Enriched Water Abundance over Jupiters High Latitudes and Polar Atmosphere

Constraining the water vapor abundance in Jupiters atmosphere is one of the primary scientific objectives of the Juno mission because it can greatly constrain the formation history of our solar system. During the last five years, Juno inferred the water abundance of about 1-to-5 times solar in the Equatorial Zone (EZ) from the Microwave Radiometers (MWR) data. Jovian Infrared Auroral Mapper (JIRAM) observations show a significant latitudinal variation of water vapors relative humidity at 3-to-5 bar level. It indicates that water vapor, like ammonia vapor, is not well-mixed below the visible weather layer. It also raises a question: where is the best place for Juno to measure the water abundance that can represent Jupiters global oxygen abundance? Here, we design a series of cloud-resolving simulations with cloud-microphysics to simulate the water and ammonia cloud systems in Jupiters mid-latitudes. We find that the atmospheric circulation at the water condensation level significantly differs from the circulation in visible weather layers above. A zonal-mean meridional circulation near the condensation level transports water vapor away from low latitudes to high latitudes. Furthermore, condensation of water splits the convection cells into two parts by forming a stratified stable layer. Our simulated water relative humidity is quantitatively consistent with JIRAMs observation. The relative humidity is 10~20% in belts and ~3% in zones at 4.5 bar. Despite the belt-and-zone contrast, water at low latitudes is relatively depleted compared with that at high latitudes at the same pressure level. At 7 to 8 bars level, water vapor abundance is about three times solar at high latitudes, consistent with our specified deep water abundance in the model, while low latitudes possess only about one solar water vapor. We argue that water plays an essential role in Jupiters atmospheric dynamics and suggest that the high latitudes and polar region of Jupiter may be a better place for the Juno Extended Mission to measure the water abundance that can represent the global value of the deep reservoir.