Teleconnections

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Teleconnections

• Teleconnections
• North Atlantic Oscillation (NAO)
• Pacific North American (PNA)
• Chapter 14.2.4

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Teleconnections
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• Two other major teleconnections
• North Atlantic Oscillation (NAO)
• Pacific-North American (PNA) Index

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North Atlantic Oscillation
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• The NAO is defined as the pressure difference
  between the Azores High and the Icelandic Low
• The NAO exhibits seemed to exhibit a 6 10 year
  periodicity in the second half of the twentieth
  century

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North Atlantic Oscillation
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Not in Book
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North Atlantic Oscillation
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• The positive phase of the NAO has below average
  low pressure and above average high pressure
• The negative phase of the NAO has above average
  low pressure and below average high pressure

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North Atlantic Oscillation
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• Both phases of the NAO are associated with
  changes in the intensity and location of the
  polar front jet stream, and patterns of
  temperature and precipitation

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North Atlantic Oscillation
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• Positive phase
• Above-average temperatures in northern Europe and
  the southeast United States
• Above-average precipitation over northern Europe
  and Scandinavia, and below-average precipitation
  over southern and central Europe

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North Atlantic Oscillation
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Not in Book
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North Atlantic Oscillation
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• Negative Phase
• The opposite patterns of temperature and
  precipitation anomalies are often observed

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North Atlantic Oscillation
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• The NAO strongly influences the temperature and
  precipitation patterns of the eastern US and
  Europe

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Pacific-North American Index
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• The PNA is the pressure differences between the
  Aleutian Islands in the Gulf of Alaska, the
  central US-Canadian border, and the Florida
  panhandle
• The PNA index exhibits significant interannual
  variability, with a phase potentially dominating
  for 2 or more years

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Pacific-North American Index
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• A positive PNA index is associated with increased
  meridional flow over the United States
• A negative PNA index is associated with increased
  zonal flow over the United States

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PacificNorth American Index
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Negative Phase
Positive Phase
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Pacific-North American Index
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• Both phases of the PNA index are associated with
  the patterns or temperature and precipitation

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Pacific-North American Index
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• Positive phase
• Below-average temperatures in the southeast US
• Precipitation is increased over the extreme
  southeast US
• Above-average temperatures in the northwestern US
• Reduced precipitation in the northwest United
  States

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Pacific-North American Index
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• Negative phase
• The opposite patterns of temperature and
  precipitation anomalies are often observed

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