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Data Set ID:
ATL09

ATLAS/ICESat-2 L3A Calibrated Backscatter Profiles and Atmospheric Layer Characteristics, Version 3

This data set (ATL09) contains calibrated, attenuated backscatter profiles, layer integrated attenuated backscatter, and other parameters including cloud layer height and atmospheric characteristics obtained from the data. 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:

  • A new parameter was added to the equation used to compute blowing snow. The algorithm detects blowing snow at two rates -- high (25 Hz) and low (1 Hz) -- however, the optimal threshold for low rate detection was found to be different (lower) than for high rate detection. The new parameter (ancillary_data/atmosphere/lr_bsnow_fac) adjusts the low rate detection threshold and improves retrievals. The new parameter's nominal value of 0.5 is adjustable.
  • Low-rate blowing snow height (profile_[x]/low_rate/bsnow_h) is now computed as defined in the ATBD for ATL04 (section 4.5.1 | Blowing Snow layer Height).
  • The value for the high rate blowing snow threshold constant (ancillary_data/atmosphere/bs_thresh_scale) was changed from 10.0 to 20.0 to reduce blowing snow detections.
  • A new parameter for blowing snow intensity (profile_[x]/high_rate/bsnow_intensity) was added to the product; it is defined as the average scattering ratio within the blowing snow layer multiplied by the 10 m level wind speed.
  • ATL09 was updated to accommodate the new pass-through constant (alpha) added to ATL04.
  • The single scaling constant phi, used to define a threshold in the apparent surface reflectance (ASR) cloud detection algorithm, was replaced by two constants, phi_land and phi_ocean. These new scaling parameters allow for different thresholds over land and ocean to address analyses that indicate the algorithm was reporting too many clouds over land and too few over ocean.
  • Areas masked out in ATL04 due to dense clouds were not being properly masked out in ATL09. This bug was corrected.
  • The ancillary_data/atmosphere/cloud_det_layer_thick parameter was no longer needed and removed.

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

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Parameter(s):
  • CLOUDS > CLOUD PROPERTIES
  • LIDAR > LIDAR BACKSCATTER
Data Format(s):
  • HDF5
Spatial Coverage:
N: 90, 
S: -90, 
E: 180, 
W: -180
Platform(s):ICESat-2
Spatial Resolution:
  • 280 m
Sensor(s):ATLAS
Temporal Coverage:
  • 13 October 2018
Version(s):V3
Temporal Resolution91 dayMetadata XML:View Metadata Record
Data Contributor(s):Steve Palm, Yeukui Yang, Ute Herzfeld, David Hancock, Kristine Barbieri, et al

Geographic Coverage

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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.

Palm, S. P., Y. Yang, U. C. Herzfeld, D. Hancock, K. A. Barbieri, J. Wimert, and the ICESat-2 Science Team. 2020. ATLAS/ICESat-2 L3A Calibrated Backscatter Profiles and Atmospheric Layer Characteristics, Version 3. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: https://doi.org/10.5067/ATLAS/ATL09.003. [Date Accessed].

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