The answers to this quiz appear in blue below each question.

1. Two of these statements are false. Which one is true?
(A) The individual convective cells that collectively make up this cloud structure are quite shallow, with heights generally less than 2 km.
(T) These cloud systems only occur when the ocean temperature is above 80 degrees F (26.5 degrees C).
(F) These clouds are usually associated with violent storm systems.

Answer: A is True. These clouds are associated with cellular (or shallow) convection, and are restricted to the bottom 2 km of the atmosphere.

2. Two of these statements are false. Which one is true?
(U) These clouds are often detected using ground-based radar.
(C) This type of cloud was first imaged from space in the early 1960's, soon after the launch of the TIROS V satellite.
(Y) These clouds are commonly tracked using propeller-driven research aircraft.

Answer: C is True. The weather satellite, TIROS V, was the first to image these clouds. The first example image was published in January 1963, in the Monthly Weather Review, Picture of the Month Series.

3. Two of these statements are false. Which one is true?
(N) These clouds persist only for a short time when severe weather is occurring.
(P) Clouds of this type occasionally produce heavy precipitation.
(T) The organization of these clouds resembles Rayleigh-Bénard convection.

Answer: T is True. The cloud organization (with clouds forming where air has risen, and clearing where the air descends) does indeed resemble Rayleigh-Bénard convection, which is easily produced in the laboratory by heating a shallow layer of fluid from below and cooling it from above.

4. Two of these statements are false. Which one is true?
(H) When these clouds make landfall, they often spawn tornadoes.
(I) These clouds are often observed to form off the western coasts of continents.
(N) These clouds form when the atmospheric pressure drops very rapidly, causing condensation.

Answer: I is True. Actinoform clouds have been most commonly observed over the Pacific Ocean to the west of South America, and have also been found over the oceans to the west of Africa and Australia, in areas associated with extensive low cloud.

5. Two of these statements are false. Which one is true?
(N) These clouds were originally thought to be a transitional form between open and closed cells.
(E) This type of cloud system plays a major role in the 1939 movie adaptation of a book published in 1900.
(O) Cloud systems of this type are often given names contributed by Asian-Pacific countries.

Answer: N is True. Although the verdict is still out on exactly how open and closed cell patterns develop, and why one type of pattern develops versus the other, actinoform clouds can no longer be classed as a transitional form between open and closed cells.

6. Two of these statements are false. Which one is true?
(L) Hail often occurs when these clouds are seen.
(A) Cloud systems like these are associated with cold ocean currents.
(O) These cloud systems rarely form near the equator.

Answer: A is True. The cellular patterns associated with actinae generally occur over cool ocean currents, although it has been suggested that they can also can occur over warm currents.

7. Two of these statements are false. Which one is true?
(N) The Coriolis force strongly influences the morphology of these cloud patterns.
(E) The name describing these cloud forms is also used in conjunction with certain sea creatures.
(S) The vorticity associated with such clouds can be very dangerous, and when they are seen, you should take cover.

Answer: E is True. The word "actinae" refers to radial symmetry. Radial symmetry is present in animals such as starfish, sea urchins, and sea anemones.

MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.