PET formulas (Heat Overlay)

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: PET_{shade, night};
• A cell is in the sun during the day: PET_sun;

PET Sun formula

The PET sun formula is as followed:
PET_sun-13.26 + 1.25 · T_a,t + 0.011 Q_gl,t - 3.37 · ln(u_t) + 0.078 · T_w,t + 0.0055 · Q_gl,tln(u) + 5.56·sin(ϕ) - 0.0103·Q_gl,t·lln(u)sin(ϕ)+0.546B_b,t + 1.94*S_vf
where,