Estimation of diurnal variation of surface layer at Tarapur site using ultrasonic anemometer

Surface layer (SL) is defined by the region above the earth surface (50-100 m) wherein shearing stress is approximately constant with height, and the wind structure is primarily determined by the nature of the surface and the vertical gradient of temperature. During day time due to convection, variation in shear stress with height is less and hence the SL heights are higher and conversely during nights decrease in shear stress with height is higher and hence SL heights are lower. SL height is decreasing with increase in the stability and also SL heights are higher for lower values of U_o^* for any stability category. Hourly average SL heights for Tarapur site varied from 40 to 142 m with U_o^* = 0.1. Estimation of SL height for the site will be useful input parameter for the dispersion models. (author)