Textbook Problem

Sea Temperature To predict the effect of El Niño or La Niña events in the future, the National Oceanographic and Atmospheric Administration collects information about sea surface temperature (SST) and atmospheric conditions. They compare monthly temperature averages in the eastern equatorial Pacific Ocean to historical data and calculate the difference (the degree of anomaly) to determine if El Niño conditions, La Niña conditions, or neutral conditions are developing. El Niño is a rise in the average SST above 0.5°C. A decline of the same amount is La Niña. FIGURE 47.8 shows data for 42 years.

FIGURE 47.8 Sea surface temperature anomalies (difference from the historical mean) in the eastern equatorial Pacific Ocean. A rise above the dashed red line is an El Niño event, a decline below the blue line is La Niña

When did the greatest positive temperature deviation occur during this time period?

Summary Introduction

To determine: The greatest positive temperature deviation.

Concept introduction: EI Nino Southern Oscillation (ENSO) event is an interaction between the ocean-atmosphere climates, during which irregular temperature fluctuation occurs in the equatorial Pacific Oceans. EI Nino and La Nina are the two extremes of this EI Nino Southern Oscillation. During an EI Nino, warm water flows towards the west coast of South America and during a LA Nina, cold water flows towards the western coast of South America. At other time, water of the Pacific is neutral.

Explanation of Solution

The National Oceanographic and Atmospheric Administration collect information regarding sea surface temperature (SST) and different atmospheric conditions to monitor and to observe if climatic events coordinate with the events of EI Nino, La Nina, or just neutral in the future. For this purpose, they compare monthly average temperature with the historical data in the equatorial Pacific Oceans. They estimate the difference to determine the different conditions that are developing, whether an EI Nino conditions, La Nina conditions, or normal conditions.

Refer to the Fig. 47.8 “Sea surface temperature anomalies (difference from the historical mean) in the equatorial Pacific Ocean” in the textbook. It shows that an EI Nino rises above the SST that is above the dashed red line and a La Nina declines below the SST that is below the dashed blue line. In the year 1998, the greatest positive temperature deviation occurred. EI Nino rises in the average SST above 2.5^°C.

Conclusion

During the year 1998, the greatest positive temperature deviation occurred.