Modifications of discrete ordinate method for computations with high scattering anisotropy: Comparative analysis

Korkin, Sergey; Lyapustin, A.; Розанов, В. В.

doi:10.1016/j.jqsrt.2012.07.022

Cited by 9 publications

(6 citation statements)

References 18 publications

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“…In order to speed-up computations, modern RT codes truncate the scattering function and apply single (or sometimes double) scattering correction 29 as post processing. Our experience 30 showed that such an approach gives huge errors in the aureole area. Because we are planning to use the code for observations from ground, we refrained from using any truncation technique 31 until further detailed research.…”

Section: Features Of the Codementioning

confidence: 95%

A new code SORD for simulation of polarized light scattering in the Earth atmosphere

Korkin¹,

Lyapustin²,

Sinyuk

et al. 2016

SPIE Proceedings

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We report a new publicly available radiative transfer (RT) code for numerical simulation of polarized light scattering in plane-parallel atmosphere of the Earth. Using 44 benchmark tests, we prove high accuracy of the new RT code, SORD (Successive ORDers of scattering 1, 2 ). We describe capabilities of SORD and show run time for each test on two different machines. At present, SORD is supposed to work as part of the Aerosol Robotic NETwork 3 (AERONET) inversion algorithm. For natural integration with the AERONET software, SORD

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Section: Features Of the Codementioning

confidence: 95%

A new code SORD for simulation of polarized light scattering in the Earth atmosphere

Korkin¹,

Lyapustin²,

Sinyuk

et al. 2016

SPIE Proceedings

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“…The code was extensively tested using 52 benchmark scenarios providing an accuracy of ∼ 0.1 % for both intensity and polarization calculations. Unlike V2 RTC, whose speed was boosted by employing the truncation approximation of Nakajima and Tanaka (1988), no such approximation is used by SORD due to the potential problems it can cause in the forward scattering direction (e.g., Korkin et al, 2012). The NASA Center for Climate Simulation (NCCS) at the NASA Goddard Space Flight Center (GSFC) Discover cluster is utilized to overcome the significant increase in computational resources required for the application of SORD in AERONET retrievals (https://www.nccs.nasa.gov/ systems/discover, last access: 8 June 2020).…”

Section: Version 3 Retrieval Algorithm Descriptionmentioning

confidence: 99%

The AERONET Version 3 aerosol retrieval algorithm, associated uncertainties and comparisons to Version 2

et al. 2020

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Abstract. The Aerosol Robotic Network (AERONET) Version 3 (V3) aerosol retrieval algorithm is described, which is based on the Version 2 (V2) algorithm with numerous updates. Comparisons of V3 aerosol retrievals to those of V2 are presented, along with a new approach to estimate uncertainties in many of the retrieved aerosol parameters. Changes in the V3 aerosol retrieval algorithm include (1) a new polarized radiative transfer code (RTC), which replaced the scalar RTC of V2, (2) detailed characterization of gas absorption by adding NO2 and H2O to specify total gas absorption in the atmospheric column, specification of vertical profiles of all the atmospheric species, (3) new bidirectional reflectance distribution function (BRDF) parameters for land sites adopted from the MODIS BRDF/Albedo product, (4) a new version of the extraterrestrial solar flux spectrum, and (5) a new temperature correction procedure of both direct Sun and sky radiance measurements. The potential effect of each change in V3 on single scattering albedo (SSA) retrievals was analyzed. The operational almucantar retrievals of V2 versus V3 were compared for four AERONET sites: GSFC, Mezaira, Mongu, and Kanpur. Analysis showed very good agreement in retrieved parameters of the size distributions. Comparisons of SSA retrievals for dust aerosols (Mezaira) showed a good agreement in 440 nm SSA, while for longer wavelengths V3 SSAs are systematically higher than those of V2, with the largest mean difference at 675 nm due to cumulative effects of both extraterrestrial solar flux and BRDF changes. For non-dust aerosols, the largest SSA deviation is at 675 nm due to differences in extraterrestrial solar flux spectrums used in each version. Further, the SSA 675 nm mean differences are very different for weakly (GSFC) and strongly (Mongu) absorbing aerosols, which is explained by the lower sensitivity to a bias in aerosol scattering optical depth by less absorbing aerosols. A new hybrid (HYB) sky radiance measurement scan is introduced and discussed. The HYB combines features of scans in two different planes to maximize the range of scattering angles and achieve scan symmetry, thereby allowing for cloud screening and spatial averaging, which is an advantage over the principal plane scan that lacks robust symmetry. We show that due to an extended range of scattering angles, HYB SSA retrievals for dust aerosols exhibit smaller variability with solar zenith angles (SZAs) than those of almucantar (ALM), which allows extension of HYB SSA retrievals to SZAs less than 50∘ to as small as 25∘. The comparison of SSA retrievals from closely time-matched HYB and ALM scans in the 50 to 75∘ SZA range showed good agreement with the differences below ∼0.005. We also present an approach to estimate retrieval uncertainties which utilizes the variability in retrieved parameters generated by perturbing both measurements and auxiliary input parameters as a proxy for retrieval uncertainty. The perturbations in measurements and auxiliary inputs are assumed as estimated biases in aerosol optical depth (AOD), radiometric calibration of sky radiances combined with solar spectral irradiance, and surface reflectance. For each set of Level 2 Sun/sky radiometer observations, 27 inputs corresponding to 27 combinations of biases were produced and separately inverted to generate the following statistics of the inversion results: average, standard deviation, minimum and maximum values. From these statistics, standard deviation (labeled U27) is used as a proxy for estimated uncertainty, and a lookup table (LUT) approach was implemented to reduce the computational time. The U27 climatological LUT was generated from the entire AERONET almucantar (1993–2018) and hybrid (2014–2018) scan databases by binning U27s in AOD (440 nm), Angström exponent (AE, 440–870 nm), and SSA (440, 675, 870, 1020 nm). Using this LUT approach, the uncertainty estimates U27 for each individual V3 Level 2 retrieval can be obtained by interpolation using the corresponding measured and inverted combination of AOD, AE, and SSA.

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“…Single scattering path radiance and reflection of the direct solar beam from the surface are computed analytically. In order to avoid errors in the aureole (Korkin et al, 2012), none of the phase function truncation techniques (Rozanov and Lyapustin, 2010) has been implemented so far. IPOL ignores atmospheric curvature, 3D effects, and thermal emission.…”

Section: Ipolmentioning

confidence: 99%

IPRT polarized radiative transfer model intercomparison project – Phase A

Emde¹,

Barlakas

Cornet

et al. 2015

Journal of Quantitative Spectroscopy and Radiative Transfer

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a b s t r a c tThe polarization state of electromagnetic radiation scattered by atmospheric particles such as aerosols, cloud droplets, or ice crystals contains much more information about the optical and microphysical properties than the total intensity alone. For this reason an increasing number of polarimetric observations are performed from space, from the ground and from aircraft. Polarized radiative transfer models are required to interpret and analyse these measurements and to develop retrieval algorithms exploiting polarimetric observations. In the last years a large number of new codes have been developed, mostly for specific applications. Benchmark results are available for specific cases, but not for more sophisticated scenarios including polarized surface reflection and multi-layer atmospheres. The International Polarized Radiative Transfer (IPRT) working group of the International Radiation Commission (IRC) has initiated a model intercomparison project in order to fill this gap. This paper presents the results of the first phase A of the IPRT project which includes ten test cases, from simple setups with only one layer and Rayleigh scattering to rather sophisticated setups with a cloud embedded in a standard atmosphere above an ocean surface. All scenarios in the first phase A of the intercomparison project are for a one-dimensional plane-parallel model geometry. The commonly established benchmark results are available at the IPRT website

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Modifications of discrete ordinate method for computations with high scattering anisotropy: Comparative analysis

Abstract: A numerical accuracy analysis of the radiative transfer equation (

Cited by 9 publications

References 18 publications

A new code SORD for simulation of polarized light scattering in the Earth atmosphere

A new code SORD for simulation of polarized light scattering in the Earth atmosphere

The AERONET Version 3 aerosol retrieval algorithm, associated uncertainties and comparisons to Version 2

IPRT polarized radiative transfer model intercomparison project – Phase A

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