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Wind Erosion:
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Analysis of Wind Data Used for Predicting Soil Erosion

Larry D. Stetler and Keith E. Saxton


Meteorological variables required to estimate soil loss from natural erosive wind events were determined using data collected from 1993 through 1996 at three field sites on the Columbia Plateau (USA). Continuous data collection occurred from May to December of each year providing hourly averaged data during non-erosive periods increasing to minute data during erosive periods. An erosive wind event was defined by sustained exceedence of a threshold wind velocity at a 3.0 m height. Unfortunately, most commercial meteorological data provide hourly averaged values and analyses of these data revealed a possible bias in calculations of available wind energy. Analysis of wind energy, calculated using 1, 15 and 60 minute averaging periods, indicated that both 15 and 60 minute averages underestimated the energy contained in the wind. Significant wind speed fluctuations (occurring on an order of minutes and containing high energy) were lost within hourly averages resulting in an average decrease in calculated wind energy of more than 30%. Improved correlation between 1 and 60 minute wind energies existed when a significant number of minutes per hour (>55) exceeded threshold velocity and decreased rapidly as larger portions of an hour did not exceed threshold. When hourly average velocity was slightly above threshold (with 15-20 minutes of the hour exceeding threshold) calculated energies varied by over 200%. Subsequent calculation of soil loss based on hourly averages would likewise be underestimated. Additional analysis using a 15 minute averaging period indicated significant improvement in the correlation of wind energy over the 60 minute averages and were less than 30%. These analyses suggest a 15 minute resolution for acquisition of meteorological data when such data is intended for estimation of soil loss from erosive winds. When using hourly data, it should be realized significant errors for soil loss may occur.