Quantifying the Effect of Climate Change on Midlatitude Subseasonal
Prediction Skill Provided by the Tropics
Abstract
Subseasonal timescales (~2 weeks - 2 months) are known
for their lack of predictability, however, specific Earth system states
known to have a strong influence on these timescales can be harnessed to
improve prediction skill (known as “forecasts of opportunity”). As the
climate continues warming, it is hypothesized these states may change
and consequently, their importance for subseasonal prediction may also
be impacted. Here, we examine changes to midlatitude subseasonal
prediction skill provided by the tropics under anthropogenic warming
using artificial neural networks to quantify skill. The network is
tasked to predict the sign of the 500hPa geopotential height for
historical and future time periods in the CESM2-LE across the Northern
Hemisphere at a 3 week lead using tropical precipitation. We show
prediction skill changes substantially in key midlatitude regions and
these changes appear linked to changes in seasonal variability with the
largest differences in accuracy occurring during forecasts of
opportunity.