Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Air Quality Worsened by Paved Surfaces

08.06.2011
New research focusing on the Houston area suggests that widespread urban development alters weather patterns in a way that can make it easier for pollutants to accumulate during warm summer weather instead of being blown out to sea.

The international study, led by the National Center for Atmospheric Research (NCAR), could have implications for the air quality of fast-growing coastal cities in the United States and other mid-latitude regions overseas.

The reason: the proliferation of strip malls, subdivisions and other paved areas may interfere with breezes needed to clear away smog and other pollution.

The researchers combined extensive atmospheric measurements with computer simulations to examine the impact of pavement on breezes in Houston.

They found that, because pavement soaks up heat and keeps land areas relatively warm overnight, the contrast between land and sea temperatures is reduced during the summer.

This in turn causes a reduction in nighttime winds that would otherwise blow pollutants out to sea.

In addition, built structures interfere with local winds and contribute to relatively stagnant afternoon conditions.

"The developed area of Houston has a major impact on local air pollution," says NCAR scientist Fei Chen, lead author of the new study. "If the city continues to expand, it's going to make the winds even weaker in the summertime, and that will make air pollution much worse."

While cautioning that more work is needed to better understand the impact of urban development on wind patterns, Chen says the research can eventually help forecasters improve projections of major pollution events.

Policy-makers might also consider new approaches to development as cities work to clean up unhealthy air.

The article will be published this month in the Journal of Geophysical Research, published by the American Geophyiscal Union.

The research was funded by the U.S. Air Force Weather Agency, the U.S. Defense Threat Reduction Agency, and the National Science Foundation (NSF), NCAR's sponsor.

"Growing urbanization and coastal zone populations in Houston and other port cities around the globe make our ability to understand and predict complex interactions between the urban canopy and local sea-breeze circulation ever more critical," says Brad Smull of NSF's Division of Atmospheric and Geospace Sciences." This study represents a significant step toward that objective."

In addition to NCAR, the authors are affiliated with the China Meteorological Administration, the U.S. National Oceanic and Atmospheric Administration and the University of Tsukuba in Japan. The research is built on a number of previous studies on the influence of urban areas on air pollution.

Houston, known for its mix of petrochemical facilities, sprawling suburbs and traffic jams that stretch for miles, has some of the highest levels of ground-level ozone and other air pollutants in the United States.

State and federal officials have long worked to regulate emissions from factories and motor vehicles in efforts to improve air quality.

The new study suggests that focusing on the city's development patterns and adding to its already extensive park system could provide air quality benefits as well.

"If you made the city greener and created lakes and ponds, then you probably would have less air pollution even if emissions stayed the same," Chen explains. "The night-time temperature over the city would be lower and winds would become stronger, blowing the pollution out to the Gulf."

Chen adds that more research is needed to determine whether paved areas are having a similar effect in other cities in the midlatitudes where sea breezes are strongest.

Coastal cities from Los Angeles to Shanghai are striving to reduce air pollution levels. However, because each city's topography and climatology is different, it remains uncertain whether expanses of pavement are significantly affecting their wind patterns.

For the Houston study, Chen and colleagues focused on the onset of a nine-day period of unusually hot weather, stagnant winds, and high pollution in the Houston-Galveston area that began on Aug. 30, 2000.

They chose that date partly because they could draw on extensive atmospheric measurements taken during the summer of 2000 by researchers participating in a field project known as the Texas Air Quality Study 2000.

That campaign was conducted by the National Oceanic and Atmospheric Administration, the U.S. Department of Energy, universities and the Texas Natural Resource Conservation Commission.

In addition to the real-world measurements, the study team created a series of computer simulations with a cutting-edge software tool, NCAR's Advanced Weather Research and Forecasting model.

Fei and his colleagues focused on wind patterns, which are driven by temperature contrasts between land and sea.

If Houston was covered with cropland instead of pavement, as in one of the computer simulations, inland air would heat up more than marine air during summer days and cause a sea breeze to blow onshore in the afternoon.

Conversely, the computer simulations showed that as the inland air became cooler than marine air overnight, a land breeze would blow offshore, potentially blowing away pollution.

In contrast, the actual paved surfaces of Houston absorb more heat during the day and are warmer overnight.

This results in stagnation for three reasons:

At night, the city's temperatures are similar to those offshore. The lack of a sharp temperature gradient has the effect of reducing winds.

During the day, the hot paved urban areas tend to draw in air from offshore. However, this air is offset by prevailing wind patterns that blow toward the water, resulting in relatively little net movement in the atmosphere over the city.

Buildings and other structures break up local winds far more than does the relatively smooth surface of croplands or a natural surface like grasslands. This tends to further reduce breezes.

"The very existence of the Houston area favors stagnation," the article states.

The study also found that drought conditions can worsen air pollution.

This is because dry soil tends to heat up more quickly than wet soil during the day. It releases more of that heat overnight, reducing water-land temperature contrast and therefore reducing nighttime breezes.

By comparing observations taken in 2000 with computer simulations of Houston-area winds and temperatures, the researchers were able to confirm that the Advanced Weather Research and Forecasting model was accurately capturing local meteorological conditions.

Media Contacts
Cheryl Dybas, NSF (703) 292-7734 cdybas@nsf.gov
David Hosansky, NCAR (303) 497-8611 hosansky@ucar.edu
Peter Weiss, AGU (202) 777-7507 pweiss@agu.org
The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2010, its budget is about $6.9 billion. NSF funds reach all 50 states through grants to nearly 2,000 universities and institutions. Each year, NSF receives over 45,000 competitive requests for funding, and makes over 11,500 new funding awards. NSF also awards over $400 million in professional and service contracts yearly.

Cheryl Dybas | EurekAlert!
Further information:
http://www.nsf.gov

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: It’s All in the Mix: Jülich Researchers are Developing Fast-Charging Solid-State Batteries

There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.

The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

A paper battery powered by bacteria

21.08.2018 | Power and Electrical Engineering

Protein interaction helps Yersinia cause disease

21.08.2018 | Life Sciences

Biosensor allows real-time oxygen monitoring for 'organs-on-a-chip'

21.08.2018 | Medical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>