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Cold Fronts
A cold front forms when cold, dense air moves into a region that is occupied with warm, less dense air.
As a cold front moves, it becomes steeper, sometimes twice as steep as a warm front. It moves more rapidly
than a warm front, which causes it to overtake the warm front and push the warmer, moist, less dense air
upwards at a rapid speed. This can cause towering cumulonimbus clouds to form. Once the front has passed,
the temperature decreases, the wind shifts, and drier air moves into the area. Behind the front, cumulus or
stratocumulus clouds may form.
Warm Fronts
A warm front forms when warm, moist air moves into a region with cooler, drier, more dense air. The
warmer, less dense air tends to move up and over the cooler drier air, causing numerous clouds to form and
bringing precipitation. Warm fronts are usually preceded by a sequence of clouds. The first sign of
approaching warm fronts is usually the appearance of high, thin cirrus clouds. As the front gets closer, they
change into cirrostratus clouds and then into altostratus clouds. These give way to thicker stratus and
nimbostratus clouds and precipitation will begin. Warm fronts have a slower rate of movement and can
produce precipitation over a large area. Temperatures and moisture levels increase and the winds shift.
Frontal Systems
Weather Impact on Air Quality in the Hampton Roads AreaPatricia Pitton, St. Pius X School, Norfolk, VA
Mentor: Dr. M. Pippin, NASA LaRC
Towering cumulusCumulus CumulonimbusCirrus Cirrocumulus Altocumulus
Cold Front Cloud Progression
Cirrus Stratus NimbostratusCirrostratus Altostratus
Warm Front Cloud Progression
Before 1200 CE, air pollution resulted from the burning of wood, tanning hides, decaying trash, and the
smelting of ores. In as early as 3 BCE, Theophrastus, a student of Aristotle, complained of a disagreeable
smell. The Romans complained of oppressive air and made their first chimneys 7-8 m tall to avoid further
contaminating the air. There is much evidence of lead, copper, and zinc smelting which produced many
sulfides.
In the 1200-1700s, limestone kilns heated with oak to produce quicklime produced organic gases,
nitrogen oxides, carbon dioxide and particulate matter. London had a shortage of wood and used sea-coal,
which had a high sulfur content. Again, pollutants sulfur dioxide, carbon dioxide, carbon monoxide, nitrogen
oxide and particulate matter formed. In 1285, a commission was established to remedy the severe pollution,
which was causing the destruction of buildings, palaces, paintings, clothing, water bodies and plants.
In 1700-1840, with the invention of the steam engine and the Industrial Revolution, there was a massive
increase in coal combustion. It was used in manufacturing, home heating, and transportation. Many laws
were created during the 1800s, but few, if any, were enforced.
By the 1900s, ordinances existed in 175 municipalities in the United States and by the 1940s the number
had increased to over 200. Smog first appeared in Los Angeles in the 1940’s. The first state air pollution law
in the United States was adopted in 1947.
The first Clean Air Act was created in 1963 and called for research on the sources and effects of air
pollution. It was amended in 1965 to create standards for hydrocarbons and carbon dioxide. The Clean Air
Act in 1970 identified seven criteria pollutants (CO, Pb, NO2, O3 PM10, PM2.5, and SO2), and established air
quality standards.
History
Acknowledgements• This work was supported by the Long-term Engagement in
Authentic Research with NASA (LEARN) project with
funding provided through a NASA SMD EPOESS grant.
• NASA Langley
• Dr. Margaret Pippin
• Rachael Slank
• Zachary Fair
• Special thanks to Jeff Timmerman for his tremendous
technical assistance
References• Environmental Protection Agency
• Fort Air Partnership
• STORM Project Dr. Alan Czernetski
• GA Tech
• CAPABABLE website
• National Climatic Data Center
• Wunderground
AnalysisOzone (O3) is a colorless gas made up of three oxygen atoms
bonded together. It is normally found in the Earth’s stratosphere,
20-30 miles up in the atmosphere, protecting Earth from the sun’s
dangerous rays. However, when it is found near the Earth’s
surface, it is considered to be a criteria air pollutant. Tropospheric
ozone is created by reactions of volatile organic compounds
(VOCs), nitrogen oxide (NO), and nitrogen dioxide (NO2) in the
presence of sunlight. On warm sunny days the heat and sunlight
will drive the ozone levels up and the winds will disperse the
pollutants. Ozone levels start at lower levels at the beginning of
the day and increase as the day progresses.
Particulate matter (PM) is a mixture of solid particles and
liquid droplets that can be found in the air. They are inhalable fine
particles with diameters less than 2.5 micrometers or coarse
particles less than 10 micrometers. Primary particles are emitted
directly from their source-construction sites, unpaved roads, fields,
smokestacks, or fires. Secondary particles form in reactions with
sulfur dioxide and nitrogen oxides emitted from power plants,
industries, and automobiles.
As can be seen from the data above, before the front passes,
the temperatures, pressures, O3, and PM2.5 are at higher levels. As
the front passes, the pressure begins to drop, indicating the
movement of the front through the area. The O3 and PM2.5 remain
steady and begin to fall because the dropping temperatures,
rainfall, and winds begin to disperse the O3 and PM2.5. After the
front passes, the O3 levels and the PM2.5 levels decrease. As the
pressures begin to rise and the temperatures return to normal
summertime levels, the O3 and PM2.5 also begin to increase until
the next passage of a front clears the air again.
40
35
30
25
20
15
10
5
0
Te
mp
era
ture
(C
)
6/1/2011 6/11/2011 6/21/2011 7/1/2011 7/11/2011 7/21/2011 7/31/2011 8/10/2011 8/20/2011 8/30/2011 9/9/2011 9/19/2011 9/29/2011
EST
Pre-front
Frontal
Passage
Post-front
120
100
80
60
40
20
0
O3
(P
PB
)
6/1/2012 6/11/2012 6/21/2012 7/1/2012 7/11/2012 7/21/2012 7/31/2012 8/10/2012 8/20/2012 8/30/2012 9/9/2012 9/19/2012 9/29/2012
EST
Frontal
PassagePre-front
Post-front
Frontal
PassagePre-front
Post-front
August 11, 2010
Langley Research Center
Temperature
Pressure
PM 2.5
Ozone
August 27, 2011
Langley Research Center
August 6, 2012
Langley Research Center
Temperature Temperature
Pressure
OzoneOzone
PM 2.5PM 2.5
8/11/2010
1440 EST
8/11/2010
1922 EST
8/11/2010
1701 EST
8/26/2011
2338 EST
8/27/2011
1626 EST
8/28/2011
0502 EST8/06/2012
2057 EST
8/06/2012
1406 EST
8/06/2012
1627 EST
40
35
30
25
20
15
10
5
0
Te
mp
era
ture
(C
)
6/1/2012 6/11/2012 6/21/2012 7/1/2012 7/11/2012 7/21/2012 7/31/2012 8/10/2012 8/20/2012 8/30/2012 9/9/2012 9/19/2012 9/29/2012
EST
40
35
30
25
20
15
10
5
0
Te
mp
era
ture
(C
)
6/1/2010 6/11/2010 6/21/2010 7/1/2010 7/11/2010 7/21/2010 7/31/2010 8/10/2010 8/20/2010 8/30/2010 9/9/2010 9/19/2010 9/29/2010
EST
1030
1020
1010
1000
990
980
970
Pre
ssu
re (
mb
)
6/1/2010 6/11/2010 6/21/2010 7/1/2010 7/11/2010 7/21/2010 7/31/2010 8/10/2010 8/20/2010 8/30/2010 9/9/2010 9/19/2010 9/29/2010
Time (EST)
1030
1020
1010
1000
990
980
970
Pre
ssu
re (
mb
)
6/1/2012 6/11/2012 6/21/2012 7/1/2012 7/11/2012 7/21/2012 7/31/2012 8/10/2012 8/20/2012 8/30/2012 9/9/2012 9/19/2012 9/29/2012
Time (EST)
1030
1020
1010
1000
990
980
970
Pre
ssu
re (
mb
)
6/1/2011 6/11/2011 6/21/2011 7/1/2011 7/11/2011 7/21/2011 7/31/2011 8/10/2011 8/20/2011 8/30/2011 9/9/2011 9/19/2011 9/29/2011
Time (EST)
Pressure
120
100
80
60
40
20
0
PM
2.5
(U
G/M
3)
6/1/2010 6/11/2010 6/21/2010 7/1/2010 7/11/2010 7/21/2010 7/31/2010 8/10/2010 8/20/2010 8/30/2010 9/9/2010 9/19/2010 9/29/2010
EST
120
100
80
60
40
20
0
PM
2.5
(U
G/M
3)
6/1/2012 6/11/2012 6/21/2012 7/1/2012 7/11/2012 7/21/2012 7/31/2012 8/10/2012 8/20/2012 8/30/2012 9/9/2012 9/19/2012 9/29/2012
EST
120
100
80
60
40
20
0
PM
2.5
(U
G/M
3)
6/1/2011 6/11/2011 6/21/2011 7/1/2011 7/11/2011 7/21/2011 7/31/2011 8/10/2011 8/20/2011 8/30/2011 9/9/2011 9/19/2011 9/29/2011
EST
120
100
80
60
40
20
0
O3
(P
PB
)
6/1/2011 6/11/2011 6/21/2011 7/1/2011 7/11/2011 7/21/2011 7/31/2011 8/10/2011 8/20/2011 8/30/2011 9/9/2011 9/19/2011 9/29/2011
EST
120
100
80
60
40
20
0
O3
(P
PB
)
6/1/2010 6/11/2010 6/21/2010 7/1/2010 7/11/2010 7/21/2010 7/31/2010 8/10/2010 8/20/2010 8/30/2010 9/9/2010 9/19/2010 9/29/2010
EST