Presentation schedule:

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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).

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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.

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

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• 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

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• 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)

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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,

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Flooded area in Lakeport, California as a result
of the 1998 El Nino event. (Federal Emergency
Management Agency)
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Bush fire in Australia as a result of the 1998 El
Niño event. (Photo courtesy of Fred
Hoogervirst/Panos Picture/London)
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La Niña
El Niño
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• 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.

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• 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.

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• 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.

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• 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.

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• 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

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

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PNA (Pacific-North American Pattern) AO (Arctic
Oscillation) NAO (North Atlantic Oscillation)
PDO (Pacific Decadal Oscillation)

• Atmospheric Teleconnection

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

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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)
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• 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.

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• 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

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• 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).

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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
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AO Index
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• 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.

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• 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.

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• 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

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• 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

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• 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.

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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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• 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.

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• 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.