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2.1.3.4 Wind Speeds <br />• <br />All wind speed graphs and/or roses developed from the data collected by the <br />Yampa Project Environmental Task Force near Craig, Colorado show a predomin- <br />ance of calm [o gentle wind speeds. Wind speeds have been recorded at less <br />than 3.5 mph (3 knots) during an average of 47 per cent of the total hours <br />each year (Environmental Research and Technology, 1979). <br />The field studies from 1970 through 1972 also documented low wind speeds the <br />majority of the time. Surface winds were recorded at less than 10 mph (S.7 <br />knots) approximately 777. of the entire study period (Stearns-Roger, 1973). A <br />clear pattern for wind speeds could not be developed during these early stud- <br />ies as the velocities varied significantly from year to year and month to <br />month. However, nearly all monthly mean wind speeds ranged between 5 to 8 mph <br />(4.4 to 7.0 knots). <br />Figures 2.1-10 and 2.1-11 depict the wind speed versus the hour of day near <br />Craig. These curves are typical Eor the region and show marked similarities <br />• for the three (3) different monitoring sites during [he six-year (1970-1976) <br />monitoring period. See Appendix C, Figures C-1 and C-2. Minimum wind speeds <br />were always near sunrise (6:00-8:00 am MST) as the surface nocturnal radiative <br />heat losses were at their greatest Level (Stearns-Roger, 1975). Maximum wind <br />speeds were obtained during the afternoon when solar insolation was at its <br />height. The daily peak wind speeds will occur between 3:00 and 4:00 pm MST <br />and affect all elevational ranges above the ground surface. <br />• <br />2-33 <br />