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Environment Parameters

The EnvironmentParameters JSON object defines environmental conditions used by MONICA, including atmospheric gas concentrations, groundwater dynamics, surface albedo, wind measurement height, nitrate leaching depth, and the numerical timestep factor used by several soil process modules.

In a MONICA site configuration, these values normally appear under the EnvironmentParameters property.

List of environment parameters

Parameter Name Type Unit Description Example
Albedo Number Fraction of incoming shortwave radiation reflected by the surface. The physically meaningful range is 0 (fully absorbed) to 1 (fully reflected). "Albedo": 0.23
rcp String or Number Representative Concentration Pathway used to estimate atmospheric CO2 when neither climate data, a year-specific value, nor a positive fixed concentration is available. Supported scenarios are rcp19, rcp26, rcp34, rcp45, rcp60, rcp70, and rcp85. "rcp": "rcp85"
AtmosphericCO2 Number ppm Fixed atmospheric CO2 concentration. Used when climate data contain no CO2 value and AtmosphericCO2s contains no entry for the current year. Set to 0 to enable RCP-based calculation. "AtmosphericCO2": 0
AtmosphericCO2s Object ppm Mapping from calendar years to atmospheric CO2 concentrations. Year-specific values take precedence over AtmosphericCO2 and the RCP calculation, but not over CO2 supplied by climate data. "AtmosphericCO2s": {}
AtmosphericO3 Number ppb Fixed atmospheric ozone concentration. Used when climate data contain no ozone value and AtmosphericO3s contain no entry for the current year. "AtmosphericO3": 0
AtmosphericO3s Object ppb Mapping from calendar years to atmospheric ozone concentrations. Year-specific values take precedence over AtmosphericO3, but not over ozone supplied by climate data. "AtmosphericO3s": {}
LeachingDepth Number m Soil depth used to evaluate nitrate leaching and the associated lower-boundary water flux. It should be consistent with the depth and layer structure of the simulated soil profile. "LeachingDepth": 1.6
MaxGroundwaterDepth Number m below surface Maximum annual groundwater depth below the soil surface. This is the deepest position of the groundwater table and should normally be greater than or equal to MinGroundwaterDepth. "MaxGroundwaterDepth": 1.0
MinGroundwaterDepth Number m below surface Minimum annual groundwater depth below the soil surface. This is the shallowest position of the groundwater table and is reached approximately during MinGroundwaterDepthMonth. "MinGroundwaterDepth": 0.5
MinGroundwaterDepthMonth Integer month Month during which the seasonal groundwater curve approximately reaches MinGroundwaterDepth. Use values from 1 to 12. "MinGroundwaterDepthMonth": 3
WindSpeedHeight Number m above ground Height at which the input wind speed was measured. MONICA uses this value when converting wind speed for evapotranspiration calculations. "WindSpeedHeight": 2
timeStep Number d Numerical time-step factor used by several soil processes calculations, including soil temperature, soil moisture and frost, and nitrate transport. Use 1 with standard daily climate data. Note: This parameter does not change the calendar interval of the main simulation loop. "timeStep": 1
type String Declares that this JSON defines environment parameters "type": "EnvironmentParameters"

Atmospheric CO2 selection

For every simulation date, MONICA selects atmospheric CO2 using the following precedence:

  1. CO2 supplied directly by the climate data.
  2. The value in AtmosphericCO2s for the current calendar year.
  3. An RCP-derived concentration when the fixed AtmosphericCO2 value does not enable a fixed concentration.
  4. The fixed value in AtmosphericCO2.

For normal configurations, set AtmosphericCO2 to:

  • a realistic positive concentration, such as 400, to use a fixed value,
  • or 0 to enable RCP-based calculation.

Example

{
    "rcp": "rcp45",
    "AtmosphericCO2": 0,
    "AtmosphericCO2s": {
        "2020": 412,
        "2021": 414
    }
}

In this example:

  • Climate data CO2 takes precedence whenever it is present.
  • 412 ppm is used in 2020 when climate data CO2 is absent.
  • 414 ppm is used in 2021 when climate data CO2 is absent.
  • For other years, MONICA calculates CO2 from the rcp45 trajectory.

Atmospheric ozone selection

MONICA selects atmospheric ozone using the following precedence:

  1. Ozone supplied directly by the climate data.
  2. The value in AtmosphericO3s for the current calendar year.
  3. The fixed value in AtmosphericO3.

Unlike CO2, atmospheric ozone is not calculated from the selected RCP scenario.

Groundwater dynamics

For each simulation date, MONICA first checks whether measured groundwater information is available for that exact date. Measured groundwater information is configured separately from the EnvironmentParameters object. When a measured value is available, MONICA uses it. Otherwise, it calculates groundwater depth from an annual sinusoidal curve defined by:

  • MaxGroundwaterDepth
  • MinGroundwaterDepth
  • MinGroundwaterDepthMonth

MinGroundwaterDepthMonth specifies approximately when the curve reaches MinGroundwaterDepth, the shallowest groundwater position. The curve reaches MaxGroundwaterDepth, the deepest position, approximately six months later. MaxGroundwaterDepth should therefore normally be greater than or equal to MinGroundwaterDepth.

Groundwater depth terminology

Groundwater depth is measured downward from the soil surface. A larger numerical value therefore represents a deeper groundwater table.

For example:

{
    "MaxGroundwaterDepth": 1.0,
    "MinGroundwaterDepth": 0.5,
    "MinGroundwaterDepthMonth": 3
}

The calculated groundwater depth is approximately 0.5 m in March and approximately 1.0 m six months later.

Example: environment.json

{
    "Albedo": 0.23,
    "rcp": "rcp85",
    "AtmosphericCO2": 0,
    "AtmosphericCO2s": {},
    "LeachingDepth": 1.6,
    "MaxGroundwaterDepth": 1.0,
    "MinGroundwaterDepth": 0.5,
    "MinGroundwaterDepthMonth": 3,
    "WindSpeedHeight": 2,
    "timeStep": 1,
    "type": "EnvironmentParameters"
}