Rj. Qualls et H. Gultekin, INFLUENCE OF COMPONENTS OF THE ADVECTION-ARIDITY APPROACH ON EVAPOTRANSPIRATION ESTIMATION, Journal of hydrology, 199(1-2), 1997, pp. 3-12
Several methods have been proposed to estimate areal evapotranspiratio
n from common meteorological data. The advection-aridity approach is o
ne such method which requires no site-calibrated parameters, and uses
measurements at a single elevation which are commonly available from a
meteorological station. The method is based on a complementary relati
onship between actual and potential evapotranspiration which postulate
s that a decrease in actual evapotranspiration will result in a comple
mentary or symmetrical increase in potential evapotranspiration for a
given energy input. In this paper, the advection-aridity equations wer
e rewritten to isolate terms which account for available energy, advec
tion or drying power of the air, and sensible heat flux. The advection
-aridity method was tested on a daily basis with data for 43 days coll
ected from a Bat, semi-arid grassland over a 4 month period. The influ
ence of each of the terms was examined to determine its relative influ
ence in generating the complementary or symmetrical structure between
actual and potential evapotranspiration. Advection and sensible heat f
lux were found to be very significant, whereas available energy was no
t. A comparison between reference values of evapotranspiration E-en ob
tained from the energy budget with measurements of net radiation, grou
nd heat flux, and sensible heat fluxes obtained by the eddy correlatio
n method, and evapotranspiration estimates from the advection-aridity
method, E-aa, produced a small root mean square error of 13.1 W m(-2).
However, significant bias was present in that E-aa overestimated E-en
for large values of E-en, but underestimated E-en for small values. M
easurement error and external energy sources not accounted for in the
complementary relationship or the advection-aridity approach are discu
ssed as potential causes of this bias.