoad | m | Minimal distance to any road bigger than terciary road
define on openstreetmap.org
|
osmextract ogr2ogr gdal_proximity | openstreetmap.org |
| distancePlace | m | Minimal distance to cities, town and village | osmextract ogr2ogr gdal_proximity | openstreetmap.org |
| distancewater | m | Minimal distance to river, lake, or reservoir (except sewage and water storage) | osmextract ogr2ogr gdal_proximity | openstreetmap.org |
| WDPA | category | Protected areas (all type of protection) | httr | protectedplanet.net |
| tas | °C x 10 | Daily mean air temperature at 2 metres from hourly ERA5 data for each month | chelsa-climate.org | |
| tasmin | °C x 10 | Daily minimum air temperature at 2 metres from hourly ERA5 data for each month | chelsa-climate.org | |
| tasmax | °C x 10 | Daily maximum air temperature at 2 metres from hourly ERA5 data for each month | chelsa-climate.org | |
| pr | \(kg.m^{-2}\) | Precipitation amount | chelsa-climate.org | |
| clt | % | Cloud area fraction | chelsa-climate.org | |
| pet_penman | \(kg.m^{-2}\) | Potential evapotranspiration calculated with the Penman-Monteith equation. | chelsa-climate.org | |
| pet_thornthwaite | \(kg.m^{-2}\) | Potential evapotranspiration calculated with the Thornthwaite equation. | chelsa-climate.org | |
| cwd_penman | \(kg.m^{-2}\) | Climatic Water Deficit calculated with pet_penman variable | chelsa-climate.org | |
| cwd_thornthwaite | \(kg.m^{-2}\) | Climatic Water Deficit calculated with pet_thornthwaite variable | chelsa-climate.org | |
| ndm_penman | month | Number of Dry Month calculated with cwd_penman variable | chelsa-climate.org | |
| ndm_thornthwaite | month | Number of Dry Month calculated with cwd_thornthwaite variable | chelsa-climate.org | |
| bio1 | °C x 10 | mean annual daily mean air temperatures averaged over 1 year | chelsa-climate.org | |
| bio2 | °C x 10 | mean diurnal range of temperatures averaged over 1 year | chelsa-climate.org | |
| bio3 | °C x 10 | ratio of diurnal variation to annual variation in temperatures | chelsa-climate.org | |
| bio4 | °C x 10 | standard deviation of the monthly mean temperatures | chelsa-climate.org | |
| bio5 | °C x 10 | The highest temperature of any monthly daily mean maximum temperature | chelsa-climate.org | |
| bio6 | °C x 10 | The lowest temperature of any monthly daily mean maximum temperature | chelsa-climate.org | |
| bio7 | °C x 10 | Annual range of air temperature : the difference between the Maximum Temperature of Warmest month and the Minimum Temperature of Coldest month | chelsa-climate.org | |
| bio8 | °C x 10 | Mean daily mean air temperatures of the wettest quarter | chelsa-climate.org | |
| bio9 | °C x 10 | Mean daily mean air temperatures of the driest quarter | chelsa-climate.org | |
| bio10 | °C x 10 | Mean daily mean air temperatures of the warmest quarter | chelsa-climate.org | |
| bio11 | °C x 10 | Mean daily mean air temperatures of the coldest quarter | chelsa-climate.org | |
| bio12 | \(kg.m^{-2}.year^{-1}\) | Accumulated precipitation amount over 1 year | chelsa-climate.org | |
| bio13 | \(kg.m^{-2}.month^{-1}\) | The precipitation of the wettest month. | chelsa-climate.org | |
| bio14 | \(kg.m^{-2}.month^{-1}\) | The precipitation of the driest month. | chelsa-climate.org | |
| bio15 | \(kg.m^{-2}\) | Precipitation seasonality | chelsa-climate.org | |
| bio16 | \(kg.m^{-2}.month^{-1}\) | Mean monthly precipitation amount of the wettest quarter | chelsa-climate.org | |
| bio17 | \(kg.m^{-2}.month^{-1}\) | Mean monthly precipitation amount of the driest quarter | chelsa-climate.org | |
| bio18 | \(kg.m^{-2}.month^{-1}\) | Mean monthly precipitation amount of the warmest quarter | chelsa-climate.org | |
| bio19 | \(kg.m^{-2}.month^{-1}\) | Mean monthly precipitation amount of the coldest quarter | chelsa-climate.org |
\[\lambda ET = \frac{\Delta (R_n - G) + \rho_a c_p \frac{(e_s - e_a)}{r_a}}{\Delta + \gamma (1 + \frac{r_s}{r_a})} \]
where R_n is the net radiation, G is the soil heat flux, (e_s - e_a) represents the vapour pressure deficit of the air, r_a is the mean air density at constant pressure, c_p is the specific heat of the air, \(\Delta\) represents the slope of the saturation vapour pressure temperature relationship, \(\gamma\) is the psychrometric constant, and r_s and r_a are the (bulk) surface and aerodynamic resistances.
\(PET_k\) is the estimated potential evapotranspiration (in mm/month) for month \(k\). \(T_k\) is the average daily temperature (in degrees Celsius) for month \(k\). \(L_k\) is the average day length (in hours) of the month \(k\). \(N_k\) is the number of days for month \(k\). \(I\) is a heat index which depends on the 12 monthly mean temperatures.
\[ I = \Sigma^{12}_{i = 1} (\frac{T_i}{5})^{1.514}\] \[ \alpha = (6.75e-7) I^3 - (7.71e-5) I^2 + (1.792e-2) I + 0.49239 \] \[ PET_k = 16 \frac{L_k}{12} \frac{N_k}{30} \left(\frac{10 T_k}{I}\right)^{\alpha} \]
Climatic Water Deficit (CWD) is the sum of monthly differences between potential evapotranspiration and precipitation. CWD is a positive value. A higher value of CWD indicates a higher deficit in water. The minimal monthly value of CWD is set to 0 when there is more precipitation than potential evapotranspiration and thus no water deficit.
\[ cwd = \Sigma^{12}_{i = 1} max(pet_i - pr_i, 0) \]