Transcript Part-3

Climate Impacts
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Discussion: What economic impacts does ENSO
have?
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What can we say about ENSO and global climate
change?
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Are there other phenomena similar to ENSO?
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Can we predict ENSO?
General Circulation
The surface pressure
• Northern
Winter
(January)
• High over
Land,
Low over
Ocean
What is the North Atlantic Oscillation ?
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A sea saw of atmospheric mass which alternates
between the polar and subtropical regions.
Changes in the mass and pressure fields lead to
variability in the strength and pathway of storm
systems crossing the Atlantic from the US East
coast to Europe.
The NAO is most noticeable during the winter
season (November - April) with maximum
amplitude and persistence in the Atlantic sector.
The North Atlantic Oscillation Index
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An Index can be constructed that represents the phase of the NAO.
Most commonly the NAO index is based on the surface pressure
(SLP) difference between the Subtropical (Azores) high and the
Subpolar (Island) low.
Very often the pressure readings from two stations one on Iceland
and the other either the Azores, Lisbon or Gibraltar are used to
construct the NAO index. The twice daily reading are averaged from
November through March and the difference in then the winter
NAO index.
The North Atlantic Oscillation Index
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The NAO index shows large variations from year to year. This
interannual signal was especially strong during the end of the 19th
century.
Sometimes the NAO index stays in one phase phase for several
years in a row. This decadal variability was quite strong at the
beginning and end of the 20th century.
One might also interpret the recent 30 years as a trend in the NAO
index possibly linked to "global warming".
The positive NAO index phase
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The positive NAO index phase
shows a stronger than usual
subtropical high pressure center
and a deep than normal
Icelandic low.
The increased pressure
difference results in more and
stronger winter storms crossing
the Atlantic Ocean on a more
northerly track.
This results in warm and wet
winters in Europe and in cold
and dry winters in northern
Canada and Greenland.
The eastern US experiences
mild and wet winter conditions.
The negative NAO index phase
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The negative NAO index phase
shows a weak subtropical high
and weak Icelandic low.
The reduced pressure gradient
results in fewer and weaker
winter storms crossing on a
more west-east pathway.
They bring moist air into the
Mediterranean and cold weather
to northern Europe.
The US east cost experiences
more cold air outbreaks and
hence snowy winter conditions.
Greenland, however, will have
milder winter temperatures.
Impacts of the NAO
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Impacts of the NAO
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Us East Coast Impacts of the NAO
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The US East coast experiences
milder winter conditions during
a positive NAO index phase.
The amount of snow cover is
reduced.
Warmer than usual ocean
temperatures cause more
frequent occurrence of "red
tides" in the summer.
Colder than usual tropical ocean
temperatures reduce the number
of hurricanes in the following
summer.
Cold ocean temperatures in the
spawning grounds over the
Grand Banks cause less cod
reproduction.
Impacts of the NAO in Europe
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Northern Europe experiences
mild and wet winter during the
positive NAO index phase.
This has dramatic consequences
for hydro-electric power
generation and heating oil
consumption.
South-Eastern Europe receives
less rain and hence causes
significant problems with
drinking water supply and
reduced stream flow volume in
the Middle East.
Harvest yield of grapes and
olives have been shown to
depend significantly on the
NAO.
NAO and Energy in Norway
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Norway experience cold
winters during a negative
NAO phase.
Heating Oil consumption in
Norway varies by 30% in good
(anti) correlation with the NAO.
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Correlation with precipitation
results in variability in
hydropower generation.
NAO and
Energy in
Norway
Norway gets 99% of
its electricity from
hydropower
Sweden get 50%
from hydropower,
50% from nuclear
energy
What happens if the
rain fall varies?
NAO and
Energy in
Norway
In Norway export and
import of energy is
relatively new.
An open trade market
has been established
(Nord Pool)
How will the price
change with climate
change?
NAO and
Energy in
Norway
There is an
amazing
correlation
between the price
of energy and
water reservoir
level which
varies due to
changes in rain
fall.
NAO and Water Resources in Turkey
and the Middle East
Precipitation in Turkey is well
correlated with the NAO.
As a result spring stream flow
in the Euphrates River varies
by about 50% with the NAO.
An upward trend in the NAO
will lead to drought
conditions in the Middle
East.
Climate and Society
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Precipitation
Temperature
CO2 and other gases
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Energy
Food
Health
Population dynamics