1.2. What environmental properties of reefs can we measure using remote sensing (Table 2)?
Afunda mental environmental parameter for coral reefs is sea surface temperature (SST). Although the National Oceanic and Atmospheric Administration (NOAA) have been routinely measuring SST since the mid 1970s, the techniques and sensors did not evolve sufficiently until the mid 1980s. As a result, we now have accurate daily SST measurements since 1985, and post processing techniques such as those employed by the Advanced Very High Resolution Pathfinder SST project, have provided consistent global SST data for the period 1985 to present (Kilpatrick et al., 2001). Beginning experimentally as early as 1997, the National Oceanic and Atmospheric Administration (NOAA) has taken advantage of this long data series by developing a SST climatology upon which they have based a number of satellite global 50-km resolution experimental products (initially SST Bleaching ‘‘HotSpot’’ anomalies and then Degree Heating Week (DHW) products) as indices of coral bleaching related thermal stress. The coral bleaching HotSpot is not a typical climatological SST anomaly. It is a measure of the occurrence of the hottest SST for a region and as such is an anomaly that is not based on the average of all SST, but on the climatological mean temperature of the climatologically hottest month (i.e. the maximum of the monthly mean SST