Multiangle Lidar Performance in the Presence of Horizontal Inhomogeneities in Atmospheric Extinction and Scattering

Gutkowicz–Krusin, Dina

doi:10.21236/ada252882

Cited by 14 publications

(15 citation statements)

References 2 publications

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“…Rather than performing the principal volume integration, different polarizability models based on physical arguments have been proposed [39,[64][65][66][67][68][69]. 14 The impact of these approximations on the accuracy of the T-DDA depends on the specific parameters of the problem.…”

Section: Discretization Of the Objects Into Cubical Subvolumes The Ementioning

confidence: 99%

Convergence analysis of the thermal discrete dipole approximation

et al. 2015

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The thermal discrete dipole approximation (T-DDA) is a numerical approach for modeling nearfield radiative heat transfer in complex three-dimensional geometries. In this work, the convergence of the T-DDA is investigated by comparison against the exact results for two spheres separated by a vacuum gap. The error associated with the T-DDA is reported for various sphere sizes, refractive indices and vacuum gap thicknesses. The results reveal that for a fixed number of subvolumes, the accuracy of the T-DDA degrades as the refractive index and the sphere diameter to gap ratio increase. A converging trend is observed as the number of subvolumes increases. The large computational requirements associated with increasing the number of subvolumes, and the shape error induced by large sphere diameter to gap ratios, are mitigated by using a nonuniform discretization scheme. Nonuniform discretization is shown to significantly accelerate the convergence of the T-DDA, and is thus recommended for near-field thermal radiation simulations. Errors less than 5% are obtained in 74% of the cases studied by using up to 82712 subvolumes. Additionally, the convergence analysis demonstrates that the T- † Corresponding authors. Tel.: +1 801 581 5721, Fax: +1 801 585 9825 E-mail addresses: mfrancoeur@mech.utah.edu (M. Francoeur), sheila.edalatpour@utah.edu (S. Edalatpour) 2 DDA is very accurate when dealing with surface polariton resonant modes dominating radiative heat transfer in the near field.

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Section: Discretization Of the Objects Into Cubical Subvolumes The Ementioning

confidence: 99%

Convergence analysis of the thermal discrete dipole approximation

et al. 2015

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“…9 Three methods have been demonstrated to provide independent aerosol extinction measurements: highspectral-resolution lidar, 10 Raman lidar 7,8 and multiple zenith-angle measurements. [11][12][13] The Raman and the high-spectral-resolution techniques both rely on the detection of a pure molecular backscatter signal, but the latter requires a much higher technical effort to suppress aerosol backscattering. For reasons of technical practicability, the preferred method within the EARLINET is a combination of Raman and elastic scattering at one emission wavelength near 355 nm.…”

Section: Introductionmentioning

confidence: 99%

Aerosol lidar intercomparison in the framework of the EARLINET project 3 Raman lidar algorithm for aerosol extinction, backscatter, and lidar ratio

Pappalardo¹,

Amodeo²,

Pandolfi³

et al. 2004

Appl. Opt.

256

229

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An intercomparison of the algorithms used to retrieve aerosol extinction and backscatter starting from Raman lidar signals has been performed by 11 groups of lidar scientists involved in the European Aerosol Research Lidar Network ͑EARLINET͒. This intercomparison is part of an extended quality assurance program performed on aerosol lidars in the EARLINET. Lidar instruments and aerosol backscatter algorithms were tested separately. The Raman lidar algorithms were tested by use of synthetic lidar data, simulated at 355, 532, 386, and 607 nm, with realistic experimental and atmospheric conditions taken into account. The intercomparison demonstrates that the data-handling procedures used by all the lidar groups provide satisfactory results. Extinction profiles show mean deviations from the correct solution within 10% in the planetary boundary layer ͑PBL͒, and backscatter profiles, retrieved by use of algorithms based on the combined Raman elastic-backscatter lidar technique, show mean deviations from solutions within 20% up to 2 km. The intercomparison was also carried out for the lidar ratio and produced profiles that show a mean deviation from the solution within 20% in the PBL. The mean value of this parameter was also calculated within a lofted aerosol layer at higher altitudes that is representative of typical layers related to special events such as Saharan dust outbreaks, forest fires, and volcanic eruptions. Here deviations were within 15%.

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“…The scanning lidar technique measures the backscatter signal under different angles. Here the disadvantage lies in the necessary assumption of horizontal homogeneity (Gutkowicz-Krusin, 1993). The Raman method that is used here uses a second, independent molecular backscatter signal, as for example the Raman-shifted nitrogen backscatter signal.…”

Section: Introductionmentioning

confidence: 99%

Three years of routine Raman lidar measurements of tropospheric aerosols: Backscattering, extinction, and residual layer height

Schneider

Eixmann

2002

Atmos. Chem. Phys.

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Abstract.We have performed a three-year series of routine lidar measurements at preselected times. The measurements were performed between 1 December 1997, and 30 November 2000, at Kühlungsborn, Germany (54 • 07 N, 11 • 46 E). Using a Rayleigh/Mie/Raman lidar system, we measured the aerosol backscatter coefficients at three wavelengths and the extinction coefficient at one wavelength. The present data analysis focuses on after-sunset Raman measurements obtained on cloud-free days. Aerosol backscatter profiles are available for altitudes above 100 m, while the majority of the extinction measurements has been restricted to heights above the residual layer. The residual layer shows an annual cycle with its maximum height in summer (2000 m) and minimum height in winter (850 m). The backscatter coefficients in the residual layer were found to be about 10 times higher than above. The mean aerosol optical depth above the residual layer and below 5 km is 0.3(±1.0) × 10 −2 in summer, and 1.5(±1.0) × 10 −2 in winter, which almost is negligible compared to values measured in during daytime in the planetary boundary layer. A cluster analysis of the backward trajectories yielded two major directions of air mass origin above the residual layer and 4 major directions inside. A marked difference between the aerosol properties dependent on the air mass origin could be found for air masses originating from the west and travelling at high wind speeds. Comparing the measured spectral dependence of the backscatter coefficients with data from the Global Aerosol Data Set, we found a general agreement, but only a few conclusions with respect to the aerosol type could be drawn due to the high variability of the measured backscatter coefficients.

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Multiangle Lidar Performance in the Presence of Horizontal Inhomogeneities in Atmospheric Extinction and Scattering

Cited by 14 publications

References 2 publications

Convergence analysis of the thermal discrete dipole approximation

Convergence analysis of the thermal discrete dipole approximation

Aerosol lidar intercomparison in the framework of the EARLINET project 3 Raman lidar algorithm for aerosol extinction, backscatter, and lidar ratio

Three years of routine Raman lidar measurements of tropospheric aerosols: Backscattering, extinction, and residual layer height

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