DMSP SATELLITE - SSM/I DATA Products

A. Numaguti (NIES, Japan)

Announced availability: 1 February 1996

Data Access

SSM/I data product collected from the Japanese WetNet for the COARE IOP are available via anonymous FTP from the University of Tokyo (ftp://ftp.ccsr.u-tokyo.ac.jp) in subdirectory pub/TOGA/satellite/SSMI-COARE.

Background

Defense Meteorological Satellite Program (DMSP)
Each DMSP satellite monitors the atmospheric, oceanographic and solar-geophysical environment of the Earth on a twice-daily basis. The visible and infrared sensors collect images of global cloud distribution across a 3,000-km swath during both daytime and nighttime conditions. The coverage of the microwave imager and sounders is one-half the visible and infrared sensors' coverage, thus they cover the polar regions above 60 on a twice-daily basis but the equatorial region on a daily basis. The space environmental sensors record along-track plasma densities, velocities, composition and drifts.

The DMSP program operates a two-satellite constellation, thus providing complete global coverage of clouds every six hours. High- resolution data are averaged, recorded and sent to ground receiving stations once an orbit (101 minutes). Local processing prepares orbital datasets organized as a time series, restores instrumental data that were adversely affected by the ionosphere during transmission, accurately computes and checks the satellite position and provides subpixel geolocation information and/or software.

SSM/I
The SSM/I is a seven-channel, four-frequency, linearly-polarized, passive microwave radiometric system which measures atmospheric, ocean and terrain microwave brightness temperatures at 19.35, 22.235, 37.0 and 85.5 GHz. The data are used to obtain synoptic maps of critical atmospheric, oceanographic and selected land parameters on a global scale. The SSM/I archive dataset consists of antenna temperatures recorded across a 1,400-km conical scan, satellite ephemeris, earth surface positions for each pixel and instrument calibration. Electromagnetic radiation is polarized by the ambient electric field, scattered by the atmosphere and the Earth's surface, and scattered and absorbed by atmospheric water vapor, oxygen, liquid water and ice.

The gridded data products derived from SSM/I microwave sensor are as follows: 


Variables  : Precipitation intensity  rra1 (mm/hr)
             Precipitable water       tpw2 (kg/m**2)
             Cloud liquid water       clw1 (g/m**2)
             Sea surface wind speed   mws1 (m/s)
             Surface type             lnd2
             Land surface temperature lst2

Grid       : Global latitude-longitude grid
             640x320 grid points
	     Longitude (1st.dimension)  - 180W -- +180E (0.5625 deg grid)
	     Latitude  (2nd.dimension)  +79.75N -- -79.75S (0.5deg grid)

Frequency  : Daily.
               * Ascending Orbit Composite
               * Descending Orbit Composite
               * Total Composite(composite of above two)
	     (Almost all regions are covered by Total Composite)

Period      : October 25, 1992 - March 6, 1993
	     (Missing data on January 2, 1993)

Data Format : PGM (Portable Graymap)

             Header Part: 640byte character
             Data Part:   640x320 1byte unsigned integer unformatted

             The integer value should be multiplied
             by an appropriate factor to obtain the value.
	     The factor is written in the Header.

             Precipitation intensity  rra1        1 (mm/hr)
             Precipitable water       tpw2      0.3 (kg/m**2)
             Cloud liquid water       clw1       10 (g/m**2)
             Sea surface wind speed   mws1      0.3 (m/s)
             Surface type             lnd2      0.1
             Land surface temperature lst2      0.1


Files       : rra1/rra1.92299a.Z   Ascending Orbit Composite
                   rra1.92299b.Z   Descending Orbit Composite
                   rra1.92299c.Z   All Orbit Composite

               PGM files

               rra1: name of variable
               92  : year
               299 : day of the year (counted from Jan.1)

	        Compressed by "compress"
	        Use "uncompress" or "zcat" to read.

             tpw2/
             clw1/
             mws1/
             lnd2/
             lst2/


             COMPO/
                Two week composite

	     92299/  WetNet original data (McIDAS format)
               :
             93059/
             SRC/    source program for conversion

Missing Values :
             land area (for tpw2 etc.) : 255
	     missing observation       : 254
             The value 242 in tpw2 is considered as missing value
             due to heavy rain.

How to READ :
	     Directly viewable by bitmap viewer such as
             "xv" and "xloadimage".
             Can be handled by "netpbm" or "pbmplus" package.

	     To read in FORTAN, unformatted direct access
             of recl=640 is suggested.
	     Data should be "uncompress"ed before use.

                   PARAMETER   (IPIXEL=640, JPIXEL=320)
                   CHARACTER*1  HX ( IPIXEL )
                   REAL         X  ( IPIXEL, JPIXEL )
                   CHARCATER    HF*32
             *
                   HF = 'rra1/rra1.92299a'
             *
                   OPEN(3,FILE=HF,FORM='UNFORMATTED',
                  "&"     ACCESS='DIRECT',RECL=IPIXEL )
             *
                   READ (3,REC=1) HX
             *
                   DO 100 J = 1, JPIXEL
                      READ (3,REC=J+1) HX
                      DO 110 I = 1, IPIXEL
                         X(I,J) = ICHAR(HX(I))
               110    CONTINUE
               100 CONTINUE


Data Source and History:
            March 1994. Imported from MO disk provided by WetNet program.
		        Converted to PGM (Numaguti)
                        Process All Orbit Composite (Numaguti)
For more information, please contact:

Atusi Numaguti
National Institute for Environmental Studies
16-2 Onogawa
Tsukuba, Ibaraki, 305
Japan

email: numaguti@nies.go.jp

Acknowledgement

Thanks to Dr. Kooiti Masuda who helped in obtaining the data. WetNet is a experimental project for world-wide data distribution to scientists at CCSR (Center for Climate System Research, Univ. of Tokyo) and their collaborators in Japan.

Return to Satellite Data Overview
Return to TOGA COARE Data User's Guide Table of Contents
Return to the COARE Homepage