Figure 5.

Observed and predicted evolution of the Great Red Spot (GRS) shape for the last 40 years. a. GRS appearance at blue/violet wavelengths⁴² (©AAS, reproduced with permission), with the measured aspect ratio (black line) and the calculated one (white dashed line) using our model (equation (4)) and the parameters reported in Table S3 of the Supplementary Information. b. Evolution of the GRS horizontal aspect ratio (major axis over minor axis on a horizontal plane) over the last 40 years. Measurements of the GRS aspect ratio are represented by the white dots⁴². Error bars correspond to uncertainties of 0.5° in latitude or longitude for each dimension⁴². The dashed line is the decreasing trend of the aspect ratio deduced from the measurements. The blue dots are the aspect ratio computed using our model (equation (4)). Error bars account for the propagation of uncertainties of ± 10 m/s for the GRS velocities⁴² and ±7 m/s for the zonal winds velocity³⁷. c. Vertical aspect ratio c/b and half-height c as a function of time deduced from relation (5). To convert c in kilometers, we use the measurements of b given in Table 1 of Simon et al. (2018)⁴². Error bars account for uncertainties in velocities (Ro_x, σ), measured ellipticity (β) and stratification difference $N^2-N_c^2$ which are given in the Methods and Supplementary Information section 7.