Nonlinear Processes in Geophysics www.nonlin-processes-geophys.net 1023-5809 1607-7946 13 1 2006 10.5194/npg-13-99-2006 http://www.nonlin-processes-geophys.net/13/99/2006/ http://www.nonlin-processes-geophys.net/13/99/2006/npg-13-99-2006.html http://www.nonlin-processes-geophys.net/13/99/2006/npg-13-99-2006.pdf 99 107 2006-04-12 Nonlinear effects in a conceptual multilayer cloud model U. Wacker uwacker@awi-bremerhaven.de Alfred-Wegener-Institut für Polar- und Meeresforschung, 27515 Bremerhaven, Germany As conceptual model for a cloud a system is considered which is open for condensate mass transport and subject to internal processes such as cloud microphysical transformation and vertical condensate transport. The effects of microphysical processes are represented in parameterized form and the system is divided into two layers to account for the vertical structure. The evolution is mathematically described in terms of four coupled nonlinear ODEs; the prognostic variables are the mass concentrations of cloud water as well as precipitation condensate in each of the layers. In the absence of vertical velocity the evolution in the lower layer is triggered by the evolution in the upper layer. In the presence of an upwind, the dynamics in both layers is mutually coupled. Depending on the chosen parameter values up to four steady states are found. When varying the parameter upwind velocity, three regimes are distinguished: For week upwind the long-term evolution is steered by the external sources; for stronger upwind the cloud condensate is blown out of the cloud in the final state and does not contribute to formation of precipitation; for intermediate upwind multiple steady state solution branches arise which characterize the transition between those two regimes. Cotton, W. R. and Anthes, R. A.: Storm and cloud dynamics, San Diego, Academic Press, pp 883, 1989. Doms, G. and Schättler, U.: The nonhydrostatic limited-area model LM (Lokal-Modell) of DWD, Part I: Scientific documentation, Deutscher Wetterdienst (DWD), Offenbach, available at: http://cosmo-model.cscs.ch/public/documentationVer1.htm#sc_doc, 1999. Ebeling, W.: Strukturbildung bei irreversiblen Prozessen, Leipzig, BSB B. G. Teubner Verlagsges., pp 371, 1976. Houze, R. A.: Cloud Dynamics, San Diego, Academic Press, Inc., pp 573, 1993. Jiang, Q. and Smith, R. B.: Cloud timescales and orographic precipitation, J. Atmos. Sci., 60, 1543-1559, 2003. Kessler, E.: On the distribution and continuity of water substance in atmospheric circulations, Meteor. Monogr., 10(32), 84, 1969. Locatelli, J. D. and Hobbs, P. V.: Fall speed and masses of solid precipitation particles, J. Geophys. Res., 79, 2185-2197, 1974. Nicolis, G. and Prigogine, I.: Self-organization in nonequilibrium systems, New York, J. Wiley & Sons, pp 491, 1977. Palmer, A. J.: A spectral model for turbulence and microphysics dynamics in an ice cloud, Nonlin. Processes Geophys., 3, 23-28, 1996. Rauber, R. M., Grant, L. O., Feng, D., and Snider, J. B.: The characteristics and distribution of cloud water over the mountains of Northern Colorado during wintertime storms, J. Climate Appl. Meteorol., 25, 468-488, 1986. Reinhardt, T. and Wacker, U.: Impact of ice particle habits on simulated clouds, Geophys. Res. Lett., 31, L21106, doi:10.1029/2004GL021134, 2004. Reinhardt, T. and Wacker, U.: A winter-time case study on the impact of ice particle habits on simulated clouds and precipitation, Atmos. Res., in press, 2006. Spassova, T. and Nikolov, S.: A hierarchy of nonlinear multiparametric models of cloud dynamics and microphysics, Atmos. Res., 78, 93-102, 2005. Wacker, U.: Structural stability in cloud physics using parameterized microphysics, Beitr. Phys. Atmos., 65, 231-242, 1992. Wacker, U.: Competition of precipitation particles in a model with parameterized cloud microphysics, J. Atmos. Sci., 52, 2577-2589, 1995. Wacker, U.: Qualitative Analyse von dynamischen Systemen der Wolkenmikrophysik, Berlin: Wissenschaft und Technik Verlag, pp 109, 1998.