Frequency and diurnal variation of dust storms in the contiguous U.S.A.

Abstract

Studies of regional wind erosion and the translocation of suspended particles are important for accurate surveys of air pollution. This category of investigation has nationwide implications for planning and regulatory purposes. However, most regional studies of wind suspension (airborne dust) have centered around the Great Plains without much consideration given to other areas of the country. The purpose of this study is to quantitate the wind translocation problem throughout the contiguous United States by using visibility as an index. National Weather Service and military surface observations on dust were analyzed for annual, monthly and diurnal periods. Frequency of dusty periods were based on hourly weather observations from stations recording dust, blowing dust, and blowing sand when visibility was 7 miles or less. Mountainous, forested, and predominantly maritime regions are generally free from major dust storms. The highest dust frequency is in the Southern Great Plains. Secondary dust frequency maxima occur in the Western States, Northern Great Plains, southern coastal Pacific and inland valleys and the Southeast. Maximum dust frequency occurs in early and late spring months for most regions but some regions experience additional dust in summer or fall. Hourly observations show higher dust frequencies occur in the afternoon between 12.00 and 20.00 LST, or during the period of maximum thermal instability. Regional dust frequency patterns are discussed in relation to the principal factors which govern natural wind-caused suspension, i.e. (1) surface properties, (2) particle properties, and (3) meteorological conditions.