niveau anémométrique

CONT: A stationary and non-accelerating flow is described with du/dt = dv/dt = 0. With this, (7-3) becomes a set of differential equations for u, v whose solution yields the Ekman spiral. However, if we are not interested in accurate solutions and consider one layer only, we can see the meaning of the friction force as first shown by C. M. Guldberg and H. Mohn in 1883. The wind profile near the earth's surface is usually convex, if represented on a graph with wind speed versus height. The wind speed increases from zero at the earth's surface to significant values near the anemometer level, and further increase of wind speed with height continues at a slower rate. In this situation, the second derivatives of u and v may be assumed proportional to -u and -v, respectively: