Experiment for Regional Sources and Sinks of Oxidants (EXPRESSO): An overview

This paper presents an overview of the Experiment for Regional Sources and Sinks of Oxidents (EXPRESSO) including the objectives of the project, a det ailed description of the characteristics of the experimental region and of field instrumentation deployed, and a summary of the main results of all co mponents of the experiment. EXPRESSO is an international, multidisciplinary effort to quantify and better understand the processes controlling surface fluxes of photochemical precursors emitted by vegetation and biomass burni ng along a tropical forest to savanna gradient in central Africa. The exper iment was conducted at the beginning of the dry season in November-December 1996. Three main research tools were deployed during this period: (1) the French research aircraft (Avion de Recherche Atmospherique et de Teledetect ion, Fokker 27), instrumented for chemistry and flux measurements (CNRS- Fr ance), (2) two satellite receivers for in situ acquisition of National Ocea nic and Atmospheric Administration-advanced very high resolution radiometer (NOAA-AVHRR) imagery for fire detection (EC-JRC, Ispra, Italy), and (3) a 65-m walkup tower installed at a tropical forest site in the Republic of Co ngo (National Center for Atmospheric Research, Boulder, Colorado). Average dynamic and turbulence characteristics over savanna and forest ecosystems w ere retrieved from aircraft measurements. They illustrate the complex atmos pheric circulation occurring in this region ill the vicinity of the Intertr opical Convergence Zone. Satellite receivers were operated three times a da y to produce maps of fire distribution. Statistics and mapping of burned su rfaces from NOAA-AVHRR and ERS-Along Track Scanning Radiometer space system s have been developed. The influence of biogenic and biomass burning source s on the chemical composition of the lower atmosphere was studied through b oth aircraft and tower measurements. The EXPRESSO field campaign was follow ed by modeling efforts (regional and global scales) in which model componen ts are evaluated using the experimental data.