ACP Atmospheric Chemistry and Physics ACP Atmos. Chem. Phys. 1680-7324 Copernicus Publications Göttingen, Germany 10.5194/acp-13-5631-2013 Large-eddy simulation of organized precipitating trade wind cumulus clouds Seifert A. https://orcid.org/0000-0001-9760-3550 1 Heus T. 2 Hans-Ertel Centre for Weather Research, Deutscher Wetterdienst, Hamburg, Germany Max Planck Institute for Meteorology, Hamburg, Germany 10 06 2013 13 11 5631 5645 Copyright: © 2013 A. Seifert 2013 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://acp.copernicus.org/articles/13/5631/2013/acp-13-5631-2013.html The full text article is available as a PDF file from https://acp.copernicus.org/articles/13/5631/2013/acp-13-5631-2013.pdf

Trade wind cumulus clouds often organize in along-wind cloud streets and across-wind mesoscale arcs. We present a benchmark large-eddy simulation which resolves the individual clouds as well as the mesoscale organization on scales of O(10 km). Different methods to quantify organization of cloud fields are applied and discussed. Using perturbed physics large-eddy simulation experiments, the processes leading to the formation of cloud clusters and the mesoscale arcs are revealed. We find that both cold pools as well as the sub-cloud layer moisture field are crucial to understand the organization of precipitating shallow convection. Further sensitivity studies show that microphysical assumptions can have a pronounced impact on the onset of cloud organization.

 References Atkinson, B. and Zhang, J.: Mesoscale shallow convection in the atmosphere, Rev. Geophys., 34, 403–431, 1996. Berner, A. H., Bretherton, C. S., and Wood, R.: Large-eddy simulation of mesoscale dynamics and entrainment around a pocket of open cells observed in VOCALS-REx RF06, Atmos. Chem. Phys., 11, 10525–10540, <a href="http://dx.doi.org/10.5194/acp-11-10525-2011">https://doi.org/10.5194/acp-11-10525-2011</a>, 2011. Böing, S.&nbsp;J., Jonker, H. J.&nbsp;J., Siebesma, A.&nbsp;P., and Grabowski, W.&nbsp;W.: Influence of the Subcloud Layer on the Development of a Deep Convective Ensemble, J.&nbsp;Atmos.&nbsp;Sci., 69, 2682–2698, 2012. Bretherton, C., Blossey, P., and Khairoutdinov, M.: An energy-balance analysis of deep convective self-aggregation above uniform SST, J.&nbsp;Atmos.&nbsp;Sci., 62, 4273–4292, 2005. Carbone, R., Tuttle, J., Ahijevych, D., and Trier, S.: Inferences of predictability associated with warm season precipitation episodes, J.&nbsp;Atmos.&nbsp;Sci., 59, 2033–2056, 2002. Cotton, W.&nbsp;R., Bryan, G.&nbsp;H., and van&nbsp;den Heever, S.&nbsp;C.: Storm and cloud dynamics, vol.&nbsp;99 of International Geophysics Series, Academic Press, 2nd edition edn., 2011. de&nbsp;Roode, S., Duynkerke, P., and Jonker, H.: Large-eddy simulation: How large is large enough?, J.&nbsp;Atmos.&nbsp;Sci., 61, 403–421, 2004. Etling, D. and Brown, R.: Roll vortices in the planetary boundary layer: A review, Bound.-Lay. Meteorol., 65, 215–248, <a href="http://dx.doi.org/10.1007/BF00705527">https://doi.org/10.1007/BF00705527</a>, 1993. Jeevanjee, N. and Romps, D.&nbsp;M.: Convective self-aggregation, cold pools, and domain size, Geophys.&nbsp;Res.&nbsp;Lett., 40, 994–998, <a href="http://dx.doi.org/10.1002/grl.50204">https://doi.org/10.1002/grl.50204</a>, 2013. Khairoutdinov, M.&nbsp;F. and Randall, D.&nbsp;A.: {S}imilarity of deep continental cumulus convection as revealed by a three-dimensional cloud-resolving model, J.&nbsp;Atmos.&nbsp;Sci., 59, 2550–2566, <a href="http://dx.doi.org/10.1175/1520-0469(2002)059<2550:SODCCC>2.0.CO;2">https://doi.org/10.1175/1520-0469(2002)059<2550:SODCCC>2.0.CO;2</a>, 2002. Kuang, Z. and Bretherton, C.&nbsp;S.: A mass-flux scheme view of a high-resolution simulation of a transition from shallow to deep cumulus convection, J.&nbsp;Atmos.&nbsp;Sci., 63, 1895–1909, 2006. Li, Y. and Carbone, R.: Excitation of Rainfall over the Tropical Western Pacific, J.&nbsp;Atmos.&nbsp;Sci., 69, 2983–2994, 2012. Malkus, J.: Trade cumulus cloud groups – some observations suggesting a mechanism of their origin, Tellus, 9, 33–44, 1957. Malkus, J. and Riehl, H.: Cloud structure and distributions over the tropical pacific ocean, Tellus, 16, 275–287, 1964. Matheou, G., Chung, D., Nuijens, L., Stevens, B., and Teixeira, J.: On the Fidelity of Large-Eddy Simulation of Shallow Precipitating Cumulus Convection, Mon.&nbsp;Weather&nbsp;Rev., 139, 2918–2939, 2011. Minor, H.&nbsp;A., Rauber, R.&nbsp;M., G{ö}ke, S., and Di&nbsp;Girolamo, L.: Trade Wind Cloud Evolution Observed by Polarization Radar: Relationship to Giant Condensation Nuclei Concentrations and Cloud Organization, J.&nbsp;Atmos.&nbsp;Sci., 68, 1075–1096, <a href="http://dx.doi.org/10.1175/2010JAS3675.1">https://doi.org/10.1175/2010JAS3675.1</a>, 2011. Muller, C.&nbsp;J. and Held, I.&nbsp;M.: Detailed Investigation of the Self-Aggregation of Convection in Cloud-Resolving Simulations, J.&nbsp;Atmos.&nbsp;Sci., 69, 2551–2565, 2012. M{ü}ller, G. and Chlond, A.: Three-dimensional numerical study of cell broadening during cold-air outbreaks, Bound.-Lay. Meteorol., 81, 289–323, 1996. Nair, U., Weger, R., Kuo, K., and Welch, R.: Clustering, randomness, and regularity in cloud fields – 5. The nature of regular cumulus cloud fields, J.&nbsp;Geophys.&nbsp;Res., 103, 11363–11380, <a href="http://dx.doi.org/10.1029/98JD00088">https://doi.org/10.1029/98JD00088</a>, 1998. Nicholls, S. and LeMone, M.: The fair weather boundary-layer in GATE: The relationship of sub-cloud fluxes and structure to the distribution and enhancement of cumulus clouds, J.&nbsp;Atmos.&nbsp;Sci., 37, 2051–2067, 1980. Randall, D. and Huffman, G.: A stochastic-model of cumulus clumping, J.&nbsp;Atmos.&nbsp;Sci., 37, 2068–2078, 1980. Rauber, R.&nbsp;M., Stevens, B., Ochs, III, H.&nbsp;T., Knight, C., Albrecht, B.&nbsp;A., Blyth, A.&nbsp;M., Fairall, C.&nbsp;W., Jensen, J.&nbsp;B., Lasher-Trapp, S.&nbsp;G., Mayol-Bracero, O.&nbsp;L., Vali, G., Anderson, J.&nbsp;R., Baker, B.&nbsp;A., Bandy, A.&nbsp;R., Burnet, E., Brenguier, J.&nbsp;L., Brewer, W.&nbsp;A., Brown, P. R.&nbsp;A., Chuang, P., Cotton, W.&nbsp;R., Girolamo, L.&nbsp;D., Geerts, B., Gerber, H., Goke, S., Gomes, L., Heikes, B.&nbsp;G., Hudson, J.&nbsp;G., Kollias, P., Lawson, R.&nbsp;P., Krueger, S.&nbsp;K., Lenschow, D.&nbsp;H., Nuijens, L., O'Sullivan, D.&nbsp;W., Rilling, R.&nbsp;A., Rogers, D.&nbsp;C., Siebesma, A.&nbsp;P., Snodgrass, E., Stith, J.&nbsp;L., Thornton, D.&nbsp;C., Tucker, S., Twohy, C.&nbsp;H., and Zuidema, P.: Rain in shallow cumulus over the ocean – The RICO campaign, B.&nbsp;Am.&nbsp;Meteorol.&nbsp;Soc., 88, 1912–1928, <a href="http://dx.doi.org/10.1175/BAMS-88-12-1912">https://doi.org/10.1175/BAMS-88-12-1912</a>, 2007. Rotunno, R., Klemp, J.&nbsp;B., and Weisman, M.&nbsp;L.: A theory for strong, long-lived squall lines, J.&nbsp;Atmos.&nbsp;Sci., 45, 463–485, 1988. Savic-Jovcic, V. and Stevens, B.: The structure and mesoscale organization of precipitating stratocumulus, J.&nbsp;Atmos.&nbsp;Sci., 65, 1587–1605, 2008. Seifert, A.: On the parameterization of evaporation of raindrops as simulated by a one-dimensional rainshaft model, J.&nbsp;Atmos.&nbsp;Sci., 65, 3608–3619, 2008. Seifert, A. and Beheng, K.&nbsp;D.: A double-moment parameterization for simulating autoconversion, accretion and selfcollection, Atmos.&nbsp;Res., 59–60, 265–281, 2001. Seifert, A., Sakradzija, M., Heus, T., and Stevens, B.: Resolution and domain size requirements for the large-eddy simulation of precipitating trade wind cumulus, in: Proc.&nbsp;16th Int.&nbsp;Conf.&nbsp;Clouds and Precip., Leipzig, Germany, 2012. Siebesma, A., Bretherton, C., Brown, A., Chlond, A., Cuxart, J., Duynkerke, P., Jiang, H., Khairoutdinov, M., Lewellen, D., Moeng, C., Sanchez, E., Stevens, B., and Stevens, D.: A large eddy simulation intercomparison study of shallow cumulus convection, J.&nbsp;Atmos.&nbsp;Sci., 60, 1201–1219, 2003. Snodgrass, E.&nbsp;R., Di&nbsp;Girolamo, L., and Rauber, R.&nbsp;M.: Precipitation Characteristics of Trade Wind Clouds during RICO Derived from Radar, Satellite, and Aircraft Measurements, J.&nbsp;Appl.&nbsp;Met., 48, 464–483, 2009. Stevens, B.: Introduction to UCLA-LES, Version 3.2.1, available from: Gitorious at <a href="https://gitorious.org/uclales">https://gitorious.org/uclales</a>, 2010. Stevens, B. and Seifert, A.: Understanding macrophysical outcomes of microphysical choices in simluations of shallow cumulus convection, J.&nbsp;Met.&nbsp;Soc.&nbsp;Jap., 86, 143–162, 2008. Stevens, B., Moeng, C., and Sullivan, P.: Large-eddy simulations-of radiatively driven convection: Sensitivities to the representation of small scales, J.&nbsp;Atmos.&nbsp;Sci., 56, 3963–3984, 1999. Stevens, B., Moeng, C., Ackerman, A., Bretherton, C., Chlond, A., de&nbsp;Roode, S., Edwards, J., Golaz, J., Jiang, H., Khairoutdinov, M., Kirkpatrick, M., Lewellen, D., Lock, A., Muller, F., Stevens, D., Whelan, E., and Zhu, P.: Evaluation of large-Eddy simulations via observations of nocturnal marine stratocumulus, Mon.&nbsp;Weather&nbsp;Rev., 133, 1443–1462, 2005. Tompkins, A.: Organization of tropical convection in low vertical wind shears: The role of cold pools, J.&nbsp;Atmos.&nbsp;Sci., 58, 1650–1672, 2001. Tompkins, A.: A prognostic parameterization for the subgrid-scale variability of water vapor and clouds in large-scale models and its use to diagnose cloud cover, J.&nbsp;Atmos.&nbsp;Sci., 59, 1917–1942, 2002. van&nbsp;Zanten, M., Stevens, B., Nuijens, L., Siebesma, A., Ackerman, A., Burnet, F., Cheng, A., Couvreux, F., Jiang, H., Khairoutdinov, M., Kogan, Y., Lewellen, D., Mechem, D., Nakamura, K., Noda, A., Shipway, B., Slawinska, J., Wang, S., and Wyszogrodzki, A.: Controls on precipitation and cloudiness in simulations of trade-wind cumulus as observed during RICO, J.&nbsp;Adv.&nbsp;Model.&nbsp;Earth Syst., 3, <a href="http://dx.doi.org/10.1029/2011MS000056">https://doi.org/10.1029/2011MS000056</a>, 2011. Wang, H. and Feingold, G.: Modeling Mesoscale Cellular Structures and Drizzle in Marine Stratocumulus. Part I: Impact of Drizzle on the Formation and Evolution of Open Cells, J.&nbsp;Atmos.&nbsp;Sci., 66, 3237–3256, 2009. Warner, C., Simpson, J., Martin, D.&nbsp;W., Suchman, D., Mosher, F.&nbsp;R., and Reinking, R.&nbsp;F.: Shallow Convection on Day 261 of GATE: Mesoscale Arcs, Mon.&nbsp;Weather&nbsp;Rev., 107, 101–112, 1979. Weger, R., Lee, J., Zhu, T., and Welch, R.: Clustering, randomness and regularity in cloud fields: 1. theoretical considerations, J.&nbsp;Geophys.&nbsp;Res., 97, 20519–20536, 1992. Xue, H., Feingold, G., and Stevens, B.: Aerosol effects on clouds, precipitation, and the organization of shallow cumulus convection, J.&nbsp;Atmos.&nbsp;Sci., 65, 392–406, 2008. Zhang, Y., Stevens, B., and Ghil, M.: On the diurnal cycle and susceptibility to aerosol concentration in a stratocumulus-topped mixed layer, Quart.&nbsp;J.&nbsp;Roy.&nbsp;Met.&nbsp;Soc., 131, 1567–1583, 2005. Zuidema, P., Li, Z., Hill, R.&nbsp;J., Bariteau, L., Rilling, B., Fairall, C., Brewer, W.&nbsp;A., Albrecht, B., and Hare, J.: On Trade Wind Cumulus Cold Pools, J.&nbsp;Atmos.&nbsp;Sci., 69, 258–280, 2012.