HR: 17:30h
AN: H34D-07    [Abstracts]
TI: Global Trends in Potential and Actual Evapotranspiration Based on 20 Years of Satellite Observations
AU: Fisher, J
EM: joshbfisher@gmail.com
AF: University of Oxford, UK Centre for the Environment, South Parks Road, Oxford, OX1 3QY, United Kingdom
AU: * Tu, K
EM: kevintu@berkeley.edu
AF: Department of Integrative Biology, University of California, Valley Life Science Building, Berkeley, CA 94720, United States
AB: Evapotranspiration (ET) or the flux of water to the atmosphere from soil evaporation and plant transpiration plays a central role in the global water cycle and both responds to and influences the evaporative demand of the atmosphere. Recent analyses suggest a decrease in pan evaporation as a result of reduced energy available for evaporation due to solar dimming. Our objectives are to 1) quantify temporal changes in both potential and actual ET for different regions of the globe and 2) determine if this change is consistent with reported decreases in pan evaporation. We first describe a modified Priestley-Taylor model of evaporation that we have recently developed and tested for application with satellite remote sensing. We apply the model using 20 years of satellite-based observations from the Advanced Very High Resolution Radiometer (AVHRR) along with additional satellite-based estimates of net radiation from the surface radiation budget (SRB) experiment. Together, these data provide sufficient information on surface and near-surface biophysical properties (visible and near-infrared reflectance, surface temperature, atmospheric humidity, net radiation) to estimate the both actual and potential ET. We validate the method by comparing predictions against eddy covariance measurements of latent energy flux at 16 sites from around the globe with contrasting vegetation and meteorological conditions. Temporal trends and spatial patterns in potential and actual ET will be discussed in the context of decreased pan evaporation and potential feedbacks between evaporative demand, surface energy balance and plant and soil evaporation.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 1813 Eco-hydrology
DE: 1814 Energy budgets
DE: 1818 Evapotranspiration
SC: Hydrology [H]
MN: 2007 Fall Meeting