CH4 mixing ratios at microbar pressure levels of Jupiter as constrained by 3-micron ISO data

Infrared Space Observatory (ISO) data of Jupiter are revisited in order to derive CH4 mixing ratios at microbar pressures in the atmosphere. We utilize the most updated radiative transfer programs to construct a 3-μm emission model of CH4 to be compared with the ISO data. From the model-data comparisons, we derive the high-altitude CH4 mixing ratios, which turn out to be at least 10 times smaller than the microbar CH4 mixing ratios assumed in the Galileo probe analysis (Seiff, A. et al., 1998. Thermal structure of Jupiter’s atmosphere near the edge of a 5-μm hot spot in the north equatorial belt. J. Geophys. Res., 103, 22857–22889. doi:10.1029/98JE01766), but which are approximately consistent with ultraviolet airglow observations and with available photochemical models that assume relatively weak atmospheric mixing. We also compare the derived CH4 profile with results from other investigations reported in literature and discuss the implications with respect to photochemistry and vertical transport in the stratosphere of Jupiter.