Validation of Hourly Global Horizontal Irradiance for Two Satellite-Derived Datasets in Northeast Iraq
Validation of Hourly Global Horizontal Irradiance for Two Satellite-Derived Datasets in Northeast Iraq
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DOI：
10.3390/rs10101651
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发表时间：
2018-10
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通讯作者：
Bikhtiyar Ameen;H. Balzter;C. Jarvis;E. Wey;Claire Thomas;M. Marchand
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作者：
Bikhtiyar Ameen;H. Balzter;C. Jarvis;E. Wey;Claire Thomas;M. Marchand
若干部门出于各种目的需要全球水平辐照度（GHI）数据。然而，高质量的长期原位GHI测量序列的可用性是有限的。因此，一些研究试图通过重新分析气候数据或卫星图像来估算GHI。验证对于在缺乏地面记录数据的区域后期使用全球健康指数数据至关重要。本研究有助于过去进行的验证helioclim3第5版（HC3v5）和哥白尼大气监测服务的研究，使用辐射服务第3版（CRSv3）的每小时GHI数据，这些数据来自伊拉克东北部9个地面站的卫星衍生数据集（SDD），这些数据以前没有使用过。验证采用像素位置的站点数据和每个站点附近的另外两个数据点进行，这在文献中很少见到。两个sdd都很好地捕捉了地面数据的时空变化趋势。晴空和晴空条件下，晴空指数的相关系数大多在0.94 ~ 0.97之间，而阴天条件下，晴空指数的相关系数在0.51 ~ 0.72 ~ 0.82 ~ 0.89之间。大多数情况下，偏差是负的，除了三个正的情况。在全天和晴空条件下，其范围分别为- 7%至4%和- 8%至3%。对于多云天气，偏差是正的，并且在不同的站点之间有所不同，从16%到85%不等。在全天和晴空条件下，均方根误差（RMSE）分别在12-20%和8-12%之间。相比之下，在阴天条件下，RMSE范围明显更高：超过56%。晴空条件下，清晰度指数的偏差和均方根误差与GHI的偏差和均方根误差基本相同。每小时GHI SDD的空间变异性仅相差2%，这取决于站点位置与每个站点周围数据点的比较。基于一个月每小时GHI的平均值和标准差，两个SDDs的变化与地面数据非常相似。不同时间尺度的台站数据和该区域具有GHI记录的台站数量少是本分析的主要局限性。
Several sectors need global horizontal irradiance (GHI) data for various purposes. However, the availability of a long-term time series of high quality in situ GHI measurements is limited. Therefore, several studies have tried to estimate GHI by re-analysing climate data or satellite images. Validation is essential for the later use of GHI data in the regions with a scarcity of ground-recorded data. This study contributes to previous studies that have been carried out in the past to validate HelioClim-3 version 5 (HC3v5) and the Copernicus Atmosphere Monitoring Service, using radiation service version 3 (CRSv3) data of hourly GHI from satellite-derived datasets (SDD) with nine ground stations in northeast Iraq, which have not been used previously. The validation is carried out with station data at the pixel locations and two other data points in the vicinity of each station, which is something that is rarely seen in the literature. The temporal and spatial trends of the ground data are well captured by the two SDDs. Correlation ranges from 0.94 to 0.97 in all-sky and clear-sky conditions in most cases, while for cloudy-sky conditions, it is between 0.51–0.72 and 0.82–0.89 for the clearness index. The bias is negative for most of the cases, except for three positive cases. It ranges from −7% to 4%, and −8% to 3% for the all-sky and clear-sky conditions, respectively. For cloudy-sky conditions, the bias is positive, and differs from one station to another, from 16% to 85%. The root mean square error (RMSE) ranges between 12–20% and 8–12% for all-sky and clear-sky conditions, respectively. In contrast, the RMSE range is significantly higher in cloudy-sky conditions: above 56%. The bias and RMSE for the clearness index are nearly the same as those for the GHI for all-sky conditions. The spatial variability of hourly GHI SDD differs only by 2%, depending on the station location compared to the data points around each station. The variability of two SDDs is quite similar to the ground data, based on the mean and standard deviation of hourly GHI in a month. Having station data at different timescales and the small number of stations with GHI records in the region are the main limitations of this analysis.