Evolution of the Daily Global 5km Satellite Coral Bleaching Heat Stress Product Suite
(Versions 1, 2, and 3)

 

I. Version 1 Product Suite

NOAA Coral Reef Watch's (CRW) Version 1 experimental daily global 5km (0.05 degree exactly) satellite coral bleaching heat stress monitoring product suite was a new-generation version of the current operational twice-weekly 50km (0.5 degree exactly) monitoring product suite. The Version 1 5km suite included sea surface temperature (SST), SST Anomaly, Coral Bleaching HotSpot, Degree Heating Week (DHW), and Bleaching Alert Area products, matching the core operational 50 km satellite products. A 5km version of CRW's other 50km operational products, such as the global Virtual Stations and the automated Satellite Bleaching Alert Email System, would come soon after CRW determined representative satellite pixel locations for select reef sites in the global tropical oceans. The Version 1 5km product suite provided two major improvements over the operational 50km products (click here to see a detailed description):

  1. New-generation SST Analysis for Deriving the 5km Product Suite

    1. Improved Data Density and Spatial and Temporal Resolutions.

    2. Improved SST Quality with New-Generation SST Algorithm.

  2. Improved Climatology

The Version 1 daily global 5km product suite, released experimentally on July 5, 2012, significantly advanced CRW's capability for remotely monitoring in near-real-time coral bleaching heat stress. These 5km satellite products would soon comprise the core of CRW's new-generation Decision Support System (DDS) for coral reef management. With higher spatial and temporal resolution of the Version 1 satellite coral bleaching heat stress products, CRW was able to begin providing service at or close to reef-scales.


Detailed Description of 5km Product Suite Version 1

Development of the next-generation 5km product suite was accomplished through a collaboration of NOAA Coral Reef Watch, the University of South Florida, NASA-Ames, the UNEP World Conservation Monitoring Centre, and the Cooperative Institute for Research in Environmental Science, with funding support from the NASA Biodiversity and Ecological Forecasting program, the NOAA Coral Reef Conservation Program, and the NOAA/NESDIS Ocean Remote Sensing Program.

 



 

II. Version 2 Product Suite

NOAA Coral Reef Watch's (CRW) Version 2 experimental daily global 5km (0.05 degree) satellite coral bleaching heat stress monitoring product suite, released May 5, 2014, was a next-generation version of the operational twice-weekly 50km (0.5 degree) suite. The high-resolution Version 2 5km suite was based on the NOAA/NESDIS operational daily global 5km geostationary-polar-orbiting (Geo-Polar) Blended Night-only SST Analysis. Products included sea surface temperature (SST), SST Anomaly, Coral Bleaching HotSpot, Degree Heating Week (DHW), a 7-day maximum Bleaching Alert Area, and a 7-day SST Trend. On February 17, 2015, CRW added 212 5km Regional Virtual Stations/Bleaching Heat Stress Gauges, based on the Version 2 5km product suite and CRW's Coral Bleaching Heat Stress Outlook product; these were much more comprehensive than the heritage 50km Virtual Stations product. On October 24, 2016, CRW also released a free, automated 5km Bleaching Alert Email System based on the Version 2 5km products.

Improvements of the Version 2 5km products over the heritage 50km products were derived from the following:

  1. Next-generation SST Analysis

    1. Higher SST quality with a next-generation SST algorithm.

    2. Multiple satellites/sensors used for producing the blended SST analysis.

    3. Higher spatial and temporal resolutions and greater data density.

  2. New Climatology

    1. The climatology used for CRW's Version 2 5km Geo-Polar Blended Night-only products was produced using night-only values for the 28-year period, 1985-2012, from the 4km Advanced Very High Resolution Radiometer (AVHRR) Pathfinder Version 5.2 SST (PFV5.2) data set, an official NOAA climate data record. CRW used the 28-year period to produce 12 monthly mean climatologies. The 5km climatological average values were bias-adjusted to match the 5km SST data and re-centered to the time-center of the operational 50km climatology to maintain consistency with the heritage 50km products.

    2. In an attempt to preserve the interpretation of DHW values when predicting bleaching in the Version 2 5km product suite, CRW faithfully recreated the Maximum Monthly Mean (MMM)-climatology and HotSpot/DHW methodologies of the heritage operational 50km products in such a way as to make the two product suites as similar as possible. Major differences between the Version 2 5km and 50km products lay in their different resolutions and in the methodologies used to create individual pixel SSTs. These differences changed the interpretation of the 5km product suite for some regions when detecting coral bleaching heat stress.

The Version 2 daily global 5km coral bleaching heat stress monitoring product suite provided service at or near reef-scales, allowing direct monitoring of 95% of global coral reefs and significantly reducing data gaps caused by cloud cover.

SST variability is often considerably higher at the much finer 5km spatial and daily temporal resolutions, when compared with CRW's 50km twice-weekly SST. Due to resulting day-to-day fluctuations between stress levels in highly-variable locations, the Version 2 single-day 5km Bleaching Alert Area product did 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 Version 2 single-day 5km Bleaching Alert Area product over several days, a 7-day maximum Bleaching Alert Area composite product, updated daily, was introduced. This 7-day composite product showed the maximum stress level that a pixel has experienced during the most recent seven (7) consecutive days. Data and images were dated on the last day of the 7-day period. Additionally, the 5km 7-day maximum Bleaching Alert Area composite product was compatible with CRW's operational 50km twice-weekly Bleaching Alert Area product. (The 50km Bleaching Alert Area product is actually based on a half-week (3 or 4 days) composite of 50km SSTs, but with much less SST variability due to its much coarser spatial resolution.)

In May 2015, CRW released a Version 2 5km 7-day SST Trend product, updated daily. The 5km SST Trend provided information on the pace and direction of the SST variation, and thus coral bleaching heat stress, if present, over the past seven days. Seven daily global SSTs were included in the calculation. Pixels colored in green had insignificant trends, due either to small SST trends (within the range -0.2 to 0.2 °C) or trends that failed the two-tailed Student's-t test for the 20% significance level with five degrees of freedom.

Note that all other Version 2 products were single-day products, updated daily. Images were 1-2 days behind the current date, however, as data were processed in the early afternoon, U.S. Eastern Time using data from the previous day. For example, data processed on a Wednesday afternoon included all observations made on Tuesday (independent of time zone) and carried Tuesday's date.


For additional technical details about the 5km product suite, see Liu et al. 2014.


Development of the next-generation 5km product suite was accomplished through a collaboration of NOAA Coral Reef Watch, the University of South Florida, NASA-Ames, the UNEP World Conservation Monitoring Centre, and the Cooperative Institute for Research in Environmental Science, with funding support from the NASA Biodiversity and Ecological Forecasting program, the NOAA Coral Reef Conservation Program, and the NOAA/NESDIS Ocean Remote Sensing Program. The 5km product suite, which was featured in the NASA Applied Sciences Program's 2013 Annual Report, will undergo continuous improvements.

CRW will continue to produce the current operational 50km product suite until the 5km product suite becomes operational. As noted above, there continue to be some differences between the two product suites in certain areas of the globe, and user discretion is advised. We expect that the 5km product suite will be more accurate due to the improved data quality, density, spatial and temporal resolutions, and climatology.

 



 

III. Version 3 Product Suite

CRW's most recent version of the 5 km product suite is Version 3, released on May 4, 2017. Its detailed product description is available on its home page.