CCSD1Z00000100000052CCSD1R00000300000032 DELIMITER=EOF; TYPE=CCSD1F000001; CCSD1C00000400000026 ADI=NURSML02; SUD=NURSML01; CCSD1R00000300000032 DELIMITER=EOF; TYPE=CCSD1D000002; UPPER ATMOSPHERE RESEARCH SATELLITE MICROWAVE LIMB SOUNDER Standard Formatted Data Units Whole Data Set Document June 1996 J. R. Burke and T. A. Lungu Jet Propulsion Laboratory California Institute of Technology, Pasadena, California UPPER ATMOSPHERE RESEARCH SATELLITE MICROWAVE LIMB SOUNDER Standard Formatted Data Units Document List: NURS1I00ML02 ** Whole Data Set NURS1I00ML01 File Class: Level 2 Data NURS1I00ML03 File Class: Level 3AT Data NURS1I00ML04 File Class: Level 3TP Parameter NURS1I00ML05 File Class: Level 3AL Data NURS1I00ML06 File Class: Level 3LP Parameter (** this document) UARS MLS SFDU DOCUMENT FOR: =========================== WHOLE DATA SET -------------- Introduction The Upper Atmosphere Research Satellite (UARS) project has an open data processing and archiving system in which retrieved geophysical data from any UARS investigation is made available to the general scientific community. In order to minimize ambiguity and errors in interpretation of the data the UARS Science Team accepted a recommendation from the UARS Data Systems Working Group that all UARS data products adhere to the Standard Formatted Data Units (SFDU) structure and construction rules as defined in Reference 1. The implementation for UARS data is described in Reference 2, and this documentation for the Microwave Limb Sounder (MLS) follows the Data Documentation Standard for UARS. The organization of SFDU documentation is hierarchical, with the top level describing the entire data set, and the bottom level describing a data item within a record. The hierarchy levels are: Whole Data Set, File Class, Record, and Field. A separate document is required for the Whole Data Set and for each File Class. For MLS there exist five SFDU File Classes: the Level 2 Data Set, the Level 3AT Data Set, the Level 3AL Data Set, the Level 3TP Parameter File and the Level 3LP Parameter File. MLS Level 0 Files contain raw instrument data; Level 1 Files contain calibrated measurements of radiance, derived diagnostics and supplemental data; Level 2 Files are retrieved geophysical data; and Level 3 Files contain geophysical data on common UARS grids. At each of these levels, the files contain data for one complete day. The SFDU documentation standards are only applicable to the Level 2 and Level 3 Data Sets. At the Whole Data Set level, the description of the data set gives an overall understanding of all MLS data products. A File Class is a group of files related by a common format. Files are constructed from elements called Records, which are constructed from elements called Fields. Each file belonging to a particular File Class is constructed from records of identical form in a defined order. Documentation of the data sets in each File Class describes how the data in each file was created, how the file is organized, and how the records within it are related. This is the Whole Data Set Documentation for the UARS Microwave Limb Sounder (MLS) Output Data Files Version 4 produced with MLS Production Processing Software Version 4.22, also valid for Output Data Files Version 3 produced with MLS Production Processing Software Version 4.11/4.12, unless otherwise specified. Data_Set_Name: UARS MLS Data Set. Data_Source: The MLS experiment on the UARS spacecraft. Scientific_Contact: ALL INITIAL ENQUIRIES SHOULD BE MADE TO THE MLS DATA MANAGER: MLS Data Manager Jet Propulsion Laboratory Mail Code 183-701 4800 Oak Grove Drive Pasadena, Ca. 91109-8099 Internet: mlsdaac@jplrac.jpl.nasa.gov Phone: 818 354-6849 Fax: 818 393-5065 Evan F. Fishbein Temperature analysis Jet Propulsion Laboratory Mail Code 183-701 4800 Oak Grove Drive Pasadena, Ca. 91109-8099 Internet: eff@tugh.jpl.nasa.gov Phone: 818 354-2250 Fax: 818 393-5065 Lucien Froidevaux Ozone analysis Jet Propulsion Laboratory Mail Code 183-701 4800 Oak Grove Drive Pasadena, Ca. 91109-8099 Internet: lucien@wilga.jpl.nasa.gov Phone: 818 354-8301 Fax: 818 393-5065 William G. Read "Forward Model" analysis Jet Propulsion Laboratory Mail Code 183-701 4800 Oak Grove Drive Pasadena, Ca. 91109-8099 Internet: bill@poobah.jpl.nasa.gov Phone: 818 354-6773 Fax: 818 393-5065 Hugh C. Pumphrey Water vapor analysis Department of Meteorology University of Edinburgh Mayfield Road, Edinburgh, Scotland, UK Internet: hcp@met.ed.ac.uk Phone: (UK) 031 650-6026 Fax: (UK) 031 662-4269 Michelle L. Santee Nitric Acid analysis Mail Code 183-701 4800 Oak Grove Drive Pasadena, Ca. 91109-8099 Internet: mls@praxis.jpl.nasa.gov Phone: 818 354-9424 Fax: 818 393-5065 Joe W. Waters Chlorine monoxide analysis Jet Propulsion Laboratory Mail Code 183-701 4800 Oak Grove Drive Pasadena, Ca. 91109-8099 Internet: joe@jedediah.jpl.nasa.gov Phone: 818 354-3025 Fax: 818 393-5065 Source_Characteristics: The UARS satellite orbit is inclined at 57 degrees, precessing daily with respect to the sun by about -4 degrees. For one day's data, the sampled local solar zenith angle varies by less than 10 degrees at a given tangent latitude on either the "day" or "night" side of the orbit. The entire diurnal cycle is sampled in about 36 days. The satellite is yawed through 180 degrees approximately every 36 days, and this ensures that one side of the satellite is never illuminated by the Sun, as required by MLS and other UARS instruments. The MLS is a limb sounder, viewing perpendicular to the orbital velocity vector from the anti-sun side. It scans only in elevation and, from the satellite altitude of about 580 km, MLS views the atmosphere at tangent points about 22 to 24 degrees below the orbital track. When the satellite flies in the forward direction, viewing to the anti-sun side gives latitude coverage from 34N to 80S, and when the satellite flies in the backward direction, coverage is from 80N to 34S. References 3 and 4 contain a synopsis of the UARS mission and its goals, and Reference 5 gives a description of the MLS Instrument. Investigation_Objectives: The UARS MLS experiment is designed to investigate the chemical composition of the Earth's upper atmosphere (upper troposphere, stratosphere and meso- sphere) on a global scale, day and night, over several years. A climatol- ogy of chemical species will be obtained, which, with observations from other UARS experiments, will provide a large data base of information regarding ozone chemistry and couplings between dynamical, chemical, and radiative processes. The MLS experiment is unique among UARS instruments in measuring chlorine monoxide (ClO), the predominant form of reactive chlorine that destroys ozone. SO2 injected into the upper atmosphere by the Mount Pinatubo volcanic eruption in June 1991 has been detected by UARS MLS (Reference 10). Additional new products from MLS include HNO3 (Reference 11), first available in MLS Version 4 data and upper tropospheric H2O (Reference 12) which is planned for version 5. Instrument_Attributes: UARS MLS measures microwave thermal emission from atmospheric molecules, in particular O3, H2O, ClO, HNO3 and SO2; O2 emission is also measured, and provides information on tangent pressure and temperature. There are three radiometers (63, 183, and 205 GHz), providing measurements in a total of six 510 MHz wide spectral bands. (The MLS 183 GHz radiometer ceased to work on April 16 1993, after which there are no stratospheric H2O measure- ments for MLS; tropospheric H2O, however is obtained from the 205 GHz radiometer which continues to operate as of April 1996). The signals from each band are detected in identical spectrometers having 15 contiguous channels with bandwidths ranging from 2 to 128 MHz. Vertical resolution is about 5 km for species profiles, and horizontal (along-track) resolution is 10 to 30 km. MLS views the limb of the Earth perpendicular to the UARS orbital velocity vector, and typically scans in discrete steps from about 5 km to 90 km every MLS major frame (MMAF) of 65.536 seconds. Within each MMAF, measurements are made in 32 minor frames (MMIF, each 2.048 seconds) with some of these periods reserved for radiometric calibration. See Reference 5 for more information on the UARS MLS Instrument, Reference 15 for Instrument Calibration and Reference 13 for further information on the technique. Measured_Parameters: The MLS Level 2 program has the flexibility to retrieve, constrain, or ignore a variety of parameters. The measured parameters for the Level 2 Data Set are specified by the structure SV_INFO (state vector information) contained in the header record. The parameters that are routinely retrieved are tangent pressure, temperature, and volume mixing ratios of ozone, water vapor, chlorine monoxide, nitric acid and sulfur dioxide. For ozone, there are two independent retrievals, one from the 205 GHz band (profile name O3_205) and one from the 183 GHz band (profile name O3_183). See References 16 trough 19 for details on Calibration of the most important measured parameters. Retrieved atmospheric profiles in the Level 2 data records are in the array PROFILE. Their estimated 1-sigma uncertainties (expected standard deviations) are in the array PROFILE_SDEV. State vector components which are normally constrained include O3_18_A (asymmetric ozone 18 isotope), O3_18_S (symmetric ozone 18 isotope) and heavy oxygen (O_18_O), as well as the line-of-sight component of wind. (Isotopic abundances of ozone are constrained to the expected fraction of the retrieved abundance of the dominant isotope, wind is constrained to zero with negligible or null expected impact.) The Level 2 files are time-ordered, with one record every MMAF (65.536 seconds), and one set of atmospheric profiles and other quantities per record. Profile values are retrieved for alternate (even-indexed) pressure levels on the UARS standard pressure grid (described in Reference 2). Each type of Level 3AT and 3AL file contains retrievals for one measured parameter. Types routinely available are: chlorine monoxide, ozone 205, ozone 183, water vapor, nitric acid, sulfur dioxide and temperature. The Level 3AT Data Sets are obtained directly from the Level 2 Data Set for even-indexed pressure levels. For the odd-indexed pressure levels the Level 3AT Data Sets are obtained by averaging values on adjacent even-indexed levels. The Level 3AL Data Sets are obtained by linear interpolation to the standard 4 degree UARS latitude grid (described in Reference 2). The Level 3 Parameter Files, 3TP and 3LP, contain diagnostic quantities and retrieval quality indicators which are very important for reliable inter- pretation of the data in the corresponding data files. Column ozone above a certain pressure (set to 46 hPa for Version 3 and Version 4 Data) and its estimated uncertainty are also stored in these files for both 183 and 205 GHz retrievals. Data_Set_Quality: For MLS Level 2 Data, the header record contains information on the overall data quality for each file. For each data record, estimated uncertainties, from random error sources and from some sources of systematic error, are included for each retrieved item. These estimated uncertainties are obtained from the square root of the diagonal terms of the covariance matrix. They are multiplied by -1 when the ratio of estimated uncertainty to a priori uncertainty is greater than 0.5. Similar estimated uncertainties exist in the Level 3 files (3AT, 3AL, 3TP and 3LP.) Other Level 2 quantities providing insight into the data quality are (see MLS SFDU File Class Documentation for Level 2): FLAG_AP FLAG_CHISQ_SPIKE FLAG_CHISQ_SPIKE_NUM FLAG_CLI FLAG_NEG FLAG_PTAN MMIF_STAT MMAF_STAT * BAND_INFO_MMAF.QUALITY * (* These quantities are also in the Level 3 Parameter files.) Values will appear in the PROFILE vector whether or not data were received from the instrument. These values are a combination of a priori values (obtained from climatology and contemporary NMC data) and instrument measurements. If no instrument data are received, the retrieval relaxes to the a priori and the estimated uncertainty value will be negative. The parameter MMAF_STAT in the Level 2 Data and Level 3 Parameter files, gives information on whether each major frame has good data, no data, bad data or other possible problem. The Level 2 data parameter PROFILE_ERRED (organi- zed identically to the PROFILE vector) reflects the "error reduction factor" (a value of 1 indicates no error reduction and that all information is from a priori; a value near zero indicates all information is from MLS measurements; a value of 0.5 indicates the a priori contribution is 25 %). Data_Processing_Overview: The MLS geophysical data products are obtained from measurements by a sequential estimation retrieval technique using algorithms which follow the theory described in Reference 14. MLS Level 2/3A Processing uses Level 1 calibrated radiance and ancillary data as input, and routinely processes one full day's data in each run. Other inputs are: user selected options and parameters (all echoed in the Level 2 Data File header record), a file of processing coefficients for use in the retrieval process, a file of space radiance offsets, default climatological data, optional UARS Climatological Atmospheric Data, and optional National Meteorological Center (NMC) Data. Note, the UARS Climatological Atmospheric Data and NMC Data are normally used as a priori information except in rare instances when they are unavailable. MLS Level 2/3A Processing produces the Level 2 Product, the Level 2 Log file, an optional file of diagnostic data for a selected range of major frames, the Level 3A products, the Level 3 Parameter Files, and a file of "last major frame quantities" used to begin the next day's processing. MLS Level 2/3A Processing consists of two programs (MLS_TANTRAK and MLS_ RETRIV) run sequentially. MLS_TANTRAK creates temporary files containing the Level 1 radiances and ancillary data mapped onto the tangent track. The retrieval program steps through these data in a sequential manner. The MLS_RETRIV program processes tangent track files in a forward direction in time. (The program can optionally process in both forward and backward directions but this option has not been used for Version 3 or Version 4 Data Products.) During the forward pass, MLS_RETRIV reads tangent track data one major frame at a time, and loops through each MMIF updating the retrieved quantities, using a sequential estimation algorithm. At the start of each MMIF a new a priori tangent pressure (PTAN63_APR) is calculated; at the end of each minor frame, the retrieved tangent pressure (PTAN63) is saved. At the beginning of each major frame, new a priori profiles are calculated. At the end of each major frame the retrieved profiles are written to the output file. In MLS Level 2 processing, for data version up to 4, geophysical parameter values are retrieved for even-indexed levels of the standard UARS pressure grid. The Level 3AT and 3TP Data Sets are obtained from Level 2 data by copying values for the even-indexed levels, and by averaging quantities from adjacent pressure levels to fill in values on the odd-indexed levels. The Level 3AL and 3LP Data Sets are obtained by interpolating the Level 3AT and 3TP Data Sets to the UARS latitude grid. Data_Usage: Level 2 data sets provide atmospheric profiles every 65.536 seconds, which is the duration of a MLS Major Frame (MMAF), equivalent to the UARS Engineering Major Frame (EMAF). Sensitivity for ozone, water vapor and temperature decreases in the lower stratosphere and in the mesosphere. ClO retrievals are noisy for individual profiles, and useful only under conditions of enhanced concentrations (more than about 1 ppbv) in the lower stratosphere. Averaged values should be used for better signal to noise. HNO3 is also fairly noisy, for individual profiles. Also, V4 software do not properly retrieve HNO3 under conditions of high SO2, because of strongly corelated signals (from SO2 and HNO3) and HNO3 in general has not been vali- dated or scrutinized to the extent that other MLS instruments have. Mesospheric ozone may lose some accuracy for observations across the terminator regions (REF_SOLAR_ILLUM = 3 or 4), because of rapid variations along the line of sight which are not taken into account in the production processing. Sensitivity to water vapor is lost just below 46 hPa, and sensitivity for temperature is lost below 46 hPa due to saturation. It is emphasized that the data file estimated uncertainties, and their signs, together with other parameter file diagnostics and quality indicators (identified in Data_Set_Quality above) should be examined carefully to ensure the validity of any data used in scientific analyses. The usefulness and significance of these quality indicators vary from parameter to parameter, and demand some experience and insight for prudent interpretation. The MLS Team would appreciate being quickly informed of any apparent anomalies which are found in the data and which are not flagged by the quality indicators. Such information will help us to improve the quality of these data in future reprocessing. Feedback on documentation errors would also be appreciated. Data_Organization: There is one File Class each for the Level 2, Level 3AT and Level 3AL Data Files, and for the Level 3TP and Level 3LP Parameter Files. File_Class_Relationships: All of the information in the Level 3AT and 3AL Files is contained in (or can be directly calculated from) the Level 2 Data Set. The Level 3 Parameter Files provide important information to help qualify the other Level 3 files. Lit_References: 1. Consultative Committee for Space Data Systems, CCSDS 620.0-B-1, Standard Formatted Data Units -- Structure and Construction Rules, November 1987. 2. Computer Sciences Corporation, CSC/SD-86/6704/UD6, UARS Central Data Handling Facility (CDHF) Software System (UCSS) Programmer's Guide to Production Software Support Services, February 1993. 3. UARS Project Data Book, General Electric, (now Martin Marietta) Astro- Space Division, P.O. Box 8555, Philadelphia, Pennsylvania 19101, April 1987. 4. Reber, C. A., C. E. Trevathan, R. J. McNeal, and M. R. Luther, The Upper Atmosphere Research Satellite (UARS) Mission, J. Geophys. Res. 98, D6, 10643-10647, 1993. 5. Barath, F. T., et al, The Upper Atmosphere Research Satellite Microwave Limb Sounder Instrument, J. Geophys. Res. 98, D6, 10751- 10762, 1993. 6. Waters, J. W., et al, Stratospheric ClO and ozone from the Microwave Limb Sounder on the Upper Atmosphere Research Satellite, Nature, 362, 597-602, 1993. 7. L. Froidevaux, J. W. Waters, W. G. Read, L. S. Elson, W. G. Read, D. A. Flower, and R. F. Jarnot, Global ozone observations from UARS MLS: an overview of zonal mean results, Journal of Atmos. Sci. (special issue on UARS early scientific results), vol. 51, pp. 2846-2866, 1994. 8. W. A. Lahoz, A. O'Neill, E. S. Carr, R. S. Harwood, L. Froidevaux, W. G. Read, J. W. Waters, J. B. Kumer, J. L. Mergenthaler, A. E. Roche, G. E. Peckham, and R. Swinbank, "Three-dimensional evolution of water vapour distributions in the northern hemisphere as observed by MLS, Journal of Atmos. Sci. (special issue on UARS early scientific results), vol. 51, pp. 2914-2930, 1994. 9. G. L. Manney, L. Froidevaux, J. W. Waters, R. W. Zurek, W. G. Read, L. S. Elson, J. B. Kumer, J. L. Mergenthaler, A. E. Roche, A. O'Neill, R. S. Harwood, I. MacKenzie and R. Swinbank, Chemical depletion of ozone in the Arctic lower stratosphere during winter 1992-93," Nature, vol.370, pp. 429-434, 1994. 10. Read, W. G., L. Froidevaux and J. W. Waters, Microwave Limb Sounder Measurements of Stratospheric SO2 from the Mt Pinatubo Volcano, Geophys. Res. Lett., 20, 1299-1302, 1993. 11. M. L. Santee, W. G. Read, J. W. Waters, L. Froidevaux, G. L. Manney, D. A. Flower, R. F. Jarnot, R. S. Harwood, and G. E. Peckham, Interhemispheric differences in polar stratospheric HNO3, H2O, ClO and O3, Science, vol. 267, pp. 849-852, 1995. 12. W. G.Read, J. W. Waters, L. Froidevaux, D. A. Flower, R. F. Jarnot, D. L. Hartmann, R. S. Harwood, and R. B. Rood, Upper-tropospheric water vapor from UARS MLS, Bull. Am. Meteorol. Soc., vol. 76, pp. 2381-2389, 1995. 13. Waters, J. W., Microwave Limb Sounding, Chapter 8 in Atmospheric Remote Sensing by Microwave Radiometry, M. A. Janssen editor, John Wiley and Sons Inc., New York, 1993. 14. Rodgers, C. D., Retrieval of Atmospheric Temperature and Composition from Remote Measurements of Thermal Radiation, Rev. Geophys. and Sp. Phys., 14, 609-624, 1976. 15. R. F. Jarnot, R. E. Cofield, J. W. Waters, D. A. Flower, and G. E. Peckham Calibration of the Microwave Limb Sounder on the Upper Atmosphere Research Satellite, J. Geophys. Res. 101, D6, 9957-9982, 1996 16. E. F. Fishbein, R E. Cofield, L. Froidevaux, R. F. Jarnot, T. A. Lungu, W G. Read, Z. Shippony, J.W. Waters, I. S. ,McDermid, T J. McGee, U. Singh, W. Gross, A. Hauchecome, P. Keckhut, M. E. Gelman and R. M. Nagatani, Validation of UARS Microwave Limb Sounder temperature and pressure measurements, J. Geophys. Res. 101, D6, 9983-10016, 1996 17. L. Froidevaux, W. G. Read, T A. Lungu, R. E. Cofield, E. F. Fishbein, D. A. Flower, R. F. Jarnot, B. P. Ridenoure, Z. Shippony, J. W. Waters, J. J. Margitan, L. S. McDermid, R. A. Stachnik. G. E. Peckham, G. Braathen, T. Deshler, J. Fishman, D. J. Hofmann, and S. J. Oltmans, Validation of UARS Microwave Limb Sounder ozone measurements, J. Geophys. Res. 101, D6, 10017-10061, 1996 18. J. W. Waters, W. G. Read, L. Froidevaux, T. A. Lungu, V. S. Perun, R. A. Stachnik, R. F. Jarnot, R. E. Cofield, E. F. Fishbein, D. A. Flower, J. R. Burke, J. C. Hardy, L. L. Nakamura, B. P. Ridenoure, Z Shippony, R. P. Thurstans, L. M. Avallone, D. W. Toohey, R. L. deZafra, and D. T Shindell, Validation of UARS Microwave Limb Sounder ClO measurements, J. Geophys. Res. 101, D6, 10091-10128, 1996 19. W. A. Lahoz. M. R. Suttie, L. Froidevaux, R. S. Harwood, C. L. Lau, T. A. Lungu, G. E. Peckham, H. C. Pumphrey, W. G. Read, Z. Shippony, R. A. Suttie, J. W. Waters, G. E. Nedoluha, S. J. Oltmans, J. M. Russell III, and W. A. Traub, Validation of UARS Microwave Limb Sounder 183 GHz H2O measurements, J. Geophys. Res. 101, D6, 10129-10150, 1996 20. D. A. Flower, T. A. Lungu, C. C. Voge, UARS MLS SFDU Whole Data Set Document, 1993 --------------------------------------------------------------------------- End of Document UARS MLS SFDU Whole Data Set Document June, 1996