Shape of the first baroclinic mode of a polytropic envelope, associated with eigenvalue λ=−8.33 10⁻³, for parameters η = 0.18, Ω = 0.15, Q = 1, n = 3, $\mathcal{P}={10}^{-5}$, and E_t = 10⁻², with numerical resolution L_max = 200, N_r = 100. Left: distribution of kinetic energy. Right: distribution of temperature fluctuations, showing the imprint of the Y₂(cos θ) spherical harmonic with its nodal line, as in the Boussinesq case (see Fig. 1 red line in the right plot). In both panels, the colour scale is logarithmic.