Technical note: Improving the AWAT filter with interpolation schemes for advanced processing of high resolution data
Technical note: Improving the AWAT filter with interpolation schemes for advanced processing of high resolution data
复制标题
DOI：
10.5194/hess-20-2309-2016
复制
发表时间：
2016-01-01
影响因子：
6.3
通讯作者：
Wessolek, Gerd
中科院分区：
文献类型：
--
作者：
Peters, Andre;Nehls, Thomas;Wessolek, Gerd
称重蒸渗仪与适当的数据过滤产生最精确和无偏的降水（P）和蒸散量（ET）的信息。最近引入的用于这种数据的滤波器方案是AWAT（自适应窗口和自适应阈值）滤波器（Peters等人，2014年）。该滤波器应用自适应阈值以将显著质量变化与不显著质量变化分开，从而保证P和ET不会被高估，并且在显著质量变化之间使用步进插值。在这方面的贡献，我们表明，步进插值方案，它反映了测量系统的分辨率，可能会导致不切实际的预测P和ET，特别是如果他们需要在高时间分辨率。我们引入线性和样条插值方案来克服这些问题。为了保证中到强降水事件突然低或零通量不平滑的不利方式，一个简单的启发式选择标准，这属性，这样的降水的步骤插值。三个插值方案（步骤，线性和样条）进行了测试和比较，使用的数据集从草参考蒸渗仪1分钟的分辨率，范围从2014年1月1日至8月5日。所选择的输出分辨率为P和ET预测1天，1小时和10分钟。正如预期的那样，步骤计划产生合理的通量率仅为1天的分辨率，而其他两个计划都能够产生合理的结果，为任何决议。关于过滤值和原始数据之间的差异，样条方案返回的结果略好于线性方案。此外，该方案允许滤波数据的连续可微性，使得通量的任何输出分辨率都是合理的。由于计算负担是没有问题的任何插值方案，我们建议始终使用样条计划。
Weighing lysimeters with appropriate data filtering yield the most precise and unbiased information for precipitation (P) and evapotranspiration (ET). A recently introduced filter scheme for such data is the AWAT (Adaptive Window and Adaptive Threshold) filter (Peters et al., 2014). The filter applies an adaptive threshold to separate significant from insignificant mass changes, guaranteeing that P and ET are not overestimated, and uses a step interpolation between the significant mass changes. In this contribution we show that the step interpolation scheme, which reflects the resolution of the measuring system, can lead to unrealistic prediction of P and ET, especially if they are required in high temporal resolution. We introduce linear and spline interpolation schemes to overcome these problems. To guarantee that medium to strong precipitation events abruptly following low or zero fluxes are not smoothed in an unfavourable way, a simple heuristic selection criterion is used, which attributes such precipitations to the step interpolation. The three interpolation schemes (step, linear and spline) are tested and compared using a data set from a grass-reference lysimeter with 1 min resolution, ranging from 1 January to 5 August 2014. The selected output resolutions for P and ET prediction are 1 day, 1 h and 10 min. As expected, the step scheme yielded reasonable flux rates only for a resolution of 1 day, whereas the other two schemes are well able to yield reasonable results for any resolution. The spline scheme returned slightly better results than the linear scheme concerning the differences between filtered values and raw data. Moreover, this scheme allows continuous differentiability of filtered data so that any output resolution for the fluxes is sound. Since computational burden is not problematic for any of the interpolation schemes, we suggest always using the spline scheme.