The Science Behind Changing Leaves
BOWLING GREEN, Ky (WNKY) – It’s a phenomenon that happens every year, and it captivates the eyes of many around the fall season. Two words can be used to describe that, Fall Foliage!
Each year the autumnal equinox arrives, giving us equal hours of daylight and nighttime. Beyond that, days get shorter and leaves start to transition as trees prepare to endure the winter months.
What causes the leaves to change color during the fall season? That’s the question it took to WKU Meteorology professor Dr. Greg Goodrich.
” It’s the combination of shorter days and cooler nights that sends a signal to the trees to stop producing Chlorophyll and it’s Chlorophyll that gives the leaves their green color.” Said Dr. Goodrich
Chlorophyll is a green chemical on leaves that is fed by sunlight. Since the sun angle is higher in the summertime, there’s greater energy intake. The lower sun angle in the fall season doesn’t provide a sufficient amount of sunlight. Thus, the energy stored from the Chlorophyll breaks down, causing the leaves to lose their green exterior.
“Once that green color starts to fade away, then you start seeing other colors appear, and those colors range from yellow to orange, red to even purple.”
There are various color species that can be found here in Kentucky. Some common ones include Dogwood, Oaks, Sourwood, and Poplars under the right conditions of course…
The timing and display of the fall colors can be affected by two weather related factors; temperature and moisture!
“The colors start to happen a little earlier if you start getting some colder air, stronger cold fronts, colder airmasses that can shock the trees into shutting down chlorophyll.”
If there are drought conditions and unseasonably warmer temperatures, the leaves may hold off on changing in a timely fashion and the leaves may have a brownish color. On the flip side, strong fall fronts that usher in rainfall and leave behind seasonably cool temperatures can help give leaves a vibrant color during the transitional period.