1. In addition to mechanical turbulence driven by wind shear, fluctuations in the atmosphere are affected by net buoyancy forces which may either enhance or retard the tendency of perturbations to grow. It can easily be verified that net buoyancy forces on a fluid element vanish when adiabatic pressure variations dp =pCBdTare exactly balanced by those associatea with hydrostatic eguilibriurn dp = -pgdz, where g is the gravitational acceleration, and a perfect gas is assumed with pressure p, temperature T, density p, and specific heat at constant pressure Cp• Eguating the pressure differentials gives the vertical temperature gradient associated with this ntral stability condition, tho;lo-ca.1.1-1c:u dry adiabatic lapse rate,
2. Uo,2-3m/s I\ \ IOOO \p;T
3. ' MEAN GRADIENT 400-1·-'
4. I -8 -6 -4 -2 0 2 4 6 8 10 12 14 16