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Influences of the El Nino Southern Oscillation and the Pacific Decadal Oscillation on the Timing of the North American SpringDetrended, modelled first leaf dates for 856 sites across North America for the period 1900-2008 are used to examine how the El Nino 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 Nino 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.
Document ID
20140001049
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
McCabe, Gregory J.
(Geological Survey Denver, CO, United States)
Ault, Toby R.
(Arizona Univ. Tucson, AZ, United States)
Cook, Benjamin I.
(NASA Goddard Inst. for Space Studies New York, NY, United States)
Betancourt, Julio L.
(Geological Survey Tucson, AZ, United States)
Schwartz, Mark D.
(Wisconsin Univ. Milwaukee, WI, United States)
Date Acquired
March 6, 2014
Publication Date
October 1, 2012
Publication Information
Publication: International Journal of Climatology
Volume: 32
Issue: 15
Subject Category
Meteorology And Climatology
Report/Patent Number
GSFC-E-DAA-TN8995
Funding Number(s)
CONTRACT_GRANT: NSF EF-0553768
CONTRACT_GRANT: NSF IOS-0639794
WBS: WBS 509496.02.08.04.24
Distribution Limits
Public
Copyright
Public Use Permitted.
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