Page 95 - The World About Us

Malawi floods
1.1.1
1.1.1
2.3.6
2.2.3

The La Niña event

A La Niña event, whilst the opposite of El Niño
(the name means 'li le girl' for this reason),
appears as an exaggerated version of the
neutral phase, with a cooling of the waters
in the central and eastern Pacific. The
south-easterly Trade Winds become
stronger than normal bringing
warm, moisture-laden air and
heavy rainfall to the western
Pacific, while reducing it over
the central Pacific region.
Australia and Indonesia may
experience flooding and India
may receive a we er than Fig.253 The south and central Pacific during the La Niña phase of ENSO.
average monsoon.
Global impacts of El Niño Global impacts of La Niña

Thunderstorms and Drought condi ons in Heavier than normal Reduced rainfall in
flooding in Peru and Southern Africa, as rainfall over eastern southern Brazil and
Ecuador. well as in Australia Australia, Indonesia central Argen na.
and South East Asia. and the Philippines. Drought in coastal areas of
Fish shoals die in Peru and Chile.
warm seas off South Increased hurricanes Heavier rain in
America’s coast. in the central and northern Brazil and Drier than normal in
eastern Pacific basin. central Andes. the USA’s Gulf states.
Heavier than normal Heavier monsoon in Fewer hurricanes in
rains in East Africa. Increased strength to
northern India with the central and
the cyclones of the
We er than normal risk of flooding. eastern Pacific basin.
western Pacific.
on Gulf Coast of USA. Torren al rain and Increased hurricanes
Reduced hurricane flooding in Southern in the Atlan c and
Drier than normal in
ac vity in the Atlan c Africa. Caribbean Sea.
Rocky mountains and and Caribbean.
Pacific Northwest.
Fig.254 El Niño and La Niña years and strengths since 1979-80
El Niño years since 1979-80 La Niña years since 1979-80
Weak Moderate Strong Very Strong Weak Moderate Strong 1. What is a cyclone,
typhoon or hurricane? (2)
1979-80 1986-87 1987-88 1982-83 1983-84 1995-96 1988-89
2004-05 1994-95 1991-92 1997-98 1984-85 2011-12 1998-99 2. Using figure 241, state the global
2006-07 2002-03 2015-16 2000-01 1999-00 average number of cyclones, hurricanes
2014-15 2009-10 2005-06 2007-08 and typhoons each year. (1)
2008-09 2010-11 3. Which ocean experiences the most
2016-17 rota ng tropical storms each year? (1)
4. What does the Saffir-Simpson Scale
Fig.255 Recent phases in the El Niño Southern Oscilla on. The strength of an El Niño or La Niña measure with regard to hurricanes? (1)
event is measured using the
Very strong to weak El Niño Neutral Strong to weak La Niña 5. Why are wind speeds low in the eye
3 Mul variate ENSO Index (MEI). This is
El Niño Events based on changes in the main of a hurricane? (2)
Standardised departure MEI 1 0 Pacific. These are: sea-level pressure; Pacific Ocean currents between El Niño
2
6. What is the general difference in
observed variables over the tropical
surface winds; sea surface
and La Niña years? (3)
temperature; surface air temperature
7. Explain why El Niño brings drought to
-1
Fluctua ons from the mean determine
La Niña Events and the cloudiness of the sky. Australian and New Guinea. (4)
8. Which have been the three strongest
-2 the strength of an ENSO event.
1980 1985 1990 1995 2000 2005 2010 2015 El Niño events since 1980? (1)
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Drought can be devastating for people and the environment.