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GlobWave Satellite Data

GlobWave will allow easy access to a harmonised set of Altimeter and SAR products.

Here we outline what the GlobWave data is and how it can be accessed.

For full details of all GlobWave data products and their content, please access the GlobWave Product User Guide.

What is the GlobWave satellite data?

The GlobWave satellite products give a “uniform” set of along track satellite wave data from all available Altimeters (spanning multiple space agencies) and from ESA Synthetic Aperture Radar (SAR) data.

The main parameters to be measured are:-

  • Altimeter: Significant Wave Height and Backscatter Coefficient (Sigma0)
  • SAR: Swell Significant Wave Height, dominant wavelength (per spectral partition) and mean direction (per spectral partition)

How is it different from the original native products provided by the Space Agencies?

One question that often gets asked is “how is a GlobWave satellite data stream different to the native data stream” e.g. the Envisat Altimeter delayed mode product vs the GlobWave delayed mode product?

The answer is that the corresponding GlobWave product file will contain the wave related parameters from the native product plus a series of important additional information. These include a consistent quality flag and error characterisation definition across all GlobWave data streams as well as ancillary data from ECMWF numerical models such as distance to coast, bathymetry and sea surface temperature. A full description of the additional information is provided by the blue text in section 4.3 of the Product User Guide.

Also, all GlobWave data streams come in the same format, which is netCDF-3 with CF (v1.4) conventions. This ensures that minimal time is spent writing ingestion routines and maximum time is spent doing interest science and applications with the data.

Exactly what data streams are supported?

We allow free access to both SAR and Altimeter data sets in both real time and delayed mode. The delayed mode data consists of 12 data streams from 9 satellites and stretches back as far as 1985 with GEOSAT. Further details are outlined in the following table:

Source

Type

Dates

ESA ERS-1

Altimeter

01/02/1992 – 02/06/1996

ESA ERS-2

Altimeter

15/05/1995 – 22/06/2003[1]

ESA ERS-1

SAR

01/01/1991– 01/12/1996

ESA ERS-2

SAR

01/01/1996 - 04/7/2011

ESA Envisat

Altimeter

26/08/2002 - 08/04/2012

ESA Envisat

SAR

17/12/2002 - 08/04/2012

CNES/NASA Topex/POSEIDON

Altimeter

25/09/1992- 08/10/2005

CNES/NASA Jason-1

Altimeter

15/01/2002 onwards

CNES/NASA Jason-2

Altimeter

01/12/2008 onwards

US Navy GEOSAT

Altimeter

31/03/1985-30/12/1989

US Navy/NOAA GEOSAT Follow On

Altimeter

08/01/2000 - 23/07/2008

ESA / NOAA CryoSAT-2

Altimeter

28/01/2011 onwards

The near-real-time data consists of 4 data streams from 3 satellites and is available from GlobWave within about 3 hours of the actual observation from space. Further details are outlined in the following table:

Source

Type

Dates

ESA Envisat

Altimeter

26/08/2002 - 08/04/2012

ESA Envisat

SAR

17/12/2002 - 08/04/2012

CNES/NASA Jason-1

Altimeter

15/01/2002 onwards

CNES/NASA Jason-2

Altimeter

01/12/2008 onwards

How I do I get access to the data?

The data is hosted on an ftp site. Username and password details can be obtained by e-mailing the CERSAT Help Desk at This email address is being protected from spambots. You need JavaScript enabled to view it. with the subject: GlobWave Data Access. We recommend that you consult sections 3 and 4.4.6 of the Product User Guide regarding essential information and known issues respectively.

If you already have a username and password then you can browse the data on the ftp site by clicking here.

GlobWave offers free access to 1 geophysical quality and 1 real-time SAR wave mode data streams from 1 satellite stretching back as far as 2002 with Envisat in an homogenenous and consistent format and content. ERS-1 and ERS-2 data will be also available in a close future too.

GlobWave offers free access to 9 geophysical quality and 3 real-time altimeter data streams from 9 satellites stretching back as far as 1985 with GEOSAT in an homogenenous and consistent format and content.

Matching measurements between satellite and in situ buoys, or matchups, are computed for various pairs of buoy networks and satellites providing a comprehensive dataset to assess, monitor and intercompare the accuracy of each of these sources of measurements. This database is periodically updated and aims at including as many sources of - directional and non-directional - wave measurements as possible.

Altimeter crossovers are computed for each pair of satellites, when crossing of their respective tracks is possible, providing a comprehensive dataset of coincident measurements that can be used to monitor the quality of each sensor and improve their calibration.