Towards a better representation of the solar cycle in general circulation models K. M. Nissen1, K. Matthes1, U. Langematz1, and B. Mayer2 1Institut für Meteorologie, Freie Universität Berlin, Carl-Heinrich-Becker-Weg 6–10, 12165 Berlin, Germany 2Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt, Oberpfaffenhofen, Germany
Abstract. We introduce the improved Freie Universität Berlin (FUB)
high-resolution radiation scheme FUBRad and compare it to the
4-band standard ECHAM5 SW radiation scheme of Fouquart and Bonnel
(FB). Both schemes are validated against the detailed radiative
transfer model libRadtran. FUBRad produces realistic heating rate
variations during the solar cycle. The SW heating rate response
with the FB scheme is about 20 times smaller than with FUBRad and
cannot produce the observed temperature signal. A reduction of the
spectral resolution to 6 bands for solar irradiance and ozone
absorption cross sections leads to a degradation (reduction) of
the solar SW heating rate signal by about 20%.
The simulated temperature response agrees qualitatively well with
observations in the summer upper stratosphere and mesosphere where
irradiance variations dominate the signal.
Comparison of the total short-wave heating rates under solar minimum
conditions shows good agreement between FUBRad, FB and
libRadtran up to the middle mesosphere (60–70 km) indicating that
both parameterizations are well suited for climate integrations
that do not take solar variability into account.
The FUBRad scheme has been implemented as a sub-submodel of the
Modular Earth Submodel System (MESSy).
Citation: Nissen, K. M., Matthes, K., Langematz, U., and Mayer, B.: Towards a better representation of the solar cycle in general circulation models, Atmos. Chem. Phys., 7, 5391-5400, doi:10.5194/acp-7-5391-2007, 2007.