NASA's Atmospheric Science Data Center (ASDC) has released the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) Clear-Sky Constrained Aerosol Extinction Profiles (CALIOP AEP) collections. These data products provide global clear-sky aerosol extinction profiles derived from CALIOP data, offering valuable insights into aerosol behavior over land and ocean regions. The CALIOP AEP collections aim to improve global aerosol extinction profiles.
CALIOP aerosol extinction retrievals rely on lidar ratios, which are the ratio of aerosol extinction to aerosol backscatter. Operational CALIOP retrievals of aerosol extinction profiles typically rely on estimates of lidar ratios based on inferences of aerosol type. Errors in these inferences as well as the uncertainties associated with the lidar ratios assumed for these aerosol types can introduce significant systematic uncertainties (~30–50%) in aerosol extinction estimates.
The primary objective of this project is to mitigate these uncertainties by deriving column average lidar ratios using aerosol optical depth (AOD) derived from CALIOP Ocean-Derived Column Optical Depth (ODCOD) product, measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS), and model runs provided by the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2).
Based on comparisons with coincident aerosol extinction profiles measured by the NASA Langley Research Center (LaRC) airborne High Spectral Resolution Lidars, the clear-sky aerosol extinction profiles derived using these AOD constraints are, on average, more accurate than the clear-sky aerosol extinction profiles from the operational retrievals. Consequently, these aerosol extinction profiles can help reduce uncertainties in estimating surface PM2.5 concentrations and benefit aerosol radiative forcing.
Data Products
- CAL_ODCOD_ext_05km_V4-5 (Version 1): CALIOP Clear-Sky Constrained Aerosol Extinction Profiles constrained by Ocean-Derived Column Optical Depth (ODCOD)—This dataset provides clear-sky aerosol extinction profiles over oceanic regions during daytime and nighttime.
- CAL_MODIS_DTDB_ext_05km_V4-5 (Version 1): CALIOP Clear-Sky Constrained Aerosol Extinction Profiles constrained by MODIS DarkTarget/Deep Blue (DTDB) AOD—This dataset provides clear-sky aerosol extinction profiles during the day.
- CAL_MERRA2_ext_05km_V4-5 (Version 1): CALIOP Clear-Sky Constrained Aerosol Extinction Profiles leveraging column AOD obtained from MERRA-2 (which assimilates MODIS, MISR, and AERONET)—This dataset spans daytime and nighttime observations over both land and ocean.
Technical Details
Spatial coverage: 82°N to 82°S, 180°W to 180°E; Vertical coverage from 22 m to 40,000 m.
Temporal coverage:
- CAL_ODCOD_ext_05km_V4-5 = June 12, 2006, to June 30, 2023
- CAL_MODIS_DTDB_ext_05km_V4-5 = June 12, 2006, to August 31, 2018
- CAL_MERRA2_ext_05km_V4-5 = June 12, 2006, to June 30, 2023
File format: netCDF-4 classic
Processing level: Level 2
Version:
Access Methods
Users can access this data through NASA’s Earthdata Search and through these CMR Virtual Directories:
User Support
For questions about this data release or assistance with data access, please contact the ASDC User Services team or visit the Earthdata Forum.