The Role of Stationary and Transient Planetary Waves in the Maintenance of Stratospheric Polar Vortex Regimes in Northern Hemisphere Winter |
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| Authors: | LI Qian Hans-F GRAF and CUI Xuefeng |
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| Institution: | Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,School of GeoSciences, University of Edinburgh, Edinburgh, UK,Center for Atmospheric Science, University of Cambridge, Cambridge, UK,State Key Laboratory of Earth Surface Processes and Resource Ecology, College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, School of GeoSciences, University of Edinburgh, Edinburgh, UK |
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| Abstract: | Using 1958--2002 NCEP/NCAR reanalysis data, we investigate stationary and
transient planetary wave propagation and its role in wave--mean flow
interaction which influences the state of the polar vortex (PV) in the
stratosphere in Northern Hemisphere (NH) winter. This is done by analyzing
the Eliassen-Palm (E-P) flux and its divergence. We find that the stationary
and transient waves propagate upward and equatorward in NH winter, with
stronger upward propagation of stationary waves from the troposphere to the
stratosphere, and stronger equatorward propagation of transient waves from
mid-latitudes to the subtropics in the troposphere. Stationary waves exhibit
more upward propagation in the polar stratosphere during the weak polar
vortex regime (WVR) than during the strong polar vortex regime (SVR). On the
other hand, transient waves have more upward propagation during SVR than
during WVR in the subpolar stratosphere, with a domain of low frequency
waves. With different paths of upward propagation, both stationary and
transient waves contribute to the maintenance of the observed stratospheric
PV regimes in NH winter. |
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| Keywords: | stratospheric polar vortex planetary waves stationary transient |
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