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.

In previous research, Rohli et al. (2005) identified long‐term features of the northern hemispheric circumpolar vortex (NHCPV) in January. This research provides a seasonal analysis using December and February to augment the previously analyzed January data in representing winter, along with April, July, and October data to represent spring, summer, and autumn, respectively. A representative 500 hPa geopotential height contour was selected to delineate the NHCPV in each of the five months. The area, shape, and centroid of the monthly December, February, April, July, and October NHCPV are computed for 1959–2001 to supplement the previously identified January properties. These geometrical features of the NHCPV reveal relationships between hemispheric‐scale circulation and temperature anomalies throughout the year. A circularity ratio (Rohli et al., 2005) is used to characterize the shape of the hemispheric‐scale circulation. Results suggest that only October exhibit long‐term trends in either area or circularity, with July being the most variable month in area and October being the most variable month in circularity. Centroids tend to be skewed toward the Pacific basin, except in spring, but few systematic temporal shifts in centroid position were noted for any month. The NHCPV is correlated with atmospheric teleconnection patterns in several months. For example, as was the case for January (Rohli et al., 2005), the Arctic Oscillation (AO) is associated with the area of the December, February, and April NHCPV, while in December the circularity is positively correlated to the AO Index. Also, the Pacific‐North American index is correlated with the area of the December and February NHCPV and with the shape of the December and October NHCPV. Copyright © 2006 Royal Meteorological Society

No abstract