Measuring
Evapotranspiration: Comparing Two Methods
A
remote automatic weather station at Oak Flats, New Mexico. (Source: US Forest
Service, http://raws.dri.edu)
Abstract:
Evapotranspiration, the combination of the evaporation
of water from the surface of the earth and the transpiration of water through
plants via photosynthesis, is the least well quantified component of the water
budget equation (P = Q + ET +ΔS). This study investigated the differences
in evapotranspiration (ET) values over Bernalillo County, NM as calculated from
in-situ weather station data using the Kimberly-Penman equation and ET values
calculated from MODIS data via the Landsat 8 program using the Penman-Monteith
formula. From February 10th, 2014 to April 30th, 2014, ET
values calculated from four different weather stations varied from 6.13 kg/m2/8-days
to 36.62 kg/m2/8-days. ET values calculated using MODIS data from
the same period of time varied from 2 kg/m2/8-days to 716 kg/m2/8-days.
ET calculations using MODIS data differed from those using weather station data
by significant percentages, ranging from 0% to 860% in some parts of Bernalillo
County. Further investigation is needed to determine the reasons for the vast
differences in ET calculated using the two different methods, and which methods
for measuring ET are more accurate.
Introduction Methods Results Discussion Conclusion Appendix A Appendix B References