Saturday, September 15, 2007

Heat Islands

Recently Loose Baggy Monster and I moved into a new apartment. This is nothing new, in fact, it is our 11th apartment since finishing college (1998). This move has been excellent, in addition to saving money, it is a 15 minute walk from work, we have excellent neighbors, and it is a fantastic neighborhood. One thing about this neighborhood reminds me of the one I grew up in, namely that there are tons and tons of trees everywhere. Trees make anything look nicer. The move, in combination with a report I heard on NPR, inspired this post.

I grew up in Sacramento, CA. Sacramento (the political, cultural, and intellectual capital of California) is in the middle of the Great Valley of California, and during the summer it can easily top out over 100° F. But, I still consider this to be the most comfortable climate I have ever lived in (even though I never lived anywhere in Sacramento that had air conditioning). Three things make Sacramento summers beautiful: 1) It is dry, unlike my new home, where it can be 90° F and foggy, 2) The delta breeze brings cool air from the delta into the city at night, with night time temperatures often falling into the 60's with a nice wind, and 3) the trees. Sacramento [allegedly] has more trees per capita than any other major city in the world.

So that is why I got so interested in this report and associated images from a NASA pilot project looking at urban heat islands. The images below show the temperature distribution in downtown Sacramento on July 29, 1998 at 1:00 PM. According to the reports, on this day the local temperature in downtown can vary by more than 40° F. The white areas (mainly rooftops) are ~140° F, while the darker green and blue are in the high 80's and low 90's. The Sacramento River runs N-S on the left of the image, and the American River cuts across the top of the picture. The big orange-red mess in the top of the image are the railyards, and in the bottom image, you can see the State Capital and associated gardens. Obviously, the coolest areas are the parks, but what I love about this image is how nice and cool all of the tree-lined residential streets look. The NPR story also talked about Sacramento's drive to increase it's tree canopy, and the temperature reduction and associated energy savings abundant trees (and other passive heat remediation goodies like cool roofing material) offer.

Anecdotally I knew that even on hot days most of the tree-lined parts of the city stayed surprisingly comfortable, but I am even amazed at how wide the range of temperatures are here. It also made me notalgic for Sacramento summer evenings. If your only experience with Sacramento is on the interstate blowing through to the beach or to Tahoe, you have no idea what I am talking about. But if you are driving to or from Sacramento, especially from the south along I-5, you will pass hundreds of new home developments that because of both their youth and planning are not covered with trees. It kind of goes against my gut common sense to think that the downtown of a city is the coolest place to be in the summer.

No in depth analysis. I am trying to get back on the blog wagon, blogon? Anyways, a combination of lab work, paperwork, deadlines, and reviews, has taken me far away from geobloglandia.


Mrs. Sunshine said...

As one who frequently walks down the residential streets in Sacramento--even in the heat--I am very attuned to finding the shadiest side of the street for walking. In this climate, shade trees really do make a huge difference! I even try to do my street crossing where a large tree has cast a big shadow.

Anonymous said...

congrats on the move...glad you guys found a place you like...11 places in 9 years, not bad!

Brian R said...

oops...that was me above as 'anonymous'

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