Stable Atmospheric Boundary-Layer Experiment in Spain (SABLES 98): A Report

Cuxart, Joan; Yagüe, Carlos; Morales, Guillermo A.; Terradellas, Enric; Orbe, J.; Calvo, Javier Bartolome; Fernández, Alberto; Soler, M. R.; Infante, C.; Buenestado, P.; Espinalt, A.; Joergensen, H.; Rees, Julia M.; Vila, José Leandro Cardoso Rivera; Redondo, J. M.; Cantalapiedra, Inma Rodríguez; Conangla, L.

doi:10.1023/a:1002609509707

Cited by 119 publications

(100 citation statements)

References 51 publications

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“…Turbulence that is primarily generated aloft (e.g. by shear associated with a low-level jet or gravity waves) is termed "upside-down" mixing, and may be partially or completely detached from the surface and confined to thin elevated layers (Ohya et al 1997;Ohya 2001;Mahrt et al 1998;Cuxart et al 2000;Ha and Mahrt 2001;Mahrt and Vickers 2002;Conangla and Cuxart 2006). In such cases, the traditional concept of a boundary layer breaks down altogether (Mahrt 1999).…”

Section: Turbulent Mixing In the Nocturnal Stable Boundary Layer (Sbl)mentioning

confidence: 99%

Bulk Mixing and Decoupling of the Nocturnal Stable Boundary Layer Characterized Using a Ubiquitous Natural Tracer

Williams

Chambers

Griffiths

2013

Boundary-Layer Meteorol

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Vertical mixing of the nocturnal stable boundary layer (SBL) over a complex land surface is investigated for a range of stabilities, using a decoupling index (0 < D rb < 1) based on the 2-50 m bulk gradient of the ubiquitous natural trace gas radon-222. The relationship between D rb and the bulk Richardson number (R ib ) exhibits three broad regions: (1) a well-mixed region (D rb ≈ 0.05) in weakly stable conditions (R ib < 0.03); (2) a steeply increasing region (0.05 < D rb < 0.9) for "transitional" stabilities (0.03 < R ib < 1); and (3) a decoupled region (D rb ≈ 0.9-1.0) in very stable conditions (R ib > 1). D rb exhibits a large variability within individual R ib bins, however, due to a range of competing processes influencing bulk mixing under different conditions. To explore these processes in R ib -D rb space, we perform a bivariate analysis of the bulk thermodynamic gradients, various indicators of external influences, and key turbulence quantities at 10 and 50 m. Strong and consistent patterns are found, and five distinct regions in R ib -D rb space are identified and associated with archetypal stable boundary-layer regimes. Results demonstrate that the introduction of a scalar decoupling index yields valuable information about turbulent mixing in the SBL that cannot be gained directly from a single bulk thermodynamic stability parameter. A significant part of the high variability observed in turbulence statistics during very stable conditions is attributable to changes in the degree of decoupling of the SBL from the residual layer above. When examined in R ib -D rb space, it is seen that very different turbulence regimes can occur for the same value of R ib , depending on the particular combination of values for the bulk temperature gradient and wind shear, together with external factors. Extremely low turbulent variances and fluxes are found at 50 m height when R ib > 1 and D rb ≈ 1 (fully decoupled). These "quiescent" cases tend to occur when geostrophic forcing is very weak and subsidence is present, but are not associated with the largest bulk temperature gradients. Humidity and net radiation data indicate the presence of low cloud, patchy fog or dew, any of which may aid decoupling in these cases by preventing temperature gradients from increasing sufficiently to favour gravity wave activity. The largest temperature gradients in our dataset are actually associated with smaller values of the decoupling index (D rb < 0.7), indicating the presence of mixing. Strong evidence is seen from enhanced turbulence levels, fluxes and submeso activity at 50 m, as well as high temperature variances and heat flux intermittencies at 10 m, suggesting this region of the R ib -D rb distribution can be identified as a top-down mixing regime. This may indicate an important role for gravity waves and other wave-like phenomena in providing the energy required for sporadic mixing at this complex terrain site.

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Section: Turbulent Mixing In the Nocturnal Stable Boundary Layer (Sbl)mentioning

confidence: 99%

Bulk Mixing and Decoupling of the Nocturnal Stable Boundary Layer Characterized Using a Ubiquitous Natural Tracer

Williams

Chambers

Griffiths

2013

Boundary-Layer Meteorol

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“…The Minnesota dataset was one of the first [7] and was also used in N84. Recently some more data became available [8,18,21], but these studies often focussed on special phenomena in the SBL such as intermittency, gravity waves, inertial oscillation, katabatic flow or other heterogeneous effects.…”

Section: Resultsmentioning

confidence: 99%

Large Eddy Simulation of the Stable Boundary-Layer: A Retrospect to Nieuwstadt’s Early Work

Dop

Axelsen

2007

Flow Turbulence Combust

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Observations and theory presented in a paper by Nieuwstadt (J Atmos Sci 41:2202-2216, 1984 are reviewed and reconsidered. We have used a large eddy simulation (LES) model to make a 10-h rerun. Averaged results obtained for the last hour were considered to be representative for the wind-driven, quasi steady nocturnal boundary layer as reported in Nieuwstadt's paper. The turbulence characteristics found with the LES model are in good to excellent agreement with the majority of the observations and confirms the uniqueness of the dataset, though the scatter in the data is (understandably) large. Laboratory experiments of the stable boundary layer might reduce the uncertainty in existing data and should be encouraged. The concept of local scaling, introduced by Nieuwstadt in 1984 was also confirmed by our simulations. Nieuwstadt's experiment and local scaling theory of the SBL were a major achievement and an important contributions to our understanding of the SBL.

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“…SABLES98 (Stable Atmospheric Boundary Layer Experiment in Spain 1998) data (Cuxart et al, 2000) from a sonic anemometer (20 Hz sampling rate) at 32 m were used. This field campaign took place in September 1998 (from 10 to 28) at the Research Centre for the Lower Atmosphere (CIBA) which is situated on the Northern Spanish Plateau.…”

Section: Datamentioning

confidence: 99%

“…From the actual measured temperature and horizontal velocity data, the gradient Richardson number is defined (Cuxart et al, 2000) as:…”

Section: Datamentioning

confidence: 99%

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Structure function analysis and intermittency in the atmospheric boundary layer

Vindel

Yagüe

Redondo

2008

Nonlin. Processes Geophys.

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Abstract. Data from the SABLES98 experimental campaign (Cuxart et al., 2000) have been used in order to study the relationship of the probability distribution of velocity increments (PDFs) to the scale and the degree of stability. This connection is demonstrated by means of the velocity structure functions and the PDFs of the velocity increments.Using the hypothesis of local similarity, so that the third order structure function scaling exponent is one, the inertial range in the Kolmogorov sense has been identified for different conditions, obtaining the velocity structure function scaling exponents for several orders. The degree of intermittency in the energy cascade is measured through these exponents and compared with the forcing intermittency revealed through the evolution of flatness with scale.The role of non-homogeneity in the turbulence structure is further analysed using Extended Self Similarity (ESS). A criterion to identify the inertial range and to show the scale independence of the relative exponents is described. Finally, using least-squares fits, the values of some parameters have been obtained which are able to characterize intermittency according to different models.

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Stable Atmospheric Boundary-Layer Experiment in Spain (SABLES 98): A Report

Cited by 119 publications

References 51 publications

Bulk Mixing and Decoupling of the Nocturnal Stable Boundary Layer Characterized Using a Ubiquitous Natural Tracer

Bulk Mixing and Decoupling of the Nocturnal Stable Boundary Layer Characterized Using a Ubiquitous Natural Tracer

Large Eddy Simulation of the Stable Boundary-Layer: A Retrospect to Nieuwstadt’s Early Work

Structure function analysis and intermittency in the atmospheric boundary layer

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