Gill model properties on the sphere with different input parameters. (a) Scaled upper-layer EMFC. (b) Scaled lower-layer zonal wind ﹩{u}_{2}^{{\prime} }﹩ at the equator. Note the eastward shift in ﹩{u}_{2}^{{\prime} }﹩ with increased E and ﹩{ \mathcal S }{{\rm{Ro}}}_{T}{T}_{{\rm{rad}}}﹩. The black line shows the vertically integrated reference potential temperature profile at the equator. Drag-free solutions (dashed) are obtained analytically in Appendix A. Solutions with low-level drag (solid) are obtained numerically.