AbstractTwo sets of aerological data are used to study the time‐averaged budget of the zonal momentum in the free atmosphere over Europe in winter. In many respects the budget appears to be different from that reported by Holopainen et al. (1980) for North America.Over Europe the coriolis force associated with the southward‐directed ageostrophic meridional flow tends to decrease the westerly momentum. A compensating effect is caused by horizontal momentum flux convergence which takes place in the zonal as well as in the meridional plane and is due mainly to transient flow systems (large‐scale turbulence).The residual term in the momentum budget indicates that over Europe the sub grid‐scale processes on the average cause a small accelerating effect on the large‐scale zonal flow in the upper troposphere. The residual force over the mountainous region of Europe (5 °E ‐ 30 °E, 45 °N ‐ 50 °N) is a decelerating one in agreement with the results for the corresponding area
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