This is to minimize the problems of desire paths. I'd prefer to not have a dirt path carved through the lawn.
Rabu, 17 Oktober 2012
Just what is that flag barrier for?
Some people might have noticed that there has been a ribbon fence erected in the front yard.
This is to minimize the problems of desire paths. I'd prefer to not have a dirt path carved through the lawn.
This is to minimize the problems of desire paths. I'd prefer to not have a dirt path carved through the lawn.
Selasa, 16 Oktober 2012
SNREds in the forest
Today, Prof. Wiley's wetlands practical class came out to Saginaw Forest to look at the wetlands found on the property. Hopefully, the class will return in future years!
Jumat, 12 Oktober 2012
SNRE Campfire Tonight!
This will be the fourth campfire for which I will be the on-the-ground organizer (you know, because I'm the caretaker). The campfire is part of the University of Michigan's School of Natural Resources and Environment's Homecoming celebrations. We're expecting to have a handful of 1962 alumni at the event, in addition to the local alums who are interested in showing up and showing how things are done. Events like this always seem to gel at the last minute (much like a good souffle), but since tonight is the night, I haven't any photos from this year's campfire.
However, this is a photo from my first year as caretaker (2009). That year, the Campfire was on October 1, 2009, and - as you can see - the trees on the far side of the lake hadn't quite turned yet.
Hopefully, it will be a great Campfire event.
However, this is a photo from my first year as caretaker (2009). That year, the Campfire was on October 1, 2009, and - as you can see - the trees on the far side of the lake hadn't quite turned yet.
Hopefully, it will be a great Campfire event.
Rabu, 10 Oktober 2012
Why does mist rise from the lakes in the morning?
During the fall, there many morning when Third Sister Lake produces gouts of mist and steam:
What's going on here? Obviously, the lake is not boiling, and - obviously - there isn't a general fog blanketing the entire forest, so why does the lake look like a pot on the stove? Well, it's due to many of the same principles of what happens when water boils in a pot on the stove, namely evaporation and condensation, but you have to think of these things in terms of heat energy and NOT in terms of water temperature alone.
In the case of boiling water on a stove, water is heated, causing evaporation; the gaseous water requires a certain amount of heat energy to maintain its gaseous state, and if the heat energy of the gaseous water falls below the condensation point, it turns back into liquid water, forming a fine mist. The mist increases in density as the amount of condensing water increases. This is why you see more and more steam rising from a pot of water as it reaches boiling point.
However, it's not only the temperature of the water that you have to consider when thinking about steam formation. In addition to the process of condensation described above, there is also the humidity to consider. In other words, the air itself can only "hold" a certain amount of gaseous water, and this capacity is determined by the temperature of the air; the higher the air temperature, the more water can be held as a gas. This is why there's a lot more steam seen above a pot boiling in very humid conditions than in very dry conditions (even when the air temperatures are identical).
In the case of misty lakes in the morning, all these processes are happening, just like in the example of the boiling pot, except the temperatures are far lower. Throughout the summer, the lake has absorbed and retained a large amount of heat energy in the top layer of the lake. At night -- especially on cloudless nights -- the heat energy in the air rises away from the surface and escapes this local system, thus bringing down the temperature. There is evaporation taking place in the lake, both day and night, thanks to the higher temperatures of the surface of the lake. However, unlike during the heat of the day, at night, since there is a lower temperature, there is less capacity for the air to hold on to gaseous water, and we can measure this as an increase in humidity. As the humidity rises to 100%, the air has a diminishing capacity to hold on to all the water that is evaporating -- due to the heat of the water in the lake -- and so the water almost immediately condenses into mist as it rises from the lake. In fact, if you heat a pot to the same temperature of the lake water, you would see steam flowing up from your pot, even though the water temperature is nowhere near boiling.
Once the sun's rays strike the surface of the water, the humidity is "burned away", in that the local temperature increases enough so that the humidity drops below 100%, thus allowing the air to once again absorb the evaporating water.
Of course, the reason why the lake effectively billows with steam during early fall mornings is due to the relatively large amount of heat stored in the lake combined with one or two significantly cold mornings. The photo above was taken on September 24, 2012, and if we look at the weather conditions measured at the Ann Arbor airport (about five miles away), we see that the overnight temperature dropped to freezing, and the humidity was near saturation. (Of course, this was in an open field, not above a lake, where the saturation would have been 100%.)
Yeah, okay, so this was a bit of a rambling post, but I hope that it helped you understand (if you didn't already) why so much mist rises off the lake on cool autumnal mornings. Of course, there is little reason to necessarily understand the why in order to appreciate the effect. In the end, fall is a veritable feast of sights, just like spring was one of smells, and summer one of sounds.
What's going on here? Obviously, the lake is not boiling, and - obviously - there isn't a general fog blanketing the entire forest, so why does the lake look like a pot on the stove? Well, it's due to many of the same principles of what happens when water boils in a pot on the stove, namely evaporation and condensation, but you have to think of these things in terms of heat energy and NOT in terms of water temperature alone.
In the case of boiling water on a stove, water is heated, causing evaporation; the gaseous water requires a certain amount of heat energy to maintain its gaseous state, and if the heat energy of the gaseous water falls below the condensation point, it turns back into liquid water, forming a fine mist. The mist increases in density as the amount of condensing water increases. This is why you see more and more steam rising from a pot of water as it reaches boiling point.
However, it's not only the temperature of the water that you have to consider when thinking about steam formation. In addition to the process of condensation described above, there is also the humidity to consider. In other words, the air itself can only "hold" a certain amount of gaseous water, and this capacity is determined by the temperature of the air; the higher the air temperature, the more water can be held as a gas. This is why there's a lot more steam seen above a pot boiling in very humid conditions than in very dry conditions (even when the air temperatures are identical).
In the case of misty lakes in the morning, all these processes are happening, just like in the example of the boiling pot, except the temperatures are far lower. Throughout the summer, the lake has absorbed and retained a large amount of heat energy in the top layer of the lake. At night -- especially on cloudless nights -- the heat energy in the air rises away from the surface and escapes this local system, thus bringing down the temperature. There is evaporation taking place in the lake, both day and night, thanks to the higher temperatures of the surface of the lake. However, unlike during the heat of the day, at night, since there is a lower temperature, there is less capacity for the air to hold on to gaseous water, and we can measure this as an increase in humidity. As the humidity rises to 100%, the air has a diminishing capacity to hold on to all the water that is evaporating -- due to the heat of the water in the lake -- and so the water almost immediately condenses into mist as it rises from the lake. In fact, if you heat a pot to the same temperature of the lake water, you would see steam flowing up from your pot, even though the water temperature is nowhere near boiling.
Once the sun's rays strike the surface of the water, the humidity is "burned away", in that the local temperature increases enough so that the humidity drops below 100%, thus allowing the air to once again absorb the evaporating water.
Of course, the reason why the lake effectively billows with steam during early fall mornings is due to the relatively large amount of heat stored in the lake combined with one or two significantly cold mornings. The photo above was taken on September 24, 2012, and if we look at the weather conditions measured at the Ann Arbor airport (about five miles away), we see that the overnight temperature dropped to freezing, and the humidity was near saturation. (Of course, this was in an open field, not above a lake, where the saturation would have been 100%.)
Yeah, okay, so this was a bit of a rambling post, but I hope that it helped you understand (if you didn't already) why so much mist rises off the lake on cool autumnal mornings. Of course, there is little reason to necessarily understand the why in order to appreciate the effect. In the end, fall is a veritable feast of sights, just like spring was one of smells, and summer one of sounds.
Peak fall colors
I think that this is the day when the fall colors are likely the best:
It's all "downhill" toward winter now.
It's all "downhill" toward winter now.
Minggu, 07 Oktober 2012
Fall colors in the forest
Slowly changing colors in the forest near the Lib-Wag parking lot.
Fall colors emerging beyond the green foliage.
Red maple leaves.
The buckthorn and honeysuckle are the only things that remain in full leaf.
Sabtu, 06 Oktober 2012
SNRE Campfire is coming...
This coming Friday, October 12, is the SNRE Campfire. This will be the 106th* celebration of the school out in Saginaw Forest, ever since the celebration of "field days" began in 1906.
In preparation for the event, I cleaned up the base of the fire-pit (removing the dirt and grass that had built up over the years),
had a lot of the ash wood and pine wood that was lying around brought in,
carried over a log for the cross-cut saw competition,
and chopped wood for the campfire.
The deliveries of straw bales, pumpkins, event tent & tables, port-a-johns, and trash cans are due to come later in the week.
* I am making the assumption that the School of Forestry continued the tradition during the US involvement in the two World Wars (i.e., 1917-1918 and 1941-1945).
In preparation for the event, I cleaned up the base of the fire-pit (removing the dirt and grass that had built up over the years),
had a lot of the ash wood and pine wood that was lying around brought in,
carried over a log for the cross-cut saw competition,
and chopped wood for the campfire.
The deliveries of straw bales, pumpkins, event tent & tables, port-a-johns, and trash cans are due to come later in the week.
* I am making the assumption that the School of Forestry continued the tradition during the US involvement in the two World Wars (i.e., 1917-1918 and 1941-1945).
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