It is a matter of common experience that the wind seems stronger when you are high up. It is usually windier, for example, at the summit of a hill than it is in the valley below. In this particular context, of course, the difference can sometimes be explained by the shelter available down in the valley, but the principle, in general, is true: wind does increase with height.
I was reminded of the fact yesterday when writing about Francis Beaufort, and recalled a cause celebre of the last century, a quarrel about the winds between Britain and Germany which erupted and expired long before the two World Wars brought other matters to a head.
Although Admiral Beaufort's scale was a vast improvement on previous methods of describing the wind, it had its limitations. There was, for example, no simple method by which the Beaufort numbers could be related to scientific ways of measuring speed.
During the 19th century, therefore, many attempts were made to assign "miles per hour" equivalents to the Forces on the Beaufort Scale.
At around the same time, the British and German authorities decided to carry out independent studies to resolve the problem. They used the same methods. Veteran seamen were stationed at coastal or island weather stations where the sea was in full view; the experts made their estimates of the wind force based on the appearance of the sea, while the wind speed was measured simultaneously by the scientists with their newfangled anemometers.
The estimated force was related to the measured wind speed under conditions varying from calm to hurricane strength.
But when the results of the studies were compared, discrepancies were found. There was a consistent difference in magnitude between the two. For example, a wind estimated to be of Force 7 by the British observers might have a speed of 38 m.p.h. as measured by the anemometer.
The Germans however, would find that a 38 m.p.h. wind was the equivalent of a Force 9. Who, then, was right? Could it be that two groups of experienced seamen would register such a consistent difference in their estimations?
It took some time to find the answer, but analysis showed that the discrepancy arose from the different exposures of the anemometers. The British instruments were mounted some 30 or 40 feet above the sea, while those of the German contingent operated at a much lower level.
It was a clear indication of a principle not fully appreciated at the time, that measured wind speed depends to a great extent upon the elevation of the point of measurement.