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GES DISC DAAC Data Guide:UARS WINDII Level 3A Data Sets Document

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The Wind Imaging Interferometer (WINDII) is one of 10 instruments aboard the Upper Atmosphere Research Satellite (UARS). Its primary objective is the measurement of winds and temperatures in the upper mesosphere and lower thermosphere. WINDII is the first instrument to make direct measurements of mesosphere and thermosphere winds from space. Regular data collection began 24 December 1991 and has continued, with a few interruptions, to the present. WINDII data have been processed to levels 1, 2, 3AL and 3AT. Currently, WINDII level 3A version 9 data products are available from the Goddard Space Flight Center (GSFC) Distributed Active Archive Center (DAAC).


Table of Contents:

1. Data Set Overview:

Data Set Identification:


Data Set Introduction:

The WINDII level 3A data are a subset of the UARS dataset. The WINDII data are archived as two data products at the DAAC:


Level 3AL
WINDII level 3AL data are daily latitude- and time-ordered data interpolated to intervals of 4 degrees latitude at the intersection of the tangent track of the instrument's line of sight (LOS). Each record consists of a single array of data of one parameter for a specific time. Level 3AL data records are written to UARS defined standard latitudes, which range from -88 to +88 degrees in 4 degree intervals.


Level 3AT
WINDII level 3AT data are daily time-ordered data, arranged at time intervals of 65.536 seconds, or about 495 km intervals along the LOS tangent track. The reference time at which level 3AT data are arranged is common across all UARS level 3AT files.


WINDII measures wind, temperature, and emission rate in the upper mesosphere and lower thermosphere (80 to 300 km) from observations of the Earth's airglow. Measurements are made both day and night providing global coverage of this region of the atmosphere.

Summary of Parameters:

Vertical profiles of wind (meridional and zonal components) and temperature.


The WINDII Level 3AL and 3AT data are written as Standard Data Format Units (SFDU) files. Each file consists of three records called SFDU, LABEL, and DATA. The SFDU and LABEL records contain descriptive information about the instrument and the data, such as start/stop time of the data, number of records in the file, etc. The DATA record contains the profile data and their standard deviations. Time, latitude longitude, local solar time, and solar zenith angles are provided with each DATA record. Each data file is accompanied by a short ASCII metadata file, which provides descriptive information such as the start and stop time of the data, file record lengths, and the UARS quality flag.

After the original level 3A file formats were agreed to, it was realized that additional parameters were needed to describe the WINDII data. Level 3LP and 3TP parameter files were created to include values for the WINDII JOB version number, CDB version number, inversion quantity flag, temperature source flag, and filter number and quality flag. Each level 3AL file for a given day is accompanied by a level 3LP file. Similarly, each level 3AT file for a given day is accompanied by a level 3TP file. The 3LP and 3TP files also consist of the three record types SFDU, LABEL and DATA, and are also accompanied by their own ASCII metadata files.

Related Data Sets:

All UARS level 3AL and 3AT files use the same formats to allow for intercomparisons of atmospheric profiles between the different instruments. The UARS High-Resolution Doppler Imager (HRDI) instrument also measures wind and temperature data.

2. Investigator(s):

Investigator(s) Name and Title:

Dr. Gordon Shepherd
Department of Earth and Atmospheric Sciences
York University
4700 Keele Street
North York, Ontario
Canada, M3J 1P3
Electronic Mail Address:


Dr. Brian Solheim
Centre for Research in Earth and Space Science
York University
4700 Keele Street
North York, Ontario
Canada, M3J 1P3
Electronic Mail Address:

Title of Investigation:

Wind Imaging Interferometer

Contacts for Scientific Aspects of the Data:

See the WINDII Instrument Home page.

3. Theory of Measurements:

The WINDII instrument utilizes emission lines for the basic Doppler shift measurements of wind fields. In addition to lines of neutral and ionized atomic oxygen, these include two lines of the OH molecule and a molecular oxygen line. WINDII takes measurements during daylight and night conditions. For a thorough description on the theory of measurement see the article "WINDII - the Wind Imaging Interferometer on the Upper Atmosphere Research Satellite" listed in the reference section 17.1 below.

4. Equipment:

Sensor/Instrument Description:


The UARS WINDII instrument is a field widened Michelson interferometer with an eight position filter wheel to select target emissions. It has a large forward baffle which together with limb pointing mirrors and telescopes define two fixed fields of view (FOV). The two FOVs are combined in a field combining prism and are then imaged, side by side, through the Michelson and camera optics onto a charge coupled detector (CCD).

One FOV looks forwards at 45 degrees from the satellite velocity vector and one FOV looks backwards at 135 degrees from the velocity vector. Both FOV boresights are inclined 22.1 degrees below the spacecraft nominal horizontal plane. Each FOV is 4 degrees horizontal by 6 degrees vertical. This gives an altitude coverage of 70 to 300 km for each field of view. The horizontal range is 160 km at the limb in each field of view. Due to oblateness of the earth the vertical coverage varies by about 20 km over one orbit. The attitude of the UARS satellite is controlled and the final attitude is known so that the look direction is well known. The CCD has 320 pixels in the horizontal, 160 pixels in each FOV, and 256 pixels in the vertical. This gives a maximum altitude resolution of 1 km.

Collection Environment:

Satellite data are collected from a near-circular Earth orbit of about 585 km altitude and 57 degree inclination.


Upper Atmosphere Research Satellite (UARS).

Source/Platform Mission Objectives:

UARS was launched in September 1991 with the mission of investigating the chemistry, dynamics, and energy inputs of the Earth's upper atmosphere. See the UARS Project and UARS Platform documents for more information.

5. Data Acquisition Methods:

Data are telemetered from UARS through the Tracking and Data Relay Satellite System (TDRSS) to the Data Capture Facility (DCF) at NASA GSFC. There the data are given an initial quality check, and are then forwarded to the UARS Central Data Handling Facility (CDHF). The instrument PI teams are connected to the CDHF through remote analysis computers (RACs), where they have developed software to convert the raw data to higher level processed data. The CDHF uses the production software to convert the level 0 data to level 1, 2, 3AT, and 3AL data. The Goddard DAAC acquires the UARS data from the CDHF.

6. Observations:

Data Notes:

None at this time.

7. Data Description:

Spatial Characteristics:

Spatial Coverage:

Spatial coverage alternates each UARS yaw cycle, approximately 36 days, from latitude -45 to 72 (northward looking), and from latitude -72 to 45 (southward looking). Vertical coverage is from approximately 80 to 300 km.

Spatial Coverage Map:

Data coverage for WINDII looking northward on 10/1/1993.

windii coverage

Spatial Resolution:

Level 3AL: 4 degrees latitude, varies in longitude.
Level 3AT: varies in latitude and longitude. Near the equator, latitude resolution is about 3 degrees.


Vertical resolution is 3 to 5 km.


Not Applicable.

Grid Description:

All WINDII level 3A data have been referenced to the UARS standard altitude grid. The index of the data array defines the altitude as given by:
  Z(i) = 5 * i,                 i <= 12
  Z(i) = 60 + (i - 12) * 3,     13 <= i <= 32
  Z(i) = 120 + (i - 32) * 5,    33 <= i <= 88.
Altitude levels are in kilometers.

Temporal Characteristics:

Temporal Coverage:

Temporal coverage is from 24 December 1991 to the present. The GSFC DAAC currently has the first 2.5 years of WINDII level 3AL and 3AT data (up to 10 April 1994). Listed below are the dates within the above time period for which WINDII data are missing or unavailable:

28-Dec-1991, 03-Jan-1992, 13-Jan-1992, 14-Jan-1992, 17-Jan-1992 to 29-Jan-1992, 07-Feb-1992, 08-Feb-1992, 10-Feb-1992, 15-Feb-1992, 23-Feb-1992, 01-Mar-1992, 03-Mar-1992, 18-Mar-1992, 21-Mar-1992, 24-Mar-1992, 08-Apr-1992, 09-Apr-1992, 30-Apr-1992, 03-May-1992, 07-May-1992, 10-May-1992, 17-May-1992, 24-May-1992, 28-May-1992, 03-Jun-1992 to 20-Jul-1992, 22-Jul-1992, 27-Jul-1992, 04-Aug-1992, 06-Aug-1992, 07-Aug-1992, 10-Aug-1992, 14-Aug-1992, 15-Aug-1992, 17-Aug-1992, 31-Aug-1992, 04-Sep-1992, 07-Sep-1992, 12-Sep-1992 to 14-Sep-1992, 18-Sep-1992, 28-Sep-1992, 12-Oct-1992, 15-Nov-1992, 18-Dec-1992, 03-Feb-1993 to 05-Feb-1993, 08-Feb-1993, 09-Feb-1993, 14-Feb-1993, 18-Feb-1993, 21-Feb-1993, 25-Feb-1993, 28-Feb-1993, 04-Mar-1993, 07-Mar-1993, 09-Mar-1993, 14-Mar-1993 to 16-Mar-1993, 20-Mar-1993, 23-Mar-1993, 27-Mar-1993, 30-Mar-1993, 01-Apr-1993, 03-Apr-1993 to 05-Apr-1993, 07-Apr-1993, 10-Apr-1993, 13-Apr-1993, 17-Apr-1993 to 20-Apr-1993, 24-Apr-1993, 28-Apr-1993, 03-May-1993, 03-Jul-1993, 06-Jul-1993, 10-Jul-1993, 13-Jul-1993, 14-Jul-1993, 19-Jul-1993, 25-Jul-1993, 31-Jul-1993, 05-Aug-1993 to 12-Aug-1993, 15-Aug-1993, 19-Aug-1993, 26-Aug-1993, 29-Aug-1993, 02-Sep-1993, 18-Sep-1993 to 26-Sep-1993, 30-Sep-1993, 02-Oct-1993 to 26-Oct-1993, 28-Oct-1993, 31-Oct-1993, 11-Nov-1993, 12-Nov-1993, 14-Nov-1993, 18-Nov-1993, 21-Nov-1993, 22-Nov-1993, 25-Nov-1993, 28-Nov-1993, 02-Dec-1993, 05-Dec-1993, 09-Dec-1993, 10-Dec-1993, 12-Dec-1993, 16-Dec-1993, 19-Dec-1993, 23-Dec-1993, 27-Dec-1993, 30-Dec-1993, 03-Jan-1994, 06-Jan-1994, 09-Jan-1994, 12-Jan-1994, 20-Jan-1994, 24-Jan-1994, 27-Jan-1994, 31-Jan-1994, 10-Feb-1994, 26-Feb-1994, 15-Mar-1994 to 17-Mar-1994, 19-Mar-1994 to 21-Mar-1994, 24-Mar-1994, 25-Mar-1994, 05-Apr-1994, 07-Apr-1994, 09-Apr-1994


Temporal Resolution:


Data Characteristics:


There are three measured parameters for WINDII Level 3AL and 3AT data products. The parameters are vertical profiles gridded to the UARS standard altitude grid (see above). The measured parameters are listed in the table below with the original subtype name, DAAC parameter name, units, and valid range:


Subtype DAAC Parameter Name Units Range

8. Data Organization:

Data Granularity:

WINDII Level 3A granules are defined such that there is one granule for each process level (3AL and 3AT), and parameter/subtype per day. Thus, for WINDII there are 6 granules per day. Each granule is a multi-file granule consisting of four files:


  1. The binary data file (files ending with PROD, or *PROD extension) which contains the vertical profile data, and quality (standard deviations), along with time, latitude, longitude, local solar time, and solar zenith angle.


  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, PI assigned quality flag and record length size of the data file.


  3. A binary parameter file (also *PROD extension) designated 3LP for 3AL granules, and 3TP for 3AT granules. The subtype for these files is PARAM. The WINDII parameter files contain JOB version number, CDB version number, inversion quantity flag, temperature source flag, and filter number and quality. These files were added to accommodate the additional WINDII values after the 3AL and 3AT file formats had already been finalized.


  4. An ASCII metadata file associated with the parameter file (also *META extension). The information is identical to the metadata file associated with the data file, except that the record length applies to the parameter file.

The format for granule file names is WINDII_Llll_Sssss_Ddddd .Vvvvv_Ccc_xxxx, where lll is the data processing level (3AL, 3AT, 3LP, or 3TP), ssss is the parameter subtype, dddd is the UARS day (0001 = 12 September 1991), vvvv is the data version number, and cc is the data version cycle number. The file extension xxxx is either PROD for the binary files, or META for the ASCII metadata files.

The average size for WINDII level 3AL granules is about 260 kilobytes, and 320 kilobytes for level 3AT granules. The *META files are small, only about 700 bytes each.

Data Format:

The data are in a native UARS format (SFDU). The files were originally created on a VAX/VMS system at the UARS CDHF, and now exist as UNIX stream files at the Goddard DAAC. WINDII data file structures are presented in the Standard Formatted Data Units (SFDU) documents listed in the References section.

9. Data Manipulations:


Derivation Techniques and Algorithms:

All the algorithms used to process the data are defined in detail in various software design documents, however, these are not needed to understand the WINDII data. The algorithms are set up to operate on measurements in sequence. One atmospheric measurement is composed of a background image and 4 (90 degree phase steps), 8 (45 degree phase steps) or 2*4 (90 degree phase steps for each group of 4 images) phase images. A 2*4 phase image measurement is called a "repeated measurement". Frequent calibration measurements are also processed and used with the corresponding atmospheric measurements. A frequent calibration measurement comprises a dark current image and 4 phase images of one of the onboard calibration lamps.

Data Processing Sequence:

Processing Steps:

The data processing is divided into three main jobs. The first job reads the raw telemetry files or level 0 data and interprets the data packet headers. The measurements are separated according to the atmospheric line observed and saved in intermediate files. Next the instrument calibration data is used to subtract dark current and to convert the count rate per bin to a line of sight intensity given in rayleighs. Once the known instrument corrections are made effects due to the UARS spacecraft are determined. The orbit attitude data are used to compute the location of the tangent point for each line of sight for each measurement bin. The frequent phase measurements are also processed in the first job step. The level 1 data, cataloged at the end of job step 1, contain the calibrated data and the geo-referencing data. These data are input to job step 2.

WINDII views the limb of the airglow and so the intensity measured in each bin is the line of sight integral of the volume emission rate modified by the Michelson interferogram. In the second job step the level 1 bin intensities for each of the 4 or 8 phase steps are used to compute what are termed "apparent quantities". These contain the atmospheric information. The apparent phase is the intensity weighted line integral giving the atmospheric wind. The apparent visibility is the intensity weighted line integral giving the atmospheric temperature. The apparent intensity is the line integral of the volume emission rate. Each measurement is composed of vertical columns of bins. A column gives a vertical scan through the airglow layer. A typical image has 6 columns, each about 25 km wide. In order to reduce the effects of gravity waves on the final wind and temperature these 6 columns are averaged together to form a single vertical profile for each field of view. The apparent intensity is inverted using constrained Twomey inversion to give the volume emission rate profile (see "Introduction to the Mathematics of Inversion in Remote Sensing and Indirect Measurements" by S. Twomey, Development in Geomathematics series, Elsevier, New York, 1977). This is then used to deconvolve the apparent phase and visibility. Finally the wind and temperature profiles are computed from the inverted phase and visibility for each field of view. The last step in the level 2 processing is to combine the line of sight winds from each FOV to form the desired vector winds. This is done by selecting data from the forward FOV which overlaps data from the backward FOV. The zonal and meridional components of the wind are computed only if the two FOVs see the same volume and the volume emission rates and temperatures (both scalar quantities) agree within specified limits. The level 2 data are saved for each measurement with no interpolation.

The final job step reads the level 2 data and interpolates from the natural measurement locations to the standard UARS grid. Only the wind and the temperature are gridded and saved in the level 3 data product. A parameter file at level 3 gives the source of the data used to derive the wind and temperature.

Processing Changes:

Reprocessing of the data occur about once a year.


Special Corrections/Adjustments:


Calculated Variables:

Meridional and zonal wind components are calculated, as well as temperature.

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 WINDII 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:


Data Verification by Data Center:

Data files are checked to ensure that they are properly transferred and translated from their original VAX/VMS format at the UARS CDHF to the DAAC's UNIX format. No additional data checks are performed by the DAAC.

11. Notes:

Limitations of the Data:

The data and parameter files exist as UNIX stream files at the DAAC. Binary data are big-endian 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 data may be used to provide global synoptic maps of wind and temperature in the upper mesosphere and lower thermosphere.

Any Other Relevant Information about the Study:


12. Application of the Data Set:

WINDII has produced an enormous amount of data on the upper atmosphere. Scientists around the world are using the data in a number of applications, for example:
  • to characterize large scale atmospheric wave phenomena
  • to measure seasonal and long term variations in the atmospheric composition
  • to measure polar mesospheric cloud phenomena and
  • to model the global upper atmosphere weather

13. Future Modifications and Plans:

The WINDII instrument continues to acquire data. Future reprocessing of the data are anticipated.

14. Read Software:

Software Description:

Simple read/dump programs are available for reading the WINDII level 3A data files. The read programs are available in C and IDL languages.

Software Access:

To get the software use the links below:

15. Data Access:

Contacts Information:

Help Desk
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:


Archive Identification:

The UARS WINDII data are archived at the GES DISC under the UARS Project.

Procedures for Obtaining Data:

The WINDII level 3A data files can be obtained from the GES DISC by several mechanisms. These include the following:


Data Archive Status/Plans:

The GES DISC currently supports WINDII level 3AT and 3AL data products.

16. Output Products and Availability:

The WINDII level 3A data are available. See the section above for Procedure for Obtaining Data for more information. For more information on WINDII, please refer to the WINDII Instrument 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.
  • G.G. Shepherd, G. Thuillier, W.A. Gault, B.H. Solheim, C. Hersom, J.M. Alunni, J.-F. Brun, S. Brune, P. Charlot, L.L. Cogger, D.-L. Desauliniers, W.F.J. Evans, R.L. Gattinger, F. Girod, D. Harvie, R.H. Hum, D.J. W. Kendall, E.J. Llewellyn, R.P. Lowe, J. Ohrt, F. Pasternak, O. Peillet, I. Powell, Y.J. Rochon, W.E. Ward, R.H. Wiens, J. Wimperis, WINDII - The Wind Imaging Interferometer on the Upper Atmosphere Reseasrch Satellite. J. Geophys, Res., 98: 10725-10750, 1993.
  • Gault, W.A., G.G. Shepherd, W.E. Ward, C.H. Hersom, Y.J. Rochon, and B.H. Solheim, On-orbit performance of the WINDII instrument on UARS. Proceedings of the SPIE Conference on Optical Spectroscopic Techniques and Instrumentation for Atmospheric and Space Res. Vol 2266, San Diego, 1994.
Journal Articles and Study Reports:
  • G.G. Shepherd, G. Thuillier, B.H. Solheim, S. Chandra, L.L. Cogger, M.L. Duboin, W.F.J. Evans, R.L. Gattinger, W.A. Gault, M. Herse, A Hauchecorne, C. Lathuilliere, E.J. Llewellyn, R.P. Lowe, H. Teitelbaum and F. Vial, Longitudinal Structure in Atomic Oxygen Concentrations Observed with WINDII on UARS. Geophys. Res. Lett. 20: 1303-1306, 1993.
  • W.E. Ward, Y.J.Rochon, C. McLandress, D.Y. Wang, J.R. Criswick, B.H. Solheim, G.G. Shepherd. Correlations between the mesospheric O(1S) emission peak intensity and height and temperature at 98 km. using WINDII Data. Adv. Space Res. 14: 57-60, 1994.
  • W.F.J. Evans, L.R. Laframboise, and G.G. Shepherd, Mesospheric temperatures from Rayleigh scattering measurements by the WINDII instrument on UARS. Adv. Space Res. 14:285-288 (No. 9) 1994.
  • McLandress, C., Y. Rochon, G.G. Shepherd, B.H. Solheim, G. Thuillier, and F. Vial, The meridional wind component of the thermospheric tide observed by WINDII on UARS. Geophys. Res. Letts. 21: 2417-2420, (November) 1994.
  • G.G. Shepherd and C. McLandress Southern Hemisphere Dynamics Observed by WINDII: The WIND Imaging Interferometer on the UARS Mission. Adv. Space Res. 16: (5) 53-60, 1995.
  • Evans, W.F.J., L.R. Laframboise, K. R. Sine, R.H. Wiens, and G.G. Shepherd, Observation of polar mesospheric clouds in scattered sunlight by the WINDII instrument on UARS. Geophys. Res. Letts. 22: 2793-2796, 1995.
  • Wiens, R.H., W.F.J. Evans, D.Y. Liang, M.S. Zalcik, and A.H. Manson, WINDII Observation of a PMC breakup event during ANLC-93. Geophys. Res. Letts. 22: 2797-2800, 1995.
  • G. Hernandez, R.H. Wiens, R.P. Lowe, G.G. Shepherd, G.J. Fraser, R.W. Smith, L. LeBlanc, and M. Clark Optical determination of the vertical wavelength of propagating upper atmosphere oscillations. Geophys. Res. Letts., 22: 2389-2392, 1995.
  • Evaluation of the UARS Data, American Geophysical Union, Washington, DC, 1996.
Goddard DAAC IMS online documentation:

18. Glossary of Terms:

A collection of parameters packaged with associated ancillary and labeling data. Uniformly processed and formatted. Typically uniform temporal and spatial resolution.
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.).
A Granule is the smallest aggregation of data which is independently managed.

19. List of Acronyms:

CCD Charged Coupled Device
CDHF Central Data Handling Facility
DAAC Distributed Active Archive Center
DCF Data Capture Facility
EOS Earth Observing System
FOV Field of View
GSFC Goddard Space Flight Center
IMS Information Management System
K Kelvin
km kilometer
m meter
m/s meters per second
NASA National Aeronautics and Space Administration
PI Principal Investigator
RAC Remote Analysis Computer
SFDU Standard Formatted Data Units
WINDII Wind Imaging Interferometer
TDRSS Tracking and Data Relay Satellite System
UARS Upper Atmosphere Research Satellite

20. Document Information:

Document Revision Date:Fri May 10 11:54:32 EDT 2002

01 May 1997

Document Review Date:

01 May 1997

Document ID:


Document Curator:


Document URL:
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