Natural Variability Flashcards
What kind of system is climate?
Complex coupled system (ocean and atmosphere)
How is a double pendulum a good example for our climate?
Climate can be predicted but weather is chaotic
What is weather noise?
Entirely random differences in average weather (no pattern)
What is internal climate variability?
Long-term atmospheric dynamical variations (often repetitive)
What causes variability?
Complex coupled system, weather noise, internal climate variability and ocean-atmosphere interactions
What is a natural mode of variability?
Internal climate variability that follows persistent patterns that repeat. It is characterized by teleconnections e.g ENSO and NAO
On what period do natural modes occur?
Years to decades
Why are natural modes important?
- Control regional weather variability
- Impact of agriculture, water resources, fishing
- Affected by climate change?
- Long term changes to modes could amplify climate change /be mistaken for climate change
Where do we measure the NAO from?
The Azores and Iceland
What are conditions like during a positive NAO phase?
- drier over Europe
- wet conditions moved northward
Case study of the strong NAO winter- when was it? what was it called?
The Big Freeze of 2009-2010 in the UK
The NAO of 2009 caused the coldest temperatures since …
1978/79
The NAO of 2009: how low did temperatures reach?
-22.3ºC
The NAO of 2009: What were some of the impacts?
- roads closed
- trains halted
- flights disrupted
- water pipes froze and burst
- 1/3 more gas used
- 25 direct deaths
Why is it important to predict the NAO for the UK?
So we can plan accordingly … e.g. grit roads
What are the changes in climate associated with NAO variations?
-strengthened westerlies
-milder European winters
-sever winters in Canada and NW Atlantic
-regional precipitation changes
-
How do we westerlies change during a positive NAO?
Strengthened westerlies from surface to the lower stratoshpere
How do winters change during positive NAO?
Milder winters in Europe and more severe winters in Canada and NW Atlantic
How does precipitation change during a positive NAO?
Pronounced regional changes … glacier advance in Northern Europe and retreat of Alpine glaciers
Where does sea ice cover change during a positive NAO?
Over the Labrador and Greenland seas
Where does the Met Office no longer publish their NAO forecast?
Loss of public trust … however the overall prediction is good but some years it is off significantly
When does the Met Office publish their results?
If they are very confident in their prediction
What % of inter annual temperature variation anomalies in the N hem over the last 60 years are due to NAO variations?
31%
What is NAO likely driven by?
Decadal variations in Atlantic Ocean temperature which may change in a future climate
What is MEI?
Multivariate ENSO index
What observations is MEI based off?
6 observations over the tropical Pacific …
- Sea level pressure
- zonal and meridional components of surface wind
- sea surface temperature
- surface air temperature
- total cloudiness fraction of the sky
What is ENSO an example of?
- Natural variability
- A coupled system (ocean and atmosphere)
What is a distinct feature of coupled non-linear systems?
Chaos
Is the climate chaotic?
Climate change is not chaotic BUT aspects of the system is … weather and internal climate variability
What are pressure differences like during a positive NAO phase?
Pressure difference between The Azores and Iceland is greater than normal
