RUFAS.routines.field.soil.soil_temp module

class RUFAS.routines.field.soil.soil_temp.SoilTemp(soil_data: SoilData | None, field_size: float | None = None)

Bases: object

Manages and simulates soil temperature based on the “Soil Temperature” section (1:1.3.3) of the Soil and Water Assessment Tool (SWAT) documentation.

Parameters

soil_dataSoilData, optional

The SoilData object used by this module to track the temperatures within the soil profile, creates new one if one is not provided.

field_sizefloat, optional

Used to initialize a SoilData object for this module to work with, if a pre-configured SoilData object is not provided (ha).

__init__(soil_data: SoilData | None, field_size: float | None = None)

daily_soil_temperature_update(solar_radiation: float, avg_temp: float, min_temp: float, max_temp: float, plant_cover: float, snow_cover: float, avg_annual_air_temp: float) → None

Update the soil temperature.

Parameters

solar_radiationfloat

Solar radiation reaching the ground on the current day (MJ per square meter per day).

avg_tempfloat

Average temperature of the current day (degrees C).

min_tempfloat

Minimum temperature of the current day (degrees C).

max_tempfloat

Maximum temperature of the current day (degrees C).

plant_coverfloat

Total aboveground plant biomass and residue on the current day (kg per hectare).

snow_coverfloat

Water content of the snow cover on the current day (mm).

avg_annual_air_tempfloat

Average annual air temperature (degrees C).

Notes

SWAT does not specify how to start the simulation i.e. it does not specify what to do on day 0, when there is no previous day’s temperature. Currently, the implementation just uses the temperature that the soil starts (it sets the previous day’s temperature equal to the current day’s temperature). This assumption is fairly reasonable due to temporal auto-correlation, but does not account for the random fluctuations that can occur throughout the year.

References

SWAT Theoretical documentation eqn. 1:1.3.3

static _determine_maximum_damping_depth(bulk_density: float) → float

Calculate the maximum damping depth of a soil profile based on bulk density.

Parameters

bulk_densityfloat

The soil profile bulk density (Mg per cubic meter).

Returns

float

The maximum damping depth (mm).

References

SWAT Theoretical documentation eqn. 1:1.3.6

static _determine_scaling_factor(soil_water_content: float, bulk_density: float, bottom_depth: float) → float

Calculate the scaling factor for use in calculating the damping depth.

Parameters

soil_water_contentfloat

Amount of water in the soil profile expressed as depth of water in profile (mm).

bulk_densityfloat

Bulk density of the soil profile (Mg per cubic meter).

bottom_depthfloat

Depth from the soil surface of the bottom of the soil profile (mm).

Returns

float

The scaling factor for calculating damping depth (unitless).

References

SWAT Theoretical documentation eqn. 1:1.3.7

static _determine_damping_depth(max_damping_depth: float, scaling_factor: float) → float

Calculate the daily value for the damping depth.

Parameters

max_damping_depthfloat

Maximum damping depth (mm).

scaling_factorfloat

Scaling factor for soil water (unitless).

Returns

float

Damping depth for the day (mm).

References

SWAT Theoretical documentation eqn. 1:1.3.8

static _determine_depth_factor(center_depth: float, damping_depth: float) → float

Calculate the depth factor for a given layer of soil.

Parameters

center_depthfloat

Depth of the center of a given soil layer (mm).

damping_depthfloat

Damping depth of the soil profile (mm).

Returns

float

The depth factor for this layer of soil (unitless).

References

SWAT Theoretical documentation eqn. 1:1.3.4, 5

static _determine_radiation_factor(solar_radiation: float, albedo: float) → float

Calculate the radiation term for use in calculating the bare soil surface temperature.

Parameters

solar_radiationfloat

Solar radiation reaching the ground on the current day (MJ per square meter per day).

albedofloat

Proportion of solar radiation that is reflected by the soil surface (unitless).

Returns

float

The radiation factor for the day (unitless).

References

SWAT Theoretical documentation eqn. 1:1.3.10

static _determine_bare_soil_surface_temp(radiation_factor: float, avg_temp: float, min_temp: float, max_temp: float) → float

Calculate the temperature at the surface of bare soil.

Parameters

radiation_factorfloat

Radiation factor for a given day (unitless).

avg_tempfloat

Average temperature of the current day (degrees C).

min_tempfloat

Minimum temperature of the current day (degrees C).

max_tempfloat

Maximum temperature of the current day (degrees C).

Returns

float

Bare soil surface temperature (degrees C).

References

SWAT Theoretical documentation eqn. 1:1.3.9

static _determine_cover_weighting_factor(plant_cover: float, snow_cover: float) → float

Calculate the weighting factor for use in calculating the soil surface temperature.

Parameters

plant_coverfloat

Total aboveground plant biomass and residue on the current day (kg per hectare).

snow_coverfloat

Water content of the snow cover on the current day (mm).

Returns

float

Weighting factor based on either snow or plant matter soil cover (unitless).

References

SWAT Theoretical documentation eqn. 1:1.3.11

static _determine_soil_surface_temp(cover_weighting_factor: float, previous_top_soil_layer_temp: float, bare_soil_surface_temp: float) → float

Calculate the soil surface temperature for a given day.

Parameters

cover_weighting_factorfloat

Weighting factor for soil cover impacts (unitless).

previous_top_soil_layer_tempfloat

Temperature of the first layer of soil on the previous day (degrees C).

bare_soil_surface_tempfloat

Temperature of the bare soil surface (degrees C).

Returns

float

Soil surface temperature for the current day (degrees C).

References

SWAT Theoretical documentation eqn. 1:1.3.12

static _determine_average_soil_temperature(prev_temperature_effect: float, previous_day_soil_temp: float, depth_factor: float, avg_annual_air_temp: float, soil_surface_temp: float) → float

Calculate the daily average soil temperature at the center of a given soil layer.

Parameters

prev_temperature_effectfloat

Coefficient that controls the influence of the previous day’s temperature on the current day’s temperature (unitless).

previous_day_soil_tempfloat

Soil temperature in the layer from the previous day (degrees C).

depth_factorfloat

Factor that quantifies the influence of depth below the surface on soil temperature (unitless).

avg_annual_air_tempfloat

Average annual air temperature (degrees C).

soil_surface_tempfloat

Soil surface temperature on the current day (degrees C).

Returns

float

Soil temperature at the given depth on the current day (degrees C).

References

SWAT Theoretical documentation eqn. 1:1.3.3