Changes in North American Atmospheric Circulation and Extreme Weather: Influence of Arctic Amplification and Northern Hemisphere Snow Cover

Changes in North American Atmospheric Circulation and Extreme Weather: Influence of Arctic... AbstractThis study tests the hypothesis that Arctic amplification (AA) of global warming remotely affects middle latitudes by promoting a weaker, wavier atmospheric circulation conducive to extreme weather. The investigation is based on the late-21st century over greater North America (20°-90°N, 50°-160°W) using 40 simulations from the Community Earth System Model’s Large Ensemble, spanning 1920-2100. AA is found to promote regionally varying ridging aloft (500 hPa) with strong seasonal differences reflecting the location of strongest surface thermal forcing. During winter, maximum increases in future geopotential heights are centered over the Arctic Ocean, in conjunction with sea ice loss, but minimum height increases (troughing) occur to the south, over the continental United States. During summer the location of maximum height inflation shifts equatorward, forming an annular band across mid-high latitudes of the entire Northern Hemisphere. This band spans the continents, whose enhanced surface heating is aided by antecedent snow-cover loss and reduced terrestrial heat capacity. Through the thermal wind relationship, mid-tropospheric winds weaken on the equatorward flank of both seasonal ridging anomalies--- mainly over Canada during winter and even more over the continental United States during summer---but strengthen elsewhere to form a dipole anomaly pattern in each season. Changes in circulation waviness, expressed as sinuosity, are inversely correlated with changes in zonal wind speed at nearly all latitudes, both in the projections and as observed during recent decades. Over the central United States during summer, the weaker and wavier flow promotes drying and enhanced heating, thus favoring more intense summer weather. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Climate American Meteorological Society

Changes in North American Atmospheric Circulation and Extreme Weather: Influence of Arctic Amplification and Northern Hemisphere Snow Cover

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Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0442
eISSN
1520-0442
D.O.I.
10.1175/JCLI-D-16-0762.1
Publisher site
See Article on Publisher Site

Abstract

AbstractThis study tests the hypothesis that Arctic amplification (AA) of global warming remotely affects middle latitudes by promoting a weaker, wavier atmospheric circulation conducive to extreme weather. The investigation is based on the late-21st century over greater North America (20°-90°N, 50°-160°W) using 40 simulations from the Community Earth System Model’s Large Ensemble, spanning 1920-2100. AA is found to promote regionally varying ridging aloft (500 hPa) with strong seasonal differences reflecting the location of strongest surface thermal forcing. During winter, maximum increases in future geopotential heights are centered over the Arctic Ocean, in conjunction with sea ice loss, but minimum height increases (troughing) occur to the south, over the continental United States. During summer the location of maximum height inflation shifts equatorward, forming an annular band across mid-high latitudes of the entire Northern Hemisphere. This band spans the continents, whose enhanced surface heating is aided by antecedent snow-cover loss and reduced terrestrial heat capacity. Through the thermal wind relationship, mid-tropospheric winds weaken on the equatorward flank of both seasonal ridging anomalies--- mainly over Canada during winter and even more over the continental United States during summer---but strengthen elsewhere to form a dipole anomaly pattern in each season. Changes in circulation waviness, expressed as sinuosity, are inversely correlated with changes in zonal wind speed at nearly all latitudes, both in the projections and as observed during recent decades. Over the central United States during summer, the weaker and wavier flow promotes drying and enhanced heating, thus favoring more intense summer weather.

Journal

Journal of ClimateAmerican Meteorological Society

Published: Mar 1, 2017

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