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Using the NCAR CAM 4 to Confirm SAM’s Modulation of the ENSO Teleconnection to Antarctica and Assess Changes to this Interaction during Various ENSO Flavor Events

Wilson, Aaron Benjamin
http://rave.ohiolink.edu/etdc/view?acc_num=osu1376919626

Abstract Details

2013, Doctor of Philosophy, Ohio State University, Atmospheric Sciences.
The Southern Annular Mode (SAM) has long been acknowledged as the dominant mode of atmospheric circulation variability in the mid- and high latitudes of the Southern Hemisphere (SH). The largest mode of global atmospheric circulation variability on interannual timescales is the El Niño-Southern Oscillation (ENSO). Studies over the last decade have shown that SAM reinforces circulation anomalies caused by ENSO variability in the high-southern latitudes through transient eddy processes and significant changes to the position and strength of the jet streams. Research on ENSO flavors has recently emerged as well, as scientists use the location of the tropical Pacific sea surface temperature (SST) anomalies to classify ENSO events as Eastern Pacific (EP) or Central Pacific (CP). This study combines previous research on the ENSO-SAM interaction with ENSO flavors to document changes to atmospheric circulation in the SH, particularly at high latitudes, which have received little attention in the discussion of ENSO flavors. A series of global climate model simulations using the National Center for Atmospheric Research Community Atmosphere Model (CAM) version 4 strongly confirm SAM's active modulation of the ENSO teleconnection to Antarctica regardless of ENSO flavor. A comparison between idealized simulations of strong CP and EP events verifies previous research showing increased blocking over the Australian continent and a southward shift in the sub-tropical jet (STJ) across the eastern Pacific basin during CP events. More importantly for the high-southern latitudes, a westward shift in the upper- level divergence in the tropical Pacific causes the Pacific-South American (PSA) stationary wave pattern to shift toward the west as well. These changes to the Rossby wave source region lead to the downstream effects including decreased blocking in the Amundsen-Bellingshausen Seas region as anticyclonic flow becomes established in the South Central Pacific. The atmospheric circulation changes lead to modifications of heat and momentum fluxes due to stationary eddies across the South Pacific and weaken the ENSO-Antarctic Dipole relationship. CAM demonstrates these changes to atmospheric circulation more robustly when results are filtered for the observed SAM phase, proving that high-latitude atmospheric circulation variability in the South Pacific is induced by both tropical and high-latitude forcing.
David Bromwich, Ph.D. (Advisor)
Jeffrey Rogers, Ph.D. (Committee Member)
Jay Hobgood, Ph.D. (Committee Member)
Jialin Lin, Ph.D. (Committee Member)
Robert Burkholder, Ph.D. (Committee Member)
296 p.
Atmospheric Sciences; Climate Change
Southern Annular Mode; SAM; El Nino-Southern Oscillation; ENSO; ENSO flavors; Central Pacific ENSO; Southern Hemisphere Atmospheric Circulation Variability

Recommended Citations

Citations

  • Wilson, A. B. (2013). Using the NCAR CAM 4 to Confirm SAM’s Modulation of the ENSO Teleconnection to Antarctica and Assess Changes to this Interaction during Various ENSO Flavor Events [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1376919626

    APA Style (7th edition)

  • Wilson, Aaron. Using the NCAR CAM 4 to Confirm SAM’s Modulation of the ENSO Teleconnection to Antarctica and Assess Changes to this Interaction during Various ENSO Flavor Events. 2013. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1376919626.

    MLA Style (8th edition)

  • Wilson, Aaron. "Using the NCAR CAM 4 to Confirm SAM’s Modulation of the ENSO Teleconnection to Antarctica and Assess Changes to this Interaction during Various ENSO Flavor Events." Doctoral dissertation, Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1376919626

    Chicago Manual of Style (17th edition)

osu1376919626
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© 2013, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.