Coefficients α ₁ and α ₂ estimated from the least-square adjustment of equation (3). Top: for the Northern hemisphere; Bottom: for the Southern hemisphere. The colours are related to the Martian seasons with 45° ≤ Ls < 225° for the red curve and 225° ≤ Ls < 45° for the green curve. The lines are the estimated α ₁ and α ₂ coefficients with respect to the . The crosses are the coefficients obtained for the different index while the lines are the values used in the model.