Numerical Simulation Study Of The Sensitivity Of Ice Crystal Particle Spectral Shape Parameters In Climate Models

There are distinct simplifications and uncertainties in the representation of ice clouds in climate models.In this study,the ice crystal radius distribution spectrum shape parameter(),which defaults to zero by the CAM5 mode cloud microphysics scheme,is extended to an adjustable parameter to analyze the effect of on ice cloud microphysical processes,cloud properties,cloud radiative forcing,precipitation,and the anthropogenic aerosol effects.Off-line tests show that the leads the ice particle size distribution(PSD)more concentrated and impacts the ice phase cloud microphysical processes such as sedimentation,Wegener–Bergeron–Findeisen process,and auto-conversion of cloud ice to snow.The results of SCAM5(single column)show that the increase of is not conducive to the auto-conversion of ice crystals to snow,which leads to an increase in the mass mean radius of ice crystals and produces more complex effects in the microphysical process.The sensitivity of CAM5(global)to mainly has the following three aspects: can significantly change the model's simulation of cloud climate properties by affecting the process of ice cloud microphysical process. increases from 0 to 5,the global average cloud ice content will increase from 0.8 to 1.78 8)2)8),the amount of high clouds will increase from27.63% to 32.88%,and the total precipitation will decrease from 2.97 to 2.77 8)8)(9(6.has a weak effect on cloud microphysical processes through the ice effective radius of ice clouds,and has a significant impact on cloud properties and cloud radiative forcing,and thus has a significant impact on tropical convective precipitation. has an impact on the climatic effects of anthropogenic aerosols through ice clouds.The increase of will increase the high clouds and cause heating,which affects the nucleation of ice crystals,and leads to a significant decrease of the ice number.In shorts,the climate model simulation results suggest that cloud microphysical processes,cloud properties,cloud radiative forcing,precipitation,and the anthropogenic aerosol effects are obviously sensitive to the ice spectra shape parameter and more attention needs to be paid to describe the ice spectra shape parameter in the cloud microphysics scheme.