Geoscience Reference
In-Depth Information
A
SO Index
40.0
30.0
20.0
10.0
0.0
-10.0
-20.0
-30.0
-40.0
-50.0
1850
1870
1890
1910
1930
1950
1970
1990
2010
NAO Index
B
30.0
0.0
-30.0
1850
1870
1890
1910
1930
1950
1970
1990
2010
NPO Index
C
30
0
-30
1850
1870
1890
1910
1930
1950
1970
1990
2010
Indices of atmospheric pressure oscillations over time A) the Southern Oscillation, B) the North Atlantic Oscillation (from Hurrell, 2002a),
and C) the North Pacific Oscillation (from Hurrell, 2002b). The indices have been normalized to a mean of 0.0 hPa and a standard deviation
of 10. See relevant sections in the text for further explanation.
Fig. 2.8
warming is termed an El Niño event. In the early
1960s, Jacob Bjerknes recognized that warmer waters,
during some El Niño events, were linked to the
Southern Oscillation and the movement of warm water
eastward from the west Pacific Ocean. These more
widely occurring events are termed El Niño-Southern
Oscillation, or for brevity,
ENSO
events. Greater
amounts of warm water - along what is normally an
arid coastline - lead to abnormally heavy rainfall,
causing floods in the arid Andes rainfall region and
