PET formulas (Heat Overlay): Difference between revisions
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* u<sub>t</sub> is the calculated [[Wind_speed_formula_(Heat_Overlay)|wind speed]] at 1.2m above ground time t; | * u<sub>t</sub> is the calculated [[Wind_speed_formula_(Heat_Overlay)|wind speed]] at 1.2m above ground time t; | ||
* T<sub>w,t</sub> is the calculated [[Temperature_formulas_(Heat_Overlay)#Wet-bulb_Temperature_formula | wet-bulb temperature]] at time t; | * T<sub>w,t</sub> is the calculated [[Temperature_formulas_(Heat_Overlay)#Wet-bulb_Temperature_formula | wet-bulb temperature]] at time t; | ||
* Q<sub>d,t</sub> is the calculated [[diffusive radiation (Heat Overlay)|diffusive radiation]] at time t; | * Q<sub>d,t</sub> is the calculated [[Diffuse_radiation_formula_(Heat_Overlay)|diffusive radiation (Heat Overlay)|diffusive radiation]] at time t; | ||
* σ is the Stefan Boltzmann constant, which is 5.670374419...×10<sup>-8</sup> W⋅m<sup>-2</sup>⋅K<sup>-4</sup>; | * σ is the Stefan Boltzmann constant, which is 5.670374419...×10<sup>-8</sup> W⋅m<sup>-2</sup>⋅K<sup>-4</sup>; | ||
* B<sub>b,t</sub> is the [[Bowen_ratio_(Heat_Overlay)|bowen ratio]] at time t; | * B<sub>b,t</sub> is the [[Bowen_ratio_(Heat_Overlay)|bowen ratio]] at time t; | ||
Revision as of 12:04, 12 September 2019
The physiological equivalent temperature PET is calculated for two possible options based on the situation:
- A cell is in the shade or it is night at time t: PETshade, night;
- A cell is in the sun during the day: PETsun;
PET Sun formula
The PET sun formula is as followed:
PETsun = -13.26 + 1.25 · Ta,t + 0.011 · Qgl,t - 3.37 · ln(ut) + 0.078 · Tw,t + 0.0055 · Qgl,t · ln(u) + 5.56 · sin(ϕt) - 0.0103 · Qgl,t · ln(u) · sin(ϕt) + 0.546 · Bb,t + 1.94 · Svf
where,
- Ta,t is the calculated atmospheric temperature at time t;
- Qgl,t is the hourly radiation at time t;
- ut is the calculated wind speed at 1.2m above ground time t;
- Tw,t is the calculated wet-bulb temperature at time t;
- ϕt is the sun altitude at time t;
- Bb,t is the bowen ratio at time t;
- Svf is the calculated sky view factor;
PET Shade and Night formula
The PET sun formula is as followed:
PETshade,night,t = -12.14 + 1.25 · Ta,t - 1.47 · ln(ut) + 0.060 · Tw,t + 0.015 · SvfQd,t + 0.0060 · (1-Svf) · σ · (Ta,t+273.15)4
where,
- Ta,t is the calculated atmospheric temperature at time t;
- ut is the calculated wind speed at 1.2m above ground time t;
- Tw,t is the calculated wet-bulb temperature at time t;
- Qd,t is the calculated diffusive radiation (Heat Overlay)|diffusive radiation at time t;
- σ is the Stefan Boltzmann constant, which is 5.670374419...×10-8 W⋅m-2⋅K-4;
- Bb,t is the bowen ratio at time t;
- Svf is the calculated sky view factor;
