SUMMER
WEATHER CAN PROMOTE POOR AIR QUALITY –
NOAA’S AIR QUALITY FORECAST GUIDANCE HELPS PREDICT IT
May
14, 2007 — In many parts of the country, the arrival of summer signals
the start of air pollution season. Fortunately, the NOAA
National Weather Service’s air
quality forecast guidance, produced in partnership with the U.S. Environmental
Protection Agency, helps provide air quality forecasters and the public
with information on predicted air quality conditions they need as they
plan their daily activities.
NOAA’s
involvement in air quality forecasting stems from the fact that air
quality and weather go hand
in hand. Weather can promote both the formation or degradation of various
airborne pollutants and can disperse/transport them from one part of the
country to another, thus making air quality a national issue.
“You
can not accurately predict air quality without taking into account weather
— and that is exactly what NOAA’s air quality forecast guidance
does,” said Paula Davidson, manager for the NOAA National Weather
Service’s Air
Quality Forecasting program in Silver Spring, Md. “Measuring
air pollution alone does not tell you very much about how it will change
over the next few days, but by taking into account meteorological conditions
such as wind, temperature, humidity, precipitation and cloud cover you
gain a much better understanding of how and why air quality varies day
to day.”
Benefits
of Air Quality Forecasting
Air Quality forecasting is especially important to those who
are most susceptible to air pollution. (Click NOAA aerial image
for larger view of the Ghent Power Plant, in Ghent, Ky., taken aboard
a NOAA hurricane hunter aircraft in 1999. Click here
for high resolution version. Please credit “NOAA.”)
“For
many individuals — especially sensitive groups including children,
the elderly, and those who suffer from asthma and other respiratory/cardiovascular
problems — knowing forecast levels of pollution can make a significant
difference in the quality of their lives and how they plan their daily
activities,” said Scott Jackson, environmental scientist at EPA's
Office of Air Quality Planning and Standards in Research Triangle Park,
N.C. “Those susceptible to poor air quality may need to modify their
behavior and take precautionary measures, like limit strenuous outdoor
activities, to protect themselves when Air Quality Index levels are high.”
WHAT
YOU CAN DO TO MAKE THE AIR CLEANER?
You
can help reduce pollution in your community by following these EPA-recommended
guidelines:
-
Choose a cleaner commute — share a ride to work or use public
transportation.
- Combine
errands and reduce trips.
-
Delay using gasoline powered lawn and garden equipment until later
in the day or wait until days when the air quality is better,
or avoid using them altogether.
- Avoid
burning leaves, trash and other materials.
- Get
regular car engine tune ups and replace your car's air filter
and oil regularly.
- Change
spark plugs on recommended maintenance schedule.
-
Limit engine idling.
- Reduce
fireplace and wood stove use.
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High concentrations
of fine particles in the air and ground-level ozone cause respiratory
and cardiovascular problems, contributing to tens of thousands of premature
deaths annually. However, it has been estimated that for each one percent
reduction in adverse health impacts that air quality forecasting could
provide, more than one billion dollars could be saved every year.
Weather’s
Impact on Air Quality
Air quality results from complex chemical and spatial interactions between
many variables in the atmosphere, as well as the direct emission of both
natural and man-made pollutants into the air. As a result, air quality
varies widely depending on your local topography, how much air pollution
is emitted or carried into your community, and by weather conditions.
“There is both cold-versus-warm season air quality and east-versus-west
air quality,” said Clinton MacDonald, manager/air quality forecaster
at Sonoma Technology, Inc. in Petaluma, Calif., and a contractor working
with NOAA on air quality issues. “Although both the East and West
coast experience ozone pollution in the summer months, particle pollution
is interestingly absent for many western states in the summer because
the type of fossil fuels burned in this region of the county release less
sulfur containing compounds. In the winter, however, particle pollution
returns to the western states in the form of smoke from wood-burning stoves,
and other particles formed from emissions of ammonia, nitrogen oxides
(NOx), and volatile organic compounds (VOCs).”
Ironically
the same weather conditions that draw us outside in the summer (sunny
skies, warm temperatures, low humidity and light winds) also promote air
pollution and make it stagnate. Sunlight and heat, for example, promote
ozone formation, as well as particle pollution. Conversely, weather conditions
that make us want to stay inside (precipitation, cold temperatures and
strong winds), clear pollutants from the air.
As you can see from the image of Hurricane
Ophelia to the right, strong winds and rain clear away poor air quality,
while airborne pollutants can accumulate on the leading edge/peripheral
feeder bands where the skies are clear and winds act to trap pollutants.
(Click NOAA image for a larger/animated view of air quality forecast
guidance during Hurricane Ophelia in 2005. Please credit “NOAA.”)
“Forecasting
air quality for any area when a hurricane
— or the remnants of a hurricane — is approaching can be tricky,”
said Bill Murphey, chief meteorologist with the Georgia Department of
Natural Resources. If a hurricane comes up from the Gulf of Mexico into
Georgia, it can actually help to clear out air pollution from the area.
But if the hurricane is moving up the Atlantic coast and you are on the
subsident (or dry air) side of the tropical system, you often see an increase
in air pollution — especially ground-level ozone.”
Weather can also affect how quickly pollutants move or are dispersed away
from an area. Normally, pollutants rise or blow away from their sources
without building up to unsafe levels. But imagine what would happen if
the air became trapped and built up to unhealthy levels. This happens
when winds are unusually light or during an inversion,
when warm air moves in over the top of cold or cooler air, pinning it
and airborne pollutants against the ground. Inversions can also occur
on clear summer nights and can affect the next day's ground-level ozone
concentrations.
“Geography can also affect air pollution. Mountain ranges surrounding
a valley, such as those in southern California, can prevent pollution
from dispersing,” said Bill Ryan, air quality forecaster and faculty
research assistant at Penn State University in University Park, Penn.
On the other hand, pollution is much more easily transported across state
boundaries in the Midwest and East coast where the terrain is flatter
and less complex.”
Major Airborne Pollutants
“Ground-level ozone and particle pollution are the two main pollutants
that are forecast and reported with the Air Quality Index,” said
Jackson.
Ground-level ozone forms when two key pollutants, NOx and VOCs “cook
in the sun” at warm temperatures. Ozone also exhibits a relatively
consistent diurnal (daily) pattern since it forms throughout the day and
slowly breaks down in the evening when the sun goes down.
Ozone can also be transported easily by the wind from one location to
another making it a poor air quality concern to not only urban areas,
but also surrounding suburban and rural areas.
Particle pollution, on the other hand, can either be directly emitted
(e.g., smoke from a wood stove) or generated when gases and/or other aerosols
react in the air. Nitrogen oxides and sulfur dioxides contribute to particle
formation.
These ozone and particle-forming pollutants come from a wide variety of
sources, including automobiles, power plants and industries. Natural sources
also contribute — wildfires and volcanoes contribute to particle
pollution, while trees
and other vegetation can contribute to both particle and ozone pollution.
NOAA’s
Air Quality Forecast Guidance
NOAA’s
air quality forecast guidance, produced twice a day from the NOAA
National Centers for Environmental Prediction in Camp Springs, Md.,
helps local air quality forecasters by providing detailed hour-by-hour
predictions, at high spatial resolution, of ground-level ozone across
their communities. State and local air quality forecasters in more than
300 cities nationwide, use NOAA’s air quality forecast guidance
and real-time weather and air quality observations to make forecasts.
(Click NOAA image for larger view of sample air quality forecast
guidance. Click here
for high resolution version, which is a large file. Please credit “NOAA.”)
Unlike previous
air quality forecasts that were worst-case, next-day air quality forecasts
for a single city based on simple statistical techniques, NOAA’s
air quality forecast guidance gives information for those in cities and
suburbs alike, for all hours of the day and night.
"A new tool for air quality prediction is NOAA's recently implemented
Smoke Forecast
Tool. Like NOAA’s ground-level ozone forecasts, this tool improves
forecasters’ ability to predict the onset, severity and duration
of smoke particle pollution in the air we breathe," said Davidson.
"This tool takes into account the smoke from burning fires detected
in NOAA satellite imagery
and its interaction with local and regional weather conditions."
Smoke particles
contribute to the total mix of particle pollutants, and near fires they
can become the dominant contribution to particle pollution. A striking
example can be seen in the figure to the right, where smoke from wildfires
in Georgia and Florida, interacted with Tropical Storm Andrea off the
coast of Florida on May 10, 2007 (the forecast is for May 11). (Click
NOAA image for larger view of NOAA's smoke forecast for May 11, 2007.
Please credit “NOAA.”)
Because particle
pollution is responsible for as many as 40,000 premature deaths each year,
knowing when and where to expect harmful concentrations of smoke particles
will help people to take steps to limit their exposure.
Relevant
Web Sites
NOAA
National Weather Service Air Quality Program
Understanding
Air Quality
NOAA's Weather and
Air Quality Research
NOAA's
Program Charter for Air Quality
Air
Quality Forecast Guidance Capabilities Fact Sheet
Media
Contact:
NOAA
National Weather Service Public Affairs, (301) 713-0622
Article by Julie Bedford (Editor, NOAA Magazine)
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