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  • 1
    Electronic Resource
    Electronic Resource
    Footprint prediction of scalar fluxes from analytical solutions of the diffusion equation (1990)
    Springer
    Boundary layer meteorology 50 (1990), S. 355-373 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The use of analytical solutions of the diffusion equation for ‘footprint prediction’ is explored. Quantitative information about the ‘footprint’, i.e., the upwind area most likely to affect a downwind flux measurement at a given height z, is essential when flux measurements from different platforms, particularly airborne ones, are compared. Analytical predictions are evaluated against numerical Lagrangian trajectory simulations which are detailed in a companion paper (Leclerc and Thurtell, 1990). For neutral stability, the structurally simple solutions proposed by Gash (1986) are shown to be capable of satisfactory approximation to numerical simulations over a wide range of heights, zero displacements and roughness lengths. Until more sophisticated practical solutions become available, it is suggested that apparent limitations in the validity of some assumptions underlying the Gash solutions for the case of very large surface roughness (forests) and tentative application of the solutions to cases of small thermal instability be dealt with by semi-empirical adjustment of the ratio of horizontal wind to friction velocity. An upper limit of validity of these solutions for z has yet to be established.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00120530
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  • 2
    Electronic Resource
    Electronic Resource
    Observations of fluxes over heterogeneous surfaces (1994)
    Springer
    Boundary layer meteorology 67 (1994), S. 345-367 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract This study analyzes data collected from repeated aircraft runs 30 m over alternating regions of irrigated and dry nonirrigated surfaces, each region on the order of 10 km across, during the California Ozone Deposition Experiment (CODE). After studying the scale dependence of the flow, the variables and their fluxes are decomposed into means for sublegs defined in terms of irrigated and nonirrigated regions and deviations from such subleg means. Since the repeated runs were flown over the same track, compositing the eight flight legs for each of the two days allows partial isolation of the influences of surface heterogeneity and transient mesoscale motions. A variance analysis is carried out to quantify the relative importance of surface heterogeneity and transient mesoscale motions on the variability of the turbulence fluxes. The momentum and ozone fluxes are more influenced by transient mesoscale motions while fluxes of heat, moisture and carbon dioxide are more influenced by surface heterogeneity. The momentum field is also influenced by a quasi-stationary mesoscale front and larger scale velocity gradients. For the present case, the mesoscale modulation of the turbulent flux is numerically more important than the direct mesoscale flux. This spatial modulation of the turbulent fluxes leads to extra Reynolds terms which act to reduce the area-averaged turbulent momentum flux and enhance the area-averaged turbulent heat flux.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00705438
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  • 3
    Electronic Resource
    Electronic Resource
    Boundary-layer heat and moisture budgets from fife (1990)
    Springer
    Boundary layer meteorology 50 (1990), S. 109-138 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Aircraft stacks were flown upwind and downwind of the First ISLSCP Field Experiment (FIFE) site in Kansas to measure the heat and moisture budgets of the boundary layer under fairly clear skies for four daytime periods. In this paper, we evaluate the terms in the conservation equation. The vertical flux divergence and advection do not account for the difference between surface and low-level aircraft flux estimates. Budget estimates of the surface fluxes using the aircraft data agree well with surface flux measurements, but extrapolation of the aircraft fluxes gives surface fluxes that are too low. With the 5 km cutoff filter used, the aircraft underestimate for sensible heat flux is about 40%, and for the latent heat flux about 30%. Part of the underestimation is attributable to long-wavelength contributions (longer than the 5 km filter), but more investigation is needed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00120520
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  • 4
    Electronic Resource
    Electronic Resource
    Aircraft measurements of CO2 exchange over various ecosystems (1984)
    Springer
    Boundary layer meteorology 29 (1984), S. 167-183 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The National Aeronautical Establishment's Twin Otter Atmospheric Research Aircraft has been equipped with open-path CO2 analyzers in order to obtain estimates of CO2 exchange over a corn field, a forest and a lake using the eddy correlation technique. On the 18th of August 1980, mean uptakes obtained over corn and forest were 12 and 8 kg CO2 ha-1 hr-1, respectively. On the 28th of August, mean uptakes obtained over corn, forest and the lake were 36, 14, and 1 kg CO2 ha-1 hr-1, respectively. The data are discussed in the light of general conditions on the two days.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00206829
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  • 5
    Electronic Resource
    Electronic Resource
    An evaluation of aircraft flux measurements of CO2, water vapor and sensible heat (1989)
    Springer
    Boundary layer meteorology 47 (1989), S. 55-69 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Ground-based flux measurements of carbon dioxide and water vapor integrate physiological processes taking place on a field scale. Aircraft flux measurements have recently been undertaken to attempt to widen the scope of applicability of such measurements. However, because of the intermittency of turbulent transfer, flux measurements must be averaged over long periods of time or long distances to give reproducible results. This requirement makes it difficult to relate aircraft flux measurements to local surface processes. Flux measurements of CO2, latent and sensible heat obtained from repeated passes in four directions and at three elevations over a homogeneous wheat-growing area are compared with ground-based measurements. Averages based on four runs of 4 km in length gave results consistent with ground-based measurements. The largest percentage differences were in the sensible heat flux. Cospectral analyses showed no significant high frequency losses for the data from flight levels of 25 and 50 m, but an underestimation of approximately 10% resulted at 10 m. Flight direction with respect to wind direction was relatively unimportant at 10 and 25 m but some effects were observed at 50 m. It was also shown that at 25 m, over a relatively smooth and homogeneous surface, the means of either three or four runs 4 km in length were similar to the means of 12–16 km runs. This confirms that at this altitude, most of the flux contribution is contained at wavelengths less than 4 km and that the mean of 3 to 4 passes accounts for most of the intermittency of turbulent transfer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00122322
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  • 6
    Electronic Resource
    Electronic Resource
    Turbulence above Lake Ontario: Velocity and scalar statistics (1976)
    Springer
    Boundary layer meteorology 10 (1976), S. 181-197 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Measurements of the fluctuations of wind, temperature and humidity were made with an instrumented aircraft at altitudes from 30 to 300m above Lake Ontario. The variations of the standard deviations of these fluctuations are examined. By applying Monin-Obukhov similarity theory based on local fluxes, it is shown that the vertical velocity, temperature and humidity fluctuations scale with the local Monin-Obukhov length. In the limit of free convection, 1/3 and −1/3 power laws are approached with constants of 1.2, 1.2, and 0.8 for vertical velocity, temperature and humidity, respectively. The von Karman scale lengths increase with height but were much larger than those found by Taylor et al. (1970).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229284
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  • 7
    Electronic Resource
    Electronic Resource
    Airborne and lidar measurements of aerosol and cloud particles in the troposphere over Alert Canada in April 1986 (1989)
    Springer
    Journal of atmospheric chemistry 9 (1989), S. 187-211 
    Details
    ISSN: 1573-0662
    Keywords: aerosol size distribution ; aerosol particle profiles ; aerosol scattering ; Arctic haze ; ice crystals ; lidar ; ozone profiles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract As a component of the Canadian Arctic Haze Study, held coincident with the second Arctic Gas and Aerosol Sampling Program (AGASP II), vertical profiles of aerosol size distribution (≥0.17 μm), light scattering parameters and cloud particle concentrations were obtained with an instrumented aircraft and ground-based lidar system during April 1986 at Alert. Northwest Territories. Average aerosol number concentrations range from about 200 cm−3 over the Arctic ice cap to about 100 cm−3 at 6 km. The aerosol size spectrum is virtually free of giant or coarse aerosol particles, and does not vary significantly with altitude. Most of the aerosol volume is concentrated in the 0.17–0.50 μm size range, and the aerosol number concentration is found to be a good surrogate for the SO4 = concentration of the Arctic haze aerosol. Comparison of the aircraft and lidar data show that, when iced crystal scattering is excluded, the aerosol light scattering coefficient and the lidar backscattering coefficient are proportional to the Arctic haze aerosol concentration. Ratios of scattering to backscattering, scattering to aerosol number concentration, and backscattering to aerosol number concentration are 15.3 steradians, 1.1×10−13 m2, and 4.8×10−15 m2 sr−1, respectively. Aerosol scattering coefficients calculated from the measured size distributions using Mie scattering agree well with measured values. The calculations indicate the aerosol absorption optical depth over 6 km to range between 0.011 and 0.018. The presence of small numbers of ice crystals (10–20 crystals 1−1 measured) increased light scattering by over a factor of ten.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00052832
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  • 8
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    Aircraft measurements of CO2 exchange over various ecosystems (1984)
    Springer
    Details
    Publication Date: 1984-06-01
    Print ISSN: 0006-8314
    Electronic ISSN: 1573-1472
    Topics: Geosciences , Physics
    Published by Springer
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  • 9
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    Observations of fluxes over heterogeneous surfaces (1994)
    Springer
    Details
    Publication Date: 1994-02-01
    Print ISSN: 0006-8314
    Electronic ISSN: 1573-1472
    Topics: Geosciences , Physics
    Published by Springer
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  • 10
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    Turbulence above Lake Ontario: Velocity and scalar statistics (1976)
    Springer
    Details
    Publication Date: 1976-05-01
    Print ISSN: 0006-8314
    Electronic ISSN: 1573-1472
    Topics: Geosciences , Physics
    Published by Springer
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