Objective

1. A Sensitivity Study of Radiative Fluxes at the Top of Atmosphere to Cloud-Microphysics and Aerosol Parameters in CAM5 • Objective • Investigate the sensitivity of net radiative fluxes at the top of atmosphere to 16 parameters of cloud microphysics and aerosol schemes in CAM5 • Approach • Developed and applied a sensitivity analysis framework to analyze the variance of simulated radiative flux (FNET) due to perturbations of model internal parameters related to cloud microphysics and aerosol processes and external parameters related to aerosol and its precursor gas emissions in CAM5 • Adopted a quasi-Monte Carlo sampling approach to effectively explore the high dimensional parameter space • Perform statistical analyses of the output responses to these parameters, including linear/nonlinear and interaction effects with the generalized linear model Anomalies of variation of global mean FNET, clear-sky FNET (FNETC), and net (SW+LW) cloud forcing at top of atmosphere (TOA) (CF) in response to the perturbations of 16 parameters from the 256 CAM5 simulations. • Impact • The changes in the global mean FNET are dominated by changes in net cloud forcing within the investigated parameter ranges • External emission factors largely affect FNET variance at the regional scale, but their impact is weaker than that of model internal parameters in terms of simulating global mean FNET • Interactions among the 16 parameters contribute a relatively small portion to total FNET variance over most global regions • Better understanding of the parameter uncertainties in CAM5, providing information for future calibration of uncertain model parameters with the largest sensitivity Zhao C, X Liu, Y Qian, J Yoon, Z Hou, G Lin, S McFarlane, H Wang, B Yang, P-L Ma, H.Yan, and J Bao. 2013. “A Sensitivity Study of Radiative Fluxes at the Top of Atmosphere to Cloud-microphysics and Aerosol Parameters in the Community Atmosphere Model CAM5.” Atmospheric Chemistry and Physics13:10969–1098. DOI:10.5194/acp-13-10969-2013