Evaluation of tropospheric impacts due to the warm 2019 SH polar winter and the cold 2019-2020 NH polar winter.

The 2019 Southern Hemisphere high latitudes were influenced by a minor warming resulting in displacement of the polar vortex well off the polar cap. This displacement generated consistently positive geopotential height (GPH) anomalies throughout the stratosphere for September and early October. The changes in the polar vortex were followed by positive GPH anomalies (negative Antarctic Oscillation, AAO) throughout the lower stratosphere and troposphere from mid-October through December. We will evaluate the impacts of this sustained negative AAO on tropospheric circulation and precipitation patterns which may have enabled the wildfires in Australia. Conversely, the 2019-2020 Northern Hemisphere winter was characterized by an anomalously stable, cold, polar vortex. These conditions generated sustained negative GPH anomalies extending throughout the stratosphere and troposphere. The associated positive Arctic Oscillation (AO) pattern was characterized by a contracted polar circulation which affected weather systems, snow fall, and unusually warm winter temperatures in the mid-latitudes. We will evaluate these impacts as well.