OPTICAL SEEING - MECHANISM OF FORMATION OF THIN TURBULENT LAMINAE IN THE ATMOSPHERE

Data from balloon soundings taken at sites in the Canary Islands, France, and Chile are used to show that hydrodynamic instability, perhaps engendered by the propagation of buoyancy (gravity) or other waves, leads to the formation of thin, turbulent laminae, or ''seeing layers.'' These seeing layers occur almost invariably in pairs and exhibit large values for the temperature-structure coefficient C-T(2) because they form where the gradient of temperature is particularly steep. The refractive-index-structure coefficient is correspondingly large, and so these layers adversely affect the quality of optical propagation. The mechanism proposed here is already known to create clear air turbulence in the stratosphere, and we show how it is consistent with the formation of thin turbulent seeing layers in the troposphere and the stratosphere at night, when the atmosphere is generally stably stratified.