Analyses of aerosol cloud nucleating and optical properties during GoAmazon

Description

During the Green Ocean Amazon 2014/2015 (GoAmazon) field experiment, the Atmospheric Radiation Measurement (ARM) Mobile Facility provided state-of-the-art instruments for observing clouds and aerosol optical and microphysical properties in the city of Manacapuru, Brazil. This site is located approximately 100 km downwind of the city of Manaus and experiences the extremes of heavy pollution when the Manaus plume regularly intersects it and a pristine atmosphere otherwise. This region is also weakly influenced by biomass burning emissions during the dry season. During this long-term experiment, an unprecedented large set of clouds and aerosol properties was acquired at high temporal resolution. We have examined the relationship between aerosol optical properties and their influence on cloud condensation nuclei (CCN) activation using collocated ground-based remote sensor measurements from ARM deployments at Manacapuru, during the GoAmazon field experiment. Our analysis shows that the large variation in the ratio of CCN concentration to aerosol concentration is closely related to shifts in both the size distribution and single-scattering albedo of the aerosol. Some case studies were also analyzed in more detail in order to identify aerosol sources. We have also assessed the spatial distribution of the direct radiative forcing of biomass burning aerosols over Amazonia using simultaneous CERES (Clouds and the Earth's Radiant Energy System) and MODIS (Moderate Resolution Imaging Spectrometer) sensors retrievals from 2000 to 2009. The mean direct RF of aerosols at the top of the atmosphere during the biomass burning season for this 10-year period was -5.2 ± 2.6 W/m².