International Satellite Cloud Climatology Project (ISCCP) DX Data

Spatially and Temporally Subsetted for TOGA COARE

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1. GENERAL INFORMATION

The ISCCP DX data set consists of analyses of data acquired from the GMS-4 satellite and the NOAA 11 and 12 satellites in support of the Tropical Ocean Global Atmosphere-Coupled Ocean Atmosphere Response Experiment (TOGA-COARE). Principal Investigator William B. Rossow of the Goddard Institute for Space Studies (GISS) has subsetted this data set both temporally and spatially to conform to the TOGA COARE period and region.

The production and distribution of this data set are being funded by NASA's Mission To Planet Earth Program. The data are not copyrighted, however we request that when you publish data or results using these data, please acknowledge as follows:

The authors would like to thank the International Satellite Cloud Climatology Project (ISCCP), Goddard Institute for Space Studies and the Distributed Active Archive Center (Code 610.2) at the Goddard Space Flight Center, Greenbelt, MD 20771 for the production and distribution of these data, respectively. These Activities are sponsored by NASA's Earth Science Enterprise.

1.1 Temporal Coverage and Resolution. All times are in GMT. The temporal coverage for the TOGA COARE campaign and for this ISCCP subset is 4 months from November 1, 1992 through February 28, 1993. The sampling interval for these data is 3hr for GMS4 and 12 hr for each NOAA polar orbiter.

1.2 Spatial Coverage and Resolution. The ISCCP subsets for the TOGA COARE campaign cover the region:

       Longitude:  120 E --> 10 W 
       Latitude:   20 S --> 20 N

The spatial resolution is about 30 km for sensors on all 3 satellites.

2. INSTRUMENT INFORMATION

2.1 ISCCP Science Objectives

Investigation of the role of clouds in climate involves a complex interrelated study of many different processes and addresses many different questions. The ISCCP's scientific objectives are:

To produce a global, reduced resolution, infrared and visible, calibrated and normalized radiance data set containing basic information on the radiative properties of the atmosphere from which cloud parameters can be derived
To stimulate and coordinate basic research on techniques for inferring the physical properties of clouds from the condensed radiance data set and to apply the resulting algorithms to derive and validate a global cloud climatology for improving the parameterization of clouds in climate models
To promote research using ISCCP data and contributing to improved understanding of the Earth's radiation budget (top of atmosphere and surface) and hydrological cycle.

2.2 General Description

This analysis is based on data from the GMS4, NOAA 11 and NOAA 12 satellites.

GMS4 (Geostationary Meteorological Satellite):: Operated by the Japan Meteorological Agency (JMA), GMS is a spin-stabilized spacecraft maintained at 140E longitude. Imaging data are from the Visible Infrared Spin-Scan Radiometer (VISSR), with high resolution (1.25 km) visible images obtained by four identical detectors scanning in parallel. The spin-scan is from west to east and from north to south.; The NOAA TIROS-N series satellites are three-axis stabilized in 850 KM (nominal) circular, near-polar, sun-synchronous orbits with an inclination angle of ~99 degrees (retrograde) to the equator. Orbital period is about 102 minutes. Sequential orbits observe adjacent longitudes near the equator and provide overlapping coverage in both polar regions. The instrument complement is as follows
NOAA 11:: - AVHRR, 5 channels; - HIRS/2, 20 channels; - MSU, 4 channels; - SSU, 3 channels
NOAA 12:: - AVHRR, 5 channels; - HIRS/2, 20 channels; - MSU, 4 channels; - SBUV

3. DATA ORGANIZATION

3.1 General Characteristics

ISCCP DX data is the individual pixel-level results of the analysis that contains the visible and IR radiances, the clear-sky radiances, the surface reflectance and temperature from the clear-sky radiances, the cloud detection decision, and the retrieved physical quantities. For clear pixels these are the surface reflectance and temperature; for cloudy pixels these are the cloud top temperature/pressure and optical thickness. The cloud top temperature is obtained with three different models: assuming an opaque cloud (all times of day), assuming a liquid water cloud or an ice cloud (daytime).

The ISCCP DX TOGA COARE subset totals 2129 data files and is about ~1.07 GB in volume. Each file contains data for one GMT. Files are named 'subDX.VSSSSP.YYMMDDHH' where 'subDX' indicates that this is a subset of the full ISCCP DX dataset, 'V' is the version number, 'SSSSP' indicates the satellite (GMS4, NOAB = NOAA-11, NOAC = NOAA-12) and the global sector (for GMS4, NOAB and NOAC, P = B or E representing the ascending or descending orbits), YY=92, 93 (year), MM=11, 12, 1, 2 (month), DD=01, 02,.., 31 (date) and HH=00, 03, .. 21 (GMT).

3.1.1 Flight coordination table. The following table relating ER-2 and DC-8 flight numbers to the dates of the 13 mission flights of the NASA/TOGA COARE campaign provides correlation with airborne data acquisition activities during the TOGA COARE intensive operating period. The mission objective for each mission flight defaulted to radiation unless convection was forecast in the target area.

Date(UTC)       ER-2 Flight     DC-8 Flight     Objective
---------------------------------------------------------
Jan 11-12       93-053          93-01-06        Radiation
Jan 17-18       93-054          93-01-07        Convection
Jan 18-19       93-055          93-01-08        Convection
Jan 25-26       93-056          93-01-09        Radiation
jan 31-Feb 1    93-057          93-01-10        Radiation
Feb 4           93-060          93-01-11        Convection
Feb 6                           93-01-12        Convection
Feb 7           93-061                          
Feb 8-9         93-062          93-01-13        Convection
Feb 10-11       93-063          93-01-14        Convection
Feb 17-18                       93-01-15        Convection
Feb 20-21       93-065          93-01-16        Convection
Feb 22-23       93-066          93-01-17        Convection
Feb 23-24       93-067          93-01-18        Radiation

3.2 Data Format

There are a variable number of data records in each DX image. Each record contains packed binary pixel data as folows:

    I*4   IWEST   Western-most longitude (0-3600 degrees*10)         
    I*4   IEAST   Eastern-most longitude (0-3600 degrees*10)          
    I*4   INORTH  Northern-most latitude (0-1800 degrees*10)          
    I*4   ISOUTH  Southern-most latitude (0-1800 degrees*10)          
    I*4   NPIX    Number of pixels                                    
    I*4   IOUT    Number of bytes in packed data BUFFER               
    I*2   LONBUF(NPIX) Longitudes for NPIX pixels (0-3600 degrees*10) 
    I*2   LATBUF(NPIX) Latitudes for NPIX pixels (0-1800 degrees*10)  
    I*2   XBUF(NPIX)  X-positions for NPIX pixels (1-1440)            
    I*2   YBUF(NPIX)  Y-positions for NPIX pixels (1-550)             
    I*1   BUFFER(IOUT) Packed data for NPIX pixels                    
    remainder of record is filled with I*1 255 values.               

The contents of the buffer as it is unpacked are as follows:

NOTE 1:  Numbers on the left identify the byte number from 1 to 32.  This is 
the MAXIMUM number of bytes that a pixel can have.  Not all bytes are present 
for all pixels.

DATA SECTION 1 - pixel ident. satellite angle, IR cloud detection  

1. NODAY,BXSHOR,LNDWTR,HITOPO,SNOICE,TIMSPA (N,B,L,H,SS,TT)         
     *NODAY  : BX day/night flag (0-1), 1 = day sect. 2,4 not present 
     *BXSHOR : BX shore flag (0-1), 1 = shore pixel                   
      LNDWTR : Land/water flag (0-1), 1 = water pixel                 
      HITOPO : Topography flag (0-1), 1 = high topography pixel       
      SNOICE : Snow/ice code (0-3)                                    
     *TIMSPA : Time/space test result (0-3)                           

2. ICSLOG,BXITHR (IIIII,BBB)                                         
     *ICSLOG : IR clear sky composite logic code (0-24)              
     *BXITHR : BX IR threshold result ()-5)                          

3. MUE       : Cosine of satellite angle * 100 (0-100)               

4. IRAD      : IR radiance (0-254 ct)                                 

5.*BXICSR    : BX IR clear sky radiance (0-254 ct)                    
  If image header says additional channels are present (BXADDL>0) then:   

6. ARAD(1)   : First additional channel radiance (0-254 ct)        

7. ARAD(2)   : Second additional channel radiance (0-254 ct)       

8. ARAD(3)   : Third additional channel radiance (0-254 ct)         
                                                                     
DATA SECTION 2 - sun angles, VIS cloud detection                     
 if NODAY = 0 (day sections present) then:                           

9. GLINT,VCSLOG,BXVTHR (G,VVVV,BBB)                                  
      GLINT  : Glint flag (0-1), 1 = glint condition exists          
     *VCSLOG : VIS clear sky composite logic code (0-14)             
     *BXVTHR : BX VIS threshold result                              

10. MU0       : Cosine of sun angle * 100 (0-100)                    

11. PHI       : Relative azimuth angle (0-180 degrees)                

12. VRAD      : VIS radiance (0-254 ct)                               

13.*BXVCSR    : BX VIS clear sky radiance (0-254 ct)                  
                                                                     
DATA SECTION 3 - adjusted cloud detections, IR retrievals,          
                  additional channel cloud detections                

14. DAYNIT,ITHR,VTHR,SHORE (D,III,VVV,S)                             
       DAYNIT : Day/night flag (0-1), 1 = night pixel (no VIS retrieval
       ITHR   : IR threshold result (0-5)                             
       VTHR   : VIS threshold result (0-5)                            
       SHORE  : Shore flag (0-1), 1 = shore pixel                    

15. IRET,ICSRET (IIII,IIII)                                           
      *IRET   : IR retrieval code (0-12)                              
      *ICSRET : IR clear sky composite retrieval code (0-12)          


16. ICSRAD    : IR clear sky composite radiance (0-254 ct)           

17. ITMP      : IR retrieved cloud top or surface temperature (0-254 ct)

18. IPRS      : IR retrieved cloud top pressure (0-254 ct)           

19. ICSTMP    : IR retrieved clear sky composite temperature (0-254 ct)

20. ICSPRS    : IR retrieved clear sky composite pressure (0-254 ct)
 if image header says is polar (SATTYP = 1,2,or -3) then:            

21. NREF      : NI reflectivity (NOAA channel 3) (0-254 ct)          

22. NTHR      : NI threshold result (NOAA channel 3) (0-254 ct)      

23. NCSREF    : NI clear sky composite reflectance (NOAA channel 3) 
                                                                    
 DATA SECTION 4 - VIS retrievals                                     
 if NODAY = 0 (day sections present) then:                           
 if DAYNIT = 1 (night, no VIS retrievals) these will all be 255     

24. VRET,VCSRET (VVVV,VVVV)                                           
      *VRET   : VIS retrieval code (0-14)                            
      *VCSRET : VIS clear sky composite retrieval code (0-14)        

25. VCSRAD    : VIS clear sky composite radiance (0-254 ct)          

26. VALBTA    : VIS retrieved cloud tau or surface albedo (0-254 ct)

27. VCSALB    : VIS retrieved clear sky composite albedo (0-254 ct)  

28. VTMP      : VIS adjusted cloud top temperature (0-254 ct)       

29. VPRS      : VIS adjusted cloud top pressure (0-254 ct)           

30. VTAUIC    : VIS retrieved ice cloud tau (0-254 ct)              

31. VTMPIC    : VIS retrieved ice cloud top temperature (0-254 ct)   

32. VPRSIC    : VIS retrieved ice cloud top pressure (0-254 ct)

4. DATA ACCESS

4.1 Online

Access ISCCP DX images online

4.3 Software

Fortran 77 program DXREAD.f was provided by the data producer to read the ISCCP DX files. This software is copiously documented and complete except for output statements which should be supplied by the user to extract the desired parameters. It compiles and runs without modification on the DAAC's SGI equipment under IRIX 4.0.5C.

5. DATA QUALITY ASSESSMENT

The ISCCP DX is an analyzed, gridded data set. Consult Reference 4 for quality information.

6. POINTS OF CONTACT

For NASA/TOGA COARE user services contact:

Edee Ocampo
GES DISC
Code 610.2
NASA Goddard Space Flight Center
Greenbelt, MD 20771

Edee.Ocampo@nasa.gov
        (301)  614-5376 (voice)
        (301)  614-5268 (Fax)

For detailed information about the data analysis, contact:

      Principal Investigator:  
	W. Rossow
        Goddard Institute for Space Studies
	2880 Broadway
	New York, NY 10025

wrossow@giss.nasa.gov
	(212) 678-5567 (voice)

For ISCCP data processing information, contact:

	Angel L. Suarez
	Goddard Institute for Space Studies
	2880 Broadway
	New York, NY 10025

asuarez@giss.nasa.gov
	(212) 678-5518 (voice)

7. DATA STATUS AND PLAN

The TOGA COARE ISCCP data is part of the Goddard DAAC's permanent field campaign archive.

8. REFERENCES

TOGA COARE Science Data Workshop II Proceedings, March 15-17, 1994, page 4.
NOAA Polar Orbiter Data Users Guide, U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Environmental Satellite Data and Information Service, National Climatic Data Center, Satellite Data Service Division, December 1991.
WMO/TD-No. 58: The International Satellite Cloud Climatology Project (ISCCP) Description of Reduced Resolution Radiance Data, July 1985 (Revised august 1987), World Meteorological Organization, Geneva.
WMO/TD-No, 266: International Satellite Cloud Climatology Project (ISCCP) Documentation of Cloud Data, December 1988 (Revised April 1991). World Meteorological Organization, Geneva.

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