A Season of Eddy-Covariance Fluxes Above an Extensive Water Body Based on Observations from a Floating Platform
A Season of Eddy-Covariance Fluxes Above an Extensive Water Body Based on Observations from a Floating Platform
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DOI：
10.1007/s10546-019-00490-z
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发表时间：
2019-12-04
影响因子：
4.3
通讯作者：
Bernhofer, Christian
中科院分区：
文献类型：
--
作者：
Spank, Uwe;Hehn, Markus;Bernhofer, Christian
涡动协方差（EC）技术被用来确定地球表面和低层大气之间的质量和能量通量在高时间分辨率。尽管EC技术在陆地站点的频繁和成功的使用，其应用于水面是罕见的。我们提出了一个赛季的EC测量上进行的Rappbode水库，德国最大的饮用水水库。水库中心的一个浮动观测平台用于观测不受周围陆地表面影响的通量，因此代表了实际的水-大气交换。感热通量的时间模式是颠倒的陆地相比，因为最大值和最小值分别发生在夜间和白天。对于蒸发不受水的可用性限制的地点，潜热通量和蒸发出乎意料地低。夏秋两季的日蒸发量分别仅为FAO草地参考蒸发量的50%和75%。测量的不确定性和能量平衡关闭的影响被排除作为潜在的因素，因此，低值似乎是一个大的水面的一般特征。观测到的二氧化碳通量的特点是在一个典型的湖泊和水库的范围内的独特的日变化。然而，与其他内陆沃茨相比，甲烷通量较低。
The eddy-covariance (EC) technique is used to determine mass and energy fluxes between the Earth's surface and the lower atmosphere at high temporal resolution. Despite the frequent and successful use of the EC technique at terrestrial sites, its application over water surfaces is rare. We present one season of EC measurements conducted on the Rappbode Reservoir, Germany's largest drinking water reservoir. A floating observation platform in the centre of the reservoir is used for observations of fluxes that were unaffected by surrounding land surfaces and therefore representative of the actual water-atmosphere exchange. The temporal patterns of sensible heat flux are inverted compared to land sites, since the maxima and the minima occur at night and day respectively. The latent heat flux and the evaporation are unexpectedly low for a site where evaporation is not limited by the availability of water. The daily totals in summer and autumn are only 50% and 75% of the potential evaporation assessed by the FAO grass-reference evaporation, respectively. Measurement uncertainties and the effects of the energy balance closure are ruled out as potential factors, so that low values appear to be a general feature of large water surfaces. The observed carbon dioxide fluxes are characterized by distinctive diurnal variations in a typical range for lakes and reservoirs. However, the methane fluxes are low compared to other inland waters.