Tidal response of the Earth’s atmosphere to a quadrupolar forcing ( and ) as a function of the reduced tidal frequency χ = (Ω−n_orb)/n_orb (horizontal axis). For each quantity q_n associated with the Hough mode of degree n, except the coefficients (top left) and the scales of variations L_V;n, the function f(χ) = sign(q_n)log (1 + |q_n|) is plotted (vertical axis) for n ∈ ˜−6,5¨. Left, from top to bottom: a) coefficients (Eq. (70)); b) eigenvalues of Laplace’s tidal equation ( defined by Eq. (35)); c) normalized variation scales of the vertical structure of the vertical component, L_V;n = 2π/ (Eq. (48)), plotted in logarithmic scale. Right, from top to bottom: d) real part of the vertical wavelengths ( , Eq. (103)); e) imaginary part of the vertical wavelengths; f) spin parameter ν = 2Ω /σ (Eq. (23)).