NOTES AND CORRESPONDENCE Comments on ‘‘Northern Hemisphere Teleconnection Patterns during Extreme Phases of the Zonal-Mean Circulation’’
In a recent article published in this journal, Ting et al. (1996) documented the three-dimensional structure of the stationary wave response to a distinctive mode of variability of the zonally averaged basic state: a me-ridional ‘‘see-saw’ ’ in zonal momentum represented by the algebraic difference...
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| Format: | Text |
| Language: | English |
| Published: |
1999
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.623.4812 http://www.atmos.colostate.edu/ao/ThompsonPapers/WallaceThompsonFang.pdf |
| Summary: | In a recent article published in this journal, Ting et al. (1996) documented the three-dimensional structure of the stationary wave response to a distinctive mode of variability of the zonally averaged basic state: a me-ridional ‘‘see-saw’ ’ in zonal momentum represented by the algebraic difference between the zonal-mean, zonal (geostrophic) wind at 558 and 358N. This particular choice of index was motivated by statistics derived from a suite of experiments with a linear baroclinic stationary wave model and prior analyses of observational data by Branstator (1984) and Kidson (1985). Here we relate the mode of variability that they examined to the ‘‘Arctic Oscillation’ ’ (AO; Thompson and Wallace 1998, here-after denoted TW98) and reflect upon the broader im-plications of their findings. In making this comparison we make use of monthly rather than seasonal mean fields because they capture more faithfully the structure of the AO and they afford a larger sample size. As in TW98, the AO is defined as the leading principal component of the (unstandardized) monthly sea level pressure anomaly field poleward of 208N based on the sea level pressure analyses of Tren-berth and Paolino (1981). The 58 3 58 lat–long gridded data were weighted by the square root of cosine of lat-itude. Our analysis of monthly mean 500-hPa height and zonal wind fields is based on the National Centers for Environmental Prediction–National Center for At-mospheric Research reanalyses (Kalnay et al. 1996) for the 119 winter months (DJF) beginning with January 1958 and ending with February 1997, obtained from the |
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