The 4 km Pathfinder effort at the National Oceanic and Atmospheric Administration (NOAA) National Oceanographic Data Center (NODC) and the University of Miami's Rosenstiel School of Marine and Atmospheric Science (RSMAS) is an extension of and improvement on the sea surface temperature (SST) fields from the NOAA/NASA AVHRR Oceans 9km Pathfinder dataset. In this 4 km Pathfinder project, some important shortcomings in the original 9 km data have been corrected, and the entire time series has been reprocessed at the 4 km Global Area Coverage (GAC) level, the highest resolution possible globally. Twice-daily SST and related parameters back to 1981 have been produced, as well as temporal averages for 5-day, 7-day, 8-day, monthly, and yearly periods. This information is archived at the National Oceanographic Data Center (http://www.nodc.noaa.gov). This metadata record describes the temporally averaged SST data and related parameters available for 1981-2009. Data for all years and time periods are available as separate NODC accessions. These data were collected through the operational periods of the NOAA-7 through NOAA-18 Polar Operational Environmental Satellite (POES).
To provide sea surface temperature data and related parameters with good temporal consistency, high accuracy and spatial resolution, and for archive and distribution through the NOAA National Oceanographic Data Center (NODC). This SST data collecton is intended primarily for climate related applications and studies and is being established to help form the basis for a Climate Data Record for SST.
Originally, the Version 5.0 Pathfinder algorithm was used to produce these twice-daily, 5-day, 7-day, 8-day, monthly, and yearly global SST and related parameters (described below). This algorithm is an improved version of the previously most successful of many methods used to derive SST from AVHRR observations (see Barton (1995) for a review of earlier techniques), the University of Miami Pathfinder version v4.2 SST algorithm (described fully in Kilpatrick et al., 2001). The v4.2 algorithm offered marked improvement over operational retrieval algorithms such as MCSST and was applied to AVHRR data to maximize accuracy and to minimize artificial fluctuations arising from the sequence of AVHRR instruments flown on NOAA's polar-orbiting satellites during the past 2 decades. The 9 km v4.2 Pathfinder SSTs have already been shown to be the highest quality product currently available for the construction of global climatologies (Casey and Cornillon, 1999) and longer-term SST trend determination (Casey and Cornillon, 2001), and have been demonstrated to be accurate within about 0.3 degrees C under optimal conditions (Kearns et al., 2000). Relative to the older 9 km v4.2 Pathfinder data, the new, ~4 km resolution Pathfinder Version 5.0 global SSTs increase detail roughly by a factor of four simply by virtue of the increased resolution. The increase in detail over widely used but relatively coarse SST datasets such as Optimally Interpolated SST Version 2 (OISSTv2; Reynolds et al., 2002) and the Hadley Centre's Global Sea Ice and SST (HadISST1; Rayner et al., 2003) is far greater. In addition to the increased resolution, significant improvements have been made in the Version 5.0 which enhance the usefulness of the SST fields. Currently, these enhancements include the use of sea ice in the quality level determination scheme, inclusion of many inland water bodies, and the use of a greatly improved land mask. The greatest improvements are seen in coastal zones, marginal seas, and boundary current regions where SST gradients are often large and their impact on operational or research products is greatest. Separate SST products for daytime and nighttime AVHRR retrievals are made to better understand the differences in skin and bulk temperatures, since mean differences between AVHRR-measured skin temperatures and bulk temperatures of 0.1 to 0.2 degrees C (Schluessel et al., 1990) and locally varying differences of up to 1.8 degrees C (Minnett et al., 2000) have been observed. In addition to SST values, the Pathfinder V5.0 Project makes six other parameters available, for a total of seven per time step: 1. All-pixel SST - The all-pixel SST files contain values for each pixel location, including those contaminated with clouds or other sources of error. The Overall Quality Flag values may be used to filter out these unwanted values. The SST value in each pixel location is an average of the highest quality AVHRR Global Area Coverage (GAC) observations available in each roughly 4 km bin. 2. First-guess SST - The Pathfinder algorithm uses a first guess SST provided by the Reynolds Optimally Interpolated SST Version 2 (OISSTv2) product. The OISSTv2 is also used in the quality control procedures. For Version 5.1 data (1981-1985), the Reynolds Optimum Interpolation1/4-degree Daily SST Analysis Version 2 (DOISSTv2) was used in place of the OISSTv2. 3. Number of observations - This parameter indicates the number of AVHRR GAC observations falling in each approximately 4 km bin. 4. Standard deviation - This is the standard deviation of the observations in each 4 km bin. 5. Overall quality flag - The overall quality flag is a relative assignment of SST quality based on a hierarchical suite of tests. The Quality Flag varies from 0 to 7, with 0 being the lowest quality and 7 the highest. For more information regarding the suite of tests, see the Kilpatrick et al. (2001) paper cited above. 6. Mask 1 - These files contain a mask code, which along with Mask 2, can be used to determine the tests in the hierarchical suite that were passed or failed, resulting in the Overall Quality Flag. 7. Mask 2 - These files contain a mask code, which along with Mask 1, can be used to determine the tests in the hierarchical suite that were passed or failed, resulting in the Overall Quality Flag. The interim SST data (2007-2009) described in this metadata record were produced prior to the derivation of a final set of monthly coefficients for those years. The SST values were therefore calculated using the most recent set of coefficients available, and are considered Interim Pathfinder Version 5.0 data and not part of the Formal Pathfinder Version 5.0 data set. The algorithm used to create Version 5.1 data (1981-1985) is different only in that it replaces the Reynolds Weekly Optimally Interpolated SST Version 2 (OISSTv2) with the Reynolds Optimum Interpolation 1/4-degree Daily SST Analysis Version 2 (DOISSTv2) as the first guess SST and in the quality control procedures. The primary effect of this change is to retain more data in the high gradient regions and in regions where meandering or feature advection is present; effect on the retrieved SST is minimal. Note on Pathfinder Program: The Pathfinder program was jointly created by NASA and NOAA through the Earth Observing System (EOS) Program Office in 1990. The focus of the Pathfinder Program was to determine how existing satellite based data sets could be processed and used to study global change. The data sets were designed to be long time-series data processed with stable calibration and community consensus algorithms to better assist the research community. For more information, see: National Aeronautics and Space Administration (NASA). 1993. Earth Observing System (EOS) Reference Handbook, ed. G. Asrar and D. J. Dokken. Washington, D. C.: National Aeronautics and Space Administration, Earth Science Support Office, Document Resource Facility. The 4 km Pathfinder Project effort at the National Oceanic and Atmospheric Administration (NOAA) National Oceanographic Data Center (NODC) and the University of Miami's Rosenstiel School of Marine and Atmospheric Science (RSMAS) is an extension of and improvement on the sea surface temperature (SST) fields from that original NOAA/NASA AVHRR Oceans Pathfinder program. Resource Description: These data are archived at the National Oceanographic Data Center and may be referenced by an assigned seven-digit accession number. Accession numbers and additional data details may be viewed utilizing the NODC Ocean Archive System at https://data.noaa.gov/onestop/ and searching by title under Pathfinder and other desired parameters.
publication date
Please acknowledge the use of these data with: The Pathfinder Version 5 and 5.1 SST Data were provided by the NOAA National Oceanographic Data Center at URL: http://pathfinder.nodc.noaa.gov
SSMC3, 4th Floor, E/OC11315 East-West Highway
Phone/FAX/E-mail/letter during business hours
https://data.nodc.noaa.gov/pathfinder/Version5.0/browse_images/Daily/2006/SST/2006001.s04d1pfv50-sst.hdf.jpg
https://data.nodc.noaa.gov/pathfinder/Version5.1/browse_images/Daily/1985/SST/1985001.s04d1pfv51-sst.hdf.jpg
https://data.nodc.noaa.gov/pathfinder/Version5.0_interim/browse_images/Daily/2009/NOAA18/SST/2009001.s04d1pfrt-sst.hdf.jpg
Kenneth S. Casey, National Oceanographic Data Center (NODC), and Edward J. Kearns, Vicki Halliwell, and Robert Evans, University of Miami, Rosenstiel School of Marine and Atmospheric Science (RSMAS)
See qual, mask1, and mask2; stdv and num files (quality flag and statistical fields for 4 km AVHRR Pathfinder available data) available online from the NODC Satellite Oceanography Group at: http://www.nodc.noaa.gov/sog/pathfinder4km/available.html
Files are run against the program (algorithm) MD5 to verify data integrity which generates a code, called an MD5 checksum. After files are transferred from one place to another, the program can be run on the file again and a new code generated. The old MD5 checksum code should be identical to the new MD5 checksum code. If not, the file was somehow corrupted during transfer (see original MD5 documentation at http://www.isi.edu/in-notes/rfc1321.txt)
The SST data are nearly complete in the sense that a value is available for nearly every pixel, with the exception of some areas and times where some of the input low-level AVHRR data were missing from the archive. However, after application of the quality flag parameters, the SST fields have extensive gaps due to clouds and other factors which limit the quality of the observed SST. The .HDF files are 16-bit files, and pixel values can range from 0 to 65535 (2 to the 16th power). However, realistic pixel values for SST will always be less than 600 or so. 'Land' has a value of 1. SST in degC = 0.075 x pixel value - 3. Temperatures are represented in 0.075 degC increments.Additional notes: These data were collected through the operational periods of the NOAA-7 through NOAA-18 Polar Operational Environmental Satellite (POES). Detailed information on the POES satellites is available at the NOAA Office of Satellite Operations website at URL: http://www.oso.noaa.gov/poes/index.htm. A table listing which satellites were used in the generation of Pathfinder V5.0 data for specific dates is available online at: http://www.nodc.noaa.gov/sog/pathfinder4km/userguide.html
The major sources of error in geo-locating AVHRR data are (a) drift in the spacecraft clock (which causes errors in the estimated along-track position), and (b) uncertainty errors in spacecraft and sensor attitude. (a) Clock Correction: To minimize error in the along track position estimated by the orbital model, a satellite clock correction factor is applied to the time code imbedded in each piece. The method used to determine these clock correction factors is presented below. The clock aboard a given satellite drifts continually at a relatively constant rate (e.g., for NOAA-14, ~9msday-1) compared to the reference clock on Earth. Because of this drift, the NOAA/NESDIS Satellite Operation Control Center periodically sends a command to the satellite to reset the on-board clock to a new baseline thereby eliminating the accumulation of a large time offset error between the Earth and satellite clocks.To correct for clock drift between these resets, correction factors were determined from a database of satellite clock time and Earth time offsets collected at the RSMAS High Resolution Picture Transmission (HRPT) receiving station. During HRPT transmission, both the satellite clock (used to create the embedded time code in each piece) and the Earth clock are simultaneously available. The clock correction bias was determined by (1) visual examination of the Earth/satellite clock differences collected in the database to locate the precise magnitude and timing of clock resets performed by the Satellite Operation Control Center and (2) recorded time differences between the identified reset periods were then filtered to remove spurious noise, and regressed against the corresponding satellite time to determine the clock drift correction. These drift corrections were then applied to all data time-stamped during a given reset period. Refer to Sea Surface Temperature Global Area Coverage (GAC) Processing Appendix A: Calibration and Navigation Correction Factors for a list of clock offsets for each NOAA spacecraft (http://www.rsmas.miami.edu/groups/rrsl/pathfinder/Processing/proc_app_a.html).(b) Attitude Corrections - After clock correction, a nominal attitude correction is then applied to minimize the uncertainty in regard to the direction in which the spacecraft is pointing. The nominal attitude correction applied was determined by averaging the absolute attitude of the spacecraft over many geographic locations and times along the orbital track. The method used to determine the absolute attitude of the spacecraft involves matching a digital coastal outline to a given image and recording the amount of pitch, yaw, and roll required to make the outline and land coincide. This method has the advantage that it can be performed over small geographical distances and is similar to other techniques which rely on widely separated geographical control points to anchor the navigation. The resultant navigation information, output by the SECTOR procedure for each piece, provides the mapping parameters needed to convert between the satellite perspective of pixel and scan line, and Earth-based latitude and longitude coordinates. Refer to Sea Surface Temperature Global Area Coverage (GAC) Processing Appendix A: Calibration and Navigation Correction Factors for attitude correction factors for each NOAA spacecraft (http://www.rsmas.miami.edu/groups/rrsl/pathfinder/Processing/proc_app_a.html).
Refer to the Horizontal Positional Accuracy Report in this metadata record for a discussion of sources of error in geo-locating AVHRR data.
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 1985 (NODC Accession Number 0001763)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 1986 (NODC Accession Number 0001764)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 1987 (NODC Accession Number 0001765)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 1988 (NODC Accession Number 0001766)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 1989 (NODC Accession Number 0001767)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 1990 (NODC Accession Number 0001768)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 1991 (NODC Accession Number 0001769)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 1992 (NODC Accession Number 0001770)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 1993 (NODC Accession Number 0001771)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 1994 (NODC Accession Number 0001772)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 1995 (NODC Accession Number 0001773)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 1996 (NODC Accession Number 0001774)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 1997 (NODC Accession Number 0001775)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 1998 (NODC Accession Number 0001776)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 1999 (NODC Accession Number 0001777)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 2000 (NODC Accession Number 0001778)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 2001 (NODC Accession Number 0001779)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 1985 (NODC Accession Number 0001780)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 1986 (NODC Accession Number 0001781)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 1987 (NODC Accession Number 0001782)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 1988 (NODC Accession Number 0001783)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 1989 (NODC Accession Number 0001784)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 1990 (NODC Accession Number 0001785)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 1991 (NODC Accession Number 0001786)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 1992 (NODC Accession Number 0001787)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 1993 (NODC Accession Number 0001788)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 1994 (NODC Accession Number 0001789)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 1995 (NODC Accession Number 0001790)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 1996 (NODC Accession Number 0001791)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 1997 (NODC Accession Number 0001792)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 1998 (NODC Accession Number 0001793)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 1999 (NODC Accession Number 0001794)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 2000 (NODC Accession Number 0001795)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 2001 (NODC Accession Number 0001796)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 1985 (NODC Accession Number 0001797)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 1986 (NODC Accession Number 0001798)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 1987 (NODC Accession Number 0001799)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 1988 (NODC Accession Number 0001800)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 1989 (NODC Accession Number 0001801)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 1990 (NODC Accession Number 0001802)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 1991 (NODC Accession Number 0001803)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 1992 (NODC Accession Number 0001804)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 1993 (NODC Accession Number 0001805)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 1994 (NODC Accession Number 0001806)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 1995 (NODC Accession Number 0001807)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 1996 (NODC Accession Number 0001808)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 1997 (NODC Accession Number 0001809)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 1998 (NODC Accession Number 0001810)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 1999 (NODC Accession Number 0001811)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 2000 (NODC Accession Number 0001812)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 2001 (NODC Accession Number 0001813)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 1985 (NODC Accession Number 0001814)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 1986 (NODC Accession Number 0001815)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 1987 (NODC Accession Number 0001816)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 1988 (NODC Accession Number 0001817)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 1989 (NODC Accession Number 0001818)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 1990 (NODC Accession Number 0001819)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 1991 (NODC Accession Number 0001820)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 1992 (NODC Accession Number 0001821)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 1993 (NODC Accession Number 0001822)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 1994 (NODC Accession Number 0001823)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 1995 (NODC Accession Number 0001824)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 1996 (NODC Accession Number 0001825)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 1997 (NODC Accession Number 0001826)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 1998 (NODC Accession Number 0001827)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 1999 (NODC Accession Number 0001828)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 2000 (NODC Accession Number 0001829)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 2001 (NODC Accession Number 0001830)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 1985 (NODC Accession Number 0001831)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 1986 (NODC Accession Number 0001832)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 1987 (NODC Accession Number 0001833)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 1988 (NODC Accession Number 0001834)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 1989 (NODC Accession Number 0001835)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 1990 (NODC Accession Number 0001836)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 1991 (NODC Accession Number 0001837)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 1992 (NODC Accession Number 0001838)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 1993 (NODC Accession Number 0001839)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 1994 (NODC Accession Number 0001840)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 1995 (NODC Accession Number 0001841)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 1996 (NODC Accession Number 0001842)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 1997 (NODC Accession Number 0001843)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 1998 (NODC Accession Number 0001844)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 1999 (NODC Accession Number 0001845)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 2000 (NODC Accession Number 0001846)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 2001 (NODC Accession Number 0001847)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 1985 (NODC Accession Number 0001848)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 1986 (NODC Accession Number 0001849)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 1987 (NODC Accession Number 0001850)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 1988 (NODC Accession Number 0001851)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 1989 (NODC Accession Number 0001852)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 1990 (NODC Accession Number 0001853)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 1991 (NODC Accession Number 0001854)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 1992 (NODC Accession Number 0001855)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 1993 (NODC Accession Number 0001856)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 1994 (NODC Accession Number 0001857)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 1995 (NODC Accession Number 0001858)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 1996 (NODC Accession Number 0001859)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 1997 (NODC Accession Number 0001860)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 1998 (NODC Accession Number 0001861)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 1999 (NODC Accession Number 0001862)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 2000 (NODC Accession Number 0001863)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 2001 (NODC Accession 0001864)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 2002 (NODC Accession Number 0043730)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 2002 (NODC Accession Number 0043731)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 2002 (NODC Accession Number 0043732)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 2002 (NODC Accession Number 0043733)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 2002 (NODC Accession Number 0043734)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 2002 (NODC Accession Number 0043735)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 2003 (NODC Accession Number 0043736)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 2003 (NODC Accesssion Number 0043737)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 2003 (NODC Accession Number 0043738)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 2003 (NODC Accession Number 0043739)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 2003 (NODC Accession Number 0043740)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 2003 (NODC Accession Number 0043741)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 2004 (NODC Accession Number 0043742)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 2004 (NODC Accession Number 0043743)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 2004 (NODC Accession Number 0043744)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 2004 (NODC Accession Number 0043745)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 2004 (NODC Accession Number 0043746)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 2004 (NODC Accession Number 0043747)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 2005 (NODC Accession Number 0043748)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 2005 (NODC Accession Number 0043749)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 2005 (NODC Accession Number 0043750)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 2005 (NODC Accession Number 0043751)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 2005 (NODC Accession Number 0043752)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Daily Data for 2006 (NODC Accession Number 0043753)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Data for 2006 (NODC Accession Number 0043754)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Monthly Data for 2006 (NODC Accession Number 0043755)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 5-day Data for 2006 (NODC Accession Number 0043756)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 7-day Data for 2006 (NODC Accession Number 0043757)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 8-day Data for 2006 (NODC Accession Number 0043758)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Interim Data for 2002 (NODC Accession Number 0045493)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Interim Data for 2003 (NODC Accession Number 0045494)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Interim Data for 2004 (NODC Accession Number 0045495)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Interim Data for 2005 (NODC Accession Number 0045496)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Interim Data for 2006 (NODC Accession Number 0045497)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Interim Data for 2007 (NODC Accession Number 0045498)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Interim Data for 2008 (NODC Accession Number 0054496)
4 km NODC/RSMAS AVHRR Pathfinder v5.0 Interim Data for 2009 (NODC Accession Number 0062474)
4km NODC/RSMAS AVHRR Pathfinder v5.1 Daily Data for 1981 (NODC Accession Number 0051818)
4km NODC/RSMAS AVHRR Pathfinder v5.1 Monthly Data for 1981 (NODC Accession Number 0051819)
4km NODC/RSMAS AVHRR Pathfinder v5.1 5-day Data for 1981 (NODC Accession Number 0051820)
4km NODC/RSMAS AVHRR Pathfinder v5.1 7-day Data for 1981 (NODC Accession Number 0051821)
4km NODC/RSMAS AVHRR Pathfinder v5.1 8-day Data for 1981 (NODC Accession Number 0051822)
4km NODC/RSMAS AVHRR Pathfinder v5.1 Daily Data for 1982 (NODC Accession Number 0051823)
4km NODC/RSMAS AVHRR Pathfinder v5.1 Data for 1982 (NODC Accession Number 0051824)
4km NODC/RSMAS AVHRR Pathfinder v5.1 Monthly Data for 1982 (NODC Accession Number 0051825)
4km NODC/RSMAS AVHRR Pathfinder v5.1 5-day Data for 1982 (NODC Accession Number 0051826)
4km NODC/RSMAS AVHRR Pathfinder v5.1 7-day Data for 1982 (NODC Accession Number 0051827)
4km NODC/RSMAS AVHRR Pathfinder v5.1 8-day Data for 1982 (NODC Accession Number 0051828)
4km NODC/RSMAS AVHRR Pathfinder v5.1 Daily Data for 1983 (NODC Accession Number 0051829)
4km NODC/RSMAS AVHRR Pathfinder v5.1 Data for 1983 (NODC Accession Number 0051830)
4km NODC/RSMAS AVHRR Pathfinder v5.1 Monthly Data for 1983 (NODC Accession Number 0051831)
4km NODC/RSMAS AVHRR Pathfinder v5.1 5-day Data for 1983 (NODC Accession Number 0051832)
4km NODC/RSMAS AVHRR Pathfinder v5.1 7-day Data for 1983 (NODC Accession Number 0051833)
4km NODC/RSMAS AVHRR Pathfinder v5.1 8-day Data for 1983 (NODC Accession Number 0051834)
4km NODC/RSMAS AVHRR Pathfinder v5.1 Daily Data for 1984 (NODC Accession Number 0051835)
4km NODC/RSMAS AVHRR Pathfinder v5.1 Data for 1984 (NODC Accession Number 0051836)
4km NODC/RSMAS AVHRR Pathfinder v5.1 Monthly Data for 1984 (NODC Accession Number 0051837)
4km NODC/RSMAS AVHRR Pathfinder v5.1 5-day Data for 1984 (NODC Accession Number 0051838)
4km NODC/RSMAS AVHRR Pathfinder v5.1 7-day Data for 1984 (NODC Accession Number 0051839)
4km NODC/RSMAS AVHRR Pathfinder v5.1 8-day Data for 1984 (NODC Accession Number 0051840)
4km NODC/RSMAS AVHRR Pathfinder v5.1 Daily Data for 1985 (NODC Accession Number 0051841)
4km NODC/RSMAS AVHRR Pathfinder v5.1 Monthly Data for 1985 (NODC Accession Number 0051842)
4km NODC/RSMAS AVHRR Pathfinder v5.1 5-day Data for 1985 (NODC Accession Number 0051843)
4km NODC/RSMAS AVHRR Pathfinder v5.1 7-day Data for 1985 (NODC Accession Number 0051844)
4km NODC/RSMAS AVHRR Pathfinder v5.1 8-day Data for 1985 (NODC Accession Number 0051845)
The Version 5.0 and 5.1 Pathfinder SSTs require several important pieces of information. This information is categorized below by the four overall steps in the Pathfinder processing system (steps A-D).AVHRR Pathfinder SST Processing StepsA. Ingestion, calibration, and navigation of Global Area Coverage (GAC) data.-a. Calibrate and convert AVHRR digital counts for channels 1 through 5 to radiancesi. Obtain AVHRR channels 1 through 5 radiometer count data.ii. Channels 1 and 2 require pre-launch calibration coefficients for linear counts-to-radiance conversion, followed by a correction for temporal changes using sensor decay rate data and then a correction for inter-satellite differences using inter-satellite standardization data to the NOAA-9 reference, both of which use Libyan desert target area data.iii. Channels 3, 4, and 5 require both the above pre-launch calibration data and onboard blackbody (space view and sensor base plate) data for non-linear counts-to-radiance conversion.-b. Navigation, Clock, and Attitude Correctionsi. Satellite clock corrections need Earth time offset data based on RSMAS High-Resolution Picture Transmission data.ii. Attitude corrections are made using coastline comparison data.iii. At this point, navigated, calibrated albedos/brightness temperatures are available for all five channels. Note that channels 1-2 are not used in the Pathfinder SST algorithm, and channel 3 is used only in assignment of a quality indicator (see step B.d.i.).B. SST Calculation-a. Channel 4 and 5 brightness temperatures are converted to SST in degrees C using the Pathfinder algorithm, which requires a set of monthly coefficients.-b. These coefficients are derived using the Pathfinder Buoy Matchup Database. This is a set of in situ buoy SST observations and collocated AVHRR data.-c. In addition, a first-guess SST field is needed by the algorithm. This first-guess field is the Reynolds Weekly 1-degree Global Optimally Interpolated SST version 2 (OISSTv2) product. Note: the older 9km Pathfinder used OISST version 1. For v5.1 data, The Pathfinder algorithm uses a first guess SST provided by the Reynolds Optimum Interpolation 1/4-Degree Daily Global SST Analysis Version 2 (DOISSTv2) product. The DOISSTv2 is also used in the quality control procedures.-d. Quality Flag Assignmenti. A Channel 3, 4, and 5 brightness temperature test is performed. (These data are already available from step A.-a.iii.)ii. The viewing angle is evaluated using a satellite zenith angle check.iii. A reference field comparison check is made against the Reynolds OISSTv2 used in step B.-c.iv. A stray sunlight test is performed which requires information on whether the data in question are to left or right of nadir.v. An edge test is performed which checks the location of the pixel within a scan line and the location of the scan line within the processing piece (a 'piece' is a subset of an entire orbit file).vi. A glint test is performed which requires a glint index calculated according to the Cox and Munk (1954) formulation.vii. A sea ice mask is used to identify pixels falling on areas of sea ice. The ice mask is based on weekly SSM/I data and the ice information contained in the Reynolds OISSTv2. (Note: this step was not present in the 9 km Pathfinder reprocessing and is used only in the 4km Version 5.0 Pathfinder product.)viii. These steps are all combined into an overall quality flag assignment for each pixel.C. Spatial Binning-a. An equal-area is grid is defined into which GAC pixels are binned. No external data are needed, only information on the equal-area binning strategy itself.-b. A data-day is defined following a spatial data-day definition. See http://www.nodc.noaa.gov/sog/pathfinder4km/Data-day.pdf for a description of the spatial data-day definition, written by Guillermo Podesta, University of Miami RSMAS.-c. A land mask is applied to the dataset, identifying pixels that fall on land. This land mask was based on an old CIA database in the 9 km Pathfinder (no citation or further information is known). In the 4 km Version 5.0 Pathfinder, a new and improved land mask based on a 1 km resolution MODIS dataset derived by the USGS Land Processes Distributed Active Archive Center is used (see http://edcdaac.usgs.gov/modis/mod12q1.html for more info.)D. Temporal Binning-a. The spatially binned pieces from step C are accumulated into a single ascending (daytime) or descending (nighttime) file for each day. In case of overlapping satellite passes, only the best pixels of equivalent quality are binned. No external information is needed, only information about the accumulation procedure itself. Note: the new 4 km Version 5.0 Pathfinder also generates temporal averages on 5-day, 7-day, 8-day, monthly, and yearly periods.-b. A final comparison is made to an internal 3-week Pathfinder comparison field. No external data are required, only knowledge of the Pathfinder reference check.-c. Fields are reformatted from equal-area to equal-angle for distribution in HDF format. Note: the old 9 km Pathfinder data were distributed in HDF4 Raster format, while the new 4 km Version 5.0 Pathfinder data are distributed in HDF4-SDS format, with tiling (internally compressed chunks) enabled.-d. The result of all these steps is the high-level Pathfinder SST product. Note: The interim SST data (2007-2009) described in this metadata record were produced prior to the derivation of a final set of monthly coefficients for those years. The SST values were therefore calculated using the most recent set of coefficients available, and are considered Interim Pathfinder Version 5.0 data and not part of the Formal Pathfinder Version 5.0 data set. The algorithm used to create Version 5.1 data (1981-1985) is different only in that it replaces the Reynolds Weekly Optimally Interpolated SST Version 2 (OISSTv2) with the Reynolds Optimum Interpolation 1/4-degree Daily SST Analysis Version 2 (DOISSTv2) as the first guess SST and in the quality control procedures. The primary effect of this change is to retain more data in the high gradient regions and in regions where meandering or feature advection is present; effect on the retrieved SST is minimal.
NOAA National Oceanographic Data Center, SSMC3, 4th Floor, Room 4853, E/OC1, 1315 East-West Highway
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The all-pixel SST files contain values for each pixel location, including those contaminated with clouds or other sources of error. The Overall Quality Flag values may be used to filter out these unwanted values. The SST value in each pixel location is an average of the highest quality AVHRR Global Area Coverage (GAC) observations available in each roughly 4 km bin.SST is a difficult parameter to define exactly because the upper ocean (~10 m) has a complexand variable vertical temperature structure that is related to ocean turbulence and the air-seafluxes of heat, moisture and momentum. Definitions of SST provide a necessary theoreticalframework that can be used to understand the information content and relationships betweenmeasurements of SST made by different instruments. The following explanatory statementsattempt to provide this framework and encapsulate the effects of the dominant heat transportprocesses and time scale of variability associated with distinct vertical and volume regimeswithin a vertical element of the water column (horizontal and temporal variability is implicitlyassumed):-The interface SST, SSTint, is the temperature of an infinitely thinlayer at the exact air-sea interface. It represents the temperature at the top of the SSTskintemperature gradient (layer) and cannot be measured using current technology. It is important tonote that it is the SSTint that interacts with the atmosphere.-The skin SST, SSTskin, is a temperature measured within a thinwater layer (<500 micrometer) adjacent to the air-sea interface. It is where conductive, diffusiveand molecular heat transfer processes dominate. A strong vertical temperature gradient ischaracteristically maintained in this thin layer sustained by the magnitude and direction of theocean-atmosphere heat flux. Thus, SSTskin varies according to the actual measurement depthwithin the layer. This layer provides the connectivity between a turbulent ocean and a turbulentatmosphere.-The sub-skin SST, SSTsu
Modified from http://podaac.jpl.nasa.gov/ghrsst/SST-definitions.html
The .HDF files are 16-bit files, and pixel values can range from 0 to 65535 (2 to the 16th power). However,realistic pixel values for SST will always be less than 600 or so. SST in degrees C = (0.075 *pixel value) - 3.0, so a pixel value of 600 equals 42 degrees C, a temperature which exceedsnormal SST limits. Temperatures are represented in 0.075 degree C increments
Dr. Kenneth Casey, NOAA/NODC Technical Director
The Pathfinder algorithm uses a first guess SST provided by the Reynolds Optimally Interpolated SST Version 2 (OISSTv2) product. The OISSTv2 is also used in the quality control procedures.
The .HDF files are 16 bit files, and pixel values can range from 0 to 65535 (2 to the 16th power). However,realistic pixel values for first guess SST will always be less than 600 or so. First-guess SST indegrees C = (0.075 * pixel value) - 3.0, so a pixel value of 600 equals 42 degrees C, atemperature which exceeds normal SST limits. Temperatures are represented in 0.075 degree Cincrements
The Pathfinder algorithm uses a first guess SST provided by the Reynolds Optimum Interpolation 1/4-Degree Daily SST Analysis Version 2 (DOISSTv2) product. The DOISSTv2 is also used in the quality control procedures.
4 km Pathfinder User Guide (http://pathfinder.nodc.noaa.gov/userguide.html)
The .HDF files are 16 bit files, and pixel values can range from 0 to 65535 (2 to the 16th power). However, realistic pixel values for first guess SST will always be less than 600 or so. First-guess SST in degrees C = (0.075 * pixel value) 3.0, so a pixel value of 600 equals 42 degrees C, a temperature which exceeds normal SST limits. Temperatures are represented in 0.075 degree C increments.
Dr. Kenneth Casey, NOAA/NODC/Satellite Oceanography Group
The angular distance between an imaginary line around the earth parallel to its equator and the equator itself; North latitude values range from 0 to 90 degrees, South latitude values range from 0 to -90 degrees. Each data file contains a vector of latitude values corresponding to each row of the data array.
Derived from http://www.cogsci.princeton.edu
Longitude is measured from the Prime Meridian (the longitude that runs through Greenwich, England), with positive values going east (0 to180 degrees) and negative values going west (0 to -180 degrees). Each data file contains a vector of longitude values corresponding to each column of the data array.
Derived from: http://jwocky.gsfc.nasa.gov/
These files contain a mask code, which along with Mask 2, can be used to determine the tests in the hierarchical suite that were passed or failed, resulting in the Overall Quality Flag.
4 km Pathfinder Version 5.0 User Guide (http://www.nodc.noaa.gov/sog/pathfinder4km/userguide.html)
These files contain a mask code, which along withMask 1, can be used to determine the tests in the hierarchical suite that were passed or failed,resulting in the Overall Quality Flag.
4 km Pathfinder Version 5.0 User Guide(http://www.nodc.noaa.gov/sog/pathfinder4km/userguide.html)
This parameter indicates the number of AVHRR GAC observations falling in each approximately 4 km bin.
The overall quality flag is a relative assignment of SST quality based on a hierarchical suite of tests. The Quality Flag varies from 0 to 7, with 0 being the lowest quality and 7 the highest. For more information regarding the suite of tests, see Kilpatrick et al. (2001).
The standard deviation of the observations in each 4 km bin.
The .HDF files for standard deviation are 16 bit files, and pixel values can range from 0 to 65535 (2 to the 16thpower). Standard deviation of SST in degrees C = (0.15 * pixel value) - 0.0, so a pixel value of50 equals 7.5 degrees C for example. Standard deviations of SST are represented in 0.15 degreeC increments.
NOAA makes no warranty regarding these data, expressed or implied, nor does the fact of distribution constitute such a warranty. NOAA and NODC cannot assume liability for any damages caused by any errors or omissions in these data, nor as a result of the failure of these data to function on a particular system.
NCSA Hierarchical Data Format (HDF 4), Scientific Data Set (HDF-SDS)
Sea surface temperature (SST) values for each pixel location, first-guess SST provided by the Reynolds Optimally Interpolated SST Version 2 (OISSTv2) product (or the Reynolds Optimum Interpolation 1/4-Degree Daily SST Analysis Version 2 (DOISSTv2) product for v5.1 data), number of observations in each 4 km bin, standard deviation of the observations in each 4 km bin, overall quality flag, mask 1, and mask 2. (See the Supplemental Information in the 'Identification' section and the 'Entity and Attribute' section of this metadata record for a more detailed description of each parameter).
Joint Photographic Experts Group file format
Low-resolution .jpg graphics that correspond to an accompanying .hdf file. The entire 'dataset' of browse images is composed of a browse graphic for an ascending and descending pass for each of seven parameters: FirstGuessSST, Mask1, Mask2, NumberObservations, QualityFlag, SST, and StandardDeviation for a total of 14 images per .HDF file.
Data may be directly downloaded through the NODC website at: https://data.noaa.gov/onestop/. NODC can be contacted directly for custom orders. (When requesting data from the NODC, the desired data set may be referred to by the 7-digit NODC accession number associated with the dataset in the NODC archives). In addition, these data and accompanying browse graphics may be directly downloaded from the NODC FTP server at: ftp://data.nodc.noaa.gov/pub/data.nodc/pathfinder/
Contact the NODC User Services Group via phone/FAX/E-mail: nodc.services@noaa.gov
1315 East-West Highway, E/OC1, SSMC3, 4th Floor
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