Part 3—Discover SST Associated with El Niño and La Niña
Step 1 – Investigate an El Niño Year
- We have already calculated the average SST for the period of 1982 to 1998 (Overall Average). Now calculate the average SST for Dec. 1997. Enter Monthly Average, Dec 1997 as the name for the result.
- To view the differences between two grids is to generate a "difference" image. A difference image will show the "departure from normal" of each location as red if it is warmer than normal and blue if it is cooler than normal. This is known as an anomaly, or difference, map. Subtract the overall average from the 1998 average and name the result "1997 Difference from Overall Average."
- Apply a standard color scheme to your difference image that you'll be able to copy to other ones. Choose the red-white-blue color scheme and change the minimum temperature to -2 and the maximum temperature to 2.
Step 2 – Investigate a La Niña Year
The following year after this strong El Niño event, a La Niña set up in the Pacific Ocean. As you did for the El Niño year, predict what pattern in SST would you expect to observe in the Pacific if it were a strong La Niña year?
You have already calculated the average SST for the period of 1982 to 1998. Next you will need to calculate the average SST for Dec 1998 and then subtract the Overall Average from it. This calculation will show you the difference between "normal" and the 1998 year.
- Create a monthly average from the five weeks of 1998. Enter Monthly Average, Dec 1998 as the name for the result.