Estimating evapotranspiration from the Amazon Basin using the atmospheric water balance

The spatio-temporal patterns of evapotranspiration (ET) in the Amazon basin are still poorly understood. Field studies in the Amazonian forest have shown that at some sites, deep roots allow trees to sustain elevated transpiration during several months of minimal rainfall, whereas at others, trees experience evident dry season water limitation. However, the few sites investigated are inadequate to characterize the conditions of transpiration throughout the basin. As a result of this uncertainty in modeling trees' access to deep soil moisture, land surface models cannot provide reliable estimates of transpiration in the region. From a basin-averaged perspective, it remains uncertain whether transpiration is water-limited, peaking during the basin's wet season, or energy-limited, peaking during the dry season when clearer skies allow for higher surface radiation. In this work, we investigate an approach to deriving a spatially-averaged ET estimate for the Amazon basin, which avoids modeling the forest's terrestrial hydrology. ET is computed as a residual of the atmospheric water balance, using basin-averaged convergence of atmospheric water vapor flux [C], precipitation [P], and tendency of total atmospheric water vapor [dw/dt] as inputs.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2006

Author dc:creator

• Karam, Hanan Nadim

Advisor dc:contributor.advisor

• Rafael L. Bras.

• Civil and Environmental Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/35086

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/35086