Performance of Different Sub-Grid-Scale Surface Flux Parameterizations for Urban and Rural Areas - Meteorological and Air Quality Models for Urban Areas - page 23

3.4 Conclusions

In this study, five case scenarios were simulated for different model resolutions
to determine the performance of two parameterization schemes (flux aggregation
with a blending height concept and parameter averaging) for sub-grid-scale sur-
face fluxes. In general, the performance differs between these two parameterisa-
tion schemes: better performance of the flux aggregation compared to the parameter
averaging is the general outcome. In addition, results are better for rural than for
urban sites. Improved performance for urban sites was found when the flux aggre-
gation was applied. Both methods seem to be resolution dependent, although the flux
aggregation is less so than the parameter averaging. However, the best parameteri-
zation for each situation could not be determined, as dynamic and thermodynamic
parameters perform differently for the same case. A number of additional factors
influence the evaluation, such as the forcing values that are used in the model via a
nudging technique and the interpolation of the model results to the routine observa-
tion stations. To derive a conclusion that is independent of these shortcomings more
case studies are necessary.

Acknowledgments This work is partly funded by the German Science Foundation under SCHL
499/1-1 and is a contribution to COST728.

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