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

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
The influence of the 11 yr solar cycle on the interannual-centennial climate variability.
Mbiye kalumbu bienvenu
university of kinshasa
The monthly sunspot number (SSN) for January 1749-August 2004, the global sea-surface
temperature (gmSST) and the regional SSTs in the northern N. Pacific (npSST) and the
Nino3.4 (ninoSST) areas for the winters of 1870-2004 are analyzed by a wavelet transform to
show their multi-scale nature. On the interdecadal timescales, both gmSST and npSST have
similar variation tendencies with that of the intensity and cycle-length of the 11 yr SSN, with
slight phase differences. The npSST and ninoSST are often out of phase on the decadalinterdecadal
timescales. The ninoSST is predominated by the interannual timescales peaking
around 3.8yr. Moreover, the ninoSST exhibits an apparent 80-90 yr signal that is almost out
of phase with that observed in SSN. Numerical experiments using a simple nonlinear system
illustrate that the intensity of the seasonal forcing, modulated by the 11 yr solar activity, is
likely an important factor causing different dominant timescales in regional SSTs. Even a
small change in the solar constant by 0.04% on the 11 yr timescale may result in a regime
change in the response (e.g. SST) with various dominant timescales, including the 77 and 88
yr signals that are similar to those of the Gleissberg cycle in observed SSN. The results show
that part of the energy of the internal variability of the system is transferred to the forced
variability that may have richer timescales than those in the forcing itself due to nonlinear
resonance. This suggests that observed interannual-centennial climate signals are not purely
internal, but also external because of the existence of the 11 yr solar activity cycle, which has
changed the solar constant in the past and will continue doing so in the future. It also suggests
that if the solar Gleissberg cycle is included in the forcing term, the 77 and 88 yr interdecadal
signals and their subharmonics on centennial timescales may be more significant than what is
shown here, which might have some implication to global warming research.