The structure of internal gravity waves in the atmosphere from high resolution radar measurements

A radar sounding system developed by one of us (Richter) has a height resolution (about 1 meter) capable of resolving the detailed structure of small features in the atmosphere never before seen. Two distinctly different types of wave phenomena characterize many of the records. One type is a long-period internal wave. The mechanism of generation is discussed and waves observed on the radar are compared with theory. They are shown to represent the fundamental mode of gravity waves for a stable lower troposphere. The other type is much shorter in period and typically shows a cusped structure like a breaking wave. Radar observations are compared with simultaneous wind and temperature soundings, and it is concluded that wind shear is unquestionably the mechanism of generation of the second type. Evidence is presented that untrapped waves above the region of instability can cause a flow of energy away from the shear zone and the energy flux is calculated. Their relation to atmospheric stability is described. Their size is deduced from the observations, and their potential as a mechanism for generation of turbulence at the high frequency end of the atmospheric turbulence spectrum is discussed.