Lect 2

Question 1

Southern Oscillation phenomenon

Answer 1

Walker 1923

Pacific Ocean = High air pressure with Indian Ocean = low air pressure

Question 2

SOI

Answer 2

Southern Oscillation Index:

Difference in Air Pressure between Tahiti and Darwin (Aus)

Question 3

Sustained -ve SOI values

Answer 3

Accompanied by EL NIÑO in S.Am:

• decreases Pacific Trade Wind strength
• warming of central/Eastern Trop. Pacific Ocean: West—>East flow
• sea level flattens (rises in W, drops in E)

Question 4

Sustained +ve SOI

Answer 4

Normal conditions:

• normal Walker Circulation
• low pressure over Darwin (and because SOI = +ve; Tahiti = High pressure)

Question 5

Walker Circulation (Normal)

Answer 5

Air circulation (ocean based) that effects the weather;
-result of diff. In surface P/T over the west/east-ern tropical Pacific Ocean:

West=warm and wet (LOW P. System)
Easy=dry and cool (HIGH P. System)
Therefore; surface air East—>West

Atmospheric winds travel West—>East completing the cell

Question 6

El Niño

Answer 6

Weak easterlies = deep thermocline in Eastern Equatorial Pacific Ocean
-warm & humid along S.Am margin

Question 7

La Niña

Answer 7

Strong easterlies = deep thermocline in Western Equatorial Pacific Ocean
-cold & dry S.Am margin

Question 8

ENSO

Answer 8

El Niño-Southern Oscillation

-phenomenon that EN and SOI aren’t independent but linked

Question 9

ENSO Proxies

Answer 9

Tree Rings
Stalagmites
Corals

Question 10

ENSO Variability

Answer 10

• Li et al: Wavelet analysis determine 50-60 periodicity + standard 2-8 year of El Niño
• Delayed Oscillator Hypothesis; positive feedback initiated by E.Pacific warming hits a certain magnitude = Rossby waves travel west, hit Indonesia and reflect as Kelvin Waves—> shift thermocline up

Question 11

NAO

Answer 11

North Atlantic Oscillation:

• Difference in pressure between Azores/Bermuda High and Icelandic Low
• winter phenomenon affecting Europe

Question 12

NAO -ve phase

Answer 12

-Small Azores High
-Westerlies head South to Mediterranean
= wet Med & cold dry N.Eu/US
Implicates Temp Decrease

Question 13

NAO +ve phase

Answer 13

-Large Azores High
-Westerlies head North to N.Europe
= dry Med & mild wet N.Eu/US
Implicates Temp Increase

Question 14

NAO-Extreme Weather Example

Answer 14

Winter of 2010:

• Snowmageddon in US: snowiest Winter on US East Coast record: up to 1m. Places that snow is rare got hit badly (N.Carolina)
• UK barraged by snow

Question 15

NAO Variability

Answer 15

Trouet et al 2009:
Using combination of stalagmites/tree rings from Morocco & Scotland = NAOms concluded that:
Medieval Warm Period = sustained NAO +ve phase that warmed Europe

Question 16

ENSO Global Teleconnection

Answer 16

During El Niño:

• US mid west gets warmer and central/south gets wetter
• S.Europe has warmer & wetter winter