A study of a fair weather boundary layer in TOGA-COARE: Parameterization of surface fluxes in large scale and regional models for light wind conditions

Authors: Mondon S.1; Redelsperger J.L.1

Source: Boundary-Layer Meteorology, Volume 88, Number 1, July 1998 , pp. 47-76(30)

Publisher: Springer

Key:
Free Content - Free Content
New Content - New Content
Subscribed Content - Subscribed Content
Free Trial Content - Free Trial Content

Abstract:

The study focuses on a way to parameterize the effect of subgrid scale convective motions on surface fluxes in large scale and regional models for the case of light surface winds. As previously proposed, these subgrid effects are assumed to scale with the convection intensity through the relationship: Umacr^2=U_0^2+(betaw_*)^2 where Umacr is the mean velocity of the wind, U_0 the velocity of the mean wind, w_* the free convection velocity, and beta an empirical coefficient to be determined. Both observations and numerical simulation are presently used to determine the free convection coefficient beta.

Large eddy simulation of a fair weather convective boundary layer case observed during TOGA-COARE is performed. Comparisons between observations and the simulation of surface properties and vertical profiles in the planetary boundary layer are presented. The simulated vertical turbulent fluxes of heat, moisture and buoyancy range well within estimates from aircraft measurements.

The most important result is that the `true' free convection coefficient beta, directly estimated from simulation, leads to a value of 0.65, smaller than the ones estimated from temporal and spatial variances. Using observations and simulation, estimates of beta from temporal and spatial variances are obtained with similar values ap 0.8. From both theoretical derivations and numerical computations, it is shown that estimates of the `true' beta from variances are possible but only after applying a correction factor equal to 0.8. If this correction is not used, beta is overestimated by about 25%. The time and space sampling problem is also addressed in using numerical simulations.

Keywords: Convective boundary layer; Numerical model; Parameterization; Surface fluxes; TOGA-COARE

Language: English

Document Type: Regular paper

Affiliations: 1: Centre National de Recherches Météorologiques, Météo France & CNRS, France

The full text electronic article is available for purchase. You will be able to download the full text electronic article after payment.

$47.00 plus tax      Refund Policy

 

OR

Back to top

Key:
Free Content - Free Content
New Content - New Content
Subscribed Content - Subscribed Content
Free Trial Content - Free Trial Content
Share this item with others: These icons link to social bookmarking sites where readers can share and discover new web pages.
Page Help Click here for Page Help
Shopping cart
Tools
Sign in






Need to register?
Sign up here
Text size: A | A | A | A