For a list of known issues with this product, see the Known Issues document under the Technical References tab.
VERSION 3: Selected granules for ATL03 and associated products (ATL04, ATL06, ATL07, ATL08, ATL09, ATL10, ATL12, ATL13) have been recalled and will be released at a later time. For a list of recalled data, see the 'Retracted Data File List' document under Technical References.
Data Set ID:
ATL12

ATLAS/ICESat-2 L3A Ocean Surface Height, Version 4

This data set (ATL12) contains along-track sea surface heights at variable length scales over cloud-free regions. Estimates of height distributions, surface roughness, surface slope, and apparent reflectance are also provided. The data were acquired by the Advanced Topographic Laser Altimeter System (ATLAS) instrument on board the Ice, Cloud and land Elevation Satellite-2 (ICESat-2) observatory.

This is the most recent version of these data.

Version Summary:

Changes for this version include:

  • Implemented the usage of the ATL03 orbit and pointing flag (podppd_flag) to only process data with podppd_flag=0. This is done to avoid putting out bad sea surface heights when the underlying pointing and position data are bad.
  • Updated the moving average process to consider photons with signal confidence 3 and 4 to be consistent with the ATBD.
  • Aligned the atmosphere data (layer_flag) collected only for the strong beams by segment_id for the processing of weak beam data.
  • Changed from surface finding based on the distribution of photon heights to surface finding based on the photon height anomaly relative to a moving bin average of high confidence photon heights. This is done to exclude subsurface returns under the crests of surface waves that otherwise fall inside the histogram of true surface heights. Added control variables (Table 5 of ATBD) conf_lim, the limiting confidence level to be included in the moving bin average, nphoton, the number of photons either side of a central photon to be included in the moving bin average, e.g., for nphoton=10, a 21 point average is used.
  • Computed nharms harmonic coefficients, a, and SNR, snr, of along-track heights. These are added features to characterize the surface wave environment in each ocean segment as harmonic coefficients versus wave numbers, wn, in the along-track direction (wave direction is not accounted for at this time).
  • Computed correlation length scale from 10-m bin averaged heights, l_scale, the corresponding degrees of freedom, np_effect, and resultant uncertainty, h_uncrtn, in the estimated sea surface heights. This is to provide an uncertainty estimate for average height over an ocean segment that accounts for the lack of statistical independence between photon heights over surface waves.
  • Updated to process only data with quality_ph equal to zero to avoid outputting surface heights based on poor quality photon heights as determined in ATL03.

COMPREHENSIVE Level of Service

Data: Data integrity and usability verified; data customization services available for select data

Documentation: Key metadata and comprehensive user guide available

User Support: Assistance with data access and usage; guidance on use of data in tools and data customization services

See All Level of Service Details

Parameter(s):
  • SEA SURFACE TOPOGRAPHY > SEA SURFACE HEIGHT
Data Format(s):
  • HDF5
Spatial Coverage:
N: 90, 
S: -90, 
E: 180, 
W: -180
Platform(s):ICESat-2
Spatial Resolution:
  • Varies
Sensor(s):ATLAS
Temporal Coverage:
  • 13 October 2018
Version(s):V4
Temporal Resolution91 dayMetadata XML:View Metadata Record
Data Contributor(s):James Morison, David Hancock, Suzanne Dickinson, John Robbins, Leeann Roberts, et al

Geographic Coverage

Other Access Options

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As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Morison, J. H., D. Hancock, S. Dickinson, J. Robbins, L. Roberts, R. Kwok, S. P. Palm, B. Smith, M. F. Jasinski, and the ICESat-2 Science Team. 2021. ATLAS/ICESat-2 L3A Ocean Surface Height, Version 4. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: https://doi.org/10.5067/ATLAS/ATL12.004. [Date Accessed].

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