Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 15, 7449-7456, 2015
http://www.atmos-chem-phys.net/15/7449/2015/
doi:10.5194/acp-15-7449-2015
© Author(s) 2015. This work is distributed
under the Creative Commons Attribution 3.0 License.
Technical note
09 Jul 2015
Technical Note: A novel parameterization of the transmissivity due to ozone absorption in the k-distribution method and correlated-k approximation of Kato et al. (1999) over the UV band
W. Wandji Nyamsi1, A. Arola2, P. Blanc1, A. V. Lindfors2, V. Cesnulyte2,3, M. R. A. Pitkänen2,3, and L. Wald1 1MINES ParisTech, PSL Research University, O.I.E., Centre Observation, Impacts, Energy, Sophia Antipolis, France
2Finnish Meteorological Institute, Kuopio, Finland
3Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
Abstract. The k-distribution method and the correlated-k approximation of Kato et al. (1999) is a computationally efficient approach originally designed for calculations of the broadband solar radiation at ground level by dividing the solar spectrum in 32 specific spectral bands from 240 to 4606 nm. Compared to a spectrally resolved computation, its performance in the UV band appears to be inaccurate, especially in the spectral intervals #3 [283, 307] nm and #4 [307, 328] nm because of inaccuracy in modeling the transmissivity due to ozone absorption. Numerical simulations presented in this paper indicate that a single effective ozone cross section is insufficient to accurately represent the transmissivity over each spectral interval. A novel parameterization of the transmissivity using more quadrature points yields maximum errors of respectively 0.0006 and 0.0143 for intervals #3 and #4. How to practically implement this new parameterization in a radiative transfer model is discussed for the case of libRadtran (library for radiative transfer). The new parameterization considerably improves the accuracy of the retrieval of irradiances in UV bands.

Citation: Wandji Nyamsi, W., Arola, A., Blanc, P., Lindfors, A. V., Cesnulyte, V., Pitkänen, M. R. A., and Wald, L.: Technical Note: A novel parameterization of the transmissivity due to ozone absorption in the k-distribution method and correlated-k approximation of Kato et al. (1999) over the UV band, Atmos. Chem. Phys., 15, 7449-7456, doi:10.5194/acp-15-7449-2015, 2015.
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Short summary
A novel model of the absorption of radiation by ozone in the UV bands [283, 307]nm and [307, 328]nm yields improvements in the modeling of the transmissivity in these bands. This model is faster than detailed spectral calculations and is as accurate with maximum errors of respectively 0.0006 and 0.0143. How to practically implement this new parameterization in a radiative transfer model is discussed for the case of libRadtran.
A novel model of the absorption of radiation by ozone in the UV bands [283, 307]nm and [307,...
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