Wednesday, July 29, 2015

Urban warming

This morning provided proof that humans very definitely can affect the weather.

Urban warming


Overnight the temperature sank all the way to 42 in Pottstown and Millville, and 44 in Mount Holly and Doylestown.

But at Philadelphia International Airport, it didn’t get below 52.

The overnight conditions provided an almost ideal environment  for show-casing how humans can affect the overlying atmosphere.

The winds were calm, and the moonlit skies brilliant clear.

Those conditions are perfect for maximum radiational cooling. When the air is almost still and the skies clear, the days heat rapidly escapes from the Earth’s surface into space.

The escape isn’t nearly as clean in the cities. Buildings and paved surfaces are reluctant to give up their heat, warming the surrounding environment.

The effects would be most pronounced in Center City, but Philadelphia International Airport has its share of heat-absorbing structures and surfaces.

Cities can affect the environment in other ways, of course. We all know about how they intensify heat waves, and how wind gusts can funnel through urban building corridors.

Various studies have shown that cities can affect precipitation patterns. Convection is caused by the rising of warm air, and cities are low-grade hot plates.

These days, however, urban heat island research is compounded by sprawl. Mini heat islands have sprouted all over the place with development.

We can say with certainty that whatever else happens, the first frosts will coat the lawns in Philadelphia’s neighboring counties before it coats the windshields of Center City.


Inquirer Weather Columnist
We encourage respectful comments but reserve the right to delete anything that doesn't contribute to an engaging dialogue.
Help us moderate this thread by flagging comments that violate our guidelines.

Comment policy: comments are intended to be civil, friendly conversations. Please treat other participants with respect and in a way that you would want to be treated. You are responsible for what you say. And please, stay on topic. If you see an objectionable post, please report it to us using the "Report Abuse" option.

Please note that comments are monitored by staff. We reserve the right at all times to remove any information or materials that are unlawful, threatening, abusive, libelous, defamatory, obscene, vulgar, pornographic, profane, indecent or otherwise objectionable. Personal attacks, especially on other participants, are not permitted. We reserve the right to permanently block any user who violates these terms and conditions.

Additionally comments that are long, have multiple paragraph breaks, include code, or include hyperlinks may not be posted.

Read 0 comments
comments powered by Disqus
About this blog

Tony Wood Inquirer Weather Columnist
Also on
letter icon Newsletter