January northern hemisphere circumpolar vortex variability and its relationship with hemispheric temperature and regional teleconnections

Abstract

Variability in the hemispheric-scale atmospheric circulation can be directly linked to variations in surface environmental features, such as temperature, precipitation, salinity of water bodies, and pollutant transport. One indicator of the behavior of the hemispheric-scale circulation is the circumpolar vortex (CPV). This research utilizes a geographic information system approach to characterize variability in the Northern Hemispheric (NH) CPV. Specifically, the area, shape, and centroid of the January NHCPV are analyzed for 1959-2001 because it may provide insight about relationships between hemispheric-scale circulation and global temperature change. We also use a new means of characterizing the hemisphericscale circulation using a 'circularity ratio' (R c ). Results suggest that the January NHCPV has exhibited no long-term trends in area or shape, and that the mean centroid is positioned at approximately 85.3°N, 178.0°W. Regional patterns emerge, which suggest that the area and circularity are associated with variability in surface temperature and moist static energy. Furthermore, the area of the January NHCPV is associated with variability in the Arctic Oscillation, while the shape is tied to variability in the Pacific-North American teleconnection pattern. These results will facilitate understanding of the relationship between hemispheric-scale circulation, regional circulation, and local temperatures.

Decadal-Scale Trends in Transition Weather Types and Atmospheric Circulation

“…represents a recent revision of the North Pacific Oscillation (NPO) found in many previous studies of NH SLP variability (e.g., Rogers 1990), and the pattern has also been identified as the IPO (e.g., Power et al, 1997) (Mantua and Hare 2002) alternating patterns on the order of months to years, the PDO acts over much longer time scales (two to three decades, Rohli et al 2005).…”

“…A significant relationship was also found between CPV circularity and PNA, with the positive phase of the PNA associated with a less circular vortex (more meridionality). The contrasting results to Frauenfeld and Davis (2003) and were thought to arise from the use of differing map projections, or a different period of record (Rohli et al, 2005;Wrona and Rohli 2007). …”

“…Work of , Frauenfeld and Davis (2003) and Rohli et al (2005) and Wrona and Rohli (2007) examined vortex trends using GIS software and found no statistically significant trends in vortex shape or size for most seasons. The contrast between their work and that of Frauenfeld and Davis (2003) and may arise from differing map projections and methods (Wrona and Rohli 2007).…”

“…The strongest feature of the jet stream in both hemispheres is located along the southern boundary of a polar vortex, the region in the upper atmosphere of maximum meridional geopotential height gradient (Frauenfeld & Davis 2003). A contracting winter polar vortex has been observed in recent decades (Davis & Benkovic 1992, Frauenfeld & Davis 2003, although some research suggests no temporal trends (Rohli et al 2005). Jet stream probabilities have been increasing over Canada, consistent with a contracting vortex (Strong & Davis 2007).…”

“…Because of the agreement between Frauenfeld and Davis (2003) and , and the hypothesis of Rohli et al (2005), that increasing mid-latitude temperatures should be associated with decreasing CPV area, it seems that relationships between the CPV and TR frequency should be examined. The work of Rohli et al (2005) and Wrona and Rohli (2007) formally identifies a second important feature of the CPV that may be related to TR activity: the shape (represented through their circularity ratio). As enhanced meridional flow in the CPV suggests increased pole-toequator exchange of momentum and heat, circularity should be related to cyclogenesis, and thus, TR.…”