NOAA-21 VIIRS Level-3 Global Binned Photosynthetically Available Radiation (PAR) Data, version 2025.0

The Photosynthetically Available Radiation (PAR) data suite provides satellite-based estimates of the downwelling solar radiation in the 400–700 nm range that is available for photosynthesis at the ocean surface. These products quantify the daily or instantaneous amount of usable light energy, expressed in moles of photons m⁻² (commonly noted as “Einstein m⁻²”), and are widely used to estimate marine primary production, interpret phytoplankton bloom dynamics, provide context for optical and biogeochemical measurements,and support ecosystem models and education on light–biology interactions.

Geophysical variables in this suite include:
- par — Daily photosynthetically available radiation (mol photons m⁻² d⁻¹)

光合有效辐射（Photosynthetically Available Radiation，PAR）数据集套件提供基于卫星反演的400–700 nm波段下行太阳辐射估算值，该波段辐射为海洋表层可用于光合作用的有效光辐射。本数据集产品可量化每日或瞬时可用光能总量，单位为光子摩尔每平方米（通常记为“爱因斯坦每平方米”，即Einstein m⁻²），被广泛应用于海洋初级生产力估算、浮游植物水华动态解析、光学与生物地球化学测量的背景支撑，以及生态系统模型构建与光-生物相互作用相关科普教育。

本套件包含的地球物理变量如下：
par：每日光合有效辐射（mol photons m⁻² d⁻¹）

以下变量同样包含于PACE L2/L3数据文件中：
l2_flags：二级处理标记（位掩码；有关flag_masks与flag_meanings的详细说明请参阅各变量属性）
ipar：瞬时光合有效辐射（mol photons m⁻² s⁻¹）