Towards a better representation of the solar cycle in general circulation models

[摘要] We introduce the improved Freie Universität Berlin (FUB)high-resolution radiation scheme FUBRad and compare it to the4-band standard ECHAM5 SW radiation scheme of Fouquart and Bonnel(FB). Both schemes are validated against the detailed radiativetransfer model libRadtran. FUBRad produces realistic heating ratevariations during the solar cycle. The SW heating rate responsewith the FB scheme is about 20 times smaller than with FUBRad andcannot produce the observed temperature signal. A reduction of thespectral resolution to 6 bands for solar irradiance and ozoneabsorption cross sections leads to a degradation (reduction) ofthe solar SW heating rate signal by about 20%.

The simulated temperature response agrees qualitatively well withobservations in the summer upper stratosphere and mesosphere whereirradiance variations dominate the signal.

Comparison of the total short-wave heating rates under solar minimumconditions shows good agreement between FUBRad, FB andlibRadtran up to the middle mesosphere (60–70 km) indicating thatboth parameterizations are well suited for climate integrationsthat do not take solar variability into account.

The FUBRad scheme has been implemented as a sub-submodel of theModular Earth Submodel System (MESSy).

[学科分类] 大气科学