Effects on the winds and windstress at the surface

Figure 3e shows the differences in anemometer-level and lowest modellevel windspeeds between the perturbed and the control simulations in the Bernese Alps on February 27, 1990. Over glaciers and the transition zone, the anemometer-level windspeed increased more than the lowest model-level windspeed, AVanem = 4.1 ms'1 over glaciers, and AVimcm = 2.6 m s"1 in the transition zone compared to for both on average during this day. This increase of the lowest model-level windspeed indicates that the vertical gradient of the wind is also increasing in the surface layer. Figure 3f shows the differences in the surface wind stress. The average wind blowing in the southeast direction increased its speed in the perturbed simulation but the stress components are effectively decreasing by 2.6 and 1.3 Pa over glaciers, and by 0.9 and 0.4 Pa over the transition zone respectively in both x and y directions.

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