A Pilot Study of the Northern Hemisphere’s Circumpolar Vortex Centroid Positions over Time and Space

Abstract:

Our previous research has established a “sharpest gradient” approach for delineating the leading edge of the circumpolar vortex and identified correlations of the area and circularity of the Northern Hemisphere’s circumpolar vortex (NHCPV) to important atmospheric-oceanic teleconnections. However, the previous research failed to address the geographical shifts in the NHCPV, independent of area or circularity changes, which could occur. This research examines the question of the extent to which the daily NHCPV centroid undergoes spatial and temporal variability, from 1979 through 2017. Time series analysis for linear trend of day to day distance of the NHCPV centroids suggests that the centroid of the NHCPV displays only minimal long-term temporal trends. This result suggests that the middle-to-upper troposphere may not have yet responded fully to the near-surface warming over the last few decades. Spectral analysis shows high-frequency variability modes of two periodic signals (i.e., semiannual (2 yr⁻¹) and quarterly (4 yr⁻¹)) which suggests influence of the cold-warm season flow, and four-season environment, respectively, with both cycles varying in magnitude. Emerging hot spot analysis shows that centroid hot spots are distributed from north of the Bering Sea to south of Iceland where of the 3681 location “bins,” 883 show a statistically significant (p< 0.05) linear trend in their hot spot category, among which 27.18% are persistent, 22.76% are sporadic, and 9.17% are intensifying hot spots. A cluster of cold spots exists over the Atlantic basin while hot spot categories are generally displaced toward the Pacific basin. Studying the CPV centroid characteristics over time and space is important for enhancing understanding in applications such as medium-to-long range weather forecasting, short-range climate prediction, and assessing impacts of atmosphere-ocean teleconnections such as El Niño/Southern Oscillation, the Arctic Oscillation, and the North Atlantic Oscillation.