Radiation Budget From ERB 1. TYPE OF DATA 1.1 Parameter/Measurement 1.2 Unit of Measurement 1.3 Data Source 1.4 Data Set Identification 2. SPATIAL CHARACTERISTICS 3. TEMPORAL CHARACTERISTICS 3.1 Temporal Coverage 3.2 Temporal Resolution 4. INSTRUMENT DESCRIPTION 4.1 Principles of Operation 4.2 Instrument Measurement Geometry 5. DATA PROCESSING SEQUENCE 5.1 Processing Steps and Data Sets 5.2 Derivation Techniques/Algorithms 5.3 Special Corrections/Adjustments 5.4 Processing Changes 6. QUALITY ASSESSMENT 6.1 Data Validation by Producer 6.2 Confidence Level/Accuracy Judgment 6.3 Usage Guidance 7. CONTACTS FOR DATA PRODUCTION INFORMATION 8. OUTPUT PRODUCTS AND AVAILABILITY 8.1 Tape Products 8.2 Film Products 8.3 Other Products 9. DATA ACCESS 9.1 Archive Identification 9.2 Procedures for Obtaining Data 9.3 NCDS Status/Plans 10. CONTACTS FOR ARCHIVE/DATA ACCESS INFORMATION 11. REFERENCES 11.1 Satellite/Instrument/Data Processing Documentation 11.2 Journal Articles and Study Reports 11.3 Archive/DBMS Usage Documentation 12. RELATED DATA SETS 13. SUMMARY/SAMPLE 14. NOTES ENDOFTOC 1. TYPE OF DATA 1.1 Parameter/Measurement. The radiation budget of the Earth is described in terms of Earth and solar irradiance. For the Earth Radiation Budget (ERB) experiment on Nimbus-6 and 7, ten solar channels (labeled 1 through 10) measure incoming solar radiation. Four Earth- looking channels (11 through 14) with fixed wide angle fields of view (WFOV) measure radiation from the entire visible Earth disc. Eight Earth-looking scanning channels with narrow angle fields of view (NFOV) measure the angular dependence of Earth radiation. Four of these channels (15 through 18) measure short wavelength (reflected) radiation, while the other four (19 through 22) measure the long wavelength (emitted) radiation. Longwave flux, Earth albedo, and net radiation are derived separately from both the WFOV and NFOV measurements (for details see Item 3 below). 1.2 Unit of Measurement. Watts per meter squared (W/(m**2)) for solar constant, terrestrial flux, and net radiation; % for albedo. 1.3 Data Source. Earth Radiation Budget (ERB) instruments on the Nimbus-6 and 7 polar orbiting satellites. 1.4 Data Set Identification. The data product descriptions below and under Item 8 are chiefly based on Nimbus-7. In April 1980 a program was initiated to reprocess the ERB data from Nimbus-6 to be consistent with the Nimbus-7 data, but this program was not funded to completion. However, some level 3 Nimbus-6 wide-field-of-view results have recently become available. - Mapped Data Matrix Tape (MATRIX), Level III Contains daily, 6-day, and monthly world grids of data and contour map matrices for wide-field-of-view parameters. - ERB Matrix Summary Tape (EMST), Level III Contains monthly averaged world grid wide field of view data extracted from the monthly ERB MATRIX tapes. - ERB Total Solar Irradiances, Level II Approximately 13 years of daily mean total solar irradiances are available on floppy diskette in ASCII format. This data set is updated every three to six months. - ERB Solar Analysis Tape (ESAT), Level II Contains 89 months of ERB orbital and daily averaged solar irradiance measurements with preliminary calibration, as well as several solar activity indicators (including the Zurich relative sunspot number, the Ottawa 2800 MHz Solar Flux, and daily calcium plage index). This product has been discontinued. Identical solar irradiance and activity indicators are available in other data sets, rendering this product obsolete. (It does, however, show the calibration problems with the spectral channels.) - Subtarget Radiance Tape (STRT), Level II Contains radiance data located on the subtarget area grid and placed in angular bins defined by the satellite zenith angle at the subtarget area, the sun-satellite azimuth angle, and the solar zenith angle. - Subtarget Revised Radiance Tape (SRRT), Level II These data are identical to the STRT, but with improved cloud data. However, they cover a shorter time span (April 14, 1979 to February 19, 1980). - Enhanced Resolution WFOV Data Tape, Level II & III Contains 8 day and monthly averaged enhanced resolution world grid data for the period July 1, 1983 to July 1, 1984. - Enhanced Resolution outgoing longwave radiation (OLR), Level III Monthly spherical harmonic coefficients for the period July 1975 to October 1985 on floppy diskette. - NFOV Maximum Likelihood Cloud Estimation (MLCE) tape, Level III Contains daily and monthly averaged reprocessed scanner world grid data for the period May 1979 through May 1980. - NFOV Sorting into Angular Bins (SAB), Level III Contains daily zone and monthly target area scanner averages computed by angular integration for the period May 1979 through May 1980. - Original NFOV MATRIX Products, Level II and III Contains the original MATRIX daily and monthly world grid scanner products for the period November 16, 1978 through June 20, 1980. In the mean the albedo is 10% (3 albedo units) too high and the OLR three W/m**2 too low. 2. SPATIAL CHARACTERISTICS Spatial coverage and spatial resolution are functions of the products that are generated. The MATRIX tape products have two basic formats; the World Grid Format and the Map Format. The spatial coverage and spatial resolution are described below. Format Spatial Characteristics ============================================================================= World grid (W.G.) format: 2070 target areas, each approximately 500 km x 500 km. Latitude interval = 4.5 degrees; longitude interval varies from 4.5 degrees at the equator to 120 degrees at the poles. _____________________________________________________________________________ Map format: 1 Mercator and 2 polar stereographic maps. Mercator map: 32 degrees N - 32 degrees S latitude, 0-360 degrees longitude; Polar maps: Equator to pole, North and South; each polar map contains 65 x 65 grid elements. These are formed by inter-polating the world grid data fields. 3. TEMPORAL CHARACTERISTICS 3.1 Temporal Coverage. Coverage began with ERB-6 in July 1975 and continues with ERB-7, turned on 16 November 1978. The scanner mechanisms of both instruments have failed. Little ERB-6 data were recorded between May 1978 and March 2, 1981, when the instrument was turned off. The ERB-6 data are only partially available, though, since final processing has not been completed. Calibration of the wide-field- of-view Earth flux measurements from the ERB instrument on Nimbus-7 stopped on October 31, 1987. Both the solar and the Earth flux channels on ERB-7 are still operational, but only the channel 10C solar measurements are calibrated and released for scientific investigation. However, partially calibrated data from solar channels 1-9 and Earth flux channels 11-14 are available upon request from November 1987 onward. Two gaps exist for the angularly-dependent, terrestrial flux data (obtained from the scan channels). About six months of ERB-6 scan data exist, from July 1975 through January 1976, though the ERB-6 scanner data became noisy in September 1975 and the problem continued until scanning was stopped in January 1976. Then there are no data until November 16, 1978, when ERB-7 began operation. ERB-7 data continue through June 1980 (19 months of scan data). The second gap begins at that time and continues to the present. In addition, the scanner operation was limited for four months early in the Nimbus-7 mission, from December 10, 1978, to April 13, 1979. During this interval the scanner still operated, but on a reduced schedule, resulting in less scan data and in some gaps in the nighttime data over the Northern Hemisphere. For the ERB-6, no large gaps exist for the solar data from July 1975 to October 1978 or for the WFOV terrestrial flux data, from July 1975 to May 1978. The ERB-6 data are very sparse after June of 1978. For the ERB-7 no large gaps exist in the solar data from November 1978 to the present. The ERB-7 WFOV calibrated terrestrial flux also exists, from November 16, 1978 through October 1987 when the calibration was shutdown, but with a gap: April 10 - June 23, l986. The WFOV measurements are still being taken and archived. The duty cycle for operation of ERB-6 was about 60 percent for the first year and 100 percent thereafter. However, after May 1976, only about 65 percent of each orbit could be recorded due to tape recorder problems. After the scan mechanism failed, the narrow angle channels continued to take data from the nadir position. During the early years of operation the ERB-7 was subject to a 75 percent duty cycle of 3 days on and 1 day off. The period of scan-limited operation mentioned above did not affect this duty cycle. The ERB-7 instrument was still powered on 3 days of 4, but the scan mechanism operated only 2 of those 3 days. Normally the scanner operated on a 3 days on/1 day off cycle also. ERB-7 operated full-time for about six months from September 1983 to the spring of 1984 and again from November 1984 to the present. However, from April 10 through June 23, l986, it was on only 20 minutes per orbit to make solar measurements. Again from late April to late August 1987 the ERB instrument was on full time every other day. On the intervening days it was on for about 30 minutes each orbit for solar measurements. 3.2 Temporal Resolution. The temporal resolution for the ERB Earth Flux products is shown in the following tables, where headings such as daily, 6-day, monthly, and seasonal indicate the averaging interval. WFOV Data Products on MATRIX ____________________________________________________________________ Channels Daily 6-day Month W.G. Products from WFOV Used W. G. Map & Map ==================================================================== LW terrestrial flux o day 12-13 X X o night 12 X X o day plus night 12-13 X X ____________________________________________________________________ Earth albedo o (0.2-4.0 micrometers) 13 X X o (0.7-3.0 micrometers) 14 X X o (0.2-0.7 micrometers) 13,14 X X ____________________________________________________________________ Net radiation 12,13 X X X ____________________________________________________________________ Data population for WFOV observations o day X X o night X X o day plus night X X ____________________________________________________________________ Note: The EMST contains only the MATRIX monthly world grid products. The one year enhanced resolution tape contains both eight day and monthly world grid products. The ten year Enhanced Resolution Outgoing Longwave Radiation diskette contains only monthly spherical harmonic coefficients. A constant solar luminosity was assumed. The total and near infrared values used were taken from early channel 5 and 10c measurements. NFOV Data Products, Original and MLE reprocessed _____________________________________________________________________ Channels Daily Month Products from NFOV Used W. G. W.G. ===================================================================== Long Wavelength (LW) terrestrial flux o day 19-22 X X o night X X o day plus night X X _____________________________________________________________________ Earth albedo o average 15,16,17,18 X X o minimum X _____________________________________________________________________ Net radiation 15-22 X X _____________________________________________________________________ Data population for NFOV observations o day X X o night X X o day plus night X _____________________________________________________________________ Note: The reprocessed MLE has both mean and separate clear sky products. The reprocessed Sorting into Angular Bins (SAB) has daily zonal and monthly zonal and world grid products. Channel 18 became noisy in December of 1978 and was not used after that period. 4. INSTRUMENT DESCRIPTION 4.1 Principles of Operation. The Earth Radiation Budget (ERB) experiment is designed to provide highly accurate (1 percent or better) radiation measurements of the Sun and Earth from which the terrestrial radiation budget can be determined on both synoptic and planetary scales. A special goal of the experiment is to provide data related to the angular distribution of Earth albedo. For solar measurements each of the 10 channels is an independent, individually replaceable modular element with a mated amplifier. The sensors are advanced versions of the Eppley-JPL thermopiles. There are no imaging optics, only filters, windows and apertures. Earth emitted infrared radiation, and Earth reflected solar radiation are measured with fixed, wide angle field-of-view sensors. The wideband channels (11 and 12) employ a type N3 thermopile with circular receivers. Channel 13 is similar to a precision pyranometer. Channel 14 has a broadband filter hemisphere to match the band of channel 5. The eight scanning channels are mounted in a cylindrical head which is gimbal mounted on the mainframe of the radiometer unit. The gimbal arrangement allows the pointing direction of the scan head to be varied within a vertical plane by rotation of the scan head, and within a horizontal plane by rotation of the gimbal. With this arrangement the same portion of Earth can be viewed from different directions, thus providing data for modeling the angular distribution of the Earth albedo. 4.2 Instrument Measurement Geometry. The viewing geometry varies with the type of channel. For the wide field-of-view channels, the four sensors have unencumbered fields of 121 degrees and maximum fields of 133.3 degrees. From the orbital altitude of 955 km for Nimbus-7, the Earth subtends an angle of 120.8 degrees, corresponding to a circle of 29.6 degrees radius on the Earth. For Nimbus-6 which had an orbital altitude of 1100 km, the Earth subtends an angle of 120.2 degrees corresponding to a circle of 29.9 degree radius on the Earth. Channel 12 has an insertable stop so that, upon command, it can view slightly less than the entire Earth surface. The geographic coordinates of the center of the field-of-view are stored as the location of the measurement. For the scanning channels, the cylindrical head contains the four telescopes aligned such that the telescope center lines are 12 degrees apart when projected onto the horizontal plane. The fields-of-view (FOVs) of the four telescopes are rectangular (0.25 x 5.12 degrees). The FOVs of the short wavelength channels (15-18) are coincident, respectively, with those of the long wavelength channels (19-22) (one telescope contains 1 shortwave and 1 longwave channel). The telescope scan head can be scanned fore and aft and to each side of the subsatellite track. The onboard data system is preset to automatically integrate FOV measurements, depending on the nadir angle, so that the effective mean Earth footprint is close to a square at all nadir angles. The number of measurements integrated to obtained this square footprint varies from twenty at nadir to one near the limb. Five scan patterns are available, the difference between modes being the sequence and number of directions taken by the scan head. The scan modes are commanded by the operations center and selected by the sensor scientist. 5.1 Processing Steps and Data Sets. Processing for radiation budget parameters begins with the Level I ERB Master Archive Tape (MAT) and the cloud statistics products. The cloud statistics are on the new cloud ERB (NCLE) tapes. The older cloud ERB (CLE) tapes are obsolete and are no longer available. From these tapes, NOAA prepared a special analysis for studies of the angular distribution of Earth albedo, designated the Subtarget Radiance Tape (STRT). The climate parameters listed in Item 3 are calculated from the MAT tapes as indicated in the table entries of Item 3, and organized on the appropriate world grids (WG) or polar stereographic or Mercator projections, as daily, 6-day, monthly, and seasonal (three-month) averages. They are written on the Mapped Data Matrix Tape (MATRIX). 5.2 Derivation Techniques/Algorithms. As a matter of convenience in data handling, Earth regional averages are given for the "ERB World Grid" which divides the Earth into 2070 approximately equal area grids (500 km x 500 km), and each grid into nine subtarget areas each approximately 160 km x 160 km in size. The following Earth Radiation Budget products (MATRIX, EMST, Original NFOV, and Reprocessed Sorting into Angular Bins NFOV) utilize only the 2070 target area grid. The subtarget areas are used only by the STRT and reprocessed MLE tapes. Because of the sun-synchronous orbits of Nimbus-6 and 7, the radiation budget parameters derived from measurements made by the ERB instrument contain a diurnal bias, for which approximate corrections have been applied, in the WFOV and NFOV time and space averaged data products. The follow-on experiment (ERBE) is designed to better define this bias, providing a correction which could be applied to ERB MATRIX data. In the mean this correction is less than 1%. However, the WFOV sensors produce a regional smoothing which can amount to several percent for many target areas. Thus, care should be taken in comparing WFOV and NFOV results. 5.3 Special Corrections/Adjustments. The calibration of the solar channels is preliminary on the ERB MAT and SEFDT products. The final calibration, Earth-Sun distance and off-axis sun position corrections are made for channel 10C (total solar irradiance) on the Nimbus-7 Total Solar Irradiance diskette. For channels 1-9 only the preliminary results are available on the SEFDT and ESAT. 5.4 Processing Changes. A study is being conducted to assure that the data sets from ERB-6 and ERB-7 data are homogeneous and compatible. In addition, the Nimbus-7 total solar irradiances have been revised using a new algorithm which sharply reduces noise in the data. 6. QUALITY ASSESSMENT 6.1 Data Validation by Producer. Data validity is critically dependent on instrument stability and the prelaunch calibration. Rocket launches have been conducted to provide comparative "solar constant" data. Intercomparisons have also been made with other satellite total solar irradiance measurements from the Solar Maximum Mission satellite, the Upper Atmosphere Research Satellite (UARS) and the three ERBE satellites (ERBS, NOAA-9 and NOAA-10). A quality checking program will be maintained by the ERB processing team, subject to available resources. 6.2 Confidence Level/Accuracy Judgment. The design goal for the Earth radiation budget products is 1 percent accuracy. The NFOV calibration was maintained to the level. In the mean the WFOV calibration appears stable to about 0.5% as do the WFOV Earth Flux products. The limited diurnal sampling is a major problem. This is chiefly a regional problem. Thus, local longwave errors up to 1 or 2% and shortwave errors up to 4 or 5% can occur in the regional monthly means. These regional errors vary in size; thus, the global monthly means appear stable to 0.5% or better in the longwave and better than 1.5% in the shortwave. However, mean discontinuities of 0.5% or more can occur in going from one product to another. Recall that the WFOV sensors give a smoothed result. Thus regional discontinuities of several percent can occur between NFOV, WFOV MATRIX and the Enhanced Resolution WFOV products. The performance of the Nimbus-7 total solar irradiance channel 10C is limited by the analog-to- digital converter to + or - 0.5 counts. The uncertainty due to this limitation is 0.35 W/(m**2) or about + or - 0.03 percent of the signal during the solar measurement for individual measurements. The channel is quite stable and the accuracy of its relative measurements may be governed by the digitization cut off. The absolute accuracy of the 10c measurements is about 0.5 percent. 6.3 Usage Guidance. The majority of the ERB radiation budget parameters are climate parameters which can be used to define Regional Net Radiation Components and the Equator-Pole Gradient for NASA Climate Program planning. The daily solar irradiance data will contribute to the determination of the solar constant. In concept, there is a continuous data set since July 1975. However, the accurate total solar irradiance data starts on November 16, 1978. Limitations exist, however, as to the availability and coverage of these data. For example, since the Nimbus-6 launch in 6/75, the ERB parameter extraction and data set preparation programs have undergone considerable modification. Hence, reprocessing of all past ERB-6 data through the latest versions of the algorithms is not yet complete. Furthermore, the ERB-6 NFOV scanning data will probably remain limited to just the July-August 1975 period. For ERB-7, the narrow angle data are available only between November 1979 and June 1980, with the best data for the period May 1979 through May 1980. 7. CONTACTS FOR DATA PRODUCTION INFORMATION 7.1 Nimbus Experiment Team Chairman Dr. H. Lee Kyle Code 936 Goddard Space Flight Center Greenbelt, MD 20771 (301) 286-9514 7.2 Senior Scientist Dr. H. Jacobowitz NOAA/NESDIS Atmospheric Sciences Branch World Weather Building, Room 711 5200 Auth Road Camp Spring, MD 20746 (301) 763-8053 7.3 Experimental Products (background on STRT and angular distribution models) Dr. L. L. Stowe NOAA/NESDIS Atmospheric Sciences Branch World Weather Building, Room 711 5200 Auth Road Camp Spring, MD 20746 (301) 763-8053 8. OUTPUT PRODUCTS AND AVAILABILITY 8.1 Tape Products 8.1.1 Mapped Data Matrix Tape (MATRIX), Level III Medium/Specification: 9-track, 1600-bpi computer tape; Nimbus Spec. No. T134031, Revision M, dated February 1985. However, now six MATRIX tapes (6 months) are stacked on one 9-track 6250-bpi computer tape. Format and Content: The MATRIX tapes contain regional earth radiation budget products at the top of the atmosphere. Included are emitted longwave, albedo, and net radiation calculations on a daily, six day, and monthly basis. Only WFOV products are presented. The earth is divided into 2070 fixed target areas, each approximately 500 x 500 km, and results are given for each target area viewed during a specific period. Sampling population and other statistics are given, as well as day, night, and average results. Each tape is generated by an IBM 3081 computer program. It contains a standard header record written twice as the first file. There are up to 14 data files numbered 2 through 15 which contain either daily world grid data or 6-day averaged data in the form of Mercator/polar map matrices, plus a data file that contains monthly averages in the world grid format and also as Mercator and polar stereographic projections. All data records contain 117,792 bits (14,724 bytes) of information. The data files are followed by a file which contains a monthly calibration table (CAT). The last file may be a trailer documentation file defining all inputs for producing the tape. Of the 28 ERB parameters calculated, 18 are included as daily world grid matrices. Monthly averages for all 28 ERB parameters appear in the next to last data file. The daily files contain only world grid formatted data. The six-day files contain only Mercator/polar map matrices, and the monthly averages file contains both types of data. All file assignments described above are based on full time operation of the ERB instrument. For those 6-day cyclic periods in which the ERB instrument is off, the total number of files on the tape will be reduced by two, but the record/file arrangement remains the same. The NFOV records contain fill values following the scanner failure. The Post-MAT Calibration Level I tapes (called DELMATs), which contain short-term calibration adjustment quantities, are used for the wide field-of-view calibrations in the MATRIX product. Data Quantity/Rate: There are 12 MATRIX tapes/year or two stacked tapes/year. One DELMAT tape/month. Status: Nine years of MATRIX and DELMAT data are available at the archive. All data use an improved algorithm. Plans/Schedule: MATRIX tapes were produced for the first nine data years which ended in October of 1987. Measurements have continued and these may be calibrated and processed in the future. 8.1.2 ERB MATRIX Summary Tape (EMST), Level III Medium/Specification: 9-track, 6250-bpi computer tape; User's Guide and Tape Specification for the Nimbus-7 ERB MATRIX Summary Tape (EMST), Revised July 1991. Format and Content: The EMST contains monthly averaged world grid data extracted from the monthly ERB MATRIX tapes. The EMST tapes are generated by an IBM 3081 computer program. They consist of one standard header file and data files. The standard header file consists of two header records written in EBCDIC, using odd parity. The data files, which start from the second file, contain the monthly averaged world grid data for ERB MATRIX parameters. Each data file consists of one month's worth of data. The number of the MATRIX parameters contained in one data file is 28. Data Quantity/Rate: One tape for November 1978 through October 1987. Status: The WFOV products on this tape were prepared using an improved algorithm known at the Global Calibration Adjustment Table (CAT). 8.1.3 The Maximum Likelihood Cloud Estimation (MLCE) Tape, Level III. Medium/Specification: 9-track, 6250-bpi computer tape. User's Guide: Nimbus-7 Earth Radiation Budget Narrow-Field-of-View Products, NASA Reference Publication 1246, November 1990. Format and Content: The MLCE contains Nimbus-7 ERB narrow-field- of-view regional Earth radiation budget products at the top of the atmosphere. Included are both mean and clear sky only values for the emitted longwave, albedo and net radiation on a daily and monthly basis. The cloud cover for each observation is estimated to be either clear (0-5%), partly cloudy (5-50%), mostly cloudy (50-95%) or overcast (95-100%). The percentage of observations in each cloud cover category are listed. Daily and monthly averages are given on fixed 2070 target area (TA) world grid, each TA approximately 500 km X 500 km. Further, each TA is subdivided into nine equal subtarget areas (STA). At the equator each STA is 1.5% latitude by 1.5% longitude. Sampling populations and other statistics are given as well as day, night and average results. Up to three months of data are on each tape. The first file on each tape contains two standard NOPS header records. This is followed by the data files, one for each ERB-ON day of the month, plus an additional monthly average file. This sequence of data files is repeated for the remaining months of data contained on the tape. The manner in which the various parameters are sorted in the data files is given in the tape specifications. Data Quantity/Rate: There is one tape for every three months, but one tape contains only May 1980. Status: Thirteen months (May 1979 - May 1980) are available. The data were processed by the Maximum Likelihood Cloud Estimation parameters. Plans/Schedule: The Nimbus-7 ERB Scanner became defective on June 20, 1980. Processing has stopped. 8.1.4 The Sorting into Angular Bins (SAB). Level III. Medium/Specification: 9-track, 6250-bpi computer tape. User's Guide: Nimbus-7 Earth Radiation Budget Narrow-Field-of-View Products, NASA Reference Publication 1246, November 1990. Format and Content: Albedo, OLR and net radiation are given. In addition, reflectances and OLR radiances are given for each of 49 angular bins covering half of the observing hemisphere. Symmetry is assumed about the principle reflection plane of the scene. Daily statistics are given for 4.5 degree latitude bands, with no data near the poles. Monthly quantities are given on a target basis. Data Quantity/Rate: One 6250-bpi tape. Status: The tape is available. Plans/Schedule: No additional data expected. 8.1.5 ERB Solar Analysis Tape (ESAT), Level II Medium/Specification: 9-track, 1600-bpi computer tape Format and Content: The ESAT contains 89 months of ERB calibrated orbital and daily averaged solar irradiance measurements. For the same time period it also contains several solar activity indicators. These include the Zurich relative sunspot number, the Ottawa 2800 Mhz Solar Flux, and the daily calcium plage index. The tape consists of five files. Data Quantity/Rate: One 1600-bpi tape. Status: The tape is available through NSSDC. Plans/Schedule: This product is obsolete and is in the process of being replaced. See section 8.3.1 and 8.3.2 for correct total solar irradiances. 8.1.6 Subtarget Radiance Tape (ERB-STRT), Level II Medium/Specification: 9-track, 6250-bpi computer tape. Format and Content: The ERB STRT tapes were generated at NOAA for use in developing angular dependence models of reflection and emission. ERB scanning channel radiances and associated information are sorted into the 2070 target areas (TA). Each area is further divided into a 3 x 3 array of subtarget areas (STA), 160 km x 160 km. Within each STA the satellite-derived information is grouped by orbit and sorted by time and viewing angle. This data product is considered partially obsolete because of the low quality of the cloud identification procedure used. Improved cloud estimates appear in the shorter Subtarget Revised Radiance Tape (SRRT), described in section 8.1.7. The SRRTs are recommended for most studies. The data for each day are contained on the tape in the following types of logical records: 1. topography records - 1 per Target Area (TA) 2. geography records - 1 per Subtarget Area (STA) 3. observation records - 1 per STA per orbit All records have information to identify TA and STA location, date and time of observation. The topography record consists of climatological information for each TA. It specifies the fraction of the TA containing: 1) water and permanent ice for each of the four seasons; 2) six other surface configurations - plains, hilly uplands and plateaus, mountains, and deserts of the hamada, erg, and mountain and bolson types; 3) nine vegetation classifications - mountains, forests of the selva, scrub, taiga, and mixed mid-latitude types, grasslands of the savanna and prairie (steppe) types, tundra, and desert. Each geography record contains the fraction of land, water, snow and ice present in a STA within 24 hours of the ERB measurements. Also, the average depth (mm) of the snow and average age (days) of the snow and ice are given. The topography and geography records both consist of ancillary data obtained from non-ERB sources, specifically P.E. James' "A Geography of Man" and the U.S. Air Force snow and ice data tape. Each observation record contains all the radiances observed in a STA during one orbital pass of the satellite. Each radiance is assigned a bin number corresponding to satellite zenith angle and azimuth angle relative to the sun (the upward facing hemisphere is divided into 389 discrete bins each about 6 degrees in zenith and 15 degrees in azimuth angle). Included is the fraction (in ninths) of the field-of-view located in the STA, the number of the channel from which the radiance value is derived, and computed minimum, mean and maximum solar zenith angle. Estimates of the amount and type of low, middle and high clouds covering each STA (obtained from the CLE (THIR)) within ten minutes of the ERB radiance observations are provided. This process is described in the detailed catalog for the NCDS data set "N7-THIR". The CLE cloud estimates are now considered obsolete, particularly for clear and low cloud estimates. A file was marked on the tape when all 2070 TAs were processed for one day. Generally nine files can be found on one tape. Data Quantity/Rate: There was one 6250-bpi tape for every 6-day period. There was a potential of 388 data days (11/16/78 to 6/22/80), but only 272 data days were included in the first archive data set which covered slightly more than one year of data. These data (203 days from April 1, 1979) have been reprocessed with an improved cloud algorithm. See section 8.1.7 below for a description of this product. It is hoped that the 118 remaining days of scanner data will be processed when funds are available. Status: 47 tapes are available from NSSDC. Plans/Schedule: This product is complete. Any further work will be archived on the SRRT data set described below. 8.1.7 Subtarget Revised Radiance Tape (ERB-SRRT), Level II. Medium/Specification: 9-track, 6250-bpi magnetic tape. Format and Content: This product is an improved version of the STRTs (Section 8.1.6) which use the New Cloud ERB (NCLE) estimates described by Stowe et. al. (1988). The tape arrangement is similar to the STRT but includes additional cloud information. Included are the average THIR 11.5 micron radiances associated with high, medium and low altitude clouds plus clear scene radiances. The STRT tapes contain 272 data days spanning over one year. The NCLE cloud data set starts in April, 1979. The NCLE were used to modify 203 of the STRT product days for the time span April 14, 1979 through February 19, 1980. Data Quantity/Rate: There is one 6250-bpi tape for every six or seven data days except the last two tapes which contain five and two data days respectively. Status: 33 tapes are available from NSSDC. Plans/Schedule: More data days may be included in the data set when funds are available. 8.2 Film Products None. 8.3 Other Products 8.3.1 Nimbus-7 ERB Daily Averaged Total Solar Irradiance Measurements, Level II on floppy diskette. Medium/Specification: IBM-compatible floppy diskette. Format and Content: Data are measurements from the ERB channel 10C. The diskette contains two files in ASCII format: Each record in S0.DAT contains the date, the number of orbits for which good observations are available, the daily mean solar irradiance value, and standard deviation of the irradiance value. The final calibration for the solar channel 10C data is done separately from the MAT and SEFDT data. MNMEANS.DAT contains monthly means derived from the daily means described above. In addition, the SMM/ACRIM monthly means are given, along with the differences between the measurements and the monthly mean Wolf sunspot numbers. Data Quantity/Rate: One 500 Kbyte floppy diskette. Status: Available from NSSDC. Plans/Schedule: The diskette is redistributed periodically as new data become available. 8.3.2 Nimbus-7 ERB Daily Averaged Total Solar Irradiance Measurements in Common Data Format, Level II. Medium/Specification: On line data file in NSSDC's Common Data Format (CDF). This format is used to store all data sets supported by the NASA Climate Data System (NCDS) and contains all descriptive elements necessary for listing or plotting. Data coverage is from November 16, 1978 to October 31, 1991. Format and Content: Data are measurements from the ERB channel 10C. Each record contains the mission day and irradiance value. The final calibration for the solar channel 10C data is done separately from the MAT and SEFDT data. Data Quantity/Rate: Data file is 124 512-byte blocks in volume. Status: Available through the NCDS system. Contact the NCDS User Support Office for access information. Plans/Schedule: Data will be updated periodically as new data become available. 9. DATA ACCESS 9.1 Archive Identification Code 933-Central Data Services Facility National Space Science Data Center Goddard Space Flight Center Greenbelt, MD 20771 (301) 286-6695 9.2 Procedures for Obtaining Data. Prospective users should request a copy of "NSSDC and WDC-A-R&S Document Availability and Distribution Services," April 1986. Researchers who reside outside the USA should direct their requests to: World Data Center-A for Rockets and Satellites Code 930.2 Goddard Space Flight Center Greenbelt, MD 20771 USA (301) 286-6695 Users may submit requests for data by letter, telephone, personal visit, or through the NASA Science Internet (NSI_net) computer network at NSSDCA::REQUEST. Data costs are dependent on affiliation and sponsorship of the user program. Data are free to NASA personnel. Communication with the NSSDC Request Coordination Office is advised before ordering. The NASA Climate Data System supports this data set through its online data system. Several software tools are available to extract and analyze supported data. Access through NCDS requires an account on the NSSDC computer system. Contact the NCDS User Support Office for information and instructions. 9.3 NCDS Status/Plans. NCDS provides access to the ERB-MATRIX, ERB- Matrix Summary Tape (EMST), and Level II ERB Channel 10C solar irradiance data sets through its online data system. Contact the NCDS User Support Office for information on the status of these products. 10. CONTACTS FOR ARCHIVE/DATA ACCESS INFORMATION Request Coordination Office National Space Science Data Center Code 933-Central Data Services Facility NASA/Goddard Space Flight Center Greenbelt, MD 20771 PHONE: (301) 286-6695 NSI_net: NSSDCA::REQUEST Internet: REQUEST@128.183.36.23 NASA Climate Data System User Support Office Code 934-NASA Goddard Space Flight Center Greenbelt, MD 20771 PHONE: (301) 286-3209 NSI_net: NSSDCA::NCDSUSO Internet: NCDSUSO@128.183.36.23 11. REFERENCES 11.1 Satellite/Instrument/Data Processing Documentation a. GSFC, 1975. The Nimbus-6 User's Guide. NASA/GSFC, Greenbelt, Maryland. b. GSFC, 1978. The Nimbus-7 User's Guide. NASA/GSFC, Greenbelt, Maryland. c. Hurley, E.J., and R. Jones, December 1983. Nimbus-7: Observing the Atmosphere and Oceans. NASA/GSFC, Greenbelt, Maryland. d. Kyle, H.L., R.R. Hucek, B. Groveman, and R. Frey, 1990. Nimbus-7 Earth Radiation Budget Narrow-Field-of-View Products, NASA RP-1246, 76 pages. e. Oakes, A.G., D. Han, H.L. Kyle, G.C Feldman, A.J. Fleig, E.J. Hurley, and B.A. Kaufman, 1989. Nimbus-7 Data Product Summary, NASA Reference Publication 1215, 106 pages. 11.2 Journal Articles and Study Reports a. Ardanuy, P. E., H.L. Kyle, and D. Hoyt, 1992. "Global Relationships Between the Earth's Radiation Budget, Cloudiness, Volcanic Aerosols, and Surface Temperature," Journal of Climate, (in press). b. Ardanuy, P. E., L.L. Stowe, A. Gruber, and M. Weiss, 1991. "Shortwave, Longwave, and Net Cloud Radiative Forcing as Determined From Nimbus-7 Observations," Journal of Geophysical Research, 96:18537-18549. c. Ardanuy, P. E., C.R. Kondragunta, and H.L. Kyle, 1990. "Low- Frequency Modes of the Tropical Radiation Budget," J. Meteor. and Atmos. Research, 44:167-194. d. Ardanuy, P. E., H.L. Kyle, R.R. Hucek. and B.S. Groveman, 1987. "Nimbus-7 Earth Radiation Budget Wide Field of View Climate Data Set Improvement, Part II: Deconvolution of the Earth Radiation Budget Products and Consideration of the 1982-1983 El Nino Event," J. Geophys. Research. 92(4), pp. 4125-4143. e. Ardanuy, P.E. and H.L. Kyle, 1986. "Observed Perturbations of the Earth's Radiation Budget: A Response to the El Chichon Stratospheric Aerosol Layer?" Journal of Climate and Appl. Meteorol., 25:505-516. f. Arking, A., 1991. "The Radiative Effects of Clouds and Their Impact on Climate," Bull. Amer. Meteorol. Soc., 72:795-813. g. Barker, H. W. and J. A. Davies, 1989. "Surface Albedo Estimates from Nimbus-7 ERB Data and A Two-Stream Approximation of the Radiative Transfer Equation," J. of Climate, 2:409-418. h. Bess, T. D., G. L. Smith and T. Charlock, 1989. "A Ten-Year Monthly Data Set of Outgoing Longwave Radiation from Nimbus-6 and Nimbus-7 Satellites," Bulletin of the American Meteorological Society, 70:480-489. i. Cess, R.D.. 1990. "Interpretation of an 8-Year record of Nimbus-7 Wide-Field-of-View Infrared Measurements," J. Geophys. Res., 95:16653-16657. j. Cess, R. D. and I. L. Vulis, 1989. "Intercomparison and Interpretation of Satellite-Derived Directional Albedos Over Deserts," J. of Climate, 2:393-407. k. Charlock, T.P., F.G. Rose, T.D. Bess, and G.L. Smith, 1990. "The Relationship of Extratropical Outgoing Longwave Radiation to Monthly Geopotential Teleconnection Patterns," J. Climate, 3:1390-1399. l. Chen, L., R.E. Reiter, and Z. Feng, 1985. "The Atmospheric Heat Source Over the Tibetan Plateau May-August 1979," Mon. Wea. Rev., 113:1771-1790. m. Chertock, B., R. Frouin, and R.C.J. Somerville, 1991. "Global Monitoring of Net Solar Irradiance at the Ocean Surface: Climatological Variability and the 1982-1983 El Nino," J. Climate, 4:639-650. n. Dhuria, H.L., and H.L. Kyle, 1990. "Cloud Types and the Tropical Earth Radiation Budget," Journal of Climate, 3:1409-1434. o. Foukal, P., and J. Lean, 1988. "Magnetic Modulation of Solar Luminosity by Photospheric Activity," Astrophys. J., 328: 347-357. p. Harshvardhan, Mr., D. A. Randall, T. G. Corsetti, D. A. Dazlich, 1989. "Earth Radiation Budget and Cloudiness Simulations with A General Circulation Model," J. of the Atmospheric Sciences, 46:1922-1942. q. Hartmann, D.L. and E.E. Recker, 1986. "On the Diurnal Variations of Outgoing Longwave Radiation in the Tropics," J. Climate App. Meteor., 25:800-812. r. Hartmann, D.L., V. Ramanathan, A. Berroir, and G.E. Hunt, May 1986. "Earth Radiation Budget Data and Climate Research," Rev. Geophys. Space Phys., 24:439-468. s. House, F.B., A. Gruber, G.E. Hunt, and A.T. Mecherikunnel, 1986. "History of Satellite Missions and Measurements of the Earth Radiation Budget (1957-1984)," Rev. Geophys. Space Res., 24:357-377. t. Hoyt, V.D., H.L. Kyle, J.R. Hickey, and R.H Maschloff, 1992. "The Nimbus-7 Total Solar Irradiance: A New Algorithm for its Derivation," Journal of Geophysical Research, 97:51-63. u. Jacobowitz, H., H.V. Soule, H.L. Kyle, F.B. House, and the Nimbus-7 Experiment Team, June 30, 1984. "The Earth Radiation Budget Experiment: An Overview", J. of Geophys. Res. 89:5021-5038. v. Kondrat'ev, I. Ia., V. V. Kozoderov, S. Kh. Keevallik and O. Iu. Kiarner, 1988. "Determination of Clear-Sky Planetary Albedo," Issledovanie Zemli iz Kosmosa, September-October 1988, 44-49 (in Russian). w. Kyle, H.L., P.E. Ardanuy, and E.J. Hurley, 1985. "The Status of the Nimbus-7 ERB Earth Radiation Budget Data Set," Bull. Amer. Meteor. Soc., 66:1378-1388. x. Kyle, H.L., K.L. Vasanth, and the Nimbus-7 ERB Experiment Team, 1986. "Some Characteristic Differences in the Earth's Radiation Budget Over Land and Ocean Derived from the Nimbus-7 ERB Experiment", J. Climate Appl. Meteor., 25:958- 981. y. Kyle, H.L., A. Mecherikunnel, P. Ardanuy, L. Penn, B. Groveman, G. Campbell, and T.H. Vondar Haar, 1990. "A Comparison of Two Major Earth Radiation Budget Data Sets," Journal of Geophysical Research, 95:9951-9970. z. Marchuk, G. I., K. Ia. Kondrat'ev and V. V. Kozoderov, 1989 "Analysis of Observational Data on the Earth's Radiation Budget," Issledovanie Zemli iz Kosmosa, January-February 1989, 3-16 (in Russian). aa. Mecherikunnel, A.T., R.E. Lee, H.L. Kyle, and E.R. Major, 1988. "Intercomparison of Solar Total Irradiance Data From Recent Spacecraft Measurements," J. Geophys. Res., 93:9503-9509. bb. Ohring, G., A. Gruber, and R. Ellingson, 1984. "Satellite Determinations of the Relationship Between Total Longwave Radiation Flux and Infrared Window Radiance," J. Climate Appl. Meteor., 23:416-425. cc. Slingo, A., R.C. Wilderspin and R.N.B. Smith, 1989. "Effect of Improved Physical Parameterization on Simulations of Cloudiness and the Earth's Radiation Budget," J. of Geophys. Res., 94: 2281-2301. dd. Smith, E.A., and Byung-Ju Sohn, 1990. "Surface Forcing of Interannual Variations in the Radiation Balance Over North Africa, Part I: Partitioning the Surface and Cloud Forcing," Climate Change, 17:147-192. ee. Smith, E.A., and M.R Smith, 1987. "Interannual Variability of the Tropical Radiation Balance and the Role of Extended Cloud Systems," J. Atmos. Sci., 44:3210-3234. ff. Smith, G.L., D. Rutan, T.P. Charlock, and T.D. Bess, 1990. "Annual and Interannual Variations of Absorbed Solar Radiation Based on a 10-Year Data Set," J. Geopys. Res., 95:16639-16652. gg. Stowe, L.L., C.G. Wellemeyer, T.F. Eck, H.Y.M. Yeh, and the Nimbus-7 Cloud Data Processing Team, 1988. "Nimbus-7 Global Cloud Climatology, Part I: Algorithms and Validation," J. Climate, 1:445-470. hh. Stowe, L.L., H.Y.M. Yeh, T.F. Eck, C.G. Wellemeyer, H.L. Kyle, and The Nimbus-7 Cloud Data Processing Team, 1989. "Nimbus-7 Global Cloud Climatology, Part II: First Year Results," J. of Climate, 2:671-709. ii. Taylor, V.R., and L.L. Stowe, June 30, 1984. "Reflectance Characteristics of Uniform Earth and Cloud Surfaces Derived from Nimbus-7 ERB," J. of Geophys. Res. 89:4987-4996. 11.3 Archive/DBMS Usage Documentation a. Kyle, H.L., 1990. "The Nimbus-7 Earth Radiation Budget (ERB) Data Set and its Uses," An article in Long-Term Monitoring of the Earth's Radiation Budget, B.R. Barkstrom, editor. Symposium at Orlando, Florida, April 17-18, 1990., Proc. SPIE, 1299, 27-39. b. Kyle, H. Lee, R. Hucek, B. Groveman and R. Frey, November 1990. Nimbus-7 Earth Radiation Budget Narrow-Field-of-View Products. NASA Reference Publication 1246. c. Kyle, H. Lee and Hyo Duck Chang, 1986. User's Guide and Tape Specifications for the Nimbus-7 ERB Matrix Summary Tape (EMST). NASA/GSFC, Greenbelt, Md. d. Ng, C.Y., and Y.P. Sheu (editors), July 1985. "Descriptions of Meteorological and Terrestrial Applications Spacecraft and Investigations." Data Catalog Series for Space Science and Applications Flight Missions 4A. NSSDC/WDC-A-R&S 85-03. NASA/GSFC, Greenbelt, Maryland. e. NSSDC, April 1986. "NSSDC and WDC-A-R&S Document Availability and Distribution Services." f. Olsen, L.M., J.W. Closs, J.R. Vanderpool, November, 1991. "NASA's Climate Data System Primer: Version 1.2." National Space Science Data Center, NASA Goddard Space Flight Center, Greenbelt, Maryland. g. Stowe, L.L. and M.D. Fromm, December 1983. Nimbus-7 ERB Sub-target Radiance Tape (STRT) Data Base. NOAA Technical Memorandum NESDIS 3. NOAA/NESDIS, Washington, D.C. 12. RELATED DATA SETS The Earth Radiation Budget Experiment (ERBE) compiled from the ERBS, NOAA-9 and NOAA-10 spacecraft contains similar parameters. Continuity between the ERBE and Nimbus products is planned using the 1984-87 time period. Refer to the data set descriptions for the ERBE products in the NASA Climate Data System for additional information. 13. SUMMARY/SAMPLE A limited number of sample online data files and graphic plots are available through the NASA Climate Data System. 14. NOTES None. *92/03/06