03 May 2017

Impact and recent trends of mid-latitude extreme wave events

Researchers develop a new method to detect events of large meandering of the jet stream and highlight a lack of hemispheric-wide trends in recent decades.

Science

This study uses a new method to characterize and detect events of large meandering of the tropospheric jet in the Northern Hemisphere using observations. Wave events, and their associated temperature extremes, did not become more frequent in recent decades, except for an increase in the frequency of events affecting East Asia.

Impact

Some recent studies have claimed a connection between the accelerated warming of the high latitudes, referred to as Arctic Amplification, and the enhanced meandering of the jet stream. This work brings more evidence to dispel these claims of a recent hemispheric-wide amplification of the jet’s meanders.

Summary

A new algorithm based on the concept of local wave activity is applied on the 500-hPa geopotential height field to detect events of persistent large wave activity in the Northern Hemisphere. The method identifies events of amplified atmospheric ridge over Europe and Alaska and amplified trough over East Asia and Northeastern Canada. Composites reveal that wave events result from the constructive interference of stationary waves and synoptic-scale systems. They are accompanied by warm or cold temperature extremes depending on the anticyclonic or cyclonic nature of the events.  Trends in the frequency of wave events indicate that only cyclonic wave events and the associated cold extremes affecting East Asia have become more frequent in recent decades.

 

Contact
Gang Chen
University of California Los Angeles (UCLA)
Publications
Martineau, P., Chen, G. & Burrows, D. "Wave events: climatology, trends, and relationship to Northern Hemisphere winter blocking and weather extremes." Journal of Climate (2017). [10.1175/JCLI-D-16-0692.1].