El Nino-La Nina, North Atlantic Oscillation, and Climate Variability
Sample Questions based on Workshops presented by Dr. Martin Visbeck
February 2000 (“The North Atlantic Oscillation and Climate Variability” with Martin Visbeck)
February 2001 (Air-Sea Interactions with Martin Visbeck)
by Dr. Michael Passow
Here are some examples of questions to check your knowledge of these important factors influencing climate change, as well as practice for state assessments.
Question Set 1–El Nino-La Nina
The chart below presents a comparison of selected atmospheric and oceanic conditions in the western Pacific and Eastern Pacific during the “long-term-average” and an “El Nino” event. Use this chart and your knowledge of science to answer the questions below.
| Variable | Long-term-average W. Pacific |
El Nino event W. Pacific |
Long-term average E. Pacific |
El Nino event E. Pacific |
Atmospheric |
||||
| Rainfall | high | lower | low | higher |
| Surface air pressure | low | higher | high | lower |
| Trade winds | weak east-to-west | variable | strong east-to-west | strong east-to-west |
Oceanic |
||||
| Surface currents | east-to-west | west-to-east | east-to-west | west-to-east |
| Sea surface temp. | high | lower | low | higher |
| Sea surface height | high | lower | low | higher |
| Thermocline depth | deep | shallower | shallow | deeper |
Multiple-choice:
_____Compared with the “long-term-average” in the eastern Pacific, surface air pressure during an “El Nino” event
1. decreases and rainfall decreases
2. decreases and rainfall increases
3. increases and rainfall decreases
4. increases and rainfall increases
_____During an “El Nino” event, the warm water layer near the surface in the western Pacific
1. becomes shallower as cold water upwells from below
2. becomes thicker as winds blow warm water from east-to-west
3. remains the same thickness as during “long-term average” conditions
4. varies with longitude
Constructed response:
Explain the affect warmer water in the eastern Pacific during an “El Nino” event would have on the area’s surface air pressure and rainfall patterns
Describe two changes in oceanic conditions in the western Pacific during and “El Nino” event compared with “long-term-average” conditions.
Explain why using “sea surface temperature anomaly” patterns are more useful to oceanographers than using actual sea surface temperatures.
Question Set 2 North Atlantic Oscillation
The chart below shows the pattern of sea level pressure differences between two selected locations. This is called the “North Atlantic Oscillation (NAO) Index.”
[Source: J. Hurrell, from http://www.ldeo.columbia.edu/programs/index.html]
Impacts that have been associated with a positive NAO value include: warmer winter temperatures and fewer snow days in northeastern North America; longer growing seasons in Scandinavia, and greater rainfall and river runoff in the Central US. Impacts associated with a negative NAO value include: warmer sear surface temperatures, more and stronger hurricanes in the tropical Atlantic and Gulf Coast; greater scallop harvests in eastern Long Island; and increased grade and olive harvests in Spain and Portugal.
Multiple-choice:
_____During most of the past fifteen years, the NAO has helped create in Europe and the northeastern U.S. winters that were
1. colder than normal
2. milder than normal
3. near the average
_____Very severe winters in Europe associated with a strongly negative NAO occurred in
1. 1870, 1925, 1970
2. 1892, 1904, 1955
3. 1904, 1982, 1987
4. 1916, 1936, 1969
Constructed response:
Provide an analysis of whether these data support the theory of Northern Hemisphere warming during the last fifty years.
