Characterization of the Structure of Tropopause Polar Vortices through Atmospheric Infrared Sounder (AIRS) Retrievals

Tropopause polar vortices (TPVs) are atmospheric coherent vortex-like structures originating poleward of the jet stream and exhibit a closed circulation of the wind along the 2-PVU dynamic tropopause. Cyclonic TPVs interact with the jet stream and synoptic mid-latitude systems and play an important role in the genesis and strengthening of surface cyclones as well as the variability of sea ice. This has been the motivation for previous and current studies in TPV behavior, evolution, climatology, and structure through the utilization of reanalysis and modeling components. However, observationally-based studies of TPVs are still relatively new, yet offer appreciable insight to TPV model-based research. As part of this endeavor, this project uses remote sensing techniques to observe the internal structure of cyclonic TPVs and to verify these results with previous model studies on TPV spatial variability.

To observe the spatial variability of clouds and the atmospheric state of TPVs, this study utilizes the AIRS/AMSU Version 6 Level 2 retrieval product, which is derived from infrared and microwave spectra collected by the Atmospheric Infrared Sounder (AIRS) and Advanced Microwave Sounding Unit (ASMU) instruments aboard the low-orbit polar-orbiting Aqua satellite. This retrieval product’s robustness in penetrating through cloudy environments allows relatively unobstructed views of the spatial variability of temperature, moisture, and ozone fields, which are important characteristics affecting the intensity of cyclonic TPVs. We also evaluate these satellite retrievals against radiosonde data collected during TPV events whenever applicable. Case studies of TPV events detected through this satellite remote sensing method support the TPV structure found in previous model studies, including a lowering of the tropopause, relatively cooler (warmer) temperatures below (above) the tropopause than the surrounding environment, and higher (lower) relative humidity below (above) the tropopause.