OCSTrack: Ocean-Model-Data Collocation Tools

OCSTrack is an object-oriented Python package for the along-track collocation of satellite (2D) and Argo Float (3D) data with ocean circulation and wave model outputs. It simplifies the process of aligning diverse datasets, making it easier to compare and validate model simulations against observational data.

Key Features

• Automated Data Fetching: Downloads satellite altimetry data from two sources — CoastWatch (NOAA STAR) and ESA CCI Sea State (IFREMER) — and Argo float data from IFREMER.
• Model Support: Natively handles outputs from SCHISM (and WWM), ADCIRC, SWAN, and WW3 models.
• Flexible Collocation: Performs temporal and spatial collocation for both 2D surface tracks and 3D profiles.
• Efficient & Scalable: Uses xarray and dask for efficient, out-of-core computations on large datasets.
• Customizable: Object-oriented design makes it easy to extend support for new models or observational data types.

Installation

You can install OCSTrack directly from PyPI:

pip install ocstrack

To install the latest development version directly from this repository:

pip install git+https://github.com/noaa-ocs-modeling/OCSTrack.git

Optional dependencies

OCSTrack has two sets of optional extras:

# Accurate depth conversion for Argo data
pip install "ocstrack[gsw]"

# Shapefile/polygon cropping support
pip install "ocstrack[geo]"

# Everything
pip install "ocstrack[all]"

Satellite Data Sources

OCSTrack supports two satellite altimetry data sources. Both are handled by the same SatelliteData class, which auto-detects the format.

CoastWatch (NOAA STAR)

Daily merged NetCDF files from the NOAA STAR CoastWatch program. No credentials required.

from ocstrack.Observation.get_sat_coastwatch import get_multi_sat_coastwatch

get_multi_sat_coastwatch(
    start_date="2023-01-16", end_date="2023-01-31",
    sat_list=['sentinel3a', 'sentinel3b', 'jason3'],
    output_dir="./sat_data/",
    lat_min=18, lat_max=31, lon_min=-98, lon_max=-80,
)

Limitations: Old data may be deleted without notice; SWH is capped at 8 m.

ESA CCI Sea State v5 (IFREMER)

Along-track per-pass files from the ESA Climate Change Initiative Sea State project, hosted on the IFREMER FTP server. Suitable for extreme wave analysis (no SWH cap).

Credentials required. Register at https://eftp.ifremer.fr to obtain a free username and password. Store them as environment variables:

export CCI_FTP_USER="your_username"
export CCI_FTP_PASS="your_password"

import os
from ocstrack.Observation.get_sat_cci import get_multi_sat_cci

get_multi_sat_cci(
    start_date="2023-01-16", end_date="2023-01-31",
    sat_list=['jason-3', 'sentinel-3a', 'sentinel-3b'],
    output_dir="./cci_sat_data/",
    ftp_user=os.environ["CCI_FTP_USER"],
    ftp_pass=os.environ["CCI_FTP_PASS"],
    lat_min=18, lat_max=31, lon_min=-98, lon_max=-80,
)

Advantages over CoastWatch: Stable long-term archive; no SWH cap; includes swh_with_8m_offset_correction, swh_quality_level, swh_uncertainty, bathymetry, and distance_to_coast.

Quick Start

Here is a minimal example of how to collocate satellite altimetry data with a WW3 model run.

import numpy as np
from ocstrack.Model.model import WW3
from ocstrack.Observation.satellite import SatelliteData
from ocstrack.Collocation.collocate import Collocate

# Load satellite data — SatelliteData auto-detects CoastWatch or CCI format
sat_data = SatelliteData("/path/to/merged_satellite_data.nc")
print(sat_data.data_source)  # 'coastwatch' or 'cci'

# Load WW3 model
model_run = WW3(
    rundir="/path/to/ww3/run/",
    model_dict={"var": "hs"},
    start_date=np.datetime64("2023-01-16"),
    end_date=np.datetime64("2023-01-31"),
)

# Collocate
coll = Collocate(model_run=model_run, observation=sat_data, n_nearest=3)
ds_coll = coll.run(output_path="collocated.nc")
print("Collocation complete!")

Documentation

For more detailed examples and the full API reference, please see our documentation website:

https://noaa-ocs-modeling.github.io/OCSTrack/

Contributing

We welcome contributions! If you have ideas for new features, find a bug, or would like to improve the documentation, please open an issue or submit a pull request.

License

This project is licensed under the terms of the CC0 1.0 Universal license. See the LICENSE.txt file for details.

How to Cite

If you use OCSTrack for 3D collocation with Argo floats, please cite:

Cassalho, F., S. Mani, S. Moghimi, F. Ye, and Y. J. Zhang. "OCSMesh and an automated creek-to-ocean mesh generation workflow." Ocean Modelling 203 (2026): 102774. https://doi.org/10.1016/j.ocemod.2026.102774.

If you use OCSTrack for 2D collocation with satellite altimetry, please cite:

Cassalho, F., A. L. Kurapov, S. Moghimi, S. M. Durski, J. Y. Zhang, A. Abdolali, et al. "Tidal modulation of waves around the Aleutian Islands." Journal of Geophysical Research: Oceans 131 (2026): e2025JC023780. https://doi.org/10.1029/2025JC023780.

Disclaimer

This repository is a scientific product and is not official communication of the National Oceanic and Atmospheric Administration, or the United States Department of Commerce. All NOAA GitHub project code is provided on an "as is" basis and the user assumes responsibility for its use. Any claims against the Department of Commerce or Department of Commerce bureaus stemming from the use of this GitHub project will be governed by all applicable Federal law. Any reference to specific commercial products, processes, or services by service mark, trademark, manufacturer, or otherwise, does not constitute or imply their endorsement, recommendation or favoring by the Department of Commerce. The Department of Commerce seal and logo, or the seal and logo of a DOC bureau, shall not be used in any manner to imply endorsement of any commercial product or activity by DOC or the United States Government.