priority should be given to programs which aid in assessing long-term trends of background ozone and PM.
Establish new capabilities to provide long-term measurements and vertical profiles of reactive compounds and PM that will allow meaningful examination of long-range transport and trends in background concentrations.
These two recommendations will require providing support to:
develop uniform and traceable standards on a global basis for calibration of both gas-phase and aerosol measurements;
improve measurement technologies for use in current observational platforms (such as ground-based air quality monitoring networks, commercial aircraft, and balloons/sondes), and in new potential platforms such as “supersites” for measuring a comprehensive suite of compounds in remote locations, and unmanned aerial vehicles for long-duration sampling of the atmosphere over a wide range of altitudes;
integrate measurements obtained from different observational programs and platforms with a particular focus on integrating remotely sensed satellite observations with in situ aircraft and ground-based measurements;
promote observational programs specifically designed to address chemical and meteorological data requirements for the improvement and validation of models.
Responsibility for carrying out this work should be clearly assigned to a U.S. federal agency (or interagency) research program, and the U.S. should play a leadership role in fostering international cooperative research and observational activities to enhance our understanding of global air quality changes.
In conclusion, the committee wishes to emphasize that developing global-scale research and observational programs inherently requires substantial international cooperation. In recent years, the atmospheric chemistry research community has successfully coordinated multinational programs to study issues such as stratospheric ozone depletion and the atmospheric effects of aviation. Studies of global air quality change should build upon these successes, and yet will likely require even deeper levels of international cooperation. For instance, quantifying long-range transport of air pollutants would be greatly aided by an