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| Last Updated:20/09/2018

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The NOAA Coral Reef Watch (CRW)

The NOAA Coral Reef Watch (CRW) daily 5-km satellite Bleaching Alert Area (7-day maximum) product presented here outlines the areas where coral bleaching heat stress currently reaches various bleaching stress levels, based on our satellite sea surface temperature (SST) monitoring.


SST variability is often considerably higher at the much finer 5-km spatial and daily temporal resolutions, when compared with CRW's 50-km twice-weekly SST. Due to resulting day-to-day fluctuations between stress levels in highly-variable locations, the single-day 5-km Bleaching Alert Area product does not consistently and adequately identify potentially harmful heat stress levels, especially with regard to the impact of accumulated heat stress. Rather than requiring users to examine the single-day 5-km Bleaching Alert Area product over several days, a 7-day maximum Bleaching Alert Area composite product, updated daily, was introduced in the Version 2 5-km product suite. This 7-day composite product shows the maximum stress level that a pixel has experienced during the most recent seven (7) consecutive days. The data and images are dated on the last day of the 7-day period. Additionally, the 5-km Bleaching Alert Area (7-day maximum) composite product is compatible with CRW's 
operational 50-km twice-weekly Bleaching Alert Area product. The 50-km Bleaching Alert Area product is actually based on a half-week (3 or 4 days) composite of 50-km SSTs, but with much less SST variability due to its much coarser spatial resolution. 

Even though the daily 5-km satellite Bleaching Alert Area (7-day maximum) product is presented here, it is important to note that the coral bleaching heat stress levels defined in the table below are for the daily single-day 5-km Bleaching Alert Area product. The level of heat stress at a 5-km satellite data grid, on any day, is based on the values of CRW's Daily 5-km 
Coral Bleaching HotSpot and Degree Heating Week (DHW)products for that day. The daily 5-km Bleaching Alert Area (7-day maximum) displayed above is therefore the maximum value of the seven, consecutive, daily single-day 5-km Bleaching Alert Area values in the data grid that end on the date shown in the image.

 

 


   
Definition

   
Potential Bleaching Intensity

No Stress
Bleaching Watch
Bleaching Warning
Bleaching Alert Level 1
Bleaching Alert Level 2
   
HotSpot <= 0
0 < HotSpot < 1
1 <= HotSpot and 0 < DHW < 4
1 <= HotSpot and 4 <= DHW < 8
1 <= HotSpot and 8 <= DHW
   
No Bleaching
 
Possible Bleaching
Bleaching Likely
Mortality Likely

 

Please note that locations with a current status of Bleaching Watch or No Stress recently may have been exposed to heat stress. Although these two levels classify the current heat stress condition, they do not take into account the recent stress history that is measured by the 5-km DHWproduct. When the instantaneous heat stress during the current twice-weekly time period drops to a Bleaching Watch or No Stress level from a previously higher level, this product does not present any information on accumulated heat stress during the past 12 weeks up to the previous twice-weekly period. Hence, a coral reef that is at Alert Level 2 one week may drop to Bleaching Watch or No Stress the following week. Please refer to CRW's 5-km DHW product for information on the accumulated heat stress during the past 12 weeks.
 

 
This product is updated each afternoon at about 13:30 U.S. Eastern Time.