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

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Comparison of the 11-year solar signal in coordinated SPARC/SOLARIS experiments
using filtered forcings
Kubin Anne 1 , Matthes Katja 2 , Shibata Kiyotaka 3 , Kodera Kunihiko 4 , Langematz Ulrike 1
1 Institut fuer Meteorologie, Freie Universitaet Berlin, Germany, 2 GFZ Potsdam, Germany, 3 MRI,
Tsukuba, Japan, 4 Nagoya University, Japan
The origin of the observed maximum in temperature and ozone response to the solar cycle in
the tropical lower stratosphere is currently under discussion. It is unclear whether it is related
to non-linear interactions between the solar cycle, the QBO and ENSO or due to aliasing
effects. To further investigate this, we present results from coordinated chemistry-climate
model (CCM) simulations, performed with the ECHAM5/MESSy (EMAC-FUB), NCAR's
Whole Atmosphere Community Climate model (WACCM3) and the MRI models within the
SPARC SOLARIS initiative. The CCM simulations are similar to the reference simulations
for the past within the SPARC CCMVal initiative for the period 1960 to 2005 with observed
greenhouse gases, ozone depleting substances, and daily varying spectrally resolved solar
irradiances but use prescribed filtered QBO and filtered SST and sea ice forcings instead. The
SSTs and the sea ice time series have been filtered to remove QBO (2-3 years) and solar cycle
(> 10 years) signals, while the observed equatorial mean zonal mean wind data have been
filtered to retain QBO signals only (9-48 months) and exclude ENSO and solar cycle signals
explicitly. All three CCMs use the same filtered SST and sea ice forcings. WACCM3 and
EMAC-FUB use the filtered QBO forcing to nudge a QBO, whereas the MRI model produces
a self-consistent QBO and does not use the filtered QBO forcing data.
The results are analysed by means of a correlation and state-of-the-art multiple linear
regression model analysis. Special emphasis is placed on the response of ozone volume
mixing ratio and related radiative heating, temperature and zonal wind to the 11-year solar
cycle. The results are compared to CCMVal reference simulations with unfiltered forcings for
the same time period.