| he environmental effects of cloud radiative fluxes and cloud feedback are a primary uncertainty in our understanding of climate and climate change. Cloud radiative fluxes are a function of cloud scattering properties, which in turn depend on the microphysical properties. This thesis quantifies how accurately we must know scattering and microphysical properties of cirrus clouds so that their radiative effect on climate can be determined. First, our ability to compute cirrus cloud scattering properties from microphysical properties is analyzed. Then the sensitivities of radiative fluxes to perturbations in cirrus scattering and microphysical properties are computed. Our ability to determine scattering and microphysical properties are critiqued, with the greatest attention given to those properties that effect the fluxes most.;Current scattering algorithms are inadequate for determining scattering properties needed to compute cirrus cloud fluxes. The range of crystal sizes is too great and crystal shapes are too irregular to be treated by current methods. Given our inability to compute cirrus scattering properties, the properties would be better-obtained by retrievals from measurements of cloud fluxes and radiances. Sensitivity studies indicate that computing net longwave fluxes at the surface to within... |
