Evaluation of five complementary relationship models for estimating actual evapotranspiration during soil freeze-thaw cycles

Abstract

The actual evapotranspiration (ETa) estimated models based on the complementary relationship (CR) theory have been applied in various climatic conditions around the world. However, in cold regions, the evaluation of the adaptability of the CR models was performed through complete freeze-thaw cycles, and the adaptability during various periods of soil freeze-thaw cycles has not been evaluated separately. Daily ETa was measured by lysimeters on alpine grassland in the Qilian Mountains from 2010 to 2017, and the measurements were used to evaluate five CR models during the thawing, thawed, freezing, and frozen periods, respectively. The five models comprised the advection-aridity (AA) model of Brutsaert and Stricker, the GG model proposed by Granger and Gray, Morton's CR areal evapotranspiration (CRAE) model, the Han model, and Brutsaert model. The results show that all five CR models were only able to estimate daily ETa during the thawed period. None of the models could estimate the daily ETa during the thawing, freezing, or frozen periods. The basic assumptions of the CR may not be suitable for non-thawed periods with complex energy processes, and no complementary behavior was shown in the non-thawed periods. The CR models must be applied with caution during freeze-thaw cycles in cold regions. HIGHLIGHTS Actual daily evapotranspiration (ETa) from 2010 to 2017 was measured in alpine grassland in the Qilian Mountains.; Complementary relationship evapotranspiration models could estimate ETa only during the thawed period.; No complementary behavior was shown during the thawing, freezing, or frozen periods in the cold regions.;

Keywords

• complementary relationship
• estimation
• evaluation
• evapotranspiration
• freeze-thaw cycle