Technical note: Using distributed temperature sensing for Bowen ratio evaporation measurements
Technical note: Using distributed temperature sensing for Bowen ratio evaporation measurements
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技术说明：使用分布式温度传感进行鲍文比蒸发测量
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
H. Savenije
中科院分区：
文献类型：
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作者：
B. Schilperoort;M. Coenders;Willem Luxemburg;C. J. Rodríguez;C. Vaca;H. Savenije
摘要。分布式温度传感（DTS）技术的精度和空间分辨率的快速提高使其能够在水文和大气科学中使用。介绍了利用DTS测量波温比（BR-DTS）来估算感热通量和潜热通量的方法。波温比是由dts测量的空气温度和湿球温度的垂直剖面得出的。然而，在之前的研究中，测量的温度没有得到验证，电缆也没有屏蔽太阳辐射。此外，BR-DTS方法以前还没有在森林上空进行过测试，那里的温度梯度很小，气柱中的能量储存变得很重要。本文验证了DTS湿球温度和空气温度测量的准确性，并将所得的波温比和热通量与涡动相关方差数据进行了比较。2016年8月，BR-DTS在荷兰中部混交林的一座46 米高的塔上进行了性能测试。平均树高为26至30 米，温度在树冠下、树冠内和树冠上测量。利用垂直温度分布曲线计算了空气柱的潜热和感热蓄积量。我们发现太阳辐射对温度测量有显著影响，导致偏差高达3 K。通过安装屏幕，阳光造成的误差减少到1 K以下。风速似乎对测量的湿球温度的影响很小，无论是在树冠下面还是在树冠上面。经过简单的质量控制后，DTS测量的Bowen比率与涡流相关方差（EC）估计值具有良好的相关性（r2 = 0.59）。BR-DTS和EC之间的平均能量平衡闭合性较好，BR-DTS方法的平均低估值为3.4 W m−2。然而，在白天，BR-DTS方法高估了可用能量，而在夜间，BR-DTS方法估计的可用能量更负。这种差异可能与生物质储热有关，但在本研究中被忽略了。BR-DTS方法平均高估潜热通量18.7 W m−2,RMSE = 90 W m−2。感热通量平均低估10.6 W m−2,RMSE = 76 W m−2。一旦能量平衡中的不确定性降低，BR-DTS的估计就可以得到改善。然而，例如，应用Monin-Obukhov相似理论可以为感热通量提供独立的估计。这将使高度不确定和难以确定的净可用能量的确定变得多余。
Abstract. Rapid improvements in the precision and spatial resolution of distributed temperature sensing (DTS) technology now allow its use in hydrological and atmospheric sciences. Introduced by ) is the use of DTS for measuring the Bowen ratio (BR-DTS), to estimate the sensible and latent heat flux. The Bowen ratio is derived from DTS-measured vertical profiles of the air temperature and wet-bulb temperature. However, in previous research the measured temperatures were not validated, and the cables were not shielded from solar radiation. Additionally, the BR-DTS method has not been tested above a forest before, where temperature gradients are small and energy storage in the air column becomes important. In this paper the accuracy of the wet-bulb and air temperature measurements of the DTS are verified, and the resulting Bowen ratio and heat fluxes are compared to eddy covariance data. The performance of BR-DTS was tested on a 46 m high tower in a mixed forest in the centre of the Netherlands in August 2016. The average tree height is 26 to 30 m, and the temperatures are measured below, in, and above the canopy. Using the vertical temperature profiles the storage of latent and sensible heat in the air column was calculated. We found a significant effect of solar radiation on the temperature measurements, leading to a deviation of up to 3 K. By installing screens, the error caused by sunlight is reduced to under 1 K. Wind speed seems to have a minimal effect on the measured wet-bulb temperature, both below and above the canopy. After a simple quality control, the Bowen ratio measured by DTS correlates well with eddy covariance (EC) estimates (r2 = 0.59). The average energy balance closure between BR-DTS and EC is good, with a mean underestimation of 3.4 W m−2 by the BR-DTS method. However, during daytime the BR-DTS method overestimates the available energy, and during night-time the BR-DTS method estimates the available energy to be more negative. This difference could be related to the biomass heat storage, which is neglected in this study. The BR-DTS method overestimates the latent heat flux on average by 18.7 W m−2, with RMSE = 90 W m−2. The sensible heat flux is underestimated on average by 10.6 W m−2, with RMSE = 76 W m−2. Estimates of the BR-DTS can be improved once the uncertainties in the energy balance are reduced. However, applying, for example, Monin–Obukhov similarity theory could provide independent estimates for the sensible heat flux. This would make the determination of the highly uncertain and difficult to determine net available energy redundant.