Northern Hemisphere circumpolar vortex trends and variability at multiple vertical levels

Authors: Nazla Bushra*, Department of Oceanography and Coastal Sciences, Louisiana State University, Robert V. Rohli, Department of Oceanography and Coastal Sciences, Louisiana State University
Topics: Climatology and Meteorology, Polar Regions, Physical Geography
Keywords: Northern Hemisphere circumpolar vortex, geopotential heights, Rossby waves, time series analysis, polar meteorology, polar climatology, cryosphere
Session Type: Virtual Paper
Day: 4/9/2021
Start / End Time: 3:05 PM / 4:20 PM
Room: Virtual 27
Presentation File: No File Uploaded

The Northern Hemisphere circumpolar vortex (NHCPV)– centered on the north pole– represents the hemispheric-scale, quasi-westerly, extratropical wind belts composed of long (i.e., Rossby) waves which circumnavigate the Earth at altitudes of 5−12 km at a given time. The waves undulate and propagate in response to subtropical upper-level divergence and thermal and orographic forcing, with many impacts on and by the surface environment. This study evaluates the extent to which the area and waviness of the NHCPV are vertically consistent. One-way ANOVA is implemented on the daily-standardized NHCPV area and waviness to test the null hypothesis that no difference exists by vertical level. In addition, long-term (1979─2017) annual and seasonal temporal and cyclical trends of the NHCPV’s area and waviness (represented by a circularity ratio) are identified at the 700-, 500-, 300-, and 200-hPa geopotential height levels, after filtering out complicated daily patterns at lower levels due to topography. Because the CPV is driven primarily by conditions on the periphery (i.e., where the CPV expands/contracts), particularly near the subpolar low-pressure systems which maintain their structure with height, the CPV structure is also hypothesized to remain intact vertically through the troposphere. If this hypothesis is supported, the CPV would therefore respond to warming in a consistent manner vertically, from the 700- to 200-hPa levels. This novel analysis of simultaneous daily variability in NHCPV area and circularity at multiple vertical levels will allow important scientific questions to be explored regarding the equator-pole transfer of energy and its effects on weather and climate events.

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