RSS SSM/I·SSMIS¶

Remote Sensing Systems (RSS) DMSP SSM/I and SSMIS Ocean Products, Version 7

Discontinued

At a glance¶

Note on period: SSM/I and SSMIS on F08 (1987-07 to 1991-12), F10 (1990-12 to 1997-11), F11 (1991-12 to 2000-05), F13 (1995-05 to 2009-11), F14 (1997-05 to 2008-08), F15 (1999-12 onward; not for climate studies after August 2006), F16 (2003-10 onward), F17 (2006-12 onward) and F18 (2009-10 onward). F19 (2014-04 to 2016-02) is not held by RSS. As checked on 2026-10-13 the last daily files for F16, F17 and F18 are for 2026-09-30.

Overview¶

A 0.25° gridded product in which RSS processes DMSP SSM/I and SSMIS microwave brightness temperatures with a single physically based algorithm to retrieve, over the ocean, 10 m wind speed, total precipitable water (columnar water vapour), cloud liquid water and rain rate together. SSMIS brightness temperatures are intercalibrated to the earlier SSM/I level, giving a nearly 40-year record from 1987 that has long been used for ocean water-vapour trends, surface winds, precipitation and reanalysis validation. Version 7 files are produced separately for each satellite from F08 to F18, and updates stopped with the end of DMSP data supply in September 2026.

Available variables¶

Names are those used by the RSS bytemap reader (ssmis_daily_v7.py). RSS originals are stored as integers 0–250 that must be scaled (and offset), and 251–255 are special codes. Variable names inside the GHRC netCDF files were not verified; check them in your files.

instantaneous mean accumulated maximum minimum static — instantaneous: value at the time stamp · mean/accumulated/maximum/minimum: over the indicated interval · static: does not change with time

Daily (by morning/evening pass)¶

3-day, weekly and monthly means¶

The full variable list is in the official documentation.

How to get the data¶

• RSS data server (bytemaps per satellite; daily, 3-day, weekly, monthly) — Direct HTTPS download (gzipped binary, e.g. f17/bmaps_v07/y2026/m09/f17_20260930v7.gz)
  • F18 is in the bmaps_v08 folder (file names with v8). Readers (Python, IDL, Matlab, Fortran, C++) are in the ssmi_support folder. FTP access needs free registration.
• NASA GHRC DAAC — RSS SSM/I and SSMIS Ocean Product Grids netCDF V7 — Earthdata Search / earthaccess / OPeNDAP (netCDF-4)
  • One collection per satellite and time step (e.g. F17 daily rssmif17d, 3-day rssmif17d3d, weekly rssmif17w, monthly rssmif17m; F16 is rssmif16*; SSM/I satellites such as F13 and F15 are also available). No F18 collection was found when checked in October 2026. A free NASA Earthdata login is required.
• RSS SSM/I and SSMIS description page — Web (format, scaling, codes and citation)

Example code¶

Downloads GHRC netCDF with earthaccess. Run earthaccess.login() once with a NASA Earthdata account, and check the variable names with print(ds) first.

# pip install earthaccess xarray netCDF4
import earthaccess
import xarray as xr

earthaccess.login()
results = earthaccess.search_data(
    short_name="rssmif17m",          # F17 SSMIS monthly means (daily is rssmif17d)
    version="7",
    temporal=("2025-01-01", "2025-12-31"),
)
files = earthaccess.download(results[:1], "./rss_ssmis")

ds = xr.open_dataset(files[0])
print(ds)                            # check variable names, scaling and fill attributes

Practical tips¶

• RSS bytemaps must be scaled — multiply wind by 0.2, vapour by 0.3, rain by 0.1, and cloud by 0.01 then add -0.05. Codes 251 (wind or vapour missing due to rain), 252 (sea ice), 253 (bad data), 254 (no observation) and 255 (land) are not values.
• Wind speed is missing or unreliable in rain, sun glint, radio-frequency interference and within about 50 km of coasts and sea ice. Most winds under rain are dropped, so samples are biased toward clear conditions.
• Cloud liquid water allows small negative values (down to -0.05 mm) so that noise averages out; do not clip them to zero.
• RSS advises against using F15 for climate studies after August 2006. For long-term trends, compare satellites while allowing for their different crossing times and orbit changes.
• From 2025 DMSP SSMIS data were delivered only on a best-effort basis, causing missing days. Check daily gaps before using 2025–2026 values.
• F18 files are posted in the bmaps_v08 folder with v8 in the name, while the RSS description page and citation cover Version 7 only. When using F18, report the version in the file names exactly.
• The daily time variable is UTC. Mixing morning and evening passes in an average can bias quantities with a strong diurnal cycle, such as rain and cloud.

Notices and change history¶

References for your paper¶

Dataset citation¶

RSS SSM/I and SSMIS 0.25° products (RSS recommended citation)

@misc{wentz2012rssssmi,
  author       = {Wentz, Frank J. and Hilburn, Kyle A. and Smith, Deborah K.},
  title        = {Remote Sensing Systems {DMSP} {SSM/I} and {SSMIS} Environmental Suite on 0.25 deg grid, Version 7},
  year         = {2012},
  publisher    = {Remote Sensing Systems},
  address      = {Santa Rosa, CA},
  howpublished = {\url{https://www.remss.com/missions/ssmi}},
  note         = {Accessed DD MMM YYYY}
}

GHRC netCDF collection (V7) — DOI 10.5067/MEASURES/SSMI-SSMIS/DATA301

@misc{wentz2012ghrcssmi,
  author    = {Wentz, Frank J. and Hilburn, Kyle and Smith, Deborah K.},
  title     = {{RSS} {SSM/I} and {SSMIS} Ocean Product Grids {netCDF} Data Collection Version 7},
  year      = {2012},
  publisher = {NASA Global Hydrometeorology Resource Center Distributed Active Archive Center},
  doi       = {10.5067/MEASURES/SSMI-SSMIS/DATA301}
}

Reference papers¶

SSM/I ocean retrieval algorithm — DOI 10.1029/96JC01751

@article{wentz1997ssmi,
  author  = {Wentz, Frank J.},
  title   = {A well-calibrated ocean algorithm for special sensor microwave / imager},
  journal = {Journal of Geophysical Research: Oceans},
  volume  = {102},
  number  = {C4},
  pages   = {8703--8718},
  year    = {1997},
  doi     = {10.1029/96JC01751}
}

Microwave rain retrieval (UMORA) — DOI 10.1175/2007JAMC1635.1

@article{hilburn2008umora,
  author  = {Hilburn, Kyle A. and Wentz, Frank J.},
  title   = {Intercalibrated Passive Microwave Rain Products from the Unified Microwave Ocean Retrieval Algorithm ({UMORA})},
  journal = {Journal of Applied Meteorology and Climatology},
  volume  = {47},
  number  = {3},
  pages   = {778--794},
  year    = {2008},
  doi     = {10.1175/2007JAMC1635.1}
}

Acknowledgements¶

RSS asks for an acknowledgement such as "SSM/I and SSMIS data are produced by Remote Sensing Systems. Data are available at www.remss.com/missions/ssmi.", and asks users to tell RSS User Support the journal and expected publication date of papers using the data (this helps sustain funding for the products).

Information on the datasets used in this study was compiled with the help of the Korean Climate Data Navigator (KCDN) (Sim, 2026; https://doi.org/10.5281/zenodo.23300923).

Links¶

• RSS — SSM/I and SSMIS data description
• RSS — equator crossing times by satellite
• RSS — terms of data use
• RSS announcements
• EUMETSAT OSI SAF — implications of the end of SSMIS data for its products