 |
| Titel |
Stably stratified canopy flow in complex terrain |
| VerfasserIn |
X. Xu, C. Yi, E. Kutter |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 13 ; Nr. 15, no. 13 (2015-07-10), S.7457-7470 |
| Datensatznummer |
250119881
|
| Publikation (Nr.) |
 copernicus.org/acp-15-7457-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| Stably stratified canopy flow in complex terrain has been considered a
difficult condition for measuring net ecosystem–atmosphere exchanges of
carbon, water vapor, and energy. A long-standing advection error in eddy-flux
measurements is caused by stably stratified canopy flow. Such a condition
with strong thermal gradient and less turbulent air is also difficult for
modeling. To understand the challenging atmospheric condition for eddy-flux
measurements, we use the renormalized group (RNG) k–ϵ
turbulence model to investigate the main characteristics of stably
stratified canopy flows in complex terrain. In this two-dimensional
simulation, we imposed persistent constant heat flux at ground surface and
linearly increasing cooling rate in the upper-canopy layer, vertically
varying dissipative force from canopy drag elements, buoyancy forcing induced
from thermal stratification and the hill terrain. These strong boundary
effects keep nonlinearity in the two-dimensional Navier–Stokes equations high
enough to generate turbulent behavior. The fundamental characteristics of
nighttime canopy flow over complex terrain measured by the small number of
available multi-tower advection experiments can be reproduced by this
numerical simulation, such as (1) unstable layer in the canopy and
super-stable layers associated with flow decoupling in deep canopy and near
the top of canopy; (2) sub-canopy drainage flow and drainage flow near the top
of canopy in calm night; (3) upward momentum transfer in canopy, downward
heat transfer in upper canopy and upward heat transfer in deep canopy; and
(4) large buoyancy suppression and weak shear production in strong stability. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|