ATS2545 Lecture Notes - Lecture 12: North Atlantic Oscillation, Nios Embedded Processor, Cactus
25 May 2018
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Lecture 12 – Australian hydrology #2
Nature of the Southern Oscillation – basis of ENSO phenomena
• A see-saw of atmospheric pressure across the Pacific Ocean, normally
assessed by comparing Darwin and Tahiti
• When the WPWP (warm pool) off Northern Australia is well developed,
strong uplift is associated with lower atmospheric pressure on a region
represented by Darwin
• This is associated with a compensating subsidence over the E pacific
• When pressure was high in one region, it was low in the other
• The southern Oscillation depicts that the atmosphere is a closed system
o In which uplift in one region must be balanced by subsidence
elsewhere
Global Teleconnections and Hydrology in Australia
• Underling mechanism in which the climate, rainfall (etc) in one region can be
protected from a knowledge of the conditions in some distant region that can
be regarded as a control region
• Many teleconnections including North Atlantic oscillation (NAO) as well as
ENSO
Implications for Rainfall Across Australia
• The normal conditions of low atmospheric pressure centred on Darwin implies
strong convective uplift and relatively high rainfall over parts of Australia
affected by these circumstances
• El Niño conditions imply stronger uplift further E over the pacific than
normal, since the warm ocean surface waters are displaced to the E
o Suggests that in El Niño years, rainfall over affected parts of Australia
will fall below normal
o Plural of El Niño - Los Niño’s
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