2026-08-28T16:21:16Zhttp://nsidc.org/api/dataset/metadata/oai

oai:nsidc.org/ATL09.0022026-04-01T17:51:25Zcumulusretirednasa_nsidc_daac

ATL09.002ATLAS/ICESat-2 L3A Calibrated Backscatter Profiles and Atmospheric Layer CharacteristicsPalm, S. P., Yang, Y., Herzfeld, U. C., Hancock, D., Barbieri, K. A., Wimert, J. & the ICESat-2 Science TeamATLAS/ICESat-2 L3A Calibrated Backscatter Profiles and Atmospheric Layer Characteristics2019-10-24Boulder, Colorado USANASA NSIDC DAAC: NASA National Snow and Ice Data Center Distributed Active Archive Center2false10.5067/ATLAS/ATL09.002https://nsidc.org/sites/default/files/atl09-v002-userguide_1.pdfATL09Technical ContactNSIDCUser Servicesnsidc@nsidc.org1-303-492-61991-303-492-2468

CIRES, 449 UCB

University of Colorado

BoulderCO80309-0449USAEARTH SCIENCEATMOSPHERECLOUDSCLOUD PROPERTIES EARTH SCIENCESPECTRAL/ENGINEERINGLIDARLIDAR BACKSCATTER Climatology/Meteorology/Atmosphereicesat2-projectATLASAdvanced Topographic Laser Altimeter SystemICESat-2Ice, Cloud, and land Elevation Satellite-22018-10-132019-11-15deprecated-9090-180180GEOGRAPHIC REGIONGLOBAL280 m30 m91 dayThese data have been retired and are no longer accessible, though a more recent version of these data may be available.These data have been retired and are no longer available for use, though a more recent version of these data may be available. Cite any prior or planned use of these data according to the recommended citation at https://nsidc.org/about/data-use-and-copyright. For more information on the NASA ESDIS Data Use Guidance, see https://www.earthdata.nasa.gov/engage/open-data-services-software-policies/data-use-guidance.EnglishNASA/GSFC/SED/ESD/I2-SIPSNASA NSIDC DAACNASA National Snow and Ice Data Center Distributed Active Archive Centerhttps://nsidc.org/daacData Center ContactNSIDCUser Servicesnsidc@nsidc.org1-303-492-6199

National Snow and Ice Data Center

CIRES, 449 UCB

University of Colorado

BoulderCO80309-0449USAHTTPSHDF5

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.

VIEW RELATED INFORMATIONhttps://nsidc.org/sites/default/files/atl09-v002-userguide_1.pdfATLAS/ICESat-2 L3A Calibrated Backscatter Profiles and Atmospheric Layer Characteristics, Version 2 User GuideCEOS IDN DIFVERSION 9.92019-10-242026-04-01NSIDCVersion SummaryReplaced 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.NSIDCMinor VersionNSIDCSpatial Reference SystemsEPSG:4326WGS 84NSIDCLevel of ServiceNo Data AccessNSIDCFull Dataset CitationPalm, S. P., Yang, Y., Herzfeld, U. C., Hancock, D., Barbieri, K. A., Wimert, J. & the ICESat-2 Science Team. (2019). <i>ATLAS/ICESat-2 L3A Calibrated Backscatter Profiles and Atmospheric Layer Characteristics</i>. (ATL09, Version 2). [Data Set]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. <a href="https://doi.org/10.5067/ATLAS/ATL09.002">https://doi.org/10.5067/ATLAS/ATL09.002</a>. [<i><describe subset used if applicable></i>].NSIDCRetiredtrue