Contrails and Aviation-cirrus
Airpollution and Rainfall (01)
Smoggy Skies, Soggy Skies.
Two ASU climatologists have discovered a link between air pollution and weather patterns on the Atlantic coast of North America. It seems that car exhaust and factory smoke produced during the week may lead to a pattern of rainy weekends.
To get their results, Randy Cerveny and Robert Balling, Jr. studied daily carbon monoxide and ozone measurements collected at a Canadian monitoring station located on an island off the coast of Nova Scotia. Carbon monoxide and ozone are two common air pollutants.
They also studied rainfall data gathered by weather satellites in orbit over the Atlantic Ocean, and information stored in databases of Atlantic hurricane measurements. They found that weather on the East Coast of the United States is likely to be rainy on weekends and clear during the week. They also found that pollution hits its highest levels at the end of the week—possibly causing the weekend showers. “The dirt and dust, the solid parts of the pollution, tend to absorb heat. That makes the air around those parts warmer. Warm air rises. As warm air rises, it tends to cause clouds and precipitation,” says Cerveny, an ASU professor of geography.
The researchers believe the seven-day pollution pattern is caused by the human work week, because nothing in nature follows a seven-day cycle. The seven-day week is a purely human creation. Not surprisingly, activities that cause pollution tend to happen on weekdays, so it makes sense that pollution levels peak at the end of the week.
“[Pollution] primarily comes from auto exhaust and from factories. It’s the nasty stuff that helps to create the brown cloud we see over Phoenix,” Cerveny says. Balling and Cerveny also found a link between pollution patterns and hurricanes. Weekend hurricanes tend to be much weaker than storms that occur Monday through Friday. Hurricane wind speeds can drop by 10 miles-per-hour on the weekend, knocking them down a whole category on the Saffir Simpson Scale, a tool used by scientists to rate the strength of hurricanes and other cyclonic storms.
Cerveny and Balling only studied the Atlantic coast. As western cities grow, some people wonder whether or not their weekends might get wetter as well. Cerveny doubts it. “Winds flow from west to east,” he says. “While it is possible that pollution from areas in southern California may affect our weather here [in Arizona], it’s unlikely to affect the West Coast.”--Diane Boudreau
For more information, contact Randy Cerveny, Ph.D., or Robert Balling, Jr., Ph.D., ASU Office of Climatology, 480.965.6265. Send e-mail to Cerveny at email@example.com or to Balling at firstname.lastname@example.org
Publication date: Spring 1999
Studying Ship Tracks
Throughout most of the twentieth century, the scientific community was only certain about a few basic facts regarding cloud formation. They knew that in order to form, clouds require water vapor as well as tiny microscopic particles (aerosols) from the surface of the Earth. When water evaporates into the atmosphere, it spreads evenly throughout the surrounding air often to the point where the relative humidity is greater than 100 percent. Aerosols that dissolve easily in water, such as ammonium sulfate and sea salt, give the excess water molecules something to cling to. These aerosols act as the nuclei, or "seeds," around which cloud droplets take shape, and together these droplets form clouds. Were it not for particles in our atmosphere, the sky would almost always be clear and the air around us thick and humid (King et al., 1995). Many researchers suspected that as the concentration of these particles increases, the properties of the cloud could change. However, they remained unclear on exactly what these changes would be, the effects aerosols could have on rainfall, and most importantly where aerosol particles come from. Many believed that humans produce a large number through the burning of fossil fuels and plants (biomass). In the late 1980s and early 1990s, a series of investigations on the exhaust from ship’s smokestacks answered some of these questions. Not significant sources of pollution themselves, ships burn fossil fuels and release their exhaust in the form of sulfur dioxide, a gas that leads to the formation of sulfate aerosols in the atmosphere. The exhaust produces clouds that are relatively low in elevation and resemble larger versions of airplane contrails. Unlike contrails, these "ship tracks" are ideal for study since they remain in the air for many hours and are surrounded by relatively pristine marine air (King et al., 1993). Initially, the ship tracks were used to see if an increasing number of aerosols from pollutants would make the clouds brighter. The scientists believed the additional aerosols from the ships would give the water vapor more nuclei to cling to, so that a greater number of smaller drops would form in the cloud. These smaller drops, in turn, would make the cloud more reflective to sunlight. The same phenomenon can be seen when ice cubes are crushed. As the ice is broken up, the once smooth surface is shattered into many tiny surfaces at varying angles. These tiny surfaces reflect incoming light in all directions and cause the crushed ice to appear white and opaque. Water droplets do not contain all these ridged surfaces, but the researchers were fairly sure their fragmentation would have a similar effect. Through satellite observation and in situ aircraft measurements, scientists not only showed that their hypothesis was correct, but they also came across an effect that no one had foreseen. In addition to making the clouds more reflective, the aerosols were causing them to retain water and to stop drizzling. The cloud seeding by the ships’ exhaust made the droplets so small that they could no longer easily merge together to reach the size needed for gravity to pull them to the ground. Since no drizzle came out of the seeded clouds, the cloud water just kept building up (King et al. 1995).
A layer of haze blankets the city on a hot summer day, blurring the Tulsa skyline. A trail of exhaust smoke spews out from the tailpipe of the car in front of you on your way to work. Clouds of smoke billow from an industry.
What do these images have in common? Tiny particles, called "fine particulates." Soiling the air, spoiling the view and taking our breath away. Literally.
Ever since our early ancestors gathered around their first fire, humans have been releasing fine particulates into the air. Only recently have scientists discovered the bad news: fine particulates are so small that they can easily be inhaled into the deepest reaches of our lungs, causing serious lung and heart disease. Fine particulates are also a visual blight, capable of reducing visibility so much that beautiful views are blotted out.
Hold on a moment! Human beings have managed to live with fine particulates for thousands of years, haven't they? Why all the fuss now?
Well, the truth is that lung disease has always been a major health problem throughout the world, and a leading cause of death. Just as bacteria were causing serious illness long before they were discovered, it's likely that fine particulates have always contributed to lung disease. We just didn't know it.
Recent studies have found that fine particulates at current levels can pose a greater danger to our health than the better-known kinds of air pollution, such as smog, sulphur dioxide and carbon monoxide. Fine particulates are linked with all sorts of health problems — from a runny nose and coughing, to bronchitis, emphysema, asthma and even death.
It's time to take
care of our air! To take action to control fine particulates, we need to
understand the nature of the problem. This site will introduce you to
fine particulates: what they are, where they come from and why they are
so effective at impairing breathing and visibility. It will also explain
what the government is doing to get fine particulates out of the air.
Global Problems Due to Particulates
Particulates also cause global problems such as suppression of rainfall and supplying transport for chemicals harmful to our atmosphere. Particulates serve as cloud condensing nuclei (CCN), which means that they attract water in the atmosphere and help form clouds. This may sound like a good thing but particulate CCN form clouds very inefficiently, they reduce the size of cloud droplets, but increase the density of droplets in the cloud. The overall effect of these CCN particulates is a suppression of rainfall over regions of high pollution. It is unknown at this time if these CCN particulates reduce the amount of rainfall on a global scale.
Our atmosphere is like a giant reactor where hundreds and hundreds of
reactions occur every second. Particulates carry chemicals that
disrupt the balance of the atmospheric chemistry and chemicals that can
block solar energy from entering or leaving the earth. For
example, the "hole" in the ozone layer isn't actually a hole,
but a region over Antarctica where the ozone is greatly depleted due to
aerosols formed in high clouds (aerosols are basically another name for
particulates). During the sunless winter, a giant vortex of air
forms over the Antarctic, pollution from all over the globe is drawn
towards the vortex. Large concentrations of photo-chemical species
build up in the vortex. These chemical species are ozone
depleting, but require sunlight to deplete the ozone. When
sun starts to reach the Antarctic after winter, the large buildup of
ozone-depleting species rapidly deplete the ozone causing the
"hole" in our atmosphere. This is just one example of
how particulates affect our atmosphere. The atmospheric chemistry
is very complex and the long term effects of particulates are largely
unknown, but we can see the short-term results everyday through smog and
current health problems.
On a soggy morning this past April, Daniel Rosenfeld moved briskly through an overcast parking lot into one of many monolithic brick structures that dot NASA’s Goddard Space Flight Center. When he arrived at the conference room, he switched on a laptop and began bringing up satellite images of what looked like an apocalyptic vision of the East Coast. From Massachusetts to North Carolina, swirling red, orange and yellow clouds floated above a blue landscape.
Peering over his glasses
and intently at the screen, he pointed to an especially fiery spot on
the map near the border of Pennsylvania and New Jersey. "The
atmosphere here is fully polluted," he said. "Those colored
streaks are mostly due to man-made aerosols."
Dirty Clouds Heat up the Atmosphere and Raise Objections (5/12/03)
Brown clouds of soot, apparently created by dried-dung fires on the Indian continent, have blown 1000 miles out over the Indian Ocean. Two miles thick, and dispersed over an area the size of the United States, this cloud is probably involved in global warming. The detailed effects of such clouds is uncertain; they may shade and cool the surface of the earth, but the soot particles absorb sunlight and radiate heat , thus warming the atmosphere. Millions of Indian housewives cook with this plentiful, cheap fuel. The Indian government has become touchy about this brown cloud and don’t want to fund further studies. The U.S. government wants to know more , because this situation adds to their objections to the 1997 Kyoto Protocol, which exempts developing countries such as India and China from cutting emissions of greenhouse gases. This treaty, which the U.S. did not ratify, does not mention soot as a greenhouse gas, but it surely is. Another plume of pollution over the ocean east of China contains of soot that is polluted with mercury from coal-burning power plants. It appears that this pollution cloud has affected weather over China, causing droughts in one area and heavy rainfall in another. As those who have read Chapter 8 know, global warming is complicated and political. (Wall Street Journal, 5/6/03, page 1)Soot, an Important Greenhouse Gas According to a paper by Mark Z. Jacobson to the Dec. 11, 2001 meeting of the American Geophysical Union, in San Francisco, diesel soot contributes almost half as much as carbon dioxide to global warming. Carbon soot absorbs light energy at all wavelengths from the infrared through the visible into the ultraviolet and then emits this energy as heat in the infrared. Because soot has a rather short lifetime in the atmosphere (it rapidly reacts with oxygen in the air to form carbon dioxide), controlling soot should have a major cooling effect on the climate. This powerful green house gas from diesel vehicles was not considered in the 1997 Kyoto Protocol, nor have most computer models of global warming considered diesel soot. This is a major argument against diesel engines. The media seems to be ignorant of the role that soot has in global warming.
Improvements in Diesel Exhaust (7/1/03)
Diesel soot strongly contributes
to global warming, but there is relief in sight.
A remarkable emission control system that cleans up diesel
exhaust is being installed across Europe.
Although more efficient than their gasoline-fueled internal
combustion cousins, diesel engines pollute the air with fine soot
particles. style You have seen
and smelled the diesel smoke while driving behind a bus.
These particulates are known to be a health hazard, but
ordinary exhaust catalysts cannot remove this soot.
Many scientists and most environmentalists do not realize that
this soot is also a powerful greenhouse aerosol.
Now the diesel pollution problem is improving in Europe because
of this new CRTu’ process, invented at Johnson Matthey.
Although this new diesel exhaust catalyst was developed in
1989, it could not be used until sulfur-free diesel fuel became
available, because sulfur inactivates (poisons) the platinum-based
exhaust catalyst. Now
that sulfur free diesel fuel is available, the CRTu’ system is
selling briskly in Europe: 5,000 systems were sold in 2002 and 500 a
month are now being sold. It
is interesting that the CRTu’, system, which was awarded the UK’s
biggest engineering innovation award, the MacRobert Award, makes use
of a toxic component in the exhaust gas, nitric oxide, to convert soot
particles into carbon dioxide.
You might remember from pages 137-8 in Chapter 6, that this
molecule, nitric oxide, is a hormone that is made in many parts of our
bodies. The question is
when will this diesel exhaust purifying system reach the United
States; sooner if those people interested in global warming were aware
of the ecological and health problems associated with diesel engines.
Acid Rain in Washington
The problem of urban pollution and
acid precipitation (often called acid rain) is of increasing concern in
the Washington metropolitan area. Pure, distilled water has a neutral pH
of 7. Normal, unpolluted rain is slightly acid, with a pH of 5.6,
because the carbon dioxide in air combines with water to form small
amounts of a weak acid called carbonic acid. Rainfall in the Washington
area has an average pH of 4.2 to 4.4, more than 10 times as acid as
unpolluted rain. The main source of pollution here is exhaust from
automobiles, trucks, and other forms of transportation. Vehicle exhaust
contains nitrogen oxides and sulfur dioxide, which combine with water to
form strong acids.
Acid Rain-the Effect of Air Pollution
Carol Mahan email@example.com
The motor car is an important
contributor to air pollution in South Africa. The transport sector
(including aeroplanes, ships, trains and road vehicles) contributes
44% of the total national nitric oxide emissions and 45% of the total
national volatile organic carbon emissions (VOC). Road vehicles,
rather than trains, aircrafts and ships, contribute the most to the
total carbon dioxide, nitric oxide and VOC emissions from the
transport sector (94%, 53% and 89% respectively). Road vehicles also
contribute to lead emissions, especially in the urban areas.
Air Pollurion with Emphasis on Traffic Generated Aerosols
Effects of Air Pollution on local climate
Dust particles become condensation
nuclei to facilitate rainfall downwind from the source of dust.
particles also cause an increase in the amount of visible light
radiation which reflects back into space (= reduced albedo.)
y Ann Taviani on Monday, October 27, 2003 - 01:20 pm:Topic 9 Question 1: VOCs
VOCs are volatile organic compounds. Hydrocarbons are often VOCs and they enter the atmosphere in automobile exhausts and play a major role in the formation of photochemical smog. For the most part, most VOCs are not pollutants themselves; however when they react with other sustances in the atmosphere, secondary air pollutants are created and these secondary air pollutants are associated with smog. VOCs can enter the environment through natural sources and anthropogenic sources as well.
The main source of anthropogenic hydrocarbons is the petroleum industry. This is because the petroleum industry produces gasoline and gasoline is a complex mixture of many volatile hydrocarbons and when in urban areas, the gasoline vapors escape into the atmosphere in several ways. Some of the ways include: when gas is pumped at gas stations, during filling of storage tanks, and as unburned gasoline in automobile exhaust.
In terms of natural sources and the natural world, the smell of pine, eucalyptus, and sandalwood trees is derived from the evaporation of VOCs called terpenes from these trees leaves. 85% of the total emissions of volatile hydrocarbons is from natural sources and 15% is from anthropogenic sources. It may seem like it's not a big deal because the anthropogenic sources are a lot lower; however, the emissions from anthropogenic sources are not evenly distributed, but are concentrated in urban areas, whereas natural emissions are evenly distributed.
Considering we cannot control VOCs from natural sources, we can work on controlling them from anthropogenic sources. One of the major ways of controlling VOCs and their hydrocarbons is the use of catalytic converters in automobiles. These catalytic converters which oxidize and reduce, remove about 98% of hydrocarbons emitted from auto exhaust systems.
Air pollution can prevent rainfall, reported in the 10 March
2000 issue of Science
These data are the first direct evidence of how urban and industrial
pollution affects rainfall levels, a question scientists have debated for
several decades. In fact, some previous studies have concluded that air
pollution might increase rainfall, but the debate has continued due to a
lack of convincing data.
Environmental Effects of Urban Traffic - A case study of Jaipur City
Growing Urban centres necessitate the sprawling of
transportation network, increasing distance between places of residence
and work which needs to be covered in minimum time. The increased
socio-economic status of urban population coupled with inadequacy of
public transport has encouraged personalized means of transport. This
craze for owning vehicles in urban centres, has led to considerable
noise and air pollution, especially in big cities. (Table 1)
acid rain (deposition)
result from both wet and dry acidic depositions that
occur downwind of areas that are emitting SO2 and NOx from fossil fuel
burning; other acids are involved to a lesser degree; e.g. HCl from coal
burning power plants; where pH is < 5.6
all rainfall is normally slighly acidic - water reacts
with CO2 to form weak H2CO3 (carbonic acid); pure rainfall has a pH
pH involves a logrithmic scale
not only isolated in mid-west; now found along both
coasts of U.S.; internationally, developing countries tha rely on coal
will face serious problems; e.g. China
Air Pollution Linked to Drought
Source: Copyright 2002, Cosmiverse
Since the 1960s, Sahel in northern Africa, which
borders the Sahara, has experienced widespread drought. Rainfall was up
to 49% lower than in the first half of the 20th century, causing
widespread famine and death. Air pollution may have contributed to the
Sahel drought, says Australian researcher Leon Rotstayn.
is Acid Rain : Air Pollution
Acid rain has been called the
environmental issue of the 1980s and it continues to be a problem today.
However, acid rain is not a new problem at all. It dates from the middle
of the 19th century when a Scottish chemist, Robert Angus Smith, began
to study the effect of air pollution in Manchester and used the term
'acid rain' to describe his findings. What is very new is the scale of
the problem. In Smith's time, acid rain fell both in towns and cities
and downwind from them, but now, the pollution is spread far and wide,
within and between nations. It has now become an international problem.
The track of large ships is sometimes visualised by a trail of shallow stratus clouds. These clouds, known as 'ship tracks', form in the wake of ships and are remarkably long-lived (Fig 1). They typically are between 0.5-5 km wide, i.e. wide enough to be seen in visible satellite imagery. Sometimes a ship track appears as a band of enhanced cloud thickness embedded in stratus. Ship tracks are due to cloud condensation nuclei (CCN) in the ship's exhaust (4). They are most likely in a near-saturated environment that is otherwise depleted of CCN. Such environment is very common in the marine boundary layer over the subtropical highs. Over these large, quasi-stationary highs, the boundary-layer air is divergent, making it unlikely to draw in CCN-rich continental air.
The nature and climatic effect of ship tracks was investigated in a field campaign labeled MAST (Monterey Area ShipTrack), which was conducted during June 1994 off the central California coast. Ship tracks increase the albedo, yet have very little effect on the long-wave radiation balance, because they are so shallow. Therefore ship-tracks tend to cool the global climate, although the magnitude of this effect is likely to be small.
ReferencesMims, F.M. and D.J. Travis, 1997. Aircraft contrails reduce solar irriadiance. EOS, 78, Oct 14. Travis, D.J. and S.A. Changnon, 1997. Evidence of jet contrail influences on regional-scale diurnal temperature range. J. Weather Mod., 29, 74-83. Sassen, K., 1997.Contrail-cirrus and their potetial for regional climate change. Bull. Amer. Meteor. Soc 78, 1885-903. Ferek, R. J., D. A. Hegg, P. V. Hobbs, P. Durkee and K. Nielsen, 1998. Measurements of Ship-Induced Tracks in Clouds Off the Washington Coast. J. Geophys. Res., 103, 23,199-23,206.
Posted on Tue, Jul. 23, 2002
emissions of vapour, Gases may contribute to warming.
On clear winter days, the sky can resemble an enormous Etch A Sketch. White lines left in the wake of jets crisscross each other, often stretching from one horizon to the other. But as ephemeral as they may seem, these cloudy trails could be contributing to global warming by trapping heat, according to a growing body of scientific research. If counted all over the globe, contrails -- the vapor trails left by aircraft -- have been found to cover a small but noticeable portion of the Earth's surface.
From 35,000 feet below, contrails may look like wispy lines. But they can grow into clouds many miles wide and hundreds of feet tall, and they often contain pollutants left by the burning of thousands of gallons of jet fuel. The trails and the clouds they create help to trap heat, contributing to the greenhouse effect, several recent studies contend.
be sure, power plants, heavy industry and automobiles are now believed
to be the largest sources of greenhouse gases in the world. The
airline industry says there is not enough evidence to single out
contrails as a significant environmental factor. But as aviation
grows, some scientists are concerned that contrails will become a
significant part of the global warming problem. ``Although
aviation does not make a large contribution to the warming problem
today, over the course of the next 50 to 100 years, it could become as
important a part of the problem as passenger cars, according to some
estimates,'' said Michael Oppenheimer, professor of geosciences and
international affairs at Princeton University.