1. Hallet-Mossop Process as a Mechanism for Ice Multiplication Steven Brown Atmospheric Sciences 5/16/2011

2. Outline Role of Ice Particles in precipitation Evidence for Ice Multiplication What is the Hallet-Mossop Process? Initial Experiment Additional Parameterizations Conclusion

3. Motivation ICE is complicated: diverse morphologies, shapes and sizes Influences: radiation feedback, cloud formation, precipitation, etc. Better understanding of ice in atmosphere - >better understanding of dynamics of atmsphere

4. Ice Formation Ice formed via ▫Homogeneous nucleation  No nuclei present  At temperatures <-34°C ▫Heterogeneous nucleation  Nuclei are present  Best nuclei: size, in-soluble, similar lattice structure Heterogeneous nucleation of supercooled liquid water drops http://youtu.be/O0uwGlgkgfY

5. Evidence for Ice Multiplication Fletcher-Ice Nuclei Curve Meyes –Ice Nuclei Curve

6. Hobbs, V. P. (1968). Ice Multiplication in Clouds. Journal of the Atmospheric Sciences, 315-318.

7. No one-to-one relation between ice nuclei and ice particle concentration Must be secondary process for ice crystal formation -  Ice Multiplication

8. Hallet Mossop Process Hallett, J., & Mossop, S. C. (1974, May 3). Production of secondary ice particles during the riming process. Nature, 249, 26-28.

9. Hallet Mossop Process

10. Hallet-Mossop Process Parameterization

11. Conclusions Hallet-Mossop process best candidate for Ice Multiplication Mechanism More work to be done: ▫Correlate with droplet size, fall speed, rimer size ▫Develop theoretical explanation of mechanism Better understanding of process->better understanding of microphysical properties of clouds

12. Bibliography Supercooled Water Droplets. (2011, January 11). Retrieved May 8, 2011, from SkyLibary: http://www.skybrary.aero/index.php/Supercooled_Water_Droplets Barrel, J. A. (n.d.). Choularton, T. W. (1978, August 24). A Possible Mechanism of Ice Splinter Production During Riming. Nature, 274, 791-792. Connolly, P. J. (2006, May 5). Modeling the influence of rimer surface temperature on the glaciation of intense thunderstorms; The Rime-Splinter Mechanism of Ice Multiplication. Quarterly Journal of the Roal Meteorological Society, 132, 3059-3077. Griggs, D. J., & Choularton, T. W. (1983, January). Freezing modes of riming droplets with application to ice splinter production. Quarterly Journal of the Royal Meteorological Society, 109(459), 243-253. Hallett, J., & Mossop, S. C. (1974, May 3). Production of secondary ice particles during the riming process. Nature, 249, 26-28. Heymsfield, A. J., & Mossop, S. C. (1984). Temperature depedence of secondary ice crystal production during soft hail growth by riming. Quarterly Journal of the Royal Meteorological Society(110), 765-770. Hobbs, V. P. (1968). Ice Multiplication in Clouds. Journal of the Atmospheric Sciences, 315-318. King, W. D., & Fletcher, H. D. (1976). Thermal Shock as an Ice Multiplication Mechanism. Journal of Atmospheric Sciences, 85-96. Mossop, S. C. (1985, March 1985). The Origin and Concentraion of Ice Crystals in Clouds. American Meteorological Society, 66(3), 264-273. Pitter, R. L., & Pruppacher, H. R. (1973). Awind tunnel investigation of reezig of small water drops falling at terminal velocity in air. Quarterly Journal of Meteorological Sciences(99), 540-550. Pruppacher, H. R., & Klett, D. J. (1997). Microphysics of Clouds and Precipitation. New York: Kluwer Academic Publishers. Pruppacher, H. R., & Klett, J. D. (1975). A wind tunnel inverstigation on ice multiplication by freezing of water drops falling at terminal velocity in air. Geophysical Research Letters, 80, 380-381. Rangno, A. L. (2008, April). Fragmentation of Freezing Drops in Shallow Maritime Frontal Clouds. American Meteorological Society, 65, 1455-1466. Strangeways, I. (2007). Cloud droplets, ice particles and precipitation. In I. Strangeways, Precipitation: Theory, Measurement and Distribution (pp. 106-118). Cambridge : Cambridge University Press. Wallace, J. M., & Hobbs, P. V. (2006). Atmospheric Science: An Introductory Survey. London: Academic Press.