IJMC Back With the Wind

                     IJMC - Back With the Wind

What do you want me to say? I mean, the International Junk Mail 
Clearinghouse cannot die...just disappear for long periods of time. Yep, 
back again. Who knows, if Smirnoff is as strong as its namesake, we could 
have a stable server again. Will a stable server help? Ask me again in a 
few months...we shall see. Anyway, welcome back. Er, well, whatever. Hi 
folks...dave is here once more. Rejoice! Jump for joy! And to all of you 
who wrote, ICQ'd, sent smoke signals, many thanks. Is all good.     -dave

Scientists Watch Cities Make Their Own Weather

August 15, 2000

Atlanta is so big and hot that it makes its own weather, and scientists
have the pictures to prove it. 

While analyzing weather data that was collected during the 1996 Summer
Olympics, Dr. Robert Bornstein, a professor of meteorology at San Jose
State University in California, saw a pattern in the winds. 

The heat-absorbing roofs and pavement were warming the air, and the hot
air was rising, sucking air from all directions into the city. Dr.
Bornstein surmised what was happening next:  as the warm air rose, it
cooled, condensing into clouds and rain. 

Satellite images backed him up, revealing several instances in which
thunderstorms erupted over Atlanta, seemingly out of nowhere, and dumped
rain on the city, usually at its southeast and northeast edges. 

"We documented all the steps in the sequence," Dr. Bornstein said. In the
satellite images, he said, "you will not see any other clouds upwind or

The idea that cities generate their own heat, and alter their climates as
a result, is not new. Dr. Bornstein observed similar thunderstorms
appearing over New York City more than two decades ago based on radar
images, and other cities probably create their own storms, too. 

But in recent years, scientists using high-tech sensors have produced a
more detailed picture of how human activities change the weather. 

Over the past four years, researchers from the NASA Marshall Space Flight
Center in Huntsville, Ala., have flown jets equipped with infrared cameras
over Salt Lake City, Sacramento, Baton Rouge, La., and Atlanta, producing
block-by-block temperature maps. Parks were cool -- plants are full of
cooling water, and trees also provide shade -- while asphalt parking lots
were hot. 

Surprisingly, though, the hottest buildings were often the newest. In Salt
Lake City, the Scott M. Matheson Courthouse, a dark-roofed building that
opened a couple of years ago, is a white-hot splotch in the infrared
photograph, suggesting a roof temperature of about 170 degrees Fahrenheit. 
Across the street to the east, the century-old, castle-like City and
County Building is a relatively cool red. 

In the era of universal air-conditioning, builders may have focused more
on durability and cost of roofs than on their ability to absorb or reflect

"We don't necessarily think about making things cool because everything is
air-conditioned," said Dr. Dale A. Quattrochi, a senior scientist at
Marshall and co-leader of the NASA heat island research. 

Moreover, the heat-island effect is growing as suburbia expands. For
instance, Atlanta's urban heat island now covers at least 17 square miles. 

"It's a semicultural mindset change." Dr. Quattrochi said. "We start
paving over things and we start cutting down trees." 

The NASA team expects to turn its infrared cameras on Houston as soon as
next week, as part of a larger effort by Texas and federal agencies to
track smog there. More heat speeds the chemical reactions that create
ozone, the primary component of smog. 

"One of things that's interesting about Houston is it is an extremely
large city in terms of the built-up area," Dr. Quattrochi said. At 572
square miles, he said, "It's going to be the largest urban area we've
studied to date." 

Unlike other cities, Houston does not have zoning laws, and its
industrial, commercial and residential buildings are all mixed together. 

By comparing data from the different cities, the NASA researchers want to
better understand how the heating effect differs among different urban

The heat-island effect was first recorded almost 200 years ago, by Luke
Howard, an amateur meteorologist in England. 

Beginning in 1807, he started comparing temperatures from several sites
within London with those measured a few miles beyond the city's edge. 

"Thus," Howard wrote in his book, "The Climate of London" in 1818, "under
the varying circumstances of different sites, different instruments, and
different positions of the latter, we find London always warmer than the
country, the average excess of its temperature being 1.579 degrees." 

Today, average temperatures in the largest cities can range 5 to 10
degrees Fahrenheit hotter than surrounding areas. 

Besides discomfort, the added heat also increases the need for
air-conditioning, which in turn contributes to other air quality problems.
The laboring air-conditioners consume more electricity, which causes
nonnuclear power plants to spew out more of the chemical ingredients for
the making of ozone. 

But once made, these effects can be unmade. In a 1998 study, scientists at
Lawrence Berkeley Laboratory in Berkeley, Calif., concluded that residents
and businesses in the New York City area could cut their summertime
air-conditioning costs by $22 million by swapping dark roofs with more
reflective ones. Outdoor summer temperatures could also drop a couple of

On the other hand, the reflective roofs would raise heating bills by $6
million in winter. "In the wintertime, you want the roof to be hot," said
Steven Konopacki, staff research associate at Lawrence Berkeley and a
member of the heat island research group. Still, the net savings would be
$16 million a year. 

And the benefits cascade. According to the computer simulations, a drop in
temperature of a couple of degrees can reduce levels of ozone "on the
order of 5 percent to 10 percent, sometimes up to 20 percent," said Dr.
Haider Taha, a Lawrence Berkeley scientist. "You slow down the cooking
rate of smog." 

Lawrence Berkeley researchers are also working on making lighter-colored
asphalts and roof shingles that come in different colors but that
efficiently reflect infrared light. 

One reason black roofs dominate the urban landscape is that they cost
less. "Some bad habits have developed, at least in the States," Mr. 
Konopacki said. 

But reduced electric bills could more than offset the initial difference
in price. Mr. Konopacki cited a medical office building in Davis, Calif.,
that had a "typical commercial building roof," reflecting about 24 percent
of the sunlight that hit it.  When the roof needed to be replaced in 1997,
the Berkeley researchers persuaded the building owner to use a white roof
that reflected 60 percent of the sunlight. Air-conditioning costs dropped
18 percent. 

The NASA and Berkeley researchers hope the data will catch the attention
of architects and builders. 

"Historically, that hasn't been part of their curriculum," said Dr.  Jeff
Luvall, who runs the NASA heat island research program with Dr. 
Quattrochi. "They're looking at aesthetics and budgets." 

Georgia has revised its building code for commercial buildings to
encourage the use of reflective roofs, and counties around Atlanta have
passed or are considering ordinances to preserve remaining trees. 
Fifty-three roofing products now carry the federal Environmental
Protection Agency's Energy Star label, which indicates that the roofs will
reflect at least 65 percent of the sunlight when new and at least 50
percent three years later. 

Some sellers of reflective roofing, like Craig Lease of the Stockton
Roofing Company in California, include NASA images in their sales
materials. "When you can back up your words with NASA data," Mr.  Lease
said, "people listen." 

IJMC September 2000 Archives