Wind structure over the sea

A comparison between theory and observation is made for he problem of veer of wind with height over the sea. Observations made in H.M.ships, notably aircraft carriers, which may be assumed to be at least as accurate as shore based observations are included. Frequency diagrams for the angle of veer show peculiar features which are absent from land observations. It is suggested that the motion of the sea surface mobility is discussed. for this, and the general effect of surface mobility is discussed. In view of the uniformity of the surface and the absence of marked thermal effects, one would expect good agreement between theory and observation in the case of wind structure in the friction layer over the sea. unfortunately the agreement is, if anything, less good than over the land, and the sea observations show certain interesting features which are absent in the case of land observations. It has been the practice in the past to attribute much of the disparity between theory and observation over the sea to observational difficulties. The difficulty of making pilot balloon observations “from a moving steamer” is mentioned by Rossby, and others seek refuge in the fact that wind directions at the surface are only measured to the nearest compass point. The probable validity of these objections in the past is not denied, but the recent rapid development of the Naval meteorological Service, and the growing volume of sea observations of a high standard of accuracy collected by trained observers calls for a review of the situation. Surface winds in H.M. ships are no longer measured n points, but in degrees, allowance for the relative motion of the ship being made automatically. An occasion when great accuracy in measurement of wind direction is possible is when aircraft are being flown off or on to the deck of a carrier. Furthermore pilot balloon observations are not, in general, more difficult to carry out on board than on shore. Ships of the size of aircraft carriers do not move a great deal in winds of less than force six, and the instruments available for following the balloon are superior to those used on shore, although they cannot be described here for obvious reasons. It may be taken as certain that observations taken on one of the larger carriers are at least as accurate as any taken ashore provided the wind is of force five or less. In the discussion below, observations from carriers will be given, as well be given, as well as those from merchant ships.