Towards a Validation of Total Turbulence Energy Conservation in Stable Stratification
Abstract
Monin Obukhov Similarity Theory (MOST) describes a linear scaling of turbulence with height in the weakly diabatic atmospheric boundary layer (ABL), but is inappropriate for diurnal transitions and in strongly stable conditions when turbulence is highly anisotropic and intermittent. MOST approximates scales of turbulence from near-surface buoyant and shear generation sources of turbulent kinetic energy (TKE) and assumes surface fluxes are constant through a portion of the lower ABL. Total turbulent energy (TTE) conservation, however, includes contributions from both turbulent potential energy (TPE) and TKE. TTE describes the energy exchange between a consumption of buoyancy to replenish TPE when surface stratification is high and the release of TPE by shear generation from large coherent eddies in low stability conditions. Measurement profiles of TTE over flat terrain provide a verification resource in developing improved turbulence parameterizations for numerical weather and climate prediction. A 10-m high-resolution turbulence tower was deployed over soybean stubble for the first stage of the FaNTASTIC project in the 2017-2018 winter season to determine TTE conservation characteristics near the surface. Turbulence and turbulent fluxes of momentum and heat are invariant with height during the night for neutral to weakly stable conditions. Categorizing stability according to an energy stratification parameter (Π=TPE/TKE) reveals a downward shifting in the maximum value of the vertical profile of potential temperature variance during strongly stable conditions (Π>0.12). An evaluation of the TTE budget over the 0.5-7.0 m tower layer provides additional details of the energy exchange. Recent measurements in the second deployment from both the 10-m short tower and from a nearby 120-m tall tower above a soybean canopy will expand upon this validation of TTE conservation with scaling considerations of large coherent eddies.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A13N3144R
- Keywords:
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- 3307 Boundary layer processes;
- ATMOSPHERIC PROCESSES;
- 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 3379 Turbulence;
- ATMOSPHERIC PROCESSES;
- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES