ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-9-11481-2009 Land use change suppresses precipitation Junkermann W. 1 Hacker J. 2 Lyons T. 3 Nair U. 4 Forschungszentrum Karlsruhe, IMK-IFU, Garmisch-Partenkirchen, Germany Airborne Research Australia, Flinders University, Adelaide, Australia Murdoch University, Perth, Australia National Space Science Technology Center, Huntsville, Alabama, USA 08 05 2009 9 3 11481 11500 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/9/11481/2009/acpd-9-11481-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/9/11481/2009/acpd-9-11481-2009.pdf

A feedback loop between regional scale deforestation and climate change was investigated in an experiment using novel, small size airborne platforms and instrument setups. Experiments were performed in a worldwide unique natural laboratory in Western Australia, characterized by two adjacent homogeneous observation areas with distinctly different land use characteristics. Conversion of several ten thousand square km of forests into agricultural land began more than a century ago. Changes in albedo and surface roughness and the water budget of soil and the planetary boundary layer evolved over decades. Besides different meteorology we found a significant up to now overseen source of aerosol over the agriculture. The enhanced number of cloud condensation nuclei is coupled through the hydrological groundwater cycle with deforestation. Modification of surface properties and aerosol number concentrations are key factors for the observed reduction of precipitation. The results document the importance of aerosol indirect effects on climate due to nanometer size biogenic aerosol and human impact on aerosol sources.

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