<i>Optics of the Atmosphere: Scattering by Molecules and Particles</i>

McCartney, Earl J.; Hall, Freeman F.

doi:10.1063/1.3037551

Cited by 388 publications

(405 citation statements)

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“…The parameters characterizing this type of scattering are well documented in the literature (e.g., McCartney, 1976). The total cross section for Rayleigh scattering in a standard atmosphere (15 • C and 1013.25 hPa), σ std m , is calculated as in Bucholtz (1995), i.e., without the approximation for the refractive index.…”

Section: Molecular Referencementioning

confidence: 85%

A permanent Raman lidar station in the Amazon: description, characterization, and first results

Barbosa¹,

Barja²,

Pauliquevis

et al. 2014

Atmos. Meas. Tech.

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Abstract.A permanent UV Raman lidar station, designed to perform continuous measurements of aerosols and water vapor and aiming to study and monitor the atmosphere from weather to climatic time scales, became operational in the central Amazon in July 2011. The automated data acquisition and internet monitoring enabled extended hours of daily measurements when compared to a manually operated instrument. This paper gives a technical description of the system, presents its experimental characterization and the algorithms used for obtaining the aerosol optical properties and identifying the cloud layers. Data from one week of measurements during the dry season of 2011 were analyzed as a mean to assess the overall system capability and performance. Both Klett and Raman inversions were successfully applied. A comparison of the aerosol optical depth from the lidar and from a co-located Aerosol Robotic Network (AERONET) sun photometer showed a correlation coefficient of 0.86. By combining nighttime measurements of the aerosol lidar ratio (50-65 sr), back-trajectory calculations and fire spots observed from satellites, we showed that observed particles originated from biomass burning. Cirrus clouds were observed in 60 % of our measurements. Most of the time they were distributed into three layers between 11.5 and 13.4 km a.g.l. The systematic and long-term measurements being made by this new scientific facility have the potential to significantly improve our understanding of the climatic implications of the anthropogenic changes in aerosol concentrations over the pristine Amazonia.

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Section: Molecular Referencementioning

confidence: 85%

A permanent Raman lidar station in the Amazon: description, characterization, and first results

Barbosa¹,

Barja²,

Pauliquevis

et al. 2014

Atmos. Meas. Tech.

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“…Rayleigh scattering [McCartney, 1976] There is a rapid variation in the vapor absorption strength, while that due to drop absorption is more gradual. The spectral variation in cloud absorption is dictated by the much finer variation in the water vapor optical depth, and the degree of accuracy that can be achieved in parameterizing it depends on the choice of the spectral band delimiters.…”

Section: Rayleigh Scatteringmentioning

confidence: 99%

A new multiple‐band solar radiative parameterization for general circulation models

Freidenreich¹,

Ramaswamy²

1999

J. Geophys. Res.

145

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Abstract. An extensive set of line-by-line plus doubling-adding reference computations for both clear and overcast skies has been utilized to develop, calibrate, and verify the accuracy of a new multiple-band solar parameterization, suitable for use in atmospheric general circulation models. In developing this parameterization the emphasis is placed on reproducing accurately the reference absorbed flux in clear and overcast atmospheres. In addition, a significantly improved representation of the reference stratospheric heating profile, in comparison with that derived from older, broadband solar parameterizations, has been attained primarily because of an improved parameterization of CO2 heating. The exponential-sum-fit technique is used to develop the parameterization of water vapor transmission in the main absorbing bands. An absorptivity approach is used to represent the heating contributions by CO2 and 02, and a spectral averaging of the continuum-like properties is used to represent the 03 heating. There are a total of two pseudomonochromatic intervals needed to do the radiative transfer problem in the vertically inhomogeneous atmosphere is 72. The delta-Eddington method is used to solve for the reflection and transmission of the homogeneous layers, while the "adding" method is used to combine the layers. The single-scattering properties of the homogeneous layers can account for all types of scattering and absorbing constituents (molecules, drops, ice particles, and aerosols), given their respective single-scattering properties and mass concentrations. With respect to the reference computational results the clear-sky heating rates are generally accurate to within 10%, and the atmospheric absorbed flux is accurate to within 2%. An analysis is made of the factors contributing to the error in the parameterized cloud absorption in the near infrared. Derivation of the representative drop coalbedo for a band using the mean reflection for an infinitely thick cloud (thick-averaging technique) generally results in a better agreement with the reference cloud absorbed flux than that derived using the mean drop coalbedo (thin-averaging technique), except for high, optically thin water clouds. Further, partitioning the 2500 < v < 8200 cm-•spectral region into several more bands than two (the minimum required) results in an improved representation of the cloud absorbed flux, with a modest increase in the shortwave radiation computational time. The cloud absorbed flux is accurate to within 10%, and the cloudy layer heating rates are accurate to within 15%, for water clouds, while larger errors can occur for ice clouds. The atmospheric absorbed, downward surface, and upward topof-the-atmosphere fluxes are generally accurate to within 10%. For overcast atmospheres, •zhere drops and gas (mainly water vapor) are both present, the formulation of an accurate solar parameterization, using the broadband concept, is much more difficult. This is especially the case when only one nearinfrared interval is utilized. The spectral absorp...

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“…is the depth of the scene point from the observer, β is called the scattering coefficient of the atmosphere [41], E ∞ is the brightness at the horizon, and ρ is a function of the scene point BRDF [36]. Under what weather conditions is the dichromatic model valid?…”

Section: Example Evaluation: Weather Analysismentioning

confidence: 99%

All the Images of an Outdoor Scene

Narasimhan

Wang

Nayar

2002

Lecture Notes in Computer Science

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Abstract. The appearance of an outdoor scene depends on a variety of factors such as viewing geometry, scene structure and reflectance (BRDF or BTF), illumination (sun, moon, stars, street lamps), atmospheric condition (clear air, fog, rain) and weathering (or aging) of materials. Over time, these factors change, altering the way a scene appears. A large set of images is required to study the entire variability in scene appearance. In this paper, we present a database of high quality registered and calibrated images of a fixed outdoor scene captured every hour for over 5 months. The dataset covers a wide range of daylight and night illumination conditions, weather conditions and seasons. We describe in detail the image acquisition and sensor calibration procedures. The images are tagged with a variety of ground truth data such as weather and illumination conditions and actual scene depths. This database has potential implications for vision, graphics, image processing and atmospheric sciences and can be a testbed for many algorithms. We describe an example application -image analysis in bad weather -and show how this method can be evaluated using the images in the database. The database is available online at http://www.cs.columbia.edu/CAVE/. The data collection is ongoing and we plan to acquire images for one year. Variability in Scene AppearanceThe appearance of a fixed scene depends on several factors -the viewing geometry, illumination geometry and spectrum, scene structure and reflectance (BRDF or BTF) and the medium (say, atmosphere) in which the scene is immersed. The estimation of one or more of these appearance parameters from one or more images of the scene has been an important part of research in computer vision. Several researchers have focused on solving this inverse problem under specific conditions of illumination (constant or smoothly varying), scene structure (no discontinuities), BRDF (lambertian) and transparent media (pure air). Images captured to evaluate their methods adhere to the specific conditions. While understanding each of these specific cases is important, modeling scene appearance in the most general setting is ultimately the goal of a vision system. To model, develop and evaluate such a general vision system, it is critical to collect a comprehensive set of images that describes the complete variability in the appearance of a scene. Several research groups have collected images of a scene (for example, faces, textures, objects) under varying lighting conditions

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Optics of the Atmosphere: Scattering by Molecules and Particles

Cited by 388 publications

References 0 publications

A permanent Raman lidar station in the Amazon: description, characterization, and first results

A permanent Raman lidar station in the Amazon: description, characterization, and first results

A new multiple‐band solar radiative parameterization for general circulation models

All the Images of an Outdoor Scene

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