  Secondary eclipse observations of ultra-hot Jupiters have found evidence that
hydrogen is dissociated on their daysides. Additionally, full-phase light curve
observations of ultra-hot Jupiters show a smaller day-night emitted flux
contrast than that expected from previous theory. Recently, it was proposed by
Bell & Cowan (2018) that the heat intake to dissociate hydrogen and heat
release due to recombination of dissociated hydrogen can affect the atmospheric
circulation of ultra-hot Jupiters. In this work, we add cooling/heating due to
dissociation/recombination into the analytic theory of Komacek & Showman (2016)
and Zhang & Showman (2017) for the dayside-nightside temperature contrasts of
hot Jupiters. We find that at high values of incident stellar flux, the
day-night temperature contrast of ultra-hot Jupiters may decrease with
increasing incident stellar flux due to dissociation/recombination, the
opposite of that expected without including the effects of
dissociation/recombination. We propose that a combination of a greater number
of full-phase light curve observations of ultra-hot Jupiters and future General
Circulation Models that include the effects of dissociation/recombination could
determine in detail how the atmospheric circulation of ultra-hot Jupiters
differs from that of cooler planets.

Earth and Planetary Astrophysics;Atmospheric and Oceanic Physics