Since fall has just started, the media is full of stories about autumn colors and the difference between astronomical and climatological fall.  Here are two I thought were especially interesting.

Slate magazine produced an online video which discusses why American trees produce both red and yellow leaves but European leaves only produce yellow leaves. The likely answer is tied to the orientation of mountain ranges which direct cold Arctic air down into mid-latitudes in the fall.  You can watch the video here.

Jim Angel, the Illinois State Climatologist, has a good blog post explaining the difference between astronomical, meteorological, and climatological fall with a graphic showing the yearly changes in temperature compared to when the equinoxes and solstices occur.  You can read his post here.