HR: 1330h
AN: H42A-1067    [PDF]
TI: Contrasts in shallow cloud cover and rainfall intensity over deforested regions in the Amazon basin
AU: * Chagnon, F
EM: frederic@mit.edu
AF: Department of Civil & Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue Room 48-208, Cambridge, MA 02139 United States
AU: Bras, R L
EM: rlbras@mit.edu
AF: Department of Civil & Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue Room 48-208, Cambridge, MA 02139 United States
AU: Wang, J
EM: jfwang@mit.edu
AF: Department of Civil & Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue Room 48-208, Cambridge, MA 02139 United States
AB: This paper addresses the impact of human induced land-use change on local and regional atmospheric circulation. To this end, the particular case of Amazonian deforestation is investigated. The first issue investigated is the enhancement of shallow cumulus clouds over deforested regions that has been observed qualitatively and in numerical model simulations. A set of shallow cumulus cloud recognition algorithms are presented, and are applied to Geostationary Operational Environmental Satellite (GOES) visible and infrared image pairs collected over the Amazon basin. Relative statistics about the occurrence of shallow clouds over forested and deforested regions are compiled, and their significance is assessed using a Monte-Carlo approach in which landcover patterns are randomized. The sensitivity of the results to the cloud recognition algorithm and landcover randomization scale are investigated. The conditional shallow cloud statistics are also stratified with respect to the synoptic circulation pattern and antecedent soil moisture conditions in order to investigate the conditions under which shallow cumulus contrasts arise. A similar analysis is performed on data from the Tropical Rainfall Measuring Mission (TRMM) precipitation radar to investigate the effect of the landcover heterogeneities on shallow warm rain cells.
DE: 1818 Evapotranspiration
DE: 1851 Plant ecology
DE: 1878 Water/energy interactions
DE: 1899 General or miscellaneous
DE: 3322 Land/atmosphere interactions
SC: Hydrology [H]
MN: 2003 Fall Meeting