AbstractQuasi‐periodic wind variations with height have been commonly observed in the lower stratosphere by means of the radar‐sonde theodolite at Crawley. The atmospheric disturbances which give rise to these wind variations have a vertical dimension of 1 km or so, but their horizontal dimensions must be much greater, perhaps of the order of several hundred kilometers. Perturbation theory is used to show that slow ‘inertia oscillations’ with a period of the order of half a day might have such dim