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  • 1
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Wavelength dependence as well as relative humidity dependence of aerosol extinction to backscatter ratio was examined. The extinction to backscatter ratio is essential in solving lidar signal and was estimated from aerosol size distribution and refractive index (which were derived from angular light scattering measurements) using the Mie scattering theory. The extinction to backscatter ratios were calculated for wavelengths of 355 nm, 532 nm, 694 nm and 1064 nm, the major laser wavelengths used for lidars, where the refractive indices were assumed to be constant with wavelength. p ]When relating the aerosol extinctionα 1 to the backscatterβ 1 with a functional form ofβ 1 ∼α 1 k 1, the exponentk 1 was evaluated by the least square method and tabulated for the four wavelengths. The extinction to backscatter ratio defined asS 1=α 1/β 1 was calculated and their dependence on the wavelength and relative humidity was examined. Their dependence on the relative humidity is small whileS 1 in the average takes the value of 66 (±17), 60 (±13), 52 (±13) and 42 (±11) for the wavelengths 355 nm, 532 nm, 694 nm and 1064 nm, respectively
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1349-9432
    Keywords: NO2 column density ; atmospheric aerosol ; solar spectrum ; sunphotometer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Ground-based, optical monitoring of the NO2 column density and aerosol optical thickness is described. The instrument consists of a solar radiation spectrometer and a conventional sunphotometer, both mounted on a sun-tracker and operated automatically. From daytime measurements in Chiba during the winter of 1998, variations of NO2 and aerosol are analyzed. Because of the capability of simultaneous, real time measurement, this method is particularly suitable for air pollution studies in city areas.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Boundary layer meteorology 59 (1992), S. 67-82 
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The spectral reflectance of the surface in an urbanized area was estimated through airborne measurements of the spectral upward flux of visible radiation in the range 475–750 nm. Atmospheric effects due to Rayleigh and Mie scattering were accounted for by using optical parameters to solve the radiative transfer equation. The values for these parameters were derived from measurements of the particle number concentration and size distribution. The results clearly show a difference in reflectance between urban and suburban areas. The difference in spectral reflectance decreases from the suburban to the urban area. In a metropolitan area, the surface reflectance generally decreases with urban development, and the global upward flux of visible radiation has a similar tendency. This trend supports the idea of a decrease in reflectance due to the modification of the surface structure.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Boundary layer meteorology 69 (1994), S. 201-213 
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The longwave upward radiation was calculated for an urban canopy by using a Monte Carlo model. The effects of the urban geometry were examined in terms of the fractional roof area, the height of the buildings and the emissivity. The urban canopy consists of identically sized buildings and the ground surfaces. The model allows for the temperature differences between the buildings and the ground surface and for multiple reflections in the canyon. The Monte Carlo results show that neglect of the geometric effects causes significant errors in calculated upward radiation: calculations with area-weighting of the radiation emitted from flat homogeneous surfaces are not appropriate. The upward flux is a nonlinear function of the fractional roof area, which may be approximated by a function of the square or cube of the fractional roof area. Neglect of the reflections by non-black surfaces (emissivity〈1) underestimates the upward flux by a few percent for a canopy of emissivity=0.9. Radiation effects due to multiple reflections in the canyon are parameterized by use of the view factor and the fractional roof area. The parameterization scheme yields accurate results.
    Type of Medium: Electronic Resource
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