Page 71 - (DK) Ocean - The Definitive Visual Guide
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EL NIÑO AND LA NIÑA 69
La Niña Events low-pressure winds associated with dry
DISCOVERY southeast trade descending air
MONITORING La niña is Spanish for “the little girl.” A La Niña system, positioned conditions and high
farther west
pressure
than normal
event is the reverse of an El Niño event. It is
The tropical Pacific is regularly characterized by unusually cold ocean temperatures
monitored for temperature
changes. The main monitoring in the eastern and central equatorial Pacific, and
methods are the use of satellites, by stronger winds and warmer seas to the north
which measure sea temperatures of Australia. La Niña conditions frequently, but
indirectly from slight variations not always, follow closely on an El Niño.
in the shape of the ocean surface, Like El Niño, La Niña causes increased
and an array of instrumented rainfall in some world regions and
weather buoys.
drought in others. India, Southeast
Asia, and eastern Australia
INSTRUMENTED BUOY
Buoys such as this one, strung in an array are lashed by rains, but
across the equatorial Pacific, are used to make southwestern US generally
regular measurements of water temperature
at varying depths. experiences higher temperatures
and low rainfall. Meanwhile,
northwestern states of the US pool of warm
experience colder, snowier winters. water positioned South
farther west than Equatorial
La Niña is also associated with an normal Current upwelling of
increase in Atlantic hurricane activity. cold, nutrient-
Overall, the effects of a La Niña rich water
event often tend to be strongest sea surface
during Northern Hemisphere winters. cooler than
normal in
eastern Pacific
LA NIÑA PATTERN
During a La Niña event, the area of
low pressure in the western Pacific
is farther west than normal, and the
DROUGHT CONDITIONS pool of warm surface water is also
This water reservoir in Texas pushed west. Unusually cold surface
completely dried up during temperatures develop in the eastern
a severe La Niña-related Pacific as the cold Peru Current
drought that affected the strengthens off South America.
southwestern US in 2011.
PERUVIAN FLOOD INTRODUCTION
Teams of youths work to shepherd
pedestrians across a highway in Peru
flooded by heavy El Niño rains in 1998.
This El Niño ravaged Peru, causing
250,000 people to abandon their homes.
