Observed linear and nonlinear K layer response

Potassium densities and temperatures were measured on board the German Research Vessel ‘Polarstern’ with the containerized IAP (Institute of Atmospheric Physics) K‐lidar. Considerable wave activity was observed in the K density profiles as well as the temperature profiles, in particular during the night of May 23/24, 1996 over the South Atlantic ocean. A strong monochromatic wave was observed between 85 and 100 km. The calculated relative K density variations are in phase with the temperature variations at the bottom of the K layer and 180° out of phase at the top of the K layer as was to be expected from linear gravity wave theory. The height of change (92–93 km) between positive and negative correlation of temperatures and K densities is clearly dominated by the nonlinear layer response, which could be observed largely because of a strong monochromatic gravity wave with vertival wavelength of 30 km and a horizontal period close to 5 hours, quite similar to the predicted nonlinear layer response from theory. These data show that (1) chemical effects are negligible in the response of the K layer to the passage of an atmospheric gravity wave, and (2) that near the peak of the K layer non‐linear effects dominate the response.