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Available from: Bert Holtslag, Oct 09, 2015
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    • "Turbulent transport between the surface and the atmosphere ceases, sometimes referred to as 'crashing' (Derbyshire 1999). Van de Wiel et al. (2002) identifies this flow regime as a 'radiative regime'. Both of these studies elucidate the flow regimes in relation to dynamic stability, as related to surface radiative forcing, the horizontal pressure gradient, thermal properties of the surface and surface roughness. "
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    ABSTRACT: The stable nocturnal boundary layer is commonly viewed or modelled as a balance between the temperature tendency (cooling) and vertical heat-flux divergence. Sometimes the radiative-flux divergence is also included. This perspective has dictated the design of field experiments for investigating stable nocturnal boundary layers. Tower-based micrometeorological data from three field campaigns are analysed to evaluate the vertically integrated sensible-heat budget for nocturnal stable conditions. Our analysis indicates frequent occurrence of large imbalance between the temperature tendency and vertical heat-flux divergence terms. The values of the radiative-flux divergence are generally too small and sometimes of the wrong sign to explain the residual. An analysis of random flux errors and uncertainties in the tendency term indicate that such errors cannot explain large imbalances, suggesting the importance of advection of temperature or possibly the divergence of mesoscale fluxes. The implied role of advection is consistent with circumstantial evidence. Even weak surface heterogeneity can create significant horizontal gradients in stable boundary layers. However, it is shown that existing field data and observational strategy do not allow adequate evaluation of advection and mesoscale flux divergence terms.
    Quarterly Journal of the Royal Meteorological Society 01/2006; 132(615). DOI:10.1256/qj.05.50 · 3.25 Impact Factor
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    • "Ook op andere locaties in Nederland werd dit gedrag in die nacht waargenomen. Het getoonde gedrag kan grotendeels worden verklaard met een relatief simpel conceptueel model dat door een van de promovendi van de leerstoelgroep ontwikkeld is (van de Wiel et al, 2002). "
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    ABSTRACT: In this paper a classification of stable boundary layer regimes is presented based on observations of near-surface turbulence during the Cooperative Atmosphere-Surface Exchange Study-1999 (CASES-99). It is found that the different nights can be divided into three subclasses: A turbulent regime, an intermittent regime, and a radiative regime, which confirms the findings of two companion papers that use a simplified theoretical model (it is noted that its simpliflied structure limits the model generality to near-surface flows). The papers predict the occurrence of stable boundary layer regimes in terms of external forcing parameters such as the (effective) pressure gradient and radiative forcing. The classification in the present work supports these predictions and shows that the predictions are robust in a qualitative sense. As such, it is, for example, shown that intermittent turbulence is most likely to occur in clear-sky conditions with a moderately weak effective pressure gradient. The quantitative features of the theoretical classification are, however, rather sensitive to (often uncertain) local parameter estimations, such as the bulk heat conductance of the vegetation layer. This sensitivity limits the current applicability of the theoretical classification in a strict quantitative sense, apart from its conceptual value.
    Journal of the Atmospheric Sciences 10/2003; 60(20):2509-2522. DOI:10.1175/1520-0469(2003)060<2509:ITITSB>2.0.CO;2 · 3.14 Impact Factor
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