科尔沁湿草甸参考作物蒸散发模拟分析

为探明气候变化下干旱半干旱地区湿草甸参考作物蒸散发(ET₀)影响因子,使用FAO 56 P-M模型对科尔沁湿草甸ET₀进行模拟,利用涡度相关系统对模型的适用性进行评价,并通过通径分析及指标敏感性分析对ET₀的影响因子进行辨识。结果表明:(1)小时尺度模拟精度最高,日尺度次之,月尺度较差,小时尺度上晴、阴、雨3种天气条件下模拟效果不同,晴天最优,阴雨天较差。(2)ET₀年内变化呈单峰曲线状,生长季明显高于非生长季,集中在3—10月,占全年89.79%。生长季典型晴天ET₀逐小时分布特征遵循倒“U”单峰型变化规律。(3)通径分析结果显示,对ET₀的通径系数以及对回归方程估测可靠程度E的总贡献均表现为VPD(饱和水汽压差) > T_min(最低气温) > R_n(冠层表面净辐射)>u₂(2 m高度风速),即VPD为影响ET₀最重要的因子;指标敏感性分析中,在去除VPD后引起的E变化最大,说明ET₀对VPD的变化最为敏感,其次为u₂、T_min和R_n。

Simulation of reference crop evapotranspiration and analysis of the factor effect in Horqin wet meadow

The FAO 56 P-M model was used to simulate reference crop evapotranspiration (ET₀) and explore the influencing factors of ET₀ for the Horqin wet meadow in the arid and semi-arid areas under climate change. The applicability of the model was evaluated by the eddy covariance system, and the influencing factors of ET₀ were identified by path analysis and index sensitivity analysis. Results showed that: (1) The accuracy of hour-scale simulation was the highest, followed by day-scale simulation, and the monthly scale simulation was poor.The simulation effect was also different under sunny, cloudy and rainy weather conditions on the hourly scale,sunny days were best, rainy days were worse. (2) The change of ET₀ in the year presented a single-peak curve, and the growth season was significantly higher than that in the non-growth season, mainly from March to October, accounting for 89.79% of the annual ET₀. The hourly distribution of ET₀ in typical sunny days during the growing season follows the single peak pattern of inverted "U". (3) The path coefficient of ET₀ and the total contribution to the estimation reliability of regression equation E were shown as VPD > T_min > R_n > u₂, VPD is the most important factor affecting ET₀. In the sensitivity analysis of indicators, the largest change of E is caused by the removal of VPD, indicating that ET₀ is the most sensitive to the change of VPD, followed by u₂, T_min and R_n.