Cities Influence Their Own Weather

CalamityJones writes "In the 'Well, DUH!' department, this story from the AP shrieks 'Cities May Make Their Own Weather.' As if anyone with half a brain could possibly have missed this point." Not having a weather supercomputer to crunch the numbers, it wasn't quite that obvious to me, but then what do I know. Living in Michigan I'm used to the lake effect - if I lived east of some major asphalt, I guess I'd get the L.A. effect.

Comments

Urban Greenspace

[Whyte Wolf]

A major contributing factor is that developers recklessly chop down trees to make room for suburbs, the scientists said. Trees provide shade from the heat and absorb many of the sun's harmful rays. Without them, the effect is a sort of urban desert.

I come from a very rural part of Canada--the smallest province in fact, and on Prince Edward Island we have lots of trees, and not much in the way of urban sprawl.

My first experience in the big city came quite a few years back when I moved to Calgary, Alberta, and in retrospect I feel very lucky. Calgary has an imense amount of greenspace within it's limits--heck we still see deer and get the occasional bear in the 'berbs.

However, coming from the countryside as I do, I have to say I do miss the trees. If I lived in a larger or more urban city, I'd likley have worse bouts of homesickness :)

People who grow up in cities often don't see nature the same way I do. Parks are very organized in comparison to raw Canadian wilderness. That said, I'd love to see more green in the urban landscape--and there does seem to be a larger move towards this kind of 'greening of the urban jungle.'

I remember a report several years back about a high-tech company in Toronto adding an atrium to their front lobby--one that was essentially a giant watershed (read swamp). A fascinating concept--no less than the idea of planting trees and creating parks on the roof's of office buildings.

I guess what I'm saying is that it's nice to see everyone--urban pesant and country hick living in the big city, see the benefits of greening our cities.

Maybe one more would be weather moderation. With the thunderstorm raging outside my window right now, that would be a welcome change :)

10,000 years of sheep

[Perdo]

Cities are a minor effect on the weather when it comes to man made alterations. The weather is "critically dependent on initial conditions" (chaos theory) So, to find the things that man has done you need to look far into the past and find the event with the greatest impact in its time. I believe it is sheep grazing. In Kuwait the US Army has a firing range where no Bedouin shepherds are allowed. The Impact area is verdant and lush. It looks a lot like the great plains (USA) do. Outside of the impact area sheep over graze, ripping vegetation out by the roots, leaving baked dust and sand. This has gone on for thousands of years. Kuwait is very near the Tigris and Euphrates rives, the cradle of civilization. The entire middle east is man (domestic sheep) made desert. About the time god cast man out of Eden he also decided that being a shepherd was better than being a farmer(Cain and Able). I speculate that early man even in Africa domesticated animals and possible even created the Sahara. The loss of Eden was not from god, but man destroying Eden. Cities are recent have a small effect compared to the thousands of years man made deserts have had to work their magic on the environment.

Re:I heard there was a way to minimze tornados...

[thogard]

There seems to be lots of evidence in Oklahoma that manmade stuff effects the weather. For example tornados will follow highways. A picture taken on the founding day of Ponca City shows no trees at all. The land was thick grass at the time (the bufflo had not been clearing it for years) but that was cleared to farm. The result was the dustbowl. The solution to that problem was lots of trees. In Kansas now you can see lines of trees along the edge of the farms on the section line roads. Its amazing how well a few trees stop the wind from building up. The large number of man made lakes in Oklahoma have also increased the rainfall in the area.

As far as dropping something from a plane into a tornado, I don't like the idea of that. The tops of the cloud cells that make tornados in Oklahoma are offten 50,000 ft and have large amounts of windsheer. Flying in a huracane is one thing but a tornado is just too intense. When the F15s get retired nasa may try to adapt one to radio control for just this theory but I think the current plans involve the plane not getting back.

Urban heat islands, people.

[GianfrancoZola]

The built-up area of cities produces 'islands' of higher temperatures, for a number of reasons, among which are:

Manmade materials like concrete, asphalt, bricks, etc. absorb solar energy much more readily than vegetation.

Water almost completely runs off because there's so much concrete everywhere, instead of standing around and slowly evaporating. Evaporation can make a significant contribution to cooling.

Waste heat from vehicles, residences, etc. doesn't help the situation.

Urban heat islands are pretty well understood. You can get nice images of them--temperature contrasts, that is--from AVHRR (Advanced Very High Resolution Radiometer) remotely-sensed imagery.

cf. W.B. Myer, "Urban heat island and urban health: Early American perspective", Professional Geographer 43, 1991, p. 38 if yer curious for a little more.

Throw more heat up into moist summertime air and that's a good prescription for thunderstorms.