A GIS-Intensive Iterative Procedure for Delineating the Tropospheric Circumpolar Vortex

Authors: Nazla Bushra*, Department of Oceanography & Coastal Sciences, College of the Coast and Environment, Louisiana State University, Robert V. Rohli, Department of Oceanography & Coastal Sciences, College of the Coast and Environment, Louisiana State University
Topics: Climatology and Meteorology
Keywords: Tropospheric Circumpolar Vortex, Atmospheric Circulation Variability, Atmospheric Teleconnections, Polar Front Jet Stream
Session Type: Paper
Day: 4/5/2019
Start / End Time: 8:00 AM / 9:40 AM
Room: Marshall East, Marriott, Mezzanine Level
Presentation File: No File Uploaded

This broad-scale, steering atmospheric circulation, known more formally as the tropospheric circumpolar vortex (TCPV), is an important driver of environmental processes. The area and circularity of the Northern Hemisphere’s TCPV (NHTCPV) are analyzed here using a data-intensive, GIScience-based new technique, using daily data, but averaged at monthly scale to be contrasted with those identified in previous research for the overlapping period of record (1979−2001). In this method, the steepest gradient of atmospheric mass (i.e., steepest 500 hPa geopotential height gradient) at 2.5˚ increment of longitude globally were identified to calculate NHTCPV area and circularity ratio (Rc), instead of using the predetermined isohypes at 500 level as has been recommended in previous research. Accuracy of representation of the NHTCPV is assessed through correlations to air-sea teleconnections that are known to be related to broad-scale, extratropical steering circulation. Results suggest that the new method improves the delineation of area and circularity of the 500-hPa manifestation of the NHCPV. Thus, representing the atmosphere with a pre-determined isohypse of atmospheric geopotential height may represent the weather system less accurately, as the TCPV relies on the relative position of atmospheric pressure and mass gradients, which may occur at different isohypses across both space and time. This finding is important because the amplitudes and positions of the undulations in the broad-scale flow exert the most important impacts on weather variability at both low- and high-frequency time periods. Such work will allow for identification of a signal of global climatic change in the upper-level flow.

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