HR: 0800h
AN: GC21A-0149    [Abstracts]
TI: Do Clouds Follow Deforestation Over the Amazon?
AU: Chagnon, F
EM: frederic@alum.mit.edu
AF: Ralph M. Parsons Laboratory, Massachusetts Institute of Technology, 15 Vassar Street, 48-336C Cambridge, MA 02139, Cambridge, MA 02139, United States
AU: Bras, R
EM: rlbras@mit.edu
AF: Ralph M. Parsons Laboratory, Massachusetts Institute of Technology, 15 Vassar Street, 48-336C Cambridge, MA 02139, Cambridge, MA 02139, United States
AU: * Wang, J
EM: jfwang@mit.edu
AF: Ralph M. Parsons Laboratory, Massachusetts Institute of Technology, 15 Vassar Street, 48-336C Cambridge, MA 02139, Cambridge, MA 02139, United States
AU: Williams, E
EM: ekagww@gmail.com
AF: Lincoln laboratory, Lexington, MA 02420, Lexington, MA 02139, United States
AU: Betts, A
EM: Akbetts@aol.com
AF: Atmospheric Research, 58 Hendee Lane, Pittsford, VT 05763, United States
AU: Renno, N
EM: nrenno@umich.edu
AF: Atmospheric, Oceanic and Space Sciences University of Michigan, 1531C Space Research Building 2455 Hayward St., Ann Arbor, MI 48109, United States
AU: Machado, L
EM: machado@cptec.inpe.br
AF: Instituto Nacional de Pesquisas Espaciais Centro de Previsão de Tempo e Estudos Climáticos, Rodovia Pres. Dutra, km 40, Cachoeira Paulista/S, 12630-000, Brazil
AU: Knox, R
EM: rknox@mit.edu
AF: Ralph M. Parsons Laboratory, Massachusetts Institute of Technology, 15 Vassar Street, 48-336C Cambridge, MA 02139, Cambridge, MA 02139, United States
AU: Bisht, G
EM: gbisht@MIT.EDU
AF: Ralph M. Parsons Laboratory, Massachusetts Institute of Technology, 15 Vassar Street, 48-336C Cambridge, MA 02139, Cambridge, MA 02139, United States
AB: A statistical analysis of ten years of remote sensing observations of cloudiness from geo-stationary satellites (GOES) has produced the strongest evidence of the impact of land cover over the deforested Amazon on the development of convective clouds. Shallow clouds are prone to appear over deforested surfaces while high clouds occur over forested surface but much less frequently. A understanding of the physical mechanisms responsible for the observations is possible using simultaneous atmospheric soundings at a forest and a pasture site during the Rondonian Boundary Layer Experiment (RBLE-3). The atmospheric boundary layer over the forested area is conditionally more unstable characterized by large values of the convective available potential energy (CAPE). At the same time the boundary layer has high negative energy. The occurrence of deep convection over the forested region is then limited by available lifting mechanisms. More active shallow convection over the deforested area is caused by stronger lifting mechanisms mainly due to the mesoscale circulations driven by deforestation induced surface heterogeneities. Convection is shallow because the available convective energy is limited over the deforested region. We also found some evidence that smoke from biomass burning in the deforested area may significantly reduce the formation of shallow clouds arguably through reducing the drop sizes of cloud water.
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
DE: 1637 Regional climate change
DE: 1840 Hydrometeorology
DE: 3307 Boundary layer processes
DE: 3314 Convective processes
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting