This project focuses on the extension and evaluation of the Radiative Transfer Model (RTM) SCIATRAN which is developed at the Institute of Environmental Physics at the University of Bremen (IUP), University Bremen, by Dr.  Vladimir Rozanov. The model was originally developed to analyse measurements performed by the hyperspectral instrument SCIAMACHY (SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY) operating in the spectral range from 240 to 2400 nm onboard ENVISAT (Gottwald and Bovensmann, 2011). SCIATRAN is a comprehensive software package (e.g., Rozanov et al. 2005) originally for the modeling of radiative transfer processes in the terrestrial atmosphere in the spectral range from ultraviolet to the thermal infrared (0.18-40 µm) including multiple scattering processes, polarization, and thermal emission.  Recently the model is extended for a coupled atmosphere-ocean system to include calculations of the light field inside the ocean body with constituents (Rozanov et al. 2014).  The software package SCIATRAN was extended, to account for the radiative transfer within the water and the interaction of radiative processes in the atmosphere and ocean.  All optical relevant parameters can be considered (absorption, elastic and inelastic scattering).  Three different forms of inelastic scattering as transpectral processes in oceanic waters are included in the model: Vibrational-Raman-Scattering, fluorescence of chl-a and CDOM (see respectively recent publications: Dinter et al. 2015, Wolanin et al. 2015a, Wolanin et al. 2015b). 

In comparisons of SCIATRAN calculations with in-situ radiation measurements above and below the water surface, the model demonstrates the ability to reproduce realistic light field conditions in complex oceanic systems and shows quite good agreement (e.g., Soppa et al. 2019).  Further an extensive sensitivity study with SCIATRAN shows the applicability and error ranges of the PhytoDOAS method. In order to validate this extension of the model, several comparisons with in-situ and satellite observations and simulations used for testing other radiative transfer models, including comparisons to HydroLight (Mobley and Sundman, 2008), a widely used RTM within the ocean optics community have been performed (Blum et al., 2012). Currently, as one important step to show the applicability of SCIATRAN model to resolve ocean optics,  the extended SCIATRAN RTM for evaluation and optimisation of the PhytoDOAS phytoplankton group retrieval (see projects SynSenPFT, S5POC, PHYSYN) and other upcoming hyperspectral ocean colour products (light availability in Dinter et al. 2015, difusse attenuation in Oelker et al. 2019, CDOM fluorescence in Wolanin et al. 2015). In co-operation with the DOAS group of the IUP, it is planned that the extended SCIATRAN RTM will also be used to optimize atmospheric trace gas retrieval using UV-VIS satellite data over the ocean.

References:

See group's peer-reviewed publications for: Blum et al. 2012, Dinter et al. 2015, Wolanin et al. 2015a, Wolanin et al. 2015b, Oelker et al. 2019, Soppa et al. 2019

See group's books for: Gottwald and Bovensmann 2011

Rozanov VV, Rozanov A, Kokhanovsky A, Burrows JP (2014) Radiative transfer through atmosphere and ocean: Software package SCIATRAN. J. Quant. Spectrosc. Rad. Transfer 133: 13-71. doi: 10.1016/j.jqsrt.2013.7.004

Rozanov A, Rozanov VV, Buchwitz M, Kokhanovsky A, Burrows JP (2005) Sciatran - a new radiative transfer model for geophysical applications in the 240-2400 nm spectral region: the pseudo-spherical version. Adv. Space Res. 36, 1015-1019