Aircraft Observation Of Cloud Microphysical Quantities In Marine Stratocumulus Cloud

Clouds have significant effects on both global and regional atmospheric radiation transport and water cycling.At present,the parameterization of cloud microphysics in weather and climate models is uncertain,which hinders the improvement of cloud precipitation and related processes simulation.Cloud droplet spectral relative dispersion is a key physical quantity for the parameterization of cloud microphysical parameterization,but the current understanding of influence factors of relative dispersion is not enough,which hinders the improvement of the parameterization of the dispersion.Therefore,in this study,aircraft observation data,numerical model and theoretical analysis methods were used to study the cloud microphysical characteristics and the correlation between relative dispersion and volume-mean radius in Marine stratocumulus clouds.The main conclusions are as follows.(1)Variation characteristics of cloud microphysical quantities in Marine Stratocumulus on horizontal and vertical scales.In the horizontal direction,the distribution of cloud microphysical quantity is quite different,especially in the low layer.With the increase of altitude,the difference of level distribution of cloud microphysical quantity decreases,and gradually uniform and regular fluctuation changes.In the vertical direction,due to condensation and significant activation process near the cloud base,cloud droplet number concentration increases,liquid water content and volume-mean radius are smaller,and relative dispersion degree is larger.In the middle layer of the cloud,due to the increase of condensation,liquid water content and volume-mean radius increase with the height,and relative dispersion decreases with height.In the vicinity of the cloud top,there is often a entrainment-mixing process,which reduces the number concentration,liquid water content and volume-mean radius,and increases the dispersion.(2)Relationship between relative dispersion and volume-mean radius in Marine Stratocumulus.At all altitudes,relative dispersion is negatively correlated with the volumemean radius due to condensation growth.In the horizontal direction,the relationship between relative dispersion and volume-mean radius is not simple: mainly positive correlation,and some negative correlation and no correlation.The positive correlation can be divided into two cases:the peak of the mean cloud droplet size distribution is close to the first bin and the peak of the mean cloud droplet size distribution is in the middle.The former is consistent with previous studies,while the latter is a newly discovered phenomenon.There are different influence mechanisms behind different correlations,including condensation,activation,evaporation,vertical velocity fluctuation and cloud base height fluctuation,and influence of relevant physical mechanisms on the correlation between the two is verified by an adiabatic cloud parcel model.In addition,it is found that entrainment-mixing mechanism near the cloud top will lead to different correlations between relative dispersion and volume-mean radius,which is mainly related to the intensity of entrainment-mixing,evaporation and condensation processes in the entrainment-mixing process.In this study,the variation characteristics of cloud microphysical quantity in Marine stratocumulus cloud and the relationship between cloud droplet spectral relative dispersion and volume-mean radius were studied from both horizontal and vertical perspectives.The results are helpful to enhance the theoretical understanding of cloud microphysical characteristics and the influencing factors of relative dispersion,and lay a foundation for the development of cloud microphysical parameterization schemes.