Imagine you work as a meteorologist for a state air quality agency, say, the North Carolina Division of Air Quality. A new plant wants to open in a rural area near the NC coast. It is your job to investigate the meteorology of the area and determine how it might affect the emissions of the plant.
This particular plant will emit concentrations of both VOC's (volatile organic compounds) and NOx (oxides of nitrogen). Based on material in Session 1, what do we know? We know that VOCs and NOx react to form ozone, which is hazardous to living organisms when breathed. We also learned about temperature inversions, which often occur overnight and in the early morning. Because of a temperature inversion, high ozone concentrations could be trapped near the surface.
From material covered in Session 2, what can we determine? We know that the energy balance in the area is important, and that the ground covers that are prominent in the area will play a major role in energy balance. Because a sandy soil is typical, the corresponding albedo will be high. The type of vegetation that grows is also important in determining albedo. But the vegetation also influences moisture in the area. Since the area is rural, and used mostly for farming, there will be a large amount of vegetation to influence energy balance. Because the plant is located near the Atlantic Ocean, we know that the air is generally moist, and the region will probably have a high Bowen Ratio. Also becasue of the moisture present, the diurnal variations in temperature will not be as extreme as locations further inland.
Session 3 presented material on meteorological parameters. As the meteorologist in charge, it would be your responsibility to make sure accurate data was collected, and that essential measurements, including pressure, temperature, humidity, precipitation, and wind, were determined. These measurements will be used later in a meteorological model to determine where the plant emissions will go when released.
Session 4 discussed the forces that influence atmospheric motion. These forces control where the winds blow, how fast they blow, as well as the overall weather conditions. What of this material would be important to our current example? The forces that control the winds and atmospheric stability are programmed into a numerical model which you would use to predict pollution transport. Therefore, an understanding of these forces is necessary. If the model results seem overly strange, then you would need to know how to make corrections and where to look in the data for errors in the forcing mechanisms. For example, let's say the model assumes a hydrostatic equilibrium in the area. You would know that hydrostatic balance is not appropriate for a small scale region such as that around and downwind of a single manufacturing plant.
Session 5 discussed the Scales of Atmospheric Motion. How does this material become important to our discussion? Based on the global wind pattern, you would expect that most weather systems would come from the west, as the prevailing westerlies in the upper atmosphere tend to move systems from west to east. The synoptic weather that influences the region would also be important. As cold front moves through, you would expect precipitation and a wind shift. The precipitation would remove the pollutants from the air and the wind shift would bring in cleaner, drier air. How would mesoscale air flow play a role? Since the site is near the coast, it is common to see a sea breeze develop, which would contribute to the transport of the pollutants. The microscale aspects of the pollution emissions might be the most significant, as these control the mixing and dilution of the pollutants.
How would material in Session 6 play a role in our discussion? Session 6 dealt with stability. This is a
critical factor in the mixing of pollution. If the atmosphere is unstable, pollutants released from the plant will be quickly mixed and diluted, and would most likely not be too dangerous. However, under more stable conditions, the pollution would be unable to mix and concentrations of ozone could reach harmful levels. The stability of the atmosphere near the plant would be a major factor to consider.
Session 7 covered the Planetary Boundary Layer. From this session we learned that the PBL height also determines the rate and degree of pollution mixing. Session 7 also covered how the moisture, surface roughness, and diurnal variations in temperature would influence the PBL and mixing of pollution. We would also realize from Session 7 that both dry and wet deposition would remove pollution from the air.
Session 8 material covered the importance of aerosols on cloud development and visibility. This material is important to our manufacturing plant example in several ways. First, aerosols released from the plant might help in cloud development in regions downwind. Second, the pollutants released can cause increased occurences of haze and smog, which may significantly degrade the visibility in the area. This would impact not only people who live in the region, but also the travel and tourism industry.
Material in Session 9 would be useful in determining what kind of model to use to predict the pollution transport. From Session 9 you would know that a Gaussian Plume Model or Plume-in-Grid Model would probably be the best to use in a situation such as this in which you are only monitoring the emissions released from one site. Session 9 would also give you the basics behind model uses and their advantages and weaknesses.
Material in session 10 actually walks you through the proper steps in setting up and running a regoinal scale, large domain model. From Session 10, you would know about the importance of preprocessors, as well as the potential problems in dealing with other types of models, such as emissions models and air quality models. With this information, you could run a model and determine, with other data and your personal experience and expertise, whether or not it would be appropriate for a manufacturing plant to open in that location and its likely impact on existing air quality levels/ambient air quality standards.
Thank you for using this course as a reference for your learning, and we hope you have found it useful.
The Shodor
Education Foundation, Inc.