A numerical investigation of an asymptotically reduced model for quasigeostrophic
Rayleigh-Bénard convection is conducted in which the depth-averaged flows are numerically suppressed by modifying the governing equations. At the largest accessible values
of the Rayleigh number Ra, the Reynolds number and Nusselt number show evidence
of approaching the diffusion-free scalings of Re ∼ RaE/Pr and Nu ∼ Pr−1/2Ra3/2E2,
respectively, where E is the Ekman number and Pr is the Prandtl number. For large
Ra, the presence of depth-invariant flows, such as large-scale vortices, yield heat and
momentum transport scalings that exceed those of the diffusion-free scaling laws. The
Taylor microscale does not vary significantly with increasing Ra, whereas the integral
length scale grows weakly. The computed length scales remain O(1) with respect to the
linearly unstable critical wave number; we therefore conclude that these scales remain
viscously controlled. We do not find a point-wise Coriolis-inertia-Archimedean (CIA)
force balance in the turbulent regime; interior dynamics are instead dominated by horizontal advection (inertia), vortex stretching (Coriolis) and the vertical pressure gradient. A
secondary, subdominant balance between the Archimedean buoyancy force and the viscous
force occurs in the interior and the ratio of the root mean square (rms) of these two forces
is found to approach unity with increasing Ra. This secondary balance is attributed to
the turbulent fluid interior acting as the dominant control on the heat transport. These
findings indicate that a pointwise CIA balance does not occur in the high Rayleigh number
regime of quasigeostrophic convection in the plane layer geometry. Instead, simulations
are characterized by what may be termed a nonlocal CIA balance in which the buoyancy
force is dominant within the thermal boundary layers and is spatially separated from the
interior Coriolis and inertial forces.
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An Advanced Multiple‐Layer Canopy Model in the WRF Model With Large‐Eddy Simulations to Simulate Canopy Flows and Scalar Transport Under Different Stability Conditions
Forest canopies play a critical role in affecting momentum and scalar transfer. Although there have been recent advances in numerical simulations of turbulent flows and scalar transfer across plant canopies and the atmosphere interface, few models have incorporated all important physical and physiological processes in subcanopy layers. Here we describe and evaluate an advanced multiple‐layer canopy module (MCANOPY), which is developed based largely on the Community Land Model version 4.5 and then coupled with the Weather Research and Forecasting model with large‐eddy simulations (WRF‐LES). The MCANOPY includes a suite of subcanopy processes, including radiation transfer, photosynthesis, canopy layer energy balance, momentum drag, and heat, water vapor, and CO2exchange between canopy layers and the canopy atmosphere. Numerical schemes for heat and water transport in soil, ground surface energy balance, and soil respiration are also included. Both the stand‐alone MCANOPY and the coupled system (the WRF‐LES‐MCANOPY) are evaluated against data measured in the Canopy Horizontal Array Turbulence Study field experiment. The MCANOPY performs reasonably well in reproducing vertical profiles of mean and turbulent flows as well as second‐order statistical quantities including heat and scalar fluxes within the canopy under unstable stability conditions. The coupled WRF‐LES‐MCANOPY captures major features of canopy edge flows under both neutral and unstable conditions. Limitations of the MCANOPY are discussed for our further work. Our results suggest that our model can be a promising modeling system for a variety of applications to study canopy flows and scalar transport (e.g., CO2).
more » « less- NSF-PAR ID:
- 10460508
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Advances in Modeling Earth Systems
- Volume:
- 11
- Issue:
- 7
- ISSN:
- 1942-2466
- Page Range / eLocation ID:
- p. 2330-2351
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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