13. Implication

Dust can be raised from the surface under dust-free condition in GCM simulations if the km-scale wind fluctuations associated with the daily thermal convection are considered in the calculation of surface stress (Fig.4, Fig.5). 

In the GCMs currently available, the incorporation of the effects of km-size thermal convection are not implemented. 

The parameterizations of sub-grid scale turbulence are inadequate for the km-size thermal convection, because they treat nearly isotropic eddies smaller than the model's vertical grid intervals, which is typically from 100 m to 1 km order in the lower atmosphere of GCM.

No information on the km-size convective wind is available by the convective adjustment, since it only ``adjusts'' the convectively unstable temperature gradient to the neutral one, without considering kinetic energy budget at all. 

In order to estimate the km-scale wind fluctuations in GCM correctly, it is necessary to develop a new parameterization of subgrid scale motions.

For the purpose, a convection resolving model like the 2-D model used in this study may be useful.

 LocalWords:  Savijarvi