Wind Erosion:
An International Symposium/Workshop

Roel Vining and Dr. James Gregory

Wind speed is an important variable when studying the likelihood and intensity of air quality degradation. High wind speed coupled with other environmental conditions can result in serious wind erosion events like that which occurred in California on Interstate 5 in November 1991, resulting in a 64 vehicle accident. Alternately low winds reduce transport of particulates and gases, and increase the potential of odors from feedlots. Historically, a model based on a sine wave has been used to model mean diurnal variations in wind speed. This paper reports on the function and nature of variations in diurnal changes in wind speed.

This study builds on previous work done by the authors to describe diurnal wind speed and relative humidity patterns at six locations in the Great Plains. That study found that mean diurnal wind speed is almost constant during dark hours, and follows a parabolic curve during daylight hours. Hourly wind speed data were gathered for 10 locations in different climatic regions across the country: Spokane, WA, Phoenix, AZ, Fresno, CA, Salt Lake City, UT, Casper, WY, Bismarck, ND, Des Moines, IA, Baton Rouge, LA, Albany, NY, and Atlanta, GA. Monthly averages of temperature for each hour of the day were calculated and compared to models previously developed from the Great Plains locations and to a sine wave model. While there were considerable differences between the average wind speed at each location, diurnal variations displayed patterns similar to those previously identified. While providing an acceptable statistical fit, a sine wave model does not adequately describe breakpoints and the shape of diurnal wind speed patterns. The residual error is certainly not random.