Variations of Northern Hemisphere Storm Track and Extratropical Cyclone Activity Associated with the Madden-Julian Oscillation

Variations of Northern Hemisphere Storm Track and Extratropical Cyclone Activity Associated with... AbstractThis study investigates the intraseasonal variations of the Northern Hemispheric storm track associated with the Madden-Julian Oscillation (MJO) during the extended boreal winter (November-April) using 36 years (1979-2014) of ERA-interim reanalysis data. Two methods have been used to diagnose storm track variations.In the first method, the storm track is quantified by the temporal filtered variance of 250-hPa meridional wind (vv250) or mean sea level pressure (pp). The intraseaonal anomalies of vv250 composited for eight MJO phases are characterized by a zonal band of strong positive (or negative) anomalies meandering from the Pacific all the way across North America and the Atlantic into northern Europe, with weaker anomalies of opposite sign at one or both flanks. The results based on pp are consistent with those based on vv250 except larger zonal variations which may be induced by surface topography.In the second method, an objective cyclone tracking scheme has been used to track the extratropical cyclones that comprise the storm track. The MJO-composite anomalies of the “accumulated” cyclone activity, a quantity that includes contributions from both the cyclone frequency and cyclone mean intensity, is very similar to those based on pp. Further analysis demonstrates that major contribution comes from variations in the cyclone frequency.Further analysis suggests that the intraseasonal variations of the storm track can be primarily attributed to the variations of the mean flow that responds to the anomalous MJO convections in the tropics, with possible contribution also from the moisture variations. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Climate American Meteorological Society

Variations of Northern Hemisphere Storm Track and Extratropical Cyclone Activity Associated with the Madden-Julian Oscillation

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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-16-0513.1
Publisher site
See Article on Publisher Site

Abstract

AbstractThis study investigates the intraseasonal variations of the Northern Hemispheric storm track associated with the Madden-Julian Oscillation (MJO) during the extended boreal winter (November-April) using 36 years (1979-2014) of ERA-interim reanalysis data. Two methods have been used to diagnose storm track variations.In the first method, the storm track is quantified by the temporal filtered variance of 250-hPa meridional wind (vv250) or mean sea level pressure (pp). The intraseaonal anomalies of vv250 composited for eight MJO phases are characterized by a zonal band of strong positive (or negative) anomalies meandering from the Pacific all the way across North America and the Atlantic into northern Europe, with weaker anomalies of opposite sign at one or both flanks. The results based on pp are consistent with those based on vv250 except larger zonal variations which may be induced by surface topography.In the second method, an objective cyclone tracking scheme has been used to track the extratropical cyclones that comprise the storm track. The MJO-composite anomalies of the “accumulated” cyclone activity, a quantity that includes contributions from both the cyclone frequency and cyclone mean intensity, is very similar to those based on pp. Further analysis demonstrates that major contribution comes from variations in the cyclone frequency.Further analysis suggests that the intraseasonal variations of the storm track can be primarily attributed to the variations of the mean flow that responds to the anomalous MJO convections in the tropics, with possible contribution also from the moisture variations.

Journal

Journal of ClimateAmerican Meteorological Society

Published: Mar 14, 2017

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