Autumn here comes on subtly at first. We start to see the signs in August, particularly this year when the sudden turn to minor drought prompted some early color change on the shallow soils here on …
Autumn here comes on subtly at first. We start to see the signs in August, particularly this year when the sudden turn to minor drought prompted some early color change on the shallow soils here on the ridge. The bracken ferns, which grew lush on the early summer rains, began showing their fall yellows, tans, and oranges by the latter half of the month. The maples sported some early fire, before dropping many of their leaves even before Labor Day due to the dry conditions. Even so, the forest is still mostly green.
For me, the most dramatic early sign of the change of seasons can be seen on those first clear mornings in late August or early September, when the initial chill of approaching autumn settles over the warmth and humidity still lingering in the Lost Lake Swamp.
The combination creates huge banks of fog that linger for an hour or so after the sunrise, giving early risers, like me, the chance to appreciate them before they dissipate as the temperature begins to rise.
Fog is common in autumn because it commonly forms in two ways under conditions that are common this time of year. We’ve all seen morning mist on the water on those first chilly mornings of September. This is called evaporation fog, which is generated when cold, dry air moves over the surface of warmer water, which is a common occurrence this time of year, particularly in the morning. As water evaporates into the air above it, the water vapor is cooled, forming suspended droplets that appear as fog or mist.
The fog that settles into the Lost Lake Swamp, and other low areas this time of year, is known as valley fog, and is formed primarily due to the fact that cold air is denser than warmer air. On clear calm overnights, cooler air slowly flows into low spots, like the swamp, where the temperatures can often dip ten degrees lower than surrounding uplands. On many mornings this time of year, that colder air reaches the dewpoint, which is the point at which water vapor begins to condense out of the atmosphere. Sometimes, it just creates dew, but it can also create fog at the same time.
Up here on the ridge, we’re usually left sitting above the fog, looking down on its constantly shifting patterns. I stood out behind our house the other morning snapping the accompanying photos and it was surprising how trees seemed to move in and out of the fog banks even minute to minute. And as the sun rises high enough to begin to warm the air down in the swamp, you can watch as the fog just disappears.
Looking out over the swamp from our perch on the ridge, I’m constantly amazed at the transforming panorama to our west. Sometimes, the cooler morning air in the swamp creates optical illusions, rather than fog. The layers of denser air, on occasion, act like lenses that can bend the light, sometimes appearing to levitate the horizon. On a few rare occasions, it’s given us a “lake view” as the bending light has allowed us to glimpse Little Lost Lake, a 50-acre opening in the muskeg that is normally hidden from our view by an upland island in the swamp that’s located between us and the lake.
While such strange apparitions can appear at any time, they are most common this time of year as we transition from summer to autumn. It’s the time of year I look forward to the most.