Unresolved spatial variability and process rates in large scale models
Robert Pincus and Stephen A. Klein
Journal of Geophysical Research, November 2000.
Vol. 105, pages 27059-27065.

Abstract

Prognostic cloud schemes in large scale models are typically formulated in terms of grid-cell average values of cloud condensate concentration q, although variability in q at spatial scales smaller than the grid cell is known to exist. Because the source and sink processes modifying q are nonlinear, the process rates computed using the mean value of q are biased relative to process rates which account for sub-grid scale variability. A preliminary assessment shows that these biases can modify instantaneous process rates by as much as a factor of two. Observations of q at a continental site suggest that the bias is avoided in current practice through the arbitrary tuning of model parameters. Models might be improved if sub-grid scale variability in q were explicitly considered; several approaches to this goal are suggested.

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