两种尺寸蒸渗计测量实际蒸散差异性试验研究

利用试验资料，对蒸散面积2 m²和4 m²两种尺寸蒸渗计测量蒸散量的差异及原因进行了研究。结果表明：2 m²蒸渗计与4 m²蒸渗计所测蒸散量具有很好的一致性，但2 m²蒸渗计所测蒸散量总体要略偏大，日蒸散量平均偏大4%，月蒸散量平均偏大10%，年蒸散量相对偏大5%；典型天气条件下，2 m²蒸渗计和4 m²蒸渗计所测蒸散量的日变化过程基本相同，小时蒸散量的差异表现为晴天时白天显著偏大、夜晚略有偏小，阴天时白天略偏大、夜晚较接近，雨天时白天、夜晚均非常接近的特征。晴天和阴天时，2 m²蒸渗计比4 m²蒸渗计测量日蒸散量分别偏大1.78 mm和0.12 mm，雨天时偏小0.11 mm；2 m²蒸渗计比4 m²蒸渗计测量蒸散量总体偏大的原因，主要是2 m²蒸渗计土壤温度显著高于4 m²蒸渗计和建造时间不同导致土体内部土壤湿度产生差异。

Difference of Actual Evapotranspiration Measured by Two Sizes Lysimeters

Based on observed data, the difference of actual evapotranspiration and its causes are analyzed by comparing the lysimeter with evaporation area of 2 square meters ( referred to as 2 m² lysimeter) and the lysimeter with evaporation area of 4 square meters (referred to as 4 m² lysimeter). The results showed that measured evapotranspiration by two lysimeters was in good consistency, but the 2 m² lysimeter's evapotranspiration was generally slightly larger than the 4 m² lysimeter with 4% more for daily evapotranspiration, 10% more for monthly evapotranspiration, and 5% more for annual evapotranspiration; Under different types of synoptic conditions, the two lysimeter's evapotranspiration had a same diurnal variation. In sunny days and cloudy days, hourly evapotranspiration measured by the 2 m² lysimeter was larger than 4 m² lysimeter during the day, but slightly smaller or very close during the night. The hourly evapotranspiration measured by the two lysimeters was very close in the rainy days. The daily evapotranspiration measured by the 2 m² lysimeter is 1.78 mm more than the 4 m² lysimeter in the sunny days and 0.12 mm more in the cloudy days, respectively, and 0.11 mm less in the rainy days; Analysis the reasons for the 2 m² lysimeter measured evapotranspiration is generally slightly larger than 4 m² lysimeter, on the one hand, the soil temperature of 2 m² lysimeter is significantly higher than that of 4 m² lysimeter. On the other hand, it can be the different construction time of two sizes of lysimeters caused the soil moisture to produce difference,resulted in the difference of evapotranspiration.