Week of February 11, 2024 – February 17, 2024
by Elizabeth Suzedell, Environmental Educator
On a 90°F and sunny summer day, would you rather sit on black pavement or green grass? That’s a question I sometimes ask the 4th grade students in their second Nature in the City program all about energy. Many of them know that the reason pavement gets so hot (over 140°F!) is because it’s a dark color which absorbs more of the sun’s light. A city covered in pavement can have significant differences in temperature compared to a nearby rural area.
The hikes I took this week with the warmer and sunnier weather got me thinking more about the microclimates we have within Baltimore Woods. On Tuesday morning, I went out to the old gravel pit on the new property. The temperature was only in the low 30°s at local weather stations, but the warmth radiating down from the sun and up from the gravel made me forget it was still early February. Right when I stepped back into the forest, it was instantly cooler and I was stepping on crunchy leaves with a layer of frost.
As I continued through the forest, I came up to the top of a ridge that overlooks the gravel pit about 50 ft below. Despite the still air everywhere else, there was a strong breeze blowing up the steep hill to where I was standing at the top. Since warm air is less dense than cold air, it rises. The air in the gravel pit below was warm enough to rise and create the steady breeze up the hillside. I didn’t notice any more windy areas for the rest of my hike back through the woods and the field.
Thursday was a very spring-like 55°F, which was something I was pretty happy about until my winter-loving Trail School group dishearteningly reminded me that “we never get snow anymore!” As we hiked down the Valley Trail together, we noticed that the air kept getting colder and colder. Once we descended into the bottom of the valley, 200 ft below where we started, we saw snow and ice on the stream banks of Baltimore Brook. Walking over the bridge was like entering into a bubble of icy air! Because there was very little wind that day, colder and denser air was able to freely sink into the bottom of the valley. This one warm day wasn’t enough to heat up the stream water either, so it acted like an ice cube to keep it extra cool.
Baltimore Woods has a diverse set of ecosystems and geology. Its forests, streams, valleys, hills, fields, meadows, pond, and a few old (human-made) gravel pits create unique microclimates throughout the preserve. Have you noticed any different microclimates around your neighborhood?