Occurrence and features of ducted modes of internal gravity waves over western Europe and their influence on microwave propagation

Several years of intense investigation of internal gravity waves propagating in low-level ducts in the atmosphere over a rather flat region not influenced by land-sea circulation or mountains are reported. This study gives a rather complete picture of the occurrence, features, and of some of the excitation conditions of these waves. Simultaneous direct measurements made on a meteorological tower, 250 m high, using temperature, vector wind, and sonic anemometer sensors at different altitudes are reported along with indirect measurements using an array of microbarographs with separations over a range of more than 100 km. The study also included microwave propagation links crossing over the meteorological site. Individual wave crests some tens of kilometers long could be followed over a path of more than 100 km. Because of the variability and non-stationary conditions of the lower atmosphere, a direct correlation between a propagating internal wave group and the fading pattern of EM propagation could be found in only a few cases.It is interesting to note Goldie's references to Kelvin and Helmholtz in this regard.