13.2
Variability of Seasonal-mean Fields Arising from Intraseasonal Variability: Application to the Southern Hemisphere Circulation
Carsten S. Frederiksen, BMRC, Melbourne, VIC, Australia; and X. Zheng
A method for studying patterns of inter-annual variability arising from intra-seasonal variability has been applied to the extratropical wintertime 500hPa geopotential height in the Southern Hemisphere, using data from the NCEP-NCAR reanalysis and a long integration of the Australian Bureau of Meteorology Atmospheric Model (BAM). In particular, the method, using monthly mean data, provides estimates of the inter-annual variance and covariance, in the seasonal mean field, which arise from intra-seasonal variability. These estimates can be used to derive patterns of inter-annual variability associated, therefore, with physical processes that vary significantly within a season, such as, for example, atmospheric blocking, or intra-seasonal oscillations. Removing this intra-seasonal component of inter-annual variability from the total inter-annual variance/covariance, derived from the seasonal mean field, one can define a "residual" component of inter- annual variability. This latter component is more closely related to external forcings and very slowly varying (inter-annual/supra-annual) internal dynamics. The patterns associated with this component are related to well known Southern Hemisphere teleconnections.
Session 13, Tropical-extratropical interactions and teleconnections over the Southern Hemisphere II
Thursday, 27 March 2003, 9:00 AM-11:30 AM
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