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<br /> <br />-24- <br /> <br />Anemometers developed specifically to measure high wind v.elocities <br />.commonly are not suitable at low velociti,es. Among wind vanes, one that <br />is heavy may oscillate less than on~ that is light and so may mask short- <br />period changes in direction, or may over-swing on sudden changes. A Vane <br />,that is large and that ha,s a relatively lOng tail tends to smooth out <br />~any whirls and eddies to which a short'vane would respond. <br /> <br />Mechanical failure during periods of low temperature may involve com- <br />plete stoppage by accumulated ice or snow, or substantial ~nder-regi,stry <br />owing to congealed lubricant in bearings. An. instrument improperly' <br />cleaned and oiled may under-register at any time. As will be obvious, <br />erroneous records so caused are all but impossible to identify and adjust. <br /> <br />Use of data on wind <br /> <br />Wind records are useful for a wide. range of purposes, including <br />(1) the selection of sites for airports, industrial plants, wind-power <br />generators, and meteorologic stations; (2) estimating wind loads on <br />bUildings, television towers, or other structures; (3) study of the <br />distribution and dilution of dust, pollen, pollutants, and cloud-seeding <br />nuclei; (4) determining wind effect on the formation and movement of ice <br />in streams and lakes; also on wave aotion and its reJ.ation to shore <br />erosion and to loading and movement of ships; and (5) weather forecasting, <br />both in general and in particular re.gard to fOrest-fire warning and <br />fighting, frost warning, and air-borne commerce. <br /> <br />Wind is a principal variable in the investigation, forecasting or <br />oalculation of evaporation. Its speed, direction, eddy structure and <br />variation with height influence the rate at which the vapor moleo~les <br />are removed from the immediate, vicinity of the liquid surface. <br /> <br />Wind is responsible for drifting of snow and strongly effects the <br />deposi, tion of snow around and on obstaoles such as buildings, fenoes, <br />bridges, and roofs. It is a parameter in the estimation and study of <br />snow-melt rates and amounts. <br /> <br />Wind is known to have substantial influence on the catch of precipi- <br />tation gages, the oatch diminishing as wind speed i,ncreases. This effect <br />is much more marked with snow t!)an with rain. It can be countered by <br />shielding the gage orifice and by locating gages at sites protected from <br />the wind. <br /> <br />The orography of a region has a pronounced effect on wind flow, which <br />in turn strongly influences the rate and distribution of precipitatiOn' <br />These orographic influences can result in more precipitation on windward <br />slopes and on steep slopes than on lee slopes and gentle slopes. <br />