# Cities and weather

**URL:** <https://boards.straightdope.com/t/cities-and-weather/70406>\
**Category:** Cecil's Columns/Staff Reports\
**Created:** [June 28, 2001, 2:28am UTC](https://boards.straightdope.com/t/cities-and-weather/70406 "2001-06-28T02:28:48Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Beruang](https://avatars.discourse-cdn.com/v4/letter/b/77aa72/32.png) [@Beruang](https://boards.straightdope.com/u/Beruang)\
**Post date:** [June 28, 2001, 2:28am UTC](https://boards.straightdope.com/t/cities-and-weather/70406/1 "2001-06-28T02:28:48Z")

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I apologize if this has been covered before, but I only just ran across this info.

Way back in his very first book, Cecil discussed the impact cities have on the weather:

[http://www.straightdope.com/classics/a1\_158a.html](http://www.straightdope.com/classics/a1_158a.html)

Well, I happened to be thumbing through the July/August 2000 issue of National Wildlife(OK, so I’m a slow reader…) and found that actual brainy-type science guys have been studying the issue and have finally caught up to the where Cecil was a couple decades ago. You can find it here:

[http://www.nwf.org/natlwild/2000/nowjj0.html](http://www.nwf.org/natlwild/2000/nowjj0.html)

Urban Growth Changes Climate

Cities can create their own climates, reduce plant growth and alter local weather patterns. Those are conclusions from researchers who have studied urban and suburban sprawl using satellite images of Earth. In one of those studies, NASA researcher Marc Imhoff used satellite data, including images of city lights (below), to study what he calls the “footprint” of urban areas. “One way of looking at the reduced greenness,” he says, “is that the annual photosynthetic productivity in some areas is reduced by as many as 20 days.”

Interestingly, Imhoff also found that urban areas have longer growing seasons, likely because of the “heat island” effect that makes a city hotter than surrounding areas. Still, that’s mixed news for plants: The extra heat can impair some plant growth. Atlanta, Georgia, a well-studied heat island, is often 5 to 8 degrees F. warmer in summer than nearby rural areas. Not only that, Atlanta seems to create its own daily low pressure system that produces storms.

Now it turns out another urban product–air pollution–can prevent rainfall. In analyzing satellite images of reflected rain droplets in clouds, Israeli physicist Daniel Rosenfeld found that tiny airborne pollution particles can prevent water in clouds from developing into raindrops or snowflakes. He concludes in a recent paper in the journal Science, “Human activity may be altering clouds and natural precipitation on a global scale.”

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**Author:** ![Duck\_Duck\_Goose](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)\
**Post date:** [June 28, 2001, 9:49pm UTC](https://boards.straightdope.com/t/cities-and-weather/70406/2 "2001-06-28T21:49:28Z")

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Um. You’re saying **Cecil** discovered this 20 years ago?

Cecil quotes a scientist.

> [@](#):
>
> One of the most striking scientific demonstrations of this was a study of the so-called “La Porte weather anomaly” conducted by Stanley Changnon, an atmospheric scientist.

The “LaPorte weather anomaly” has been around for a while, I believe.

[http://www.enc.org/resources/records/full/0,1240,005396,00.shtm](http://www.enc.org/resources/records/full/0,1240,005396,00.shtm)

> [@](#):
>
> Harvesting the clouds : advances in weather modification  
> ENC#: ENC-005396  
> Series: Science study series.  
> Edition: Anchor Books edition.  
> Publisher: Anchor Books Doubleday & Company, Inc  
> Date: 1969
> 
> Grades:  
> 9 10 11 12
> 
> Abstract:  
> This series of resource books, published between 1959 and 1967 and written by prominent scientists and educator…
> 
> \<snip\>
> 
> Man, machines and the atmosphere  
> –Intentional changes of climate  
> –Unintentional changes in climate  
> –Pollution in the atmosphere  
> –The La Porte weather anomaly

[http://www.positivepractices.com/Integration/MathandWeather1996.html](http://www.positivepractices.com/Integration/MathandWeather1996.html)

> [@](#):
>
> Eichenlaub, V. (1972). The La Porte Weather Anomaly: Its Controversies and Implications . School Science and Mathematics 72 3 208-213 .

[http://www.indiana.edu/~libgm/gmthesis.html](http://www.indiana.edu/~libgm/gmthesis.html)

> [@](#):
>
> Author: Polen, Richard C.
> 
> Title: Time series analysis of stream flow in northern Indiana: A new look at the LaPorte weather anomaly.
> 
> Published: 1975.
> 
> Description: Research Paper (A.M.) Indiana University.

Changnon’s own update.

[http://www.ca.uky.edu/agripedia/aen461g/biom16.htm](http://www.ca.uky.edu/agripedia/aen461g/biom16.htm)

> [@](#):
>
> Changnon, S.A…, Jr. “More on the LaPorte Anomaly: A Review.” Bulletin of the American Meteorological Society 61 (1980): 702-711. Concludes the anomalous precipitation at LaPorte, Indiana, between late 1930’s and 1960’s was linked to urban-industrial air pollution.

Sorry to disagree, but not only have the “brainy-type science guys” not “finally caught up to Cecil”, but he was quoting from them in the first place. I would say rather that the National Wildlife magazine has finally caught up to the “brainy-type guys”. Old news, fellas. 😃  
(post edited to fix link)

[Edited by Arnold Winkelried on 06-28-2001 at 05:34 PM]