Influence of ice nuclei particle parameterization on cloud formation and electrification using the COMMAS 3-D model

Abstract

Ice Nuclei Particles (INP) are aerosol particles that promote the formation of ice crystals in clouds via heterogeneous freezing. A variety of primary INP parameterizations have been developed and implemented into various numerical models. In this research, the idealized cloud model from the National Severe Storms Laboratory (NSSL) Collaborative Model for Atmospheric Simulation (COMMAS) was used to examine the impact of INP parameterization schemes on cloud formation and electrification. The simulations used the NSSL two-moment bulk microphysics scheme that has six hydrometeor categories as well as the electrification and lightning parameterizations in COMMAS. Microphysical processes are known to alter cloud formation, development, and electrification. This study isolates the effects of INP using four primary INP parameterizations available in the COMMAS model: Meyers/Ferrier (1994), Cooper/Thompson (2004), Phillips (2007), and DeMott (2010). By varying these parameterization schemes, the influence of INP on cloud microphysical processes and the associated effects on both hydrometeor parameter formation and electrification were made. The simulation was initialized with an environmental sounding from a small Oklahoma thunderstorm from 29 June 2004, and results were coherent with observational data from the event. Each of the primary INP parameterization schemes uniquely produced activated INP concentrations in the cloud. The primary INP parameterization schemes were found to have the most effect early in the simulation before secondary ice multiplication processes become dominant. The Meyers/Ferrier (1994) scheme activated higher INP concentrations earlier in the model simulation and began producing higher concentrations of various cloud hydrometeors. Variations in dynamic, precipitative and, electric cloud properties (e.g. development of updrafts, downdrafts, total precipitation amounts, charge separation initiation time, and heights) were observed.

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