A Direct Comparison between the use of Double Gray and Multiwavelength
Radiative Transfer in a General Circulation Model with and without
Radiatively Active Clouds
Inhomogeneous cloud formation and wavelength-dependent phenomena are expected
to shape hot Jupiter atmospheres. We present a General Circulation Model (GCM)
with multiwavelength "picket fence" radiative transfer and radiatively active,
temperature dependent clouds, and compare the results to a double gray routine.
The double gray method inherently fails to model polychromatic effects in hot
Jupiter atmospheres, while picket fence captures these non-gray aspects and
performs well compared to fully wavelength-dependent methods. We compare both
methods with radiatively active clouds and cloud-free models, assessing the
limitations of the double gray method. Although there are broad similarities,
the picket fence models have larger day-night side temperature differences,
non-isothermal upper atmospheres, and multiwavelength effects in the presence
of radiatively active clouds. We model the well-known hot Jupiters HD 189733 b
and HD 209458 b. For the hotter HD 209458 b, the picket fence method prevents
clouds from thermostating dayside temperatures, resulting in hotter upper
atmospheres and the dissipation of dayside clouds. Differences in the
temperature structures are then associated with nuanced differences in the
circulation patterns and clouds. Models of the cooler HD 189733 b have global
cloud coverage, regardless of radiative transfer scheme, whereas there are
larger differences in the models of HD 209458 b, particularly in the extent of
the partial cloud coverage on its dayside. This results in minor changes to the
thermal and reflected light phase curves of HD 189733 b, but more significant
differences for the picket fence and double gray versions of HD 209458 b.Comment: Submitted to ApJ, 31 page