Temperature formulas (Heat Overlay)

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

• The atmospheric temperature T_a
• The wet-bulb temperatur T_w

Atmospheric Temperature formula

$T_{a,t}=T_{station,t}+UHI_{max,t}\cdot f_{sun,t}$

where

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

Wet-bulb Temperature formula

T_w,t = T_a,t · atan( 0.151977 · (ϕ + 8.313659)^0.5) + atan (T_a + ϕ) - atan(ϕ - 1.676331) + 0.00391838 · ϕ^3/2 atan(0.023101 · ϕ) - 4.686935
where:

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

See also

• Wet-bulb temperature

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