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ALES Sea Surface Heights (SSH_ALES)

Sea Level Anomalies (SLA) from Jason-2 using Adaptive Leading Edge Subwaveform (ALES) Retracker
Sea Level Anomalies (SLA) from Jason-2 using Adaptive Leading Edge Subwaveform (ALES) Retracker

The Adaptive Leading Edge Subwaveform (ALES) Retracker is a fitting algorithm used to improve the sea level estimations from satellite altimetry. While the biggest improvement involves the coastal ocean, the sea level data are reliable in the open ocean as well and improve the current standards in terms of noise content.

We currently provide sea surface height data at 1-Hz posting rate (one measurement every ~7km along a track) for single missions in their nominal phase. To derive the Sea Surface Height, we have removed the tides using the EOT tidal model, also described and available in this website.

We also provide the users with the tidal predictions, so that another tidal model can be applied, and with the Mean Sea Surface data from DTU15 model (Andersen and Knudsen, 2009), to allow the derivation of sea level anomalies.

The data of all missions have been cross-calibrated in advance (following the approach of Bosch et al., 2014; referenced to Jason-1), and are corrected for radial errors. Therefore, it should be possible to merge and combine SSH of any mission in order to improve the spatial and temporal resolution.

For more information on the way the sea surface height is derived and on which corrections are applied, the user can read the Chapter 4 of the COSTA user manual (http://epic.awi.de/43972/1/User_Manual_COSTA_v1_0.pdf).

A training course on the dataset is available from: https://mediatum.ub.tum.de/doc/1456132/1456132.pdf

In the present version, we suggest the users to exclude the following data:

  • Distance to Coast < 3 km
  • |SSH-MSS| > 2.5 m
  • SWH > 11 m
  • stdalt > 0.20 m

Available Dataset(s)

Available version(s) of the product "ALES Sea Surface Height product (SSH_ALES)" in OpenADB.

ALES Sea Surface Heights (SSH_ALES)

Version 55 (DTU15, EOT11a, radial errors applied)
  • Mission Dataset Freq. Cycles Dates
    Envisat (Version 3) SGDR v3.0 1 Hz 007 - 093 2002-06-17 21:39:47 -
    2010-10-18 21:28:54
    Jason-1 SGDR-E 1 Hz 001 - 259 2002-01-15 06:29:21 -
    2009-01-26 02:31:33
    Jason-1 (Extended Mission) SGDR-E 1 Hz 262 - 374 2009-02-10 18:01:37 -
    2012-03-03 12:59:11
    Jason-1 (Geodetic Mission) SGDR-E 1 Hz 500 - 537 2012-05-07 16:04:18 -
    2013-06-21 00:51:53
    Jason-2 SGDR-D 1 Hz 001 - 303 2008-07-12 01:25:09 -
    2016-10-02 11:53:12
    Jason-2 (Extended Mission) SGDR-D 1 Hz 305 - 327 2016-10-13 20:00:25 -
    2017-05-17 22:01:04
    Jason-3 SGDR-T 1 Hz 001 - 117 2016-02-17 10:28:45 -
    2019-04-22 13:36:19
    SARAL SGDR-T 1 Hz 001 - 035 2013-03-14 05:44:46 -
    2016-07-04 11:05:52
    SARAL (Drifting Phase) SGDR-T 1 Hz 100 - 128 2016-07-04 12:57:15 -
    2019-04-15 16:53:44
    Sentinel-3A (SAR) SGDR/NTC 1 Hz 025 - 056 2017-11-23 21:37:31 -
    2020-04-05 21:27:24
    Sentinel-3B (SAR) SGDR/NTC 1 Hz 019 - 037 2018-11-23 10:33:41 -
    2020-04-15 21:28:57

The ALES data are distributed here in the hope that they will be useful, but DGFI-TUM provides these data "as is" without warranty, expressed or implied, as to the use or appropriateness of the ALES data, and there are no warranties of merchantability or fitness of these data for a particular purpose or use.

Data Format

The product "Adaptive Leading Edge Subwaveform (ALES) Retracker" includes the following parameters.

Parameter Description
glon Longitude of Satellite Footprint
glat Latitude of Satellite Footprint
jday Julian Day 2000
ssh Sea Surface Heights
stdalt Standard Deviation
swh Significant Wave Height
mssh Mean Sea Surface
otide Ocean Tide Correction
ltide Ocean Load Tide Correction
distance Distance to Coast
sflags Geophysical Corrections Quality Flags
oflags Orbit Status and Quality Flags
iflags Instrument Status and Quality Flags

The data will be provided in NetCDF. More details on the data are available here.

How to cite this dataset

Please cite: "The ALES SSH data were produced by DGFI-TUM and distributed via OpenADB (http://www.openadb.dgfi.tum.de). More details on the retracker and the product are available in Passaro et al. (2014), Passaro et al. (2015) and Passaro et al, (2017)."

Please also give credit to the respective institution(s) in charge of mission operation and maintenance (see bottom of this page).

References

Acknowledgment

Marcello Passaro acknowledges the value of the work performed with Paolo Cipollini (National Oceanography Centre, Southampton), co-author of the ALES algorithm in its first version.

All products are computed based on altimetry missions operated by NASA/CNES (TOPEX, Jason-1), ESA (ERS-1/2, Envisat, Cryosat-2), USNavy/NOAA (GFO), CNES/NASA/Eumetsat/NOAA (Jason-2, Jason-3), ISRO/CNES (Saral), and EUMETSAT (Sentinel-3). The original data sets are disseminated by AVISO, ESA, NOAA, and PODAAC.