scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
The 11-years solar cycle in transient WACCM-3 simulations
Chiodo Gabriel 1 , García-Herrera Ricardo 1 , Calvo Natalia 2
1 Universidad Complutense de Madrid, 2 National Center for Atmospheric Research
The whole atmospheric response to the 11-years Schwabe cycle was analysed in an ensemble
of four WACCM-3.5 simulations covering 45 years (1965-2005, neglecting the initial five
years for model spin-up). These experiments were carried out within the CCMVal-2 initiative
to reproduce the past. The simulations were driven with the following forcings: (1) a timevarying
solar cycle, (2) nudged QBO, (3) observed SSTs, (4) anthropogenic carbon and ODS
emissions. All ensemble members show a statistically significant annual mean warming
throughout the middle and upper tropical stratosphere, with a radiatively-driven maximum in
the upper stratosphere, a relative minimum in the middle stratosphere and a secondary
dynamically-driven strong maximum in the tropical lower stratospheric temperature and
ozone response. The nudged QBO and the observed SSTs play an important role in
amplifying the solar signal in the lower stratosphere. Moreover, a downward propagation of
zonal wind anomalies from the stratosphere to the troposphere in the extra-tropics is found
during the Northern Hemispheric winter, which appears to be a robust feature of the model
simulations. On the other hand, the QBO modulation of the extra-tropical solar signal in late
NH-winter (i), and the solar-cycle modulation of the Holton-Tan relationship (ii) are only
evident in two of the four ensemble members, thus indicating that the two-way QBO-solar
cycle dynamical interaction is not significant. Some features of these results are shown to be
closer to observations than in previous WACCM modeling studies, thus certifying an
improvement in the modeled whole atmospheric solar response in WACCM-3.5, which is
brought by the implementation of a new GW-source parameterization.