Lower Tropospheric Temperature Anomalies from MSU 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 2.1 Spatial Coverage 2.2 Spatial Resolution 3. TEMPORAL CHARACTERISTICS 3.1 Temporal Coverage 3.2 Temporal Resolution 4. INSTRUMENT DESCRIPTION 4.1 Mission Objectives 4.2 Key Satellite Flight Parameters 4.3 Principles of Operation 4.4 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. Retrieved brightness temperature anomalies for the lower-to-mid troposphere (approximately surface to 400 mb), and the annual cycle for 1982-90, about which these anomalies were computed. 1.2 Unit of Measurement. Hundreths of degree C (.01 deg C). 1.3 Data Source. The Microwave Sounding Unit aboard the TIROS-N series of NOAA polar orbiting satellites (TIROS-N, NOAA- 6, -7, -9, -10, -11, and -12). 1.4 Data Set Identification. The "Lower Tropospheric Temperature Anomalies from MSU" data set consists of calibrated MSU channel 2 brightness temperatures along individual MSU scan lines. These are combined in a simple multi-angular linear retrieval on MSU channel 2 to produce new brightness temperatures representing a weighting function peaking near 700 mb and having very little influence from above 300 mb. This weighting function describes the vertical sensitivity to thermal emission by molecular oxygen in the atmosphere and is very closely related to the thermometric temperature for that layer. The MSU temperature data set resides within NCDS as MSUTMP_MONTHLY and MSUTMP_CLIMATOLOGY. 2. SPATIAL CHARACTERISTICS 2.1 Spatial Coverage. Global coverage. 2.2 Spatial Resolution. Original spatial resolution of the instrument footprint ranges from 120 km to over 200 km, but the retrieval procedure requires a total of eight of these measurements, which span a 2000 km swath, to produce a single retrieval temperature. Therefore, the original retrieval resolution is approximately 200 km north-south by 2000 km east-west near the equator, tilting to 200 km east-west by 2000 km north-south near the poles. The vertical resolution is approximately from the surface to 400 mb, with peak weighting near 700 mb. The resolution of the data set is a 2.5 x 2.5 degree latitude-longitude grid. 3. TEMPORAL CHARACTERISTICS 3.1 Temporal Coverage. January 1979 - December 1991. At some times two satellites were operating, while at other times only one satellite was operating. 3.2 Temporal Resolution. Monthly. 4. INSTRUMENT DESCRIPTION 4.1 Mission Objectives. TOVS sounding instruments, consisting of HIRS/2, Microwave Sounding Unit (MSU), and Stratospheric Sounding Unit (SSU), are designed to provide global coverage of atmospheric temperature and moisture profiles. 4.2 Key Satellite Flight Parameters. Nominal orbit parameters for the TIROS-N/NOAA series satellites are: o Launch date TIROS-N: October 13, 1978 NOAA-6: June 27, 1979 NOAA-7: June 23, 1981 NOAA-8: March 28, 1983 NOAA-9: December 12, 1984 NOAA-10: September 17, 1986 NOAA-11: October 18, 1988 NOAA-12: May 14, 1991 o Duration, planned At least two years o Duration, actual TIROS-N: January 30, 1980 NOAA-6: June 30, 1986 NOAA-7: June 7, 1986 NOAA-8: October 31, 1985 NOAA-9: November 7, 1988 NOAA-10: Presently operating NOAA-11: Presently operating NOAA-12: Presently operating o Orbit type Near polar, circular, sun-synchronous o Semi-major axis 7231.8 km o Nominal altitude 853.7 km o Inclination angle TIROS-N: 102.3 degrees NOAA-6: 98.7 NOAA-7: 98.9 NOAA-8: 98.8 NOAA-9: 98.9 NOAA-10: 98.9 NOAA-11: 98.9 NOAA-12: 98.7 o Nodal period TIROS-N: 101.90 minutes NOAA-6: 101.12 NOAA-7: 101.95 NOAA-8: 101.29 NOAA-9: 102.09 NOAA-10: 102.13 NOAA-11: 102.10 NOAA-12: 101.34 o Equator crossing times (ascending)*: Morning orbit: NOAA-6: 0730 NOAA-8: 0730 NOAA-10: 0730 NOAA-12: 0730 Afternoon orbit**: TIROS-N: 1500 NOAA-7: 1430 NOAA-9: 1420 NOAA-11: 1340 * Local mean solar time **Afternoon orbits drift slowly with time. Instrument Parameters for MSU are: o Calibration Hot reference body and space background and scan cycle o Cross-track scan angle (degrees from nadir) +/- 47.35 o Scan time (seconds) 25.6 o Number of steps 11 o Angular FOV (degrees) 7.5 o Step angle (degrees) 9.47 o Step time (seconds) 1.84 o Ground IFOV at nadir (km diameter) 109.3 o Ground IFOV at end of scan 323.1 km cross-track x 178.8 km along-track o Distance between IFOV centers (km along-track) 168.1 o Swath width +/- 1174 km o Data rate (bits per second) 320 o Data precision (bits) 12 o Time between start of each scan line 25.6 sec o Step and dwell time 1.81 sec o Time* 0.9 sec *Time - the difference between the start of each scan and the center of the first dwell period. 4.3 Principles of Operation. The MSU is a four-channel Dicke microwave radiometer operating in the 60 GHz oxygen absorption complex. The four channels respond to the following respective spectral frequencies: 50.3, 53.74, 54.96, and 57.95 GHz with a channel bandwidth of 200 MHz in each case and a typical NEdN of 0.3 degrees K. (NEdN is noise equivalent differential radiance (milliwatts/m**2-steradian-cm**-1). MSU channel 2 senses radiation centered at 53.74 GHz. The instrument is externally calibrated once each scan with cold space (2.7 K) and a warm target whose temperature is monitored with redundant platinum resistance thermometers. The instrument scans across the satellite subtrack once every 25.4 seconds during which the satellite advances 170 km. Within each scan the instrument samples eleven footprints, one every 9.5 degrees of scan angle, with a spatial resolution of 110 km (circular) at nadir to 180x320 km (elliptical) at the scan extremes. The antenna half-power beam-width leading to these spatial resolutions is 7.5 degrees. The MSU data output represents an apparent brightness temperature after a 1.84-second integration period per step. The data are quantized to 12-bit precision and combined with telemetry and step position information to produce an effective output data rate of 320 bits per second. MSU has no special calibration sequence that interrupts normal scanning. The calibration data are included in a scan line of data. From the last Earth view position, the reflector rapidly moves 4 steps to view space, 10 additional steps to view the housing, and then returns to the home position to begin another scan line. Since each scan line requires 25.6 seconds, synchronization of MSU within the other two TOVS instruments occurs every 128 seconds (5 scan lines). 4.4 Measurement Geometry. The MSU sensors consist of two four-inch antennae, each having an IFOV of 7.5 degrees. The antennae are step-scanned through eleven individual 1.84-second Earth viewing steps and take a total of 25.6 seconds to complete. The 124 km IFOV resolution at the subpoint creates an underlap of approximately 115 km between adjacent scan lines. 5. DATA PROCESSING SEQUENCE 5.1 Processing Steps and Data Sets. Calibration of the MSU is described in Spencer, R.W. and J.R. Christy, 1990, and Spencer, R.W., J.R. Christy, and N.C. Grody, 1990, (see Item 11.2). After calibration, any physically unrealistic brightness temperatures, TB, (outside of 180 K to 270 K) at scan positions #1,2,3,4,8,9,10,11 cause that scan line to be rejected. Also checked are unrealistic TB differences between adjacent footprints (horizontal temperature gradients). The scan line is rejected if any are found. 5.2 Derivation Techniques/Algorithms. After a single scan line is accepted, a simple linear retrieval is performed, Channel "2R" TB = 4(TB3+TB4+TB8+TB9)/4 - 3(TB1+TB2+TB10+TB11)/4, where 2R is the Channel 2 reference value, TB3 is the TB at the third footprint position, and so forth. This produces a new weighting function (or, more properly, "averaging kernel") which has virtually no stratospheric influence and a peak near 700 mb. The resulting channel 2R TB is assigned to the 2.5 degree grid squares containing the middle three footprint positions (#5,6,7), except above 81 degrees latitude where the data are to the poleward footprint positions as well. This binning procedure is performed for each day separately. The daily average in every grid square is computed, and an east-west linear interpolation is performed for empty grid squares. At the end of each calendar month, the monthly average at each gridpoint is computed. Satellites are intercalibrated at the gridpoint level with the months of overlap between successive satellites. More information on the data set production is contained in Spencer, R.W and J.R. Christy, 1991, (see Item 11.2). 5.3 Special Corrections/Adjustments. None 5.4 Processing Changes. None 6. QUALITY ASSESSMENT 6.1 Data Validation by Producer. The monthly gridpoint anomalies were validated with radiosonde-calculated channel 2R TB at all United States controlled radiosonde stations (mainly over the U.S., the Pacific Ocean, and Caribbean Sea) during the ten year period 1979-88. Single station gridpoint errors (assuming the radiosonde as truth) ranged from 0.16 degrees C over the tropical west Pacific to 0.50 degrees C at high latitude continental locations, with correlations of 0.74 to 0.97, respectively. Compositing of several adjacent stations resulted in 0.11 degrees C to 0.35 degrees C, and correlations of 0.83 to 0.98, respectively. These are somewhat poorer than the results obtained with raw channel 2 averages, primarily due to the loss of daily synoptic scale temperature information in the retrieval procedure. Zonal averages, as well as hemispheric and global averages should be much better. Satellite intercomparisons reveal globally averaged channel 2R anomaly agreement to about 0.02 degrees C per month. Each MSU's channel 2 was found to be stable to about 0.01 degrees C over the lifetime of the instrument (up to five years). More information on radiosonde validation can be found in Spencer, R.W and J.R. Christy, 1990, (see Item 11.2). 6.2 Confidence Level/Accuracy Judgment. 6.3 Usage Guidance. Because of the loss of synoptic scale temperature gradient information in the retrieval, some east-west "smearing" in the monthly anomaly patterns is evident in the imaging. As a result, regionally averaged anomalies are probably much more accurate than single gridpoint anomalies. Also, high altitude (above 2000 m) regions will experience degraded accuracy. These include the Tibetan Plateau, portions of the Andes, eastern Antarctica, and northern Greenland. 7. CONTACTS FOR DATA PRODUCTION INFORMATION 7.1 Dr. Roy W. Spencer ES43 NASA Marshall Space Flight Center Huntsville, Alabama 35812 (205)544-1686 7.2 Dr. John R. Christy Johnson Research Center University of Alabama-Huntsville Huntsville, Alabama 35899 (205)895-6257 8. OUTPUT PRODUCTS AND AVAILABILITY 8.1 Tape Products. None 8.2 Film Products. A film of daily brightness temperatures from MSU was made. For more information, please contact the data producer. 8.3 Other products. 8.3.1 The Lower Tropospheric Temperature Anomalies from MSU in Common Data Format (CDF) Medium/Specification: Magnetic disk Format and Content: The data are stored in a special data-set-independent format, designated the Common Data Format (CDF). CDF was developed as a uniform method of storing and retrieving data on disk. The CDF contains data and descriptions about the data. A standard software package called the "CDF Library" allows a user within an NCDS session to create and access these data and descriptions. These CDF files may be accessed within the Data Applications subsystem of NCDS. Data Quantity/Rate: Lower Tropospheric Monthly Temperature Anomalies; 1 file, 13 Mb Lower Tropospheric Climatological Temp. Anomalies; 1 file, .51 Mb Status: Available Plans/Schedule: Additional data will be integrated periodically as they are received. 8.3.2 The Greenhouse Effect Detection Experiment (GEDEX) CD-ROM Medium/Specifications: CD-ROM in ISO 9660 standard Format and Content: The data on this disk will be stored in a special data-set-independent format, designated the Common Data Format (CDF). CDF was developed as a uniform method of storing and retrieving data on disk. The CDF contains data and descriptions about the data. A standard software package called the "CDF Library" will be included with this CD-ROM allowing a user to create and access these data and descriptions. The CD-ROM will consist of many different data sets related to the study of the Greenhouse Effect, including the Lower-to-Mid Tropospheric Temperature Anomalies from MSU data sets, and the accompanying NCDS data set documentation. Data Quantity/Rate: 1 CD-ROM disk set. Status: Release date for this product is scheduled for early 1992. Plans/Schedule: Users interested in this product should contact NCDS staff for more details. 9. DATA ACCESS 9.1 Archive Identification. 9.1.1 Goddard DAAC User Support Office NASA/Goddard Space Flight Center Code 935 Greenbelt, Maryland 20771 (301) 286-3209 FTS: 888-3209 INTERNET: NCDSUSO@NSSDCA.GSFC.NASA.GOV NSI DECnet: NSSDCA::NCDSUSO 9.1.2 Data Support Section National Center for Atmospheric Research (NCAR) P.O. Box 3000 Boulder, Colorado 80307 (303) 497-1215 9.2 Procedures for Obtaining Data. Users can obtain these data online through the NASA Climate Data System (NCDS). 9.3 NCDS Status/Plans. NCDS currently supports this data set in the Common Data Format (CDF) and will continue to update the data set as new data are received. These CDFs can be accessed by specifying the data set names within the Data Applications Subsystem of NCDS: NCDS$DATA:MSUTMP_MONTHLY NCDS$DATA:MSUTMP_CLIMATOLOGY 10. CONTACTS FOR ARCHIVE/DATA ACCESS INFORMATION 10.1 Goddard DAAC User Support Office NASA/Goddard Space Flight Center Code 935 Greenbelt, Maryland 20771 (301) 286-3209 FTS: 888-3209 INTERNET: NCDSUSO@NSSDCA.GSFC.NASA.GOV NSI DECnet: NSSDCA::NCDSUSO 10.2 Data Support Section National Center for Atmospheric Research (NCAR) P.O. Box 3000 Boulder, Colorado 80307 (303) 497-1215 11. REFERENCES 11.1 Satellite/Instrument/Data Processing Documentation a. Kidwell, K.B. (ed.), 1991. "NOAA Polar Orbiter Data Users Guide." NCDC/SDSD. (Updated from original 1984 edition.) 11.2 Journal Articles and Study Reports a. Spencer, R.W. and J.R. Christy, 1990. "Precise Monitoring of Global Temperature Trends from Satellites." Science 247:1558-1562. b. Spencer, R.W., J.R. Christy, and N.C. Grody, 1990. "Global Atmospheric Temperature Monitoring with Satellite Microwave Measurements: Method and Results 1979-84." Journal of Climate 3:1111-1128. c. Spencer, R.W. and J.R. Christy, 1991. "Precision and Radiosonde Validation of Satellite Gridpoint Temperature Anomalies, Part I: MSU Channel 2." Journal of Climate, submitted. d. Spencer, R.W. and J.R. Christy, 1991. "Precision and Radiosonde Validation of Satellite Gridpoint Temperature Anomalies, Part II: A Tropospheric Retrieval and Trends 1979-90." Journal of Climate, submitted. 11.3 Archive/DBMS Usage Documentation a. Olsen, L.M, J.W. Closs, and F.E. Corprew, November 1991. "NASA's Climate Data System Primer: Version 4.0." EOS DAAC, NASA Goddard Space Flight Center, Greenbelt, Maryland. 12. RELATED DATA SETS Several related temperature anomaly data sets exist online through NCDS as follows: 1) The GISS Temperature Deviations data set contains monthly temperature deviations for the period 1880 through 1988 and is available online through NCDS in Common Data Format (CDF). To access these CDFs, specify the following as input within the Data Applications Subsystem of the NCDS: Spatial Scale of Data Set Name Monthly Temperature Anomalies ------------- ----------------------------- NCDS$DATA:GISS-TMP-DEV_MON-GLB Global NCDS$DATA:GISS-TMP-DEV_MON-NH Northern Hemisphere NCDS$DATA:GISS-TMP-DEV_MON-SH Southern Hemisphere NCDS$DATA:GISS-TMP-DEV_MON-ZONE Latitude Zones NCDS$DATA:GISS-TMP-DEV_MON-BOXES 80 equal area boxes NCDS$DATA:GISS-TMP-DEV_MON-SUBBOXES 8000 equal area subboxes 2) The Climate Research Unit Temperature Deviations data set contains surface air temperature anomalies in degrees Celsius, derived from the World Weather Records (WWR). These data are available online through NCDS in Common Data Format (CDF). To access this CDF, specify the following as input within the Data Applications subsystem in NCDS. NCDS$DATA:CLIM-RSRCH-U_TMP-DEV 3) The Angell Global Temperature Deviations data set contains zonal temperature deviations derived from radiosonde measurements compiled in Monthly Climatic Data for the World, published by the National Climatic Data Center. These data are available online through NCDS in Common Data Format (CDF). To access this CDF, specify the following as input within the Data Applications subsystem in NCDS. NCDS$DATA:ANGELL_TMP_DEV 4) The Vinnikov, Groisman and Lugina zonal and station temperature data sets contain monthly, seasonal, and annual mean zonal temperatures deviations and monthly mean station temperatures deviations. These data are available online through NCDS in Common Data Format (CDF). To access these CDFs, specify the following as input within the Data Applications subsystem in NCDS: NCDS$DATA:VGL-TMP-DEV_MONTHLY NCDS$DATA:VGL-TMP-DEV_SEASONAL NCDS$DATA:VGL-TMP-DEV_ANNUAL NCDS$DATA:VGL-TMP-MON_NORTH-STATN NCDS$DATA:VGL-TMP-MON_SOUTH-STATN 13. SUMMARY/SAMPLE Unavailable as of this writing 14. NOTES None *92/03/12