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 stops mattering
   • Pressure at Tahiti rises even higher than it already is
   • 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)?

   • Trade winds push water east
   • Trade winds push surface water west
   • Rivers in Asia add it
   • Upwelling brings it up
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)?

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

5. Use this

   Cross-section of the Pacific warm layer.

6. 4.

   NOAA: normally the warm layer is about 150 m thick in the west, while the eastern thermocline is about 30 m deep. How much deeper does the western warm layer reach, by Kira's math?

   • About 120 m
   • About 180 m
   • About 5 m
   • About 4,500 m
7. 5.

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

   • The trade winds grow stronger
   • Upwelling brings up more cold water
   • Upwelling brings up less cold, deep water
   • Sea ice melts nearby
8. 6.

   A number line of anomalies above and below zero. 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 above normal
   • 0.8 °C below normal
   • 1.2 °C above normal
   • 2.4 °C above normal
9. 7.

   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
10. 8.

    Map of the U.S. with the jet stream dipping south or north. NOAA: in moderate to strong El Niño years, how does North Atlantic hurricane activity typically change, by Tala's reading?

    • It rises sharply
    • It does not change
    • It drops, with about 60% fewer hurricane days
    • It doubles
11. 9.

    Cold water rising off South America, with arrows of different sizes. NOAA: why is there less phytoplankton off South America during El Niño, by Zee's reading?

    • Weaker upwelling brings up fewer nutrients
    • Stronger upwelling brings too many nutrients
    • Trade winds blow them away
    • Colder water stops their growth
12. 10.

    Map of the U.S. with the jet stream dipping south or north. 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 20
    • About 110
    • About 30
    • About 80