Tuesday, 30 April 2002: 11:45 AM
Resolution dependence of parameterized physics inferred from nonhydrostatic model experiments
A two-dimensional cloud-resolving model (CRM) covering a horizontal domain of 512 km is used to examine the dependence of model physics on horizontal resolution in the meso-scale range. For this purpose the CRM is integrated with 2-, 8-, and 32-km resolutions under a variety of large-scale and surface conditions. The results show that when a cumulus parameterization is not included while individual clouds are not resolved, spurious meso-scale circulations develop as a substitute to cumulus convection. Consequently, systematic errors appear on large-scale thermodynamic fields although the domain averaged vertical profiles of the source and sink terms in the thermodynamic and water budget equations (�real physics�) hardly change with resolutions.
We then explore the resolution dependence of �apparent physics� needed by a model that does not resolve individual clouds. We diagnose the �apparent physics� from the difference between the result of the CRM and that of a dynamics model that is consistent with the CRM but without physics. It is found that the �apparent physics� is considerably different from the �real physics� even in the averages over the entire domain and it is resolution dependent. In the middle and upper troposphere, transports associated with microphysical processes are mainly responsible for this difference.
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