A theoretical analysis of lee wave clouds observed by Tiros I

A Tiros I cloud photograph taken April 18, 1960 over the southern part of South America is examined. The clouds were very regularly orientated in parallel bands on the lee side of the Andes. The cloud pattern is assumed to be quasi-stationary. It seems to be quite clear that the clouds are formed by the waves which are set up in the air flow over the mountain range. The wind direction varied little with height and was almost perpendicular to the mountain.

The observed wave length is compared with a theoretically computed value obtained by using a method previously presented by the author (Döös, 1961). The agreement between these values is good. The amplitude of the disturbances produced by the mountain has also been evaluated. For comparison the wave length has also been evaluated by means of the parcel method.