scholarly journals Areal-averaged trace gas emission rates from long-range open-path measurements in stable boundary layer conditions

2012 ◽  
Vol 5 (1) ◽  
pp. 1459-1496 ◽  
Author(s):  
K. Schäfer ◽  
R. H. Grant ◽  
S. Emeis ◽  
A. Raabe ◽  
C. von der Heide ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Land Surface ◽  
Stable Boundary Layer ◽  
Gradient Methods ◽  
Trace Gas ◽  
Emission Rates ◽  
Stable Boundary ◽  
Flux Gradient ◽  
Surface Emission ◽  
Flux Measurements

Abstract. Measurements of land-surface emission rates of greenhouse and other gases at large spatial scales (10 000 m2) are needed to assess the spatial distribution of emissions. This can be more readily done using spatial-integrating micro-meteorological methods than the widely-utilized small chamber measurements. Several micro-meteorological flux-gradient methods utilizing a non-intrusive path-averaging measurement method were evaluated for determining land-surface emission rates of trace gases under stable boundary layers. Successful application of a flux-gradient method requires confidence in the gradients of trace gas concentration and wind and in the applicability of boundary-layer turbulence theory. While there is relatively high confidence in flux measurements made under unstable atmospheres with mean winds greater than 1 m s−1, there is greater uncertainty in flux measurements made under free convective or stable conditions. The study involved quality-assured determinations of fluxes under low wind, stable or night-time atmospheric conditions when the continuous "steady-state" turbulence of the surface boundary layer breaks down and the layer has intermittent turbulence. Results indicate that the Monin-Obukhov similarity theory (MOST) flux-gradient methods that assume a log-linear profile of the wind speed and concentration gradient incorrectly determine vertical profiles and thus fluxes in the stable boundary layer.

scholarly journals Areal-averaged trace gas emission rates from long-range open-path measurements in stable boundary layer conditions

2012 ◽  
Vol 5 (7) ◽  
pp. 1571-1583 ◽  
Author(s):  
K. Schäfer ◽  
R. H. Grant ◽  
S. Emeis ◽  
A. Raabe ◽  
C. von der Heide ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Land Surface ◽  
Gradient Methods ◽  
Trace Gas ◽  
Emission Rates ◽  
Stable Boundary ◽  
Flux Gradient ◽  
Surface Emission ◽  
Stable Conditions ◽  
Flux Measurements

Abstract. Measurements of land-surface emission rates of greenhouse and other gases at large spatial scales (10 000 m2) are needed to assess the spatial distribution of emissions. This can be readily done using spatial-integrating micro-meteorological methods like flux-gradient methods which were evaluated for determining land-surface emission rates of trace gases under stable boundary layers. Non-intrusive path-integrating measurements are utilized. Successful application of a flux-gradient method requires confidence in the gradients of trace gas concentration and wind, and in the applicability of boundary-layer turbulence theory; consequently the procedures to qualify measurements that can be used to determine the flux is critical. While there is relatively high confidence in flux measurements made under unstable atmospheres with mean winds greater than 1 m s−1, there is greater uncertainty in flux measurements made under free convective or stable conditions. The study of N2O emissions of flat grassland and NH3 emissions from a cattle lagoon involves quality-assured determinations of fluxes under low wind, stable or night-time atmospheric conditions when the continuous "steady-state" turbulence of the surface boundary layer breaks down and the layer has intermittent turbulence. Results indicate that following the Monin-Obukhov similarity theory (MOST) flux-gradient methods that assume a log-linear profile of the wind speed and concentration gradient incorrectly determine vertical profiles and thus flux in the stable boundary layer. An alternative approach is considered on the basis of turbulent diffusivity, i.e. the measured friction velocity as well as height gradients of horizontal wind speeds and concentrations without MOST correction for stability. It is shown that this is the most accurate of the flux-gradient methods under stable conditions.

Impact of wind speeds on turbulent transport of carbon dioxide (CO2) fluxes at a tropical location in Ile - Ife, southwest Nigeria

2020 ◽  
Author(s):  
Theodora Bello ◽  
Adewale Ajao ◽  
Oluwagbemiga Jegede
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Land Surface ◽  
Stable Boundary Layer ◽  
Turbulent Transport ◽  
Strong Wind ◽  
Stable Boundary ◽  
Wind Speeds ◽  
Low Wind Speed ◽  
Tropical Area

<p>The study investigates impact of wind speeds on the turbulent transport of CO<sub>2 </sub>fluxes for a land-surface atmosphere interface in a low-wind tropical area between May 28<sup>th</sup> and June 14<sup>th</sup>, 2010; and May 24<sup>th</sup> and June 15<sup>th</sup>, 2015. Eddy covariance technique was used to acquire turbulent mass fluxes of CO<sub>2</sub> and wind speed at the study site located inside the main campus of Obafemi Awolowo University, Ile – Ife, Nigeria. The results showed high levels of CO<sub>2 </sub>fluxes at nighttime attributed to stable boundary layer conditions and low wind speed. Large transport and distribution of CO<sub>2 </sub>fluxes were observed in the early mornings due to strong wind speeds recorded at the study location. In addition, negative CO<sub>2 </sub>fluxes were observed during the daytime attributed to prominent convective and photosynthetic activities. The study concludes there was an inverse relationship between turbulent transport of CO<sub>2 </sub>fluxes and wind speed for daytime period while nighttime CO<sub>2</sub> fluxes showed no significant correlation.</p><p><strong>Keywords</strong>: CO<sub>2 </sub>fluxes, Wind speed, Turbulent transport, Low-wind tropical area, Stable boundary layer</p>

Modeling the Evolution of the Atmospheric Boundary Layer Coupled to the Land Surface for Three Contrasting Nights in CASES-99

2006 ◽  
Vol 63 (3) ◽  
pp. 920-935 ◽  
Author(s):  
G. J. Steeneveld ◽  
B. J. H. van de Wiel ◽  
A. A. M. Holtslag
Keyword(s):  
Boundary Layer ◽  
Land Surface ◽  
Stable Boundary Layer ◽  
Current Model ◽  
Atmospheric Stability ◽  
Surface Fluxes ◽  
Surface Energy Budget ◽  
Dominant Term ◽  
Stable Boundary ◽  
Underlying Soil

Abstract The modeling and prediction of the stable boundary layer over land is a persistent, problematic feature in weather, climate, and air quality topics. Here, the performance of a state-of-the-art single-column boundary layer model is evaluated with observations from the 1999 Cooperative Atmosphere–Surface Exchange Study (CASES-99) field experiment. Very high model resolution in the atmosphere and the soil is utilized to represent three different stable boundary layer archetypes, namely, a fully turbulent night, an intermittently turbulent night, and a radiative night with hardly any turbulence (all at clear skies). Each archetype represents a different class of atmospheric stability. In the current model, the atmosphere is fully coupled to a vegetation layer and the underlying soil. In addition, stability functions (local scaling) are utilized based on in situ observations. Overall it is found that the vertical structure, the surface fluxes (apart from the intermittent character) and the surface temperature in the stable boundary layer can be satisfactorily modeled for a broad stability range (at a local scale) with the current understanding of the physics of the stable boundary layer. This can also be achieved by the use of a rather detailed coupling between the atmosphere and the underlying soil and vegetation, together with high resolution in both the atmosphere and the soil. This is especially true for the very stable nights, when longwave radiative cooling is dominant. Both model outcome and observations show that in the latter case the soil heat flux is a dominant term of the surface energy budget.

Similarity Theory, Intermittency and Turbulences in the Stable Boundary Layer

2005 ◽  
Vol 277-279 ◽  
pp. 618-624 ◽  
Author(s):  
Kyungm Ja Ha ◽  
Kyung Eak Kim ◽  
Yu Kyung Hyun ◽  
Eun Hee Jeon ◽  
Larry Mahrt
Keyword(s):  
Boundary Layer ◽  
Stable Boundary Layer ◽  
Similarity Theory ◽  
Similarity Relation ◽  
Stability Parameters ◽  
Stable Boundary ◽  
Flux Gradient ◽  
Stable Conditions ◽  
New Treatments ◽  
Theory Z

The evaluation of similarity theory, z-less formulation of turbulence, and validation for various stable conditions is addressed with the use of CASES99 data over grassland. The dependence of the flux-gradient relationships on height and stability parameters is evaluated. For very stable conditions, similarity relation based on Monin-Obukhov theory is locally invalid and new treatments are required. The flux intermittency is recommended as a good indicator of stability for very thin stable boundary layer.

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