Simulation of solar radiation during a total eclipse: a challenge for radiative transfer C. Emde and B. Mayer Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Oberpfaffenhofen, 82234 Wessling, Germany
Abstract. A solar eclipse is a rare but spectacular natural phenomenon and
furthermore it is a challenge for radiative transfer modelling.
Whereas a simple one-dimensional radiative transfer model with
reduced solar irradiance at the top of the atmosphere can be used to
calculate the brightness during partial eclipses a much more
sophisticated model is required to calculate the brightness
(i.e. the diffuse radiation) during the total eclipse. The reason is
that radiation reaching a detector in the shadow gets there
exclusively by horizontal transport of photons in a spherical shell
atmosphere, which requires a three-dimensional radiative transfer
model. In this study the first fully three-dimensional simulations
for a solar eclipse are presented exemplified by the solar eclipse
at 29 March 2006. Using a backward Monte Carlo model we calculated
the diffuse radiation in the umbra and simulated the changing
colours of the sky. Radiance and irradiance are decreased by 3 to 4
orders of magnitude, depending on wavelength. We found that aerosol
has a comparatively small impact on the radiation in the umbra. We
also estimated the contribution of the solar corona to the radiation
under the umbra and found that it is negligible compared to the
diffuse solar radiation in the wavelength region from 310 to 500 nm.
Citation: Emde, C. and Mayer, B.: Simulation of solar radiation during a total eclipse: a challenge for radiative transfer, Atmos. Chem. Phys., 7, 2259-2270, doi:10.5194/acp-7-2259-2007, 2007.