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Download and read Swot from AVISO

This notebook demonstrates how to browse and download SWOT LR data available on AVISO using the Altimetry Downloader Aviso tool.

Tutorial Objectives

• Explore products from AVISO using the altimetry_downloader_aviso

• Download a product using the altimetry_downloader_aviso

• Subset L3 Usnmoothed product using the altimetry_downloader_aviso

• Open data using altimetry.io

Note

Required environment to run this notebook:

• altimetry_downloader_aviso: see documentation.

• altimetry.io: available here.

• xarray

Import + code

import logging
logging.basicConfig(level=logging.INFO)

from pathlib import Path
import altimetry_downloader_aviso as dl_aviso

Parameters

Define an output folder to save results

output_dir= Path.home() / "TMP_DATA"

Discover Aviso’s products

Use the summary and details commands to discover Aviso’s catalog products.

cat = dl_aviso.summary()

INFO:altimetry_downloader_aviso.catalog_client.client:Fetching products from Aviso's catalog...

for product in cat.products:
    print(f"{product.short_name} -> {product.title}")

SWOT_L2_LR_SSH_Basic -> Altimetry product SWOT Level-2 KaRIn Low Rate SSH - Basic
SWOT_L3_LR_SSH_Basic -> Altimetry product SWOT Level-3 Low Rate SSH - Basic
SWOT_L2_LR_SSH_Unsmoothed -> Altimetry product SWOT Level-2 KaRIn Low Rate SSH - Unsmoothed
L4_with_SWOT -> Experimental Product: Multimission Gridded (with SWOT, MIOST only) Level-4 Sea Surface Heights and Velocities
SWOT_L3_LR_SSH_Technical -> Altimetry product SWOT Level-3 Low Rate SSH - Technical
SWOT_L2_LR_SSH_WindWave -> Altimetry product SWOT Level-2 KaRIn Low Rate SSH - WindWave
SWOT_L3_LR_WIND_WAVE_Extended -> Wind & Wave product SWOT Level-3 WindWave - Extended
SWOT_L3_LR_SSH_Unsmoothed -> Altimetry product SWOT Level-3 Low Rate SSH - Unsmoothed
SWOT_L2_LR_SSH_Expert -> Altimetry product SWOT Level-2 KaRIn Low Rate SSH - Expert
SWOT_L3_LR_WIND_WAVE_Light -> Wind & Wave product SWOT Level-3 WindWave - Light
SWOT_L3_LR_SSH_Expert -> Altimetry product SWOT Level-3 Low Rate SSH - Expert

product = dl_aviso.details('SWOT_L3_LR_SSH_Unsmoothed')

product.last_version

'v3.0'

Download a product

The first time you download a product using the Altimetry Downloader Aviso, credentials will be asked for Aviso authentication. They will be stored in a ~/.netrc file.

List filter values

List the relevant filter values of the get function with filter_infos:

product = dl_aviso.get_product_from_short_name("SWOT_L3_LR_SSH_Basic")
temporal_coverage, half_orbit_range, versions = dl_aviso.filter_infos(product)

temporal_coverage

{'CALVAL': [2023-03-28T23:44:17.000000, 2023-07-10T09:12:05.000000],
 'SCIENCE': [2023-07-26T12:27:56.000000, 2026-09-15T20:38:36.000000]}

half_orbit_range

{'CALVAL': ((474, 3), (578, 4)), 'SCIENCE': ((1, 149), (56, 142))}

versions

{'2.0.1', '3.0'}

Download

Use get function to download half-orbit files.

dl_aviso.get(
    'SWOT_L2_LR_SSH_Basic', 
    cycle_number=37, 
    pass_number=2,
    version='PID0',
    output_dir=output_dir
)

['/home/atonneau/TMP_DATA/SWOT_L2_LR_SSH_Basic_037_002_20250810T092805_20250810T101933_PID0_01.nc']

To download several cycles and/or half-orbits:

dl_aviso.get(
    'SWOT_L3_LR_SSH_Basic', 
    cycle_number=[40, 41], 
    pass_number=list(range(10, 16)),
    output_dir=output_dir, 
    overwrite=True
)

About to download 12 file(s), estimated total size: 44.6 MB

['/home/atonneau/TMP_DATA/SWOT_L3_LR_SSH_Basic_040_010_20251012T063453_20251012T072620_v3.0.nc',
 '/home/atonneau/TMP_DATA/SWOT_L3_LR_SSH_Basic_040_011_20251012T072620_20251012T081747_v3.0.nc',
 '/home/atonneau/TMP_DATA/SWOT_L3_LR_SSH_Basic_040_012_20251012T081747_20251012T090913_v3.0.nc',
 '/home/atonneau/TMP_DATA/SWOT_L3_LR_SSH_Basic_040_013_20251012T090914_20251012T100040_v3.0.nc',
 '/home/atonneau/TMP_DATA/SWOT_L3_LR_SSH_Basic_040_014_20251012T100041_20251012T105207_v3.0.nc',
 '/home/atonneau/TMP_DATA/SWOT_L3_LR_SSH_Basic_040_015_20251012T105207_20251012T114334_v3.0.nc',
 '/home/atonneau/TMP_DATA/SWOT_L3_LR_SSH_Basic_041_010_20251102T031959_20251102T041126_v3.0.nc',
 '/home/atonneau/TMP_DATA/SWOT_L3_LR_SSH_Basic_041_011_20251102T041126_20251102T050253_v3.0.nc',
 '/home/atonneau/TMP_DATA/SWOT_L3_LR_SSH_Basic_041_012_20251102T050253_20251102T055419_v3.0.nc',
 '/home/atonneau/TMP_DATA/SWOT_L3_LR_SSH_Basic_041_013_20251102T055420_20251102T064546_v3.0.nc',
 '/home/atonneau/TMP_DATA/SWOT_L3_LR_SSH_Basic_041_014_20251102T064547_20251102T073713_v3.0.nc',
 '/home/atonneau/TMP_DATA/SWOT_L3_LR_SSH_Basic_041_015_20251102T073714_20251102T082840_v3.0.nc']

Subset a product

Use subset function to download subsets of a product using filters.

Note

Use show_progress=True on get or subset functions to display a download progress bar

local_files = dl_aviso.subset(
    "SWOT_L3_LR_SSH_Unsmoothed",
    box=(-10, 10, 10, 40),
    selected_variables=["ssha_unfiltered", "time"],
    cycle_number=10,
    pass_number=[223, 238, 251],
    version="3.0",
    output_dir=output_dir,
    overwrite=True
)

INFO:altimetry_downloader_aviso.catalog_client.client:Fetching products from Aviso's catalog...
INFO:altimetry_downloader_aviso.catalog_client.granule_discoverer:Filtering SWOT_L3_LR_SSH_Unsmoothed product with filters {'cycle_number': [10], 'pass_number': [223, 238, 251], 'version': '3.0'}...
INFO:altimetry_downloader_aviso.core:Subsetting 3 file(s)...

local_files

['/home/atonneau/TMP_DATA/SWOT_L3_LR_SSH_Unsmoothed_010_223_20240201T224047_20240201T233213_v3.0.nc',
 '/home/atonneau/TMP_DATA/SWOT_L3_LR_SSH_Unsmoothed_010_238_20240202T113229_20240202T122356_v3.0.nc',
 '/home/atonneau/TMP_DATA/SWOT_L3_LR_SSH_Unsmoothed_010_251_20240202T224118_20240202T233244_v3.0.nc']

Open data using altimetry.io

from altimetry.io import AltimetryData, FileCollectionSource

Open data source

alti_data = AltimetryData(
    source=FileCollectionSource(
        path=output_dir,
        ftype="SWOT_L3_LR_SSH",
        subset="Unsmoothed",
    ),
)

Query data

ds = alti_data.query_orbit(
    cycle_number=10,
    pass_number=[223, 238, 251]
)
ds

INFO:fcollections.core._filesdb:Picked subset {'version': '3.0', 'subset': <ProductSubset.Unsmoothed: 4>}
INFO:fcollections.core._readers:Files to read: 3

<xarray.Dataset>
Dimensions:          (num_lines: 24867, num_pixels: 519)
Coordinates:
    time             (num_lines) datetime64[ns] dask.array<chunksize=(7882,), meta=np.ndarray>
    latitude         (num_lines, num_pixels) float64 dask.array<chunksize=(7882, 519), meta=np.ndarray>
    longitude        (num_lines, num_pixels) float64 dask.array<chunksize=(7882, 519), meta=np.ndarray>
Dimensions without coordinates: num_lines, num_pixels
Data variables:
    ssha_unfiltered  (num_lines, num_pixels) float64 dask.array<chunksize=(7882, 519), meta=np.ndarray>
    cycle_number     (num_lines) uint8 10 10 10 10 10 10 ... 10 10 10 10 10 10
    pass_number      (num_lines) uint8 223 223 223 223 223 ... 251 251 251 251
Attributes: (12/43)
    Conventions:                     CF-1.9
    Metadata_Conventions:            Unidata Dataset Discovery v1.0
    cdm_data_type:                   Swath
    comment:                         Sea Surface Height measured by Altimetry
    geospatial_lat_units:            degrees_north
    geospatial_lon_units:            degrees_east
    ...                              ...
    geospatial_lon_max:              359.999999
    date_modified:                   2026-08-13T20:12:18Z
    history:                         2026-08-13T20:12:18Z: Created by DUACS K...
    date_created:                    2026-08-13T20:12:18Z
    date_issued:                     2026-08-13T20:12:18Z
    temporality:                     reproc

xarray.Dataset

• Dimensions:
  • num_lines: 24867
  • num_pixels: 519
• Coordinates: (3)
  • time
    (num_lines)
    datetime64[ns]
    dask.array<chunksize=(7882,), meta=np.ndarray>

    comment :

    Time of measurement in seconds in the UTC time scale since 1 Jan 2000 00:00:00 UTC. [tai_utc_difference] is the difference between TAI and UTC reference time (seconds) for the first measurement of the data set. If a leap second occurs within the data set, the attribute leap_second is set to the UTC time at which the leap second occurs.

    leap_second :

    0000-00-00T00:00:00Z

    long_name :

    time in UTC

    standard_name :

    time

    tai_utc_difference :

    37.0

    _ChunkSizes :

    82974

    Array Chunk Bytes 194.27 kiB 102.15 kiB Shape (24867,) (13075,) Dask graph 3 chunks in 7 graph layers Data type datetime64[ns] numpy.ndarray

  • latitude
    (num_lines, num_pixels)
    float64
    dask.array<chunksize=(7882, 519), meta=np.ndarray>

    comment :

    Latitude of measurement [-80,80]. Positive latitude is North latitude, negative latitude is South latitude.

    long_name :

    latitude (positive N, negative S)

    standard_name :

    latitude

    units :

    degrees_north

    _ChunkSizes :

    [4000 260]

    Array Chunk Bytes 98.46 MiB 51.77 MiB Shape (24867, 519) (13075, 519) Dask graph 3 chunks in 7 graph layers Data type float64 numpy.ndarray

  • longitude
    (num_lines, num_pixels)
    float64
    dask.array<chunksize=(7882, 519), meta=np.ndarray>

    comment :

    Longitude of measurement. East longitude relative to Greenwich meridian.

    long_name :

    longitude (degrees East)

    standard_name :

    longitude

    units :

    degrees_east

    _ChunkSizes :

    [4000 260]

    Array Chunk Bytes 98.46 MiB 51.77 MiB Shape (24867, 519) (13075, 519) Dask graph 3 chunks in 7 graph layers Data type float64 numpy.ndarray

• Data variables: (3)
  • ssha_unfiltered
    (num_lines, num_pixels)
    float64
    dask.array<chunksize=(7882, 519), meta=np.ndarray>

    long_name :

    sea surface height anomaly calibrated and edited

    standard_name :

    sea_surface_height_above_mean_sea_level

    comment :

    Height of the sea surface anomaly with all corrections applied and with calibration and data selection applied; It is equivalent to the Sea Level Anomaly (SLA) distribued in the nadir DUACS products; see the product user manual for details.

    units :

    m

    _ChunkSizes :

    [4000 260]

    Array Chunk Bytes 98.46 MiB 51.77 MiB Shape (24867, 519) (13075, 519) Dask graph 3 chunks in 7 graph layers Data type float64 numpy.ndarray

  • cycle_number
    (num_lines)
    uint8
    10 10 10 10 10 ... 10 10 10 10 10

    array([10, 10, 10, ..., 10, 10, 10], dtype=uint8)

  • pass_number
    (num_lines)
    uint8
    223 223 223 223 ... 251 251 251 251

    array([223, 223, 223, ..., 251, 251, 251], dtype=uint8)

• Indexes: (0)
• Attributes: (43)

  Conventions :

  CF-1.9

  Metadata_Conventions :

  Unidata Dataset Discovery v1.0

  cdm_data_type :

  Swath

  comment :

  Sea Surface Height measured by Altimetry

  geospatial_lat_units :

  degrees_north

  geospatial_lon_units :

  degrees_east

  geospatial_vertical_max :

  0

  geospatial_vertical_min :

  0

  geospatial_vertical_positive :

  down

  geospatial_vertical_resolution :

  point

  geospatial_vertical_units :

  m

  keywords :

  Oceans > Ocean Topography > Sea Surface Height

  keywords_vocabulary :

  NetCDF COARDS Climate and Forecast Standard Names

  processing_level :

  L3

  product_version :

  3.0

  project :

  SSALTO/DUACS

  source :

  Altimetry measurements

  ssalto_duacs_comment :

  The reference mission used for the altimeter inter-calibration processing is Sentinel-6A

  standard_name_vocabulary :

  NetCDF Climate and Forecast (CF) Metadata Convention Standard Name Table v37

  time_coverage_resolution :

  PT0.027S

  title :

  NRT SWOT KaRIn & nadir Global Ocean swath SSALTO/DUACS Sea Surface Height L3 product

  platform :

  Swot

  institution :

  CLS, CNES

  data_used :

  SWOT KaRIn L2_LR_SSH PGC0/PIC0/PIC2/PID0 (NASA/CNES). DOI associated: https://doi.org/10.24400/527896/a01-2023.016

  reference_altimeter :

  S6

  references :

  Handbook: https://www.aviso.altimetry.fr/fileadmin/documents/data/tools/handbook_duacs_SWOT_L3.pdf

  doi :

  https://doi.org/10.24400/527896/A01-2024.003

  contact :

  aviso@altimetry.fr

  creator_email :

  aviso@altimetry.fr

  creator_name :

  DUACS - Data Unification and Altimeter Combination System

  creator_url :

  https://aviso.altimetry.fr

  license :

  https://www.aviso.altimetry.fr/fileadmin/documents/data/License_Aviso.pdf

  time_coverage_start :

  2024-02-01T22:40:47Z

  time_coverage_end :

  2024-02-01T23:32:13Z

  geospatial_lat_min :

  -78.258972

  geospatial_lat_max :

  78.255512

  geospatial_lon_min :

  1e-06

  geospatial_lon_max :

  359.999999

  date_modified :

  2026-08-13T20:12:18Z

  history :

  2026-08-13T20:12:18Z: Created by DUACS KaRIn prototype

  date_created :

  2026-08-13T20:12:18Z

  date_issued :

  2026-08-13T20:12:18Z

  temporality :

  reproc

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