On Wednesday, July 28 from 8:00 a.m. to 4:00 p.m. (USA Mountain Time), the following data collections may not be available due to planned system maintenance: AMSR-E, Aquarius, High Mountain Asia, IceBridge, ICESat/GLAS, ICESat-2, MEaSUREs, MODIS, NISE, SMAP, SnowEx, and VIIRS.
Data Set ID: 
ATL09

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

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.

There is a more recent version of these data.

Version Summary: 

Changes for this version include:

  • Replaced the binary cloud_flag_asr parameter with cloud_conf_flag_asr (0-5) in the routine that computes layer_flag. This new parameter combines apparent surface reflectance (ASR) cloud detection and Density Dimension Algorithm (DDA) cloud detection into a single, consolidated confidence flag.
  • Corrected several issues related to units in the ATL09 documentation and product template.
  • Added a layer_conf_dens parameter which indicates the confidence associated with the corresponding layer detection.
  • Added constants phi_land and phi_ocean as adjustable (input) parameters in the algorithm that determines whether a cloud is present based on the measured ASR.
  • Modified the start bin in the blowing snow optical depth algorithm to mitigate a problem in v01 which led to unrealistically high values of optical depth.
  • Fixed a bug in the surf_ht_dens_mod algorithm.
  • Changed the nighttime QUANTILE1 to 0.97.
  • Corrected an issue where an invalid density value could contaminate the computed value.
  • Updated a hard-coded cloud thickness and separation value in v01 to allow the control file overrides to work correctly.
  • Changed the default value for layer_conf to be invalid.
  • Modified the surface height removal implemented in v01 to handle clouds at surfaces more than 300 m thick.
  • Added blowing snow = invalid to the multiple scattering warning flag (msw_flag) criteria for msw_flag = 0. This change addresses logic in the MSW flag that did not treat blowing snow as a layer.
  • Added a 700-bin relative humidity profile to the product (input from ATL04) to better discriminate between clouds and aerosols.
  • Modified the confidence limits for bs_conf in the blowing snow algorithm.
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 to 15 November 2019
Version(s):V2
Temporal Resolution91 dayMetadata XML:View Metadata Record
Data Contributor(s):Steve Palm, Yeukui Yang, Ute Herzfeld, David Hancock, Kristine Barbieri, et al

Geographic Coverage

No access options.

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. 2019. ATLAS/ICESat-2 L3A Calibrated Backscatter Profiles and Atmospheric Layer Characteristics, Version 2. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: https://doi.org/10.5067/ATLAS/ATL09.002. [Date Accessed].

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