Saturn's largest moon, Titan, has an Earth-like volatile cycle, but with
methane playing the role of water and surface liquid reservoirs geographically
isolated at high latitudes. We recreate Titan's characteristic dry hydroclimate
at the equator of an Earth-like climate model without seasons and with water as
the condensable by varying a small set of planetary parameters. We use three
observationally motivated criteria for Titan-like conditions at the equator: 1)
the peak in surface specific humidity is not at the equator, despite it having
the warmest annual-mean temperatures; 2) the vertical profile of specific
humidity in the equatorial column is nearly constant through the lower
troposphere; and 3) the relative humidity near the surface at the equator is
significantly lower than saturation (lower than 60%). We find that simply
reducing the available water at the equator does not fully reproduce Titan-like
conditions. We additionally vary the rotation period and volatility of water to
mimic Titan's slower rotation and more abundant methane vapor. Longer rotation
periods coupled with a dry equatorial surface meet fewer of the Titan-like
criteria than equivalent experiments with shorter rotation periods. Experiments
with higher volatility of water meet more criteria than those with lower
volatility, with some of those with the highest volatility meeting all three,
demonstrating that an Earth-like planet can display Titan-like climatology by
changing only a few physical parameters.
Preprint
Comment: 40 pages, 18 figures
Subjects: Astrophysics - Earth and Planetary Astrophysics; Physics - Atmospheric and Oceanic Physics