On the role of roughness lengths in flux parameterizations of boundary-layer models |
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Authors: | Aloysius Kou-Fang Lo |
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Institution: | (1) Air Quality Modelling and Integration, Research Division, Atmospheric Environment Service, M3H 5T4 Downsview, Ontario, Canada |
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Abstract: | Flux-profile relationships based on surface-layer similarity theory are used to derive relationships between the Monin-Obukhov stability parameter = z/L and the bulk Richardson number Ri
b
. In contrast to previous studies, the roughness length for heat, z
0h
,is assumed unequal to the roughness length for momentum, z
0m
.For the stable case, an analytic expression of in terms of Ri
b
can be derived and in the unstable case, the solution is obtained through a simple iterative process.Errors introduced from the simplification of z
0h
= z
0m
are evaluated and are shown to be very significant in most cases. Thus, this error in many practical applications may invalidate the intended solution. |
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Keywords: | |
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