Karst area in southwestern China is characterized with complex topography, low soil water capacity, and fragile ecosystem. Accurate estimation of regional evapotranspiration is essential for ecological restoration and water resources management in southwestern China. Based on observed evapotranspiration and meteorological data, this study aimed to estimate spatial upscale evapotranspiration using the MOD15A2 LAI and Penman-Monteith-Leuning (PML) model, within which the stomatal conductance and soil wetness index were optimized by the least-square method. The results showed that the modeled ET well fitted with the observations, with the determination coefficient, Nash efficiency coefficient and RMSE being 0.85, 0.75 and 1.56 mm·d-1, respectively. The ET exhibited clear seasonality and reached to its maximum in summer, coinciding with vegetation phenology. The annual ET ranged from 534 to 1035 mm·a-1, with strong spatial heterogeneity which highly related to the precipitation. Evapotranspiration may be affected by precipitation as well as land use types.
西南喀斯特地区地形起伏大、土壤保水持水性差、生态环境脆弱.准确估算区域尺度蒸散发对研究喀斯特地区植被恢复、水资源管理等具有重要意义.本文以桂西北喀斯特植被恢复区为例,基于野外实测气象和蒸散发数据,采用最小二乘法对Penman-Monteith-Leuning(PML)模型中气孔导度土壤湿度指数进行参数优化,并结合MOD15A2叶面积指数进行空间外推,实现了区域尺度上长时序蒸散发的估算.结果表明: 研究区蒸散发模拟值与实测值有较好的一致性,模型确定系数、纳什系数和均方根误差分别为0.85、0.75和1.56 mm·d-1.蒸散发表现出季节变化特征,并与植被生长季物候特征一致,夏季蒸散量达到峰值.研究区年蒸散量在534～1035 mm,陆面蒸散发的空间分布呈现差异性,受降水的空间分布影响较大.年蒸散发可能不仅受到降水因素的影响,还与人类活动和土地利用类型有关.
Keywords: Penman-Monteith equation; evapotranspiration; leaf area index; scaling up.