Heat Stress Module theory: Difference between revisions

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This page described the algorithm prescribed by the DPRA report.
This page describes the algorithm prescribed by the {{Template:Heat_DPRA_Report}}. For a visual overview of the Heat Stress Module, see [[Heat_Stress_module_overview|Heat Stress Overview]].
==Algorithm==
The DPRA report calculations are implemented as follows:


The calculation prescription of the DPRA report is implemented as followed:
At the start of the calculation, the following data is pre-calculated for each cell:
# The [[foliage height calculation model (Heat Stress Overlay)|foliage height calculation model]] is used to calculate the [[Foliage result type (Heat Stress Overlay)|foliage height]] (if applicable).
# The [[sky view factor calculation model (Heat Stress Overlay)|sky view calculation model]] is used to calculate the [[Sky view result type (Heat Stress Overlay)|sky view factor]].
# The [[average calculation model (Heat Stress Overlay)| average calculation model]] is used to calculate the [[vegetation avg result type (Heat Stress Overlay)|averaged vegetation fraction]] and the [[Sky view avg result type (Heat  Stress Overlay)|averaged sky view factor]].
# The [[UHI formula (Heat Stress Overlay)|urban heat island formula]] is applied to calculate the [[Uhi result type (Heat Stress Overlay)|urban heat island effect value]].


Calculate once at the start:
Then, for each timeframe, the following data is calculated per cell:
# The [[Foliage_height_(Heat_Overlay)|foliage height]] in case the foliage height should be based on foliage [[Function|Functions]] with a height and a [[Foliage_crown_factor|foliage crown factor]]. See the [[Foliage_height_calculation_(Heat_Overlay)|foliage height calculation model]].
# The [[temperature formulas (Heat Stress Overlay)|temperature formulas]] are applied to calculate the [[temperature atmosphere result type (Heat Stress Overlay)|atmospheric temperature]], and the Wet-bulb temperature.
# The [[Sky_view_result_type_(Heat_Overlay)|sky view factor]], based on the terrain height, buildings and [[Foliage_height_(Heat_Overlay)|foliage height]].
# The [[shade calculation model (Heat Stress Overlay)|shade calculation model]] is used to determine whether the cell is [[shade result type (Heat Stress Overlay)|shaded]].
# The [[Vegetation_avg_result_type_(Heat_Overlay)|average vegetation fraction]] and [[Sky_view_avg_result_type_(Heat_Overlay)|average sky view factor]]. The average window is based on a wind direction and speed. For more information on this averaging window, see [[Average_step_(Heat_Overlay)| average step]].
# The [[Wind calculation model (Heat Stress Overlay)|wind calculation model]] is used to determine the [[Wind speed result type (Heat Stress Overlay)|wind speed]] (using [[Weather station (Heat Stress Overlay)|weather station data]]).
# Per cell: the [[Uhi_result_type_(Heat_Overlay)|urban heat island effect value]]. See [[UHI_formula_(Heat_Overlay)|Urban heat island formula]].
# The [[Diffuse radiation formula (Heat Stress Overlay)|diffuse radiation formula]] is applied to calculate the diffuse radiation.
 
# The [[PET formulas (Heat Stress Overlay)|physiological equivalent temperature formulas]] are applied to calculate the final [[Pet result type (Heat Stress Overlay)|physiological equivalent temperature (PET)]].
Next, for each timestep, calculate the following:
{{article end
# Per cell: the [[Temperature_atmosphere_result_type_(Heat_Overlay)|atmospheric temperature]] and the Wet-bulb temperature. See [[Temperature_formulas_(Heat_Overlay)|Temperature formulas]];
|notes=
# Per cell: is the cell [[Shade_result_type_(Heat_Overlay)|shaded]] by a building, foliage or landscape features. See [[Shade_calculation_(Heat_Overlay)|shade calculation]];
* Each [[Dates_(Heat_Overlay)|date-time]] created in the Heat Stress Overlay configuration wizard will be its own timestep.
# Per cell: the wind speed at 1.2 m above ground, translated from the 10 m wind speed measured at a [[Weather_station_(Heat_Overlay)|weather station]].
* 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.
# Per cell: the diffuse radiation, based on the sun [[Hourly_radiation_(Heat_Overlay)|radiation]] and [[Sun_altitude_(Heat_Overlay)|altitude angle]]. See [[Diffuse_radiation_formula_(Heat_Overlay)|diffuse radiation formula]];
* Automatic translation to future KNMI WH-scenarios is not supported. However, these can be configured manually by providing custom weather station data.
# Per cell: the physiological equivalent temperature (PET). If it is night or the cell is in the shade, the [[PET_formulas_(Heat_Overlay)#PET_Shade_and_Night_formula|shade formula]] is used, else the [[PET_formulas_(Heat_Overlay)#PET_Sun_formula|sun formula]] is used.
}}
 
{{HeatOverlay_formula_nav}}
 
==Notes==
* Each [[Dates_(Heat_Overlay)|date-time]] created in the Heat Overlay Wizard will be its own timestep.
* In the DPRA report step description, the atmospheric temperature is only calculated once. However, the Atmospheric temperature formula used an hour of day input parameter and should therefore be performed each timestep.
* We have not implemented an automatic translation to future KNMI WH-scenarios. However, since users can provide their own weather station data, it can be configured manually.
{{Template:HeatOverlay_formula_nav}}

Latest revision as of 07:18, 9 July 2026

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:

  1. The foliage height calculation model is used to calculate the foliage height (if applicable).
  2. The sky view calculation model is used to calculate the sky view factor.
  3. The average calculation model is used to calculate the averaged vegetation fraction and the averaged sky view factor.
  4. 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:

  1. The temperature formulas are applied to calculate the atmospheric temperature, and the Wet-bulb temperature.
  2. The shade calculation model is used to determine whether the cell is shaded.
  3. The wind calculation model is used to determine the wind speed (using weather station data).
  4. The diffuse radiation formula is applied to calculate the diffuse radiation.
  5. 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.
Heat Stress Module
Heat Stress Module
Tutorials
Overview
Theory
Benchmarks
Group
Formulas
UHI • Temperatures • Diffuse radiation • PET
Calculation models
Foliage height • Sky view factor • Shade • Average vegetation and sky view factor
Related
Calculation models and formulas • Feature attributes • Model attributes • Result types


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