7. Data from the equator

The data in the following section are from NOAA's TAO buoy array along the equatorial Pacific. An archive of these data can be found at the NOAA/ PMEL TAO Home Page. TAO = Tropical Atmosphere Ocean; PMEL = Pacific Marine Environmental Laboratory.



(a.) The diagrams below show changes in sea-surface temperatures and winds along the equator from 140 east longitude (western Pacific) to 110 west longitude (eastern Pacific). The upper diagram illustrates equatorial conditions during a normal year (1991); the lower diagram illustrates conditions during an El Niño year (1992).

Each diagram has two parts. The upper part (monthly mean) shows the actual conditions on the equator, including the temperature (in degrees Celsius), and the wind speed and direction. Arrows point in the direction the wind is blowing toward and longer arrow length indicates stronger wind speed. The lower part (anomalies) shows the difference between the observed monthly average and the long term monthly average. Temperature anomalies greater than 0.0 are places with higher than normal sea-surface temperatures and anomalies less than 0.0 are lower than normal. Arrows show differences in wind direction and speed. For example, an arrow pointing toward the east shows winds that are more easterly than normal. The longer the arrow, the stronger the anomaly. Note that these diagrams account for expected seasonal variations.


Based on what you have learned so far, explain the changes between normal and El Niño years that are illustrated by these data. Keep in mind that these data show only sea-surface conditions (not conditions at depth).

(b.) Using the formula below, convert Celsius degrees to degrees Fahrenheit:

[formula: degrees Fahrenheit = 1.8 (degrees Celsius) + 32]

28 degrees Celsius = ? degrees Fahrenheit

20 degrees Celsius = ? degrees Fahrenheit

15 degrees Celsius = ? degrees Fahrenheit

8 degrees Celsius = ? degrees Fahrenheit



(c.) The next images are similar to those in part (a), but show data from 1 December 1996.



Based on the sea-surface temperatures and winds shown in this diagram, do you think that this was a year of normal or El Niño conditions?



(d.) Another way to view the NOAA buoy data is shown below. This diagram shows the variation of temperature along the equator (0 degrees latitude) from the ocean surface to 500 meters depth. The diagram is the monthly average from November 1996 and shows normal conditions along the equator. Like the diagrams above, the upper part shows actual sea-surface temperatures measured at the buoys and the lower part shows the difference between observed conditions and the long-term monthly average for November. These conditions are interpreted as "normal" because the temperature anomalies are small.

Describe the variations in ocean temperatures from east to west along the equator and from the surface to 500 meters depth during a time of normal conditions in the Pacific Ocean.

(e.) Examine the temperature variations in the diagram above at 110 west longitude from 0-200 meters depth (normal conditions). The diagram below shows changes in wind direction and in ocean temperatures from 0-200 meters depth for a two-year period in the eastern Pacific (110 W). In the upper part, red lines pointing upward indicate eastward-moving winds; lines pointing downward indicate westward-flowing winds. Temperature measurements are shown in the lower part (isotherms = lines of equal temperature).


Where in the Pacific Ocean were these data collected? (Look at a world map at the appropriate latitude and longitude.)
During which months were El Niño conditions strongest during the 2-year period shown in the diagram above?

During which month(s) did El Niño conditions begin?

 

(f.) Go to the Real-time TAO Buoy Data Display to see what the average situation along the equator has been like in the last 5 days. Do you think the ocean-atmosphere system is currently in a normal mode, closer to an El Niño state, or closer to a La Niña condition?


Return to exercise home page