Characterization of Small Scale Roughness Elements on a Water Surface

<p>Air-water exchanges of momentum heat and water vapor were investigated from a tower on a fresh water lake at low to moderate wind speeds 3 less than U(sub 10) less than 8 m/s. The tower is located 15 m offshore where water depth is about 4 m. For this purpose surface fluxes were determined directly from atmospheric turbulence measurements using the eddy correlation technique and water surface elevations due to long gravity and short gravity-capillary waves were measured by a resistance wire wave gauge. The observed wave field was generated purely by the local winds over a well-defined fetch of 7 km. Experimental results showed that for the conditions of light winds and nonneutral atmospheric stratification encountered in this study atmospheric turbulence statistics could not provide an estimate of the surface fluxes with great accuracy. For similar environmental conditions the neutral drag coefficient C(sub DN) and the surface roughness length parameter z(sub 0) determined from flux-profile relationships were found to show large scatter mainly due to the significant variations in the contribution to total covariances by the low-frequency atmospheric phenomena. However on the average they were found to be in good agreement with other independent estimates of C(sub DN) and z(sub 0) obtained from the wave measurements. The technique of determining C(sub 0) and z(sub 0) from wave spectra devised in this study was successfully used not only during steady state but also during rapidly changing wind speed conditions.</p><p>This work has been selected by scholars as being culturally important and is part of the knowledge base of civilization as we know it. This work was reproduced from the original artifact and remains as true to the original work as possible. Therefore you will see the original copyright references library stamps (as most of these works have been housed in our most important libraries around the world) and other notations in the work.</p><p>This work is in the public domain in the United States of America and possibly other nations. Within the United States you may freely copy and distribute this work as no entity (individual or corporate) has a copyright on the body of the work.</p><p>As a reproduction of a historical artifact this work may contain missing or blurred pages poor pictures errant marks etc. Scholars believe and we concur that this work is important enough to be preserved reproduced and made generally available to the public. We appreciate your support of the preservation process and thank you for being an important part of keeping this knowledge alive and relevant.</p>