Altitude and snow
Dear HIW, Your latest magazines have been fascinating, but in one of them it made me think of a strange question. In the French Alps people often say it snows a lot because of altitude. If this is true then how come in England, a country more northerly than France, when you are in an aeroplane and it is raining, you can only see rain instead of snow? Many thanks, Pascal Ahearne, aged 12
Hi, Pascal. You have made a great observation. The answer is a bit complicated, but it basically comes down to how high above the ground you can find rain-making clouds and how high you have to be for altitude to affect the temperature. As your plane takes to the sky, you might pass through rain and then some clouds, but after a few minutes you’ll notice you’re above the fluffy, dense clouds. It’s these fluffy clouds that create rain and snow. Once you’re at altitude you have passed them, and you’re now surrounded by a different type of cloud that doesn’t precipitate, so you only experience rain or snow during take-off or landing. These low-level clouds are usually not high up enough that they are affected that much by altitude, so if it is raining on the ground it will also be raining in these low-level clouds (or at least forming ice in such small snowflakes that they melt the instant that they touch your plane window). In England it rains a lot, and we have these low-level clouds at relatively low altitude because the country is close to sea level (not at high altitude). However, when you’re on the mountains you’re at a much higher altitude, and so are the rainmaking clouds, which means they are able to make a lot of snow. We hope that answers your question Pascal, and thanks for writing to us.