Comparison of a simple 2‐D Pluto general circulation model with stellar occultation light curves and implications for atmospheric circulation

Abstract

We use a simple Pluto general circulation model (sPGCM) to predict for the first time the wind on Pluto and its global, large‐scale structure, as well as the temperature and surface pressure. Wind is a fundamental atmospheric variable that has previously been neither measured nor explicitly modeled on Pluto. We ran the sPGCM in 2‐D mode (latitude, height, and time varying) using the Massachusetts Institute of Technology general circulation model dynamical core, a simple radiative‐convective scheme, and no frost cycle. We found that Pluto's atmosphere is dynamically active in the zonal direction with high‐speed, high‐latitude jets that encircle the poles in gradient wind balance and prograde with Pluto's rotation. The meridional and vertical winds do not show evidence for a Hadley cell (or other large‐scale structure) due to the low‐altitude temperature inversion. The horizontal variation in surface pressure is a small fraction of the previously derived interannual variation in surface pressure. The simple general circulation model output was validated with stellar occultation light curve data from the years 1988, 2002, 2006, and 2007. For 2006 and 2007, the best fit global mean surface pressure was 24 microbar, in 2002 it was 22 microbar, and in 1988 it was 12 microbar (1 microbar error bars). For all years the methane mixing ratio was 1% (0.2% error bars). This work is a first step for future Pluto, Triton, and Kuiper Belt object atmosphere general circulation models that will also include longitudinal variations and a volatile cycle.