A synoptic scale perspective of solar forcing on extreme precipitation
and floods over Europe during summer
Abstract
The relationship between total solar irradiance (TSI) forcing and summer
extreme precipitation and flood frequency over western Europe is
investigated from a synoptic-scale perspective, with a focus on the role
of Rossby Wave Packets (RWPs). Utilizing observational, model, and proxy
data, we reveal a significant increase in RWP frequency along a zonal
band centered around 50°N, extending from North America to western
Europe, during periods of low TSI. This anomaly in RWP frequency is
consistent with a significant increase in the frequency of extreme
precipitation events recorded over western Europe. Sensitivity
experiments conducted with a state-of-the-art chemistry-climate model
corroborate our findings based on observational data. Additionally, a
flood record from western Europe demonstrates a significant increase in
flood frequency during low TSI years, a relationship that persists
across timescales. We argue that the frequency patterns associated with
TSI forcing presented in this study are robust and, therefore, valuable
for estimating the frequency of extreme precipitation events over
western Europe under various solar irradiance scenarios. Moreover, our
findings indicate that the North Atlantic sector is more responsive to
changes in solar forcing during the boreal summer than previously
thought, with this effect manifesting primarily on synoptic timescales
rather than the long-term climatological mean.