Behavior of the Refractive-Index-Structure Parameter near the Ground*

A semiempirical theory is developed which relates the refractive-index-structure parameter Cn2 in the lowest few tens of meters to the vertical gradients of wind speed and temperature and to a stability parameter. This provides an indirect method of determining Cn2, or its temperature counterpart CT2, and the method is successfully applied to recent data which include directly measured CT2 values. The height dependence of the structure parameter is also determined, and the predicted z−4/3 profile under unstable conditions agrees with recent data in the free atmosphere at heights up to 500 m.