Can you smell these photos? Raindrops cover flowers in Ketchikan, Alaska on August 27, 2017 (L) and a tourist visits the Mendenhall Glacier on a rainy day (R, date unknown). When a summer thunderstorm arrives and rain falls on the hot, dry ground, why does it smell so good outside? Farmers have said that they can “smell rain” before a storm arrives. Some describe the scent before a rain storm a musky, earthy smell called petrichor. But, we know that rain itself has no scent. The process, which was first studied in 1964 by Australian scientists, comes from a moistened ground. Petrichor is made up of oils of plants and bacteria that live in the ground. Tiny microorganisms, called actinobacteria, are found in rural, urban, and marine environments and help decompose decaying matter into nutrients for plants and organisms. Their byproducts, called "geosmin", are similar to a type of alcohol. The chemical structure of geosmin makes it detectable, even in trillion parts per air molecule. During periods of prolonged dryness or drought, the actinobacteria slow down their decomposition activity. As a storm approaches and the air becomes humid, the ground begins to moisten. This helps the actinobacteria to speed up their activity, forming geosmin. As raindrops fall, porous surfaces such as loose soil, splatter and eject aerosols, similar to a ring on a lake after throwing a rock in. These tiny particles can be carried by the wind, alerting people downwind that rain will soon be on the way. The scent goes away as the storm passes and the ground dries up once again, leaving the actinobacteria in waiting of when it might rain again, the sound of thunder rumbling in the distance. To learn more about particulates, petrichor, and other air quality topics, please click here! ©2022 Meteorologist Sharon Sullivan References:
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 Image Credit: Climate Central In order to understand how weather and ozone are related we first must understand how exactly ozone forms. There are a few key ingredients to the formation of tropospheric ozone: volatile organic compounds (VOC), sunlight, and warmth. VOCs are generated through emissions anywhere from industrial facilities to the tailpipe of people’s cars. These compounds are spewed into the air on a daily basis but in high concentrations can cause issues. In areas of high concentrations, and with the help of sunlight, a chemical reaction occurs that creates tropospheric ozone or ground-level ozone which is what it is sometimes called. We are all aware of ozone higher up in the atmosphere, called stratospheric ozone, that actually protects us from harmful UV rays. However, ground-level ozone, is actually harmful to humans and plants.
Now, where does weather come in? As we all know, weather influences our day-to-day lives whether that is with rain, sunshine or overcast skies. Weather influences the “life-cycle” of ozone as well. Wind patterns can carry ozone plumes across countless miles which affects areas that could be hundreds of miles away from where the initial source is. A perfect example of this is the Great Lakes. Chicago, being a populated area with industrial facilities within its reach produces the ozone precursors (VOCs) and when winds are southwesterly in the region, those VOCs travel across Lake Michigan and can impact areas within the southwest Michigan region. A prime day for ground-level ozone production in that region is southwest winds, clear skies, and a hot day. If the air temperature is too cold, ground-level ozone tends to not produce as much as it does on a hot day. Also, if there isn’t ample sunlight, like on an overcast day, ozone production is cut-off because it needs sunlight in order to produce the chemical reaction needed in order to form. This is why ground-level ozone can be variable as it is very dependent upon the overall weather it occurs in. Forecasting weather patterns helps immensely when it comes to forecasting overall air quality, because the weather can tell you if there will be any ground-level ozone plumes forming or approaching from another area upwind from your location. For more information of Air Quality issues, click here. ©2022 Meteorologist Alec Kownacki  DISCUSSION: In order for lightning to occur, ice of different sizes and supercooled liquid water (liquid that occurs below 0°C) must be present in a cloud. A thunderstorm cloud (i.e., a cumulonimbus cloud) is quite turbulent with all the ice getting tossed about and colliding with one another. The environment inside a thunderstorm is somewhat similar to the environment inside a washing machine. The collisions amongst the ice allow charge to transfer between them. Since charges can typically move easier through liquids than solids, the supercooled water helps speed up the charge transfer process. Larger pieces of ice tend to acquire charges of one sign, while smaller ice tend to accumulate the opposite sign of charge. A strong updraft is required to produce all this mass of ice and liquid in the cloud. It is also necessary to help transport the smaller ice crystals toward the top of the cloud, while large ice settles toward the bottom of the cloud. This charge transfer and separation may eventually build up large enough to overcome the electrical resistance of air, resulting in a lightning flash.
So, how does air pollution play into this? It is very difficult to get water vapor to spontaneously condense or freeze in the atmosphere. There must be something (e.g., an aerosol) to condense or freeze onto. When there are more aerosols or more pollution in the atmosphere, more droplets can form. This large number of droplets are all competing for a limited amount of water vapor, and thus, cannot grow to raindrop size. Instead, they remain in the cloud and may get carried upward above the freezing level supplying the supercooled liquid and/or ice required for lightning. In contrast, clean air with relatively few aerosols only allows a smaller number of droplets to form. In this case, there is more water vapor available for each droplet, potentially allowing them to grow to raindrop size and fall out of the cloud before they can freeze and contribute to lightning formation. Hence, less air pollution may result in less lightning and vice versa. Observations support this relationship between air pollution and lightning. The response to the COVID-19 pandemic, especially in the beginning, resulted in less travel, industrial activity, etc., which resulted in a cleaner atmosphere. A recent study by Yakun Liu showed that global lightning flashes like the one shown above in Spain occurred much less often in association with this decrease in air pollution. Local increases in lightning have also been observed near the Philippines in association with increased aerosols from a volcano, along major shipping lanes due to pollution from ships, and in association with smoke from wildfires in Australia. Reducing air pollution can obviously, lead to better health outcomes. Given that lightning can start fires and/or cause fatalities, the reduction of lightning associated with a reduction in air pollution may be another beneficial aspect of actions and policies that seek to limit air pollution. For further information concerning air quality, be sure to click here! ©2022 Meteorologist Dr. Ken Leppert II  Aside from the meteorologists you see on television or the meteorologists you hear about from the National Weather Service, air quality meteorologists apply the meteorological foundation to air pollution and the overall quality of the air around us. Air quality can be directly related to meteorology in terms of transporting air pollution from one source to another area. Air quality meteorologists pay attention to numerous pollutants being lifted into the atmosphere by sources, most likely from industrial facilities. Some of these pollutants can influence the surrounding area from which it originated.
Tropospheric ozone is a substance that can be directly influenced by pollutants being released into the atmosphere. Ozone also needs sunlight in order to be produced as well as, in most cases, hot and dry weather. There are numerous studies that have looked closely into whether ozone prefers hot, and dry weather over hot, and humid weather. These studies have shown that ozone tends to prefer hot, and dry weather in order to form. However, this does not mean ozone doesn’t form when the weather is hot and humid though. Another pollutant that air quality meteorologists look into is fine particulate matter (PM-2.5), more commonly known as smoke. There are other particulate matter under the PM-2.5 umbrella, but smoke is the most common. This pollutant comes from wildfires that tend to occur during hot, and dry weather conditions. Smoke from these fires become lofted into the atmosphere and is transported via atmospheric winds and can return to the surface from subsidence, or downward motion in the atmosphere. Aside from providing colorful sunrises and sunsets, these concentrations can cause harmful situations for those with breathing problems or underlying illnesses. The job of an air quality meteorologist is to forecast these pollutants and provide the general public with the most up to date information and data. If need be, meteorologists will issue an air quality action day which headlines harmful concentrations of pollutants and poor air quality. These action days are most common during the summer months, but can occur during other months throughout the year. Clear communication is of utmost importance for air quality forecasts, much like general weather forecasts. The atmosphere in which we live in and interact with changes relatively quickly, so concise and clear communication is needed in order to keep society safe. Stay tuned as this article kicks off a new series of articles concerning air quality and meteorology. To learn more about other interesting stories related to air quality, be sure to click on the following link: www.globalweatherclimatecenter.com/airquality ©2021 Meteorologist Alec Kownacki  Point-source emitters in Utah Valley. Source: Snowbrains As an air quality scientist, I’m constantly looking through poor air quality images such as the what we find in the image above while also finding ways to not only predict when these sorts of conditions will develop but what we can do to reduce their likelihood. So let’s dive into a slightly gross but important topic: Particulate Matter.  Size distributions of particulate matter. Source: John Wenger, University of College Cork Before we dive in, it’s important to distinguish between particulates and particulate matter. Particulates are the actual airborne particles while particulate matter (PM) refers to the concentrations of these solid and liquid particles that get suspended in the air and are made up of a wide array of elements. We break PM down into two elemental categories: organic and inorganic. Examples from both categories include anything from water vapor to soot from wildfires. They can also carry bits of chemical species, including nitrogen dioxide, ozone, and carbon dioxide, to name a few. As a result, inhaling air with high PM levels can cause both short and, depending on the level, long-term respiratory damage. The severity of the damage to the respiratory system is exasperated whenever the particulates within those concentrations have finer dimensional sizes that make them easier to inhale. In order to account for finer particle concentrations, PM are classified into dimensional categories as well. These include PM10, which include all particulates with diameters that are less than 10 micrometers (um) across, and PM2.5, which only include all particulates with diameters that are less than 2.5um across.  Emitters of particulate matter. Source: Lindsey Konkel, Food and Environment Reporting Network Unfortunately, high PM conditions have become much more common in developing counties in recent years, including China and India, as emissions have increased in cities, resulting in greater anthropogenically(human-induced) PM levels. Emissions essentially allow for an even greater likelihood that particulates will develop, increasing their concentration while also decreasing their sizes as they take up more space and leave less room for development. In cities that are located in valleys, such as Salt Lake or Mexico City, the entrapment of man-made emissions in their urban cores only further enhances the likelihood that particulates will form, until their concentrations reach critical levels, as can be seen in the images below:  High PM levels over the LA Basin. Source: David Illif So what can we do to mitigate PM levels in cities? Limiting emissions is the best method to bring those levels down, along with placing industrial centers away from places that geographically enable the entrapment of pollutants, like valleys and basins. Urban projects should be wary of how and where they develop residential areas in order to lower the likelihood that people will be exposed to dangerous PM levels. These are just some of the many methods that can help to reduce particulate concentrations. If you live in an area with high levels of pollution, you can also reach out to local government in order to get the community involved in reducing its emissions!
To learn about more air quality topics click, here. ©2020 Meteorologist Gerardo Diaz Jr. Sources: https://www.greenfacts.org/en/particulate-matter-pm/level-2/01-presentation.htm https://www.thoughtco.com/definition-of-nucleation-605425 https://snowbrains.com/salt-lake-city-ut-7th-worst-air-quality-in-usa-says-american-lung-association/ http://fafdl.org/blog/2018/02/23/nitrogen-emissions-air-pollution/ http://fafdl.org/blog/2018/02/23/nitrogen-emissions-air-pollution/ Inversions in a vertical profile of the atmosphere paint a picture of what is going on at a level (Altitude) well above what we can feel (weather often beginning at the surface and extending to the troposphere (6-20km), commonly extended to the stratosphere). Meteorologists look at multiple levels above the surface to detail what could be happening in your area.  Photo: An example of a Skew-T/LOG-P chart that depicts many variables in a vertical profile of the atmosphere taken at 1200 UTC on 12/22/2019 from Central Illinois. (Photo from the University Center of atmospheric Research) Warm air advection refers to the transfer of warm air from one region to another, which in turn, leads to warmer temperatures at the surface or well into the atmosphere. In this case, we see temperatures rise well above the surface, which creates an inversion layer. Looking at the Skew-T graph, we notice the slanted blue lines give temperature values in Celsius, and the red line presents a graph of the temperature differences with height. At the very bottom of the graph, the temperature is near freezing (0 degrees Celsius), while slightly above the surface, the temperature is closer to 10 degrees Celsius. Due to present cold air at the surface and the factor of warm air rising, the warm air that is advecting into the new region will rise as it moves in. Often air temperature will decrease with height, but in the case of inversions, the air temperature warms with height. The case stands where warmer air moves into a region and rises higher than the already present warm air, thus creating this inversion effect. During the summer, an inversion can aid in the presence of severe weather as a result of solar heating allowing for the inversion layer to be broken due to rapidly rising air. During the winter, an inversion can be present due to advection of warm air, but topography can play a role in blocking air from rising further or mixing. In the case of mixing, warm air rises and generates a mix of the air that was present above it, which acts to ‘dilute’ the air and dry air can mix with fog, clouds or pollution. This situation of pollution interacting with topography is evident in a photo overlooking Salt Lake City, Utah. We can mistake a layer of white just above the town for low hanging clouds, but in reality, it’s a layer of pollution that is trapped.  Photo: Inversion layer present over Salt Lake City, Utah in the winter months. (Photo courtesy of The Daily Universe) Thanks to the surrounding mountain ranges and the city standing in the valley, the inversion layer is somewhat stagnant in town. Pollution accumulates since it is trapped by the surrounding topography which leads to regular poor air quality. In fact, the population has dealt with premature deaths due to the consistent exposure to pollutants.
Utah is only one example of poor air quality due to surrounding topography. Other towns include Los Angeles, Beijing and Hong Kong that deal with high amounts of pollutants in the air. Constant emissions from vehicles and homes contribute to a growing amount of particulate matter in the air that could be trapped in an inversion layer. Winter is a harsh time for inversions to be present for a lengthy period of time in colder regions. Because of the low amount of solar heating with shorter sunlit hours, the chance of mixing the air at the surface with the air aloft is challenged. Cities have little choice to inhibit the buildup of these pollutants, and the ultimate choice is to reduce emissions for a cleaner environment. Research is underway for further preventative measures that these towns can take to reduce pollution and the effect on the community. To learn about more air quality topics click, here. ©2020 Meteorologist Jason Maska  Source: PRI-Environment With summer nearly here, I recently started considering making a few visits to a couple of the big national parks out west. And as an air quality scientist, one of the very first things I looked into was the pollution levels in and around some of the largest parks. Needless to say, what I found was rather surprising. According to the National Parks Conservation Association (NPCA), approximately 85 percent of the nation’s 417 national parks are dealing with unhealthy air conditions. These poor air conditions have also led to everything from hazier skies to damages to sensitive species and habitats. As such, this is a serious and significant matter for nearly all of the national parks in the country, given that these parks are annually visited by millions of Americans, thus leaving them at risk of unexpected respiratory problems, along with the obstruction of landmarks and wonders within said parks due to the decreased visibility.  Source: SFGate While no park is the same, a large portion of the nation’s 417 parks are found in the West. This region has experienced significant population growth in recent decades, with cities like Phoenix and Denver outpacing the growth of cities back East. This demographic shift in population centers increasing in size in the West has retroactively led to more emission sources, ranging from newer coal plants to greater vehicle emissions owing to more cars in the region. The release of various pollutants, ranging from nitrous oxides and ozone, all effectively are introduced into the atmosphere and are dispersed with respect to wind patterns in a given area. Poor air quality in the west is further enhanced by the Rocky Mountains, which serve as natural barriers that can help to either entrap pollutants or change their trajectories and then advect (move) them to areas that are downstream of their original pollution source. The increase in anthropogenic (man-made) emissions is just one of many variables that are at play in the overall decrease in air quality in recent years. Another major factor is the overall shift in the amount of wildfires that have occurred due in large part to Climate Change. At their core, wildfires release large amounts of particulates into the atmosphere, decreasing air quality across areas as they spread and are transported by upper-level winds. These natural disasters become more frequent and last longer than they have in the past, the west will have to deal not only with more damage and destruction from said wildfires, but also from the negative secondary effects caused by more particulates being released into the air.  Source: Yahoo News Given the decrease in air quality in several of the cities in the West, it comes to no surprise that all of that pollution eventually bleeds into many of the national parks in the region. As such, many visitors from those urban centers who may be visiting said parks to escape the air pollution for a few days tend to be surprised to find that those same conditions have made their way to their vacation destinations. Furthermore, as climate change alters the intensity and length of wildfires, destruction caused by said fires will also be a major concern that national parks in the West will have to deal with as well. With all of this in mind, the real question becomes: what can we do to preserve our national parks and prepare them for the challenges that lie ahead in the coming decades? We can start by acknowledging that there is a significant air quality problem in our national parks that stems from pollution sources in our urban centers. At the local and community level, people can try to reduce their carbon footprints by finding alternative modes of getting around, such as public transit, or by opting in to getting their electricity from more renewable sources like wind or solar power. We can further reduce our pollution levels by demanding for more alternative forms of fuel and more public transportation, and legislating for such things. All in all, it may seem like a daunting task, we need only look back to Theodore Roosevelt, who once said "I recognize the right and duty of this generation to develop and use the natural resources of our land; but I do not recognize the right to waste them, or to rob, by wasteful use, the generations that come after us." Indeed, if we don’t work to decrease our pollution output and find ways to mitigate the effects of climate change, these wonderful national parks that we have inherited may not be the same national parks we leave behind for the next generation. © 2019 Meteorologist Gerardo Diaz Jr. Sources: NPCA Parks Report 2019: https://www.npca.org/reports/air-climate-report/ Yahoo: https://news.yahoo.com/cant-escape-air-pollution-national-150928067.html Global Citizen: https://www.globalcitizen.org/en/content/national-parks-air-pollution/ PRI-Environment: https://www.pri.org/stories/2016-04-16/fighting-haze-grand-canyon SFGate: https://www.sfgate.com/news/article/Yosemite-wildfires-smoke-valley-Empire-South-Fork-12176803.php#photo-14057642   Air quality is vital to everyday life and health. Certain gases and particles cause poor air quality (polluted air) in large quantities. This is very unhealthy and unsafe to breathe in.
The National Oceanic and Atmospheric Administration (NOAA) wrote in an air quality article that they are in partnership with the Environmental Protection Agency (EPA) to “issue daily air quality forecasts as part of a national Air Quality Forecasting Capability.” The National Weather Service (NWS) and NOAA implemented this national Air Quality Forecasting Capability that gathers hourly pollutant concentrations in a graphical and numerical form to help prevent the loss of life. NOAA explains the two major pollutant categories: ozone and particulate matter. Nitrogen oxides and volatile organic compounds, such as motor vehicle exhaust, industrial emissions, gasoline vapors, and chemical solvents,that produce ground-level ozone when there is heat and sunlight. If ozone gases are inhaled, it can create health problems such as lung irritation and inflammation, asthma attacks, wheezing, coughing, and increased susceptibility of respiratory illnesses. Particulate matter are airborne particles that includes dust, dirt, soot, and smoke. Some particles are directly emitted into the atmosphere and some are formed when gases from burning fuels react with water vapor and sunlight. What impact does weather have on air quality? NOAA’s National Center for Environmental Information explains how scientists found a correlation with air quality and heat waves, droughts, and snow storms. An increase in ozone can be caused by heat waves, due to the air being stagnant and trapping emitted pollutants. Heat waves can also create a drought. This can create dry vegetation which is fuel for wildfires thus creating smoke. Also, when there are large snow storms that cause power outages, air quality can be indirectly affected due to people using wood and coal burning stoves, fireplaces, and gas or diesel generators to stay warm. Reducing the amount of the burning of fossil fuels and trying to maintain/prevent wildfires can help keep air quality clean thus making air safer for all humans and animals. To learn more about air quality topics, click here! ©2018 Weather Forecaster Brittany Connelly  Since the year 2000, the largest wildfire in almost every American western state has occurred. As we have seen on the news recently, wildfires possess a capability to completely obliterate anything in its path. Along with infrastructure and economic damage as threats, these wildfires put plumes of fine particulates in the air which causes health damage. These particulates extend far past where the initial spark occurred. Thanks to the atmosphere, the particulates can travel hundreds—If not—thousands of miles away from the fire and have an effect on the air elsewhere.
An analysis of PM2.5, particulate matter smaller than 2.5 microns in diameter, showed that through worsening wildfires, air quality in turn decreases due to the increase in PM2.5. The EPA has established a federal 24-hour PM2.5 standard of 35 micrograms per cubic meter which is the standard for healthy human consumption. In the Sacramento and San Joaquin Valleys, the number of days for which PM2.5 exceeded the EPA standard declined during 2000 through 2016. This decline in the 16-year average can be attributed to efforts to decrease industrial emissions. However, the number of days of exceedances each year during the California wildfire season (June through September) has been increasing. With stronger and more frequent wildfires, this number will increase due to the abundance of PM2.5. Also, longer wildfire seasons are currently being observed, so with this, even more PM2.5 will likely be present in the atmosphere. Speaking of longer wildfire seasons, in the Pacific Northwest along with other western states, seasons are now on average 105 days longer than what they were in the 1970s. With these longer seasons, stronger fires occur as well. For instance, Idaho has experienced more than 10 times as many large fires (more than 1000 acres) in a typical year since the 70s. Oregon and Washington are 7 times as many and 5 times as many, respectively. The American West in recent years has experienced more frequent and stronger wildfires as a result of a drying climate. Efforts to clean the air and to remain below the PM2.5 35 micrograms per cubic meter standard set by the EPA, will be facing a harder challenge in coming years. As said above, air pollution progress is quantifiable and can be observed, but so can the increase in PM2.5. To read Climate Central’s full analysis go, here. To learn about more air quality issues click, here. ©2018 Weather Forecaster Alec Kownacki  DISCUSSION: As the state of California continues to contend with some of the worst wildfire conditions in recorded history, there are several other problems which are quickly emerging from wildfires such as (but certainly not limited to), the Camp Fire, the Woolsey Fire, the Hill Fire, and more. One such problem happens to be a substantial threat to general health and respiratory health issues for people of many different age ranges. For example, those with respiratory issues of any kind are far more vulnerable to the impacts from persistent wildfire smoke as well as people who are particularly young or old. Thus, there is much more to these wildfire threats than immediately meets the eye. Having said that, attached above is a brief video briefing which goes into some of these corresponding health threats in a greater amount of detail. Of course, there is still much more to learn and discuss beyond the scope of this article, so be sure to stay tuned for further updates as the state of California begins to work on getting closer to the road to recovery over time.
To learn more about other air quality topics from around the world, be sure to click here! © 2018 Meteorologist Jordan Rabinowitz A Quick Look at the Difference Between Tropospheric and Stratospheric Ozone (Credit: NASA)8/31/2018  DISCUSSION: When you hear someone say, “There is ozone in the atmosphere,” should you be worried? Well, that depends. Ozone, a chemical molecule formed by three oxygen atoms, has different effects on the earth, depending on where in the atmosphere it exists. Here, we quickly compare two types of ozone: tropospheric ozone (near the surface) and stratospheric ozone (up in the stratosphere). Let’s take a closer look.
There is very little natural tropospheric ozone, so most ozone that forms in the troposphere is purely anthropogenic. Most of the tropospheric ozone is also a secondary pollutant, meaning that it is not directly emitted into the atmosphere, but instead forms when the right conditions occur. Emissions from automobiles and other industrial processes cause higher ozone concentrations during the day. Through some slightly complicated chemistry, when these emissions react with sunlight (known as a photochemical reaction), ozone is formed. High ozone levels at the surface pose a threat to human health, such as respiratory infections. Exposure to ozone can increase the risk of bacteria, such as pneumonia or bronchitis. So, the short answer – ozone at the tropospheric level is bad. Stratospheric ozone, on the other hand, occurs much higher in the atmosphere, and in a much higher concentration – but this is actually a good thing. This layer of ozone in the stratosphere, aptly named “the ozone layer,” is vital to life on earth. It filters out harmful ultraviolet (UV) radiation that would otherwise make earth uninhabitable. This layer, however, has been depleted in the past by the release of aerosol chlorofluorocarbons (CFCs), a chemical that contains carbon, chlorine, and fluorine. Through some more complex chemistry, these CFCs destroy stratospheric ozone, therefore resulting in their ban in 1978. It is worth mentioning that there can be an exchange between stratospheric ozone and tropospheric ozone. Although a stable layer of air exists between the troposphere and stratosphere, trace measurements have shown that there is in fact gas exchange between these two layers of the atmosphere, but it takes place very slowly – on the order of years. To learn more about air quality, click here! © 2018 Meteorologist Joseph Fogarty  DISCUSSION: With the volcanic eruptions in Hawaii and Guatemala releasing volcanic ash dust into the atmosphere, these particulates could have drastic implications on life in these areas. This discussion will outline some of the elements that can be found in the atmosphere. Some of these can be detrimental to human health.
Particulates are solid and liquid material that can be 0.1 to 100 micrometers in size. These represent about 90% of all atmospheric particles. These can come from natural sources such as ash, dirt, dust, and pollen. Particulates can also come from human activity such as combustion, incineration, and construction. These pollutants are commonly made of carbon and silica, however other elements could be included. A particulates lifespan in the atmosphere can be dependent on its size. Particulates greater than 10 micrometers in size tend to disperse out of the air after emission. Any particulate between 1 and 10 micrometers lifespan is dependent on the state of the atmosphere at the time of emission. Anything less than 1 micrometer can stay in the air for a long time! Particulate matter is classified relative to 2.5 and 10 micrometers. These are labeled as PM2.5 and PM10, respectively. Carbon in the atmosphere, in one way, can be described by its oxides. The most prevalent ones are Carbon Dioxide and Carbon Monoxide. Carbon Monoxide, labeled as CO, is generated by combustion engines. CO is very dangerous to human life as it can easily bind to hemoglobin. This prevents oxygen from reaching the brain and other organs. Carbon Dioxide is produced in a variety of ways. Some of the natural ways that Carbon Dioxide is produced is through volcanoes, plants, weathering of rocks, etc. Carbon Dioxide can be removed by “sinks” in the world. Oceans are one of these “sinks,” by removing roughly 1/3 of the Carbon Dioxide from the atmosphere. However, Carbon Dioxide has been on a steady increase since the Industrial Revolution. Carbon can also be described as Hydrocarbons. Hydrocarbons are Carbon molecules attached to an amount of Hydrogen molecules. A notable Hydrocarbon is methane, which is a significant greenhouse gas. Hydrocarbons can be released through natural sources such as animals and wetlands. Human activity such as coal and gas production also produce methane. Other elements that can be found in the atmosphere with their oxides are Sulfur and Nitrogen. Unlike Nitrogen, Sulfur can also be found in the atmosphere as Hydrogen Sulfide. Nitrogen compounds can arise naturally from oceans and soil decomposition. Nitrogen oxides are produced from human activity and is corrosive to many surfaces. Roughly 2/3rds of sulfur in the atmosphere can come from natural sources. Human activity such as coal plants, gas plants, paper mills, and oil refineries can release sulfur into the atmosphere. For more about Air Quality, click here! © 2018 Meteorologist Jennifer Naillon  Imagine a pollutant as an unwanted guest in a family house. The pollutant will eventually overstay its welcome. Certain processes act like the “enforcers” of the family and remove the pollutant from the house. This happens frequently in the atmosphere!
There are three distinct processes that remove pollution from the atmosphere. The three processes are: gravitational settling, dry deposition, and precipitation scavenging. Gravitational settling is where particulates come down to the surface by gravity. This process removes most particulates that are greater than 0.1 micrometers. The larger particles will be removed quickly. However, particles on the smaller end could remain suspended by turbulence. When the turbulence dies down the smaller particles will eventually settle down. Dry deposition, also known as adsorption, is a turbulent transfer process. Dry deposition is a downward flux where the surface acts as a “sink.” Two causes of dry deposition are impaction and interception. Impaction is where smaller particles near larger ones cannot follow the normal flow, so they hit a water droplet. Interception is where small particles follow normal flow near an obstruction, and then the particle collides into the obstruction. The rate at which pollution descends towards the surface is determined by the state of turbulence, bacterial activity over soil, or surface tension over water. This is a continuous process because it is not dependent on any precipitation. Precipitation scavenging is a more efficient process than dry deposition and gravitational settling. This process is the best at removing gases and small particulates. Many of these particulates are condensation nuclei. Condensation nuclei are particles which water vapor condenses upon in the atmosphere. Once many nuclei accumulate and become large enough to fall, it precipitates as rainout or snowout. Washout occurs outside of the cloud. The greater the precipitation, the greater the amount of pollution that can be removed. In comparing the efficiencies of washout, snowout, and rainout, washout tops the list. However, washout depends on the rainfall rate, the size of the rain drops, and the pollutants that it gathers. In conclusion, air pollutants will eventually find their way out of the atmosphere by gravity, turbulence, or by precipitation. To learn more about air quality, click here! © 2018 Weather Forecaster Jennifer Naillon  DISCUSSION: The purpose of the Environmental Protection Agency's (EPA) Air Quality Index (AQI) is to quickly alert people to general air quality conditions and provide guidance that they may need to limit their exposure to outside air. Specifically, the index takes into account observations of various air pollutants, including near-surface ozone, particulate matter (small and larger particles), carbon monoxide, sulfur dioxide, and nitrogen oxide. A calculation converts the observed concentration of each of the above six pollutants to an AQI value. The pollutant with the highest AQI is associated with the scale above where a smaller AQI value (~25) indicates good air quality that poses little risk. A higher value (up to 500) indicates hazardous conditions even for healthy people.
As described by Physics Today's Mika McKinnon here, the recent fires in California highlighted several issues with the AQI. First, the AQI doesn't specify which pollutant triggered the value given. The pollutant with the highest concentration is important for determining which groups are most at risk. For example, carbon monoxide is especially dangerous for those with a heart attack risk, while ozone is especially dangerous for the very young and old. Thus, the AQI as given doesn't specify which people are most at risk on a given day. In addition, how frequently the AQI is updated depends on the number of observations in an area. In remote locations with few observations, it can take 24 hours or longer for the AQI to update. In the case of California fires, there was visibly hazy, dangerous air, while the AQI indicated good air quality conditions before it eventually updated to a higher value. Obviously, an AQI that doesn't necessarily match current conditions could pose a problem. The point of this article is not to discourage people from paying attention to the AQI. It does provide some indication of air quality conditions and actions that may need to be taken by certain groups of people. It is easy to read and understand. However, it is important to understand the limitations of this tool in order to use it most effectively and to spur further improvements of the tool. Click here to learn more about air quality throughout the globe! ©2017 Meteorologist Dr. Ken Leppert II  photo credit: (Environmental Protection Agency's AirNow Air Quality Index) DISCUSSION:
Although the excessive heat of the summer months allows for beach days, BBQs, and playing outside, it is crucial to remain aware of the extraordinarily hot temperatures for health concerns. The relentless sunshine can create unsafe air quality conditions in many regions across the United States. Not only is it essential to remain aware of summer illnesses like heat stroke, but an extra precaution must be taken during the excruciating summer weather to avoid respiratory and cardiovascular problems related to unsafe air quality. Specifically, tropospheric ozone forms as a result of sunlight reacting with nitrous oxides and volatile organic compounds. Therefore, the longer the sun shines throughout the day, the poorer the air can become. Sensitive groups are at severe risk during the summer, especially in densely populated/urban areas due to heightened emissions. Poor air quality is responsible for lung injury and possesses life-threatening outcomes. It is imperative to bear in mind that one should always attempt to lessen car emissions by consolidating trips, reduce the use of substances with chemical solvents, and to check air quality updates. The National Weather Service, partnered with the Environmental Protection Agency, produces daily air quality forecasts to protect the safety of people and the environment, so be sure to keep updated on your region’s ozone and smoke outlooks! A helpful resource for air quality is the EPA’s AirNow, which utilizes the AQI Index and is an easy-to-use tool to remain informed when it is (and when it is not) safe to spend time outdoors! Click here to learn more about air quality throughout the globe! ©2017 Meteorologist Alexa Trischler  photo credit: (Francesco Fiondella/International Research Institute for Climate and Society, Columbia) According to models published in the Journal of Geophysical Research: Atmospheres, a decrease in sulfur dioxide levels in the United States can markedly increase the rainfall of Africa’s Sahel region by the year 2100.
Since the 1970’s, the United States has been on a mission to particularly cut emissions of sulfur dioxide. Sulfur dioxide is a harmful gas that is yielded from the burning of coal. This gas leads to acid rain, poisoning crops around the world, and even induces respiratory problems in animals. In addition, sulfur dioxide “simultaneously cools and dries earth's climate by reflecting sunlight back to space and suppressing heat-driven evaporation near the ground.” By eliminating sulfur dioxide emissions out completely, models suggest that by the year 2100, there will be a 10% increase (from 2000 levels) in rainfall in Africa’s Sahel region (the transition region between the Sahara desert to the north and the Savanna to the south). The increase in rainfall will also cause the crop season to last longer, allowing harvesting to hit an all-time high. This will also generate economic growth. To learn more about air quality around the world and the research behind it, be sure to click here! ©2017 Meteorologist David Tedesco NOAA ATom Project Gets Underway! (credit: Christina Williamson via NWS Aviation Weather Center)8/3/2016 
DISCUSSION: As another neat scientific expedition being funded by the National Oceanic and Atmospheric Administration (NOAA) gets underway, here is a neat graphic and discussion below concerning this particular air pollution-oriented project. The project's name being the "Atmospheric Tomography mission" has it's goals set on studying and developing an improved understanding for how relatively short-lived greenhouse gases (e.g., ozone, methane, etc.) ultimately contribute to the effects of climate change around the world. Attached below you can clearly see the NOAA DC-8 aircraft being prepared for its departure! A very neat study without question! To learn about other neat studies being done in regards to air pollution and/or air quality research around the world, be sure to click here!
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