Beginning in the early 1990s, frequent observations of haze and degraded visibility were reported at the Big Bend National Park in West Texas. Because visibility appeared to decline further over ensuing years, the U.S. Environme ntal Protection Agency and National Park Service, with governmental agencies from Mexico, sponsored a preliminary study in 1996 to investigate the causes of park haze. Three years later, findings indicated that fine particulate sulfur compounds were playing the major role in the increasing levels of haze in the park. It appeared that the particulates were being transported from sources both in the United States and Mexico; however, greater understanding of particulate sources and transport processes was needed. Thus, an enhanced study followed.

The Big Bend Regional Aerosol and Visibility Observational study —known as the BRAVO study—began in 1999 with the primary objective of identifying the causes of haze in the park. This very large, collaborative study enlisted numerous participants with sponsorship from the U.S. Environme ntal Protection Agency, National Park Service, and Texas Commission on Environmental Quality, with technical support from the N ational Oceanic and Atmospheric Administration’s (NOAA) Air Resources Laboratory and the Electric Power Research Institute. The Desert Research Institute (DRI), in collaboration with NOAA’s Air Resources Laboratory, oversaw technical management of the BRAVO study through its Cooperative Institute for Atmospheric Sciences and Terrestrial Applications  (CIASTA). This DRI organization is a collaborative venture among NOAA and academic and research facilities within the University and Community College System of Nevada. CIASTA is directed by DRI’s Dr. Mark Green who, with NOAA’s Marc Pitchford, CIASTA Federal Program Officer, played a leading role in the design and management of the BRAVO study, as well as in writing and publishing the Final Report for the Big Bend Regional Aerosol and Visibility Observational Study.

BRAVO constituted one of the largest and most comprehensive visibility-field studies and air-quality modeling efforts ever conducted in the United States. As compared to the 1996 preliminary study, BRAVO encompassed a broader scope of field activities and an expanded spatial study domain—moving further into northeastern and southern regions of the United States and into the Gulf of Mexico. An intensive monitoring period lasted four months from July through October 1999.

State-of-the-science techniques in air-quality monitoring and modeling, as well as laboratory and statistical analyses, were utilized involving over 60 scientists representing various U.S. agencies and a cadre of research and academic institutions. Inert atmospheric tracers quantified the transport and dispersion properties of the atmosphere over the state of Texas. Evaluation and analysis of the data were followed by a modeling effort that continued five years beyond the close of the 1999 field study.