Contours of the maximum growth rate max(σ_r) in the parameter space of (k_x, k_z) (solid lines) for Re = ∞ and N = 1 for (a) , (b) , and (c) . For (a) and (b), this corresponds to (Ω, θ) = (1, 90° ), and (Ω, θ) = (1.031, 76°) for (c). Black and blue solid lines are contours of the maximum growth rate of the inflectional and inertial instabilities, respectively, and gray dashed lines in the background are contours of the maximum growth rate for the same parameters but in the traditional f-plane approximation where .