A 3D general circulation model for Pluto and Triton with fixed volatile abundance and simplified surface forcing

TL;DR

This paper develops a 3D general circulation model for Pluto and Triton, revealing horizontal heat transport, weak vertical motions, and explaining observed atmospheric features without the need for a traditional troposphere.

Contribution

The model introduces a simplified approach with fixed volatile abundance and surface forcing, providing new insights into the atmospheric dynamics of Pluto and Triton.

Findings

Easterly jets at the equator with maximum speeds of 10-12 m/s on Pluto and 4 m/s on Triton.

Minimal meridional and vertical overturning circulation in both atmospheres.

Horizontal motions dominate heat transport, with small temperature contrasts (<5 K).

Abstract

We present a 3D general circulation model of Pluto and Triton's atmospheres, which uses radiative-conductive-convective forcing. In both the Pluto and Triton models, an easterly (prograde) jet is present at the equator with a maximum magnitude of 10-12 m/s and 4 m/s, respectively. Neither atmosphere shows any significant overturning circulation in the meridional and vertical directions. Rather, it is horizontal motions (mean circulation and transient waves) that transport heat meridionally at a magnitude of 1 and 3 x 10^7 W at Pluto's autumn equinox and winter solstice, respectively (seasons referenced to the Northern Hemisphere). The meridional and dayside-nightside temperature contrast is small (<5 K). We find that the lack of vertical motion can be explained on Pluto by the strong temperature inversion in the lower atmosphere. The height of the Voyager 2 plumes on Triton can be explained by the dynamical properties of the lower atmosphere alone (i.e., strong wind shear) and does not require a thermally defined troposphere (i.e., temperature decreasing with height at the surface underlying a region of temperature increasing with height). The model results are compared with Pluto stellar occultation light curve data from 1988, 2002, 2006, and 2007 and Triton light curve data from 1997.