华北平原冬小麦/夏玉米轮作田能量闭合状况分析

对华北平原冬小麦/夏玉米轮作田连续3a(2003-11-2006-10)涡度相关观测的能量闭合状况进行综合分析,并探讨下垫面对能量闭合程度的影响.结果表明,能量平衡比率(EBR)日变化规律明显,以昼夜交替时波动最大,下午略高于上午,白天能量闭合状况明显优于夜间.将湍流能的相位提前0.5h,湍流通量和有效能的匹配度及能量闭合程度均得到提高.白天EBR呈秋冬高(分别为0.98和0.94)、春夏低(分别为0.85和0.70)的季节变化特征,EBR的波动幅度依次为:夏＞秋＞冬＞春.下垫面状况对地表能量闭合程度影响显著,裸地阶段、小麦季和玉米季的年均白天EBR分别为1.11、0.94和0.74,小麦季的能量闭合状况优于玉米季；EBR波动幅度依次为:裸地阶段＞玉米季＞小麦季.观测期间,白天EBR年均值范围在0.82 ～0.97,平均0.89,较好地满足了农田通量观测对数据质量的要求.

Analysis of the Energy Balance Closure in a Winter Wheat/Summer Maize Double Cropping System in the North China Plain

In this paper, the energy balance closure of eddy covariance measurements and the effects of land surface conditions on it were analyzed in a winter wheat/summer maize double cropping system in the North China Plain from November 2003 to October 2006. The results showed that energy balance ratios （EBR） varied diurnally and the fluctuation was great in the turn of day and night. EBR in the afternoon was slightly higher than that in the morning. The energy balance closure was obviously better in the daytime than that in the nighttime. The energy balance closure was improved by shifting the phase of the turbulent fluxes （LE ＋ H ） half-hourly ahead. Daytime EBR varied seasonally. It was higher in autumn and winter （0. 98 and 0. 94, respectively） but lower in the spring and summer （0. 85 and 0. 70, respectively）. The seasonal variability of daytime EBR was in the order of summer 〉 autumn 〉 winter 〉 spring. Land surface status had significant impacts on EBR. EBR was 1.11,0. 94 and 0. 74 for the periods of bare soil, winter wheat and summer maize respectively. Energy balance closure was better in the winter wheat field than that in summer maize field. The variability of EBR was in the order of bare soil 〉 maize 〉 wheat. Annual mean daytime EBR varied from 0. 82 to 0. 97 with an average of 0. 89, indicating a satisfied data quality in the eddy covariance measurements in the farmland.