Over the last eight years , a rich dataset of mid-infrared CH 4 observations from the TEXES instrument at IRTF has been used to characterize the thermal evolution of Jupiter ’ s stratosphere .
These data were used to produce vertically-resolved temperature maps between latitudes of 50 ^ { \circ } S and 50 ^ { \circ } N , allowing us to track approximately two periods of Jupiter ’ s quasi-quadrennial oscillation ( QQO ) .
During the first five years of observations , the QQO has a smooth sinusoidal pattern with a period of 4.0 \pm 0.2 years and an amplitude of 7 \pm 1 K at 13.5 mbar ( our region of maximum sensitivity ) .
In 2017 , we note an abrupt change to this pattern , with the phase being shifted backwards by \sim 1 year .
Searching for possible causes of this QQO delay , we investigated the TEXES zonally-resolved temperature retrievals and found that in May/June 2017 , there was an unusually warm thermal anomaly located at a latitude of 28 ^ { \circ } N and a pressure of 1.2 mbar , moving westward with a velocity of 19 \pm 4 ms -1 .
We suggest that there may be a link between these two events .