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El Nino Teleconnections. Philip Kreycik EPS 131 4/30/04. 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 - PowerPoint PPT Presentation
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El Nino Teleconnections
Philip KreycikEPS 1314/30/04
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
’97-’98 El Niño Beginning to Peak
Fig. From JPL
Walker Circulation
Fig. From theAustralian Bureau of Meteorology
El Niño- what causes it
• We’re 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?
Attempts to Predict and Prepare
Fig. From Natl. Geographic online
Southern Oscillation Index (SOI)
• Oscillation in pressure difference across tropical Pacific– Normalized to the average difference
• + means La Nina
• - means El Niño
Recent SOI Values
Teleconnections- Floods
• Deep Convection- the mechanism
• NW Peruvian Coast– Sechura Desert
• Southern Brazil • Europe• Implications for human health
– Food resources– Disease
Teleconnections- Drought
• Shifting Walker Circulation shifting wet and dry areas
• Africa, India, Polynesia, Australia, New Zealand
Photo from the Royal Society of New Zealand
North American Teleconnections
“Hurricane Linda, spawned during an El Niño, churns northeastward in September 1997. Linda’s 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
Teleconnections- N. American Storms and Rain
Fig. from the NOAA
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
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
ENSO and the N. Pacific Oscillation
• NPO high, El Nino phaseconstructive interference– cold central Pacific, warm East Pacific– Strong effect on N. Am. monsoon
• NPO low, El Nino phasedestructive interference
Some Results
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