Long-term changes and variability in northern hemisphere circumpolar vortex

• Main Author: Wrona, Kalyn MacKenzie
• Format: Text
• Language: unknown
• Published: LSU Scholarly Repository 2005
• Subjects: atmospheric circulation variability; atmospheric teleconnections; circumpolar vortex; Social and Behavioral Sciences; Arctic; Pacific
• Online Access: https://repository.lsu.edu/gradschool_theses/3286; https://doi.org/10.31390/gradschool_theses.3286; https://repository.lsu.edu/context/gradschool_theses/article/4285/viewcontent/uc.pdf

Variability in the hemispheric-scale atmospheric circulation can be directly linked to variations in surface environmental features, such as temperature, precipitation, 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 (GIS) approach to determine the variability in the northern hemisphere (NH) CPV. Specifically, the area, shape, and centroid of the December, January, February, April, July, and October NHCPV are analyzed for 1959 – 2001 because these features may provide insight about relationships between hemispheric-scale circulation and global temperature change throughout the year. A “circularity ratio†is used to characterize the shape of the hemispheric-scale circulation. Results suggest that none of the months analyzed exhibit any long-term trends in area and circularity, with July being the most variable month in area and October being the most variable month in circularity. In general, winter centroids tend to be skewed toward the Pacific basin, but few systematic temporal shifts in centroid position were noted for any month. Many monthly NHCPVs are correlated with atmospheric teleconnection patterns. For example, the Arctic Oscillation (AO) is associated with the area of the December, January, 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, January, and October NHCPV. Cluster analysis resulted in seven clusters consisting of similar wintertime NHCPV properties. Finally, clear regional patterns emerge that suggest that the area and circularity are associated with variability in surface temperature and moist static energy in various regions of the northern hemisphere. These results may facilitate understanding of the relationship between hemispheric- and regional-scale circulation ...