Heat Module overview

This page contains a visual overview of the Heat Stress Module and acts as a starting point to understand what the Heat Stress Module can deliver.

Heat Module

Tutorials

Overview

Theory

Benchmarks

Ingredients

The calculation of the Heat Stress Overlays takes into account:

• Meteorological circumstances such as:
  • Sun angles, altitude and azimuth, dependent on date and time of day and project location.
  • Air temperatures, (hourly, daily minimum and maximum);
  • Global radiation, (hourly and average);
  • Relative humidity (hourly);
  • Wind speeds (hourly and daily average).
  • Wind direction (hourly)
• Spatial situation, such as:
  • Land use, for fraction vegetation and rate of evaporation (Bowen ratio).
  • Terrain, foliage and building heights

Calculation of Physiological Equivalent Temperature

To calculate the Physiological Equivalent Temperature (PET), we first have to determine which formula (sun or shade/night) should be used. It is selected by:

• Day or night? Determined by the sun altitude angle;
• Is a cell shaded? Calculated by the shade calculation model;

PET sun

The following factors influence the Physiological Equivalent Temperature for locations directly in the sun:

• The atmospheric temperature, calculated by the atmospheric temperature formula;
• The hourly global radiation from the sun, supplied as weather station data;
• The wind speed at 1.2 meter above ground, calculate by the wind speed calculation model;
• The Wet-Bulb temperature, calculated by the Wet Bulb temperature formula;
• The sun altitude, calculated automatically based on the project area, date and time of day;
• The Bowen ratio, an attribute obtained from Buildings or Terrain on that specific location;
• The sky view factor, calculated by the sky view factor calculation model.

PET shade and night

The following factors influence the Physiological Equivalent Temperature for locations directly in the shade or at night:

• The atmospheric temperature, calculated by the atmospheric temperature formula;
• The wind speed at 1.2 meter above ground, calculate by the Wind speed calculation model;
• The Wet-Bulb temperature, calculated by the Wet Bulb temperature formula;
• The sky view factor, calculated by the sky view factor calculation model.
• The diffuse radiation, calculated by the diffuse radiation formula.