Table 11. El Nino years from 1910 to 1993 (Quinn et al., 1987). 
Event no. 
Year 
Strength 
21 
1911-12 
S 
22 
1914 
M + 
23 
1917 
S 
24 
1918-19 
W/M 
25 
1923 
M 
26 
1925-26 
VS 
27 
1930-31 
W/M 
28 
1932 
S 
29 
1 939 
M + 
30 
1940-41 
S 
31 
1 943 
M + 
Event no. 
Year 
Strength 
32 
1951 
W/M 
33 
1953 
M + 
34 
1957-58 
S 
35 
1965 
M + 
36 
1972-73 
S 
37 
1976 
M 
38 
1982-83 
VS 
39 
1 987 
M 
91-92 
* 
92-93 
* 
94-95 
* 
W/M - Nearly moderate. M+ - Nearly strong. S - Strong. VS - Very strong. 
* Personal communication. J. Bell, NOAA/NWS/National Meteorological Center Climate Analysis Center, Camp Springs, MD. 
5.2. El Nino events 
The El Niho/Southern Oscillation (ENSO) is the largest single source of interannual climatic 
variability on a global scale and its effects are wide ranging (Diaz and Markgraf, 1992). The 
Southern Oscillation is a large scale sea level pressure "seesaw" across the tropical Pacific 
Ocean. The anomalous oceanic and atmospheric conditions that occur periodically along the 
upwelling zone of the Equatorial Pacific along the coast of Ecuador and Peru is known as El Nino 
and is a manifestation of coupled ocean-atmosphere processes. The warm phase of this coupling 
is known as El Nino and the cold phase as La Nina. Winter et al. (1994) found a very good 
correspondence between low d 13 C values (indicative of cloud cover) in a core taken from a 
specimen of Montastrea annularis and strong El Nino events indicating that the Caribbean is 
sensitive to ENSO activity. Various efforts have been made to determine El Nino and La Nina 
years using various data sets and techniques. Several of these efforts are discussed in Diaz and 
Markgraf (eds.) (1992). Those determined by Quinn et al. (1987) are listed in Table 11. During 
the past centuries, El Nino events tend to repeat over periods of 3 - 4 or 7 - 8 yrs (Quinn et 
al., 1987; Brier et al., 1989; and others). 
Wilson (1989) compared onsets of El Nino events and major volcanic activity and found that 
40-60% of El Nino events are preceded within one or two years by major volcanic eruptions in 
the tropics, while 70-80% are preceded within one or two years by major eruptions 
somewhere in the world. A number of El Nino events, however, cannot be directly linked with 
any major volcanic eruption that preceded them within three years. Major, tropical volcanic 
activity can inject large quantities of aerosols into the stratosphere and can account for about 
70% of El Nino events. Wilson (1989) also compared onsets of El Nino events to specific phases 
of the solar/geomagnetic cycles and found that nearly two thirds of El Nino events had their 
onsets when the annual sunspot number was below 54 (the average annual sunspot number for 
the interval 1848 to 1987). 
Hanson and Maul (1991) identified rainfall anomalies associated with major El Nino events in 
the climate record of the seven climatic divisions of Florida. Only El Nino events that were 
strong enough to persist over two successive years were examined in this study. Therefore 
only "moderate" and "strong" events as defined by Quinn et al. (1987) were used. An additional 
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