Autumn sees the landscape change from shades of green to a spectrum of red, gold, orange and brown. Photographs and reports from this year show a particularly beautiful season in the UK, but why has it been just so spectacular?
The vibrancy of the leaf colours and duration of display varies annually due to different chemical concentrations that is affected by changes in weather, soil and altitude. As the summer ends and the days get shorter, this reduces the amount of chlorophyll produced; a chemical that causes the leaf to appear green. Now as the chlorophyll begins to break down, other coloured pigments can take over. Carotenoids are mainly yellow or orange pigments, and anthocyanins appear as red or purple pigments.
Spring and summer seasons that have provided an abundance of moisture, followed by rather dry, warm and sunny autumns with cool but frostless nights provide the best weather that leads to the brightest colours. New England in north-east America is famous for its spectacular autumnal displays, whereas in the UK the season can be relatively muted. The difference is down to the weather. In New England, the weather in autumn typically brings bright, dry, sunny days combined with cool nights, whereas in Britain the conditions are cooler, damper, and more overcast.
However this year the weather has bought favourable conditions for creating the best autumn conditions. High pressure has dominated the UK weather, bringing notably dry conditions for much of the country. Based on Met Office statistics, there was just 38% of average UK October rainfall, ranking it the sixth driest October since 1910. Sunshine levels were also close to or above, with northern Scotland recording its sunniest October on record in 85 years, and the UK as a whole received 117% of average sunshine. Mean temperatures were either close to or a little above average, with a lack of air frosts. Overall, this created dry, warm, sunny days, and frost-free nights providing the perfect conditions for a picture-perfect autumn. A lack of heavy rainy periods and windy, violent storms that have previously caused an abrupt to end autumn before it’s even begun, have allowed the beautiful autumnal conditions to prevail.
With a warming climate and changing precipitation patterns, can we expect a change in autumn in the future? A longer growing season will likely keep trees greener later into the autumn, however the risk of a sudden frost remains, which can cause vegetation to shed their leaves before they go reach their full potential and go through the full colours of autumn that we’ve experienced this year.