Geoscience Reference
In-Depth Information
a column of warm, moist air. h is column bulges into the atmosphere for six
to ten miles, where it remains like a giant boulder in a stream—an obstacle
that atmospheric winds and storm systems must move around—and so inl u-
ences the strength and location of jet streams over the northern and southern
Pacii c Oceans.
h e copious amounts of evaporation from this warm water also spawn
large storms that are carried by westerly winds into northern Mexico and the
southwestern United States. h e deluges, l oods, and mudslides experienced
in the North American Southwest are ot en mirrored by opposite but equally
tragic events in distant regions thousands of miles away, on the western side
of the Pacii c Ocean. h ere, the surrounding ocean waters are cooler than
usual, with less evaporation and less rain. Droughts, forest i res, and dust
storms ot en occur simultaneously in places such as Australia and Indonesia.
h e Pacii c Northwest also experiences drier than normal conditions during
an El Niño event.
La Niña Episodes
If El Niño conditions represent a disruption of what we think of as the normal
climate state, La Niña episodes occur when “normal” conditions go into “over-
drive.” h e trade winds blow even harder across the Pacii c Ocean, forming an
even larger warm pool in the western Pacii c and leading to an increased upwell-
ing of cold surface waters in the eastern Pacii c. In the western Pacii c, evapo-
rated water of this vast warm pool rises high into the atmosphere, forming
towering clouds that drench the tropical regions over northern Australia and
Indonesia. Across the Pacii c, in Peru and in the North American Southwest,
the unusually cool waters of the eastern Pacii c bring severe drought.
ENSO and Precipitation in the West
Because the oceans provide the water and energy for most of the storms
on Earth, the shit ing of warm surface waters to the central and eastern
Pacii c during El Niño ultimately alters precipitation patterns across much
of the globe by atmospheric teleconnections (or long-distance relationships
between weather patterns). For example, droughts in Australia, Indonesia,
southern Africa, southern India, Spain, and Portugal ot en occur at the same
time as deluges and l oods in Peru, the Mississippi River Basin, and Western
Europe. In the American West, the Southwest normally experiences deluges
