E kman S piral Cold Water Upwelling Normal Conditions G lobal O cean C urrents Walker Cells Global Average Precipitation AVERAGE JANUARY SEALEVEL PRESSURE Southern Oscillation Tahiti Pressure Darwin Pressure ID: 585683
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Slide1
EL NINOSlide2
E
kman
S
piralSlide3
Cold Water UpwellingSlide4
“Normal” ConditionsSlide5
G
lobal
O
cean
C
urrentsSlide6
Walker CellsSlide7
Global Average PrecipitationSlide8
AVERAGE JANUARY SEA-LEVEL PRESSURE
Southern Oscillation = Tahiti Pressure — Darwin Pressure
Tahiti
DarwinSlide9
EL NINO CONDITIONSSlide10
LA NINA CONDITIONSSlide11Slide12
El
Niño
and the
Southern
Oscillation
(ENSO)
El
Niño:
5 consecutive months of
sea-surface temperatures in region
“Nino 3.4” at least 0.5°C above average
(La Ni
ñ
a: 0.5°c below average)
Tahiti
Darwin
Southern Oscillation:
Tahiti surface
pressure minus Darwin surface pressure
positive = strong easterly trades
negative = weak easterly trades or
westerliesSlide13
Relationship between El Niño and Southern Oscillation
ENSO
=
E
l
N
iño
S
outhern
O
scillationSlide14
ENSO
O
ver
T
ime
1950–2015Slide15
Red = high SSTs
Blue = low SSTs
U
pdate ENSO
T
ime
S
eriesSlide16
ENSO ImpactsSlide17
Kelvin Wave
White/Red areas = elevated sea levelSlide18Slide19
From Gray
During El
Niño events,
North Atlantic
h
urricanes
are less common.Slide20
SOI and North Pacific Hurricanes
Irwin and Davis (1999)
When SOI is negative (El
Niño),
Eastern
Pacific
h
urricanes
are farther from the coast.Slide21
ENSO and Circumpolar Vortex
Frauenfeld and Davis (2000)
During El
Niño,
polar vortex (and jet stream) expands over
the North
Pacific and contracts over western North America.Slide22
SOI and Virginia PrecipitationSlide23
SOI and Virginia Temperatures
(Chap. 10, pp. 280–286)