A General Model of the Atmospheric Scattering in the Wavelength Interval 300 - 1100nm (original) (raw)
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Journal of Modern Optics, 1994
Mathematical models are developed to characterize propagation through a turbid medium at three different wavelengths in the visible and near infrared spectral range . These models are based upon relations between the temporal, angular, and spatial spread of electromagnetic unpolarized radiation, geometrical path length, particle size distribution, and the medium's propagation parameters such as Mie scattering, and absorption coefficients, Mie phasefunction, and optical thickness . Calculations of the radiation characteristics were carried out using Monte Carlo simulations . Here, atmospheric particulates are used to model turbid media for optical thickness between 1 and 6, emphasizing optical communication applications, The advantage of this work is the ability to predict simply and in real time important radiation parameters relevant to any optical communication system . Results indicate very high correlation between optical thickness and propagation characteristics . For transmission, comparison is made to Bucher's model . Results are similar except for absorption effects which are not included in Bucher's model . Some important conclusions are derived such as the prediction that it is advantageous to use longer wavelength radiation through the atmosphere . In addition, there is a very dominant back scattering effect, involving up to 50% of transmitted power for optical densities as low as 6 . On the other hand, power density of received scattered light is very low for conventional distances relevant to satellite optical communication, and can be neglected . On the basis of simulation results, the received radiation is of unscattered light only for any optical communication application . The dominant mechanism relating to radiation attenuation is scattering rather than absorption .
Journal of the Atmospheric Sciences, 2002
The model proposed provides for reconstruction of the aerosol scattering coefficient profile. In so doing one needs for, as input data, the scattering coefficient value of the dry aerosol substance at the near ground level measured at the wavelength of 0.52 µm, relative air humidity, aerosol optical thickness, and mean temperature of air in the low troposphere. The model assumes the account for correlation between the values of scattering coefficient at different altitudes, as well as the dependence of the height of mixing layer on the heating of the lower atmospheric layers. The errors in reconstructing the vertical profiles of the aerosol scattering coefficient are analyzed for different ways of taking into account the external factors and input parameters. It is shown that the use of such an approach provides a decrease in the rms error in reconstruction even at this stage approximately by 30% for winter and by 3 to 4 times for summer in comparison with the rms deviation of this parameter in the initial data sets.
Scattering Effect on Terrestrial Free Space Optical Signal in Tropical Weather Condition
Free space optical communication (FSO) is the future technology for high speed and highly secure data communication. Terrestrial operation is one of the applications of FSO where data communication is established between ground to ground platforms. But the FSO has to face challenges against atmosphere in form of attenuation and turbulent channel. The atmospheric attenuation is mainly caused by scattering. The atmospheric attenuation affects the overall quality of the system. In this paper the effects of scattering on the terrestrial FSO which have a link length of 2 km, is simulated using OptiSystem 7.0. The outcome of this simulation will prove that an optical source of 1550 nm is very useful for data transmission of maximum 5 GBits/s in the local weather with a bit rate error less than 10 −9. The results can be also used to determine FSO parameters like optical transmitted power, aperture radius of transmitter and receiver, gain of the optical signal etc for a terrestrial link of 2 km range.
Analytic spectral functions for atmospheric transmittance calculations
Applied Optics, 1988
Analytic formulas for the transition energies, intensities, and spectral absorption coefficients of the big (most intense) band systems of H 2 0 and CO 2 are presented. Analytic spectral representations of the Chappuis band of 03, three bands of 02, and two bands of CH 4 are also given. These inputs in conjunction with band model transmission formulas can be used with spectral functions for the extraterrestrial solar irradiance and Rayleigh and aerosol attenuation for engineering-type calculations of the direct solar spectral irradiance reaching the ground between 0.35 and 4.5 um. Several algorithms may then be used for estimating the diffuse irradiance.
Atmospheric transmission in the 1 to 14 μ region
Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, 1951
The transmission of the atmosphere for radiation of wave-lengths between 1 and 14 μ has been determined at sea-level, and its dependence on meteorological conditions investigated. Measurements have been made over paths of 2264 and 4478 yd., and the correlation with visibility and humidity studied in detail at four chosen wave-lengths, 2.18, 3.61, 10.01 and 11.48 μ ,. Spectral transmission curves for typical conditions have been recorded for the complete range 1 to 14 μ and, in addition to the numerous absorption bands due to water vapour arid carbon dioxide, some bands caused by the rarer constituents, in particular N 2 O and HDO, have been observed. Throughout the wave-length range investigated, the transmission varies with the visibility, the effect being less marked at the longer wave-lengths. For example, when, under typical conditions, the visual transmission falls from 75 to 50% per sea mile, the corresponding change at 2.18 μ is from 85 to 73%, and at 10.01 μ from 87 to 83%. ...
Improved algorithm for calculations of Rayleigh-scattering optical depth in standard atmospheres
Applied Optics, 2005
Precise calculations of the total Rayleigh-scattering optical depth have been performed at 88 wavelengths ranging from 0.20 to 4.00 m for the six well-known standard atmosphere models by integrating the volume Rayleigh-scattering coefficient along the vertical atmospheric path from sea level to a 120-km height. The coefficient was determined by use of an improved algorithm based on the Ciddor algorithm [Appl. Opt. 35, 1566], extended by us over the 0.20-0.23-m wavelength range to evaluate the moist air refractive index as a function of wavelength, air pressure, temperature, water-vapor partial pressure, and CO 2 volume concentration. The King depolarization factor was also defined taking into account the moisture conditions of air. The results indicate that the influence of water vapor on Rayleigh scattering cannot be neglected at tropospheric altitudes: for standard atmospheric conditions represented in terms of the U.S. Standard Atmosphere (1976) model, the relative variations produced by water vapor in the Rayleigh scattering parameters at a 0.50-m wavelength turn out to be equal to Ϫ0.10% in the moist air refractivity at sea level (where the water-vapor partial pressure is equal to Ϸ7.8 hPa), Ϫ0.04% in the sea-level King factor, Ϫ0.24% in the sea-level Rayleigh-scattering cross section, and Ϫ0.06% in the Rayleigh-scattering optical depth.
Absorption Profile of a Planetary Atmosphere: A Proposal for a Scattering Independent Determination
Applied Optics, 1972
The use of scattering theory to infer atmospheric optical parameters requires the separation of absorption and scattering. It is demonstrated that a gradient flux relation exists that would provide the absorption (altitude) profile independently of scattering and irrespective of the state of polarization of the light field. The relation is derived for an atmosphere of plane-parallel or spherical geometry and for broad (continuum) and narrow (spectral line) frequency bands. The results are shown to hold, in particular, for the polarizations induced by both Rayleigh and Mie scattering in the field. Experimental setups are proposed for each of the cases considered of atmospheric geometry and frequency bandwidth. A final discussion considers the relevance of the present determination of the atmospheric absorption profile to the related problems of aerosol relative concentration, interpretation of radiometric and spectrometric data formed in the presence of scattering, clouds morphology, and radiative heat budget of the atmosphere.