Examining a Relationship Between Tropopause Polar Vortex Intensity and Warm Conveyor Belt Strength

Tropopause polar vortices (TPVs) are coherent circulation features with origins in polar regions and are represented by potential vorticity (PV) anomalies near the tropopause. These upper-level PV anomalies are important for the formation and evolution of surface cyclones, and hence TPVs can be viewed as a precursor to surface cyclones, especially in the Arctic. Warm conveyor belts (WCBs) are areas of enhanced ascent, water vapor transport, and diabatic heating associated with surface cyclones. Diabatic heating within the WCB often leads to or enhances cyclonic PV anomalies near the surface, and it is proposed here that there is a positive correlation between the magnitudes of these PV anomalies and the intensities of the features which cause them. Correlations have previously been found between the strength of WCBs and the intensification of extratropical surface cyclones; however, it is not established whether this link also applies specifically to Arctic cyclones. Moreover, given that TPVs and Arctic cyclones are related, linking TPVs to WCBs could expand knowledge and improve forecast skill of WCBs and their impacts, most notably on precipitation. This study examines whether there is indeed a correlation between TPV intensity and WCB strength. Two methods are used to assess WCB strength: low-level air mass within the WCB, and northward integrated vapor transport (IVT). TPV intensity is defined here by the departure of the TPV minimum potential temperature from its long-term climatological value. Northern Hemisphere cyclone and TPV tracks from ERA-Interim from 1984 to 2016 are utilized to perform this analysis, with a focus on the correlations between TPVs, Arctic cyclones, and WCBs. We find relatively weak correlations with the WCB, which we find may be better quantified using northward IVT due to the relatively small amounts of latent heating and ascent in the Arctic in comparison to the midlatitudes.