Radiation, clearness and clear-day indices at 37 FLUXNET sites

This database comprises the information used to calculate the clear-day and clearness indices in 37 FLUXNET sites distributed across the globe and their values. Data are obtained using the FLUXNET data set (Baldocchi, 2001, Olson, 2004) and the \"First European Comprehensive Solar Irradiance Data Exploitation project'' (SOLID) (Haberreiter, 2017, Scholl, 2016).

The results obtained with this database are published in Muñoz & Ochoa (2021). Climatic traits on daily clearness and cloudiness indices. This article inspects for climatic traits in the shape of the probability density function (PDF) of the clear-day (c) and the clearness (k) indices. The analysis was made for shortwave radiation (SW) at all sites and for photosynthetically active radiation (PAR) at 28 sites. We identified three types of PDF, unimodal with low dispersion (ULD), unimodal with high dispersion (UHD), and bimodal (B), with no difference in the PDF type between c and k at each site. Looking for regional patterns in the PDF type we found that latitude, global climate zone, and Köppen climate type have a weak and the Holdridge life a stronger relation with c and k PDF types.

本数据库涵盖用于计算全球37个通量网（FLUXNET）站点的晴空日指数与晴空指数及其对应数值的全部相关信息。
本数据集的数据来源于通量网（FLUXNET）数据集（Baldocchi, 2001；Olson, 2004）以及「首届欧洲综合太阳辐射数据开发项目」（SOLID）（Haberreiter, 2017；Scholl, 2016）。

基于本数据库得到的研究成果已发表于Muñoz与Ochoa（2021）的论文《逐日晴空与云量指数的气候特征》。该文围绕晴空日指数（c）与晴空指数（k）的概率密度函数（PDF）形态展开气候特征分析。本次分析覆盖所有站点的短波辐射（SW）数据，以及其中28个站点的光合有效辐射（PAR）数据。研究共识别出三类概率密度函数形态：低离散单峰型（ULD）、高离散单峰型（UHD）与双峰型（B）；且各站点的晴空日指数与晴空指数所对应的PDF类型并无差异。在探寻PDF类型的区域分布规律时，研究发现：纬度、全球气候分区及柯本气候类型与晴空日、晴空指数的PDF类型关联较弱，而霍尔特里奇生命地带（Holdridge life zone）与二者的关联则更为显著。