PranavKonijeti/viirs-sst-daily-nrt

VIIRS/SNPP Daily Sea Surface Temperature — 4 km, Near-Real-Time

Daily global sea surface temperature from the VIIRS instrument aboard Suomi-NPP, Level-3 Standard Mapped Image at 4 km, as distributed by the NASA Ocean Biology Processing Group. This is the near-real-time (NRT) feed — produced within hours of acquisition, with preliminary calibration.

If you are training a model or computing a trend, use the science-quality feed instead: PranavKonijeti/viirs-sst-daily-nonNRT. See Which feed should I use?.

At a glance

Coverage	2019-10-01 → 2026-07-07
Files	2,438 daily granules (.nc)
Size	30.2 GB
Grid	4320 lat × 8640 lon, global, equirectangular
Resolution	4.64 km nominal (~0.0417°), daily
Variable	sst, degrees Celsius
Missing days	34 of 2,472 (1.4%) — see Gaps

Files

One netCDF-4 file per day, named:

SNPP_VIIRS.YYYYMMDD.L3m.DAY.SST.sst.4km.NRT.nc

Note the .NRT suffix — this is what distinguishes these filenames from the science-quality granules.

Each file contains:

variable	description
sst	Sea surface temperature, degree_C, stored as scaled int16
qual_sst	Per-pixel quality flag (lower is better; 0 is best)
lat, lon	Coordinate axes
palette	Display colour table (not data)

Land, cloud, and retrieval failures are NaN after decoding. Typically ~70–85% of the grid is NaN on any given day — most of the planet is either land or under cloud, so expect sparse coverage per file.

Usage

from huggingface_hub import snapshot_download

path = snapshot_download(
    repo_id="PranavKonijeti/viirs-sst-daily-nrt",
    repo_type="dataset",
    local_dir="./sst_nrt",
)

To pull a single year instead of all 30 GB:

snapshot_download(
    repo_id="PranavKonijeti/viirs-sst-daily-nrt",
    repo_type="dataset",
    allow_patterns="SNPP_VIIRS.2024*.nc",
    local_dir="./sst_2024",
)

Reading one day:

import xarray as xr

ds = xr.open_dataset("SNPP_VIIRS.20240104.L3m.DAY.SST.sst.4km.NRT.nc")
sst = ds["sst"]            # (lat, lon), degrees Celsius, NaN where no retrieval

sst is stored as scaled int16; xarray decodes it to floating-point Celsius automatically. With a lower-level netCDF library, apply scale_factor and add_offset yourself.

Which feed should I use?

	this repo (NRT)	science repo
Latency	Hours	Days to weeks
Calibration	Preliminary	Final, reprocessed
Coverage here	2019-10-01 → 2026-07-07	2012-01-19 → 2026-05-31
Best for	Recent conditions, low-latency monitoring	Training, climatology, trend analysis

NRT is optimised for speed, not accuracy. Its calibration is preliminary and the underlying granules can be reprocessed later, so values for a given date may change retroactively and are not guaranteed stable. That makes this feed a poor basis for model training, climatology, or any trend estimate — a shifting calibration is indistinguishable from a real signal.

Use it for what it is good at: the most recent days, where the science feed has not caught up yet. Note this repository extends to 2026-07-07, later than the science repository's 2026-05-31, which is exactly the latency gap NRT exists to fill.

The two feeds overlap from October 2019 onward. The same date will appear in both with slightly different values — expected, not an error. Do not mix them in a single time series without accounting for the calibration difference.

Gaps and missing data

Days are not contiguous. 34 of the 2,472 days in the span have no file, from instrument downtime, processing gaps, or granules that failed download. Do not assume file n+1 is the day after file n — parse the date from the filename.

Within any given file, per-pixel gaps from cloud and land are the norm.

Provenance

Downloaded from the NASA Ocean Biology Processing Group's distribution server at oceandata.sci.gsfc.nasa.gov. Files are unmodified as distributed — no resampling, reprojection, or filtering was applied.

• Platform: Suomi-NPP · Instrument: VIIRS · Processing level: L3 Mapped
• Producer: NASA/GSFC/OBPG
• Title as distributed: VIIRSN Level-3 Standard Mapped Image

This repository is a convenience mirror. For authoritative or current versions of this product, go to the source above.

License and citation

Distributed under the NASA Earth Science Data and Information Policy, as recorded in each file's license global attribute. NASA Earth science data are open; attribution to NASA/GSFC/OBPG is expected.

If you use this data, cite the NASA Ocean Biology Processing Group rather than this mirror:

NASA Ocean Biology Processing Group. Visible and Infrared Imager/Radiometer Suite (VIIRS) Level-3 Mapped Sea Surface Temperature Data, Suomi-NPP. NASA Ocean Biology Distributed Active Archive Center. https://oceandata.sci.gsfc.nasa.gov

Notes

The dataset viewer is not available here — HF renders Parquet and similar tabular formats, and these are raw netCDF grids. Use xarray as shown above.