Planetary and exoplanetary Astronomy Lunch Seminar (PALS) for 2022-10-24

Series: Planetary and exoplanetary Astronomy Lunch Seminar (PALS)
Date: Monday 24-October-2022
Time: 11:15-12:15
Location: Zoom (contact for link)
Speaker: Shuang Wang
Title: Equatorial Superrotation and Waves in the Atmosphere and Ocean of Tidally Locked Planets

Abstract: The phase curve observations of 1:1 tidally locked planets including hot Jupiters usually show an eastward shift, which is caused by atmospheric equatorial superrotation (i.e., west-to-east winds over the equator). The superrotation is due to the equator-ward momentum transports by stationary planetary waves. The planetary waves on tidally locked planets are dominated by wavenumber-1, stationary, off-equatorial Rossby waves and equatorial Kelvin waves, which are considered to be the Matsuno-Gill mode. However, the feedbacks of such a strong superrotation on the planetary waves are rarely studied. In this study, we solve the 1-layer shallow water equations analytically to get the wave patterns under a prescribed zonal flow, and find that the zonal flow can shift the phase of planetary waves. The degree of the phase shift is a monotonic but nonlinear function of the strength of the zonal flow, and the phase shift has two limits of -180 and 180 degrees. The two limits are constrained by the energy budget of the whole system. We also find a resonance between planetary waves and the zonal flow occurs when the speed of zonal flow approaches to the phase speed of the waves but with opposite sign. The resonance is also constrained by the energy budget of this system.

Furthermore, we will show that there should also exist equatorial superrotation and planetary waves in the ocean. The waves are excited from heat source and wind stress, and they are in opposite phase. Both types of flows can transport eddy momentum to the equator, which can produce and maintain the oceanic superrotation. The oceanic superrotation can be found in analytical solutions and numerical simulations, and it may be observed on magma ocean planets by the telescope of JWST in the near future.

For further information contact PALS coordinator Tad Komacek at


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