El Nino Teleconnections

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El Nino Teleconnections

Philip Kreycik EPS 131 4/30/04
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El Niño - What it is

• Periodic anomaly in climate conditions
• Irregular period
• Centered in Tropical Pacific
• Local SST changes, surface pressure change
• Local and Global consequences
• South American floods
• African droughts
• North American rains

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97-98 El Niño Beginning to Peak
Fig. From JPL
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Walker Circulation
Fig. From the Australian Bureau of Meteorology
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El Niño- what causes it

• Were still uncertain
• Atmosphere is a chaotic system
• Difficult to sort out causes and effects
• Pressure seems to be the driving force
• Slackening of trade winds impacts temp. profile
  in ocean
• But what causes changes in the trans-Pacific
  pressure gradient?

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Attempts to Predict and Prepare
Fig. From Natl. Geographic online
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Southern Oscillation Index (SOI)

• Oscillation in pressure difference across
  tropical Pacific
• Normalized to the average difference
• means La Nina
• - means El Niño

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Recent SOI Values
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Teleconnections- Floods

• Deep Convection- the mechanism
• NW Peruvian Coast
• Sechura Desert
• Southern Brazil
• Europe
• Implications for human health
• Food resources
• Disease

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Teleconnections- Drought

• Shifting Walker Circulation? shifting wet and dry
  areas
• Africa, India, Polynesia, Australia, New Zealand

Photo from the Royal Society of New Zealand
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North American Teleconnections
Hurricane Linda, spawned during an El Niño,
churns northeastward in September 1997. Lindas
185-mile-an-hour 298-kilometer-an-hour winds
made it one of the strongest eastern Pacific
storms ever recorded
Photo and caption from Natl. Geographic
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Teleconnections- N. American Storms and Rain
Fig. from the NOAA
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North American Monsoon

• Christopher Castro et al. The Relationship of
  the N. Am. Monsoon to Tropical and N. Pacific SST
  as Revealed by Observational Analyses
• Highly variable period of wet weather
• Short bursts of intense precipitation

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Western US Sensitivity to ENSO

• Not as simple as the NOAA diagram makes it seem!
• Dependence on several oscillating systems
• ENSO
• NPO
• Others
• Relative phases

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ENSO and the N. Pacific Oscillation

• NPO high, El Nino phase?constructive interference
• cold central Pacific, warm East Pacific
• Strong effect on N. Am. monsoon
• NPO low, El Nino phase?destructive interference

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Some Results
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Final conclusion of the study

• Moisture drawn in from Gulf of Mexico
• Low pressure displaced to lower lat. in El Nino
• Circulation around pressure system
• Predictive power still leaves something to be
  desired