Heat Stress Module theory
(Redirected from Calculation models and formulas (Heat Stress Overlay))
This page describes the algorithm prescribed by the DPRA Heat stress report. For a visual overview of the Heat Stress Module, see Heat Stress Overview.
Algorithm
The DPRA report calculations are implemented as follows:
At the start of the calculation, the following data is pre-calculated for each cell:
- The foliage height calculation model is used to calculate the foliage height (if applicable).
- The sky view calculation model is used to calculate the sky view factor.
- The average calculation model is used to calculate the averaged vegetation fraction and the averaged sky view factor.
- The urban heat island formula is applied to calculate the urban heat island effect value.
Then, for each timeframe, the following data is calculated per cell:
- The temperature formulas are applied to calculate the atmospheric temperature, and the Wet-bulb temperature.
- The shade calculation model is used to determine whether the cell is shaded.
- The wind calculation model is used to determine the wind speed (using weather station data).
- The diffuse radiation formula is applied to calculate the diffuse radiation.
- The physiological equivalent temperature formulas are applied to calculate the final physiological equivalent temperature (PET).
Notes
- Each date-time created in the Heat Stress Overlay configuration wizard will be its own timestep.
- Although the DPRA report description states that atmospheric temperature is calculated once, it must be calculated every timestep because the formula requires an 'hour of day' parameter.
- Automatic translation to future KNMI WH-scenarios is not supported. However, these can be configured manually by providing custom weather station data.
