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Convective systems and surface processes in Amazonia during the WETAMC/LBA.

Goals of the WETAMC/LBA

The Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) is designed to generate new knowledge, essential to the understanding of the processes within the ecology, hydrology, biogeochemistry and climatology of Amazonia , the impacts of the different land uses on these processes and the interactions between Amazonia and the global biogeophysical system of the planet. To accomplish these goals, the LBA includes long term monitoring through several landscape transects of the biosphere-atmosphere interaction and intensive field campaigns during the wet season, the dry season and during the transition between them. From previous studies in the Amazon region (see Amazonian Deforestation and Climate J. Gash, C. Nobre, J. Roberts, R. Victoria, Eds., John Wiley & Sons, 1996) there are significant differences between surface fluxes of heat and moisture between forested and deforested areas in the dry season. This differences are small during the wet season. The differences in the surface fluxes lead to differences in boundary layer features such as the height of the mixed layer, which have an impact on the local concentrations and long range transport of aerosol, trace gases, greenhouse gases, and atmospheric constituents in general including the ones generated by the vegetation (e.g. volatile organic compounds - VOC).

The Wet Season Atmospheric Mesoscale Campaign - WETAMC/LBA - had a focus on the local effects of deforestation, with its different impacts, as well as on the regional response to the larger scale forcing, within the lines of the LBA. The WETAMC/LBA was a joint venture between including Brazilians and Europeans scientists who joined forces with NASA/TRMM scientists , whereby a major ground validation program within TRMM, known as TRMM/LBA, was collocated with the WETAMC/LBA. The field phase of this campaign took place in the state of Rondonia in Brazil (southwest Amazonia) during January and February 1999 and had about 250 participants. TRMM/LBA had a focus on the dynamical, microphysical, electrical and diabatic heating characteristics of tropical convection in the Amazon region and a major focus on the validation of the TRMM satellite experimental products. Together, the WETAMC/LBA and TRMM/LBA campaigns represent an opportunity to study tropical convection in Amazonia and its relation to the underlying forested and deforested regions. For the long term objectives of LBA, the WETAMC and the other planned intensive field campaigns as the DRYAMC (planned for 2002), represent the means by which local measurements are integrated and related to the larger scale picture over the basin. Besides the physical climate intensive monitoring, the WETAMC included atmospheric chemistry measurements providing a complete data base to study in an integrated approach the impact of convective clouds on the atmospheric chemistry, over pasture and forest, and vice-versa, an integrated goal of LBA as whole.

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Silva Dias, M.A., A..J. Dolman, S. Rutledge, E. Zipser, P. Silva Dias, G. Fisch, C. Nobre, P. Kabat, B. Ferrier, A. Betts, J. Halverson, M. Garstang, J. Fuentes, A. Manzi, H. Rocha, J.A. Marengo, C. Morales and N.J. Bink, 2000: Convective systems and surface processes in Amazonia during the WETAMC/LBA. BAHC News, 7, 3-7.