A consistent vertical Bowen ratio profile in the planetary boundary layer

Autor(en)

Michael Hantel, Martin Steinheimer

Abstrakt

It has recently been suggested that the integrand b = -a'?' of the subgrid-scale conversion rate between available and kinetic energy has a measurable impact upon the Lorenz energy cycle. Here we discuss a technique to estimate this quantity within the lower part of an atmospheric column by relating b to the subgrid-scale fluxes of sensible and latent heat in form of their sum (the total convective heat flux, c, to be diagnosed from the pertinent energy law) and their ratio (a generalized Bowen ratio, ß, to be specified a priori). We focus on the frequently observed case that c vanishes at or above the top of the boundary layer, which implies that ß must be minus unity at the same level (referred to as 'critical pressure'). ß at the earth's surface is taken as measured. Observations suggest that the vertical curvature of the ß profile is negative in the boundary layer. We specify an analytic vertical profile ß (?) that interpolates these pieces of information; ? is a non-dimensional vertical coordinate. The pertinent thermodynamic energy law from which the column profile c(?) is gained (referred to here as convection equation) is driven by the (observed) grid-scale budget; the solution c is over most of the boundary layer quite insensitive to ß. It is only in the immediate vicinity of the critical pressure that c(?) becomes sensitively dependent upon ß(?); it actually turns infinite at this level (a 'pole' of the convection equation). We remove the pole through adjusting the critical pressure by a uniquely determined (and actually quite small) amount. This makes the ß profile consistent with the convection equation and with the other convective flux profiles, across the entire boundary layer. The remaining open parameter that cannot be fixed by our method is the curvature of the Bowen ratio profile. This exercise has implications for about a third of all atmospheric columns over the globe and thus may be relevant for the quantification of the global energy cycle. Œ Royal Meteorological Society, 2006.

Organisation(en)

Institut für Meteorologie und Geophysik

Journal

Quarterly Journal of the Royal Meteorological Society: a journal of the atmospheric sciences, applied meteorology, and physical oceanography

Band

132

Seiten

2459-2474

Anzahl der Seiten

16

ISSN

0035-9009

Publikationsdatum

2006

Peer-reviewed

Ja

ÖFOS 2012

1052 Meteorologie, Klimatologie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/cba09d33-7694-4d18-bbd7-01c50b426a14