Midlatitude jet streams, narrow bands of strong upper atmospheric winds, steer high- and low-pressure weather systems and help maintain our planet’s habitable climate. They are closely related to the preferred track of midlatitude low-pressure storm systems known as storm tracks.
The position and intensity of jet streams typically vary in response to processes that affect surface temperature gradients between the equator and the poles. Although many comprehensive climate models predict that Earth’s jet streams will shift poleward as the planet warms, the projected magnitudes of these shifts appear to vary widely depending upon the planet’s response to changes in radiative energy.
Now Tan et al. have developed a series of simulations to test how different approaches to modeling radiation can affect the response of jet streams to global warming. The results indicate that when using a gray radiation scheme, which has been used in many simplified modeling studies, the midlatitude jet stream responds by shifting toward the equator rather than the pole.
The authors conclude that despite the prevalence of the gray radiation scheme, this approach does not adequately capture the circulation response to global warming. Instead, the researchers showed that using a simple, four-band longwave radiation scheme that incorporates the effects of water vapor more effectively replicates circulation responses in full general circulation models.
The results suggest the authors’ model captures the fundamental processes that influence the response of midlatitude circulation to increasing temperatures and demonstrate that this approach can boost our understanding of how jet streams and storm tracks will respond to future warming. (Journal of Advances in Modeling Earth Systems (JAMES), https://doi.org/10.1029/2018MS001492, 2019)
—Terri Cook, Freelance Writer