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General Information

File Identifier:	CRW_marine_heatwave
Metadata Language:	eng; USA
Metadata Date Stamp:	2025-03
Organization:	NOAA Coral Reef Watch program
Organization Role:	pointOfContact

Identification Information

Title:	NOAA Coral Reef Watch Marine Heatwave Watch
Dataset Language:	eng; USA
Abstract:	Marine Heatwaves are prolonged periods of anomalously high sea surface temperature (SST). In effect, they are categorized anomalies of SST compared with a long-term, high, daily SST threshold. The daily global 5km-resolution Marine Heatwave Watch (MHW) product presented here is a generalized version of the NOAA Coral Reef Watch (CRW) daily global 5km satellite Coral Bleaching HotSpot product. It isn't aimed specifically at corals and the warm season for each coral reef worldwide, but instead provides a general description of oceanic heat stress that can occur at any time of year, at any given location, and is likely applicable to and impacting a broader range of marine life. The MHW product is derived by applying the Marine Heatwave algorithm of Hobday et al. (2018) to the CRW daily global 5km CoralTemp satellite SST data product. It has near real-time and historic components and spans 1985 to the present.

Browse Graphic

Browse Graphic URL:	https://coralreefwatch.noaa.gov/data_current/marine_heatwave/v1.0.1/daily/png/noaa-crw_mhw_v1.0.1_category_global_current.png
Browse Graphic Caption:	The daily global 5km-resolution Marine Heatwave Watch (MHW) product presented here is a generalized version of the NOAA Coral Reef Watch (CRW) daily global 5km satellite Coral Bleaching HotSpot product.
Browse Graphic Type:	png

Data Theme

Theme Topics:

Oceans and Estuaries

Spatial Domain

West Bounding Longitude:	-180.0
South Bounding Latitude:	-90.0
East Bounding Longitude:	180.0
North Bounding Latitude:	90.0

Data Quality Information

Scope (quality information applies to):

aggregate

Data History:

Calculation of Heatwave Category For each day from January 1, 1985 to the present, we calculated the Marine Heatwave category for each 5km satellite pixel grid in the v3.1 daily global CoralTemp SST dataset. We identified a Marine Heatwave if the SST for a particular day was greater than the 90th percentile value for that location. Once a Marine Heatwave was identified, it was categorized based on its intensity, after Hobday et al. (2018)1. Intensity categories were defined based on the difference between the average and 90th percentile values for each 5km pixel (diff). If the SST for a particular day was ≥ (average + diff) and < (average + 2diff), it was categorized as being Marine Heatwave Category 1. If the SST for a particular day was ≥ (average + 2diff) and < (average + 3diff), it was categorized as being Marine Heatwave Category 2; and so on.Since the climatology does not have a value for February 29 in each leap year, when this value was needed, both the average and 90th percentile SST values were calculated using an average of the SST values from February 28 and March 1. Dealing with Sea Ice Due to the methodology used to derive the MHW product, its interpretation becomes problematic if all pixels are not approximately normally distributed. At the very least, if the methodology is applied to a pixel with non-normally distributed temperatures (e.g., a pixel with any sea ice) and then applied to a pixel with approximately normally distributed temperatures (e.g., a pixel with only water temperatures), then the interpretation of each of these pixels will be different, creating internal inconsistencies. For this reason, if sea ice was present in a 5km satellite grid location within the 11-day window surrounding any date in the 28-year climatology period, then the pixel was classified as ice and given a flag value of 1 in the mask array of the climatology. The sea ice mask in the MHW product is static and is a conservative estimate of the ice-free satellite pixels within the climatology. It is not an indication of sea ice for that pixel for a given day.

Contact Information

Organization:	NOAA Coral Reef Watch program
Address:	NOAA/NESDIS/STAR Coral Reef Watch, NCWCP, E/RA3, Room 3222, 5830 University Research Court
City:	College Park
State:	Maryland
Postal Code:	20740
Country:	USA
Email:	coralreefwatch@noaa.gov
Telephone:	301-683-3320
Fax:	301-683-3301

Distribution Information

Format Name:	netCDF
Distribution Link:	https://coralreefwatch.noaa.gov/product/marine_heatwave/
Distribution Link Function:	Download

Metadata Reference Information

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