SCIATRAN 2.0 – A new radiative transfer model for geophysical applications in the 175–2400 nm spectral region

doi:10.1016/j.asr.2005.03.012

Advances in Space Research

Volume 36, Issue 5, 2005, Pages 1015-1019

https://doi.org/10.1016/j.asr.2005.03.012 Get rights and content

Abstract

A successor version of the SCIATRAN radiative transfer model (RTM) has been developed to perform radiative transfer modeling in any observation geometry appropriate to measurements of the scattered solar radiation in the Earth’s atmosphere. The model is designed to be used as a forward model in the retrieval of atmospheric constituents from measurements of scattered solar light by satellite, ground-based, or airborne instruments in UV–Vis–NIR spectral region. Furthermore, it can be used to calculate air mass factors or fluxes. The new generation of the SCIATRAN model comprises all features of the latest SCIATRAN 1.2 RTM supporting additionally radiative transfer calculations in a spherical atmosphere. The program is written in FORTRAN 95 and suitable for parallel execution using the OpenMP standard. The wavelength range covered by the radiative transfer model is extended to 175–2380 nm including Schuman-Runge and Herzberg absorption bands of oxygen. The SCIATRAN 2.0 model exhibits the following new capabilities: (i) modeling of the scattered solar radiation in limb viewing geometry as well as any kind of measurements of the scattered radiation within the atmosphere, (ii) corresponding quasi-analytical calculation of weighting functions of atmospheric parameters, (iii) airmass factor calculations for ground-based, space and airborne measurements including off-axis geometry, (v) accounting for photochemically active species, i.e., radiative transfer calculations can be performed using solar zenith angle dependent vertical distributions of atmospheric species, (iv) height resolved radiation fluxes, including actinic fluxes for photolysis rate calculations, (vi) inelastic rotational Raman scattering in any supported viewing geometry, (vii) new effective approximations for radiative transfer modeling in presence of clouds. The SCIATRAN model is freely available via the world wide web for non-commercial scientific applications.

Introduction

The SCIATRAN radiative transfer models (RTMs) are next generation RTMs based on the well-known GOMETRAN (Rozanov et al., 1997) model which was originally developed to simulate solar radiation backscattered from the atmosphere and reflected from the Earth’s surface in the spectral range 240–800 nm as measured by the Global Ozone Monitoring Experiment (GOME) in nadir viewing geometry. A successor RTM called SCIATRAN (Rozanov et al., 2002) was extended to cover the spectral range 240–2380 nm comprising the eight spectral channels of the SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) instrument. SCIATRAN versions up to 1.2 utilize the pseudo-spherical approach, including refraction, appropriate for solar zenith angles up to about 92° and near-nadir viewing angles.

A new generation of the SCIATRAN model comprises all features of the latest SCIATRAN 1.2 RTM supporting additionally radiative transfer calculations in a spherical atmosphere (Rozanov et al., 2001). The program is written in FORTRAN 95 and suitable for parallel execution using the OpenMP standard (OpenMP, 1997–2004). The wavelength range covered by the radiative transfer model is extended to 175–2380 nm including Schuman-Runge and Herzberg absorption bands of oxygen. The SCIATRAN 2.0 model exhibits many new capabilities making it valuable for a wide range of scientific applications.

Section snippets

Main features

Due to a newly implemented spherical mode and an improved plane-parallel mode, the SCIATRAN radiative transfer model becomes suitable to solve almost any scientific task associated to measurements of the scattered solar radiation in the Earth’s atmosphere in the ultraviolet, visible, and near-infrared (UV–Vis–NIR) spectral regions. The radiative transfer modeling can be performed at any viewing geometry common for measurements of the scattered solar radiation within or above the atmosphere,

Conclusion

The latest version of the radiative transfer model SCIATRAN has been discussed which is suitable to solve almost any scientific task related to measurements of the scattered solar radiation in the Earth’s atmosphere by means of satellite, ground-based, or air-borne instruments in UV–Vis–NIR spectral region. The program is freely available for non-commercial scientific applications (http://www.iup.physik.uni-bremen.de/sciatran). The work on the polarization is currently in progress.

Acknowledgments

This work has been funded in parts by the German Ministry of Education and Research BMBF (Grant 07UFE12/8), the German Aerospace Centre DLR (Grant 50EE0027), and the German Research Foundation DFG (Project BU 688/8-1).

Authors thank Dr. P. Wang (Institute of Environmental Physics, University of Bremen, Germany), for her efforts on the OClO slant column modeling. We also thank B. Mayer and K. Wapler (German Aerospace Center (DLR), Institute of Atmospheric Physics, Oberpfaffenhofen, Germany) for

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Citation Excerpt :
Consequently, the requirement of developing a different AOD retrieval algorithm for land arises; most of the operational satellite products like MODIS, SeaWIFS and VIIRS employ different algorithms for retrieval over ocean and land. Several of these sensor retrievals utilize RTMs that are based on the complex calculations and/or look-up table approach (Rozanov et al., 2005) (Vermote et al., 1997) (Berk et al., 1987) (Kokhanovsky and de Leeuw 2009). For passive sensors, one of the commonly used approaches is the Dark Target (DT) algorithm which is restricted to retrieval over dark targets like water and vegetated surfaces (ATBD - Data Usage Dark Target. (n.d.)).
The decoupling of aerosol signals from the at-sensor reflectance measured through a space-borne sensor is a complex task due to the involved coupling mechanism of the interaction of light with the Earth's surface and the atmosphere. Specifically, the retrieval becomes more challenging over the land surface due to appreciable reflectance from the target. This paper presents a simplistic physics-based approach to retrieve Aerosol Optical Depth (AOD) (at a spatial resolution of 0.01°) over the land surface from the top-of-atmosphere (TOA) signals measured from an Indian space-borne sensor, Ocean Color Monitor-2 (onboard OCEANSAT-2 satellite). The estimated AOD from OCM-2 has been compared with that from Moderate Resolution Spectroradiometer (MODIS) onboard AQUA satellite (Collection 6.1 Deep Blue/Dark Target product). The comparison is illustrated for two different conditions prevalent over the Indian region, i.e., smoke-dominated (post-monsoonal) and dust-laden (pre-monsoonal) periods. A case study is also illustrated for the pre- and post-COVID-19 lockdown time period for two different zones of the Indian region. The validation (comparison) of OCM-2 AOD is performed with respect to the data from AERONET stations (MODIS), and we found a correlation coefficient (R²) of 0.84 (0.83) with root mean square error (RMSE) of 0.14 (0.20). Also, ∼87% (70%) of the retrieved OCM-2 (MODIS) AOD values were observed within the expected error (EE) envelope. The sensitivity of the retrieval algorithm with respect to the input parameters is also presented.

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SCIATRAN 2.0 – A new radiative transfer model for geophysical applications in the 175–2400 nm spectral region

Abstract

Introduction

Section snippets

Main features

Conclusion

Acknowledgments

J. Quant. Spectrosc. Radiat. Transfer

Adv. Space Res.

J. Quant. Spectrosc. Radiat. Transfer

Adv. Space. Res.

J. Quant. Spectrosc. Radiat. Transfer

J. Quant. Spectrosc. Radiat. Transfer

Light scattering media optics