GES DISC DAAC Data Guide:
NMC Gridded Data for UARS Project - Data Set Document

Summary:

Correlative gridded data from NOAA's National Center for Environmental Prediction (formerly known as the National Meteorological Center or NMC) are included as supplementary data products to the UARS Project. The main use of the correlative data from the NMC run is to provide an independent analysis for comparison with data from the UARS instruments. The correlative NMC data are intended to aid in validating the UARS instrument data. NMC data are available at the Goddard Space Flight Center (GSFC) Distributed Active Archive Center (DAAC).

NOTE: NCEP data products are still archived using NMC as part of the data set name to remain consistent with previously archived data. These acronyms refer to the same organization and may be used interchangably within this document.

Table of Contents:

• 1 Data Set Overview
• 2 Investigator(s)
• 3 Theory of Measurements
• 4 Equipment
• 5 Data Acquisition Methods
• 6 Observations
• 7 Data Description
• 8 Data Organization
• 9 Data Manipulations
• 10 Errors
• 11 Notes
• 12 Application of the Dataset
• 13 Future Modification and Plans
• 14 Software
• 15 Data Access
• 16 Output Products and Availability
• 17 References
• 18 Glossary of Terms
• 19 List of Acronyms
• 20 Document Information

1. Data Set Overview

Data Set Identification:

NMC CORRELATIVE DAILY DATA

Data Set Introduction:

The Goddard DAAC keeps the most current month of correlative NMC data online for users to download via anonymous ftp.

NMC GRIDDED DATA

The National Center for Environmental Prediction (NCEP) geopotential heights and temperatures are derived from two analysis systems:

1. tropospheric fields from 1000mb to 100mb, and
2. stratospheric analyses from 70 mb to 0.4 mb.

The tropospheric fields from 1000mb to 100mb are the 1200 GMT gridded fields which are part of the Global Daily Assimilation System (GDAS) described by McPherson et al. (1979), where data from radiosondes, aircraft, satellites, ships, buoys, or any other conventional means are assimilated and merged into meteorological fields (heights, temperature, winds). The stratospheric analyses developed by the National Weather Service Climate Analysis Center are 1200 GMT operational analyses at the 70-0.4mb pressure levels, produced from satellite temperature retrievals and RAOBS via a modified Cressman analysis (Gelman et al., 1987), which is a successive iteration method where the fields are iteratively adjusted by weighted data depending on distance from the grid point. Tropospheric temperature analyses use combined NOAA-10 and NOAA-11 data.

Moisture (only for Northern hemisphere) and Winds are obtained from the NCEP global data assimilation systems. Analyses from assimilation are on the same gridded fields as temperature and height analyses.

The data file structure for this file type is listed in the Standard Formatted Data Units (SFDU) documents listed in the References section below.

Objective:

The goal of upper atmosphere research is to understand the chemistry, dynamics, and energy balance above the troposphere as well as the coupling between these processes and between atmospheric regions. Understanding the mechanisms that control upper atmosphere structure and variability, as well as an understanding of how the upper atmosphere responds to natural and man-made causes will help define the role of the upper atmosphere in climate variability.

Summary of Parameters:

There are four measured parameters for NMC correlative data: geopotential height (HEIGHT), moisture (MOISTURE), temperature (TEMP) and winds (WINDS) both meridional and zonal wind components.

Discussion:

Data fields will be produced at 18 standard meteorological levels from 1000 mb to 0.4 mb for heights and temperatures. For moisture only the 6 lowest altitude pressure levels are used and there is no data for the southern hemisphere. For winds there are both U and V components. U comp. and V comp. of wind are given with respect to grid in the data files. For the northern hemisphere there is wind data only for the 12 lowest altitude pressure levels (up to the 50 mb level). For the southern hemisphere there is wind data only at the 4 levels 1000, 500, 300, and 250 mb.

Related Data Sets:

Other UARS data sets that measure the correlative value of the UARS instrument data include the UKMO Correlative Assimilation Data.

2. Investigators:

Principal Investigator:

Name:

Dr. Alvin Jim Miller

Addresses:

Code W/NMC53 NOAA/NWS

5200 Auth Rd, Room 805

Camp Springs, 20746-4304

Telephone Numbers:

Voice: +1 301-763-8071

FAX: +1 301-763-8125

Electronic Mail Address:

miller@upair.wwb.noaa.gov

Title of Investigation:

NMC Gridded Data Produced for UARS Project

Contact Information:

See Principal Investigator above.

3. Theory of Measurements:

Data from radiosondes, aircraft, satellites, ships, buoys, or any other conventional means are assimilated and merged into meteorological fields (heights,temperature, winds). Stratospheric analyses are 1200 GMT operational analyses at the 70-0.4mb pressure levels, produced from satellite temperature retrievals and RAOBS. Using a successive iteration method, the fields are iteratively adjusted by weighted data depending on distance from the grid point. Tropospheric temperature analyses use combined NOAA-10 and NOAA-11 data.

The operational analyses now use satellite retrievals. The minimum variance retrieval method is not dependent on week-old regression coeficients of co-located radiosonde data with satellite radiances as was done in the past.

4. Equipment:

Instrument Description:

Overview:

See Data Set Introduction above.

Collection Environment:

Satellite.

Platform:

Upper Atmosphere Research Satellite (UARS).

Platform Mission Objectives:

UARS was launched September 12, 1991 with the mission of investigating the chemical and dynamical processes of the Earth's upper atmosphere. See the UARS Project document for more information.

5. Data Acquisition Methods:

6. Observations:

Data Notes:

None at this time.

7. Data Description:

Spatial Characteristics:

Spatial Coverage:

The gridded fields are on the standard 65x65 NMC polar stereographic grid oriented 80W (grid increment 381 km at 60N), and 100E (grid increment 381 km at 60S); Pole at (33,33).

Spatial Coverage Map:

Data coverage for NMC on 5/22/1991. (Create map of NMC data!)

Spatial Resolution:

Resolution is about 2.5 degrees latitude by 2.0 degrees longitude. ??The Gaussian grid of 384x190, roughly equivalent to 1x1 degree latitude/longitude.

Projection:

Not Applicable.

Grid Description:

The gridded fields are on the standard 65x65 NMC polar stereographic grid oriented 80W (grid increment 381 km at 60N), and 100E (grid increment 381 km at 60S); Pole at (33,33). The NMC uses 18 standard pressure levels for data at 1000, 850, 700, 500, 400, 300, 250, 200, 150, 100, 70, 50, 30, 10, 5, 2, 1, 0.4 millibars.

Height and temperature data are produced at 18 pressure levels from 1000 mb to 0.4 mb. Moisture data are only produced in the northern hemisphere for the 6 lowest altitude pressure levels. Wind data are produced for the 12 lowest altitude levels in the northern hemisphere, and at the 4 levels 1000, 500, 300, and 250 mb in the southern hemisphere.

Temporal Characteristics:

Temporal Coverage:

The Goddard DAAC keeps the most current month of available NMC data online for users to download via anonymous ftp. After about one month, usually around the 20th, these data will be removed and the next month will be placed online. Older data can be ordered from the DAAC through its Web archive search or the telnet based IMS system.

Temporal Resolution:

The temporal resolution of NMC data granules is daily.

Data Characteristics:

Parameters:

Analyzed fields will be produced for the following parameters listed below with the subtype name, DAAC parameter name, and units:

8. Data Organization:

Data Granularity:

The granularity of NMC data are defined such that there is one granule for parameter subtype per day, for a total of 4 granules per day. Each NMC granule is a multi-file granule consisting of two files:

1. The binary data file (files ending with PROD, or *PROD extension) which contains the height, moisture, temperature, or winds data.

2. An ASCII metadata file (files ending with META, or *META extension) associated with the data file containing items such as the begin date, end date, altitude and record length size of the data file.

The naming convention for UARS granule file names distributed by the Goddard DAAC is as follows:

CORR_ZNMC_ Sssss_Ddddd.Vvvvv_ Ccc_xxxx

where: (dddd = UARS day, vvvv = data version #, cc = data cycle #)

ssss

is the subtype or parameter (STEMP),

dddd

is the UARS acquisition day (D0001 = 12 September 1991),

vvvv

is the data version number ,

cc

is the data version cycle number (C01), and

xxxx

is the file extension (PROD for the binary files, or META for the ASCII metadata files)

Average granule size is about 612 Kb for height and temperature granules, 115 Kb for moisture granules, and 546 Kb for wind granules. The *META files are small, only about 770 bytes each.

Data Format:

The data files each contain 1 header record followed by data records. Each data record contains data for both hemispheres at a constant pressure surface.

Data file structures are presented in the Standard Formatted Data Units (SFDU) documents listed in the References section.

9. Data Manipulations:

Formulae:

Derivation Techniques and Algorithms:

Data Processing Sequence:

Processing Steps:

Data used in the NMC analysis are purely from standard NMC sources, i.e., NOAA satellites, radiosondes from the worldwide network, aircraft winds, cloud vectors from satellites, and any other available data transmitted to NMC. This data are assimilated and merged into meteorological fields (heights, temperature, winds). The stratospheric analyses developed by the NMC Climate Analysis Center are 1200 GMT operational analyses at the 70-0.4mb pressure levels, produced from satellite temperature retrievals and RAOBS via a modified Cressman analysis (Gelman et al., 1987), which is a successive iteration method where the fields are iteratively adjusted by weighted data depending on distance from the grid point. Tropospheric temperature analyses use combined NOAA-10 and NOAA-11 data.

The operational analyses now use satellite retrievals based on a minimum variance simultaneous retrieval method described in Goldberg et al. (1988), Fleming et al. (1988), and Fleming et al. (1986). The minimum variance retrieval method is not dependent on week-old regression coeficients of co-located radiosonde data with satellite radiances as was done in the past.

The NMC analyses below 10mb are heavily dependent on RAOBS (parti- culary over the continents), but less dependent on the RAOBS and more dependent on the TOVS retrievals over ocean areas and ice covered regions.

Processing Changes:

None.

Calculations:

Special Corrections/Adjustments:

None.

Calculated Variables:

Analyzed fields will be produced for temperature, geopotential height, U and V wind components, and moisture.

10. Errors:

Sources of Error:

The data quality is given by the standard deviation of the quantity. Each data element in each file is stored along with a standard deviation which has been calculated by the analysis software. The nominal error is 10 m/s for the wind and 25 K for temperature.

Quality Assessment:

Data Validation by Source:

All data are checked by the ????? science team and assigned quality values. These values appear as the DATA_QUALITY_UARS fields in the ASCII metadata files. The format for DATA_QUALITY_UARS is a 3 character field of the form "p.q" where:

                VALUE       MEANING
         for p      0       Machine inspected
                    1       Qualitative evaluation
                    2       Intensive analysis
         for q      1       less than 50% good data
                    2       50% - 75% good data
                    3       76% - 98% good data
                    4       better than 98% good data

Measurement Error for Parameters:

Variances are included with each data value.

Additional Quality Assessments:

None.

Data Verification by Data Center:

Analysis quality of meteorological fields are continually evaluated and updated at NMC. Within the access codes provided to UARS, errors are attributed to profiles in a general sense, i.e., the errors are computed depending on whether the profile is given in a dense data region or in a poor data region, as over the ocean. Data files are checked to ensure that they are properly transferred. No additional data checks are performed by the DAAC.

11. Notes:

Limitations of the Data:

The data files exist as UNIX stream files at the DAAC. Binary data are IEEE formatted. The binary data files should be read on 32 bit machines running UNIX operating systems. This is especially important for fields which are IEEE floating point values, such as the profile data and quality values. If you are going to use a non 32-bit and/or non-UNIX machine, then you will need to write your own conversion routines to read the data files.

File record length information is only listed in the ASCII metadata files (*META extension) which accompany the data and parameter files.

Known Problems with the Data:

None at this time.

Usage Guidance:

The main use of analyses from the NMC run is to provide an independent analysis for members of the UARS science team to compare with equivalent retrievals derived form UARS instruments.

Any other Relevant Information about the Study:

None.

12. Application of the Data Set:

See Usage Guidanceabove.

13. Future Modifications and Plans:

Future reprocessing of the data are possible.

14. Read Software:

Software Description:

Simple read/dump programs are available for reading the ????? level 3A data files. The read programs are available in both Fortran and C languages. These programs simply print the file contents to the screen.

The *META and *PROD files (see the Data Granularity section) must be kept in the same directory, because the programs require the *META file as the input parameter in order to read the *PROD file. The *META file is necessary because it contains file record length information, which is not in the *PROD files.

If you are using the Fortran READ programs you may need to change the OPEN statement. Some machines read 4 byte words, while other machines read 1 byte. If the program isn't working correctly, you should try changing RECL=RECSIZ/4 to RECL=RECSIZ.

Contact science@eosdata.gsfc.nasa.gov for problems with the read/dump software.

Software Access:

To compile the programs, just type:

     f77 FILE_NAME.F -o FILE_NAME       (Fortran programs)

or

     cc file_name.c -o file_name            (C programs)

Below are examples showing how to run the programs:

     $ READUMP_L3AT_DATA                                           (Fortran program)
      PLEASE ENTER META DATA FILE NAME BELOW:
     ?????_L3AT_SH2O_D0001.V0003_C01_META

     $ readump_l3at_data ?????_L3AT_SH2O_D0001.V0003_C01_META      (C program)

15. Data Access:

Contact Information:

Name:

Help Desk

Addresses:

NASA Goddard Space Flight Center

Code 610.2

Greenbelt, MD 20771

Telephone Numbers:

Phone: 1-301-614-5224

FAX: 1-301-614-5268

Electronic Mail Address:

daacuso@daac.gsfc.nasa.gov

Archive Identification:

The UARS ????? data are archived at the GSFC DAAC, and can be identified by the attributes listed below.

         Data Set = UARS
     Data Product = ????? L3AL DAILY LAT ORDERED
                    ????? L3AT DAILY TIME ORDERED

Procedures for Obtaining Data:

The ????? level 3A data files can be obtained from the Goddard DAAC by several mechanisms. These include the following:

• The DAAC Web-Based Archive Interface provides a means for searching and ordering data. Select the UARS Data Set link.

• Anonymous FTP. The most recent month of NMC data (about 2 months from current) can be downloaded from the DAAC anonymous FTP server located at daac.gsfc.nasa.gov, in directory http://disc.sci.gsfc.nasa.gov/data/uars/???. This area can also be accessed through the World Wide Web at ftp://daac.gsfc.nasa.gov/data/uars/corr/nmc. For convenience, the data files are arranged in directories by parameter (e.g. http://disc.sci.gsfc.nasa.gov/data/uars/corr/nmc/moisture).

• EOSDIS V0 Web Gateway. You can place orders for the UARS data through the Earth Observing System Data and Information System (EOSDIS) Earth Science Web Gateway. From here you can also order data products from other data centers. The web address for the EOSDIS V0 Web Gateway is "http://harp.gsfc.nasa.gov/ims-bin/pub/imswelcome".

• The Goddard DAAC Information Management System (IMS), also provides online search and order capabilities for the UARS and other data sets. The IMS is a character based interface for VT100 emulators. To connect to the DAAC IMS:

  telnet daac.gsfc.nasa.gov

  Username: daacims

  Password: gsfcdaac

• DAAC Help Desk. Data can also be obtained by contacting the GSFC DAAC Help Desk listed above.

Data Archive Status/Plans:

The DAAC currently supports ????? level 3AL and 3AT data products.

16. Output Products and Availability:

The ????? level 3A data are available to anyone free of charge. See the section above on Procedures for Obtaining Data for specific information. For more information on ?????, please refer to the ????? Home Page.

17. References:

Satellite/Instrument/Data Processing Documentation:

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.

Journal Articles and Study Reports:

McPherson, R., D., K. H. Bergman, R. E. Kistler, G. E. Rasch, and D. S. Gordon: "The NMC Operational Global Data Assimilation System," Mon. Wea. Rev., Vol. 107, pp 1445-61.

Fleming, H. E., M. E. Goldberg, and D. S. Crosby, 1988: "Operational Implementation of the Minimum Variance Simultaneous Retrieval Method", Proceedings, AMS Third Conference on Satellite Meteorology and Oceanography, Jan. 31 - Feb. 5, 1988, Anaheim, Calif., pp.16-19.

"Minimum Variance Simultaneous Retrieval of Temperature and Water Vapor from Satellite Radiance Measurements", Preprint Volume, Second Conference on Satellite Meteorology/Remote Sensing and Applications, May 13-16, 1986, Williamsburg, Va. Published by the American Meteorological Society, Boston, Mass., pp 20-23.

Golberg, M. D. and J. M. Daniels, 1988: "A Method for Obtaining and Improved Approximation for the Temperature/Moisture Retrieval Problem", Proceeding, AMS Third Conference on Satellite Meteorology and Oceanography, Jan. 31 - Feb. 5, 1988, Anaheim, Calif. pp. 20-23.

Goddard DAAC IMS online documentation:

Documentation of NMC gridded data produced for UARS project, NURSNM01.

Horne, C., UARS Granule Level File (*META) Description, July 1994.

18. Glossary of Terms:

DATA PRODUCT

A collection of parameters packaged with associated ancillary and labeling data. Uniformly processed and formatted. Typically uniform temporal and spatial resolution. ????? level 3A data products include ?????_L3AL_DAILY and ?????_L3AT_DAILY. The ????? data product class is divided into data product subclasses according to measured parameters.

DATA SET

A logically meaningful grouping or collection of similar or related data. Data having mostly similar characteristics (source or class of source, processing level and algorithms, etc.) ????? is a subset of the UARS data set.

GRANULE

A Granule is the smallest aggregation of data which is independently managed.

PARAMETER

A measurable or derived variable represented by the data (e.g. air temperature, snow depth, relative humidity). At the Goddard DAAC, parameters are grouped into a Parameter General category, which is broken down into Parameter Specific.

19. List of Acronyms:

20. Document Information:

Document Revision Date:Fri May 10 11:54:09 EDT 2002

09 February 1998

UARS Project