The White Mountains temporarily become the Smokey Mountains

2019-07-10 06:26:37.000 – Jay Broccolo, Weather Observer/Meteorologist

The past couple of weeks have been quite hazy, lowering visibility down to as short of a distance as 8 miles today and even lower in the valley areas. Today, the 10^th of July, could be even hazier, dropping visibility below 7 miles, which is mildly exciting for us because we can code a weather phenomenon that we normally do not get to see, FU, which is smoke (types with a smile). That also means the air is dense with particulates. The NWS defines Haze (HZ) as an aggregation in the atmosphere of very fine, widely dispersed, solid or liquid particles, or both, giving the air an opalescent appearance that subdues colors.” Essentially, anything in the atmosphere that is not in a gaseous state like; pollen, dust, sand, snow, volcanic ash, and currently, a combination of mostly smoke, higher humidity and of course, pollution. Hazy conditions tend to occur in the warm season because there is more water in the atmosphere in the form of water vapor. Partly because there is a much greater amount of evapo-transportation occurring, which is the transfer of moisture by organic life, i.e. trees, soil, and so forth. So how does all of these combine to give us haze? 

Well, the reason why the increase in water vapor (humidity) is so important because most of the haze we see, especially on the east coast, is because of the chemical reactions that occur in the air between pollutants like Sulphur Dioxide (SO2), which originates from the burning of fossil fuels, other industrial processes, volcanic eruptions, and dah dum… wildfires. SO2 bonds with the oxygen (O) and hydrogen (H) in the water vapor and air to create various sulphur oxides (SOx) and can even precipitate as Sulphuric Acid (H2S04), if in liquid form. If less water is present, then as a solid in the form of ammonium salts, which if mixed with water can create Sulphuric Acid. Either way, they both act to scatter the light because the molecules are big compared to air and in different light spectrum, can appear differently. Sometimes, the bonds are created by oxidation reactions in which the sun helps the process along, a process called photo-oxidation. All of this is gross, I know!

This is what most of the haze in the Eastern United States is comprised off though. The Smokey Mountains in Tennessee and North Carolina have observed a drop in visibility. During pre-industrial times, the lowest visibility is believed to be around 25 miles. Currently, a typical day is around 25 miles with lower visibilities in the upper single digits, also gross! I digress. This haze we are currently experiencing is not just sulphur oxides and other compounds, but also terpenes from the trees, nitrogen oxides (NOx), methane (CH4), Carbon Dioxide (CO2), water vapor, volatile organics, fine and coarse particulates, along with literally hundreds of other chemicals and fumes depending on what is combusting. I actually caught few of the larger particulates on the snowboard overnight. Combustion itself is a form of really fast complete oxidation, by combining oxygen with a fuel source, normally carbon and hydrogen (gasp, trees), and the removal of hydrogen, carbon, and other molecules as the heat breaks the bonds.

Having said all that, haze = bad, at least at these current conditions. Be sure to check the air quality and your local weather forecasts before setting out into the outdoors. I will leave you with the current ‘smoke map’ from NOAA, which can be found here https://www.ospo.noaa.gov/Products/land/hms.html

 

Jay Broccolo, Weather Observer/Meteorologist