Thermal Emission From Saturn's Polar Cyclones

We have used data from the Cassini Composite Infrared Spectrometer to map the temperatures in Saturn's polar cyclones at the highest spatial resolution obtained during the Cassini mission. We find temperature contrasts of 7K in the upper troposphere within 1.4 degrees of both poles, roughly 50 percent larger than earlier measurements at lower spatial resolution. The polar hot spots weaken with depth, disappearing near 500 mbar. In the stratosphere, the polar hot spot becomes broader, extending 4 degrees from the poles, and weakens with altitude disappearing near 1mbar. A thermal relaxation model shows that the tropospheric hot spot is consistent with adiabatic heating from subsidence with a vertical velocity of about -0.05mm/s above 500mbar. The observed temperature gradients imply that the winds in the polar cyclone decay with increasing altitude over roughly three pressure scale heights above the 200-mbar level. Plain Language Summary We have used data from the Composite Infrared Spectrometer to map the temperatures in Saturn's polar cyclones during the Cassini mission. The final orbits of the mission enabled the highest spatial resolution data (20km) of the mission. The analysis of this data reveals temperature contrasts of 7 degrees C (11 degrees F) in the upper troposphere within 1.4 degrees of both poles which is roughly 50% larger than measurements taken at lower spatial resolution earlier in the mission. We find that the polar hot spot temperature contrast weakens with depth in the troposphere. It was discovered that the hot spot temperature contrast in the stratosphere is broader than seen in the troposphere and weakens with increased altitude. The tropospheric temperature contrasts can be explained by slowly descending vertical winds at a rate of 0.05mm/s. We observed that the temperature gradients are consistent with rapidly decaying winds over increasing altitude at the tropopause.