A Study of Fitting a Swamp Meadow Ecosystem Evapotranspiration to a Model Based on the Penman-Monteith Equation

Abstract EN

To accurately estimate the magnitude and seasonal dynamics of evapotranspiration (ET) over an important a swamp meadow in the Fenghuoshan permafrost region, we employed the Food and Agriculture Organization- (FAO-) Penman-Monteith (P-M) model.

The model was also used to investigate changes in the crop coefficient ( k c ), which was calculated as the ratio of the measured actual ET ( ET a from the eddy covariance (EC) system) to the reference ET ( ET 0 from the P-M model).

The results indicated a reference ET of 900 mm/year from the swamp meadow ecosystem, which was significantly higher than the actual ET (426 mm/year).

The reference ET peaked from April to July, while the actual ET was primarily in growing season.

The value of k c exhibited significant seasonal variations within the range 0.3–1.0 with a mean k c of 0.55 during the growing season.

The daily k c showed a linear increase with R n and T a and a linear decrease with the VPD.

With respect to the biotic factors, the biomass exhibited a significant positive correlation with k c .

Thus, a daily k c model is developed as a function of the VPD, R n , T a , and biomass.