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October 7: Hot and cool
Oct. 7th, 2010 06:52 pmI've learned an interesting thing by having an iPhone. (I know that doesn't sound very nature-y. But wait!) I'm a bit of a weather nerd, so in the Weather app, I've added a whole bunch of cities where my friends live around the world. Just because I'm interested in what their weather is like, and I'll enjoy watching the patterns and comparing through all the seasons. Of course, the first two locations I added were my own (the City) and my parents' (Hometown). Anytime I check my weather in the City, with a slide of my thumb I can check the Hometown weather at the same time.
It's usually quite similar. We're only 150 miles apart, after all, and at almost exactly the same latitude. Being in the foothills, Hometown is at a slightly higher elevation compared to the City's *thisclose*-to-the-river-delta location. So I expect it to be a couple of degrees cooler at times. What I didn't expect was a frequent 10-12 degree Farenheit difference on many nights. The temperatures will start to diverge after sunset, with the Hometown temperature dropping much more rapidly than the temperature in the City. For instance, as I'm writing this, the sun has just set, and the temperature here has cooled down one degree from the day's high. In Hometown, it's already nine degrees cooler than their high for today.
Intuitively and factually, I know that all the asphalt and concrete and glass and car exhaust and power generation in an urban area gathers and absorbs heat, and it doesn't let go of it quickly. I also know that the respiration of plants cools the places around them. So when I leave my apartment to exercise on a summer evening and during my route around the hospital complex with all of its parking lots and brick buildings and concrete sidewalks, I pass the one area with some woods and a creek... I understand why it's literally a breath of cool air. It's just been interesting to see that demonstrated with hard numbers!
Here's an interesting little article.
It's usually quite similar. We're only 150 miles apart, after all, and at almost exactly the same latitude. Being in the foothills, Hometown is at a slightly higher elevation compared to the City's *thisclose*-to-the-river-delta location. So I expect it to be a couple of degrees cooler at times. What I didn't expect was a frequent 10-12 degree Farenheit difference on many nights. The temperatures will start to diverge after sunset, with the Hometown temperature dropping much more rapidly than the temperature in the City. For instance, as I'm writing this, the sun has just set, and the temperature here has cooled down one degree from the day's high. In Hometown, it's already nine degrees cooler than their high for today.
Intuitively and factually, I know that all the asphalt and concrete and glass and car exhaust and power generation in an urban area gathers and absorbs heat, and it doesn't let go of it quickly. I also know that the respiration of plants cools the places around them. So when I leave my apartment to exercise on a summer evening and during my route around the hospital complex with all of its parking lots and brick buildings and concrete sidewalks, I pass the one area with some woods and a creek... I understand why it's literally a breath of cool air. It's just been interesting to see that demonstrated with hard numbers!
Here's an interesting little article.
Scientists have known for 200 years that the temperature in a city can be higher than that in its environs--something they learned when an amateur weather watcher detected a 1.58°F temperature difference between London and its suburbs. Modern cities, with their cars and heat-trapping buildings, can create an even bigger temperature gap, sometimes as much as 10°F.