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GEOPHYSICAL RESEARCH LETTERS, VOL. 30, NO. 3, 1119, doi:10.1029/2002GL015926, 2003

Potential vorticity intrusion index and climate variability of surface temperature

Ming Cai

Department of Meteorology, University of Maryland, College Park, MD, USA


Abstract

This paper proposes a potential vorticity intrusion index (denoted as PVI) as an alternative diagnostic tool to study the observed climate variability/trend of the surface temperature. The PVI index measures the percentage area of upper lever PV intrusion in the extratropics at any given time. More (fewer) outbreaks of extreme cold surface air temperature in high latitudes take place when the PVI index is high (low). The interannual variability of the PVI index exhibits a strong QBO- like signal. The high (low) PVI index prevails when the equatorial zonal mean zonal wind at 50 hPa is easterly (westerly). The probability distribution map of PV intrusion activities shows a shift of the preferred regions of frontogenesis from the oceans to the continents when the PVI index is high. This explains directly why more extreme cold events are observed over the northern Eurasian and Northern America continents when the PVI index is high, or the QBO is in the easterly phase.

Published 6 February 2003.

Index Terms: 1620 Global Change: Climate dynamics (3309); 3364 Meteorology and Atmospheric Dynamics: Synoptic-scale meteorology.

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Citation: Cai, M. (2003), Potential vorticity intrusion index and climate variability of surface temperature, Geophys. Res. Lett., 30(3), 1119, doi:10.1029/2002GL015926.