MSFC SSM/I Grid and Swath Daily Products

IMPORTANT NOTICE: Due to the Navy's activation of a radiation/calibration beacon on the DMSP-F15 platform, the SSM/I 22V channel has become corrupted. This beacon was started on August 14, 2006. The corrupted 22V will affect all geophysical products which use it. This means the GHRC's IWV, CLW, and OWS (for F-15 only) are likely unusable, and will be discontinued from the time this beacon was activated. We're sorry for this inconvenience.

The Global Hydrology Resource Center (GHRC) is producing three distinct geophysical products from the Special Sensor Microwave Imager (SSM/I), using Wentz's Decode 4 Algorithm. From the brightness temperature swath data, the GHRC generates three geophysical products at swath and gridded resolutions. These three oceanic geophysical products are produced from data recorded by SSM/I measurements aboard the Defense Meteorological Satellite Program (DMSP) F-13, F-14, and F-15 satellites. Browse images of the gridded files are also created. The three oceanic geophysical products are:

• Integrated Water Vapor (IWV)
• Cloud Liquid Water (CLW)
• Oceanic Wind Speed (OWS)

Daily Swath Files From DMSP F13, DMSP F14, and DMSP F15

Integrated Water Vapor

Integrated water vapor is defined as the total amount of non-precipitating water vapor from the ocean surface to the top of the atmosphere. Where results are not attainable, the FNMOC surface code (negated) is assigned. For all three of the ocean products, the brightness temperature (Tb) data are read from the HDF Tb swath files and are then converted back to antenna temperatures (Ta) with the along-scan bias and satellite inter-calibration included. The Ta's are modified to include Wentz's radiative transfer model offsets. top

For each day, the swath data files (all ascending and all descending files) are created for each of the 3 geophysical products from the MSFC SMM/I brightness temperature swath files.

Cloud Liquid Water

Cloud liquid water is defined as the total amount of non-precipitating liquid water from the ocean surface to the top of the atmosphere. Where results are not attainable, the FNMOC surface code (negated) is assigned. Note, since the FNMOC code for land is zero, land codes are included with vegetated land codes and have a value of -1. For all three of the ocean products, the brightness temperature (Tb) data are read from the HDF Tb swath files and are then converted to antenna temperatures (Ta's) with the along-scan bias and satellite inter-calibration included. The Ta's are modified to include Wentz's radiative transfer model offsets.

For each day, the swath data files (all ascending and all descending files) are created for each of the 3 geophysical products from the MSFC SMM/I brightness temperature swath files. top

Oceanic Wind Speed

Oceanic wind speed is defined as the wind speed just above the ocean surface. Where results are not attainable the FNMOC surface code (negated) is assigned. Note, since the FNMOC code for land is zero, land codes are included with vegetated land codes and have a value of -1. For all three of the ocean products, the brightness temperature (Tb) data are read from the HDF Tb swath files and then are converted to antenna temperatures (Ta's) with the along-scan bias and satellite inter-calibration included. The Ta's are modified to include Wentz's radiative transfer model offsets.

For each day, the swath data files (all ascending and all descending files) are created for each of the 3 geophysical products from the MSFC SMM/I brightness temperature swath files. top

Daily Gridded Files From DMSP F13, DMSP F14, and DMSP F15

For each day, all of the swath files containing ascending swaths are averaged into a 0.5 x 0.5 degree global grid (720 x 360). The same is done for descending swaths. The global grid is centered on the Greenwich meridian. Each grid box value is the mean of the geophysical product values located within the half degree box centered at every xx.25 and xx.75 degrees. Only valid (positive) geophysical product values are used.

Daily Browse Images (HDF and GIF) From DMSP F13, DMSP F14, and DMSP F15

Browse files are created from daily gridded HDF products files. Two formats are used; GIF and HDF raster8. For each day the HDF raster8 file contains an image for both the ascending and descending orbits. For each day there are two GIF files created, one for the ascending and one for the descending orbit.

Both the HDF raster8 image and the GIF images are created from the HDF gridded data files. The images have been annotated. Also, the coastal boundaries have been color coded.

More details

DMSP F13 (START DATE: 1995-05-03 STOP DATE: Ongoing)
DMSP F14 (START DATE: 1997-05-10 STOP DATE: Ongoing)
DMSP F15 (START DATE: 2000-02-23 STOP DATE: 2006-08-13)

References:

Hollinger, J., et al., DMSP Special Sensor Microwave / Imager Calibration / Validation Final Report Volume I, Naval Research Laboratory, Washington, D. C.,20 July 1989.

Wentz, Frank J., Measurement of Oceanic Wind Vector Using Satellite Microwave Radiometers, IEEE Transactions on Geoscience and Remote Sensing, Vol. 30, No. 5, 5 September 1992.

Wentz, Frank J., User's Manual SSM/I Antenna Temperature Tapes Revision 1, RSS Technical Report 120191, Dec. 1, 1991, Remote Sensing Systems, Santa Rosa, CA.

Wentz, Frank J., User's Manual SSM/I Antenna Temperature Tapes Revision 2, RSS Technical Report 120193, Dec. 1, 1993, Remote Sensing Systems, Santa Rosa, CA.

NASA Information Contact: Michael Goodman, Global Hydrology and Climate Center GHRC Web Curator: GHRC Web Team Last update: Wednesday, 27-Sep-2006 16:20:37 CDT If you have trouble viewing or navigating this page, please contact GHRC User Services. U.S. Government Compliance report.