基于改进的双源模型模拟荒漠河岸胡杨林蒸散发

蒸散发是水循环和能量平衡过程中的重要组成部分,其准确量化对于深刻揭示干旱半干旱地区的生态水文过程具有重要意义。以黑河下游荒漠河岸胡杨林为研究对象,在2014和2015年胡杨主要生长季内,基于涡度相关技术实测数据,分析了蒸散发日及各物候期变化规律,结合改进的双源Penman-Monteith-Priestley-Taylor(PM-PT)模型,模拟了黑河下游荒漠河岸胡杨林蒸散发,并分析了模型的参数敏感性,得到的主要结论如下:(1)胡杨林蒸散发日变化大致呈先升高后降低的趋势。上午随着太阳辐射的逐渐增强,气温逐渐升高,蒸散速率逐渐增大,在中午12:00左右达到峰值。随后,太阳辐射减弱,气温逐渐降低,空气中相对湿度增加,胡杨叶片内外水汽压差减小,蒸散速率随之降低。(2)胡杨生长季内蒸散发整体上呈先升高后降低的趋势。2014和2015年生长季蒸散发总量分别为612 mm和658 mm,果期和种子散播期累积蒸散发为生长季内蒸散发总量的主体部分,果期内累积蒸散发分别为316 mm和348 mm,分别占各年生长季蒸散发总量的51.65%和52.87%;种子散播期内平均蒸散发略低于果期,2014和2015年胡杨林种子散播期内累积蒸散发分别为261 mm和271 mm,分别占各年生长季蒸散发总量的42.71%和41.12%,展叶期和叶变色期内平均蒸散发最低,原因在于展叶期胡杨叶片尚未完全成形,而叶变色期叶片活性逐渐降低。(3)改进的双源PM-PT模型与传统的双源Shuttleworth-Wallace(SW)模型相比,在模型结构与参数数量方面均得到了优化,其模拟精度也更高。(4)改进的双源PM-PT模型对净辐射最为敏感。

Simulating evapotranspiration of the desert riparian Populus euphratica Olive. forest based on an improved dual-source model

Evapotranspiration (ET) is a key component of water cycles and energy balance, quantification of which is important for revealing the eco-hydrological processes in arid and semi-arid areas. Taking the desert riparian Populus euphratica Olive. forest as the study object, we studied the diurnal and phonological variations of ET based on the data measured from the eddy covariance instrument, simulated ET of the P. euphratica forest using an improved dual-source Penman-Monteith-Priestley-Taylor (PM-PT) model and analyzed the parameter sensitivity. Results showed that: (1) the diurnal variations of ET of the P. euphratica forest both increased firstly, and then decreased during the growing seasons in 2014 and 2015, respectively. With the enhancement of solar radiation in the forenoon, the temperature raised gradually, ET increased and peaked at about 12:00. Afterwards, solar radiation weakened, the temperature decreased gradually, the relative humidity increased and the vapor pressure deficit decreased, and ET decreased accordingly. (2) The seasonal variations of ET of the P. euphratica forest increased firstly, and then decreased. Total ET during the growing seasons in 2014 and 2015 were 612 mm and 658 mm, respectively. ET accumulated in fruit and seed dispersal periods were the main parts, especially in fruit period. The accumulated ET were 316 mm and 348 mm, accounting for 51.65% and 52.87% of total ET in each growing season in 2014 and 2015, respectively. The average values of ET in seed dispersal period were slightly lower than those in fruit stage. The accumulated ET were 261 mm and 271 mm, accounting for 42.71% and 41.12% of total ET in each growing season in 2014 and 2015, respectively. Because the leaves of P. euphratica were not fully formed in leaf development stage and the leaf activity decreased gradually in leaf discoloration stage, the average values of ET in both stages were the lowest. (3) Compared with the traditional dual-source Shuttleworth-Wallace (SW) model, the improved dual-source PM-PT model is optimized in terms of the model structure and parameter numbers, and its accuracy is also higher. (4) The improved PM-PT model had the greatest sensitivity to net radiation.