Characteristic wind speed distributions and reliability of the logarithmic wind profile

Wind produces turbulence facilitating the exchange of pollutants and other environmentally important trace gases such as oxygen and greenhouse gases between stationary water bodies and the atmosphere. Whereas wind speeds continuously vary, different wind speed monitoring and characterization procedures have been used for the gas exchange studies. We assessed the impact of measurement time intervals, logarithmic wind speed profiles, and surface roughness values on wind characterizations. The Weibull probability density function effectively characterized yearly and seasonal wind speed distributions. It was not affected by various averaging lime intervals (1-60 min). However, averaging time interval of < 10 min was necessary for reliable characterizations of shorter-periods (< 3-5 days). Vertical wind speed variations were effectively described by logarithmic profile irrespective of atmospheric stability conditions. Interestingly, use of the logarithmic profile allowed the actual U-10 to be predicted with reasonable accuracy for a wide range of surface roughness values. This was true under all stability conditions. Thus, small time intervals and the logarithmic profile appear to be very robust and widely useful techniques.