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  • Articles  (66)
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  • 1
    Electronic Resource
    Electronic Resource
    The depth of the daytime mixed layer at two coastal sites: A model and its validation (1982)
    Springer
    Boundary layer meteorology 24 (1982), S. 161-180 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A mathematical model of mixed-layer depth based on the thermodynamic analysis of Tennekes (1973) is generalized to include advection and subsidence. The effects of advection on mixed-layer depth have been modelled by setting the model equations in a Lagrangian frame, performing an approximate first integral in order to derive the spatial dependence of the model variables, and using these spatial forms to give a set of Eulerian equations. The effects of subsidence have been modelled by imposing a subsidence velocity on the top of the mixed layer as well as allowing subsidence-induced warming above that layer. The model thus derived consists of a system of non-linear differential equations which may be numerically solved to elucidate the temporal behaviour of mixed-layer depth. The boundary conditions necessary for such a solution are drawn from field studies at two coastal sites: one with a relatively simple coastline and essentially flat land under agricultural use, the other with a considerably more complex coastline, rolling relief and mixed land use (agricultural, parkland and urban). In both cases the modelled evolution of mixed-layer depth is in good agreement with the measured depth. The sensitivity of the model to all the input variables is investigated by examining the dependence of the maximum mixed-layer depth on each of these variables in an artificial set.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00121666
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  • 2
    Electronic Resource
    Electronic Resource
    Advectively-assisted evapotranspiration from irrigated urban vegetation (1979)
    Springer
    Boundary layer meteorology 17 (1979), S. 167-173 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The energy balance of an irrigated suburban lawn in Vancouver, B. C. during fair summer weather is presented. The results indicate that the evapotranspiration régime is assisted by advected energy from drier surfaces. Areal estimates of the suburban energy balance suggest that the latent heat flux from such irrigated surfaces is sufficient partially to compensate for the decrease in evapotranspiring areas by urbanization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00117976
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  • 3
    Electronic Resource
    Electronic Resource
    Velocity and temperature spectra and cospectra in an unstable suburban atmosphere (1989)
    Springer
    Boundary layer meteorology 47 (1989), S. 309-320 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Boundary-layer flow over very rough surfaces is poorly understood so the applicability of standard micrometeorological theory is uncertain. This study presents observations of the turbulent fluctuations of meteorological parameters over a suburban area. Even though the height of measurement is considered to be close to the junction between the inertial and roughness sub-layers, the wind and temperature spectra and the momentum and sensible heat flux cospectra are in good agreement with reference data from smoother surfaces. Recommendations are made concerning site requirements, height of measurement and averaging times for the study of turbulence and turbulent fluxes over suburban terrain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00122336
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  • 4
    Electronic Resource
    Electronic Resource
    Spatial variability of energy fluxes in suburban terrain (1991)
    Springer
    Boundary layer meteorology 54 (1991), S. 249-276 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Energy fluxes over an area of “homogeneous” suburban residential land-use in Vancouver, B.C., Canada are shown to vary by up to 25–40% within horizontal scales on the order of 102–103 m. Previously, variability of this magnitude has been expected to occur only at larger scales, between land-use zones or as urban-rural differences. In view of these findings, it is recognized that microadvective interaction between surface types at small scales may be important and can affect the energy balance even at larger scales. The present study discusses the small-scale spatial variability of energy fluxes and shows that it varies greatly for each term in the surface energy balance. Net radiation shows a relatively conservative behaviour (via albedo-surface temperature feedback) with little spatial variability. The turbulent fluxes (measured by eddy correlation at 28 m height), on the other hand, show a link between their temporal and spatial variability as the result of a temporally shifting source area which contains varying combinations of surface cover (using the dynamical source area concept of Schmid and Oke, 1990). As a result, part of the measured temporal variation is attributable to spatial differences in surface cover. Anthropogenic heat flux and storage heat flux (both modelled using a high resolution surface data-base) exhibit temporally varying spatial distributions. Their spatial pattern, however, is governed by nested scales of urban morphology (blocks, streets, properties, etc.). These differences in the source of variability between each component flux suggest a difficulty in the interpretation of the energy balance over urban areas, unless each term is spatially-averaged over the principal morphological units occurring in the area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00183956
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  • 5
    Electronic Resource
    Electronic Resource
    Validation of an urban canyon radiation model for nocturnal long-wave fluxes (1991)
    Springer
    Boundary layer meteorology 54 (1991), S. 347-361 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The urban canyon radiation model of Arnfield (1976, 1982) is validated using measurements of long-wave fluxes taken within a scaled down urban canyon constructed from concrete building blocks. A custom-designed traversing system allowed miniature radiometers to be automatically moved around the perimeter of a canyon cross-section, thereby providing for the validation of individual model grid-points. The agreement between measured and modelled radiation is generally very good. Some differences between the two over the canyon walls are attributed to difficulties in achieving precise instrument orientation. Model results derived from the measured surface temperature data are compared to results using various approximation schemes more likely to be used in practice. Approximations based on canyon surface temperatures are superior to those using air temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00118866
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  • 6
    Electronic Resource
    Electronic Resource
    Simulation of surface urban heat islands under ‘ideal’ conditions at night part 2: Diagnosis of causation (1991)
    Springer
    Boundary layer meteorology 56 (1991), S. 339-358 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A simple energy balance model which simulates the thermal regime of urban and rural surfaces under calm, cloudless conditions at night is used to assess the relative importance of the commonly stated causes of urban heat islands. Results show that the effects of street canyon geometry on radiation and of thermal properties on heat storage release, are the primary and almost equal causes on most occasions. In very cold conditions, space heating of buildings can become a dominant cause but this depends on wall insulation. The effects of the urban ‘greenhouse’ and surface emissivity are relatively minor. The model confirms the importance of local control especially the relation between street geometry and the heat island and highlights the importance of rural thermal properties and their ability to produce seasonal variation in the heat island. A possible explanation for the small heat
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00119211
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  • 7
    Electronic Resource
    Electronic Resource
    Eddy-correlation measurements of sensible heat fluxes over a grass surface (1974)
    Springer
    Boundary layer meteorology 7 (1974), S. 151-163 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Direct measurements of sensible heat fluxes were conducted over a grass surface at Ladner, British Columbia, using yaw-sphere-thermometer eddy-correlation systems. The results show that for half-hour averaging periods, there is no phase-lag between sensible heat and net radiation flux densities. Field comparison of two yaw-sphere-thermometer systems gave good and consistent agreement. At a height of 2 m above ground and a horizontal crosswind separation of 1.5 m, less than 5% variability was noted in the measured heat fluxes. For a 19-m horizontal separation, the variability was less than 20%. The aridity index (α) advanced by Priestley and Taylor (1972), is shown to be a potentially useful climatic indicator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227910
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  • 8
    Electronic Resource
    Electronic Resource
    Suburban-rural energy balance comparisons in summer for Vancouver, B.C. (1986)
    Springer
    Boundary layer meteorology 36 (1986), S. 351-369 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Simultaneous energy balance observations at a rural and a suburban site in Vancouver, B.C. during the summer of 1983 are presented. The study is a follow-up to that conducted in 1980. Many of the 1980 results were unexpected and the present study seeks to assess their representativeness. The net radiant, turbulent sensible, and rural soil heat flux densities were measured directly. The suburban heat storage was parameterized and the turbulent latent heat flux densities were resolved as residuals in the energy balances. The 1983 average diurnal energy partitioning for both sites was typical of those quoted in the literature, suggesting that the 1980 results represent an extreme case. Suburban-rural differences showed the suburban area to have a 4% increase in net radiation, a 51% increase in turbulent sensible heat, and a 46% decrease in turbulent latent heat flux density. The values of the average daytime Bowen ratio were 0.46 and 1.28 for the rural and suburban areas, respectively. The sensible heat flux density exhibited relatively large values in the late afternoon and remained directed upward on many summer evenings. Large day-to-day variability in the relative magnitude of the suburban turbulent fluxes may have been due to synoptic influences. In this environment, the turbulent surface and mixed layers are closely coupled because of the low aerodynamic resistance over the rough surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00118337
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  • 9
    Electronic Resource
    Electronic Resource
    Mixed-layer heat advection and entrainment during the sea breeze (1994)
    Springer
    Boundary layer meteorology 68 (1994), S. 139-158 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A model is developed to simulate the potential temperature and the height of the mixed layer under advection conditions. It includes analytic expressions for the effects of mixed-layer conditions upwind of the interface between two different surfaces on the development of the mixed layer downwind from the interface. Model performance is evaluated against tethersonde data obtained on two summer days during sea breeze flow in Vancouver, Canada. It is found that the mixed-layer height and temperature over the ocean has a small but noticeable effect on the development of the mixed layer observed 10 km inland from the coast. For these two clear days, the subsidence velocity at the inversion base capping the mixed layer is estimated to be about 30 mm s−1 from late morning to late afternoon. When the effects of subsidence are included in the model, the mixed-layer height is considerably underpredicted, while the prediction for the mean potential temperature in the mixed layer is considerably improved. Good predictions for both height and temperature can be obtained when values for the heat entrainment ratio,c, 0.44 and 0.68 for these two days respectively for the period from 1000 to 1300 LAT, were used. These values are estimated using an equation including the additional effects on heat entrainment due to the mechanical mixing caused by wind shear at the top of the mixed layer and surface friction. The contribution of wind shear to entrainment was equal to, or greater than, that from buoyant convection resulting from the surface heat flux. Strong wind shear occurred near the top of the mixed layer between the lower level inland flow and the return flow aloft in the sea breeze circulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00712668
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  • 10
    Electronic Resource
    Electronic Resource
    Suburban-rural energy balance comparisons for Vancouver, B.C.: An extreme case? (1983)
    Springer
    Boundary layer meteorology 26 (1983), S. 337-354 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Synchronous observations of the energy balances of a suburban and a rural area in the Vancouver region are used to investigate the impact of urbanization on energy exchange. Net radiation and rural soil heat flux density were directly measured, suburban heat storage was parameterized, and the turbulent heat flux densities were evaluated using the Bowen ratio-energy balance method. Most comparisons were conducted during a period of drying following an unusually wet early summer. These conditions produced atypical but very interesting results. With cloudless skies and high radiant input, suburban-rural differences of both net radiation and evapotranspiration were contrary to previous results and intuition. In both cases, suburban values were greater than their rural counterparts. In most respects the rural site behaved as expected, and the explanation for these findings is thought to be related to advective assistance of evapotranspiration from the suburban area. Under lesser radiant forcing the suburban budget acted in greater conformity with past experience and suburban-rural differences were similarly more in agreement with expectation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00119532
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