AMS Climate Science and Climatology 2 — Questions and Answers
Question 1: El Niño conditions in the tropical Pacific are characterized by:
- Warmer-than-normal SSTs in the central and eastern tropical Pacific (Correct answer)
- Cooler-than-normal SSTs across the entire tropical Pacific
- Stronger-than-normal Walker circulation and trade winds
- Higher-than-normal sea level pressure in the central Pacific
Correct answer: Warmer-than-normal SSTs in the central and eastern tropical Pacific
El Niño is defined by anomalously warm sea surface temperatures in the central and eastern equatorial Pacific, which weaken the Walker circulation and alter global weather patterns.
Question 2: The Oceanic Niño Index (ONI) measures El Niño and La Niña events using SST anomalies in which Pacific region?
- Niño 1+2 (far eastern equatorial Pacific)
- Niño 3.4 (central equatorial Pacific) (Correct answer)
- Niño 4 (western equatorial Pacific)
- The entire tropical Pacific basin
Correct answer: Niño 3.4 (central equatorial Pacific)
NOAA's ONI is based on a 3-month running mean of SST departures from average in the Niño 3.4 region (5°N–5°S, 120°W–170°W), with ±0.5°C defining El Niño/La Niña.
Question 3: The Pacific Decadal Oscillation (PDO) differs from ENSO primarily in that:
- The PDO affects only the North Pacific, while ENSO affects the whole globe
- The PDO operates on decadal timescales, while ENSO operates on 2–7 year timescales (Correct answer)
- The PDO is driven by atmospheric forcing, while ENSO is purely oceanic
- The PDO only affects SSTs, while ENSO affects winds and precipitation
Correct answer: The PDO operates on decadal timescales, while ENSO operates on 2–7 year timescales
The PDO is a long-lived pattern of Pacific SST variability with phases lasting 20–30 years, much longer than ENSO's 2–7 year cycle, and modulates ENSO's impacts on North America.
Question 4: A positive phase of the North Atlantic Oscillation (NAO) is associated with:
- Weaker westerlies and cold, dry winters over northwestern Europe
- Stronger westerlies and warmer, wetter winters over northwestern Europe (Correct answer)
- Increased blocking events over the North Atlantic
- Stronger trade winds in the tropical Atlantic
Correct answer: Stronger westerlies and warmer, wetter winters over northwestern Europe
A positive NAO features an enhanced pressure gradient between the Azores High and Icelandic Low, driving stronger westerlies that bring mild, wet conditions to northwestern Europe and northern Eurasia.
Question 5: What is a climate teleconnection?
- A satellite communication system used by climate scientists
- A statistical relationship linking climate anomalies in geographically distant regions (Correct answer)
- A direct atmospheric bridge connecting tropical and polar climates
- A feedback loop confined within a single climate zone
Correct answer: A statistical relationship linking climate anomalies in geographically distant regions
Teleconnections are recurring and persistent large-scale patterns of pressure and circulation anomalies that span vast geographical areas and link climate variations in distant regions.
Question 6: The Quasi-Biennial Oscillation (QBO) refers to:
- A roughly 2-year alternating pattern of easterly and westerly winds in the tropical stratosphere (Correct answer)
- A 2-year cycle of precipitation in the tropical troposphere
- A biennial oscillation in Arctic sea ice extent
- A two-year variation in global mean surface temperature
Correct answer: A roughly 2-year alternating pattern of easterly and westerly winds in the tropical stratosphere
The QBO is a downward-propagating pattern of alternating equatorial stratospheric zonal winds at about 10–50 hPa, with a mean period of approximately 28 months, influencing storm tracks and tropospheric weather.
Question 7: The Atlantic Multidecadal Oscillation (AMO) has been linked most strongly to variations in:
- Western European drought frequency and North Atlantic hurricane activity (Correct answer)
- Pacific trade wind intensity and ENSO amplitude
- Antarctic ice shelf calving rates
- Indian Ocean dipole events
Correct answer: Western European drought frequency and North Atlantic hurricane activity
The AMO, a pattern of North Atlantic SST variability with 60–80 year cycles, is associated with shifts in Atlantic hurricane frequency, Sahel rainfall, and summer climate anomalies across Europe and North America.
AMS Climate Science and Climatology 2
El Niño conditions in the tropical Pacific are characterized by: