[RegCNET] what are the diffirences between Grell sc heme in RegCM3 and MM5V3?

[Moetasim]

Grell-AS scheme is, in fact, a simplified form of Arakawa-Schubert cumulus 
parametrization which uses one cloud type and includes mosit downdraft. 
The Grell scheme with quasi equilibrium closure assumption (AS) is similar to 
the Grell scheme in MM5, however, the value for the maximum allowable stable 
layer thickness between the level where updraft originates and the level of 
free convection is different in MM5 and RegCM3. The performace of Grell-AS 
scheme is somewhat sensitive to the choice of this lifiting depth  trigger (as 
named by Kain and Fritsch). 

The quasi closure assmpution used in Grell-AS relates the amount of convection 
to the rate of destabilization of the environment, which means that when large 
scale processes tend to increase the moist convective instability, the 
convective activity tends to dissipate this destabilization back to the 
equilibrium state. The dynamic and static contorl in Grell-AS  scheme are 
similar to AS other than that it includes downdraft in dynamic and static 
control.For the cumulus feedback, the latent heat released within the clouds 
doesn’t directly warm the environment, but it maintains the vertical mass flux 
of the clouds. Therefore, the convection influences the environment through 
environmental subsidence and detrainment at the top of the updraft or the 
bottom of the downdraft.



Moet


However, it uses same quasi equilibirum closure assumption as it is in the case 
of AS 


Quoting huyijiacat <huyijiacat0214 at 163.com>:

> RegCNet
>        Is the Grell scheme with two closures assumption in the RegCM3 the
> same with the Grell scheme in MM5V3? What assumption about the generation of
> the instability does MM5 Grell scheme utilize? Thank you!
>                                                           Hu.Y.J 
>  
>  
>