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Boundary layer characteristics over areas of inhomogeneous surface fluxes

Boundary layer characteristics over areas of inhomogeneous surface fluxes,10.1175/1520-0450-34.2.559,Journal of Applied Meteorology,J. C. Doran,W. J.

Boundary layer characteristics over areas of inhomogeneous surface fluxes   (Citations: 32)
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This paper describes results from a June 1992 field program to study the response of the boundary layer over a site with well-defined extreme differences in sensible and latent heat fluxes over clearly separated areas, each with characteristic length scales of 10 km or more. The experiment region consisted of semiarid grassland steppe and irrigated farmland. Sensible heat flux maxima over the steppe regularly reached values in excess of 300 W m-2 and were typically a factor of 4 or more greater than those over the farmland. Two days were selected for analysis: one with moderate winds of 7-10 m s⁻¹ and one with lighter winds of 4-7 m s⁻¹ over the steppe. In both cases the wind directions were nearly perpendicular to the boundary between the steppe and farm. An analysis of potential temperature soundings showed that mixed-layer characteristics over both the farm and the steppe were largely determined by heating over the steppe, with advection from the steppe to the farm playing a significant role. On the day with the lighter winds, a secondary circulation related to the thermal contrasts between the two areas was observed. A simple conceptual model is described that predicts the extent of the cooler area required to generate such circulations. The observations illustrate how predictions of boundary layer structure in terms of local surface sensible heat fluxes may be compromised by advective effects. Such difficulties complicate efforts to obtain accurate representations of surface fluxes over inhomogeneous surfaces even if parameterizations of mesoscale contributions to the heat flux are included. 17 refs., 12 figs., 1 tab.
Journal: Journal of Applied Meteorology - J APPL METEOROL , vol. 34, no. 2, pp. 559-571, 1995
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    • ...These circulations enhance vertical fluxes of sensible heat (SH) and latent heat (LH) in PBL and may enhance convective clouds and precipitation over scales ranging from tens to hundreds of kilometers (Chen and Avissar 1994a, b; Doran et al. 1995; Avissar and Liu 1996; Baidya Roy and Avissar 2000; Wang et al. 2000; Weaver and Avissar 2001; Rife et al. 2001; Weaver et al. 2002)...
    • ...Such mesoscale circulations induced by landscape heterogeneity and their potential consequences in producing clouds and precipitation have been studied in previous field experiments (e.g., Physick and Tapper 1990; Segal and Arritt 1992; Mahrt et al. 1994; Doran et al. 1995), satellite observations (e.g., Rabin et al. 1990; Cutrim et al. 1995; Rabin and Martin 1996; Weaver and Avissar 2001), and numerical simulations (e.g., Baidya Roy and ...

    Ning Zhanget al. Effects of land-surface heterogeneity on numerical simulations of meso...

    • ...A similar mechanism has also been proposed as an explanation for observed differences in the convective boundary layer found during the Boardman Atmospheric Radiation measurement Regional Flux Experiment (BARFEX) (Segal et al. 1991; Doran et al. 1995)...

    Chris K. Wendtet al. Local boundary-layer development over burnt and unburnt tropical savan...

    • ...Experimental results over the heat-flux heterogeneities have indicated an increase in the heat flux downwind of the heterogeneity (Doran et al. 1995; Klaassen et al. 2002) due to advection effects...

    Thara V. Prabhaet al. Characteristics of secondary circulations over an inhomogeneous surfac...

    • ...Several studies with mesoscale models (Avissar and Chen 1993; Zeng and Pielke 1995; Lynn et al. 1995) have shown that fluxes associated with the mesoscale circulations may be important near the top of the boundary layer, but observational evidence of mesoscale circulations (Doran et al. 1995) and of their absence (Hubbe et al. 1997) leaves open the question of their impact on the regional or climate scale...

    Andrea Molodet al. A New Look at Modeling Surface Heterogeneity: Extending Its Influence ...

    • ...coast (Mahrt et al, 1994; Doran et al, 1995)...

    J.-F. Miaoet al. Impacts of topography and land degradation on the sea breeze over east...

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