Comparison of 700-hPa NCEP-R1 and AMIP-R2 Wind Patterns over the Continental United States Using Cluster Analysis

Clustering techniques are adapted to facilitate the comparison of gridded 700-hPa wind flow patterns spanning the continental United States. A recent decade (1985–94) of wind component data has been extracted from two widely used reanalysis datasets: NCEP-R1 and the NCEP–Department of Energy (DOE) A...

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Veröffentlicht in:Journal of applied meteorology (1988) 2007-11, Vol.46 (11), p.1744-1758
Hauptverfasser: Cooter, Ellen J., Swall, Jenise, Gilliam, Robert
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Sprache:eng
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Zusammenfassung:Clustering techniques are adapted to facilitate the comparison of gridded 700-hPa wind flow patterns spanning the continental United States. A recent decade (1985–94) of wind component data has been extracted from two widely used reanalysis datasets: NCEP-R1 and the NCEP–Department of Energy (DOE) Atmospheric Model Intercomparison Project, phase two (AMIP-R2). Metrics and measures are identified that facilitate the identification and comparison of large-scale wind flow. Comparison of the cluster results reveals dominant wind patterns common to both datasets as well as three types of reanalysis model differences: 1) relatively minor numerical differences; 2) differences produced by model corrections or parameterization changes, such as snow mask, snow depth, and moisture flux; and 3) systematic differences, such as orography, overocean radiation fluxes, and overocean data assimilation. A second analysis examines the frequency of 700-hPa wind patterns associated with key ozone-season (May–September) synoptic settings. Association of 1990–94 daily maximum 1-h ozone levels with these patterns across the United States follows documented meteorological dependencies. Above-average ozone levels in the Midwest and mid-Atlantic are associated with transitional anticyclone and easterly flow synoptic patterns (39.2% of ozone-season days) while above-average ozone levels across the southern United States are associated with the westward extension of the Bermuda high circulation (14.8% of ozone-season days). Below-average ozone levels throughout most of the eastern United States are associated with frontal passages and migratory anticyclones (29.6% of ozone-season days).
ISSN:1558-8424
0894-8763
1558-8432
1520-0450
DOI:10.1175/2007JAMC1527.1