Planetary Climate Dynamics

Abstract:

Hypotheses involving energetic constraints and the down-gradient diffusion of heat in eddy parameterization theories are tested by estimating baroclinic eddy transports in rotating annulus laboratory experiments. Particle Imaging Velocimetry measurements are supplemented by numerical simulations to estimate variables not measured directly. The results with a topographic beta effect broadly support Fick's first law, and are consistent with the GEOMETRIC framework in which eddy buoyancy flux is constrained by total eddy energy. With the topographic beta effect, a relatively simple relation is observed between the eddy buoyancy flux and the total eddy energy, with the ratio quantifying the eddy transport efficiency. This efficiency decreases in more complex flow regimes with larger rotation rates, associated with the changing energy partition between eddy available potential energy and eddy kinetic energy. In the absence of a topographic beta effect, more complicated dependencies are found, suggesting roles for other variables.

Abstract:

Abstract:

The prevalence of atmospheres on rocky planets is one of the major questions in exoplanet astronomy, but there are currently no published unambiguous detections of atmospheres on any rocky exoplanets. The MIRI instrument on JWST can measure thermal emission from tidally locked rocky exoplanets orbiting small, cool stars. This emission is a function of their surface and atmospheric properties, potentially allowing detections of atmospheres. One way to find atmospheres is to search for lower dayside emission than would be expected for a blackbody planet. Another technique is to measure phase curves of thermal emission to search for nightside emission due to atmospheric heat redistribution. Here, we compare strategies for detecting atmospheres on rocky exoplanets. We simulate secondary eclipse and phase curve observations in the MIRI F1500W and F1280W filters for a range of surfaces (providing our open-access albedo data) and atmospheres on 30 exoplanets selected for their F1500W signal-to-noise ratio. We show that secondary eclipse observations are more degenerate between surfaces and atmospheres than suggested in previous work, and that thick atmospheres can support emission consistent with a blackbody planet in these filters. These results make it difficult to unambiguously detect or rule out atmospheres using their photometric dayside emission alone. We suggest that an F1500W phase curve could instead be observed for a similar sample of planets. While phase curves are time-consuming and their instrumental systematics can be challenging, we suggest that they allow the only unambiguous detections of atmospheres by nightside thermal emission.