April 22, 2020 - 3:00 pm
April 22, 2020 - 4:00 pm
CategoriesWeather and Climate Systems
Tropopause Polar Vortex Climatology and Linkages with Rossby Wave Initiation
Wednesday, April 22nd
3:00pm Central Time (US and Canada)/Zoom Meeting
Join Zoom Meeting
Meeting ID: 505 651 584
Zoom Password: 996546
Tropopause Polar Vortices (TPVs) are coherent vortices along the tropopause, identified by a local minimum in temperature and local maximum in potential vorticity along the dynamic tropopause. TPVs are most often found in high latitudes poleward of 60ºN and are important features in midlatitude and polar synoptic meteorology, associated with cyclogenesis, cold air outbreaks, and Rossby Wave initiation (RWI). The primary pathways of TPVs into the midlatitudes are through northern Canada and Siberia. Rossby Waves are identified as a packet of troughs and ridges propagating along the midlatitude jet stream, with RWI occurring most frequently over the western North Pacific Ocean. RWI events in this region are associated with an upstream wave train propagating over Asia, antecedent downstream ridge, and increased moisture transport along a zonal midlatitude jet, which is subsequently perturbed.
Prior studies exist on the climatology of TPV location and structure but are relatively lacking with regard to a climatological analyses of TPV transport from Polar Regions into midlatitudes and whether there is an association with RWI events. The objective of this work is to create an updated climatology of TPV transportation into midlatitudes, and to identify TPV linkages with RWI events with the expectation that TPVs would be located poleward of the RWI location acting as positive potential vorticity anomalies that perturb the zonal jet. Analysis of December through February TPV tracks and RWI locations based on the ERA-Interim (ERA-I) reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF) reveals that about 22 percent of all wintertime TPVs are identified as having been transported into the midlatitudes. The most common pathways for TPV transportation into the midlatitudes are via northern Canada and northern Siberia and smaller maxima over northern Scandinavia and over western Alaska. Of the 875 RWI events analyzed, 82% are found to be associated with a TPV, with most TPVs located up to 2500 km poleward of the RWI location and no notable west or east preference.