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NCDC > Satellite Data > SSM/I and SSMIS Gridded Products

Binary Format Dataset Description

Data Type

4-byte floating point(binary) data.

Quality Control

Input data source is quality controlled prior to product generation at NOAA/NESDIS/STAR/CICS-MD/Satellite Climate Studies Branch.

Data Origin

The input data originates from the Defense Meteorological Satellite Program (DMSP), Special Sensor Microwave/Imager (SSM/I) instrument. A subsampled, 1/3 degree gridded daily archive of this data has been assembled by researchers at the NOAA/NESDIS/STAR. These daily fields are used as input to generate the monthly products.

Content Elements

One-Degree Products

The files have the following naming convention:

ppp.yy

where ppp=product type and yy=year (e.g., 87 for 1987).

Each field is stored as a 1440 byte record of 4-byte real variables which have been generated on a Windows based computer (see notes below regarding format issues when using on another platform). Each record contains 360 values corresponding to each degree of longitude, with the first element corresponding to longitude 0.5° East, the second 1.5° East, etc., and the last 0.5° West. The first record contains data centered at latitude 89.5° South, the second record contains data centered at 88.5° South, etc., and the last 89.5° North. Missing data are indicated by a value of -999.0.

The first 180 records in the data set correspond to January of that year, the next 180 is February, etc. The total length of each annual data set is 180*1440*12=3,110,400 bytes.

The following describes the content of the 1 degree gridded files:

  1. cfr.yy - Monthly mean cloud fraction (0 - 1.0)
  2. ice.yy - Monthly mean sea-ice cover (0 - 100 percent)
  3. lwp.yy - Monthly mean liquid water path (1000 * mm)
  4. pfr.yy - Monthly mean rain fraction (0 - 1.0)
  5. pre.yy - Monthly rainfall (mm)
  6. snw.yy - Monthly mean snow cover fraction (0 - 1.0 percent)
  7. ssa.yy - Monthly mean sampling fraction (0 - 1.0)
  8. win.yy - Monthly mean surface wind speed (m/sec)
  9. wvp.yy - Monthly mean total precipitable water (mm)

Period of Record is 1989 to present

2.5-Degree Products

Monthly Products

The files have the following naming convention:

ppp.mon

where ppp=product type.

Each field is stored as a 576 byte record of 4-byte real variables which have been generated on a personal computer. Each record contains 144 values corresponding to each 2.5° of longitude, with the first element corresponding to longitude 1.25° East, the second 2.5° East, etc. and the last 1.25° West. The first record contains data centered at latitude 88.75° South, the second record contains data centered at 86.25° South, etc. and the last 88.75° North. Missing data are indicated by a value of -999.0. Negative values in the pr1 and pr2 rainfall products denote indeterminate rainfall due to snow and ice cover; the absolute value indicates the fraction of ice/snow cover for the month.

The first 72 records in the data set correspond to January 1987, 72 is February 1987, etc. and the last 72 records correspond to December of the current year. The total length of each data set is 72*576*12*(# of years available....in 2002 # of years = 16)= total # of bytes.

The following describes the content of the 2.5° gridded files:

  1. cfr.mon - Monthly mean cloud fraction (0 - 1.0)
  2. lwp.mon - Monthly mean liquid water path (1000*mm)
  3. pf1.mon - Monthly mean rain fraction (0 - 1.0) using 85 GHz scattering algorithm over land, scattering/emission over ocean (ALG#1)
  4. pr1.mon - Monthly rainfall (mm) using ALG#1
  5. pf2.mon - Monthly mean rain fraction (0 - 1.0) using 37 GHz scattering algorithm over land, emission over ocean (ALG#2)
  6. pr2.mon - Monthly rainfall (mm) using ALG#2
  7. ssa.mon - Monthly mean sampling fraction (0 - 1.0)
  8. ice.mon - Monthly mean sea-ice cover (0 - 100 percent)
  9. snw.mon - Monthly mean snow cover fraction (0 - 1.0 percent)
  10. wvp.mon - Monthly mean total precipitable water (mm)

Period of Record

The data set begins in 1987 and is continually updated with current data. The first valid month of data is July 1987. Due to F8 instrument failure, there is no valid data for December 1987. There is no valid data for cfr, lwp, pf1, and pr1 for July 1990 - December 1991.

Pentad Products

The files have the following naming convention:

pppyy-f13-2.5.pen

where ppp=product type and yy=year (e.g.,87 for 1987).

Each field is stored as a 576 byte record of 4-byte real variables which have been generated on a personal computer. Each record contains 144 values corresponding to each 2.5° of longitude, with the first element corresponding to longitude 1.25° East, the second 2.5° East, etc. and the last 1.25° West. The first record contains data centered at latitude 88.75° South, the second record contains data centered at 86.25° South, etc. and the last 88.75° North. Missing data are indicated by a value of -999.0. Negative values in the pr1 and pr2 rainfall products denote indeterminate rainfall due to snow and ice cover; the absolute value indicates the fraction of ice/snow cover for the month.

The first 72 records in the data set correspond to the first pentad of the year, 72 to the second one, etc. and the last 72 records correspond to the last pentad of December of the given year. The total length of each data set is 72*576*73 (number of pentad in the year)= total # of bytes.

The following describes the content of the pentad 2.5° gridded files:

  1. cfryy-f13-2.5.pen - Pentad mean cloud fraction (0 - 1.0)>
  2. lwpyy-f13-2.5.pen - Pentad mean liquid water path (1000*mm)
  3. pf1yy-f13-2.5.pen - Pentad mean rain fraction (0 - 1.0) using 85 GHz scattering algorithm over land, scattering/emission over ocean (ALG#1)
  4. pr1yy-f13-2.5.pen - Pentad rainfall (mm) using ALG#1
  5. pf2yy-f13-2.5.pen - Pentad mean rain fraction (0 - 1.0) using 37 GHz scattering algorithm over land, emission over ocean (ALG#2)
  6. pr2yy-f13-2.5.pen - Pentad rainfall (mm) using ALG#2
  7. ssayy-f13-2.5.pen - Pentad mean sampling fraction (0 - 1.0)
  8. iceyy-f13-2.5.pen - Pentad mean sea-ice cover (0 - 100 percent)
  9. snwyy-f13-2.5.pen - Pentad mean snow cover fraction (0 - 1.0 percent)
  10. winyy-f13-2.5.pen - Pentad mean surface wind speed (m/sec)
  11. wvpyy-f13-2.5.pen - Pentad mean total precipitable water (mm)

Period of Record

Only the current year is available. Other periods are available under request

GPCP products

Each field is stored as a 576 byte record of 4-byte real variables which have been generated on a personal computer. Each record contains 144 values corresponding to each 2.5° of longitude, with the first element corresponding to longitude 1.25° East, the second 2.5:deg; East, etc. and the last 1.25° West. The first record contains data centered at latitude 88.75° South; the second record contains data centered at 86.25° South, etc. and the last 88.75° North. Missing data are indicated by a value of -999.0. Negative values in the pr1 and pr2 rainfall products denote indeterminate rainfall due to snow and ice cover; the absolute value indicates the fraction of ice/snow cover for the month.

The following describes the content of the gpcp 2.5° gridded files:

  1. gpcp_nesdis_pr1: Monthly rainfall using 85 GHz scattering algorithm over land, scattering/emission over ocean (ALG#1) for the early morning constellation (F8-F11 and F13)
  2. gpcp_nesdis_pr2: Monthly rainfall using 37 GHz scattering algorithm over land, emission over ocean (ALG#2) for the early morning constellation (F8-F11 and F13)
  3. gpcp_nesdis_f10_pr1: Monthly rainfall using 85 GHz scattering algorithm over land, scattering/emission over ocean (ALG#1) for the mid morning constellation (F10/14 and F15)
  4. gpcp_nesdis_f10_pr2: Monthly rainfall using 37 GHz scattering algorithm over land, emission over ocean (ALG#2) for the mid morning constellation (F10/14 and F15)
  5. gpcp_nesdis_dual_pr1: Monthly rainfall using 85 GHz scattering algorithm over land, scattering/emission over ocean (ALG#1) for the combination of both constellations
  6. gpcp_nesdis_dual_pr2: Monthly rainfall using 37 GHz scattering algorithm over land, emission over ocean (ALG#2) for the combination of both constellations

For products 1 and 2, the first 72 records in the data set correspond to January 1987, 72 are February 1987, etc. and the last 72 records correspond to December of the current year. The total length of each data set is 72*576*12*(# of years available since 1987) = total # of bytes. For the rest of the products, the first 72 records in the data set correspond to January 1992, 72 are February 1987, etc. and the last 72 records correspond to December of the current year. The total length of each data set is 72*576*12*(# of years available since 1992) = total # of bytes.

Period of Record:

The data set begins in 1987 and is continually updated with current data. The first valid month of data is July 1987. Due to F8 instrumental failure, there is no valid data for Decemeber 1987. There is no valid data for cfr, lwp, pf1, and pr1 for July 1990 - December 1991 for product 1 and 2. Products 3 to 6 begin in 1992 and are continually updated with current data.