MCR LTER: Coral Reef: In Situ Light Data, ongoing since 2021

This time series describes light (PAR, 400-700 nm) recorded in the air, on the surface, and at depth (17.1 m depth) at the LTER2 fore reef site. Surface data originate from twin cosine collectors (Hobo/Onset brand, model S-LIA-M003) attached to USB micro weather stations (Hobo/Onset brand, model H21-USB). Sensors are attached to the roof of the waterfront building at the UCB Gump station (-17.490598, -149.826208) with the sensors ~ 6 m above sea level. In situ light is recorded with a single PME miniPAR logger fitted with a Li-COR LI-192 cosine correct PAR sensor attached to a PME miniWiper. The sensor is mounted underwater with the top of the sensor at 17.1 m depth. The objective is to measure K dPAR , the diffuse attenuation coefficient for PAR wavelengths, over long periods. The technique relies on the assumption that ~96% of surface PAR is transmitted through the air-sea interface when sun altitudes are > 46° and wind speeds are < 5 m s-1 (Gregg and Carder 1990). Departures from this assumption degrade the estimation of subsurface PAR from surface PAR, which is required to calculate K dPAR .