scientists from the Marine Applications Science Team (MAST) in the Oceanic
Research and Applications Division (ORAD) of the Office of Research and
Applications (ORA) and from the Product Systems Branch (PSB) of the Information
Processing Division (IPS) of the Office of Satellite Data Processing and Distribution
(OSDPD).
3. The Coral Reef Watch SST Anomaly Product
CRW’s first product consisted of a simple SST anomaly based on a nighttime
AVHRR climatology data set from 1985 to 1993. The climatology was derived by
averaging weekly mean nighttime SSTs into monthly means over the nine year period,
and then producing the 12 monthly means from all nine years of data. The actual daily
SST anomaly was derived after the monthly means had been interpolated into daily
means. This product supports wide ranging uses and is the preferred product for the
NESDIS’ National Climate Data Center (NCDC) when observing the onset and effects
of El Nino and La Nina (http://www.ncdc.noaa.gov/oa/climate/elnino/elnino.html).
The SST Anomaly product became officially operational in 2001 (see Figure 2 for an
example of the SST Anomaly product).
4. The Coral Reef Watch Bleaching HotSpot Product
Early in 1997, NESDIS began developing global satellite 50-km resolution
experimental products (initially SST Bleaching HotSpots, and then DHW products) as
indices of thermal stress-related coral bleaching. These products are the outgrowth of
earlier work by Montgomery and Strong (1994) and Gleeson and Strong (1995). The
HotSpot product became officially operational in 2001 (see Figure 3 for an example of
the HotSpot product).
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
climatology, often referred to as the MMM climatology). Since the HotSpot is an
anomaly based on the maximum of the monthly mean SST, negative values are
meaningless in this context; therefore only positive values are displayed.
5. The Coral Reef Watch DHW Product
HotSpot values provide a measure of the intensity of sea surface thermal stress, but
do not measure the cumulative effects of that thermal stress on a biological system such
as a coral reef. In order to monitor this cumulative effect, a thermal stress index, the
Degree Heating Week (DHW), was developed. DHW represents the accumulation of
HotSpots for a given location over a rolling 12-week time period. Preliminary results
indicate that a HotSpot value of less than one degree is insufficient to cause visible
stress on corals. Consequently, only HotSpot values 1°C are accumulated (i.e. if we
have consecutive HotSpot values of 1.0, 2.0, 0.8 and 1.2, the DHW value will be 4.2
because 0.8 is less than one and therefore not used). One DHW is equivalent to one
week of HotSpot levels staying at 1°C or one ½ week of HotSpot levels at 2°C, and so
forth. For an example of the DHW product, see Figure 4.
14
Skirving, Strong, Liu, Arzayus, Liu and Sapper
Research and Applications Division (ORAD) of the Office of Research and
Applications (ORA) and from the Product Systems Branch (PSB) of the Information
Processing Division (IPS) of the Office of Satellite Data Processing and Distribution
(OSDPD).
3. The Coral Reef Watch SST Anomaly Product
CRW’s first product consisted of a simple SST anomaly based on a nighttime
AVHRR climatology data set from 1985 to 1993. The climatology was derived by
averaging weekly mean nighttime SSTs into monthly means over the nine year period,
and then producing the 12 monthly means from all nine years of data. The actual daily
SST anomaly was derived after the monthly means had been interpolated into daily
means. This product supports wide ranging uses and is the preferred product for the
NESDIS’ National Climate Data Center (NCDC) when observing the onset and effects
of El Nino and La Nina (http://www.ncdc.noaa.gov/oa/climate/elnino/elnino.html).
The SST Anomaly product became officially operational in 2001 (see Figure 2 for an
example of the SST Anomaly product).
4. The Coral Reef Watch Bleaching HotSpot Product
Early in 1997, NESDIS began developing global satellite 50-km resolution
experimental products (initially SST Bleaching HotSpots, and then DHW products) as
indices of thermal stress-related coral bleaching. These products are the outgrowth of
earlier work by Montgomery and Strong (1994) and Gleeson and Strong (1995). The
HotSpot product became officially operational in 2001 (see Figure 3 for an example of
the HotSpot product).
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
climatology, often referred to as the MMM climatology). Since the HotSpot is an
anomaly based on the maximum of the monthly mean SST, negative values are
meaningless in this context; therefore only positive values are displayed.
5. The Coral Reef Watch DHW Product
HotSpot values provide a measure of the intensity of sea surface thermal stress, but
do not measure the cumulative effects of that thermal stress on a biological system such
as a coral reef. In order to monitor this cumulative effect, a thermal stress index, the
Degree Heating Week (DHW), was developed. DHW represents the accumulation of
HotSpots for a given location over a rolling 12-week time period. Preliminary results
indicate that a HotSpot value of less than one degree is insufficient to cause visible
stress on corals. Consequently, only HotSpot values 1°C are accumulated (i.e. if we
have consecutive HotSpot values of 1.0, 2.0, 0.8 and 1.2, the DHW value will be 4.2
because 0.8 is less than one and therefore not used). One DHW is equivalent to one
week of HotSpot levels staying at 1°C or one ½ week of HotSpot levels at 2°C, and so
forth. For an example of the DHW product, see Figure 4.
14
Skirving, Strong, Liu, Arzayus, Liu and Sapper