Synoptic climatology of the longdistance dispersa

Authors: K L Frank L S Kalkstein B W Geils H W Thistle

Publish Date: 2008/05/20

Volume: 52, Issue: 7, Pages: 641-652

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Abstract

This study developed a methodology to temporally classify large scale upper level atmospheric conditions over North America utilizing a newlydeveloped upper level synoptic classification ULSC Four meteorological variables geopotential height specific humidity and u and vwind components at the 500 hPa level over North America were obtained from the NCEP/NCAR Reanalysis Project dataset for the period 1965–1974 These data were subjected to principal components analysis to standardize and reduce the dataset and then an average linkage clustering algorithm identified groups of observations with similar flow patterns The procedure yielded 16 clusters These flow patterns identified by the ULSC typify all patterns expected to be observed over the study area Additionally the resulting cluster calendar for the period 1965–1974 showed that the clusters are generally temporally continuous Subsequent classification of additional observations through a zscore method produced acceptable results indicating that additional observations may easily be incorporated into the ULSC calendar The ULSC calendar of synoptic conditions can be used to identify situations that lead to periods of extreme weather ie heat waves flooding and droughts and to explore longdistance dispersal of airborne particles and biota across North America

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