科尔沁温带草甸能量平衡的日季变化特征

Diurnal and seasonal variations of energy balance over Horqin meadow

利用2011年9月—2012年10月涡度相关数据和气象观测资料,对科尔沁温带草甸能量平衡的日季变化特征进行分析.结果表明:研究区涡度相关系统全年的能量平衡闭合度为0.77,不同时期能量平衡闭合度的大小顺序为:生长季>裸土期>积雪期.能量平衡各分量日变化均呈单峰曲线形式,净辐射日变化峰值出现在12:00前后,其余分量的峰值出现时间都稍有滞后.净辐射季节变化呈单峰曲线形式,年平均值为5.71 MJ·m-2·d-1.潜热通量季节变化趋势与净辐射相似,年平均值为2.84 MJ·m-2·d-1.感热通量季节变化呈双峰曲线形式,峰值分别出现在4月和9月,年平均值为1.87 MJ·m-2·d-1.土壤热通量的最大值(3.47 MJ·m-2·d-1)出现在4月,9月以后开始转为负值.全年能量平衡各分量收支比例的大小顺序为:潜热通量>感热通量>土壤热通量,潜热通量、感热通量和土壤热通量分别占净辐射的49.8%、35.8%和3.1%.全年波文比的季节变化近似"U"型,平均值为1.61;生长季数值较小且较为平稳,平均值为0.18;非生长季数值较大且波动较大,平均值为2.39.

Based on the measurements of eddy flux and micrometeorological factors, this paper ana- lyzed the diurnal and seasonal variations of energy balance over Horqin meadow. The results showed that annual energy balance ratio （EBR） of the eddy eovariance system was 0.77, and EBR was biggest in growing season, middle in bare soil period and smallest in snow-covered period. Diurnal variations of energy components all presented bell-shaped curves. The peak of net radiation ap- peared around 12：00 and peaks of other components slightly lagged. Seasonal variation of net radia- tion presented a single-peak curve, and the annual average was 5.71 MJ.m-2 . d-1. Seasonal va- riation of latent heat flux was similar to that of net radiation, and the annual average was 2.84 MJ . m-2 . d-1. Seasonal variation of sensible heat flux presented a double-peak curve, and the peaks appeared in April and September, respectively. Annual averaged sensible heat flux was 1.87 MJ.m-2 . d-1. Maximum soil heat flux （3.47 MJ .m-2 . d-1 ） appeared in April, and the soil heat flux became negative after September. Annual budget ratios of energy components presen- ted a decreasing order of latent heat flux, sensible heat flux and soil heat flux, which accounted for 49.8%, 35.8% and 3.1% of net radiation, respectively. Seasonal variation of Bowen ratio （fl） presented a ＇U＇ shape, and the annual average was 1.61. fl was small （0.18） and relatively sta- ble in growing season, while it was large （2.39） and fluctuated severely in non-growing season.