Wind vane

The use of a measurement generally dictates the circumstances of data collection. For example, to provide a best estimate of plume transport direction, hour by hour, of a release from a 75-m stack, a wind vane at the 100-m level of a tower will probably provide more representative wind direction measurements than a vane at 10 m above ground. If the release has buoyancy so that it rises appreciably before leveling off, even the 100-m measurement may not be totally adequate. 

Wind vane A revolving instrument used to indicate the direction in which the wind is blowing. 

Wind vane is the instrument used to determine the direction in which wind is blowing. Wind vane points into the wind or the direction from which the wind is blowing. For example, if the wind vane points towards the north east, it indicates a north east wind. It has a light arrow where the arrow tail points in the opposite direction. In airports, wind socks are used. 

Ancient bones are somewhat like wind vanes that show from which direction a particular hypothesis breezes across the fossil field. If a paradigm is useful one should be able to predict what will be found at the end of the projected course. This means that one can put a general evolutionary hypothesis like a grid over the pattern of evidence and see how fossils and expectations match. In the standard model predictions are not possible because the phenotype lattice radiates from one spot (the common ancestor) with every beam studded with chance-initiated branch points that give rise to unpredictable patterns.1 By rules of the Genomic Potential Hypothesis the future position of a species in the hierarchy of taxa is, in principle, predictable. The discussion of our own past will reflect this fundamental change in philosophy. 

The Caltech machine shop built a few British gustiness meters, which was a wind vane free to move up and down as well as left-to-right. It had a Light-weight ink pen on its downwind side, which put ink marks on a sheet of curved paper. We let it operate for two minutes, and the pattern of scribbles indicated the degree of horizontal and vertical turbulence. 

To develop our novel micro-meteorological instruments, we used a large cow-pasture east of Pasadena, which gently sloped up toward the San Gabriel mountains. We had a favorite demonstration of katabatic wind. We had a pole with eight wind vanes spaced about every half meter apart. In the afternoon, the sea breeze caused all the wind vanes to point toward the Pacific Ocean. As sunset approached, first the lowest wind vane on our pole turned and pointed toward the mountain as a shallow current of cold air flowed downhill. Somewhat later the second vane turned, then the third, fourth, fifth, sixth, seventh, and finally the eighth turned as the katabatic wind built up to be a deep gentle flow of cold air. Before sunset, we could almost tell the time of day by how many wind vanes pointed uphill. 

Wind direction can be determined in the field by measuring with a rotn >astt the direction of drift of smoke or of dust thrown into the air and itdding 180 degrees. It can also be determined by means of a portable wind vane previously oriented by compass, or by taking the magnetic Atimuth from the wind vane to a point inchcated by its arrow. ... 

Smoke drift indicates wind direction, still wind vanes Wind felt on face, leaves rustle, vanes begin to move... 

Surface wind direction is measured by a wind vane, essentially a flat plate on a horizontal rod that aligns itself with the wind direction. Wind direction aloft is determined by pilot balloons (less than 1 m in diameter, equipped to carry a small radio for tracking) and tetroons (a constant-volume balloon in the shape of a tetrahedron, which is ballasted so as to remain at a nearly constant elevation). 

Figure 16.1 shows a typical record of one wind component that might be obtained by an anemometer. From such a record a mean velocity u, can be obtained. Wind turbulence refers to the properties of the fluctuations about the mean in a record such as the one shown in Figure 16.1. These fluctuations are primarily responsible for the spreading of a cloud of pollutants in the atmosphere. It is important to measure all three components of the wind velocity, since the vertical fluctuations are often the most important in transporting pollutants. The vertical velocity fluctuations provide a direct measure of the stability of the atmosphere. In order to obtain a record such as the one shown in Figure 16.1 a sensitive, rapidly responding wind vane and anemometer are required. Vertical fluctuations can be measured by ...

Bivane a wind vane constructed so as to measure wind direction fluctuations in vertical as well as horizontal planes. 

I -3 Light Air Direction of wind shown by smoke drift, but not by wind vanes. Ripples with the appearance of scales are formed, but without foam crests. 

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