Relative frequency shifts Δν/ν vs. mode frequency ν for modes with ℓ = 0 (upper panel), ℓ = 1 (middle panel) and ℓ = 2 (bottom panel), for a polar spot model relative to QS model with r_c = 0.98 R_⊙ and ϵ = 0.4. Dashed lines represent linear frequency shifts given by Eq. (9). Fitted frequencies from numerical simulations (asterisks for m = 0, triangles for | m | = 1, and crosses for | m | = 2) show the nonlinear behavior of the shifts for m = 0 modes (asterisks). We note that m = 0 and | m | = 1 mode frequencies for ℓ = 2 cross at ν ≃ 3060 μHz.