South American Biomass Burning Analysis (SAMBBA)

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Biomass burning aerosol (BBA) exerts a considerable impact on regional radiation budgets as it significantly perturbs the surface fluxes and atmospheric heating rates and its cloud nucleating (CCN) properties perturb cloud microphysics and hence affect cloud radiative properties, precipitation and cloud lifetime. It is likely that such large influences on heating rates and CCN will affect regional weather predictions in addition to climatic changes. It is increasingly recognised that biomass burning affects the biosphere but the magnitude of the effects need to quantified. However, BBA is a complex and poorly understood aerosol species because of the mixing of the black carbon with organic and inorganic species. Furthermore, emission rates are poorly quantified and difficult to represent in models. It is now timely to address these challenges as both measurement methods and model capabilities have developed rapidly over the last few years and are now sufficiently advanced that the processes and properties of BBA can be sufficiently constrained by measurements; these can be used to challenge the new aerosol schemes used in numerical weather prediction (NWP) and climate models. Amazonia is one of the most important biomass burning regions in the world, being significantly impacted by intense biomass burning during the dry season leading to highly turbid conditions, and is therefore a key environment for quantifying these processes and determining the influence of these interactions on the weather and climate of the region. Though previous large scale studies of BBA over Amazonia and its radiative impacts have been performed, these are now over a decade old and considerable scientific progress can be made towards addressing all of the above questions given the rapid advance of models and measurements in recent years. We are therefore proposing a major consortium programme, SAMBBA, a consortium of 7 university partners and the UK Met Office, which will deliver a suite of ground, aircraft and satellite measurements of Amazonian BBA and use this data to 1) improve our knowledge of BB emissions; 2) challenge and improve the latest aerosol process models; 3) challenge and improve satellite retrievals; 4) test predictions of aerosol influences on regional climate and weather over Amazonia and the surrounding regions made using the next generation of climate and NWP models with extensive prognostic aerosol schemes; and 5) assess the impact of .biomass burning on the Amazonian biosphere.The main field experiment will take place during September 2012 and is based in Porto Velho, Brazil. At this time of year, widespread burning takes place across the region leading to highly turbid conditions. The UK large research aircraft (FAAM) will be used to sample aerosol chemical, physical and optical properties and gas phase precursor concentrations. Measurements of radiation will also be made using advanced radiometers on board the aircraft and satellite data will also be utilised. The influences of biomass burning aerosols are highly significant at local, weather, seasonal, and climate temporal scales necessitating the use of a hierarchy of models to establish and test key processes and quantify impacts. We will challenge models carrying detailed process descriptions of biomass burning aerosols with the new, comprehensive observations being made during SAMBBA to evaluate model performance and to improve parameterisations. Numerical Weather Prediction and Climate model simulations with a range of complexity and spatial resolution will be used to investigate the ways in which absorbing aerosol may influence dynamics and climate on regional and wider scales. At the heart of the approach is the use of a new range of models that can investigate such interactions using coupled descriptions of aerosols and clouds to fully investigate feedbacks at spatial scales that are sufficiently well resolved to assess such processes.