Start | Index | Overview • PREV | UP | NEXT The actual \(CO_2\) concentration in the atmosphere is calculated by a linear function based on the \(CO_2\) concentration (cStartValue) in the start year (cStartYear) and the slope (cSlope).
\[ \begin{equation} CO_2(Year) = Slope \cdot (Year-StartYear) + StartValue \label{co2} \end{equation} \]Transpiration is reduced by a factor \(f(CO_2)\) that depends linearly on the actual \(CO_2\) concentration by:
\[ \begin{eqnarray} f(CO_2) & = & Transpiration\_m \cdot CO_2 + Transpiration\_b \label{fco2}\\ ReducedActualTranspiration & = & ActualTranspiration \cdot f(CO_2(year)) \label{redtrans} \end{eqnarray} \]where \Transpiration\_m\ and \Transpiration\_b\ are the slope and the intercept of the linear function being set to 1.1. and -0.0003 respectively by default. The reduced actual transpiration is calculated by multiplying the actual transpiration as determined by crop water demand and soil water supply with the reduction factor \(f(CO_2)\). This value of reduced actual transpiration is then compared with the potential crop transpiration PTRAN to calculate crop water stress (TRANRF) (e.g. in the SimComponent lintul.LintulWaterStress and the impact on crop growth rate.
If you want to switch of the \(CO_2\) effect on transpiration (e.g. if you use want to use the same solution with projects to calculate with and without \(CO_2\) effect), then you can parameterize the component, so that the factor is always 1:
For clarity reasons however, it is recommended to use different solutions and to remove the SimComponent from the solution, if you don't want to calculate \(CO_2\) effect on transpiration.
Calculations due to LintulFAST. Further reference needed!
| Content Type | Name | Description | Data Type | Unit | Min Value | Max Value | Default Value |
|---|---|---|---|---|---|---|---|
| constant | cSlope | Slope of the linear function calculating the \(CO_2\) concentration in the atmosphere \(\eqref{co2}\) | DOUBLE | ppm/a | 0.0 | 20.0 | 3.5 |
| constant | cStartValue | Start \(CO_2\) value of the linear function calculating the \(CO_2\) concentration \(\eqref{co2}\) | DOUBLE | ppm | 220.0 | 400.0 | 350.0 |
| constant | cStartYear | Start year of the linear function calculating the \(CO_2\) concentration \(\eqref{co2}\) | INT | a | 1930 | 2020 | 1990 |
| constant | cTranspiration_b | Intercept of the linear function calculating the reduction factor \(\eqref{fco2}\) | DOUBLE | 1 | 0.0 | 20.0 | 1.1 |
| constant | cTranspiration_m | Slope of the linear function calculating the reduction factor \(\eqref{fco2}\) | DOUBLE | reciprocal_parts_per_million | 0.0 | 20.0 | -3.0E-4 |
| input | iActualTranspiration | (Unreduced) actual transpiration | DOUBLE | mm/d | 0.0 | 20.0 | - |
| out | ActualTranspiration | Reduced actual transpiration by \(CO_2\) \(\eqref{redtrans}\) | DOUBLE | mm/d | 0.0 | 20.0 | - |