DataStreme Activity 9B:

¡EL NIÑO!

Note: You should examine the color images (Image 1, 2, and 3) while you are "on-line".

Do Now:

  1. Print this file.
  2. Print the Wednesday Image 1, Image 2, and Image 3 Files.
  3. Print (when available) the Thursday, 9 November 2000, Daily Summary File.

To Do Activity:

  1. Read Chapter 9 in STUDY GUIDE, Part A: Narrative.
  2. Go to STUDY GUIDE, Part B: Applications. Start Activity 9B.
  3. Return here (Wednesday Activity B File) when told to do so.

Go To STUDY GUIDE - Activity 9B Now


WELCOME BACK: Procedure continued from STUDY GUIDE.

  1. The planetary-scale circulation of the atmosphere along the equatorial InterTropical Convergence Zone (ITCZ) includes the northeasterly trade winds of the Northern Hemisphere converging with the southeasterly trades of the Southern Hemisphere. But this generalized picture does not describe all the fluctuations of the dynamic Earth-atmosphere system. Changing temperatures in the upper layers of the Pacific Ocean and the overlying atmosphere along the Equator lead to the Southern Oscillation and El Niño/La Niña episodes. In much of 1997 and early 1998, the tropical Pacific Ocean was experiencing a strong El Niño. The effects of these tropical ocean-atmosphere conditions extended well beyond the tropics and may well have set the stage for the extensive storminess along the West Coast, the relatively warm and dry weather in the Southeast, and unusual weather elsewhere that occurred during that time period. Later 1998 into 1999 saw the shift to La Niña conditions in those tropical waters. Those La Niña conditions have waned and the tropical Pacific is presently experiencing conditions that are near the long-term average.

    Image 1 is a depiction of the ocean surface temperatures and atmospheric surface winds in the tropics as measured primarily by an anchored-buoy array along the Equator. The mapped area extends ten degrees of latitude north and south of the Equator and from near the South American coast on the east to near Indonesia on the west. The top view, labelled November 1997 Means, is the average sea surface temperatures (shaded and isothermed) and surface winds (as shown by arrows) for the month of November 1997, near the peak of the 1997-98 El Niño episode.

    The sea surface temperatures (SSTs) across the region ranged from about 26 °C as the "coolest" in the southeast corner to above [(20) (25) (30)] °C just south of the Equator, west of center in the upper panel. The warmest SSTs were located in the neighborhood of about [(170° W) (120° W)] Longitude in the Pacific.

  2. The wind directions in the eastern Pacific were generally from the southeast. However, in the west-central Pacific, along the Equator (from about 160° E to 150° W), generally [(light) (strong)] winds were from the west. These wind conditions generally [(were) (were not)] consistent with the depiction of the Trade Winds shown in the small windows of the ¡El Niño! ¡La Niña! at the "El Niño" setting.

  3. The ¡El Niño! ¡La Niña! indicates that SSTs in the eastern Pacific during an El Niño event are [(above) (below)] the "Long-Term Average" values. This is shown on the ¡El Niño! ¡La Niña! as the red line in the window compared to the black, long-term average mark alongside the window. This condition is a [(positive) (negative)] SST anomaly.

  4. The bottom view of Image 1 (November 1997 Anomalies) is a depiction of SST and wind anomalies, that is, departures of the observed values shown in the top view from the long-term average. (Note: Positive anomaly isotherms are solid lines. Negative anomaly isotherms are dashed lines. A heavy line labeled 0 shows where no temperature anomaly exists.)

    The shaded and isothermed SST anomalies in the eastern Pacific were positive, with some by more than [(1.5) (4.5) (7.5)] C°. SST anomalies across the tropical Pacific were all positive except for two small regions near the western corners of the image where temperatures were slightly below the long-term average (above and below the heavy "0" lines). The eastern Pacific SST anomaly [(was) (was not)] consistent with the depiction in the small Sea Surface Temperature window of the ¡El Niño! ¡La Niña! at the "El Niño" setting.

  5. Image 2 is a similar depiction of the tropical Pacific SST and wind conditions for November 1998, one year later than Image 1, showing La Niña conditions had replaced those of El Niño. In November 1998, the sea-surface temperatures along the Equator in the eastern Pacific were near 22 °C, several degrees [(warmer) (cooler)] than those in the same area in November 1997 during the El Niño. The winds across the entire Pacific area of the depiction were now generally from the [(east) (west)].

  6. The lower panel of November 1998 Anomalies shows the Pacific SST anomalies along the Equator being almost all [(positive) (negative)], also denoted by the dashed lines, with values going below [(-1) (-2)] C°. This relatively cool (compared to the Long-Term Average) water marks the identification of La Niña. The La Niña conditions can be seen on the reverse side of the ¡El Niño! ¡La Niña! insert.

  7. The upper panel of Image 3 is the depiction of the five-day mean tropical Pacific SST and wind conditions ending on 6 November, 2000, the current situation. The shading and isotherms indicate that the coolest waters across the tropical Pacific are located in the [(western) (central) (eastern)] Pacific near and just south of the Equator. The winds include motions generally toward the [(west) (east)] across the entire Pacific to 150 °E.

  8. In the lower view (Anomalies), the November 2000 SST anomalies are generally slightly positive in the [(eastern) (western)] tropical Pacific while they are negative over most of the [(central and eastern) (western)] Pacific. The anomalies imply that, while the temperatures (as seen in the top panel of the image) range from cool in the east to warm in the west with cooler extensions along the equator, this pattern is about average over the long-term (of existing measurements). The current near-neutral conditions are expected to prevail over the area for the next few months. The latest forecast for the tropical Pacific can be found at: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html.

More information on El Niño can be found at: http://www.elnino.noaa.gov/ and for La Niña at: http://www.elnino.noaa.gov/lanina.html . For the latest five-day average conditions from the TAO buoy array, you can access http://www.pmel.noaa.gov/tao/jsdisplay/.


Faxing Instructions:

After completing this week's applications, fax the following pages to your LIT mentor by Monday, 13 November 2000:

  1. Chapter 9 Progress Response Form from the Part B: Applications binder, Week 9, or the DataStreme Homepage.
  2. 9A and 9B Activity Response Form.
  3. STUDY GUIDE, Part B: Applications, page 9A-5.

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URL: datastreme/learn/b_act.html
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