22. Modes of Climate Variability & Sea Level Changes

Question 1

Why is it important to study climate variability?

Answer 1

without an understanding of “baseline”, we have no way to understand how current observations of our climate fit into the bigger picture (eg is the climate actually changing?)

Question 2

explain the following in terms of studying climate variability

mean=

anomaly=

Answer 2

mean= serves as a reference for studying the variability

anomaly= difference between the current state of the climate system and the mean

Question 3

T/F

Variations in the climate are random

Answer 3

false

Variations in the climate are NOT random
- clearly organized in a pattern/ structure

Question 4

Explain what geopotential height is

Answer 4

• vertical coordinate referenced to earth’s mean sea level
• height of a pressure sfc above mean sea level
• heights are lower in cold air masses and higher in warm air masse s

Question 5

Geopotential heights are lower in cold air masses and higher in warm air masses. Explain why

Answer 5

Since cold air is more dense that warm air, it causes pressure surfaces to be lower in colder air masses, while less dense, warmer air allows the pressure surfaces to be higher

Question 6

Arctic Oscillation (AO)=

Answer 6

a climate index showing the state of the atmospheric circulation over the Arctic

• diff in patterns of pressure b.w the Arctic and the N. mid latitudes

Question 7

What happens during the positive Arctic Oscillation phase?

Answer 7

polar circulation is stronger which forces cold air/ storms to remain further north

• below average geopotential heights are associated with a strong polar vortex

Question 8

Below avg geopotential heights are associated with:

Answer 8

a strong polar vortex

Question 9

During a positive AO phase, where do ocean storms go?

What regions of the world will be wet vs dry?

Answer 9

farther north!

Wet: Alaska, Scotland, Scandinavia

Dry: West N. America & Mediterranean

Question 10

What happens during a negative Arctic Oscillation Phase?

Answer 10

the polar low pressure system (polar vortex) is weaker (so the pressure is higher than usual), which weakens the upper level winds (westerlies)

Therefore, cold arctic air pushes further south

• above average geopotential heights are associated with weak polar vortex

Question 11

above average geopotential heights are associated with :

Answer 11

weak polar vortex

Question 12

During a negative AO phase, what will the pressures be like in the Arctic? Mid-Lat?

Answer 12

Arctic= high pressure

Mid lat= low pressure

Question 13

What kind of weather would each location experience during a strongly negative AO phase?
- High lat
- temperate regions

Answer 13

high lat= warm weather

temperate regions= cold, stormy weather (sucks because this is where people live)

Question 14

The Arctic Oscillation and the North Atlantic Oscillation (NAO) are two separate indices that both:
(give 2)

Answer 14

• measure varying pressure gradients in the N lats
• Results impact temp and storm tracks

Question 15

There are 2 pressure centers in the North Atlantic:

Answer 15

• low pressure center near Iceland
• high pressure center near Azores (Eastern Atlantic Ocean)

*location of the pressure centers can move around seasonally; so other locations have been used to measure this index

Question 16

T/F

The strength of the N. Atlantic’s pressure centers alters the jet stream, which affects temp and precip

Answer 16

true

Question 17

What happens during the positive NAO phase?

Answer 17

• Icelandic low is strengthened
• Azores high is strengthened

Pressure gradient is increased (greater diff b/w the low & high pressure)

The westerlies increase in strength —> cold air moves off N. America

Question 18

In a positive NAO phase, what are the relative geopotential heights over western Atlantic vs Icelandic region?

Answer 18

• above average heights over the western atlantic
• below average heights over the icelandic region

Question 19

What would temps be like in the eastern US during a positive NAO phase?

Answer 19

above avg temps as the strong westerlies push the cold air away

Question 20

Explain what happens during a negative NAO phase

Answer 20

• Icelandic low weakens
• Azores high weakens

Decrease in pressure gradient across the N Atlantic

• Weakening of the westerlies: cold air builds up over Canada & can move south