Assume that in a certain area, the atmospheric lapse rate ?(gamma) subscript actual, is equal to zero from the ground up to 2000 meters. Starting from the hydrostatic equation (given below), derive an equation relating atmospheric pressure to altitude. dP/dz = -gp Use your equation to calculate the pressure (in mb) at 1200 m above the ground (assume surface temperature = 15 degree C and surface pressure = 1000 mb).