The LSD product provides an indirect measure of the effect of the combined light and thermal stress on the coral photo-system. As currently designed, the product will provide a relative measure of these effects with values ranging between 0 and 1. Corals are expected to efficiently cope with light/temperature conditions when LSD value is close to 1, but are expected to bleach when LSD value falls below 0.4.
The LSD product is updated daily and it currently has a resolution of 1/8th of a degree. The current version of the product is expressed in terms of the Excess Excitation Energy (EEE), which has units of quanta. Eventually the LSD product will be expressed as an index ranging between 1 and 0 as explained above.
This version of LSD is tuned to massive corals of the Caribbean such as those of the genus Montastraea, and may need to be refined to be applicable to other corals. Time series graphs currently are provided as an interim product showing changes in the LSD index.
The temperature data used in deriving the LSD are the current operational Coral Reef Watch satellite sea surface temperature data. This is a twice-weekly 50km (0.5 degree) product derived from the night-time only data from the AVHRR polar orbiting sensor. This temperature product has been successfully used by Coral Reef Watch for over a decade to derive products for monitoring and predicting bleaching thermal stress.
The photosynthetically active radiation (PAR) is derived from the NESDIS/STAR GOES Surface and Insolation Product suite. Hourly PAR data from this product suite are summed to derive a daily total PAR. The daily PAR totals are then used to derive an anomaly product that measures the acclimation of the corals to changing light levels from day to day. It is important to note that this is a potential weakness of the LSD product since these satellite-derived daily PAR totals do not match well with in situ measurements of daily PAR totals. There is a high likelihood that this is due to the geometric mismatch between in situ ground-based measurements and satellite-based measurements. It will therefore be important to closely monitor the consistency of the satellite-derived PAR data during the early stages of product evaluation and testing.
This product was developed by Coral Reef Watch in close collaboration with the Universidad Nacional Autónoma de México, the University of Queensland, and the University of Exeter; and with support from the the Bleaching Working Group and Remote Sensing Working Group of the Coral Reef Targeted Research (CRTR) Program.