Numerical Simulation Of The Influence Of Atmospheric Ice Nuclei Concentration On Electrification In Thunderstorms

In order to investigate the effects of different ice nucleus concentration-temperature spectra on the microphysical,electrification and charge structure of thunderstorm clouds,we select three classic ice nucleus spectra for numerical simulation experiments,using the existing two-dimensional?2-D?cumulus model and combined with a case of mountain thunderstorm.On this basis,in order to discuss in detail the effects of different ice nucleus concentrations on electrification in thunderstorms,DeMott nucleation scheme related to aerosol concentration was selected and implanted into the 2D and 3D cumulus model respectively.Aerosol concentration is used to control the concentration of ice nuclei to analyze the effects of different ice nucleus concentrations on the microphysical,electrification,charge structure,precipitation and lightning frequency of thunderstorm clouds.Conclusion as below:?1?Different ice nucleus spectral environments have a great influence on the content and distribution of ice-phase particles in thunderstorm clouds.The larger the vertical temperature zone of the ice nucleus spectral,the wider the distribution of the ice phase particles produced.In the case of a large concentration of ice nucleus,the content of ice crystals and graupel particles is high,more small ice crystals appear in the zone of higher elevations;?2?The number of ice nucleus in high-temperature region has a significant affects the updrafts velocity.More ice nucleus in the high-temperature region leads to more latent heat released by the ice phase particles during the development of the microphysical process,resulting in intensive updrafts and vigorous convection development;?3?In the case of ice nucleus spectral environment with high ice crystal concentration in the low-temperature region,The non-inductive electric rate and inductive electric rate are high in thunderstorm clouds,resulting in increased charge.In the spectral environment with high ice nucleus in high temperature regions,a large number of ice crystals and graupel gain positive charge to form a sub-positive charge zone,and the charge structure exhibits tripolarity;While in a high-temperature zone,dipolar charge structures are easily formed in the spectrum environment with less ice nuclei and less hydrometeors particles participate in electrification.?4?With the increase of ice nucleus concentration,the content of ice crystals and graupel particles increases with the release of a large amount of latent heat,leading to rising winds.However,due to the limited water vapor in the cloud,the size of the ice phase particles is reduced.The number of ice nuclei increases,the heterogeneous nucleation process increases,and the ice crystal content produced by homogenous nucleation decreases.At the same time,cloud droplets and raindrops are reduced.?5?The number of ice nuclei increases,the ice phase particles in the middle and lower layers increase,the electrification process increases,and the charge density of the sub-positive charge region increases.The main positive and negative charge regions have a decreasing charge density because small particle has low collision efficiency.?6?When the aerosol concentration exceeds 5000 cm^-3,the updrafts velocity exceeds 10 m s^-1,and the strong updraft quickly brings the cloud water to the frozen layer,accelerating the formation of ice phase particles,leading to the advancement of the electrification process and the form of charge structure.?7?With the increase of ice nuclei concentration,the accumulated rainfall on the ground decreases,the frequency of lightning increases,and the first occurrence time of intracloud flash and Cloud to Groud Flash is gradually advanced.