Open AccessSubseasonal Variation in Neptune’s Mid-infrared Emission
Author(s) -
Michael T. Roman,
Leigh N. Fletcher,
Glenn S. Orton,
Thomas Greathouse,
J. I. Moses,
Naomi Rowe-Gurney,
Patrick Irwin,
Arrate Antuñano,
James Sinclair,
Yasumasa Kasaba,
Takuya Fujiyoshi,
Imke de Pater,
Heidi B. Hammel
Publication year - 2022
Publication title -
the planetary science journal
Language(s) - English
Resource type - Journals
ISSN - 2632-3338
DOI - 10.3847/psj/ac5aa4
Subject(s) - neptune , stratosphere , solstice , troposphere , environmental science , atmospheric sciences , northern hemisphere , context (archaeology) , climatology , geology , physics , astronomy , planet , latitude , paleontology
We present an analysis of all currently available ground-based imaging of Neptune in the mid-infrared. Dating between 2003 and 2020, the images reveal changes in Neptune’s mid-infrared (∼8–25 μ m) emission over time in the years surrounding Neptune’s 2005 southern summer solstice. Images sensitive to stratospheric ethane (∼12 μ m), methane (∼8 μ m), and CH 3 D (∼9 μ m) display significant subseasonal temporal variation on regional and global scales. Comparison with H 2 S(1) hydrogen quadrupole (∼17.035 μ m) spectra suggests that these changes are primarily related to stratospheric temperature changes. The stratosphere appears to have cooled between 2003 and 2009 across multiple filtered wavelengths, followed by a dramatic warming of the south pole between 2018 and 2020. Conversely, upper-tropospheric temperatures—inferred from ∼17 to 25 μ m imaging—appear invariant during this period, except for the south pole, which appeared warmest between 2003 and 2006. We discuss the observed variability in the context of seasonal forcing, tropospheric meteorology, and the solar cycle. Collectively, these data provide the strongest evidence to date that processes produce subseasonal variation on both global and regional scales in Neptune’s stratosphere.