Earth Data School
About
Full catalog/SWOT_L2_NALT_GDR_D
SWOT_L2_NALT_GDR_D·vD·dataset

Sea and lake surface height, version D (SWOT altimeter)

SWOT Level 2 Nadir Altimeter Geophysical Data Record with Waveforms Version D
ocean NASA POCLOUD Level 2 netCDF-4
In plain English

What it measures. Sea surface height measured directly beneath the satellite, plus wave height and wind speed, recorded as points along the flight track.

How it's made. Collected by the Poseidon-3C radar altimeter on the NASA/CNES SWOT satellite; this 'Version D' uses precise final orbit information and is released within about 90 days.

How & where you'd use it. Used to study ocean surface topography and map inland water bodies; the longer processing time makes this the more accurate counterpart to the quick interim version.

What's measured

OCEANS › SEA SURFACE TOPOGRAPHY › SEA SURFACE HEIGHTOCEANS › OCEAN WAVES › SIGNIFICANT WAVE HEIGHT

Coverage & cadence

  • Time span2022-12-16 → ongoing
  • Measured bySWOT (Jason-class Altimeter, AMR)
  • Processing levelLevel 2
  • Spatial extent-180, -77.6, 180, 77.6
  • FormatsnetCDF-4
  • StatusACTIVE

What you can do with it

  • Watch sea-surface temperature and marine heatwaves
  • Spot algal blooms and ocean-colour shifts
  • Support fisheries and coastal monitoring
Official description

The SWOT Level 2 Nadir Altimeter Geophysical Data Record (GDR) with Waveforms dataset produced by the Surface Water and Ocean Topography (SWOT) mission provides sea surface height, significant wave height and wind speed measurements from the Poseidon-3C nadir altimeter, a Jason-class dual frequency (Ku/C) altimeter. SWOT is a joint mission between NASA and CNES that launched on December 16, 2022. It aims to measure ocean surface topography with unprecedented resolution and accuracy, as well as map inland water bodies globally. The GDR dataset consists of discrete measurements for each half orbit along the ground track with sampling resolutions of approximately 6-km and 300-m at 1Hz and 20Hz, respectively. The data were processed using restituted auxiliary data and the Precise Orbit Ephemeris (POE). The data are available with latency of < 90 days and distributed in netCDF-4 file format. This collection is the parent collection to the following sub-collections: https://podaac.jpl.nasa.gov/dataset/SWOT_L2_NALT_GDR_SSHA_D https://podaac.jpl.nasa.gov/dataset/SWOT_L2_NALT_GDR_GDR_D https://podaac.jpl.nasa.gov/dataset/SWOT_L2_NALT_GDR_SGDR_D

Get the data

swot_l2_nalt_gdr_d_access.py
import earthaccess
earthaccess.login(strategy="netrc")          # free Earthdata Login

results = earthaccess.search_data(
    short_name="SWOT_L2_NALT_GDR_D",
    version="D",
    bounding_box=(-122.5, 37.2, -121.8, 37.9),  # your area (W,S,E,N)
    temporal=("2024-01-01", "2024-12-31"),       # your dates
)
files = earthaccess.open(results)   # stream straight from POCLOUD
Browsing CMR needs no login. Downloading or streaming bytes needs a free Earthdata Login + the earthaccess package.