Kenneth S. Casey, National Oceanic and Atmospheric Administration (NOAA) 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) 20041001 Unknown HDF-SDS version 4 not applicable Pathfinder Version 5.0 Silver Spring, Maryland NOAA National Oceanographic Data Center http://www.nodc.noaa.gov/sog/ 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 1985 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 5-day SST data and related parameters available for 1993. Data for all other years and time periods are available as separate NODC accessions. 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 set 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. 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. 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. This accession also includes a collection of value-added, cloud-screened products in HDF4. These products contain daytime, nighttime, and day-night averaged data of quality flags 4-7 only, as well as standard deviation and pixel count information. They have been produced from the original Pathfinder Version 5 data by NODC for daily, 5-day, 7-day, and monthly temporal averages at 4km and one degree spatial resolution, as well as five degree spatial resolution for monthly products. 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. 19930101 Unknown 19931231 Unknown publication date Complete As needed -180 180 90 -90 Global Change Master Directory EARTH SCIENCE > Biosphere > Aquatic Habitat > Coastal Habitat EARTH SCIENCE > Biosphere > Aquatic Habitat > Reef Habitat EARTH SCIENCE > Climate Indicators EARTH SCIENCE > Hydrosphere > Water Quality > Water Temperature EARTH SCIENCE > Oceans > Coastal Processes > Coral Reefs EARTH SCIENCE > Oceans > Ocean Temperature > Sea Surface Temperature EARTH SCIENCE > Oceans > Ocean Temperature > Sea Surface Temperature > AVHRR EARTH SCIENCE > Oceans > Ocean Temperature > Sea Surface Temperature > AVHRR >4km Pathfinder EARTH SCIENCE > Oceans > Ocean Temperature > Sea Surface Temperature > AVHRR >9km Pathfinder EARTH SCIENCE > Oceans > Ocean Temperature > Sea Surface Temperature > AVHRR >MCSST EARTH SCIENCE > Oceans > Ocean Temperature > Sea Surface Temperature > AVHRR >NLSST none Please acknowledge the use of these data with 'The Pathfinder Version 5.0 SST Data were provided by the NOAA National Oceanographic Data Center at URL: http://www.nodc.noaa.gov/sog/' Dr. Kenneth S. Casey NOAA National Oceanographic Data Center Physical scientist mailing address

NOAA National Oceanographic Data Center SSMC3, 4th Floor, Room 4853, Route: E/OC1 1315 East-West Highway

Silver Spring Maryland 20910 U.S.A. (301) 713-3272 x133 FAX: (301) 713-3300 Kenneth.Casey@noaa.gov 9:00 AM-4:00 PM, EST Phone/FAX/E-mail/letter OBSDATE.[BITCODE][RESO][AVGPERIOD][DAYNIGHT]pfv50-TYPE(-BITS).hdf.jpg Low-resolution graphics for 5-day 1993 averaged data JPEG Kenneth S. Casey, National Oceanographic Data Center (NODC), and Edward J. Kearns, Vicki Halliwell, and Robert Evans, University of Miami, Rosential School of Marine and Atmospheric Science (RSMAS) none Unclassified not applicable NCSA Hierarchical Data Format (HDF 4), Scientific Data Set (HDF-SDS) This accession contains 14 yearly files (approx. .10 GB), which follow the file naming convention described below. Each file also has an accompanying low-resolution graphic. OBSDATE.[BITCODE][RESO][AVGPERIOD][DAYNIGHT]pfv50-TYPE(-BITS).hdf (for example: 1985.s04y1pfv50-bsst-16b.hdf) Where: OBSDATE = The date(s) the observations were made. OBSDATE may be in one of the following forms: - Daily Files: YYYYDDD, with: YYYY = 4 digit year of observation (1985-200x) DDD = 3 digit day of year (001-365, or 001-366 for leap years) For help converting between calendar dates and day of year, please see our Calendar Date Conversion Chart - 5-Day Files: SYYYYDDD-EYYYYDDD, with: SYYYYDDD = starting 4-digit year and 3-digit day EYYYYDDD = ending 4-digit year and 3-digit day - 7-Day Files: YYYYWW, with: YYYY = 4 digit year of observation WW = 2-digit week number between 01 and 52 - 8-Day Files: SYYYYDDD-EYYYYDDD, with: SYYYYDDD = starting 4-digit year and 3-digit day EYYYYDDD = ending 4-digit year and 3-digit day - Monthly Files: YYYYMM, with: YYYY = 4 digit year of observation MM = 2-digit month between 01 and 12 - Yearly Files: YYYY, with: YYYY = 4 digit year of observation BITCODE = Indicates the bit length of the pixel values in the file. "s" is for 16 bit files, "m" is for 8 bit files (see BITS below) RESO = Approximate resolution in km. Set to "04" for 4 km files AVGPERIOD = Indicates the averaging period used to create the file. AVGPERIOD may be in one of the following forms: Daily Files = "d" 5-Day Files = "5" 7-Day Files = "w" 8-Day Files = "8" Monthly Files = "m" Yearly Files = "y" DAYNIGHT = Indicates nighttime, descending pass (1) or daytime, ascending pass (3) observations pfv50 = Shorthand for "Pathfinder Version 5.0" TYPE = Indicates the type of data stored in the file. TYPE may be one of the following: sst: Pathfinder all-pixel SST bsst: OISSTv2 first-guess SST field sdev: Standard deviation num: Number of observations qual: Overall quality value msk1: Quality mask 1 msk2: Quality mask 2 BITS = Number of bits in each pixel. Only present for 16-bit files (-16b) hdf = Indicates HDF-SDS Version 4 file format University of Miami Rosenstiel School of Marine and Atmospheric Science 20010630 185600 none website Miami, FL Remote Sensing Group, RSMAS http://www.rsmas.miami.edu/groups/rrsl/pathfinder/ NOAA National Environmental, Satellite, Data, and Information Services (NESDIS)/National Climatic Data Center (NCDC) 19981130 Unknown November 1998 website Asheville, North Carolina NOAA National Climatic Data Center http://www2.ncdc.noaa.gov/docs/podug/ NASA/Jet Propulsion Laboratory Physical Oceanography 20031107 115600 website Pasadena, CA NASA/Jet Propulsion Laboratory http://podaac.jpl.nasa.gov/sst/ Casey, K.S., and P. Cornillon 19990630 Unknown journal article none J. Climate, Volume 12, No. 6 Boston, MA American Meteorological Society in pp. 1848-1862 http://ams.allenpress.com/amsonline/?request=index-html American Meteorological Society 19990630 Unknown journal None Vol. 12, No. 6 Boston, MA American Meteorological Society http://ams.allenpress.com/amsonline/?request=get-archive Casey, K.S., and P. Cornillon 20010930 Unknown journal article None J. Climate, Volume 14, No. 18 Boston, MA American Meteorological Society pp. 3801-3818 http://ams.allenpress.com/amsonline/?request=index-html American Meteorological Society 20010930 Unknown journal None Volume 14, No. 18 Boston, MA American Meteorological Society http://ams.allenpress.com/amsonline/?request=get-archive Reynolds, R. W., N. A. Rayner, T. M. Smith, D. C. Stokes, and W. Wang 20020730 Unknown journal article None J. Climate, Volume 15, No. 13 Boston, MA American Meteorological Society pp. 1609-1625 http://ams.allenpress.com/amsonline/?request=index-html American Meteorological Society 20020730 Unknown journal None Volume 15, No.13 Boston, MA American Meteorological Society http://ams.allenpress.com/amsonline/?request=get-archive Kearns, E. J., Hanafin, J. A., Evans, R. H., Minnett, P. J., and Brown, O. B. 20000730 Unknown journal article None Bull. Amer. Met. Soc. 81, No. 7 Boston, Ma American Meteorological Society pp. 1525-1536 http://ams.allenpress.com/amsonline/?request=get-archive&issn=1520-0477 American Meteorological Society 20000730 Unknown journal None Volume 81, No. 7 Boston, MA American Meteorological Society http://ams.allenpress.com/amsonline/?request=get-archive Barton, I. J. 19950530 Unknown journal article None J. Geophys. Res., Volume 100, No. C5 Washington, DC American Geophysical Union pp. 8777-8790 http://www.agu.org/pubs/crossref/1995/95JC00365.shtml American Geophysical Union 19950530 Unknown Oceans journal None Volume 100, No. C5 Washington, DC American Geophysical Union http://www.agu.org/journals/jc/ Kilpatrick, K. A., Podesta, G. P., and Evans, R. 20010530 Unknown journal article None Jour. Geophys. Res., Volume 106, No. C5 Washington, DC American Geophysical Union pp. 9179-9197 http://www.agu.org/journals/jc/jc0105/1999JC000065/0.html American Geophysical Union 20010530 Unknown Oceans journal None Volume 106, No. C5 Washington, DC American Geophysical Union http://www.agu.org/journals/jc/ Rayner, N. A., D. E. Parker, E. B. Horton, C. K. Folland, L. V. Alexander, D. P. Rowell, E. C. Kent and A. Kaplan 20030730 Unknown journal article None Jour. Geophys. Res., Vol. 108 (No. D14),4407,10.1029/2002JD002670 Washington, DC American Geophysical Union http://www.agu.org/journals/jd/jd0314/2002JD002670/index.html American Geophysical Union 20030730 Unknown Oceans journal None Vol. 108 (No. D14),4407,10.1029/2002JD002670 Washington, DC American Geophysical Union http://www.agu.org/journals/jd/jd0314/2002JD002670/index.html Schluessel, P., W. J. Emery, H. Grassl, and T. Mammen 19900815 Unknown Oceans journal article None Jour. Geophys. Res., Vol. 95, No. C8 Washington, DC American Geophysical Union pp. 13,341-13,356. American Geophysical Union 19900815 Unknown Oceans journal None Vol. 95, No. C8 Washington, DC American Geophysical Union Minnett, P.J. and B. Ward 20001230 Unknown symposia proceedings The Netherlands European Space Agency European Space Agency 20001230 Unknown book The Netherlands European Space Agency For copies of proceedings, contact: ESA Publications Division ESTEC-Finance Division (ADM-FT) P.O. Box 299-2200 AG Noordwijk The Netherlands FAX +31 (0)71 565 5433 http://esapub.esrin.esa.it/bulletin/bullet105/publicat105.pdf 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 NOAA-9 (launched December 12, 1984) to NOAA-16 Polar Operational Environmental Satellites (POES). As of November 2003, NOAA was operating five polar orbiters. A new series of polar orbiters, with improved sensors, began with the launch of NOAA-15 in May 1998 and NOAA-16 on September 21, 2000. The newest, NOAA-17, was launched June 24, 2002. NOAA-12, NOAA-14 and NOAA-15 all continue transmitting data as stand-by satellites. NOAA-16 and NOAA-17 are classified as the 'operational' satellites. 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 a 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 for a discussion of sources of error in geo-locating AVHRR data. The Version 5.0 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 Steps A. Ingestion, calibration, and navigation of Global Area Coverage (GAC) data a. Calibrate and convert AVHRR digital counts for channels 1 through 5 to radiances i. 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 Corrections i. 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 Global Optimally Interpolated SST version 2 (OISSTv2) product. Note: the older 9km Pathfinder used OISST version 1. d. Quality Flag Assignment i. 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. 20040701 Dr. Kenneth S. Casey NOAA/NESDIS National Oceanographic Data Center Physical scientist mailing address

NOAA/NESDIS National Oceanographic Data Center SSMC3, 4th Floor, Room 4853, Route: E/OC1 1315 East-West Highway

Silver Spring Maryland 20910 U.S.A. (301)713-3272 x133 FAX:(301)713-3300 Kenneth.Casey@noaa.gov 9:00 AM-4:00 PM, EST Phone/FAX/E-mail/letter Unknown Raster Grid Cell 4096 8192 1 0.0439453125 0.0439453125 Decimal degrees WGS84 WGS84 6378137 298.257223563 Pathfinder Version 5.0 5-day SST Data for 1993 5-day temporal averages of SST data and related parameters for 1993. Related parameters include first-guess SST, number of observations, standard deviation, overall quality flag, mask 1, and mask 2 (defined in the Attribute Labels section of this metadata record). Each of the seven parameter files listed contains a mapped array with 8192 elements in longitude and 4096 in latitude, plus a vector of length 8192 identifying the longitudes and a vector with 4096 values indicating the latitudes. There are also global tags describing the entire contents as well as tags describing each of the 2 vectors and 1 array. The seven parameters are stored either as 8-bit or 16-bit unsigned integers which may be converted linearly (y = mx + b) to geophysical units using a scale (i.e., slope=m) and offset (i.e., intercept=b) according to the following table: PARAMETER # BITS SCALE OFFSET UNITS "All-pixel" SST: 16 bit 0.075 -3.0 Deg C First-guess SST: 16 bit 0.075 -3.0 Deg C Standard Deviation: 16 bit 0.150 0.0 Deg C Number of Observations: 8 bit 1.000 0.0 Unitless Overall Quality Flag: 8 bit 1.000 0.0* Unitless Mask 1: 8 bit 1.000 0.0 Unitless Mask 2: 8 bit 1.000 0.0 Unitless * - Note that the offset parameter in the Overall Quality Flag files is incorrectly set to a value of 1. The value of 0 listed here is correct. NOAA National Oceanographic Data Center/Satellite Oceanography Group All Pixel Sea Surface Temperature (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. SST is a difficult parameter to define exactly because the upper ocean (~10 m) has a complex and variable vertical temperature structure that is related to ocean turbulence and the air-sea fluxes of heat, moisture and momentum. Definitions of SST provide a necessary theoretical framework that can be used to understand the information content and relationships between measurements of SST made by different instruments. The following explanatory statements attempt to provide this framework and encapsulate the effects of the dominant heat transport processes and time scale of variability associated with distinct vertical and volume regimes within a vertical element of the water column (horizontal and temporal variability is implicitly assumed): -The interface SST, SSTint, is the temperature of an infinitely thin layer at the exact air-sea interface. It represents the temperature at the top of the SSTskin temperature gradient (layer) and cannot be measured using current technology. It is important to note that it is the SSTint that interacts with the atmosphere. -The skin SST, SSTskin, is a temperature measured within a thin water layer (<500 micrometer) adjacent to the air-sea interface. It is where conductive, diffusive and molecular heat transfer processes dominate. A strong vertical temperature gradient is characteristically maintained in this thin layer sustained by the magnitude and direction of the ocean-atmosphere heat flux. Thus, SSTskin varies according to the actual measurement depth within the layer. This layer provides the connectivity between a turbulent ocean and a turbulent atmosphere. -The sub-skin SST, SSTsub-skin, is representative of the SST at the bottom of the surface layer where the dominance of molecular and conductive processes gives way to turbulent heat transfer. It varies on a time scale of minutes and is influenced by solar warming in a manner strongly dependent on the turbulent energy density in the layer below. -The near surface ocean temperature (~10 m) is significantly influenced by local solar heating and typically varies with depth over a time scale of hours. Consequently "SST" measurements should always be referenced against a specific depth or an average over a depth range. The notation SSTdepth refers to any temperature within the water column beneath the SSTsub-skin where turbulent heat transfer processes dominate. The traditional "bulk" SST is related to this measure. SSTdepth should always be quoted at a specific depth in the water column; e.g., SST1m refers to the SST at a depth of 1m. The SSTskin is the closest parameter actually measured by the AVHRR satellite radiometer. However, because the Pathfinder algorithm regresses the satellite-observed radiances against buoy temperatures to determine a "bulk" SST, the actual SST is akin to the SSTdepth where depth is about 1 m. Modified from http://podaac.jpl.nasa.gov/ghrsst/SST-definitions.html sea surface temperature 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 exceeds normal SST limits. Temperatures are represented in 0.075 degree C increments Dr. Kenneth Casey, NOAA/NODC/Satellite Oceanography Group 19850101 20011231 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. 4 km Pathfinder Version 5.0 User Guide (http://www.nodc.noaa.gov/sog/pathfinder4km/userguide.html) first guess sea surface temperature 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 19850101 20011231 Latitude 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 -90 90 decimal degrees 0.000000001 19850101 20011231 Longitude 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/ -180 180 decimal degrees 0.0000000001 19850101 20011231 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. 4 km Pathfinder Version 5.0 User Guide (http://www.nodc.noaa.gov/sog/pathfinder4km/userguide.html) 0 255 unitless 1 19850101 20011231 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. 4 km Pathfinder Version 5.0 User Guide (http://www.nodc.noaa.gov/sog/pathfinder4km/userguide.html) 0 255 unitless 1 19850101 20011231 Number of observations This parameter indicates the number of AVHRR GAC observations falling in each approximately 4 km bin. 4 km Pathfinder Version 5.0 User Guide (http://www.nodc.noaa.gov/sog/pathfinder4km/userguide.html) 0 255 number of observations 1 19850101 20011231 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 Kilpatrick et al. (2001). 4 km Pathfinder Version 5.0 User Guide (http://www.nodc.noaa.gov/sog/pathfinder4km/userguide.html) 0 7 quality level 1 19850101 20011231 Standard deviation The standard deviation of the observations in each 4 km bin. 4 km Pathfinder Version 5.0 User Guide (http://www.nodc.noaa.gov/sog/pathfinder4km/userguide.html) standard deviation of sea surface temperature The .HDF files for standard deviation are 16 bit files, and pixel values can range from 0 to 65535 (2 to the 16th power). Standard deviation of SST in degrees C = (0.15 * pixel value) - 0.0, so a pixel value of 50 equals 7.5 degrees C for example. Standard deviations of SST are represented in 0.15 degree C increments. Dr. Kenneth Casey, NOAA/NODC/Satellite Oceanography Group 19850101 20011231 The data set contains a 4 km resolution time series of temporally averaged 5-day sea surface temperatures for 1993. The time series includes (a) SST values for each pixel location (all-pixel SST files), (b) first-guess SST, (c) number of observations falling in each 4 km bin, (d) standard deviation of the observations in each 4 km bin, (e) overall SST quality flag (from the lowest quality of 0 to the highest quality of 7), and (f, g) tests that were passed and failed to determine the overall quality flag (masks 1 and 2). 4 km Pathfinder Version 5.0 User Guide (http://www.nodc.noaa.gov/sog/pathfinder4km/userguide.html) NOAA National Oceanographic Data Center not applicable mailing and physical address

SSMC3, 4th Floor, E/OC1 1315 East-West Highway

Silver Spring MD 20910 U.S.A 301-713-3277 or 301-713-3280 301-713-3301 nodc.services@noaa.gov 8:00 - 6:00 PM, EST Phone/FAX/E-mail/letter during business hours NODC Accession Number 0001771 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. .HDF 4.0 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, 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 of this metadata record for a more detailed description of each parameter). HDF-SDS files employ internal "deflate"compression which is identical to "gzip" compression. 6832 ftp://data.nodc.noaa.gov/pub/data.nodc/pathfinder/Version5.0/ Direct FTP access: Navigate to ftp://data.nodc.noaa.gov/pub/data.nodc/pathfinder/Version5.0/ Use any FTP client to begin downloading data. Any FTP client http://data.nodc.noaa.gov/pathfinder/Version5.0 Simple Web access: Navigate to URL: http://data.nodc.noaa.gov/pathfinder/Version5.0 and begin browsing through the file hierarchy. Clicking on any of the files will prompt you to download that file or will launch any application associated with HDF files. Standard Internet browser and/or software capable of utilizing .HDF files http://data.nodc.noaa.gov/cgi-bin/nph-dods/pathfinder/Version5.0 These data are also served using OPeNDAP (formerly DODS) server. The base URL is: http://data.nodc.noaa.gov/cgi-bin/nph-dods/pathfinder/Version5.0 In addition, links are provided in the table at URL: http://www.nodc.noaa.gov/sog/pathfinder4km/available.html (4km Pathfinder Data Availability Table) to access the OPeNDAP directory listings. For a listing of OPeNDAP clients which may be used to access the 4 km Pathfinder data (as well as any other OPeNDAP-enabled data sets), please see the OPeNDAP web site at URL: http://opendap.org/ and follow the link called "Download". Examine the list of "Clients" for various mechanisms to access and display the data directly using OPeNDAP. For example, the OPeNDAP Data Connector is an excellent standalone client which will allow you to quickly search, access, browse, and even generate images of the Pathfinder SST data. Standard Internet browser; OPeNDAP software as needed/desired http://www.nodc.noaa.gov/search/prod/ Data may also be directly downloaded through the NODC website at: http://www.nodc.noaa.gov/search/prod/. 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 number given in the RESOURCE DESCRIPTION field of this metadata record). Standard Internet browser; FTP capability .JPG 20040930 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. None 32 http://data.nodc.noaa.gov/pathfinder/Version5.0/browse_images/5day/ Browse graphics may be downloaded directly by desired period through URL: http://data.nodc.noaa.gov/pathfinder/Version5.0/browse_images. PC, Mac, Unix, or other; standard Internet browser None These data are available from multiple online sources; see the "DIGITAL FORM" section of this metadata record and follow the instructions for "Online Options". 24 hours if downloaded via the Internet Contact the NODC User Services Group via phone/FAX/E-mail: nodc.services@noaa.gov PC, Mac, UNIX or other, standard Internet browser, ability to work with/utilize .HDF files strongly recommended. 20041001 Unknown Present Unknown 20040831 20040927 20050615 Sheri Phillips and Amanda Lowe NOAA/NODC Oceanographer mailing address

1315 East-West Highway, E/OC1, SSMC3, 4th Floor

Silver Spring MD 20910 U.S.A. 301-713-3280 x127 301-713-3302 sheri.phillips@noaa.gov 9:30 AM - 6 PM Monday-Thursday E-mail, phone, FAX, mail FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998 local time None None None Unclassified None