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... (Pacific-North American Pattern) AO (Arctic Oscillation) NAO (North Atlantic Oscillation) ... Atmospheric teleconnection Predictions of ENSO (1) ... – PowerPoint PPT presentation

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Title: Presentation schedule:


1
Presentation schedule
  • Dec 2, Wed Dec 4, Friday
  • Sidjak, Rob Hart, Irene
  • Clarke, Steve Jackson, Ian
  • Berry, Kathryn Martin, Sarah
  • Cosway, Katryn Paterson, Graeme
  • Earl, Gareth Priestley, Dan
  • Enns, Deborah deHoog, Neil
  • Talk 10-13 mins. Questions 1-3 mins.
  • (The last Quiz will be in next Friday).

2
Present-Day climate variability
  • Objectives
  • ENSO mode
  • AO and NAO mode
  • PDO

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ENSO MODE
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ENSO
  • A scientific definition of ENSO events When the
    three-month running mean of the SST anomalies in
    the Nino 3.4 region are greater than or equal to
    0.5C, there is a good chance of an El Niño event
    taking place. When the anomalies are smaller than
    or equal to -0.5C, there is a good chance of a
    La Niña event taking place.

9
  • Recognizing El NiñoEl Niño can be seen in Sea
    Surface Temperature in the Equatorial Pacific
    Ocean

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11
  • El Niño Years
  • 1902-1903  1905-1906   1911-1912  1914-1915
    1918-1919  1923-1924   1925-1926  1930-1931
    1932-1933  1939-1940   1941-1942  1951-1952
    1953-1954  1957-1958   1965-1966  1969-1970
    1972-1973  1976-1977   1982-1983  1986-1987
    1991-1992  1994-1995   1997-1998 2002-2003
  • 2006-2007

12
  • Irregularity of ENSO
  •   (1) noise internal to either the atmosphere or
    ocean
  • (2) inherent nonlinearity of the coupled
    atmosphere/ocean system (or in the coupling
    itself)

13
Effect of ENSO on Climate
  • In the Tropics, El Niño episodes are associated
    with increased rainfall across the east-central
    and eastern Pacific and with drier than normal
    conditions over northern Australia, Indonesia and
    the Philippines. Elsewhere, wetter than normal
    conditions tend to be observed 1) during
    December-February (DJF) along coastal Ecuador,
    northwestern Peru, southern Brazil, central
    Argentina, and equatorial eastern Africa,

14
Flooded area in Lakeport, California as a result
of the 1998 El Nino event. (Federal Emergency
Management Agency)
15
Bush fire in Australia as a result of the 1998 El
Niño event. (Photo courtesy of Fred
Hoogervirst/Panos Picture/London)
16
La Niña
El Niño
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18
  • What are the effects of an El Nino on Canada?
  • During the winter of an El Nino event, the air
    temperature tends to be warm over most of Canada,
    with the greatest warming centerd around
    Manitoba-western Ontario. Southern Canada also
    tends to be drier during an El Nino winter.
    Southern British Columbia tends to receive less
    snow.
  • In the case of the cold La Nina event-- the
    opposite of the warm El Nino event-- the coastal
    waters off British Columbia tend to be cool. In a
    La Nina winter, the Canadian air temperature
    (especially west of Quebec) tends to be below
    normal, while the precipitation in southern
    Canada tends to be above normal. Southern British
    Columbia tends to receive more snow.

19
  • Significant impacts of ENSO on Canadian natural
    resources and environment have been documented in
    a variety of areas including water resources,
    agriculture, forestry, fisheries, power
    utilities, coastal zones and other climate
    sensitive sectors of the Canadian economy.
  • (1) the fishery of British Columbia.
  • (2) forestry
  • Hsieh and Tang, 2001. Interannual variability
    of accumulated snow in the Columbia basin,
    British Columbia. Water Resources
  • Res. 37 1753-1760. Hsieh, W.W.,
    B. Tang and E.R. Garnett, 1999. Teleconnections
    between Pacific sea surface temperatures and
  • Canadian prairie wheat yield. Agricul.
    Forest Meteorol. 96 209-217.

20
  • During El Nino, as the sea surface temperature
    (SST) is above normal off B.C., the returning
    Fraser River sockeye salmon (with yearly landed
    value of about 600 million) favor traveling via
    the northern route of Johnstone Strait instead of
    the more commonly used southern route of Juan de
    Fuca Strait. Many fishermen with fishing permits
    on the west coast of Vancouver Island suffered
    heavy losses in 1997 as the sockeye bypassed
    their area.
  • Other impacts occur in forestry. During El Nino,
    temperatures in the BC interior, especially in
    winter, are above normal and summer precipitation
    is typically below normal. Mountain pine beetle
    and forest fires are the two major natural
    disturbance agents in interior forests. A warm
    winter climate is favorable to mountain pine
    beetle survival and has recently led to a severe
    increase in lodgepole pine mortality. At
    the same time fire risk increase under warm and
    dry summer conditions.

21
  • 1997-1998 El Niño induced mild weather helped to
    significantly reduce motor vehicle accidents on
    B.C. roads. The ICBC reported that it enjoyed a
    substantial economic benefit this winter. The
    insurance corporation realized a saving of 3
    million per day owing to the mild winter weather.

22
  • How can sea surface temperatures in the tropical
    Pacific Ocean have any bearing on the weather
    that occurs in northern America?
  • i) Atmospheric circulation
  • ii) Oceanic Circulation
  • iii) Atmospheric teleconnection

23
  • Predictions of ENSO
  • (1) statistical models
  • (2) dynamical models

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28
PNA (Pacific-North American Pattern) AO (Arctic
Oscillation) NAO (North Atlantic Oscillation)
PDO (Pacific Decadal Oscillation)
  • Atmospheric Teleconnection

29
PNA 4 centers Hawaii(20N,160W)North Pacific
Ocean (45N 165W) Alberta (55N 115W) and the
Gulf Coast region of USA (30N 80W)

30
The PNA is associated with a Rossby wave pattern
with centers of action over the Pacific and over
N. America. PNA index ½ Z
(20N,160W)-Z(45N,165W)
Z(55N, 115W)-Z(30N, 85W)
31
  • PNA is one of the most prominent modes of
    low-frequency variability in the Northern
    Hemisphere extratropics. The positive phase of
    the PNA pattern features above-average heights in
    the vicinity of Hawaii and over the intermountain
    region of North America, and below-average
    heights located south
  • of the Aleutian Islands
  • and over the southeastern
  • United States.

32
  • The positive phase of the PNA pattern is
    associated with above-average temperatures over
    western Canada and the extreme western United
    States, and below-average temperatures across the
    south-central and southeastern U.S. The PNA tends
    to have little impact on surface temperature
    variability over North America during summer. The
    associated precipitation anomalies include
    above-average totals in the Gulf
  • of Alaska extending into the
  • Pacific Northwestern United
  • States, and below-average totals
  • over the upper Midwestern
  • United States.
  • Buys Ballot's law

33
  • Although the PNA pattern is a natural internal
    mode of climate variability, it is also strongly
    influenced by the El Niño/ Southern Oscillation
    (ENSO) phenomenon. The positive phase of the PNA
    pattern tends to be associated with Pacific warm
    episodes (El Niño), and the negative phase tends
    to be associated with Pacific cold episodes (La
    Niña).

34
AO is the dominant mode of mean-monthly sea
levelpressure variability over the Northern
Hemisphere withan out-of-phase relation between
the sea level pressure over the Arctic basin and
that at the mid-latitudes (Thompson and Wallace
1998).
AO
35

AO Index
36
  • What is the NAO ?
  • Sometimes AO is also referred to as the North
    Atlantic Oscillation (NAO) due to its strong
    manifestation over the Atlantic sector.
  • A large-scale mode of natural climate
    variability having large impacts on weather and
    climate in the North Atlantic region and
    surrounding continents.

37
  • The NAO is the dominant mode of winter climate
    variability in the North Atlantic region ranging
    from central North America to Europe and much
    into Northern Asia. The NAO is a large scale
    seesaw in atmospheric mass between the
    subtropical high and the polar low. The
    corresponding index varies from year to year, but
    also exhibits a tendency to remain in one phase
    for intervals lasting several years.

38
  • Positive NAO Index The Positive NAO index phase
    shows a stronger than usual subtropical high
    pressure center and a deeper 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

39
  • Negative NAO Index
  • The negative NAO index phase
  • shows a weak subtropical high
  • and a 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 air to northern Europe
  • The US east coast experiences more
  • cold air outbreaks and hence snowy
  • weather conditions.
  • Greenland, however, will have milder
  • winter temperatures

40
  • PDO (Pacific Decadal Oscillation)
  • PDO is a long-term ocean fluctuation of the
    Pacific Ocean. The PDO waxes and wanes
    approximately every 20 to 30 years.

41
Typical wintertime Sea Surface Temperature
(colors),  Sea Level Pressure (contours) and
surface wind stress (arrows) anomaly patterns
during warm and cool phases of PDO  
  • Warm phase Cold phase

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43
  • Percent change in mean catches of four Alaskan
    salmon stocks following major PDO sign changes in
    1947 and 1977.  salmon stock 1947 step 1977 step
  • western Alaska sockeye - 37.2 242.2
  • central Alaska sockeye -33.3 220.4
  • central Alaska pink -38.3 251.9
  • southeast Alaska pink -64.4 208.7
  • Published in the Bulletin of the American
    Meteorological Society
  • 78 1069-1079, 1999.

44
  • Fisheries scientist Steven Hare coined the term
    "Pacific Decadal Oscillation" (PDO) in 1996 while
    researching connections between Alaska salmon
    production cycles and Pacific climate. PDO has
    since been described as a long-lived El Niño-like
    pattern of Pacific climate variability because
    the two climate oscillations have similar spatial
    climate fingerprints, but very different temporal
    behavior.
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