Climate under Cover
Digital Dynamic Simulation in Plant Bio-Engineering

Soil CO2 and Water Toolset

Soil CO2 Diffusion and Water Transport

This page converts CUC70, CUC70SUP, and CUC90 into browser-based tools for soil CO2 concentration, interpolation support, and coupled soil water transport.

The page keeps the original lookup-table comparison structure and provides browser-based interactive charts for Matlab cross-checking.

MATLAB sources are preserved in matlab-source/cuc70_122, including co2insoil.m, soil90.m, and cuc70sup.m.

CUC70

Soil temperature and CO2 concentration

Recreates the coupled temperature and soil CO2 concentration profile, with diffusion coefficient DS as the main comparison variable.

CUC70SUP

Interpolation methods for soil CO2 generation

Shows the support interpolation example used to explore the temperature-to-CO2-generation lookup table in CUC70.

CUC90

Temperature and water regimes in the soil layer

Simulates the coupled soil temperature profile and volumetric water content, including vapor diffusion, liquid flow, and water potential effects.

Water vapor diffusivity and hydraulic conductivity as functions of volumetric water content.

Water potential as a function of volumetric water content.

Implementation

Model structure

  • CUC70 and CUC90 keep the coupled state-variable structure used in the MATLAB examples.
  • CUC70 simulate CO2 concentration in the soil layer. Generation in each layer is assumed as a function of temperature.
  • CUC70SUP compares nearest, linear, cubic, and spline interpolation against the original lookup points.
  • CUC90 To simulate temperature and water regimes in the soil layer. Water vapor diffusivity, Hydraulic conductivity and Water potential are assumed function of volumetric water content.

Formula Notes

Key relations and symbols

  • gen1 = 0.001 * interpNearest(T1, xtemp, yco2) is a representative CO2-generation term; interpNearest uses the original lookup table from temperature to generation coefficient.
  • IC1 = [2*DS(CCF - C1)/Z + DS(C2 - C1)/Z] / Z + gen1 is the top-layer CO2-balance equation, where DS is diffusion coefficient and Z is layer thickness.
  • WO = FWS(TD) sets the humidity-ratio boundary in CUC90, where TD is outside dew point in °C and WO is in kg/kg.
  • C1 to C5 are soil CO2 concentrations (nondimensional in the original example), T1 to T5 are temperatures in °C, and DS is in m²/hr.
  • CCF is surface CO2 boundary concentration, Z is soil-layer thickness in m, gen1 is the volumetric source term, FWS returns humidity ratio in kg/kg, and xtemp and yco2 are the lookup-table axes from the original Matlab example.
  • DWV(WW) = 3.6 * interpLinear(WW, xtemp, ytemp) gives the water-vapor diffusivity curve used in the first CUC90 property chart.
  • K(WW) = interpLinear(WW, xtemp, ytemp) and WP(WW) = -AFGEN_STB(WW) / 100 give hydraulic conductivity and water potential as functions of volumetric water content.