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THE LAST WORD Rain, rain, go away I have been reading that the chair of the UK’s Environment Agency, Lord Smith of Finsbury, has been warning of “a new kind of rain”. Apparently, “convective rain” does not sweep across the country but dumps its deluge in just one place, putting great strain on that particular area. Is this a real and new phenomenon caused by climate change? And if it is, what causes it? n Convective precipitation is by no means a new phenomenon. Indeed, every time the phrase “sunshine and showers” is used in weather forecasts, convective rainfall is implied. It is caused by a sharp temperature gradient in the lower atmosphere. Warm air at the surface of the Earth rises through cold air higher in the atmosphere in columns known as thermals. As a thermal rises it cools, and the moisture contained within it condenses to form towering cumulonimbus clouds. These can then deposit heavy but short-lived bursts of rain or snow. In summer, the sun can heat the air just above the ground so much that huge thermals rise to give us thunderstorms. In winter, during a cold snap, warmer air over the sea can gather lots of water and rise into a bitterly cold air mass, causing intense falls of snow. This is sometimes called “lake effect” snow, so named after a similar phenomenon over the Great Lakes of North America which gives severe blizzards in winter. Convective precipitation is very different from frontal precipitation, which is caused by the sideways collision of two air masses of different temperatures forcing warm air to rise and resulting in thick cloud. Slow-moving convective precipitation can be caused by “convergence zones”, where two warm air masses meet and are forced upwards. This was responsible for the severe flooding in Boscastle in Cornwall, UK, in August 2004. Although this is not a new phenomenon, warmer air in summer caused by climate change perhaps makes these events more likely. William Torgerson York, UK Float like a butterfly I came across this lovely creature (see photo) on a wild hillside on the west coast of Tuscany, Italy, one April, at about 100 metres above sea level. It flew like a butterfly, dancing around in pairs with others like it, and was about 4 centimetres across, but it doesn’t seem like any butterfly I’ve seen, nor is it in any of my insect books. It is very beautiful, what is it? n This insect is the owlfly Libelloides coccajus, related to lacewings and antlions. I have seen them in Burgundy in France and in the Pyrenees mountains, and have observed their butterfly- like qualities. Edmund Scott By email, no address supplied n These insects go by the picturesque name of owlflies because of their bulging eyes. They are a kind of lacewing of the order Neuroptera, and belong to the family Ascalaphidae, which takes its name from Ascalaphus, the custodian of the orchard in Hades, who was transformed by an angry Demeter into an owl. There are about 15 known species in Europe, and this appears to be Libelloides coccajus – the sulphur owlfly. The prominent claspers at the tip of the abdomen indicate that it is a male. Owlflies are closely related to antlions of the family Myrmeleontidae. They are superficially similar, but whereas antlions are principally nocturnal, owlflies are active in the sunshine, flying straight and level a couple of metres above the ground where they hawk for small insects in the manner of dragonflies. The Latin word “libella” means “level”, and is the origin of the French word for dragonfly, une libellule. From this seems to come the genus name Libelloides. Just like the larvae of antlions, owlfly larvae are predators, feeding on other insects found in soil detritus and under stones. Terence Hollingworth Blagnac, France This week’s question KNOBBLY CHEESE Why do Grana Padano , cheddar and feta cheeses, to use three random examples, all break in different ways and have inside surfaces with very different appearances? After all, they are all cheese. Maria Brigida Pesaro, Italy “Every time sunshine and showers are mentioned in weather forecasts, convective rain is implied” Last words past and present at newscientist.com/topic/lastword The new book out now: packed full of wit, knowledge and extraordinary discovery Available from booksellers and at newscientist.com/dolphins Will we ever speak dolphin?
