Recent advances in research on micro–to storm–scale ice microphysical processes in clouds

In this paper, we summarize our recent research results from ice processes in the atmosphere from storm- to microscale. First, we tested the sensitivity of ice processes in a simulated US High Plains supercell storm using a 3–dimensional cloud model by specifying three different ice physics schemes; namely, the control run, the all–liquid run with normal latent heats, and the all–liquid run with latent heat of sublimation. We showed that the absence of ice processes would result in a substantially shorter lifespan of the storm. Furthermore, we showed that this impact is due to the microphysical properties of ice rather than the thermodynamics of the cloud due to latent heat release. Secondly, we tested the sensitivity of ice crystal habits on the development of thin cirrus clouds using a 2-dimensional cirrus model with detailed microphysics. Four different ice crystal habits were studied: plates, columns, rosettes and spheres. The results show that the cirrus development is indeed greatly influenced by the habit of ice crystals in the cloud. The largest differences exist between cirrus consisting of rosettes and that consisting of spheres. The largest impact is in the long-wave heating rates where the peak heating rates between these two cases differ by more than 6 times. Other cloud properties are also significantly influenced by the different habits. Finally, calculations of the ice crystal capacitance for three ice habits: rosettes, solid columns and hollow columns were performed using finite element techniques. The results show that the homomorphic solid and hollow columns of same dimensions have nearly the same capacitance, implying that the mass growth rates of the two are nearly the same but the hollow column will have greater linear growth rate due to its hollowness. The results for rosettes show that the capacitance of rosettes is a nonlinear function of the number of lobes, and hence previous assumptions that their capacitances can be approximated by spheres or prolate/oblate spheroids of the same diameter may result in substantial errors. The computed capacitances can be used in the calculations of crystal growth rates in ice clouds.