Comparison between Photosynthetically Available Radiation (PAR) estimated from MODIS and GOES over the Gulf of Mexico

Photosynthetically Available Radiation (PAR) is an important parameter to estimate marine primary productivity (PP), where MODIS daily PAR is generated by an instantaneous PAR (iPAR) around local solar noon. The uncertainties associated with MODIS daily PAR need to be quantified in order to understand the uncertainties in the estimated PP. On the other hand, Geostationary Operational Environmental Satellite system (GOES) provides estimates of hourly solar radiation product (24 images per day) over North America, which can be integrated to produce daily PAR. In this study, both GOES iPAR and daily PAR are used to compare with the corresponding MODIS products to understand uncertainties in MODIS daily PAR products and to understand how multiple measurements per day can improve daily PAR estimates. While GOES iPAR and MODIS iPAR showed excellent consistency over cloud-free regions, their daily PAR products showed some degree of discrepancy due to variable cloud cover.