ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-11-11951-2011 Assessing regional scale predictions of aerosols, marine stratocumulus, and their interactions during VOCALS-REx using WRF-Chem Yang Q. 1 W. I. Gustafson Jr. 1 Fast J. D. 1 Wang H. 1 Easter R. C. 1 Morrison H. 2 Lee Y.-N. 3 Chapman E. G. 1 Spak S. N. 4 Mena-Carrasco M. A. 5 Pacific Northwest National Laboratory, Richland, WA, USA National Center for Atmospheric Research, Boulder, CO, USA Brookhaven National Laboratory, Upton, New York, USA Public Policy Center, University of Iowa, Iowa City, IA, USA Center for Sustainability Research, Universidad Andrés Bello, Santiago, Chile 02 12 2011 11 23 11951 11975 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/11/11951/2011/acp-11-11951-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/11951/2011/acp-11-11951-2011.pdf

This study assesses the ability of the recent chemistry version (v3.3) of the Weather Research and Forecasting (WRF-Chem) model to simulate boundary layer structure, aerosols, stratocumulus clouds, and energy fluxes over the Southeast Pacific Ocean. Measurements from the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) and satellite retrievals (i.e., products from the MODerate resolution Imaging Spectroradiometer (MODIS), Clouds and Earth's Radiant Energy System (CERES), and GOES-10) are used for this assessment. The Morrison double-moment microphysics scheme is newly coupled with interactive aerosols in the model. The 31-day (15 October–16 November 2008) WRF-Chem simulation with aerosol-cloud interactions (AERO hereafter) is also compared to a simulation (MET hereafter) with fixed cloud droplet number concentrations in the microphysics scheme and simplified cloud and aerosol treatments in the radiation scheme. The well-simulated aerosol quantities (aerosol number, mass composition and optical properties), and the inclusion of full aerosol-cloud couplings lead to significant improvements in many features of the simulated stratocumulus clouds: cloud optical properties and microphysical properties such as cloud top effective radius, cloud water path, and cloud optical thickness. In addition to accounting for the aerosol direct and semi-direct effects, these improvements feed back to the simulation of boundary-layer characteristics and energy budgets. Particularly, inclusion of interactive aerosols in AERO strengthens the temperature and humidity gradients within the capping inversion layer and lowers the marine boundary layer (MBL) depth by 130 m from that of the MET simulation. These differences are associated with weaker entrainment and stronger mean subsidence at the top of the MBL in AERO. Mean top-of-atmosphere outgoing shortwave fluxes, surface latent heat, and surface downwelling longwave fluxes are in better agreement with observations in AERO, compared to the MET simulation. Nevertheless, biases in some of the simulated meteorological quantities (e.g., MBL temperature and humidity) and aerosol quantities (e.g., underestimations of accumulation mode aerosol number) might affect simulated stratocumulus and energy fluxes over the Southeastern Pacific, and require further investigation. The well-simulated timing and outflow patterns of polluted and clean episodes demonstrate the model's ability to capture daily/synoptic scale variations of aerosol and cloud properties, and suggest that the model is suitable for studying atmospheric processes associated with pollution outflow over the ocean. The overall performance of the regional model in simulating mesoscale clouds and boundary layer properties is encouraging and suggests that reproducing gradients of aerosol and cloud droplet concentrations and coupling cloud-aerosol-radiation processes are important when simulating marine stratocumulus over the Southeast Pacific.

 References Abel, S. J., Walters, D. N., and Allen, G.: Evaluation of stratocumulus cloud prediction in the Met Office forecast model during VOCALS-REx, Atmos. Chem. Phys., 10, 10541–10559, http://dx.doi.org/10.5194/acp-10-10541-2010doi:10.5194/acp-10-10541-2010, 2010. Albrecht, B. A.: Aerosols, Cloud Microphysics, and Fractional Cloudiness, Science, 245, 1227–1230, 1989. Allen, G., Coe, H., Clarke, A., Bretherton, C., Wood, R., Abel, S. J., Barrett, P., Brown, P., George, R., Freitag, S., McNaughton, C., Howell, S., Shank, L., Kapustin, V., Brekhovskikh, V., Kleinman, L., Lee, Y.-N., Springston, S., Toniazzo, T., Krejci, R., Fochesatto, J., Shaw, G., Krecl, P., Brooks, B., McMeeking, G., Bower, K. N., Williams, P. I., Crosier, J., Crawford, I., Connolly, P., Allan, J. D., Covert, D., Bandy, A. R., Russell, L. M., Trembath, J., Bart, M., McQuaid, J. B., Wang, J., and Chand, D.: South East Pacific atmospheric composition and variability sampled along 20° S during VOCALS-REx, Atmos. Chem. Phys., 11, 5237–5262, http://dx.doi.org/10.5194/acp-11-5237-2011doi:10.5194/acp-11-5237-2011, 2011. Baker, M. B. and Charlson, R. J.: Bistability of CCN Concentrations and Thermodynamics in the Cloud-topped Boundary-Layer, Nature, 345, 142–145, 1990. Blomquist, B. W., Fairall, C. W., Huebert, B. J., Kieber, D. J., and Westby, G. R.: DMS sea-air transfer velocity: Direct measurements by eddy covariance and parameterization based on the NOAA/COARE gas transfer model, Geophys Res Lett, 33, L07601 http://dx.doi.org/10.1029/2006gl025735doi:10.1029/2006gl025735, 2006. Bretherton, C. S., Uttal, T., Fairall, C. W., Yuter, S. E., Weller, R. A., Baumgardner, D., Comstock, K., Wood, R., and Raga, G. B.: The EPIC 2001 stratocumulus study, B. Am. Meteorol. Soc., 85, 967-977, http://dx.doi.org/10.1175/Bams-85-7-96710.1175/BAMS-85-7-967, 2004. Bretherton, C. S., Uchida, J., and Blossey, P. N.: Slow manifolds and multiple equilibria in stratocumulus-capped boundary layers, J. Adv. Model. Earth Syst., 2, 14, http://dx.doi.org/10.3894/JAMES.2010.2.14doi:10.3894/JAMES.2010.2.14, 2010a. Bretherton, C. S., Wood, R., George, R. C., Leon, D., Allen, G., and Zheng, X.: Southeast Pacific stratocumulus clouds, precipitation and boundary layer structure sampled along 20° S during VOCALS-REx, Atmos. Chem. Phys., 10, 10639–10654, http://dx.doi.org/10.5194/acp-10-10639-2010doi:10.5194/acp-10-10639-2010, 2010b. Chapman, E. G., Gustafson Jr., W. I., Easter, R. C., Barnard, J. C., Ghan, S. J., Pekour, M. S., and Fast, J. D.: Coupling aerosol-cloud-radiative processes in the WRF-Chem model: Investigating the radiative impact of elevated point sources, Atmos. Chem. Phys., 9, 945–964, http://dx.doi.org/10.5194/acp-9-945-2009doi:10.5194/acp-9-945-2009, 2009. Clarke, A. D., Owens, S. R., and Zhou, J. C.: An ultrafine sea-salt flux from breaking waves: Implications for cloud condensation nuclei in the remote marine atmosphere, J. Geophys. Res-Atmos., 111, D06202, http://dx.doi.org/10.1029/2005jd006565doi:10.1029/2005jd006565, 2006. de Szoeke, S. P., Fairall, C. W., Wolfe, D. E., Bariteau, L., and Zuidema, P.: Surface Flux Observations on the Southeastern Tropical Pacific Ocean and Attribution of SST Errors in Coupled Ocean-Atmosphere Models, J. Climate, 23, 4152–4174, http://dx.doi.org/10.1175/2010jcli3411.1doi:10.1175/2010jcli3411.1, 2010. De Carlo, P. F., Kimmel, J. R., Trimborn, A., Northway, M. J., Jayne, J. T., Aiken, A. C., Gonin, M., Fuhrer, K., Horvath, T., Docherty, K. S., Worsnop, D. R., and Jimenez, J. L.: Field-deployable, high-resolution, time-of-flight aerosol mass spectrometer, Anal. Chem., 78, 8281–8289, http://dx.doi.org/10.1021/ac061249ndoi:10.1021/ac061249n, 2006. Dunion, J. P. and Velden, C. S.: The impact of the Saharan air layer on Atlantic tropical cyclone activity, B. Am. Meteorol. Soc., 85, 353, http://dx.doi.org/10.1175/BAMS-85-3-353doi:10.1175/BAMS-85-3-353, 2004. Fairall, C. W., Yang, M., Bariteau, L., Edson, J. B., Helmig, D., McGillis, W., Pezoa, S., Hare, J. E., Huebert, B., and Blomquist, B.: Implementation of the Coupled Ocean-Atmosphere Response Experiment flux algorithm with CO2, dimethyl sulfide, and O<sub>3</sub>, J. Geophys. Res-Atmos., 116, C00F09 http://dx.doi.org/10.1029/2010JC006884doi:10.1029/2010JC006884, 2011. Fast, J. D., Gustafson, W. I., Easter, R. C., Zaveri, R. A., Barnard, J. C., Chapman, E. G., Grell, G. A., and Peckham, S. E.: Evolution of ozone, particulates, and aerosol direct radiative forcing in the vicinity of Houston using a fully coupled meteorology-chemistry-aerosol model, J. Geophys. Res-Atmos., 111, D21305, http://dx.doi.org/10.1029/2005jd006721doi:10.1029/2005jd006721, 2006. Fast, J., Aiken, A. C., Allan, J., Alexander, L., Campos, T., Canagaratna, M. R., Chapman, E., DeCarlo, P. F., de Foy, B., Gaffney, J., de Gouw, J., Doran, J. C., Emmons, L., Hodzic, A., Herndon, S. C., Huey, G., Jayne, J. T., Jimenez, J. L., Kleinman, L., Kuster, W., Marley, N., Russell, L., Ochoa, C., Onasch, T. B., Pekour, M., Song, C., Ulbrich, I. M., Warneke, C., Welsh-Bon, D., Wiedinmyer, C., Worsnop, D. R., Yu, X.-Y., and Zaveri, R.: Evaluating simulated primary anthropogenic and biomass burning organic aerosols during MILAGRO: implications for assessing treatments of secondary organic aerosols, Atmos. Chem. Phys., 9, 6191–6215, http://dx.doi.org/10.5194/acp-9-6191-2009doi:10.5194/acp-9-6191-2009, 2009. Garreaud, R. D. and Munoz, R. C.: The low-level jet off the west coast of subtropical South America: Structure and variability, Mon. Weather Rev., 133, 2246–2261, 2005. George, R. C. and Wood, R.: Subseasonal variability of low cloud radiative properties over the southeast Pacific Ocean, Atmos. Chem. Phys., 10, 4047–4063, http://dx.doi.org/10.5194/acp-10-4047-2010doi:10.5194/acp-10-4047-2010, 2010. Gong, S. L., Barrie, L. A., and Blanchet, J. P.: Modeling sea-salt aerosols in the atmosphere .1. Model development, J. Geophys. Res.-Atmos., 102, 3805–3818, 1997. Grell, G. A., Peckham, S. E., Schmitz, R., McKeen, S. A., Frost, G., Skamarock, W. C., and Eder, B.: Fully coupled "online" chemistry within the WRF model, Atmos. Environ., 39, 6957–6975, http://dx.doi.org/10.1016/j.atmosenv.2005.04.027doi:10.1016/j.atmosenv.2005.04.027, 2005. Guenther, A., Karl, T., Harley, P., Wiedinmyer, C., Palmer, P. I., and Geron, C.: Estimates of global terrestrial isoprene emissions using MEGAN (Model of Emissions of Gases and Aerosols from Nature), Atmos. Chem. Phys., 6, 3181–3210, http://dx.doi.org/10.5194/acp-6-3181-2006doi:10.5194/acp-6-3181-2006, 2006. Gustafson, W. I., Chapman, E. G., Ghan, S. J., Easter, R. C., and Fast, J. D.: Impact on modeled cloud characteristics due to simplified treatment of uniform cloud condensation nuclei during NEAQS 2004, Geophys. Res. Lett., 34, L19809, http://dx.doi.org/10.1029/2007gl030021doi:10.1029/2007gl030021, 2007. Hawkins, L. N., Russell, L. M., Covert, D. S., Quinn, P. K., and Bates, T. S.: Carboxylic acids, sulfates, and organosulfates in processed continental organic aerosol over the southeast Pacific Ocean during VOCALS-REx 2008, J. Geophys. Res.-Atmos., 115, D13201, http://dx.doi.org/10.1029/2009jd013276doi:10.1029/2009jd013276, 2010. Hong, S. Y., Noh, Y., and Dudhia, J.: A new vertical diffusion package with an explicit treatment of entrainment processes, Mon. Weather Rev., 134, 2318–2341, 2006. Huneeus, N., Gallardo, L., and Rutllant, J. A.: Offshore transport episodes of anthropogenic sulfur in northern Chile: Potential impact on the stratocumulus cloud deck, Geophys. Res. Lett., 33, L19819, http://dx.doi.org/10.1029/2006gl026921doi:10.1029/2006gl026921, 2006. Jiang, H. L., Feingold, G., and Cotton, W. R.: Simulations of aerosol-cloud-dynamical feedbacks resulting from entrainment of aerosol into the marine boundary layer during the Atlantic Stratocumulus Transition Experiment, J. Geophys. Res.-Atmos., 107, 4813, http://dx.doi.org/10.1029/2001JD001502doi:10.1029/2001JD001502, 2002. Jimenez, P. A., Dudhia, J., Gonzalez-Rouco, J. F., Navarro, J., Montavez, J. P., and Garcia-Bustamante, E.: A revised scheme for the WRF surface layer formation, Mon. Weather Rev., http://dx.doi.org/10.1175/MWR-D-11-00056.1doi:10.1175/MWR-D-11-00056.1, in preparation, 2011. Kleinman, L. I., Daum, P. H., Lee, Y.-N., Lewis, E. R., Sedlacek III, A. J., Senum, G. I., Springston, S. R., Wang, J., Hubbe, J., Jayne, J., Min, Q., Yum, S. S., and Allen, G.: Aerosol concentration and size distribution measured below, in, and above cloud from the DOE G-1 during VOCALS-REx, Atmos. Chem. Phys. Discuss., 11, 17289–17336, http://dx.doi.org/10.5194/acpd-11-17289-2011doi:10.5194/acpd-11-17289-2011, 2011. Loeb, N. G., Kato, S., Loukachine, K., and Manalo-Smith, N.: Angular distribution models for top-of-atmosphere radiative flux estimation from the Clouds and the Earth's Radiant Energy System instrument on the Terra satellite, Part~I: Methodology, J. Atmos. Ocean. Tech., 22, 338–351, 2005. Matsui, T., Masunaga, H., Kreidenweis, S. M., Pielke, R. A., Tao, W. K., Chin, M., and Kaufman, Y. J.: Satellite-based assessment of marine low cloud variability associated with aerosol, atmospheric stability, and the diurnal cycle, J. Geophys. Res-Atmos., 111, D20202, http://dx.doi.org/10.1029/2006jd008056doi:10.1029/2006jd008056, 2006. Monahan, E. C., Spiel, D. E., and Davidson, K. L.: A model of marine aerosol generation via whitecaps and wave disruption, in: Oceanic Whitecaps, edited by: Niocail, E. C. M. a. G. M., Reidel, D., Norwell, 167–174, 1986. Morrison, H., Curry, J. A., and Khvorostyanov, V. I.: A new double-moment microphysics parameterization for application in cloud and climate models, Part~I: Description, J. Atmos. Sci., 62, 1665–1677, 2005. Morrison, H., Thompson, G., and Tatarskii, V.: Impact of Cloud Microphysics on the Development of Trailing Stratiform Precipitation in a Simulated Squall Line: Comparison of One- and Two-Moment Schemes, Mon. Weather Rev., 137, 991–1007, http://dx.doi.org/10.1175/2008mwr2556.1doi:10.1175/2008mwr2556.1, 2009. Nightingale, P. D., Malin, G., Law, C. S., Watson, A. J., Liss, P. S., Liddicoat, M. I., Boutin, J., and Upstill-Goddard, R. C.: In situ evaluation of air-sea gas exchange parameterizations using novel conservative and volatile tracers, Global Biogeochem. Cy., 14, 373–387, 2000. Painemal, D. and Zuidema, P.: Microphysical variability in southeast Pacific Stratocumulus clouds: synoptic conditions and radiative response, Atmos. Chem. Phys., 10, 6255–6269, http://dx.doi.org/10.5194/acp-10-6255-2010doi:10.5194/acp-10-6255-2010, 2010. Qian, Y., Gustafson, W. I., Leung, L. R., and Ghan, S. J.: Effects of soot-induced snow albedo change on snowpack and hydrological cycle in western United States based on Weather Research and Forecasting chemistry and regional climate simulations, J. Geophys. Res-Atmos., 114, D03108, http://dx.doi.org/10.1029/2008jd011039doi:10.1029/2008jd011039, 2009. Rahn, D. A. and Garreaud, R.: Marine boundary layer over the subtropical southeast Pacific during VOCALS-REx - Part 1: Mean structure and diurnal cycle, Atmos. Chem. Phys., 10, 4491–4506, http://dx.doi.org/10.5194/acp-10-4491-2010doi:10.5194/acp-10-4491-2010, 2010. Remer, L. A., Kleidman, R. G., Levy, R. C., Kaufman, Y. J., Tanre, D., Mattoo, S., Martins, J. V., Ichoku, C., Koren, I., Yu, H. B., and Holben, B. N.: Global aerosol climatology from the MODIS satellite sensors, J. Geophys. Res-Atmos., 113, D14S07, http://dx.doi.org/10.1029/2007jd009661doi:10.1029/2007jd009661, 2008. Rogers, R. R. and Yau, M. K.: A short course in cloud physics, 125–126, 1989. Russell, L. M., Hawkins, L. N., Frossard, A. A., Quinn, P. K., and Bates, T. S.: Carbohydrate-like composition of submicron atmospheric particles and their production from ocean bubble bursting, P. Natl. Acad. Sci. USA, 107, 6652–6657, http://dx.doi.org/10.1073/pnas.0908905107doi:10.1073/pnas.0908905107, 2010. Shaw, W. J., Allwine, K. J., Fritz, B. G., Rutz, F. C., Rishel, J. P., and Chapman, E. G.: Evaluation of the wind erosion module in DUSTRAN, Atmos. Environ., 42, 1907–1921, http://dx.doi.org/10.1016/j.atmosenv.2007.11.022doi:10.1016/j.atmosenv.2007.11.022, 2008. Shrivastava, M., Fast, J., Easter, R., Gustafson Jr., W. I., Zaveri, R. A., Jimenez, J. L., Saide, P., and Hodzic, A.: Modeling organic aerosols in a megacity: comparison of simple and complex representations of the volatility basis set approach, Atmos. Chem. Phys., 11, 6639–6662, http://dx.doi.org/10.5194/acp-11-6639-2011doi:10.5194/acp-11-6639-2011, 2011. Skamarock, W. C.: Evaluating mesoscale NWP models using kinetic energy spectra, Mon. Weather Rev., 132, 3019–3032, 2004. Stevens, B. and Feingold, G.: Untangling aerosol effects on clouds and precipitation in a buffered system, Nature, 461, 607–613, http://dx.doi.org/10.1038/nature08281doi:10.1038/nature08281, 2009. Stevens, B., Vali, G., Comstock, K., Wood, R., van Zanten, M. C., Austin, P. H., Bretherton, C. S., and Lenschow, D. H.: Pockets of open cells and drizzle in marine stratocumulus, B. Am. Meteorol. Soc., 86, 51, http://dx.doi.org/10.1175/BAMS-86-1-51doi:10.1175/BAMS-86-1-51, 2005. Toniazzo, T., Abel, S. J., Wood, R., Mechoso, C. R., Allen, G., and Shaffrey, L. C.: Large-scale and synoptic meteorology in the south-east Pacific during the observations campaign VOCALS-REx in austral Spring 2008, Atmos. Chem. Phys., 11, 4977–05009, http://dx.doi.org/10.5194/acp-11-4977-2011doi:10.5194/acp-11-4977-2011, 2011. Twomey, S.: Influence of Pollution on Shortwave Albedo of Clouds, J. Atmos. Sci., 34, 1149–1152, 1977. Wang, H. and Feingold, G.: Modeling Mesoscale Cellular Structures and Drizzle in Marine Stratocumulus. Part II: The Microphysics and Dynamics of the Boundary Region between Open and Closed Cells, J. Atmos. Sci., 66, 3257–3275, http://dx.doi.org/10.1175/2009jas3120.1doi:10.1175/2009jas3120.1, 2009a. 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. Atmos. Sci., 66, 3237–3256, http://dx.doi.org/10.1175/2009jas3022.1doi:10.1175/2009jas3022.1, 2009b. Wang, H., Skamarock, W. C., and Feingold, G.: Evaluation of Scalar Advection Schemes in the Advanced Research WRF Model Using Large-Eddy Simulations of Aerosol-Cloud Interactions, Mon. Weather Rev., 137, 2547–2558, http://dx.doi.org/10.1175/2009mwr2820.1doi:10.1175/2009mwr2820.1, 2009. Wiedinmyer, C., Akagi, S. K., Yokelson, R. J., Emmons, L. K., Al-Saadi, J. A., Orlando, J. J., and Soja, A. J.: The Fire INventory from NCAR (FINN): a high resolution global model to estimate the emissions from open burning, Geosci. Model Dev., 4, 625–641, http://dx.doi.org/10.5194/gmd-4-625-2011doi:10.5194/gmd-4-625-2011, 2011. Wood, R. and Bretherton, C. S.: Boundary layer depth, entrainment, and decoupling in the cloud-capped subtropical and tropical marine boundary layer, J. Climate, 17, 3576–3588, 2004. Wood, R., Bretherton, C. S., Leon, D., Clarke, A. D., Zuidema, P., Allen, G., and Coe, H.: An aircraft case study of the spatial transition from closed to open mesoscale cellular convection over the Southeast Pacific, Atmos. Chem. Phys., 11, 2341–2370, http://dx.doi.org/10.5194/acp-11-2341-2011doi:10.5194/acp-11-2341-2011, 2011a. Wood, R., Mechoso, C. R., Bretherton, C. S., Weller, R. A., Huebert, B., Straneo, F., Albrecht, B. A., Coe, H., Allen, G., Vaughan, G., Daum, P., Fairall, C., Chand, D., Gallardo Klenner, L., Garreaud, R., Grados, C., Covert, D. S., Bates, T. S., Krejci, R., Russell, L. M., de Szoeke, S., Brewer, A., Yuter, S. E., Springston, S. R., Chaigneau, A., Toniazzo, T., Minnis, P., Palikonda, R., Abel, S. J., Brown, W. O. J., Williams, S., Fochesatto, J., Brioude, J., and Bower, K. N.: The VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx): goals, platforms, and field operations, Atmos. Chem. Phys., 11, 627–654, http://dx.doi.org/10.5194/acp-11-627-2011doi:10.5194/acp-11-627-2011, 2011b. Wyant, M. C., Wood, R., Bretherton, C. S., Mechoso, C. R., Bacmeister, J., Balmaseda, M. A., Barrett, B., Codron, F., Earnshaw, P., Fast, J., Hannay, C., Kaiser, J. W., Kitagawa, H., Klein, S. A., Köhler, M., Manganello, J., Pan, H.-L., Sun, F., Wang, S., and Wang, Y.: The PreVOCA experiment: modeling the lower troposphere in the Southeast Pacific, Atmos. Chem. Phys., 10, 4757–4774, http://dx.doi.org/10.5194/acp-10-4757-2010doi:10.5194/acp-10-4757-2010, 2010. Yang, M., Blomquist, B. W., and Huebert, B. J.: Constraining the concentration of the hydroxyl radical in a stratocumulus-topped marine boundary layer from sea-to-air eddy covariance flux measurements of dimethylsulfide, Atmos. Chem. Phys., 9, 9225–9236, http://dx.doi.org/10.5194/acp-9-9225-2009doi:10.5194/acp-9-9225-2009, 2009. Yang, M., Huebert, B. J., Blomquist, B. W., Howell, S. G., Shank, L. M., McNaughton, C. S., Clarke, A. D., Hawkins, L. N., Russell, L. M., Covert, D. S., Coffman, D. J., Bates, T. S., Quinn, P. K., Zagorac, N., Bandy, A. R., de Szoeke, S. P., Zuidema, P. D., Tucker, S. C., Brewer, W. A., Benedict, K. B., and Collett, J. L.: Atmospheric sulfur cycling in the southeastern Pacific - longitudinal distribution, vertical profile, and diel variability observed during VOCALS-REx, Atmos. Chem. Phys., 11, 5079–5097, http://dx.doi.org/10.5194/acp-11-5079-2011doi:10.5194/acp-11-5079-2011, 2011. Zaveri, R. A., Easter, R. C., Fast, J. D., and Peters, L. K.: Model for Simulating Aerosol Interactions and Chemistry (MOSAIC), J. Geophys. Res.-Atmos., 113, D13204, http://dx.doi.org/10.1029/2007jd008782doi:10.1029/2007jd008782, 2008. Zhang, Y., Olsen, S. C., and Dubey, M. K.: WRF/Chem simulated springtime impact of rising Asian emissions on air quality over the US, Atmos. Environ., 44, 2799–2812, http://dx.doi.org/10.1016/j.atmosenv.2010.05.003doi:10.1016/j.atmosenv.2010.05.003, 2010. Zhao, C., Liu, X., Leung, L. R., Johnson, B., McFarlane, S. A., Gustafson Jr., W. I., Fast, J. D., and Easter, R.: The spatial distribution of mineral dust and its shortwave radiative forcing over North Africa: modeling sensitivities to dust emissions and aerosol size treatments, Atmos. Chem. Phys., 10, 8821–8838, http://dx.doi.org/10.5194/acp-10-8821-2010doi:10.5194/acp-10-8821-2010, 2010. Zuidema, P., Painemal, D., de Szoeke, S., and Fairall, C.: Stratocumulus Cloud-Top Height Estimates and Their Climatic Implications, J. Climate, 22, 4652–4666, http://dx.doi.org/10.1175/2009jcli2708.1doi:10.1175/2009jcli2708.1, 2009.