World Ocean Atlas 1998 (WOA98) CD-ROM Documentation version 1.0 Ocean Climate Laboratory National Oceanographic Data Center April 1999 1. INTRODUCTION The World Ocean Atlas 1998 (WOA98) consists of 3 CD-ROMs containing objectively analyzed fields of temperature, salinity,dissolved oxygen, derived oxygen variables (Apparent Oxygen Utilization and oxygen saturation), nutrients (phosphate, nitrate, silicate) and chlorophyll along with fields of various statistics. This CD-ROM set is associated with the following products: NOAA Atlas NESDIS World Ocean Atlas 1998 series (12 volumes): contains figures showing objectively analyzed fields of each variable for various climatological compositing periods (annual, seasonal, monthly) at selected standard depth levels and a description of the methods used to generate the objectively analyzed fields; World Ocean Database 1998 (WOD98) CD-ROM set: contains bserved and standard level flagged data used to generate the WOA98 fields. WOD98 consists of 5 CD-ROMs; World Ocean Database 1998 atlas series, an eight volume series detailing the source of the WOD98 data and showing distribution plots for each variable as a function of year. 2. CONTENTS OF WOA98 The data on each WOA98 CD-ROM consists of: statistics of observed (vertically interpolated) data (unanalyzed) for one-degree squares and five-degree squares at standard depth levels (see table 1). The following statistics for each grid square are included: 1) number of observations, 2) mean, 3) standard deviation, 4) standard error of the mean. See table 2 for availability of statistics by variable; annual, seasonal, and monthly objectively analyzed mean fields by one- degree squares at standard depth levels. See table 2 for availability of objective analyses by variable; "interpolation error" of the objectively analyzed fields defined as fields of observed means minus annual objectively analyzed mean by one- degree squares at standard depth levels. See table 2 for availability of these fields by variable; seasonal and monthly objectively analyzed fields minus annual mean objectively analyzed fields by one-degree squares at standard depth levels. See table 3 for availability of these fields by variable; land/ocean-bottom mask used in the analyses at standard depth levels; definition of basins used in the objective analyses at standard depth levels (see table 4). The seasons are defined as Winter (January-March), Spring (April-June), Summer (July-September), Fall (October-December) (based on the Northern Hemisphere). Table 1 lists the depths and Table 2 the available files for each variable in WOA98. 3. DIRECTORY STRUCTURE The objectively analyzed fields and associated statistics for temperature, salinity, oxygen, nutrients, and chlorophyll are in three CD-ROMs: WOA98-01 annual, seasonal, monthly fields for temperature and salinity, WOA98-02 annual, seasonal, monthly fields for oxygen and the derived variables Apparent Oxygen Utilization and % oxygen saturation. WOA98-03 annual and seasonal fields for phosphate, nitrate, silicate, and chlorophyll There are four types of directories within each CD-ROM: masks, programs, utils, and variable data directories (variable data directories are identified by the variable name e.g. temperature, salinity, etc.. Figure 1 shows an example of the directory structure for temperature on WOA98-01. A readme.htm, readme.wpd, and readme.txt files, containing HTML, Word Perfect 8, and text files of this documentation are also included in the CD-ROM. The following "gif" images are also contained in this directory as they are needed when viewing the HTML version of the documentation: coordin1.gif and coordin5.gif. masks directory: basin.msk - basin mask used in the objective analysis. There are 33 standard depth levels for which each numeric one degree value corresponds to the number given for the corresponding basin in Table 4, columns 1 and 4. landsea.msk - bottom depth assigned to each one-degree latitude by one- degree longitude square. Numerical values correspond to the depth levels given in Table 1. programs directory: analysis.for - FORTRAN program to print out a latitude-longitude area from a user requested file analysis.c - C program to print out a latitude-longitude area from a user requested file analysis.exe - DOS executable program to print out a latitude-longitude area from a user requested file. utils directory: gzip directory gzip124.exe - self-extracting DOS executable gzip-1.2.4.tar.Z - compressed and tar'd file containing source code for UNIX users temperat directory (WOA98-01) salinity directory (WOA98-01) oxygen directory (WOA98-02) o2sat directory - percent oxygen saturation data (WOA98-02) aou directory - Apparent Oxygen Utilization data (WOA98-02) phosph directory (WOA98-03) nitrate directory (WOA98-03) silicate directory (WOA98-03) chloroph directory (WOA98-03) Each variable data directory in WOA98-01 and WOA98-02 contains three subdirectories: annual directory - annual objective analyses and statistics at standard depth levels seasonal directory - seasonal objective analyses and statistics at standard depth levels monthly directory - monthly objective analyses and statistics at standard depth levels. Each variable data directory in WOA98-03 contains two subdirectories: annual directory - annual objective analyses and statistics at standard depth levels seasonal directory - seasonal objective analyses and statistics at standard depth levels. The following file types are contained within the annual, seasonal, and monthly directories: Analyzed mean fields ( an) - For temperature, salinity, and oxygen: Each annual mean field is the average of the 12 analyzed monthly mean fields at and above 1500 meters. Below 1500 m the average of the four seasonal analyzed fields is used. The seasonal mean fields above 1500 m are the average of the appropriate three monthly fields. Below 1500 m the seasonal analyzed mean fields are the all-data analyses of each season. The monthly analyzed mean fields are all-data analyses. For phosphate, nitrate, silicate, chlorophyll: Each annual mean field is the average of the four analyzed seasonal mean fields at and above 500 meters (surface for chlorophyll). Below 500 m (0 m for chlorophyll) the annual fields are all-data analyses. The seasonal mean fields are all-data analyses. Seasonal or monthly fields minus annual fields (ma) - one-degree seasonal minus annual analyzed fields. Grid point fields (gp) - the number of grid points which contain data within the radius of influence for each grid box. Data distribution field (dd) - geographic distribution of data used in analysis Standard deviation field (sd) - standard deviation from the mean by one- degree squares Standard error of the mean (se) - standard error of the mean by one-degree squares Means (mn) - unanalyzed one-degree means for all data used in analysis Observed minus annual (oa) - analyzed mean field subtracted from one-degree raw (unanalyzed) means. 4. DATA FORMAT Each individual datum is stored in one of two ways: For gp (grid point) files and dd (data distribution) files, the value is stored as an 8 digit numeral followed by a decimal point (FORTRAN f8.0). The missing value is -100.. This is also the form for basin.msk and landsea.msk. For gp, dd and basin.msk files, missing value is reserved for land/ocean-bottom. Any ocean point without data values is set to zero. The landsea.msk file has no missing values. For all other files (an, se, sd, mn, ma), values are stored as an eight digit real with 4 places to the left of the decimal (FORTAN f8.4). The missing value is -99.9999. Missing values are used for land/ocean-bottom and for ocean points without data. The reason for the two different formats is that dd and gp files may have values greater than 999., which can not be accommodated in the later format. For both cases, there are 10 values per line, followed by a return. The first value in a one-degree square file corresponds to the grid square from 89.0ø S to 90.0ø S latitude and 0.0ø E to 1.0ø E longitude for one-degree data (grid square 1,1). The first 360 values are incremented eastward in longitude, constant in latitude. The 361st value in the file is for the grid square 88.0øS to 89.0ø S latitude, 0.0ø E to 1.0ø E longitude. Figure 2 shows the one-degree coordinate system of the analyzed fields. The five-degree square files follow the same pattern, listing 72x36 values. Figure 3 shows the five-degree coordinate system. Program analysis.for is a sample program which can be used as a template for reading in data in FORTRAN, analysis.c is a C sample program, analysis.exe is a DOS executable version of the above programs. 5. FILE NAMING CONVENTION FOR ANALYZED DATA AND STATISTICS All the files in the directories containing the data follow the same naming convention: [p][tp][ft][g].gz where: [p] = parameter: t = temperature s = salinity o = dissolved oxygen x = percent oxygen saturation a = Apparent Oxygen Utilization p = phosphate n = nitrate i = silicate c = chlorophyll [tp] = time period: 00 = all data annual 13 - 16 = seasons (starting with Winter (Jan-Mar)) 01 - 12 = months (starting with January) [ft] = file type: an = analyzed mean field dd = distribution of data sd = standard deviation of data se = standard error of the mean of data mn = raw (unanalyzed) mean of data oa = observed (raw) mean minus analyzed field gp = number of grid points containing data within the radius of influence around present grid point [g] = one-degree (1) or 5-degree (5) square file Example: t14se1.gz = compressed file for one-degree square standard error of the mean for spring temperature. 6. util DIRECTORY Within the util directory of each CD-ROM there is a GZIP directory which contains two files used for decompressing the data on the WOA98. The first (GZIP124.EXE) is a self-extracting DOS executable and the second (gzip-1.2.4.tar.Z) is a compressed and tar'd file containing source code for UNIX users. This file may appear as gzip-1~1.Z. a. Installing gzip For the First Time DOS Users: The file gzip124.exe is a self-extracting DOS executable. Copy gzip124.exe to your hard drive. Run gzip124.exe and use the file gzip.exe to decompress data as described below. UNIX Users: Copy gzip-1.2.4.tar.Z to your UNIX system. If the file name is gzip-1~1.Z, rename it to gzip-1.2.4.tar.Z. Run the following commands: decompress gzip-1.2.4.tar.Z tar xvf gzip-1.2.4.tar These commands will create a directory named gzip-1.2.4 which include the gzip source code and documentation on copyrights, compression methods and how to compile and install the gzip code. Read through the README file and when ready to build the gzip executable, follow the instructions in the INSTALL file. b. Decompressing Data From WOD98 To decompress the contents of a directory and all of it's subdirectories: gzip -ndr If an older version of gzip is used, the -n option is required in order to preserve the correct file names. Special Note for UNIX Users The DOS CR-LF (Carriage Return-Line Feed (^M)) indicates the end of a record and may cause problems when working in a UNIX environment. Many systems have a "dos2unix" program which removes these characters from an ASCII file. Files can also be converted by transferring from DOS/WINDOWS using FTP (File Transfer Protocol). The UNIX "tr" or "perl" utilities will also remove the CR-LF. a. To use the UNIX translate utility, "tr": tr -d '\r' < original_filename > new_filename (Note that the "<" and ">" must be typed for this command to work). b. To use the UNIX perl utility: perl -pi -e 's/\r\n/\n/g' filename --------------------------------------------- --------------------------------------------- Table 1. Standard levels and depths (meters) Depth Level Depth Level Depth Level -------------------------------------------- 0 1 300 12 1400 23 10 2 400 13 1500 24 20 3 500 14 1750 25 30 4 600 15 2000 26 50 5 700 16 2500 27 75 6 800 17 3000 28 100 7 900 18 3500 29 125 8 1000 19 4000 30 150 9 1100 20 4500 31 200 10 1200 21 5000 32 250 11 1300 22 5500 33 --------------------------------------------------------- Table 2. Availability of fields for each variable and the maximum depth for each data type. An X indicates that these files are not available for the specified variable. Variable Annual Seasonal Monthly ----------------------------------------------- Temperature 5500 5500 1500 Salinity 5500 5500 1500 Dissolved Oxygen 5500 5500 1500 Apparent Oxygen Utilization 5500 5500 1500 Oxygen Saturation 5500 5500 1500 Phosphate 5500 500 X Nitrate 5500 500 X Silicate 5500 500 X Chlorophyll 100 surface X Table 3. Availability of difference fields for each variable and the maximum depth available for each variable. An X indicates that these files are not available for the specified variable. Variable Seasonal Monthly --------------------------------------------- Temperature 1500 1500 Salinity 1500 1500 Dissolved Oxygen 1500 1500 Apparent Oxygen Utilization 1500 1500 Oxygen Saturation 1500 1500 Phosphate 500 X Nitrate 500 X Silicate 500 X Chlorophyll surface X Table 4. Basins defined for objective analysis and the shallowest standard depth level for which each basin is defined. # BASIN STANDARD DEPTH # BASIN STANDARD DEPTH ------------------------------------------------------------------------- 1 Atlantic Ocean 1 29 Fiji Basin 29 2 Pacific Ocean 1 30 North American Basin 29 3 Indian Ocean 1 31 West European Basin 29 4 Mediterranean 1 32 Southeast Indian Basin 29 5 Baltic Sea 1 33 Coral Sea 29 6 Black Sea 1 34 East Indian Ocean 29 7 Red Sea 1 35 Central Indian Ocean 29 8 Persian Gulf 1 36 Southwest Atlantic 29 9 Hudson Bay 1 37 Southeast Atlantic 29 10 Southern Ocean 1 38 Southeast Pacific 29 11 Arctic Ocean 1 39 Guatemala Basin 29 12 Sea of Japan 1 40 East Caroline Basin 30 13 Kara Sea 8 41 Marianas Basin 30 14 Sulu Sea 10 42 Philippine Sea 30 15 Baffin Bay 14 43 Arabian Sea 30 16 East Mediterr. 16 44 Chile Basin 30 17 West Mediterr. 19 45 Somali Basin 30 18 Sea of Okhotsk 19 46 Mascarene Basin 30 19 Banda Sea 23 47 Crosat Basin 30 20 Caribbean Sea 23 48 Guinea Basin 30 21 Andaman Basin 25 49 Brazil Basin 31 22 North Caribbea 26 50 Argentine Basin 31 23 Gulf of Mexico 26 51 Tasman Sea 30 24 Beaufort Sea 28 52 Atlantic Indian Basin 31 25 South ChinaSea 28 53 Caspian Sea 1 26 Barents Sea 28 56 Bay of Bengal 1 27 Celebes Sea 25 57 Java Sea 6 28 Aleutian Basin 28 Figure 1. Directory structure for the temperature data in WOA98-01. Bold denotes directories, italics denotes file names. "xx" denotes time period, 13-16 for the seasons, and 01-12 for the monthly files. readme.ps readme.wpd readme.txt coordin1.gif coordin5.gif programs analysis.for analysis.c analysis.exe mask basin.msk landsea.msk temperat annual seasonal monthly t00an1.gz txxan1.gz txxan1.gz an1= one-degree analyzed field t00dd1.gz txxdd1.gz txxdd1.gz dd1= one-degree data distribution t00dd5.gz txxdd5.gz txxdd5.gz dd5= five-degree data distribution t00gp1.gz txxgp1.gz txxgp1.gz gp1= one-degree grid points containing data within the influence region t00mn1.gz txxmn1.gz txxmn1.gz mn1= unanalyzed one-degree mean t00mn5.gz txxmn5.gz txxmn5.gz mn5= unanalyzed five-degree mean t00oa1.gz txxoa1.gz txxoa1.gz oa1= observed mean minus analyzed t00sd1.gz txxsd1.gz txxsd1.gz sd1= one-degree standard deviation t00sd5.gz txxsd5.gz txxsd5.gz sd5= five-degree standard deviation t00se1.gz txxse1.gz txxse1.gz se1= one-degree standard error t00se5.gz txxse5.gz txxse5.gz se5= five-degree standard error txxma1.gz txxma1.gz ma1= seasonal or monthly mean minus annual fields utils gzip gzip124.exe gzip-1.2.4.tar.Z Figure 2. One-degree horizontal co-ordinate system of the analyzed fields. GREENWICH 360,180|1,180 | | | | | | | 359,91/360,91|1,91/2,91 EQUATOR W ________________________|________________________ E 360,90| | | | | | | 360,2|1,2 360,1|1,1 Figure 3. Five-degree horizontal co-ordinate system of the analyzed fields. GREENWICH |72,36|1,36| | | | | | | | 71,19/72,19|1,19/2,19 EQUATOR W ________________________|________________________ E | | | | | | | 72,2|1,2 72,1|1,1