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Although much of GMD's effort has been focused on obtaining long-term measurements of the remote atmosphere, it has been necessary to make observations at sites that are influenced regionally in order to understand the distribution and nature of the sources of climatically important gases. Examples include sampling sites at Harvard Forest, Massachusetts, and Niwot Ridge, Colorado, on ~500 meter towers in North Carolina, Wisconsin, and Texas, and at polluted sites in the central U.S.

It has become even more apparent in recent years that air masses can carry pollution long distances, over which compounds are transformed during transport. Large-scale pollution and dust from Asia, for example, is transported at midaltitude across the Pacific Ocean in a matter of days and impacts sites in the United States. Fires in Central America send smoke plumes across Mexico and the South-Central U.S., and dust from Africa regularly reaches the eastern U.S. GMD is in the process of implementing a new baseline station at Trinidad Head, California, in order to monitor incoming air pollution from Asia.

The importance of large-scale transport in affecting overall air quality and its impacts on public health is only beginning to be appreciated. GMD will study intercontinental transport events and improve our understanding of their impacts.

[Transport of smoke from Los Alamos, May 2000]
Transport of smoke from Los Alamos, May 2000, measured by GMD at the Southern Great Plains ARM site along with vertical aerosol profiles from a GMD aircraft program.

Scientific Questions Related to Air Quality

  • Is intercontinental transport of pollutants influencing the distribution of chemicals and particles over the United States and its adjacent oceans?
  • To what extent will increasing concentrations of atmospheric aerosols affect air quality?
  • How is air quality affected by background or "natural" trace species?
  • How are the atmospheric budgets of CO and H2 affected by source and oxidative processes?

Actions and Impacts

  • Establish West Coast Observatory at Trinidad Head, California.

    Impact: Measurement of pollution incident on the west coast of the U.S. will provide information on changing air quality baselines in the future.

  • Initiate measurements of aerosol optical depth at the West Coast Observatory.

    Impact: These measurements will allow determination of the particulate loading of air arriving on the U.S. west coast prior to interaction with the inhabited portion of the continent and, combined with other aerosol optical properties determined on the surface and from aircraft profiles, will determine effects on the radiation budget.

  • Initiate measurements of hydrocarbons, PAN, CO, H2, and other species involved in air quality issues at the West Coast Observatory.

    Impact: Hydrocarbons and PAN play important roles in regulating tropospheric ozone. GMD's Trinidad Head Observatory is well suited for these measurements because it samples both remote and regionally influenced air.

  • Continue operations with GMD's movable aerosol sampling system.

    Impact: Deploying the GMD movable aerosol sampling system along the Gulf Coast of the U.S. will provide information on aerosol particles as they enter the country and deployment in the eastern U.S. will allow analysis of particles associated with dust from Africa.

[Asian dust storm and air pollution that impacted the U.S., April 2001]
Asian dust storm and air pollution that impacted the U.S., April 2001