The Effects of Radiation on Tropopause Polar Vortices over the Greenland Ice Sheet

Tropopause Polar Vortices (TPVs) are long-lived, coherent vortices that are identified by closed material contours of potential temperature on the tropopause. Since these potential vorticity anomalies spend most of their lifetime in the Arctic, they can impact their surrounding environment by introducing variability in sea ice, generating surface cyclones, and intensifying midlatitude weather systems when carried equatorward by the Polar jet stream. While several studies have modeled the structure and climatology of TPVs, there is much to be discovered in terms of their evolution, intensification, and genesis. Case studies and composite studies from previous model simulations have shown that changes in TPV intensity can be attributed to local factors such as radiative cooling and latent heating. Numerical simulations indicate that clear-sky longwave radiative cooling is an important factor in the maintenance of TPVs while clouds can contribute to large amplitude changes in response to cloud-top radiative cooling in the vortex core. This study uses cloud and atmospheric state observations from Summit Station, Greenland, to investigate the effects of clear-sky, ice-only, and all-sky radiative cooling on TPV intensification.

As part of the Integrated Characterization of Energy, Clouds, Atmospheric State, and Precipitation at Summit (ICECAPS) project, observations of tropospheric and cloud properties at Summit Station, Greenland have been collected since 2010. This ground-based observing system combined with temperature and humidity profiles from ERA5, which assimilates the twice-daily soundings launched at Summit, provides novel details of local characteristics of TPVs. The atmospheric state and cloud property data used in conjunction with stand-alone version of the Rapid Radiative Transfer Model is used to analyze shortwave and longwave radiative contributions to TPV diabatic intensity changes from both clouds and clear-sky water vapor effects.