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K.S. Casey et al.
T 4 − T 5 brightness temperature difference is less than 0.7 ◦ C. To avoid discontinuities, in cases where the T 4 − T 5 brightness temperature difference was between
0.5 and 0.9 ◦ C the SST was calculated using a weighted combination of SST values determined using both sets of coefficients. Pathfinder Version 3 data were first
released to the public in 1997 and spanned only 1991–1994. They were quickly
superseded by Pathfinder Version 4, which was released only a short time later.
16.3.4 Version 4
In Version 4, a more robust algorithm coefficient scheme was introduced, and decision trees were implemented to better eliminate cloud-contaminated pixels. Quality
levels were expanded to 0–7 to allow for greater user flexibility in determining tradeoffs between data coverage and data quality. Version 4 data became available in 1997
and eventually covered 1985–2003. The Version 4 data marked the culmination of
the NOAA/NASA AVHRR Oceans Pathfinder period.
16.4 Current State of Pathfinder SST: Version 5
Beginning in 2002, the Pathfinder SST Program entered a new phase targeted at producing an even more accurate, consistent, and finer resolution SST data set. By this
time, the term “Climate Data Record” had emerged and the Pathfinder SST Program
renewed its efforts toward delivering the SST climate data record. Improvements in
spatial resolution, the land mask, and the way sea ice information was used in the
quality level determinations were implemented. The 1 ◦ resolution OISSTv1 firstguess and reference SST field used in earlier Pathfinder versions was replaced with
a newer version of the product, the OISSTv2 (Reynolds et al., 2002). For the earliest
part of the AVHRR record from late 1981 to 1984, a new 25 km Daily Optimally
Interpolated SST (DOISST, Reynolds et al., 2007) was used. A more quantitative
analysis of the improvements achieved along with a description and evaluation of
new SST climatologies derived from Pathfinder Version 5 is available in Casey
et al. (2010).
By 2009, production, distribution, and long-term stewardship of the Pathfinder
Version 5 SST data had become a joint University of Miami and NODC effort.
The University of Miami processed the data from L0/L1b to L3, including a transformation from the integerized sinusoidal grid to the regularly gridded data in
HDF4-Scientific Data Set format. These data were then transferred to NODC, where
they were subjected to additional quality assurance involving browse image generation, visual inspection of every image, and comparison against the HadSST2
(Rayner et al., 2006) in-situ dataset. Any problems identified were then analyzed,
and corrections implemented at the University of Miami where the data were regenerated before re-inspection at NODC. Once cleared through the quality assurance
steps, the data were then archived at NODC and provided to users through its http,
ftp, and OPeNDAP services. Access to the entire Pathfinder Version 5 collection
K.S. Casey et al.
T 4 − T 5 brightness temperature difference is less than 0.7 ◦ C. To avoid discontinuities, in cases where the T 4 − T 5 brightness temperature difference was between
0.5 and 0.9 ◦ C the SST was calculated using a weighted combination of SST values determined using both sets of coefficients. Pathfinder Version 3 data were first
released to the public in 1997 and spanned only 1991–1994. They were quickly
superseded by Pathfinder Version 4, which was released only a short time later.
16.3.4 Version 4
In Version 4, a more robust algorithm coefficient scheme was introduced, and decision trees were implemented to better eliminate cloud-contaminated pixels. Quality
levels were expanded to 0–7 to allow for greater user flexibility in determining tradeoffs between data coverage and data quality. Version 4 data became available in 1997
and eventually covered 1985–2003. The Version 4 data marked the culmination of
the NOAA/NASA AVHRR Oceans Pathfinder period.
16.4 Current State of Pathfinder SST: Version 5
Beginning in 2002, the Pathfinder SST Program entered a new phase targeted at producing an even more accurate, consistent, and finer resolution SST data set. By this
time, the term “Climate Data Record” had emerged and the Pathfinder SST Program
renewed its efforts toward delivering the SST climate data record. Improvements in
spatial resolution, the land mask, and the way sea ice information was used in the
quality level determinations were implemented. The 1 ◦ resolution OISSTv1 firstguess and reference SST field used in earlier Pathfinder versions was replaced with
a newer version of the product, the OISSTv2 (Reynolds et al., 2002). For the earliest
part of the AVHRR record from late 1981 to 1984, a new 25 km Daily Optimally
Interpolated SST (DOISST, Reynolds et al., 2007) was used. A more quantitative
analysis of the improvements achieved along with a description and evaluation of
new SST climatologies derived from Pathfinder Version 5 is available in Casey
et al. (2010).
By 2009, production, distribution, and long-term stewardship of the Pathfinder
Version 5 SST data had become a joint University of Miami and NODC effort.
The University of Miami processed the data from L0/L1b to L3, including a transformation from the integerized sinusoidal grid to the regularly gridded data in
HDF4-Scientific Data Set format. These data were then transferred to NODC, where
they were subjected to additional quality assurance involving browse image generation, visual inspection of every image, and comparison against the HadSST2
(Rayner et al., 2006) in-situ dataset. Any problems identified were then analyzed,
and corrections implemented at the University of Miami where the data were regenerated before re-inspection at NODC. Once cleared through the quality assurance
steps, the data were then archived at NODC and provided to users through its http,
ftp, and OPeNDAP services. Access to the entire Pathfinder Version 5 collection