
Urban heat islands and street trees in Philadelphia - profquail
http://urbanspatialanalysis.com/urban-heat-islands-street-trees-in-philadelphia/
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URSpider94
Hooray for GIS! It's truly amazing that in this day and age, this quality of
data, and the computing power to crunch it, is available to the average user
sitting on their couch with a laptop.

Some things I'd like to see: 1\. I've generally seen heat islands referring to
not so much getting hotter on a hot day, but staying warmer on a cold day, or
at night -- this is one reason why cities get rain when the suburbs get snow,
especially in the mid-Atlantic. Would like to test whether trees impact that.

2\. I'm concerned from a statistical perspective that trees vs. no trees could
be strongly correlated with other variables that might be more causative, like
building type and density. Would like to see a paired comparison of areas in
the city that are otherwise very similar, with the only difference being more
vs. less trees.

Not complaining at all; the author is laying out the tools. Time for me or
someone else to pick them up and investigate further ...

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jacalata
> I'm concerned from a statistical perspective that trees vs. no trees could
> be strongly correlated with other variables that might be more causative,
> like building type and density.

Wasn't that why he mentioned using the tree request program, to provide
controls?

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tedunangst
I'm a little confused. The image that's captioned "Land surface temperature,
Philadelphia" (top label: "Landsat 8 derived land temperature") is that
estimated or measured? Because it sounds like the hot spots were detected by
taking a satellite image and looking for places that "looked" hot, but then
it's presented like those places really were hotter?

A little later, he says the black warehouses were located under the really hot
spots. But weren't the really hot spots determined by finding all the black
spots in the image?

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bhousel
Landsat 8 has 11 different imaging bands, and 2 of them (bands 10 and 11) are
thermal infrared bands just for measuring heat.

For more info, see this Landsat 8 cheatsheet (written by my awesome coworker
Charlie Loyd):
[http://landsat.gsfc.nasa.gov/?page_id=5377](http://landsat.gsfc.nasa.gov/?page_id=5377)

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anc84
> Our calibration team has found that with current processing these surface
> brightness temperatures are accurate to within ~±1 K for many 15 – 35° C
> targets, e.g., growing season vegetated targets.

Wow, I would have never expected that!

Dump European question: ±1 K is the same as ±1° C, right?

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masklinn
> Dump European question: ±1 K is the same as ±1° C, right?

Yes the intervals are identical, the only difference is the scale's starting
point. In fact although that's discouraged papers often use Celsius absolutes
and Kelvin intervals, as is the case here.

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oneplane
According to this data, I don't want to live in such cities. I get that for
some people those pools of houses and people in a small area are nice, but for
me, in the information age, it doesn't make much sense anymore to live in a
crowded area with all the amplified problems people have when stacked on top
of each other.

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alistairSH
But at the same time, rural and suburban living have their own problems. You
lose economies of scale when it comes to rolling out new technology (fiber,
cable, etc). Residents have to drive more. Transportation of goods/services
costs more. Some jobs (services) require you to be on-site - straight up
software development is one of a few that doesn't require any live face-time
(but even that goes away as soon as you move into executive management or
sales).

The real answer seems to be somewhere in the middle. Well-planned urban areas
should be able to mitigate much of the heat island effect. And if the suburbs
are reigned in (and replaced with a more natural environment, with more plant-
life, etc), we should see some benefits in the overall environment.

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vanderZwan
Forests create their own microclimate that stabilises temperatures during the
day _and night_ \- meaning it doesn't cool down as quickly as an open field.
So I would expect trees to also make a city more pleasant during nighttime.

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neves
Doesn't everybody know that trees bring down the temperature?

We can resume the article in a phrase " on average, for an additional 100
trees in a census tract, land surface temperature decreases 0.3 degrees."

But it has nice graphics.

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lfowles
> Doesn't everybody know that trees bring down the temperature?

No.

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JumpCrisscross
Would love to see a similar analysis of New York City. I am working with the
City on figuring where to plant how many trees.

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kaybe
They seem to be offering their services for cases just like that, so if you
throw some money at them they will probably give you what you need.

