The site.json configuration file
site.json holds all input data and parameters that can be considered site-specific. Besides the key SiteParameters in the top-level JSON object, there might be a few JSON objects that set global or general soil and environment-specific parameters. These can either be included from the SQLite database (table user_parameter), from the filesystem, or defined directly in site.json. To facilitate easy overwriting of the standard parameters, they are included via the DEFAULT parameter pseudo-key.
The soil profile
The key SoilProfileParameters contains a JSON array of JSON objects that describe the layers of the soil profile. MONICA internally uses 20 layers, each with a 10 cm thickness. SoilProfileParameters must contain at least one layer with a minimal set of soil properties (KA5TextureClass, SoilOrganicCarbon/SoilOrganicMatter, and SoilRawDensity/SoilBulkDensity). Additionally, each layer needs a Thickness key describing the height of the soil layer. The specified soil profile will be internally normalized to 20 layers of 10 cm each. If the total thickness of the layers does not add up to 2 m (MONICA's used profile depth), the last layer will be extended up to 2 m. Likewise, layers extending beyond 2 m will be cut at that depth.
Not all properties are required, but the more soil properties are specified, the more accurate the calculations will be. If only the KA5TextureClass is given, average values for Sand and Clay content will be used, and FieldCapacity, PermanentWiltingPoint, PoreVolume, and Lambda will be calculated based on them.
Only one of SoilRawDensity and SoilBulkDensity, as well as one of SoilOrganicCarbon and SoilOrganicMatter, must be provided. If both values are being supplied, they should match.
The following table shows the names of the soil properties that can be set for an individual layer.
| Name of config file variable | Unit | Description |
|---|---|---|
| Thickness | m | Thickness of the soil layer |
| Sand | kg kg-1 (fraction [0-1]) | Soil sand content, a fraction between 0 and 1 |
| Clay | kg kg-1 (fraction [0-1]) | Soil clay content, a fraction between 0 and 1 |
| pH | Soil pH value | |
| Sceleton | fraction [0-1] | Soil stone content, a fraction between 0 and 1 |
| Lambda | Soil water conductivity coefficient | |
| FieldCapacity | m3 m-3 (fraction [0-1]) | Field capacity |
| PoreVolume | m3 m-3 (fraction [0-1]) | Saturation |
| PermanentWiltingPoint | m3 m-3 (fraction [0-1]) | Permanent wilting point |
| KA5TextureClass | KA5 soil texture class | |
| SoilAmmonium | kg NH4-N m-3 | Initial soil ammonium content |
| SoilNitrate | kg NO3-N m-3 | Initial soil nitrate content |
| CN | Soil C/N ratio | |
| SoilRawDensity | kg m-3 | Soil raw density |
| SoilBulkDensity | kg m-3 | Soil bulk density |
| SoilOrganicCarbon | % [0-100] ([kg C kg-1] * 100) | Soil organic carbon, a percentage between 0 and 100 |
| SoilOrganicMatter | kg OM kg-1 (fraction [0-1]) | Soil organic matter |
| SoilMoisturePercentFC | % [0-100] | Initial soil moisture in percent of field capacity |
Further site-specific variables:
| Name of config file variable | Unit | Description |
|---|---|---|
| Latitude | [decimal degrees] | Site's latitude |
| Slope | [height m * length m-1] [0-1] | Site's slope |
| HeightNN | [m] | Site's height above sea level |
| NDeposition | N deposition via atmosphere |
Environment parameters for the whole simulation
The following environment parameters for the entire simulation can be adjusted by referencing either the appropriate JSON file or selectively overwriting parameters read from the default file.
Atmospheric CO2 (O3) handling logic
Currently, the following procedure is applied:
- Check if co2 or o3 field is present in the daily climate data. If so, use the supplied values.
- If the parameter
AtmosphericCO2s(AtmosphericO3s) is set to a JSON object mapping of "year" to "CO2 value", use these yearly values. - If the parameter
AtmosphericCO2(AtmosphericO3) is set to 0 or a negative value, let MONICA calculate the CO2 concentration depending on the year. - If none of the above apply, use the value of
AtmosphericCO2(AtmosphericO3) for the entire simulation.
Environment parameter table
| Name of parameter | Unit | Default value | Description |
|---|---|---|---|
| Albedo | 0.23 | Surface reflectivity coefficient | |
| AtmosphericCO2 | ppm | 0.0 | Atmospheric CO2 concentration |
| AtmosphericCO2s | ppm | unset | Example value: {"1991": 360, "1992": 370, "1993": 380} |
| AtmosphericO3, | ppm | 0.0 | Atmospheric O3 concentration |
| AtmosphericO3s | ppm | unset | |
| WindSpeedHeight | m | 2.0 | Height above ground surface at which wind speed is measured |
| LeachingDepth | m | 0.0 | Depth below ground surface at which water and nitrate outflow is determined |
| MaxGroundwaterDepth | m | 18.0 | Maximum annual groundwater depth below the ground surface |
| MinGroundwaterDepth | m | 20.0 | Minimum annual groundwater depth below the ground surface |
| MinGroundwaterDepthMonth | 3.0 | Month in which the minimum average groundwater depth below ground surface is observed |
Example site.json file
The following example shows a typical site.json configuration defining key site parameters such as latitude, slope, and soil profile properties. It also demonstrates how to include external parameter files for soil, environment, and transport processes using the include-from-file directive.
{
"SiteParameters": {
"Latitude": 52.80939865112305,
"Slope": 0.1,
"HeightNN": [0 , "m"],
"NDeposition": 30,
"SoilProfileParameters": [
{
"Thickness": 0.3,
"SoilOrganicCarbon": [0.8, "%"],
"KA5TextureClass": "Sl2",
"SoilRawDensity": ["ld_eff2trd", 2, ["KA5TextureClass2clay", "Sl2"]],
"Lambda": ["sandAndClay2lambda", ["KA5TextureClass2sand", "Sl2"], ["KA5TextureClass2clay", "Sl2"]]
},
{
"Thickness": 0.1,
"SoilOrganicCarbon": [0.15, "%"],
"KA5TextureClass": "Sl2",
"SoilRawDensity": ["ld_eff2trd", 2, ["KA5TextureClass2clay", "Sl2"]]
},
{
"Thickness": 1.6,
"SoilOrganicCarbon": [0.05, "%"],
"KA5TextureClass": "Sl2",
"SoilRawDensity": ["ld_eff2trd", 2, ["KA5TextureClass2clay", "Sl2"]]
}
]
},
"SoilTemperatureParameters": ["include-from-file", "../monica-parameters/user-parameters/hermes-soil-temperature.json"],
"EnvironmentParameters": {
"DEFAULT": ["include-from-file", "../monica-parameters/user-parameters/hermes-environment.json"],
"LeachingDepth": 2.0,
"WindSpeedHeight": 2.5
},
"SoilOrganicParameters": ["include-from-file", "../monica-parameters/user-parameters/hermes-soil-organic.json"],
"SoilTransportParameters": ["include-from-file", "../monica-parameters/user-parameters/hermes-soil-transport.json"],
"SoilMoistureParameters": ["include-from-file", "../monica-parameters/user-parameters/hermes-soil-moisture.json"]
}