Methodology for optimizing a photosynthetically active radiation monitoring network from satellite-derived estimations: A case study over mainland Spain

Clustering analysis has previously been applied to determine locations to monitor solar radiation. However, this is the first implementation for PAR stations in mainland Spain. Another novelty developed in this work is the distribution employed for specific sites within each cluster. The outcome achieved using clustering analysis was compared to those obtained using three other methods: two methods without clustering analysis and the third where clustering is performed but not optimizing the number of clusters. In one technique without clusters, the largest region is split into two new sub-regions, similar to the clustering analysis with optimization. In the second without clustering analysis, since the data variability was not previously addressed, the region divided is those with the largest combined effect of variance and size. The results fully justify using a clustering process; however, clustering without optimization is the worst performing method.