2. (10 points) Estimate the rate at which air must subside over the Sahara to balance the heat loss by radiation (assume RTOA=20Wm2 ). Hint: Approximate the vertical gradient of moist static energy with that of potential energy and then use downward advection against this gradient to balance a radiative heat loss, e.g., w[d(gz)/dz]=wg=RTOA(g/ps)..