华北平原冬小麦农田蒸散量

Evapotranspiration of winter wheat field in North China Plain.

以华北平原冬小麦农田为研究对象，采用涡度相关技术和热红外遥感技术，研究了不同环境条件下土壤含水量与农田蒸散量及作物冠层温度的关系．结果表明，冬小麦在农田郁闭（LAI≥3）、晴天和土壤相对含水量低于田间持水量65％的情况下，蒸发比值日变化正午前后出现相对较低且平稳的变化趋势．在晴天情况下，农田潜热通量与作物冠层温度日变化和季节变化均呈极显著的非线性相关关系，而冠气温差、农田相对蒸散量则与0～100cm土层的土壤相对含水量密切相关以13：30～14：00的平均冠层温度值Tc、日最高气温Ta max和日净辐射总量Rnd为统计数据，确立了冬小麦农田日蒸散量ETd（mm）估算简化模式参数．

By using eddy covariance and remote sensing techniques, the relationships between winter wheat soil moisture content and farmland evapotranspiration or canopy temperature were analyzed at field scale under various environmental conditions in the North China Plain. The results showed that when the soil moisture content was below 65% of field capacity, the evaporative fraction under full canopy was low and stable during the middle part of clear days. Under clear sky condition, there was a good non-linear correlation between latent heat flux and crop canopy temperature with diurnal and seasonal patterns. The temperature difference between crop canopy and air as well as the relative evapotranspiration had a close link to the relative moisture content of 0 - 100 cm soil layer. Based on the in situ measurements of daily evapotranspiration amount （ ETd ）, daily net radiation flux （ Rnd, mm）,average canopy temperature （Tc, ℃） from 13：30 to 14：00, and daily maximum air temperature （ Ta max ℃ ） during the field experiment, the parameters of simplified estimation model for daily evapotranspiration were established.