| In recent years,there has been increasing attention to the study of ice nuclei in clouds,considered a major source of uncertainty in atmospheric modeling.The development of ice nuclei parameterization is also a focal area,with many uncertainties still existing in the interactions between ice nuclei and clouds.Notably,there are ongoing challenges regarding the properties of aerosols and their impact on the formation of ice nuclei.Challenges stem from factors such as the irregular shape of ice crystals,which makes them difficult to accurately observe,and persistent debates about the development of ice nuclei parameterization.Despite these hurdles,the progress in ice nuclei parameterization research has laid the groundwork for improved modeling of clouds and has prompted investigations into aerosol-cloud interaction feedback mechanisms.The primary conclusions are as follows:(1)Based on the Morrison microphysics scheme,ice nuclei parameterization was improved,and a control experiment as well as two improved experiments,the Thom experiment,and the Coupling experiment,were designed.Comparisons and validations with assimilated data and radar observations revealed that the Coupling experiment is more accurate in terms of spatial distribution of precipitation intensity,time series,cloud characteristics,and aerosols,than the Control and Thom experiments.Notably,the Coupling experiment demonstrated superior control of spatial correlation and error in precipitation volume modeling in southern Gansu(near SACOL),and superior cloud characteristics when compared directly with the KAZR cloud radar.The regression slope and correlation coefficient were 0.66 and 0.53,respectively,indicating a more accurate simulation of ice nucleation through a more comprehensive coupling of WRF and Chem modules.(2)Further analysis revealed that the generation of ice crystals above-40°C decreased in the Coupling experiment,while snow and graupel particles increased by11.4% and 32.1% between 0 and-40°C,respectively.This led to enhanced coalescence with cloud droplets and raindrops.The generation of more ice particles resulted in a greater release of latent heat of condensation,heating the atmosphere and strengthening vertical upward movement.This led to further cloud development and an overall increase in total water content,delaying the occurrence of precipitation extremes by half an hour and increasing it by 25%.The improvements in the Coupling experiment were primarily achieved by enhancing the efficiency of heterogeneous nucleation,competing for water vapor,and weakening homogenous nucleation,leading to more cloud condensation,greater latent heat release,and strengthened vertical movement,thereby delaying and intensifying precipitation.(3)Using the enhanced ice nuclei parameterization scheme,sensitivity tests were established to isolate the impact of ice nuclei(IN)and cloud condensation nuclei(CCN)on the development of clouds and precipitation,which may lead to varying feedback effects.Specifically,the interaction between IN and clouds constitutes a negative feedback process,whereas the regulatory role of CCN-cloud interaction is positive feedback.In the case of convective cloud precipitation,an increase in IN results in the development of cloud layers,intensified precipitation,and increased ground-reaching radiation,leading to the reduction of pollutants through processes such as wet deposition and elevation of the boundary layer,thereby decreasing the quantity of ice nuclei.On the other hand,the interaction between CCN and clouds results in an increase in CCN leading to a decrease in raindrop radius,enhanced evaporation,thinning of the cloud layer,weakened precipitation,lowering of the boundary layer,making it difficult for pollutants to spread and be removed by wet methods,which eventually leads to an additional increase in CCN.This demonstrates that fixing IN at a lower value disrupts the fine-tuning between the meteorological field and pollutants.It indirectly reflects the importance of the negative feedback mechanism in the self-regulation process of the interaction between IN and clouds.The improvement of ice nuclei parameterization simulation has improved the feedback mechanism for clouds and precipitation,as well as for air quality. |
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