QUINN ET AL : SOUTHERN OSCILLATION. EL NINO, AND INDONESIAN DROUGHTS 



DISCUSSION 



Over the past 1 16 yi- ( 1861-1976), for which we 

 have adequate data on the occurrence of El Nino 

 type events of weaker intensity, there were de- 

 cades of minimal activity (e.g.. 1901-10, 1931-40, 

 1961-70), but no decade without such activity. 

 There is no reason to expect any significant change 

 in the amount of El Nino activity in the foresee- 

 able future over that experienced in the past cen- 

 tury. Therefore, it would appear that our data 

 (e.g.. Tables 2-5) might eventually be used in con- 

 junction with associated catch data and biological 

 findings for effective long-range planning in the 

 management of the anchoveta fishery. For exam- 

 ple, assessment of maximum sustainable yields 

 under various environmental conditions ranging 

 from the favorable extended anti-El Nino condi- 

 tion (when there are two or more consecutive years 

 with high Southern Oscillation indices) to the El 

 Nino situation (when there are rapidly falling and 

 low Southern Oscillation indices) might prove use- 

 ful for determining the optimum size and flexibil- 

 ity of the fishing fleet and fish processing facilities. 

 A key element to such assessments will be a know- 

 ledge of the required biological recuperation time 

 following cessation of an unfavorable physical en- 

 vironmental condition. 



Such data could also be used for speculative 

 long-range outlooks. For example, if we had just 

 experienced a strong El Nino, our results suggest 

 that there is a near-zero probability that we would 

 experience another strong event in < 7 yr after the 

 onset of the recent situation. However, there 

 would be an 86Vir probability that an event in the 

 very weak, weak, or moderate category would 

 occur within 3-4 yr after the strong El Nino onset. 

 Considering the current situation, and recogniz- 

 ing that a moderate event set in during 1976 and 

 held over into early 1977, there is a dAVc probabil- 

 ity (based on our data) that another event of un- 

 known intensity would set in during 1980. It 

 would not be reasonable to go beyond statistical 

 estimates until we find we are approaching a peak 

 in the Southern Oscillation index anomalies. 



When we are nearing a preevent peak and can 

 assess its height and time of occurrence, then we 

 can use peak to trough statistics (e.g., Figure 7) to 

 advantage in forecasting onset time and likely 

 intensity of the coming El Nino type event. The 

 intensity would be based on the height of the index 

 anomaly peak and the time of year when the sub- 

 sequent trough was expected to occur. Event onset 



time can be further refined by considering Figure 

 8 statistics. It is also essential in the prediction 

 procedure to realize that some developments may 

 involve two or more stages. In cases of this type, 

 forecast lead times for the separate stages will 

 often be greatly reduced (to 1-6 mo in advance), 

 unless historical analogies lead to pattern recog- 

 nition as the situation evolves. 



ACKNOWLEDGMENTS 



We thank the Chief of the Naval Weather Ser- 

 vice and the Director of the Hydrographic Insti- 

 tute of the Armada de Chile; the Director of the 

 Civil Aviation Service and Chief of the 

 Meteorological Service of Polynesie, Francaise; 

 the Director of the Meteorological and Geophysi- 

 cal Institute, Djakarta, Indonesia; the President of 

 the Instituto del Mar del Peru; Ramon Mugica, 

 Cniversidad de Piura, Peru; the Director of the 

 Australian Bureau of Meteorology; and, the Na- 

 tional Climatic Center, Environmental Data Ser- 

 vice, NOAA, for their support of this study. We are 

 indebted to Forrest R. Miller of the Inter- 

 American Tropical Tuna Commission and Richard 

 Evans of the Southwest Fisheries Center, Na- 

 tional Marine Fisheries Service, NOAA, for their 

 timely information on sea temperatures and 

 weather conditions over the eastern tropical 

 Pacific. We also thank Clayton Creech for his sup- 

 port in data processing. Support by the National 

 Science Foundation under the North Pacific Ex- 

 periment of the International Decade of Ocean 

 Exploration through NSF Grant No. OCE 75- 

 21907 AOl, and under the Climate Dynamics 

 Program of the Division of Atmospheric Sciences 

 through NSF Grant No. ATM77-00870 is grate- 

 fully acknowledged. 



LITERATURE CITED 



Berlage, H. p. 



1957. Fluctuations of the general atmospheric circulation 

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1969. Atmospheric teleconnections from the equatorial 

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Clayton. H. H. 



1927. World weather records. Smithson. Inst. Misc. Col- 

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