Influences of the El Niño Southern Oscillation and the Pacific Decadal Oscillation on the timing of the North American spring

International Journal of Climatology
By: , and 

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Abstract

Detrended, modelled first leaf dates for 856 sites across North America for the period 1900–2008 are used to examine how the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) separately and together might influence the timing of spring. Although spring (mean March through April) ENSO and PDO signals are apparent in first leaf dates, the signals are not statistically significant (at a 95% confidence level (p < 0.05)) for most sites. The most significant ENSO/PDO signal in first leaf dates occurs for El Niño and positive PDO conditions. An analysis of the spatial distributions of first leaf dates for separate and combined ENSO/PDO conditions features a northwest–southeast dipole that is significantly (at p < 0.05) different than the distributions for neutral conditions. The nature of the teleconnection between Pacific SST's and first leaf dates is evident in comparable composites for detrended sea level pressure (SLP) in the spring months. During positive ENSO/PDO, there is an anomalous flow of warm air from the southwestern US into the northwestern US and an anomalous northeasterly flow of cold air from polar regions into the eastern and southeastern US. These flow patterns are reversed during negative ENSO/PDO. Although the magnitudes of first leaf date departures are not necessarily significantly related to ENSO and PDO, the spatial patterns of departures are significantly related to ENSO and PDO. These significant relations and the long-lived persistence of SSTs provide a potential tool for forecasting the tendencies for first leaf dates to be early or late.

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Publication type Article
Publication Subtype Journal Article
Title Influences of the El Niño Southern Oscillation and the Pacific Decadal Oscillation on the timing of the North American spring
Series title International Journal of Climatology
DOI 10.1002/joc.3400
Volume 32
Year Published 2012
Language English
Publisher Royal Meteorological Society
Contributing office(s) National Research Program - Central Branch
Description 10 p.
First page 2301
Last page 2310
Country Canada, United States
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