Abstract The reliability of short-term weather forecast provided by COSMO model in simulating reference evapotranspiration (ET0) was evaluated in 7 study sites distributed in 4 countries (Italy, Norway, Romania and Spain). The main objective of the study was to assess the optimal scenario for calculating ET0, using the FAO-56 Penman-Monteith (PM) equation, by separately considering the accuracy in the use of “past” and “forecast” data input. Firstly, each forecasted variable (air temperature, Tair; relative humidity, RH; wind speed, u2; solar radiation, Rs) and ET0 were compared with in situ observations at hourly and daily scales. Moreover the seasonality effect in the forecast performance was evaluated. Secondly, simulated ET0 were computed every three days with: (i) a “past scenario” that used the observed data input measured in situ during the previous three days, (ii) a “forecast scenario” that used the forecasted input variables for the next three days; and compared with (iii) actual ET0 obtained from the in situ measured data. A general good agreement was found between observed and forecasted agro-meteorological parameters at the different explored time-scales. The best performance was obtained for Tair and Rs, followed by RH and u2. Globally, the comparison between ET0 from the measured and forecasted data input showed high performance, with R2 and RMSE of 0.90 and 0.68 mm d−1. ET0 simulations resulted more accurate using the “forecast scenario” (1.7% overestimation), rather than using the “past scenario” (2.6% underestimation). These results open promising perspectives in the use of forecast for ET0 assessment for different agriculture practices and particularly for irrigation scheduling under water scarcity conditions.

中文翻译：

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比较使用过去和预测的天气数据来估计参考蒸发量

摘要 在分布在 4 个国家（意大利、挪威、罗马尼亚和西班牙）的 7 个研究点对 COSMO 模型提供的模拟参考蒸散量（ET0）的短期天气预报的可靠性进行了评估。该研究的主要目标是通过分别考虑使用“过去”和“预测”数据输入的准确性，使用 FAO-56 Penman-Monteith (PM) 方程评估计算 ET0 的最佳方案。首先，将每个预测变量（气温，Tair；相对湿度，RH；风速，u2；太阳辐射，Rs）和 ET0 与每小时和每日尺度的现场观测进行比较。此外，还评估了预测性能中的季节性影响。其次，每三天计算一次模拟 ET0：(i) 使用前三天现场测量的观测数据输入的“过去情景”， (ii) 使用未来三天预测输入变量的“预测情景”；并与 (iii) 从原位测量数据获得的实际 ET0 进行比较。在不同探索的时间尺度上观测到的和预测的农业气象参数之间普遍存在良好的一致性。Tair 和 Rs 获得了最佳性能，其次是 RH 和 u2。在全球范围内，来自测量和预测数据输入的 ET0 之间的比较显示出高性能，R2 和 RMSE 分别为 0.90 和 0.68 mm d-1。ET0 模拟结果使用“预测情景”（高估 1.7%）比使用“过去情景”（低估 2.6%）更准确。