5 Conclusion
This study is the first to document information on the comparison of 13
reference crop evapotranspiration models against lysimeter measurements
in a humid alpine meadow, northeastern Qinghai-Tibetan Plateau, we found
that the radiation-based models performed better than combination models
and temperature-based models. In addition, the combination models and
most radiation-based models tended to underestimate measured ET, whereas
temperature-based models tended to overestimate measured ET during the
whole study period. Specifically, all models tended to underestimate ET
during the growing season and overestimate ET during the non-growing
season, suggesting that these models should be calibrated or modified by
local lysimeter data when extrapolated to other regions. Furthermore,
the 1963 Penman and FAO-24 Penman models demonstrated better
performances than the recommended FAO-56Penman-Monteith (PM), suggesting
that older Penman equations may be superior to the standard FAO-56
Penman-Monteith model, especially considering the good performance of
the 1963 Penman model in this study. Given the outstanding performance
of the DeBruin-Keijman and Priestley-Taylor models, which require few
meteorological inputs, we thus recommend that these two models can be
used in other alpine meadows that have similar climates to that of the
study region, to improve ET estimation.