1. Upslope Flows

4. Prandtl (1942) one-dimensional theory Defant (1949) continued with Prandtl’s model Egger (1981) 2-D model

5. “Slope winds are spontaneous and intermittent in space and time. They are not continuous and stationary, but a succession of thermal bubbles from favorable, rocky, dry spots on the slope.” Slope flows react instantly to insolation. Upslope breezes start a few minutes after sunrise. (Vergeiner and Dreiseitl 1987)

6. “Slope wind field experiments, rare anyway, give random inconclusive results from which representative values of mass and heat transport in the slope layer cannot be derived.”

7.  1T11T1 2T22T2 x z T 1 > T 2  1 <  2 warmcold PGF Buoyancy Forces in Idealized Upslope Flow (Adapted from Atkinson 1981)

8. Air parcel above slopes surface has a higher potential temperature and therefore lower density than air parcel at same height above sea level over the plain (valley). Two forces acting on the parcel above the slope: 1.Pressure Gradient Force: pushing air towards the slope. 2.Buoyancy Force: drives air parcel vertically. Sum of both forces results in upward movement of air over slope, which is replaced by air coming from valley atmosphere. Forces in Idealized Upslope Flow

10. Banta 1984)

11. Reuten et al. 2005