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,t · ln(u) + 5.56 · sin(ϕ_t) - 0.0103 · Q_gl,t · ln(u) · sin(ϕ_t) + 0.546 · B_b,t + 1.94 · S_vf
where,

• T_a,t
• Q_gl,t
• u_t
• T_w,t
• Q_gl,t
• ϕ_t
• B_b,t
• S_vf