Working from Eqs. (2.19) and (2.20), derive the QG vorticity equation (2.21). Be sure to show all of your work clearly and neatly. +u 's at g g g v g tus at 's g + fouag + Byue =0, and ang ve ay -+1 g -fovag-Byvs 04x =-V - V. V(g +f)+fo -f) + fo ap g 8 at (2.19) |-- (2.20) (2.21)