Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 9 1 2009 10.5194/acp-9-155-2009 http://www.atmos-chem-phys.net/9/155/2009/ http://www.atmos-chem-phys.net/9/155/2009/acp-9-155-2009.html http://www.atmos-chem-phys.net/9/155/2009/acp-9-155-2009.pdf 155 161 2009-01-12 Cloud's Center of Gravity – a compact approach to analyze convective cloud development I. Koren ilan.koren@weizmann.ac.il O. Altaratz G. Feingold Z. Levin T. Reisin Dept. of Environ. Sciences Weizmann Institute, Rehovot, Israel NOAA Earth System Research Laboratory, Boulder, Colorado, USA Dept. of Geophysics and Planetary Sciences, Tel Aviv University, Tel Aviv, Israel Soreq Nuclear Research Center, Yavne, Israel As cloud resolving models become more detailed, with higher resolution outputs, it is often complicated to isolate the physical processes that control the cloud attributes. Moreover, due to the high dimensionality and complexity of the model output, the analysis and interpretation of the results can be very complicated. Here we suggest a novel approach to convective cloud analysis that yields more insight into the physical and temporal evolution of clouds, and is compact and efficient. The different (3-D) cloud attributes are weighted and projected onto a single point in space and in time, that has properties of, or similar to, the Center Of Gravity (COG). The location, magnitude and spread of this variable are followed in time. The implications of the COG approach are demonstrated for a study of aerosol effects on a warm convective cloud. We show that in addition to reducing dramatically the dimensionality of the output, such an approach often enhances the signal, adds more information, and makes the physical description of cloud evolution clearer, allowing unambiguous comparison of clouds evolving in different environmental conditions. This approach may also be useful for analysis of cloud data retrieved from surface or space-based cloud radars. Cotton, W. R., Pielke, R. A., Walko, R. L., Liston, G. E., Tremback, C. J., Jiang, H., McAnelly, R. L., Harrington, J. Y., Nicholls, M. E., Carrio, G. G., and McFadden, J. P.: RAMS 2001: Current status and future directions, Meteo. Atmos. Phys., 82, 5–29, 2003. Feynman, R., Leighton, R., and Matthew, S.: Center of Mass Moment of Inertia – The Feynman Lectures on Physics, Addison Wesley, Vol 1, Chapter~19, ISBN 0-201-02116-1, 19-1–19-4, 1963. IPCC: The Intergovernmental Panel on Climate Change (IPCC) website, http://www.ipcc.ch/SPM2feb07.pdf, 2007. Levin, Z. and Cotton, W. R.: Aerosol Pollution Impact on Precipitation: A Scientific Review, WMO/IUGG International Aerosol Precipitation Science Assessment Group (IAPSAG), 485 pp., 2007. Meyers, M. P., Walko, R. L., Harrington, J. Y., and Cotton, W. R.: New RAMS cloud microphysics parameterization. Part II: The two-moment scheme., Atmos. Res., 45, 3–39, 1997. Stephens, G. L., Vane, D. G., Boain, R. J., Mace, G. G., Sassen, K.,, Wang, Z., Illingworth, A. J., O'Connor, E. J., Rossow, W. B., Durden, S. L., Miller, S. D., Austin, R. T., Benedetti, A., and Mitrescu, C.: The cloudsat mission and the a-train, A New Dimension of Space-Based Observations of Clouds and Precipitation, Bull. Am. Meteor. Soc., 83(12), 1771–1790, 2002. Teller, A. and Levin, Z.: Factorial method as a tool for estimating the relative contribution to precipitation of cloud microphysical processes and environmental conditions: Method and application, J. Geophys. Res., 113, D02202, doi:10.1029/2007JD008960, 2008. Walko, R., Cotton W. R., Meyers M. P., and Harrington J. Y.,: New RAMS cloud microphysics parameterization. Part I: The single-moment scheme, Atmos. Res. 38, 29–62, 1995. Walko, R., Cotton, W. R., Feingold, G., and Stevens B.: Efficient computation of vapor and heat diffusion between hydrometeors in a numerical model, Atmos. Res., 53, 171–183, 2000.