Contours of horizontal flow convergence (in lavender) and divergence (in yellow) plotted over the temperature (in K) and wind map at the 150 mbar pressure level. The convergence/divergence contour levels are set at ±1 × 10 ⁻⁴, 1.5 × 10 ⁻⁴, 2 × 10 ⁻⁴, and 2.5 × 10 ⁻⁴ s ⁻¹. Clearly, the bulk of the flow has |∇ · v| < 1 × 10 ⁻⁴ s ⁻¹. The narrow region of strong convergence around longitude +135° is what we refer to as a shock-like feature. An increase in temperature around longitude +135° seen in the bottom panel of Figure  1, just one model level below the one shown here, is consistent with adiabatic heating by a downward flow associated with this shock-like feature.