Geoscience Reference
In-Depth Information
FIGURE 9.1
Location.of.LTER.sites.used.in.this.chapter..See.Table.9.1.for.full.site.names.
and.guide.to.abbreviations.
.
1..
Southern Oscillation Index (SOI)
.. The. SOI. is. calculated. from. the. differ-
ence.in.barometric.pressure.between.Tahiti,.in.the.central.Paciic.Ocean,.and.
Darwin,.in.the.Australian.Northern.Territory..These.measurements.are.used.
to. construct. a. monthly. index. that. is. widely. used. to. diagnose. the. presence.
of.the.ENSO.phenomenon,.one.of.the.best-known.and.widely.studied.of.all.
atmospheric.teleconnections..ENSO.is.a.pattern.of.pressure.change.across.the.
Paciic.Ocean,.producing.altered.sea.surface.temperatures.and.changes.in.the.
strength. and. persistence. of. the. southern. Paciic. trade. winds.. ENSO. is. cor-
related.with.precipitation.and.temperature.patterns.in.central.North.America.
(Greenland. 1999).. ENSO. events. are. quasi-periodic,. varying. at. time. scales.
ranging. from. 4. to. 7. years. (Kaplan. et. al.. 1998).. SOI. values. used. here. were.
calculated.from.monthly.values.(Trenberth.1984).and.were.obtained.from.the.
National. Weather. Service. Climate. Prediction. Center. (http://www.cpc.ncep.
noaa.gov/data/indices/).
.
2..
North Atlantic Oscillation (NAO).
The.NAO.is.an.oscillation.in.atmospheric.
mass.and.pressure.across.the.North.Atlantic.Ocean..NAO.effects.on.climate.
are. manifest. in. a. number. of. ways.. Low-frequency. oscillation. between. a.
negative.and.positive.phase.are.associated.with.long-term.temperature.and.
precipitation. trends. in. temperature. and. precipitation. in. North. America..
The.NAO.also.manifests.interseasonal.and.interannual.variability.(Hurrell.
