Rainbow clouds have been visible for several evenings recently. They are known as “nacreous” (or polar stratospheric) clouds and are very unusual in Britain. Nacreous clouds typically form in the winter polar stratosphere, a layer of our atmosphere around 15,000 to 25,000m in altitude. The stratosphere is generally very dry and so cloud formation is rare, but it seems as though recent storms may have driven moisture high into the atmosphere and the very low temperature turns any moisture in the air into ice crystals. On the down side, these clouds enhance the breakdown of the Earth’s ozone layer, as the ice crystals in the clouds encourage a chemical reaction between the ozone layer and gases such as chlorine and bromine (giving the colours).
Nearer home lovely to see a flock of 10 Long-tailed tits in the garden plus the usual feeder species squabbling for possession.
