Thermal Maps of Jupiter: Spatial Organization and Time Dependence of Stratospheric Temperatures, 1980 to 1990

Abstract

The spatial organization and time dependence of Jupiter's stratospheric temperatures have been measured by observing thermal emission from the 7.8-micrometer CH(4) band. These temperatures, observed through the greater part of a Jovian year, exhibit the influence of seasonal radiative forcing. Distinct bands of high temperature are located at the poles and mid-latitudes, while the equator alternates between warm and cold with a period of approximately 4 years. Substantial longitudinal variability is often observed within the warm mid-latitude bands, and occasionally elsewhere on the planet. This variability includes small, localized structures, as well as large-scale waves with wavelengths longer than approximately 30,000 kilometers. The amplitudes of the waves vary on a time scale of approximately 1 month; structures on a smaller scale may have lifetimes of only days. Waves observed in 1985, 1987, and 1988 propagated with group velocities less than +/-30 meters per second.

Jupiter's North Equatorial Belt expansion and thermal wave activity ahead of Juno's arrival

“…Furthermore, significant stratospheric wave activity was detected at 20 − 30 • N, with wavenumber N = 11 − 13, a small phase speed within an eastward zonal flow, and a mean amplitude of 7.3 ± 2.2 K at 5 mbar. Precursors for this stratospheric wave were identified in December 2014 , and similar stratospheric wave activity was present in 1988 [Orton et al, 1991] and 2001 [Li et al, 2006].…”

“…Previous reports of stratospheric wave activity are sparse, given the difficulties of observing at 7.9 µm. Orton et al [1991] identified N = 11 waves near 22 • N from September to December 1988 (during an expansion), and a stratospheric wave (N ≈ 11) is evident over the 20 − 30 • N region in the 1-4-mbar temperature maps from Cassini in 2000-01 [Flasar et al, 2004;Li et al, 2006]. IRTF/TEXES first identified stratospheric wave activity over a limited longitude range to the north and east of WSZ in December 2014, at a time when the northern edge of the NEB was undulating as a precursor to the 2015-16 expansion .…”

“…Orton et al [1991] tracked stratospheric temperatures from 1980 to 1990 using 7.8-µm CH 4 emission; Orton et al [1994] tracked 250-mbar temperatures from February 1978 to April 1993 using H 2 continuum emission at 18.2 µm. They noted that the mid-NEB tropospheric wave was particularly strong between 1988-1990 (wavenumber ∼ 10 with a ∼ 2 K amplitude, with an estimated westward speed of 5.5 m/s), and again in 1993.…”

“…The interior of the NEB is characterized by upper-tropospheric thermal wave activity [e.g., Magalhaes et al, 1990;Orton et al, 1994;Rogers et al, 2004;Li et al, 2006;Fisher et al, 2016]. Stratospheric waves in the 20−30 • N region were also reported [Orton et al, 1991;Fletcher et al, 2016]. A chronology of these previous wave detections is presented in Supplemental Text S2.…”

Structure of the Jovian Stratosphere at the Galileo Probe Entry Site

“…These curves are used to evaluate the uncertainty in the mole fractions and cooling rates. Horizontal variations in the stratospheric temperature have been addressed by Orton et al (1991), who published maps of brightness temperature in the ν 4 band of CH 4 . These observations revealed that the zonal mean structure alternates between states of warm subtropical (∼14 • ) and cool equatorial regions to cool subtropical and warm equatorial regions, with a period of about four years.…”