CAL_MERRA2_ext_05km_V4-5_1 provides a comprehensive global dataset of clear-sky aerosol extinction profiles derived from CALIOP data. These retrievals leverage column aerosol optical depth (AOD) obtained from the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), which assimilates AOD observations from MODIS, MISR, and AERONET. The dataset spans daytime and nighttime observations over both land and ocean from 2006 to 2023.   

Traditional CALIOP aerosol extinction retrievals rely on lidar ratios, introducing significant uncertainties (~30–50%). By substituting lidar ratios with column AOD, we computed constrained aerosol extinction profiles using CALIOP attenuated backscatter data. These profiles were validated against more than 150 coincident airborne High Spectral Resolution Lidar (HSRL) datasets, showing strong agreement with mean bias differences within 0.01 km⁻¹ (10%). Compared to operational CALIOP V4.51 aerosol extinction retrievals, these constrained profiles achieved nearly twofold reductions in bias and root-mean-square errors. 

The resulting global dataset holds immense value for critical applications such as estimating PM2.5 concentrations and reducing uncertainties in observational assessments of aerosol direct radiative forcing.