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Eddy diffusivities derived from a numerical model of the convective planetary boundary layer

Lamb, R. G. and Durran, D. R. (1978) Eddy diffusivities derived from a numerical model of the convective planetary boundary layer. Nuovo cimento della Società italiana di fisica. C, 1 (1). pp. 1-17. ISSN 0390-5551. https://resolver.caltech.edu/CaltechAUTHORS:20201104-075831510

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Abstract

Functional forms for the vertical eddy diffusivity K_z (z) are sought that optimize the performance of the K-theory diffusion equation. The method developed to determine the optimal diffusivity is first tested by applying it to analytic solution of the diffusion equation in which the functional form of the diffusivity is known precisely. In all test cases performed, the technique yields the correct K_z profile regardless of the initial estimate of K_z from which the technique’s search procedure begins. When applied to “observed” mean, cross-wind-integrated point source concentration fields derived from Lagrangian diffusion theory and data from a numerical turbulence model jointly, the technique yields optimal diffusivities that make the solution of the diffusion equation agree within ±20% of the “observed” values within the core of point source plumes. Expressed in terms of the convective-velocity scale w* and the mixed-layer depth z_i, the optimal diffusivity has a quasiuniversal form for atmospheric stabilities in the range z_i/L ⪯ -10 where L is the Monin-Obukhov length. The optimal diffusivity is found to be strongly dependent on the source hight. The K_z profiles derived for the two source heights z_s ∼ -0.025 z_i and z_s ∼ -0.25 z_i are of opposite shape, but they have comparable maximum values of K_z ∼ -0.25 w*z_i.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1007/bf02508043DOIArticle
Additional Information:© 1978 Società italiana di fisica. Received 26 November 1977.
Subject Keywords:Mixed Layer; Diffusion Equation; Initial Guess; Concentration Field; Eddy Diffusivity
Issue or Number:1
Record Number:CaltechAUTHORS:20201104-075831510
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20201104-075831510
Official Citation:Lamb, R.G., Durran, D.R. Eddy diffusivities derived from a numerical model of the convective planetary boundary layer. Il Nuovo Cimento C 1, 1–17 (1978). https://doi.org/10.1007/BF02508043
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106416
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:04 Nov 2020 20:50
Last Modified:04 Nov 2020 20:50

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