Analysis of information sources in references of the Wikipedia article "Wind gradient" in English language version.
...the effect of a change in mean wind velocity with altitude, the wind velocity gradient...[permanent dead link]
Thus we have a "wind-speed gradient" as we move vertically, and this has a tendency to encourage mixing between the air at one level and the air at those levels immediately above and below it.
wind gradient = rate of increase of wind strength with unit increase in height above ground level;
The relation between wind speed and height is called the wind profile or wind gradient.
You'll not recognize wind shear if your apparent wind angle is smaller on one tack than on the other because the apparent wind direction is a combination of boat speed and wind speed - and the sailing speed may be more determined by water conditions in one direction rather than another. This means that the faster a boat goes the more 'ahead' the apparent wind becomes. That is why the 'close reach' direction is the fastest direction of sailing – simply because as the boat speeds up the apparent wind direct goes further and further forward without stalling the sails and the apparent wind speed also increases – so increasing the boat's speed even further. This particular factor is exploited to the full in sand-yachting in which it is common for a sand yacht to exceed the wind speed as measured by a stationary observer. Wind shear is certainly felt because the wind speed at the masthead will be higher than at deck level. Thus gusts of wind can capsize a small sailing boat easily if the crew are not sufficiently wary.
Wind speed and direction are normally measured at the top of the mast, and the wind gradient must therefore be known in order to determine the mean wind speed incident on the sail.
...the shear wind gradient is rather weak....the energy gain...is due to a mechanism other than the wind gradient effect.
...there will usually be both a wind gradient and a temperature gradient.
Flow near the surface encounters small obstacles that change the wind speed and introduce random vertical and horizontal velocity components at right angles to the main direction of flow.
Flow near the surface encounters small obstacles that change the wind speed and introduce random vertical and horizontal velocity components at right angles to the main direction of flow.
