Документ взят из кэша поисковой машины. Адрес оригинального документа : http://hit-conf.imec.msu.ru/2012/abstracts/Kurbatsky.doc Дата изменения: Sun Jun 14 09:32:00 2015 Дата индексирования: Sat Apr 9 23:38:22 2016 Кодировка:

EFFICIENCY OF EDDY MIXING IN STABLY STRATIFIED ATMOSPHERIC BOUNDARY LAYER

Albert F. Kurbatskiy*?**, Lyudmila I. Kurbatskaya***

*Khristianovich Institute of Theoretical and Applied Mechanics SB RAS
630090 Novosibirsk
**Novosibirsk State University, 630090 Novosibirsk
***Institute of Computational Mathematics and Mathematical Geophysics SB
RAS
630090 Novosibirsk
E-mail: kurbat@itam.nsc.ru
________________________________________________________________________
__________________

Certain qualitative changes in turbulent eddy mixing in an atmospheric
boundary layer (ABL) during transitional regimes towards stronger
stratification are highlighted using numerical simulations with the
mesoscale RANS turbulence model. The eddy mixing efficiency for the stably
stratified atmospheric boundary layer is investigated as a function of the
gradient Richardson number ([pic]). In particular, the flux Richardson
number can be have non-monotonic (line 1 on Fig. 1), which has increased
with increasing of the gradient Richardson number, saturates and then
decreases after a value of [pic] around 1.0 (Fig. 1). Behavior of turbulent
eddy mixing coefficients for momentum and heat (Fig. 3) in this study is
consistent with the representation that the flow can sustain propagating
internal waves that can effectively transport momentum, but not heat. This
behavior is in good agreement with observational results for stably
stratified nocturnal boundary layer flows.
Keywords: Thermal stable atmospheric boundary layer, Flux Richardson
number, Eddy momentum and heat diffusivities, Modeling.

References
1] Pardyjak, E.R. et al. J. Fluid Mech. (2002), vol. 459, pp.307-316.
2] Mellor, G. L. & Yamada T. Rev. Geophysics Space Phys. (1982), vol. 20,
pp. 851-875.
3] Nakanishi, M. Boundary-Layer Meteorology (2001), vol. 99, pp. 349-378.
4] Monti P. Journal of the Atmospheric Sciences (2002), vol. 59, pp. 2513-
2534.

[pic]
Figure 1. Mixing efficiency ([pic]) as a function of gradient Richardson
number ([pic]): symbols are measurements data [1]; solid lines are the
simulation results; dotted and dash-dot lines are the parameterizations [2,
3].
[pic]
Figure 2. The variation of shear production (lines 1, 3) and buoyancy flux
(lines 2, 4) with the gradient Richardson number ([pic]): the lines 1, 2
are from [1], the lines 3, 4 are the simulation results.
[pic]
Figure 3. Scalings of turbulent eddy mixing coefficients [pic](line 1) and
[pic](line 2) (normalized by [pic]) with [pic]: solid lines are the
simulation results; the symbols are measurements data [4].

[pic]
Figure 4. The ratio of heat to momentum eddy diffusivity as a function of
the gradient Richardson number. The symbols are observation data [4]; the
solid line is a simulation result.