Conclusions

The wide and varying discrepancy in ET values calculated using the two different methods compared in this study highlights the necessity for using more accurate formulas that take into account the specific conditions observed at the given location. While using the alfalfa-specific Kimberly-Penman equation as a standard across the RAWS network may be useful for standardizing the Keech-Byram index for comparison across stations, it may not be the most accurate method for measuring actual ET at most sites in which RAWS stations are located. The four weather stations that were used in this study are located at different elevations and different ecosystems; perhaps there is no one formula that would provide accurate ET values for all four sites. Local, direct ET measurements would be required to derive an accurate formula for each site. Future studies will involve calculating ET using different values for r_a and r_s that more accurately represent the conditions found at each weather station location and comparing those to ET values calculated using MODIS data.

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