Evaluation of CloudSat Radiative Kernels Using ARM and CERES Observations and ERA5 Reanalysis.

Despite the widespread use of the radiative kernel technique for studying radiative feedbacks and radiative forcings, there has not been any systematic, observation‐based validation of the radiative kernel method. Here, we utilize observed and reanalyzed radiative fluxes and atmospheric profiles from the Atmospheric Radiation Measurement (ARM) program and ERA5 reanalysis to assess a set of observation‐based radiative kernels from CloudSat for six ARM sites. The CloudSat radiative kernels, convoluted with the ERA5 state variables, can almost perfectly reconstruct the monthly anomalies of shortwave (SW) and longwave (LW) radiative fluxes in ERA5 at the surface (SFC) and top‐of‐atmosphere (TOA) with correlations significantly being greater than 0.95. The biases of kernel‐estimated flux anomalies calculated using the ARM‐observed state variables can be more than twice as large when compared with the ARM‐observed surface flux anomalies and Clouds and Earth's Radiant Energy System observed anomalies at the TOA. Generally, clouds contribute to most (>60%) of the variance of flux anomalies at Southern Great Plain (SGP), Tropical Western Pacific (TWP), and Eastern North Atlantic (ENA), and surface albedo dominates (>69%) the variance of SW flux anomalies at North Slope of Alaska. The radiative kernels exhibit the lowest correlation (r∼[0.55,0.85]) when reconstructing SFC LW flux anomalies at SGP, TWP, and ENA, whose biases are related to the possibility that the kernels may not fully capture the characteristics associated with Madden‐Julian oscillation and El Niño‐Southern Oscillation at TWP and the presence of clouds at SGP and ENA. Key Points: Observation‐based CloudSat radiative kernels are evaluated with field observations for six Atmospheric Radiation Measurement sites with different climate characteristicsThe kernels are found to be valuable for reconstructing observed radiative flux anomalies at the surface and top‐of‐atmosphereThe CloudSat kernels are the least skilled in reconstructing the observed changes in longwave radiative flux at the surface [ABSTRACT FROM AUTHOR]