GHRSST MUR v4.1¶

GHRSST Level 4 MUR Global Foundation Sea Surface Temperature Analysis, Version 4.1 (NASA JPL Multi-scale Ultra-high Resolution daily 0.01° foundation SST), plus the 0.25° MUR25 v4.2

Available

At a glance¶

Note on period: The first v4.1 file is dated 2002-06-01 (the catalog start is 2002-05-31 21:00 UTC). MUR25 v4.2 starts on 2002-09-01. The dt_1km_data variable appears from 2015-10-04, and sst_anomaly in v4.1 from 2019-07-23.

Overview¶

A global daily 0.01° (about 1 km) SST analysis produced at JPL by Dr. Toshio Chin's team under NASA's MEaSUREs program. It combines high-resolution infrared SST from MODIS (Aqua and Terra) and AVHRR, cloud-penetrating microwave SST from AMSR-E, AMSR2 and WindSat, and NOAA iQuam in situ data, relying on nighttime observations, and fills gaps with a Multi-Resolution Variational Analysis (MRVA) that uses wavelets as basis functions. Sea ice comes from EUMETSAT OSI SAF. Because the method keeps observations at their original locations instead of binning them to a grid first, MUR retains more fine-scale structure than other SST analyses. MUR25 (v4.2), a 0.25° version built with the same method, adds anomalies relative to a 2003–2014 MUR climatology and is convenient for long-term studies.

Available variables¶

Names follow the PO.DAAC variable table and file attributes. PO.DAAC originals are in kelvin, while the NOAA CoastWatch ERDDAP copies (jplMURSST41, jplMURSST42) are converted to °C. MUR25 v4.2 contains analysed_sst, analysis_error, mask, sea_ice_fraction and sst_anomaly, but not dt_1km_data.

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

Analysed SST (daily L4)¶

Ancillary fields¶

The full variable list is in the official documentation.

How to get the data¶

• NASA PO.DAAC — MUR v4.1 (MUR-JPL-L4-GLOB-v4.1) — Earthdata Search / earthaccess / OPeNDAP / Harmony subsetting / podaac-data-subscriber / direct AWS S3 access (us-west-2)
  • Requires a free NASA Earthdata Login. Each daily netCDF-4 file is about 300 MB, so subset small regions such as the Korean Peninsula with OPeNDAP or Harmony. The AWS Open Data entry (arn:aws:s3:::podaac-ops-cumulus-protected/MUR-JPL-L4-GLOB-v4.1/) also needs Earthdata credentials.
• NASA PO.DAAC — MUR25 v4.2 (MUR25-JPL-L4-GLOB-v04.2) — Earthdata Search / earthaccess / OPeNDAP / Harmony
  • The 0.25° version, with sst_anomaly (relative to 2003–2014) over the whole record. Earthdata Login required.
• NOAA CoastWatch ERDDAP — jplMURSST41 (0.01°) — ERDDAP griddap (regional and time subsets as netCDF, CSV and more; OPeNDAP) No login needed
  • No login needed. SST is converted to °C; on 2026-10-13 it ran through 2026-10-10. The 0.25° version is jplMURSST42.

Example code¶

Opens PO.DAAC files with earthaccess and clips the area around the Korean Peninsula. Run earthaccess.login() once with your NASA Earthdata account first. Files are large, so read only the region you need.

# pip install earthaccess xarray netCDF4 h5netcdf
import earthaccess
import xarray as xr

earthaccess.login()
results = earthaccess.search_data(
    short_name="MUR-JPL-L4-GLOB-v4.1",      # 0.25° version: MUR25-JPL-L4-GLOB-v04.2
    temporal=("2025-08-01", "2025-08-03"),
)
files = earthaccess.open(results)           # open without downloading

ds = xr.open_mfdataset(files, combine="by_coords")
sst = ds["analysed_sst"].sel(lat=slice(30, 40), lon=slice(120, 135)) - 273.15   # K -> °C, around Korea
print(sst.mean("time").values.mean())
print(ds["dt_1km_data"].sel(lat=slice(30, 40), lon=slice(120, 135)).max().values)  # max hours to an IR measurement

Practical tips¶

• Foundation SST excludes daytime warming, so on calm, clear summer afternoons it can be lower than satellite skin SST or near-surface buoy readings. Check depth and time definitions before comparing.
• A 0.01° grid does not mean 1 km features were observed every day. Infrared data are blocked by cloud, so use dt_1km_data (time to the nearest IR measurement) to see whether high-resolution data were present. Areas under persistent cloud are filled from microwave (about 25 km) data and look smoother.
• Recent days switch from near-real-time to retrospective files, and ERDDAP notes that the most recent 7 days are usually revised daily. Re-download recent data about a week later before finalising results.
• PO.DAAC originals are in kelvin and the CoastWatch ERDDAP copies in °C. Harmonise units when mixing files from different sources.
• Quality drops when inputs are missing. PO.DAAC reported that AMSR2 was excluded from 2022-12-17 to 2023-02-27, and that 2025-08-25 and 08-26 lost most high-resolution input and are very blurry (provided as is until reprocessed). Avoid these dates for case studies.
• sst_anomaly in v4.1 exists only from 2019-07-23 and uses a 2003–2014 baseline. Compute anomalies yourself from analysed_sst if you need a standard normal such as 1991–2020.
• PO.DAAC presents the much smaller MUR25 (0.25°) for long-term SST studies and large-scale analyses such as ENSO. Use the 0.01° version only when you need fine structure such as coastal fronts or eddies, and you will download far less.
• PO.DAAC has said there is no dedicated status page for MUR production. Delay and quality notices go out through the PO.DAAC mailing list, the announcements page and the Earthdata Forum.

Notices and change history¶

References for your paper¶

Dataset citation¶

MUR v4.1 (PO.DAAC) — DOI 10.5067/GHGMR-4FJ04

@misc{jplmur2015v41,
  author    = {{JPL MUR MEaSUREs Project}},
  title     = {{GHRSST} Level 4 {MUR} Global Foundation Sea Surface Temperature Analysis. Ver. 4.1},
  year      = {2015},
  publisher = {NASA Physical Oceanography Distributed Active Archive Center},
  version   = {4.1},
  doi       = {10.5067/GHGMR-4FJ04}
}

MUR25 v4.2 (PO.DAAC) — DOI 10.5067/GHM25-4FJ42

@misc{jplmur2019mur25,
  author    = {{JPL MUR MEaSUREs Project}},
  title     = {{GHRSST} Level 4 {MUR} 0.25 deg Global Foundation Sea Surface Temperature Analysis. Ver. 4.2},
  year      = {2019},
  publisher = {NASA Physical Oceanography Distributed Active Archive Center},
  version   = {4.2},
  doi       = {10.5067/GHM25-4FJ42}
}

Reference papers¶

MUR analysis method (citation requested by PO.DAAC) — DOI 10.1016/j.rse.2017.07.029

@article{chin2017mur,
  author  = {Chin, Toshio Michael and Vazquez-Cuervo, Jorge and Armstrong, Edward M.},
  title   = {A multi-scale high-resolution analysis of global sea surface temperature},
  journal = {Remote Sensing of Environment},
  volume  = {200},
  pages   = {154--169},
  year    = {2017},
  doi     = {10.1016/j.rse.2017.07.029}
}

Acknowledgements¶

The file attributes ask users to acknowledge the data with "These data were provided by JPL under support by NASA MEaSUREs program." Following the PO.DAAC citation guidelines (https://podaac.jpl.nasa.gov/CitingPODAAC), cite the DOI of the version you actually used (v4.1 or MUR25 v4.2).

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¶

• PO.DAAC — MUR v4.1 dataset page
• PO.DAAC — MUR25 v4.2 dataset page
• PO.DAAC — MUR project overview (MEaSUREs-MUR)
• GHRSST Data Specification GDS 2.0 (PDF)
• Chin et al. (2017), Remote Sensing of Environment
• On this site — OSTIA (Met Office 0.05° foundation SST analysis)
• On this site — NOAA OISST v2.1 (0.25° daily analysis)
• On this site — ESA SST CCI (satellite-only SST climate data record)
• On this site — AVHRR Pathfinder SST (discontinued 4 km satellite SST)