Commission 2. Radio and nonionized media

2.1.1 IUCRM colloquium. The June 1972 Inter-Union Commission on Radio Meteorology (IUCRM) colloquium, ‘Waves and turbulence and their interaction with EM waves,’ was reported by B. R. Bean (USA). The IUCRM is concerned with interdisciplinary problems related to the effects of the nonionized atmosphere on the propagation of electromagnetic waves and the use of remote-probing techniques to study the atmosphere. Of particular interest to atmospheric scientists and fluid dynamicists on the one hand and to radio scientists on the other is the fine-scale structure of stratified layers marked by strongly sheared flow. Such stratums are the seat of both stable gravity waves and unstable Kelvin-Helmholtz waves; the breaking of the latter is responsible for clear-air turbulence, among other things. The resulting refractively turbulent stratum is also responsible for the scatter of EM waves in tropospheric propagation and for backscatter in the case of microwave or acoustic radars. Recent studies with high-resolution radars have cast new light on the mechanisms of waves and turbulence in hydrostatically stable layers, while fluid dynamicists have advanced this knowledge through theoretical and experimental research on the stability of such flows. Simultaneously, meteorologists have been making strides on the structure and prediction of clear-air turbulence.