ABSTRACT Conventional meteorological data and remotely sensed Normalized Difference Vegetation Index (NDVI) images can be proficiently combined to predict actual evapotranspiration (ETA) on different spatial and temporal scales. Up to now, however, the operational application of this approach in heterogeneous Mediterranean regions has found difficulty due to the insufficient spatial resolution of satellite sensors having high acquisition frequency (i.e. 250 m of Terra/Aqua Moderate Resolution Imaging Spectroradiometer, MODIS). The current study investigates the advantages brought for this objective by the recent availability of NDVI data taken from the Sentinel-2 MultiSpectral Instrument (MSI), which has a spatial resolution of 10 m. The investigation has been performed in two Mediterranean areas characterized by different spatio-temporal variability of vegetation cover. The first is a mountain coniferous forest, where such variability is low, while the second is a relatively small (around 10 ha) irrigated tomato field surrounded by other annual crops showing diversified growing cycles. An ETA estimation method based on NDVI data is applied in the two study areas and its performances are evaluated against ground references obtained through the elaboration of site measurements (i.e. meteorological, soil water content, and crop coefficient observations). The advantage of using MSI over MODIS NDVI images is marginal in the first case study, while is evident in the second. More particularly, such advantage is outstanding when the remote sensing method is applied in an operational mode, i.e. without using the information on the water supplied to the tomato crop by irrigation. This confirms that the utility of higher spatial resolution data is dependent not only on the fragmentation of the observed landscapes but also on the synchronicity of major vegetation growing cycles, which is influenced by both environmental and human-induced factors.

中文翻译：

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评估 Terra/Aqua MODIS 和 Sentinel-2 MSI NDVI 数据以预测地中海地区的实际蒸散量

摘要 传统气象数据和遥感归一化差异植被指数 (NDVI) 图像可以巧妙地结合起来，以预测不同时空尺度上的实际蒸散量 (ETA)。然而，到目前为止，由于具有高采集频率的卫星传感器（即 250 m 的 Terra/Aqua 中分辨率成像光谱仪，MODIS）的空间分辨率不足，这种方法在地中海异质地区的操作应用遇到了困难。当前的研究调查了最近从空间分辨率为 10 m 的 Sentinel-2 多光谱仪器 (MSI) 中获取的 NDVI 数据带来的优势。调查是在两个地中海地区进行的，这些地区的特点是植被覆盖的时空变化不同。第一个是山地针叶林，这种变异性较低，而第二个是相对较小（约 10 公顷）的灌溉番茄田，周围环绕着其他一年生作物，显示出多样化的生长周期。基于 NDVI 数据的 ETA 估计方法应用于两个研究区域，并根据通过详细的现场测量（即气象、土壤含水量和作物系数观测）获得的地面参考来评估其性能。在第一个案例研究中，使用 MSI 优于 MODIS NDVI 图像的优势很小，而在第二个案例研究中很明显。更特别的是，当在操作模式下应用遥感方法时，即不使用通过灌溉提供给番茄作物的水的信息时，这种优势是突出的。这证实了更高空间分辨率数据的效用不仅取决于所观察到的景观的碎片化，还取决于主要植被生长周期的同步性，后者受环境和人为因素的影响。