## Servicios Personalizados

## Revista

## Articulo

## Indicadores

- Citado por SciELO
- Accesos

## Links relacionados

- Citado por Google
- Similares en SciELO
- Similares en Google

## Compartir

## Gayana (Concepción)

##
*versión impresa* ISSN 0717-652X*versión On-line* ISSN 0717-6538

### Gayana (Concepc.) v.68 n.2 supl.TIProc Concepción 2004

#### http://dx.doi.org/10.4067/S0717-65382004000200010

Gayana 68(2) supl. t.I. Proc. : 60-61, 2004 ISSN 0717-652X
Dept. Atmospheric Sciences, Box 351640, University of Washington Seattle, WA 98105. rabrown@atmos.washington.edu
The University of Washington PBL model is a nonlinear similarity model (with organized large eddies in an equilibrium mean flow) suitable for km-scale to General Circulation Model or Climate numerical models. The theory and verification for this solution are now well established. Researchers who work with winds in the boundary layer with scales from point to 20-km regimes
Since Ekman found his wonderful logarithmic spiral solution for a Planetary Boundary Layer (PBL) in 1904, it has been used widely to model the boundary layer in a rotating frame of reference. The analytic solution for a PBL
where K is an eddy viscosity, and Unfortunately, the classic Ekman spiral velocity profile has rarely, if ever, been observed. The winds do spiral, turning clockwise from surface to geostrophic, as do the oceanic PBL flows. But they are not consistent, steady, or logarithmic. Most researchers assumed that the problem was variable turbulence, resulting in a highly variable eddy diffusivity, K(x,y,z,t). But for most large-scale numerical modelers, the great simplification of using a constant K overcame any worries about the problems with variable turbulence. In the 1960s it was found that the PBL solution was unstable to infinitesimal perturbations, hence the prescribed K solutions were not valid. In 1970 it was found that the perturbation grew to a state of equilibrium, where energy into the perturbation equaled energy back to the mean flow. This 'Coherent Structure' solution treated the finite perturbation explicitly as organized large eddies (OLE) in the form of longitudinal alternating vortices, or 'Rolls'. The nonlinear solution used K-theory for
where u This solution predicts that OLE are part of the solution for 80% of the observed conditions (slightly stably stratified to convective conditions). Unfortunately, it was difficult to observe and consequently it was not accepted as By the 1990s, Synthetic Aperture Radar (SAR) data from the Canadian Radarsat was showing linear effects on the ocean surface that corresponded to the nonlinear PBL solution. A statistical study showed these signatures to be present about 50% of the time. This is a sufficient, but not necessary, condition for the presence of Rolls. It is now apparent that the nonlinear solution is the prevailing solution for planetary boundary layer flow. This has profound consequences on 'surface truth' measurements and satellite wind applications. The effects are illustrated in Figure 1. Figure 1. The nonhomogenuities from Rolls.
1. The winds are non-homogeneous at the surface over a 0.1-5 km horizontal distance. Upper high velocity wind is 2. The average wind profile is 3. The PBL contains
Brown, R.A., 1970; A Secondary Flow Model for the Planetary Boundary Layer. Brown R.A. & Ralph Foster, 1994; On PBL Models for general circulation models, Brown, R.A., 2002; Scaling Effects in Remote Sensing Applications and the Case of Organized Large Eddies, Brown, R.A. 2004; Comments on the synergism between the analytic PBL model and remote sensing data, |