TY - JOUR
T1 - The Sensitivity of Superrotation to the Latitude of Baroclinic Forcing in a Terrestrial Dry Dynamical Core
AU - Zurita-Gotor, Pablo
AU - Anaya-Benlliure, Álvaro
AU - Held, Isaac M.
N1 - Funding Information:
Acknowledgments. This work was funded by the National Science Foundation Grant AGS-1733818. P.Z.-G. acknowledges support from Grant PID2019-109107GB-I00 by the Spanish Ministry of Science, Innovation and Universities and funding by Santander UCM Grant PR87/19-22537 for the workstation in which the simulations were performed. We thank J. Schröttle and two anonymous reviewers for suggestions that improved the manuscript.
Publisher Copyright:
© 2022 American Meteorological Society.
PY - 2022
Y1 - 2022
N2 - Previous studies have shown that Kelvin–Rossby instability is a viable mechanism for producing equatorial superrotation in small and/or slowly rotating planets. It is shown in this paper that this mechanism can also produce superrotation with terrestrial parameters when the baroclinic forcing moves to low latitudes, explaining previous results by Williams. The transition between superrotating and subrotating flow occurs abruptly as the baroclinic forcing moves poleward. Although Kelvin–Rossby instability weakens when the baroclinic zone moves away from the equator, the key factor explaining the abrupt transition is the change in the baroclinic eddies. When differential heating is contained within the tropics, baroclinic eddies do not decelerate the subtropical jet and the upper-tropospheric flow approximately conserves angular momentum, providing conditions favorable for Kelvin–Rossby instability. In contrast, when baroclinic eddies are generated in the extratropics, they decelerate the subtropical jet and prevent the Kelvin–Rossby coupling. Due to this sensitivity to baroclinic eddies, the system exhibits hysteresis: near the transition parameter, extratropical eddies can prevent superrotation when they are initially present.
AB - Previous studies have shown that Kelvin–Rossby instability is a viable mechanism for producing equatorial superrotation in small and/or slowly rotating planets. It is shown in this paper that this mechanism can also produce superrotation with terrestrial parameters when the baroclinic forcing moves to low latitudes, explaining previous results by Williams. The transition between superrotating and subrotating flow occurs abruptly as the baroclinic forcing moves poleward. Although Kelvin–Rossby instability weakens when the baroclinic zone moves away from the equator, the key factor explaining the abrupt transition is the change in the baroclinic eddies. When differential heating is contained within the tropics, baroclinic eddies do not decelerate the subtropical jet and the upper-tropospheric flow approximately conserves angular momentum, providing conditions favorable for Kelvin–Rossby instability. In contrast, when baroclinic eddies are generated in the extratropics, they decelerate the subtropical jet and prevent the Kelvin–Rossby coupling. Due to this sensitivity to baroclinic eddies, the system exhibits hysteresis: near the transition parameter, extratropical eddies can prevent superrotation when they are initially present.
KW - Angular momentum
KW - Atmospheric circulation
KW - Eddies
KW - General circulation models
KW - Idealized models
KW - Instability
KW - Kelvin waves
KW - Planetary atmospheres
UR - http://www.scopus.com/inward/record.url?scp=85128697411&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85128697411&partnerID=8YFLogxK
U2 - 10.1175/JAS-D-21-0269.1
DO - 10.1175/JAS-D-21-0269.1
M3 - Article
AN - SCOPUS:85128697411
SN - 0022-4928
VL - 79
SP - 1311
EP - 1323
JO - Journal of the Atmospheric Sciences
JF - Journal of the Atmospheric Sciences
IS - 5
ER -