I seems a lot of us have complained about the cloud question. As I remember the correct answer was that a cumulonimbus is a cumulous cloud that is actually raining - or words to that effect. I've looked at The Australian Climatic Environment (Linacre & Hobbs) a very technical book, The Australian Weather Book (Colls & Whitaker), the BoM site and the NOAA site and nowhere can I find the act of precipitating as a defining feature. Linacre and Hobbs state that 'Where thunderstorms
may form, the cloud is called cumulonimbus.' (my emphasis) The definition seems to be that it is a cloud of great vertical extent which has reached the top of the troposphere and developed the classic anvil top. This makes sense to me because first, no other cloud is defined in such a way and second, there are such things as dry storms with no rain but plenty of lightening which indicates strong convective circulation and so great vertical development. [The World Meteorological Organisation is the authority if anyone want to follow this up.]
So at the moment my hypothesis is that the quiz was wrong. It happens. Everyone mark yourself up 1.
