El Niño and La Niña

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Use this

   Trade-wind arrows of different lengths across the Pacific.

2. 1.

   NOAA: normally air pressure is lower at Darwin and higher at Tahiti. What changes during El Niño, by Bo's reading?

   • Pressure at Tahiti rises even higher than it already is
   • Pressure stops mattering
   • Both pressures become equal for good
   • Pressure at Darwin becomes higher than at Tahiti
3. 2.

   Why does warm water normally pile up in the western Pacific, by Esme's reading (NOAA)?

   • Rivers in Asia add it
   • Trade winds push surface water west
   • Upwelling brings it up
   • Trade winds push water east
4. 3.

   Cold water rising off South America, with arrows of different sizes. During La Niña, trade winds are stronger than normal. What follows, by Jun's reading (NOAA)?

   • Warm water moves back east
   • More upwelling off South America and cooler eastern water
   • Less upwelling off South America and warmer eastern Pacific water
   • Rain shifts east

5. Use this

   Cross-section of the Pacific warm layer.

6. 4.

   NOAA: normally sea level is about 46 cm higher near Indonesia than near Peru. What causes this, by Luz's reading?

   • Trade winds pile water up in the west
   • Upwelling raises the water at Peru
   • El Niño pushes it west
   • The Moon's pull, by itself
7. 5.

   During El Niño the eastern thermocline deepens. Why does the surface water there warm, by Milo's reading (NOAA)?

   • Upwelling brings up less cold, deep water
   • The trade winds grow stronger
   • Sea ice melts nearby
   • Upwelling brings up more cold water

8. Use this

   A number line of anomalies above and below zero.

9. 6.

   Model data: Niño 3.4 temperatures run 0.4, 0.8 and 1.2 °C above normal over three months. What is the average, by Noah's math?

   • 0.8 °C below normal
   • 0.8 °C above normal
   • 1.2 °C above normal
   • 2.4 °C above normal
10. 7.

    Model data: Niño 3.4 averages 1.0 °C below normal for three months. Which phase does that suggest, by Pia's reading?

    • Neither, since below normal means warmer
    • A permanent change
    • La Niña, cooler than normal
    • El Niño, warmer than normal
11. 8.

    NOAA: western Pacific surface water is normally about 8 °C warmer than off South America. If the west is 29 °C (model), about what is the east, by Ren's math?

    • About 21 °C
    • About 29 °C
    • About 37 °C
    • About 3.6 °C

12. Use this

    Map of the U.S. with the jet stream dipping south or north.

13. 9.

    NOAA: in moderate to strong El Niño years, how does North Atlantic hurricane activity typically change, by Tala's reading?

    • It doubles
    • It rises sharply
    • It drops, with about 60% fewer hurricane days
    • It does not change
14. 10.

    If a normal season had 50 hurricane days (model), about how many would a strong El Niño year have, with NOAA's 60% reduction, by Ari's math?

    • About 110
    • About 30
    • About 20
    • About 80