Climate responses and their hemispheric differences under an extreme
quiet sun scenario
Abstract
Fundamental understanding of the climate responses to solar variability
is obscured by the large and complex climate variability. This
long-standing issue is addressed here by examining climate responses
under an extreme quiet sun (EQS) scenario, obtained by making the sun
void of all magnetic fields. It is used to drive a coupled climate model
with whole atmosphere and ocean components. The simulations reveal
robust responses, and elucidate aspects of the responses to changes of
troposphere/surface forcing and stratospheric forcing that are similar
and those that are different. Planetary waves (PWs) play a key role in
both regional climate and the mean circulation changes. Intermediate
scale stationary waves and regional climate respond to solar forcing
changes in the troposphere and stratosphere in a similar way, due to
similar subtropical wind changes in the upper troposphere. The patterns
of these changes are similar to those found in a warming climate, but
with opposite signs. Responses of the largest scale PW during NH and SH
winters differ, leading to hemispheric differences in the interplay
between dynamical and radiative processes. The analysis exposes
remarkable general similarities between climate responses in EQS
simulations and those under nominal solar minimum conditions, even
though the latter may not always appear to be statistically significant.