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and a significant gap was found in the representation of both shallow and
deep convection between the cases with the 4-km grid and with the finer
grids. The simulated results suggest that a proper parameterization for
activating convection is required for the 4-km simulation.
By examining the resolution-dependence, we presented a simple
formulation using TKE for enhancing updraft and demonstrated that
the coarse-mesh simulation with this formulation significantly improves
the convective dust transport. Since the present modeling framework is
configured in an idealized way with full physics processes included as in
Takemi
,
6, 7
other complicating factors such as the data assimilation
technique and lateral boundary condition need not be taken into account.
Considering that a simulation with a grid size of 1-10 km in the
cloud-resolving range will be affordable at least in the regional-scale, a
parameterization for activating both shallow and deep convection should
be included in the CRM simulations. The most important point to be
stressed in this study is that the use of an eddy velocity scale, in the present
formulation or the other, is plausible for better representing the cumulus-
scale transport of dust aerosol. The present results further suggest that the
production of TKE in the closure scheme should be enhanced in the 4-km
simulation. A future study should conduct high resolution simulations of
both shallow and deep convection under various meteorological settings in
order to examine the validity of the present formulation and to revise the
parameterization based more on physics processes in the boundary layer.
et al.
Acknowledgments
This work was supported partly by Grant-in-Aid for Scientific Research
19740287 from the Japan Society for the Promotion of Science. The GFD
Dennou Library (http://www.gfd-dennou.org/index.html.en) was used for
drawing some of the figures.
References
1. C. Luo, N. Mahowald and C. Jones, Temporal variability of dust mobilization
and concentration in source regions,
J. Geophys. Res.
109
(2004) D20202, doi:
10.1029/2004JD004861.
2. J. Koch and N. O. Renno, The role of convective plumes and vortices on the
global aerosol budget,
Geophys. Res. Lett.
32
(2005) L18806, doi:10.1029/
2005GL023420.
