El Nino Flashcards
what is El Nino associated with?
associated with a reduction in air pressure difference in overlying atmosphere across Pacific (Southern Oscillation) & reduction in strength of trade winds
what is El Nina?
The opposite, la Niña occurs when Eastern Eq. Pac. SSTs are cooler than normal and trade wind strength increases
what is teleconnection?
“when something happens here, something else happens over there”. A linkage between weather changes in widely separated regions of the globe
what is the teleconnection technical definition?
A significant positive or negative correlation in the fluctuations of a field (e.g. temperature; atmospheric pressure) at widely separated points.
what is teleconnection most commonly applied to?
Most commonly applied to variability on monthly and longer timescales, the name refers to the fact that such correlations suggest that information is propagating between the distant points through the atmosphere (or ocean).
how did la Nina teleconnections change in mass?
Changes in mass from early 2010 to mid 2011 from NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites
Drop of 5 mm in global mean sea level due to rain over land
what is the close relationship between temperature and sea surface height anomalies?
El Niño – positive SSH anomaly associated with elevated temperatures
La Niña – negative SSH anomaly associated with cooler temperatures
what does SSh stand for?
sea surface height
how are kelvin waves related to SSH?
Eastward moving Kelvin wave collides with coast and bounces off as westward moving Rossby wave
what happened to El Nino thermocline?
El Niño develops with the eastward-propagating Kelvin wave (model output) - depresses thermocline
what are the kelvin waves renews El Nino?
Elevated sea surface height in east, but not extreme suggests El Niño may be weakening
Then strong sea level anomaly appears northeast of Australia signals start of Kelvin wave
Spreads eastward into central Pacific and reinvigorates El Niño
what is ENSO?
ENSO = El Niño + Southern Oscillation
El Niño indices - based on SST anomalies in the equatorial Pacific
what is southern oscillation indices?
based on air pressure differences between Tahiti and Darwin.
Usually calculated using monthly mean sea level pressure anomalies SOI T-D. reliable since 1935.
what is the TOGA array?
The Tropical Ocean-Global Atmosphere observing system
what is the PDO? is there inter-decadal as well as inter-annual variability?
Fisheries scientist Steven Hare coined the term “Pacific Decadal Oscillation” (PDO) in 1996 while researching connections between Alaska salmon production cycles and Pacific climate
