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The role of the Southern Hemisphere semiannual oscillation in the development of a precursor to central and eastern Pacific Southern Oscillation warm events

Journal Article · · Geophysical Research Letters
DOI:https://doi.org/10.1002/2017GL073832· OSTI ID:1473892
 [1];  [2];  [3]
  1. National Center for Atmospheric Research (NCAR), Boulder, CO (United States); National Center for Atmospheric Research
  2. National Center for Atmospheric Research (NCAR), Boulder, CO (United States)
  3. National Center for Atmospheric Research (NCAR), Boulder, CO (United States); Monash Univ., Melbourne, VIC (Australia). School of Earth, Atmosphere and Environment
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The semiannual oscillation (SAO) is a twice-yearly northward movement (in May-June-July (MJJ) and November-December-January (NDJ)) of the circumpolar trough of sea level pressure (SLP) in the Southern Hemisphere with effects throughout the troposphere. During MJJ the second harmonic of SLP, describing the SAO, has low values of SLP north of 50°S in the subtropical South Pacific, while the first harmonic, which is dominant over the Australian sector, increases to its peak. This once-a-year peak in negative SLP gradients (decreasing to the east) between Australia and the ocean to its east extends to the equatorial Pacific. Southern Oscillation warm events since 1950, with an intensification of this seasonal cycle, have had larger-amplitude SST anomalies in the eastern equatorial Pacific in MJJ and during the following mature phase in NDJ. Weak amplification of the seasonal cycle in MJJ tends to be followed by larger-amplitude SST anomalies in the central equatorial Pacific during NDJ.
Research Organization:
National Center for Atmospheric Research (NCAR), Boulder, CO (United States)
Sponsoring Organization:
National Science Foundation (NSF); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23). Climate and Environmental Sciences Division
Contributing Organization:
National Oceanic and Atmospheric Administration (NOAA), Boulder, CO (United States)
Grant/Contract Number:
FC02-97ER62402
OSTI ID:
1473892
Journal Information:
Geophysical Research Letters, Journal Name: Geophysical Research Letters Journal Issue: 13 Vol. 44; ISSN 0094-8276
Publisher:
American Geophysical UnionCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (2)

The Relationship Between South Pacific Atmospheric Internal Variability and ENSO in the North American Multimodel Ensemble Phase‐II Models journal November 2019
Sustained ocean changes contributed to sudden Antarctic sea ice retreat in late 2016 journal January 2019

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Related Subjects

54 ENVIRONMENTAL SCIENCES
El Nino
seasonal cycle
semiannual oscillation