内蒙古半干旱草原能量物质交换的微气象方法估算

根据1998年5～8月和1999年8月在中国科学院内蒙古草原生态系统定位试验站进行微气象观测的资料,作者分析了该地区能量平衡及其各分量的基本特征.结果表明:(1)净辐射通量的转化形式有明显的季节性变化,5～6月份,净辐射能大部分用于感热交换,而后期则多用于潜热交换,5～8月份的日波文比值分别为1.26,1.42,0 41和0.20.(2)观测期间,波文比的日变化特征表现为,早晚变化大不稳定,而白天则相对稳定.(3)用涡度相关方法观测的感热和潜热通量之和与同期的净辐射相比较,前者的结果偏小1 5%左右,两种方法观测到的潜热通量的差异达平均35%左右.(4)半干旱草原CO2通量有明显的日变化,在生长旺期,白天CO2通量强度可达到1.5 mg s-1m-2以上,但在生长后期,1998年和1999年8月份的白天CO2通量强度分别为0.38 mg s-1m-2和0.2 mg s-1m-2左右;其差异与草地土壤水分和植物长势有关.

The Estimate of Energy and Mass Exchanges in Inner Mongolia Semi-Arid Grassland Using Micrometeorological Methods

In order to study the energy, water and CO2 status of Semi-Arid Grassland, some micrometeorological methods were employed to measure at the Inner Mongolia Grassland Research Station, Chinese Academy of Sciences, from May to August, 1998 and in August, 1999. The main methods were Eddy Correlation (EC) and Bowen Ratio-Energy Balance (BREB). Based on the data, authors analyzed the basic characteristics of energy balance components in the area. Meanwhile, the results measured by the two methods were compared with each other. It shows that: (1) In 1998, the most of net radiation was used to the sensible exchange in May and June, and was used to latent exchange in July and August, the mean Bowen-Ratio for May, June, July, and August were 1.26, 1.42, 0.41, and 0.2, respectively. (2) During the observations, the diurnal variation characteristic of Bowen Ratio was bigger and unsteady at the sunrise and sunset, smaller and steady in the remainder of a daytime. (3) The sum of sensible and latent heat fluxes density measured by EC method was smaller than that by BREB method. (4) CO2 flux density has an obvious diurnal change, in daytime of the growing stage, the maximum of CO2 flux density were more than about 1.5 mg s-1 m-2, and in the late of growing stage (in August), the average of CO2 flux density was about 0.38 mg S-1 m-2 and 0.2 mg s-1M2 in 1998 and in 1999, respectively. The differences are related to the soil moisture and growing status of grassland.