ACP Atmospheric Chemistry and Physics ACP Atmos. Chem. Phys. 1680-7324 Copernicus Publications Göttingen, Germany 10.5194/acp-9-4131-2009 The relationship between aerosol and cloud drop number concentrations in a global aerosol microphysics model Pringle K. J. 2 1 Carslaw K. S. 1 Spracklen D. V. 1 Mann G. M. 1 Chipperfield M. P. 1 Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, UK now at: Max-Planck-Institute for Chemistry, Mainz, Germany 22 06 2009 9 12 4131 4144 Copyright: © 2009 K. J. Pringle et al. 2009 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/9/4131/2009/acp-9-4131-2009.html The full text article is available as a PDF file from https://acp.copernicus.org/articles/9/4131/2009/acp-9-4131-2009.pdf

Empirical relationships that link cloud droplet number (CDN) to aerosol number or mass are commonly used to calculate global fields of CDN for climate forcing assessments. In this work we use a sectional global model of sulfate and sea-salt aerosol coupled to a mechanistic aerosol activation scheme to explore the limitations of this approach. We find that a given aerosol number concentration produces a wide range of CDN concentrations due to variations in the shape of the aerosol size distribution. On a global scale, the dependence of CDN on the size distribution results in regional biases in predicted CDN (for a given aerosol number). Empirical relationships between aerosol number and CDN are often derived from regional data but applied to the entire globe. In an analogous process, we derive regional "correlation-relations" between aerosol number and CDN and apply these regional relations to calculations of CDN on the global scale. The global mean percentage error in CDN caused by using regionally derived CDN-aerosol relations is 20 to 26%, which is about half the global mean percentage change in CDN caused by doubling the updraft velocity. However, the error is as much as 25–75% in the Southern Ocean, the Arctic and regions of persistent stratocumulus when an aerosol-CDN correlation relation from the North Atlantic is used. These regions produce much higher CDN concentrations (for a given aerosol number) than predicted by the globally uniform empirical relations. CDN-aerosol number relations from different regions also show very different sensitivity to changing aerosol. The magnitude of the rate of change of CDN with particle number, a measure of the aerosol efficacy, varies by a factor 4. CDN in cloud processed regions of persistent stratocumulus is particularly sensitive to changing aerosol number. It is therefore likely that the indirect effect will be underestimated in these important regions.

 References Abdul-Razzak, H. and Ghan, S J.: A parameterization of aerosol activation, 2, Multiple aerosol types, J. Geophys. Res.-Atmos., 105, 6837–6844, \doi10.1029/1999JD901161, 2000. Abdul-Razzak, H. and Ghan, S J.: A parameterization of aerosol activation 3. Sectional representation, J. Geophys. Res.-Atmos., 107, 4026, \doi10.1029/2001JD000483, 2002. Abdul-Razzak, H., Ghan, S J., and Rivera-Carpio, C.: A parameterization of aerosol activation 1. Single aerosol type, J. Geophys. Res.-Atmos., 103, 6123–6132, \doi10.1029/97JD03735, 1998. Adams, P. and Seinfeld, J.: Disproportionate impact of particulate emissions on global cloud condensation nuclei concentrations, Geophys. Res. Lett., 30, 43–46, 2003. Andreae, M O. and Rosenfeld, D.: Aerosol-cloud-precipitation interactions. Part 1. The nature and sources of cloud-active aerosols, Earth. Sci. Rev., 89, 13–41, \doi10.1016/j.earscirev.2008.03.001, 2008. Bauer, E., Petoukhov, V., Ganopolski, A., and Eliseev, A.: Climatic response to anthropogenic sulphate aerosols versus well-mixed greenhouse gases from 1850 to 2000 AD in CLIMBER-2, J. Geophys. Res.-Atmos., 60, 82–97, 2008. Benkovitz, C.: Global gridded inventories of anthropogenic emissions of sulfur and nitrogen, J. Geophys. Res.-Atmos., 101, 29239–29253, 1996. Bennartz, R.: Global assessment of marine boundary layer cloud droplet number concentration from satellite, J. Geophys. Res.-Atmos., 112, D02201, \doi10.1029/2006JD007547, 2007. Boucher, O. and Lohmann, U.: The sulfate-CCN-cloud. albedo effect, A sensitivity study with two general circulation models, Tellus Ser. B., 47, 281–300, 1995. Chen, Y. and Penner, J E.: Uncertainty analysis for estimates of the first indirect aerosol effect, Atmos. Chem. Phys., 5, 2935–2948, 2005. Chipperfield, M.: New Version of the TOMCAT/SLIMCAT Off-Line Chemical Transport Model: Intercomparison of Stratospheric Tracer Experiments, Q. J. Roy. Meteor. Soc., 132, 1179–1203, \doi10.1256/qj.05.51, 2006. Chuang, C., Penner, J., Prospero, J., Grant, K., Rau, G., and Kawamoto, K.: Cloud susceptibility and the first aerosol indirect forcing: Sensitivity to black carbon and aerosol concentrations, J. Geophys. Res.-Atmos., 107(D21), \doi10.1029/2000JD000215, 2002. Dusek, U., Frank, G P., Hildebrandt, L., Curtius, J., Schneider, J., Walter, S., Chand, D., Drewnick, F., Hings, S., Jung, D., Borrmann, S., and Andreae, M O.: Size Matters More Than Chemistry for Cloud-Nucleating Ability of Aerosol Particles, Science, 312, 1375–1378, \doi10.1126/science.1125261, 2006. Forster, P., Ramaswamy, V., Artaxo, P., Berntsen, T., Betts, R., Fahey, D., Haywood, J., Lean, J., Lowe, D., Myhre, G., Nganga, J., Prinn, R., Raga, G., Schulz, M., and Van~Dorland, R.: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, 2007. Fountoukis, C. and Nenes, A.: Continued Development of a Cloud Droplet Formation Parameterization for Global Climate Models, J. Geophys. Res.-Atmos., 110, D11212, \doi10.1029/2004JD005591, 2005. Fountoukis, C., Nenes, A., Meskhidze, N., Bahreini, R., Conant, W C., Jonsson, H Murphy, S., Sorooshian, A., Varutbangkul, V., Brechtel, F., Flagan, R C., and Seinfeld, J H.: Aerosol cloud drop concentration closure for clouds sampled during the International Consortium for Atmospheric Research on Transport and Transformation 2004 campaign, J. Geophys. Res.-Atmos., 112, D10S30, \doi10.1029/2006JD007272, 2007. Ghan, S., Easter, R., Hudson, J., and Breon, F.-M.: Evaluation of aerosol indirect radiative forcing in MIRAGE, J. Geophys. Res.-Atmos., 106, 5317–5334, 2001. Gultepe, I. and Isaac, G A.: Scale effects on averaging of cloud droplet and aerosol number concentrations: observations and models, J. Climate, 12, 1268–1279, 1999. Hallberg, A., Noone, K J., and Ogren, J A.: Aerosol particles and clouds: which particles form cloud droplets?, Tellus. B, 50, 59–75, 1998. Jones, A., Roberts, D., and Slingo, A.: A climate model study of indirect radiative forcing by anthropogenic sulfate aerosols, Nature, 370, 450–453, 1994. Jones, A., Roberts, D., Woodage, M., and Johnson, C.: Indirect sulphate aerosol forcing in a climate model with an interactive sulphur cycle, J. Geophys. Res.-Atmos., 106, 20293–20310, 2001. Kiehl, J., Schneider, T L., Rasch, P J., Barth, M C., and Wong, J.: Radiative forcing due to sulfate aerosols from simulations with the National Center for Atmospheric Research Community Climate Model, version 3, J. Geophys. Res.-Atmos., 105, 1441–1458, 2000. Kirkevag, A., Iversen, T., Kristjansson, J E., Seland, Ø., and Debernard, J B.: On the additivity of climate response to anthropogenic aerosols and CO2, and the enhancement of future global warming by carbonaceous aerosols, Tellus A, 60A, 513–527, 2008. Komppula, M., Lihavainen, H., Kerminen, V M., Kulmala, M., and Viisanen, Y.: Measurements of cloud droplet activation of aerosol particles at a clean subarctic background site, J. Geophys. Res.-Atmos., 110, D06204, \doihttp://dx.doi.org/10.1029/2004JD005200, 2005. Korhonen, H., Carslaw, K S., Spracklen, D V., Mann, G., and Woodhouse, M.: Influence of oceanic DMS emissions on CCN concentrations and seasonality over the remote southern hemisphere oceans: A global model study, J. Geophys. Res.-Atmos., 113(D12), \doi10.1029/2007JD009718, 2008. Kristjansson, J E.: Studies of the aerosol indirect effect from sulfate and black carbon aerosols, J. Geophys. Res.-Atmos., 107(D15), \doi10.1029/2001JD000887, 2002. Kristjansson, J E., Iversen, T., Kirkevåg, A., Seland, Ø., and Debernard, J.: Response of the climate system to aerosol direct and indirect forcing: Role of cloud feedbacks, J. Geophys. Res.-Atmos., 110, D24206, \doi10.1029/2005JD006299, 2005. Kulmala, M., Laaksonen, A., and Pirjola, L.: Parameterization for sulfuric acid/water nucleation rates, J. Geophys. Res.-Atmos., 103, 8301–8307, 1998. Lohmann, U. and Feichter, J.: Global indirect aerosol effects: a review, Atmos. Chem. Phys., 5, 715–737, 2005. Lohmann, U., Feichter, J., Chuang, C C., and Penner, J E.: Prediction of the number of cloud droplets in the ECHAM GCM, J. Geophys. Res.-Atmos., 104, 9169–9198, 1999. Lohmann, U., Feichter, J., Penner, J., and Leaitch, R.: Indirect effect of sulfate and carbonaceous aerosols: A mechanistic treatment, J. Geophys. Res.-Atmos., 105, 12193–12206, \doi10.1029/1999JD901199, 2000. Lowenthal, D H., Borys, R D., Choularton, T W., Bower, K N., Flynn, M J., and Gallagher, M W.: Parameterization of the cloud droplet-sulfate relationship, Atmos. Environ., 38, 287–292, 2004. Ma, X., von Salzen, K., and Li, J.: Modelling sea salt aerosol and its direct and indirect effects on climate, Atmos. Chem. Phys., 8, 1311–1327, 2008. Martin, G., Johnson, D., and Spice, A.: The measurement and parameterization of effective radius of droplets in warm stratiform clouds, J. Atmos. Sci., 51, 1823–1842, 1994. McComiskey, A. and Feingold, G.: Quantifying error in the radiative forcing of the first aerosol indirect effect, Geophys. Res. Lett., 35, L02810, \doi10.1029/2007GL032667, 2008. McFiggans, G., Artaxo, P., Baltensperger, U., Coe, H., Facchini, M C., Feingold, G., Fuzzi, S., Gysel, M., Laaksonen, A., Lohmann, U., Mentel, T F., Murphy, D M., O'Dowd, C D., Snider, J R., and Weingartner, E.: The effect of physical and chemical aerosol properties on warm cloud droplet activation, Atmos. Chem. Phys., 6, 2593–2649, 2006. Menon, S. and Rotstayn, L.: The radiative influence of aerosol effects on liquid-phase cumulus and stratiform clouds based on sensitivity studies with two climate models, Climate Dynam., 27(4), \doi10.1007/s00382-006-0139-3, 2007. Menon, S., Del~Genio, A D., Dorothy, K., and Tselioudis, G.: GCM simulations of the aerosol indirect effect: Sensitivity to cloud parameterization and aerosol burden, J. Atmos. Sci., 59, 692–713, 2002. Menon, S., Brenguier, J.-L., Boucher, O., Davison, P., Del~Genio, A D., Feichter, J., Ghan, S., Guibert, S., Liu, X., Lohmann, U., Pawlowska, H., Penner, J E., Quaas, J., Roberts, D L., Schuller, L., and Snider, J.: Evaluating aerosol/cloud/radiation process parameterizations with single-column models and Second Aerosol Characterisation Experiment (ACE-2) cloudy column observations, J. Geophys. Res., 108(D24), \doi10.1029/2003JD003902, 2003. Meskhidze, N., Nenes, A., Conant, W C., and Seinfeld, J.: Evaluation of a new Cloud Droplet Activation Parameterization with In Situ Data from CRYSTAL-FACE and CSTRIPE, J. Geophys. Res.-Atmos., 110, D16202, \doi10.1029/2004JD005703, 2005. Meskhidze, N., Sotiropoulou, R. E P., Nenes, A., Kouatchou, J., Das, B., and Rodriguez, J M.: Aerosol-cloud interactions in the NASA GMI: model development and indirect forcing assessments, Atmos. Chem. Phys. Discuss., 7, 14295–14330, 2007. Ming, Y., Ramaswamy, V., Ginoux, P A., Horowitz, L W., and Russell, L M.: Geophysical Fluid Dynamics Laboratory general circulation model investigation of the indirect radiative effects of anthropogenic sulfate aerosol, J. Geophys. Res.-Atmos., 110, D22206, \doi10.1029/2005JD006161, 2005. Ming, Y., Ramaswamy, V., Donner, L J., and Phillips, V. T J.: A new parameterization of cloud droplet activation applicable to general circulation models, J. Atmos. Sci., 63, \doi10.1175/JAS3686.11348-1356, 2006. Nenes, A. and Seinfeld, J H.: Parameterization of cloud droplet formation in global climate models, J. Geophys. Res.-Atmos., 108(4415), \doi10.1029/2002JD002911, 2003. Penner, J E., Quass, J., Storelvmo, T., Takemura, T Boucher, O., Guo, H., Kirkevag, A., Kristjansson, J E., and Seland, O.: Model intercomparision of indirect aerosol effects, Atmos. Chem. Phys., 6, 3391–3405, 2006. Quaas, J., Boucher, O., and Lohmann, U.: Constraining the total aerosol indirect effect in the LMDZ and ECHAM4 GCMs using MODIS satellite data, Atmos. Chem. Phys., 6, 947–955, 2006. Ramanathan, V., Crutzen, P., Kiehl, J., and Rosenfeld, D.: Atmosphere - Aerosols, climate, and the hydrological cycle, Science, 294, 2119–2124, 2001. Rotstayn, L D., Cai, W., Dix, M R., Farquhar, G D., Feng, Y., Ginoux, P., Herzog, M., Ito, A., Penner, J., Roderick, M L., and Wang, M.: Have Australian rainfall and cloudiness increased due to the remote effects of Asian anthropogenic aerosols?, J. Geophys. Res.-Atmos., 112, D09202, \doi10.1029/2006JD007712, 2007. Spracklen, D., Pringle, K., Carslaw, K., Chipperfield, M., and Mann, G.: A global off-line model of size resolved aerosol processes; I. Model development and prediction of aerosol properties, Atmos. Chem. Phys., 5, 2227–2252, 2005a. Spracklen, D., Pringle, K., Carslaw, K., Chipperfield, M., and Mann, G.: A global off-line model of size resolved aerosol processes; II. Importance of uncertainties in microphysical processes, Atmos. Chem. Phys., 5, 3233–3250, 2005b. Spracklen, D V., Carslaw, K S., Kulmala, M., Kerminen, V.-M., Mann, G W., and Sihto, S.-L.: The contribution of boundary layer nucleation events to total particle concentrations on regional and global scales, Atmos. Chem. Phys., 6, 5631–5648, 2006. Spracklen, D V., Pringle, K J., Carslaw, K S., Mann, G W., Manktelow, P., and Heintzenberg, J.: Evaluation of a global aerosol microphysics model against size-resolved particle statistics in the marine atmosphere, Atmos. Chem. Phys., 7, 2073–2090, 2007. Stockwell, D. and Chipperfield, M.: A tropospheric chemical -transport model : Development and validation of the model transport schemes, Q. J. Roy. Meteorol. Soc., 125, 1747–1783, 1999. Takemura, T., Nozawa, T., Emori, S., Nakajima, T Y., and Nakajima, T.: Global three-dimensional simulation of aerosol optical thickness distribution of various origins, J. Geophys. Res.-Atmos., 110, 17853–17874, \doi10.1029/2004JD005029, 2005. Verma, S., Boucher, O., Upadhyaya, H., and Sharma, O.: Sulfate aerosols forcing: An estimate using a three-dimensional interactive chemistry scheme, Atmos. Environ., 40, 7953–7962, 2006. Zhang, Y., Easter, R C., Ghan, S J., and Abdul-Razzak, H.: Impact of aerosol size representation on modeling aerosol-cloud interactions, J. Geophys. Res.-Atmos., 107, 4558, \doi10.1029/2001JD001549, 2002.