Potential Refractivity as a Similarity Variable
Abstract
The validity of a common radiometeorological application of Monin-Obukhov (M-0) similarity theory to potential refractivity (Chi), which is a nonlinear combination of theta and q, is determined by whether the properly nondimensionalized chi gradient is a universal function of Z/L. We develop expressions for the flux of chi (and its scaling parameter, chi*) in terms of temperature and moisture fluxes, and an M-O similarity expression for the vertical chi gradient. Results show that even is theta and q are accepted as exactly following M-O similarity expressions, when the surface layer is stable, chi does not obey such an expression. That is, when properly nondimensionalized, the vertical gradient of chi does not collapse to a single universal function of Z/L. The assumption that chi behaves as a similarity variable is approximately correct for well-mixed surface layers under unstable and near-neutral conditions. The gradient of chi is an important factor in determining microwave propagation conditions. We demonstrate the error induced in a simple algorithm when chi is assumed to obey M-O similarity theory. An alternative methodology, consistent with the application of similarity theory to theta and q, is then developed without requiring that chi itself satisfy similarity theory.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1992
- Accession Number
- ADA247116
Entities
People
- John Cook
- Stephen Burk