Figure 8.

Exploring the properties of the NEB using Cassini CIRS temperature retrievals from 2000 (Fletcher et al. 2016a), comparing the latitudes of the NEB cyclones (16°N; solid black line) and NTrZ anticyclones (20°N; solid red line). We plot (a) the temperatures; (b) the Brunt Väisälä frequency; (c) the zonal winds estimated from the vertical wind shear in panel (e); (d) the latitudinal gradient of the quasi-geostrophic potential vorticity; (f) the Rossby deformation radius; and the square of the vertical wavenumber m in the case of pure gravity waves (g), inertio-gravity waves (h), and Rossby waves (i). The CIRS constrained temperatures between 80 and 800 mbar, so values outside of this range should be treated with caution. For the calculations of m², we show estimates for c_x = −5 m s⁻¹ (dashed line), c_x = −15 m s⁻¹ (solid line), and c_x = −25 m s⁻¹ (dotted line) for 16°N (black) and 20°N (red). Parameters based on first- and second-order derivatives of the T (p) are highly uncertain, as described in the main text, and should be considered as a qualitative guide only. The blue dashed line indicates the zero point.