HR: 1330h
AN: H23B-10    [Abstracts]
TI: Actual and Apparent Evapotranspiration in the Environment: A Study Toward the Resolution of the Evaporation Paradox
AU: * Kahler, D M
EM: dmk57@cornell.edu
AF: Civil and Environmental Engineering, Cornell University, Hollister Hall, Ithaca, NY 14853 United States
AU: Brutsaert, W
EM: whb2@cornell.edu
AF: Civil and Environmental Engineering, Cornell University, Hollister Hall, Ithaca, NY 14853 United States
AB: Over the past 50 years evaporation from pans has been shown to be decreasing. Until recently, pan evaporation was widely accepted to be proportional to landscape evapotranspiration. This decrease stands out against data that show an increase in global precipitation. This paradox can be explained using Bouchet's complimentary relationship. At the root of the paradox is that evaporation pans measure apparent potential evaporation. Apparent potential evaporation is only equal to the actual potential evapotranspiration (and actual evapotranspiration) under moist conditions. According to the complimentary relationship, evapotranspiration from a landscape will decrease if the conditions drop below the potential level (i.e. the land dries out). This decrease will liberate available energy that will accelerate evapotranspiration from an evaporation pan (or any other moist surface). We present a comparison of actual evapotranspiration measured at the First ISLSCP Field Experiment (FIFE) in the Konza Prairie, Kansas and at the Atmospheric Radiation Measurement (ARM) program in the Washita River Basin, Oklahoma with apparent potential evaporation data from nearby evaporation pans compiled by the National Climactic Data Center (NCDC). The data generally support the theory underlying the complimentary relationship.
DE: 1655 Water cycles (1836)
DE: 1818 Evapotranspiration
DE: 3322 Land/atmosphere interactions
SC: Hydrology [H]
MN: 2005 Joint Assembly