Temperature formulas (Heat Overlay)

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Two temperature formulas are used in the calculation of the PET value:

  • The atmospheric temperature Ta
  • The wet-bulb temperatur Tw

Atmospheric Temperature formula

where

  • is the calculated atmospheric temperature at time t;
  • is the temperature measured at a weather station at time t;
  • is the calculated Urban Heat Island effect at time t;
  • is the sun daily motion factor at time t;

Wet-bulb Temperature formula

Tw,t = Ta,t · atan( 0.151977 · (ϕ + 8.313659)0.5) + atan (Ta + ϕ) - atan(ϕ - 1.676331) + 0.00391838 · ϕ3/2 atan(0.023101 · ϕ) - 4.686935
where:

  • Tw,t is the calculated wet-bulb temperature;
  • Ta,t is the calculated atmospheric temperature;
  • ϕ is the sun altitude angle;

See also