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Air Pollution in the US and China

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Airpollution is a global problem that requires collaboration among countries.   Understanding specific air quality problems in different regions through satellite and ground-based data is one step toward improving air quality across the globe. 

Questions to Explore:

  • How do particulate matter and total aerosol amount correlate during days of bad air quality?
  • How does air quality on a “bad” day in the U.S. Northeast compare to air quality on a “bad” day in the cities of Shanghai and Beijing in China?

 

Data Frames for this Chapter:

Giovanni Air Quality Instance

  • Fine Particulate Matter (Air Quality, Giovanni)
  • Aerosol Optical Depth (Air Quality, Giovanni)
  • UV-Aerosol Absorbing Index (Air Quality, Giovanni)
  • Sulfate Aerosol Optical Depth (Monthly MODIS-GOCART Aerosol Optical Thickness Inter-comparison, Giovanni)
  • Nitrogen Dioxide Column Amount (OMI Beta Version, Giovanni)
  • Aerosol Particle Radius (NEO)
  • Vertical Curtain Plots (A-Train, Giovanni)
  • Google Earth visualization

 

Visualizations for this Chapter:

Location Map and Coordinates:

map location

coordinates

 

EPA AIRNow is a network of in situ observations from stations across the country.  The monitors at the stations measure fine particulate matter (PM2.5), among other pollutants, close to the surface where they can affect human health.  Aerosol Optical Depth (AOD) is a satellite-based quantity and a measure of the total aerosols in a vertical air column.  PM2.5 data can be used to evaluate the satellite AOD and the ability of the satellite instruments to detect ground-based aerosols. AOD can also be used to complement ground-based measurements where, for example, there is limited monitoring data available. In many cases, AOD and PM show similar spatial patterns, but interferences can affect each dataset differently.  In particular, dust and particles in the upper atmosphere, as well as cloud cover, can interfere with AOD calculations:  instruments measuring AOD cannot "see" through clouds.

Let’s look at two different regions to understand the correlation between PM2.5 monitors and AOD calculations.

The East Coast has some of the worst pollution in the United States.  Let’s zoom into the mid-Atlantic East Coast to see some of the air pollution issues in this area.  Especially during summer months, air pollution becomes a significant risk for people living in these areas. 

(Note:  all of the images in this chapter are linked to larger versions;  click the image to see the larger version.)

Area Plots (Air Quality)

  1. Select the coordinates above.
  2. Parameter:           Fine Particulate Matter – PM 2.5

    Aerosol Optical Depth at 550 nm

  1. Temporal:            Begin Date = 2007, August 1

    End Date = 2007, August 5

  1. Select Visualization: Lat-Lon Map, Time-Averaged
  2. Generate Plot

 

Fine Particulate Matter - PM 2.5

particulate matter on east coast

Aerosol Optical Depth

aerosol optical depth on east coast

These images show some of the same general patterns, but we need to determine if there is a correlation between the two.  To do this, let’s generate a scatter plot.

 

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Scatter Plot (Air Quality)

  1. Select the same coordinates above. 
  2. Parameter:           Fine Particulate Matter – PM 2.5
  3. Aerosol Optical Depth at 550 nm

  1. Temporal:            Begin Date = 2007, August 1

    End Date = 2007, August 5

  1. Select Visualization:     Scatter Plot
  2. Generate Plot

scatter plot of AOD and PM concentrations

You can also fit a line to the image (shown above.)

  1. Under Plot Preferences, select ‘Yes’ for Line Fitting. 

With an r-value of .78, this plot shows a significant correlation between Aerosol Optical Depth and EPA Particulate Matter monitors.  Now let’s examine the east coast in the fall months.  As you will see, not all of the correlations turn out as well as the previous example.    

 

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Area Plot (Air Quality)

  1. Choose the ‘Air Quality’ instance.
  2. Select the coordinates above.
  3. Parameter:           Fine Particulate Matter – PM 2.5

    Aerosol Optical Depth at 550 nm

  1. Temporal:            Begin Date = 2007, October 21

    End Date = 2007, October 26

  1. Select Visualization:     Lat-Lon Map, Time-Averaged
  2. Generate Plot

Fine Particulate Matter PM 2.5

particulate matter concentration on east coast

Aerosol Optical Depth

fine particulate matter concentrations on east coast

 

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Scatter Plot (Air Quality)

  1. Select the same coordinates above. 
  2. Parameter:          Fine Particulate Matter – PM 2.5

    Aerosol Optical Depth at 550 nm

  1. Temporal:            Begin Date = 2007, October 21

    End Date = 2007, October 26

  1. Select Visualization:     Scatter Plot
  2. Generate Plot

scatter plot of AOD and PM on east coast

 

These two days have very different correlation results.  One of the main factors affecting this difference is the height and type of the aerosol concentration.  The MODIS satellites might not detect air pollution due to obstruction from clouds, which block its view.   Weather conditions or other factors could have prevented the MODIS satellite from detecting pollutants. 

 

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United States and China: Air Quality Comparison

The 2008 Olympic Games in Beijing, China aroused discussion on the air quality in China and other developing countries.  Although China has raced into industrial dominance on the world stage, it has not significantly implemented air quality standards, which were an important result of the 1970s environmental movement in the United States.  If we look across the world to Shanghai and Beijing, we can analyze air pollution in two of China’s developing cities. 

Although the United States uses more total fossil fuels in the form of natural gas, oil, and coal than China (even with a much smaller population!), emissions in the United States are subject to more regulation of harmful air pollutants by the US Environmental Protection Agency.  These pollutants include Nitrogen Dioxide, Ozone, Particulate Matter (PM2.5 and PM10), Carbon Monoxide, Sulfur Dioxide, and Lead.

Beginning with the EPA’s Clean Air Act of 1977, the government began to regulate the amount of pollutants emitted by sources.  Sulfur Dioxide, which is emitted mainly by large-scale industrial coal burning power plants, was one of these regulated pollutants.  Since that time, sulfur dioxide concentrations have drastically decreased by 6.5 million tons since the 1980s (Office of Air and Radiation, Clearing the Air.)  

Sulfur Dioxide is more concentrated in Shanghai and Beijing for several reasons.  First of all, China’s existing power plants are not subject to the same pollution standards as power plants in the United States.  Secondly, China’s total emissions are growing each year.  Although not as high as the United States, emissions are increasing rapidly as China continues a swift pace of industrialization.  However, most power plants and industrial activity are centered in large industrial cities (Li, 1990.)  Very large cities along the coast of China are relatively close in proximity.  The power plants in the United States are generally spread across the country, but centered in rural settings such as Ohio, West Virginia, and Pennsylvania.  The map of the overall sulfur concentrations measured by the GOCART model shows this contrast.

Area Plot (Monthly MODIS-GOCART Aerosol Optical Thickness Inter-comparison)

  1. Go to the Monthly MODIS-GOCART Instance.
  2. Choose the world view (i.e. default coordinates) 
  3. Parameter:          Sulfate Aerosol Column Depth
  4. Temporal:            Begin Date = 2000, January

    End Date = 2006, December

  1. Select Visualization: Lat-Lon Map, Time-Averaged
  2. Generate Plot

sulfate concentrations across the world

Looking at the map we can see that China has the highest concentration of sulfate aerosols.  Other notable areas are the Eastern United States (PA, WV, Ohio) and Europe.  In addition, we can see contributions from India, another developing country like China.  Biomass burning from fires in equatorial Africa is also visible.  Below is a map of the U.S. sulfate aerosol concentrations and their location. 

Zoom into these coordinates for the United States:

coordinates for USA

map of sulfates across US

 

and for parts of China:

coordinates for parts of china

sulfate concentration across parts of china

 

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Area Plot (OMI)

Unlike sulfur, there is little difference in nitrogen dioxide concentrations between the United States and China.  In fact, the United States might have larger nitrogen dioxide concentrations across its entire span.  The rural areas of China (western half) have low nitrogen dioxide concentrations, as you can see in the zoomed map.

  1. Go the OMI Beta Instance
  2. Choose the world view (i.e. default coordinates) 
  3. Parameter:         NO2 Column Amount
  4. Temporal:            Begin Date = 2007, June 1

    End Date = 2007, August 30

  1. Select Visualization: Lat-Lon Map, Time-Averaged
  2. Generate Plot

nitrogen dioxide concentrations across the world

Again, we can zoom into the United States coordinates and the China coordinates from the example above.

nitrogen dioxide concentration in US

nitrogen dioxide concentration across parts of China

 

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Area Plot (NEO)

Besides analyzing just the type of aerosol – either nitrogen dioxide or sulfates – we can also look at the particle size of pollutants in China.  The particles sizes of aerosols in China are larger, which is due to the type and source of emissions. 

  1.  Select Aerosol Particle Radius (MODIS).  Choose a monthly resolution.
  2. Select the various time periods:     January 2007
  3. August, 2007

    November 2006

  1. Look at the world map of the particle sizes.

particle radius size across the world

  1. Now zoom into the areas of Los Angeles (the most polluted city in the United States) and Shanghai/Beijing to get a closer look.

los angeles zoomed map

zoomed map of Shanghai/Beijing

As we can see from the graph, the radii of aerosols are larger in China.  However, the EPA has determined that smaller particles are actually more harmful than larger particles!  Because of this, the EPA did not revise its regulation on particulate matter   less than 10 micrometers (PM10 <10μm.)  This does not mean that China has ‘better’ pollution than the United States.  It simply points to another difference in the type of pollutants in China.      

Whereas only 12% of the United States’ energy mix consists of coke and coal, 52% of China’s energy mix consists of coke and coal.  Because coal burns less cleanly than other sources such as oil or natural gas, coal creates more pollution problems.  In addition, the efficiency of coal use in China is about a third lower than the international advanced level. (Zulin et al. 2001)   

 

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Area Plot (Air Quality)

Let’s look more at the air pollution affecting China.

  1. Select the following coordinates:

coordinates for Chinese cities

  1. Parameter:          Aerosol Optical Depth at 550 nm
  2. Temporal:            Begin Date = 2007, August 1

    End Date = 2007, August 1

  1. Select Visualization: Lat-Lon Map, Time-Averaged
  2. Generate Plot

Aerosol Optical Depth over Shanghai and Beijing

 

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Google Earth extension:

Now, we can import these plots to Google Earth to see a plot of the area.

  1. Make sure that Google Earth is downloaded and operating on your computer.
  2. Click ‘Download Data’ above the map projection.
  3. Choose the KMZ download option by clicking the icon. 
  4. The KMZ should directly import into Google Earth. 

google earth map of AOD concentrations in china

 

Because China does not have a ground-based monitoring system as extensive as the one in the U.S., we must rely more on satellite based measurements for tracking air pollution in that country Total column satellite measurements such as AOD cannot tell us whether the aerosols are at the surface where they can affect human health, or higher up in the atmosphere. However, we can look at the vertical distribution of the aerosols, from the parameters in the A-Train instance.

 

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Vertical Curtain Plots (A-Train)

  1. Select an orbit near the Yellow Sea in China.  (The North Polar Projections can provide a more accurate location.  However, you should experiment with different map views to find the best and closest orbits.) 

North Polar Projection

Orbit used in this example

north polar projection

Descending Orbit projection

General location of South China Sea and Shanghai/Beijing

descending orbit projection

  1. Map View: North Polar Projection
  2. Temporal: Orbit Date: August 4, 2007
  3. Parameter: Cloud/Aerosol Classification (Vertical Feature Mask)
  4. Generate Visualization

calipso vertical curtain of aerosols

 

The color scale differentiates between clouds in the stratosphere and lower atmosphere, as well as aerosols.  It also displays the total attenuation – or the total amount of light scattered – and serves as an indication for the haze over an area. 

 

Create similar plots to understand the vertical profile for a larger area:

Ascending Orbit on August 2, 2007

Descending Orbit on August 3, 2007

calipso vertical curtain for aerosols calipso vertical curtain for aerosols

NOTE:  Remember to Update Map after each date change because the orbit varies slightly each day. 

 

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Google Earth extension:

Again, follow these steps to import to Google Earth.

  1. Make sure that Google Earth is downloaded and operating on your computer.
  2. Click ‘Download Data’ above the map projection.
  3. Choose the KMZ download option by clicking the icon. 
  4. The KMZ should directly import into Google Earth. 

Visualization Problems:

  1. If you cannot see these plots in the same map window, click the clock at the top of the map. 
  2. Then click 'Restrict Time to Currently Selected Folder'

google earth 3-D visualization

Use the key pads on the right to zoom into the cities.  Note that above and below, the Forbidden City of the Chinese emperors is near the center of Beijing.

Shanghai Map:

shanghai

Beijing Map:

Beijing

These plots show considerable haze across Shanghai and Beijing.  In addition, there are many clouds and aerosols in the lower atmosphere near Beijing. 

As a last step, combine the Google Earth 3-D plots above with the Aerosol Optical Depth plot created earlier.  This gives a more complete picture of the air pollution in Shanghai and Beijing.

AOD and 3-D plot curtains of Chinese cities

 

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Questions for Further Investigation

  • How is the EPA AIRNow PM 2.5 dataset different from MODIS’s Aerosol Optical Depth dataset? 
  • What are some differences between air quality in the US cities and Chinese cities?
  • In Los Angeles and Shanghai, aerosols fall under what EPA standards for particulate matter?  PM 2.5? PM 10?   Look at the radius size for aerosols in the NEO dataset.  (Remember PM 2.5 refers to a diameter of 2.5 micrometers, not the radius.)  Specify the health risks associated with the different sizes of the particulate matter.
  • Are the two Korean nations likely to be affected by China’s air pollution?
  • Will the air quality emissions restrictions for the Olympics be effective and detectable by the satellite observations from MODIS and OMI?

 

References

Office of Air and Radiation. Clean Air Markets Division (6204N) EPA-430F-02-009. ‘Clearing the Air: The Facts about Capping and Trading Emissions’ www.epa.gov/airmarkets. May 2002.

Li, W., et al. 1990. Industrial Geography of China. Science Press.

Zulin, Shi and Wangsheng, Su. (2001) Energy Use and Environmental Pollution in China.  China-India-Japan-United States Cooperation to Promote Clean Air. South North Institute for Sustainable Development.  Beijing, China.

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Last updated: Apr 08, 2014 09:53 AM ET