ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-10-4757-2010 The PreVOCA experiment: modeling the lower troposphere in the Southeast Pacific Wyant M. C. 1 Wood R. 1 Bretherton C. S. 1 Mechoso C. R. 2 Bacmeister J. 3 Balmaseda M. A. 4 Barrett B. 5 Codron F. 6 Earnshaw P. 7 Fast J. 8 Hannay C. 9 Kaiser J. W. 4 Kitagawa H. 10 Klein S. A. 11 Köhler M. 4 Manganello J. 12 Pan H.-L. 13 Sun F. 2 Wang S. 14 Wang Y. 15 Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, Los Angeles, CA, USA Global Modeling and Assimiliation Office, NASA Goddard Space Flight Center, Greenbelt, MD, USA Research Department, European Center for Medium-Range Weather Forecasts, Reading, UK Department of Geophysics, University of Chile, Santiago, Chile Université Pierre et Marie Curie, Laboratoire de Meteorologie Dynamique, Paris, France Met Office, Exeter, Devon, UK Atmospheric Sciences and Global Change, Pacific Northwest National Laboratory, Richland, WA, USA Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, CO, USA Meteorological College, Japan Meteorological Agency, Tokyo, Japan Program for Climate Model Diagnosis and Intercomparison, Lawrence Livermore National Laboratory, Livermore, CA, USA Center for Ocean-Land-Atmosphere Studies, Calverton, MD, USA Environmental Modeling Center, National Centers for Environmental Prediction, Camp Springs, Maryland, USA Marine Meteorology Division, Naval Research Laboratory, Monterey, CA, USA International Pacific Research Center, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, HI, USA 26 05 2010 10 10 4757 4774 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/10/4757/2010/acp-10-4757-2010.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/10/4757/2010/acp-10-4757-2010.pdf

The Preliminary VOCALS Model Assessment (PreVOCA) aims to assess contemporary atmospheric modeling of the subtropical South East Pacific, with a particular focus on the clouds and the marine boundary layer (MBL). Models results from fourteen modeling centers were collected including operational forecast models, regional models, and global climate models for the month of October 2006. Forecast models and global climate models produced daily forecasts, while most regional models were run continuously during the study period, initialized and forced at the boundaries with global model analyses. Results are compared in the region from 40° S to the equator and from 110° W to 70° W, corresponding to the Pacific coast of South America. Mean-monthly model surface winds agree well with QuikSCAT observed winds and models agree fairly well on mean weak large-scale subsidence in the region next to the coast. However they have greatly differing geographic patterns of mean cloud fraction with only a few models agreeing well with MODIS observations. Most models also underestimate the MBL depth by several hundred meters in the eastern part of the study region. The diurnal cycle of liquid water path is underestimated by most models at the 85° W 20° S stratus buoy site compared with satellite, consistent with previous modeling studies. The low cloud fraction is also underestimated during all parts of the diurnal cycle compared to surface-based climatologies. Most models qualitatively capture the MBL deepening around 15 October 2006 at the stratus buoy, associated with colder air at 700 hPa.

 References Allan, R., Slingo, A., Milton, S., and Brooks, M.: Evaluation of the Met Office global forecast model using geostationary Earth Radiation Budget (GERB) data, Q. J. Roy. Meteor. Soc., 133, 1993–2010, 2007. Anthes, R., Bernhardt, P., Chen, Y., Cucurull, L., Dymond, K., Ector, D., Healy, S., Ho, S., Hunt, D., Kuo, Y., Liu, H., Manning, K., Mccormick, C., Meehan, T., Randel, W., Rocken, C., Schreiner, W., Sokolovskiy, S., Syndergaard, S., Thompson, D., Trenberth, K., Wee, T., Yen, N., and Zeng, Z.: The COSMIC/FORMOSAT-3 – Mission early results, B. Am. Meteorol. Soc., 89, 313–333, 2008. Boyle, J., Klein, S., Zhang, G., Xie, S., and Wei, X.: Climate model forecast experiments for TOGA COARE, Mon. Weather Rev., 136, 808–832, 2008. Bretherton, C. and Park, S.: A new bulk shallow-cumulus model and implications for penetrative entrainment feedback on updraft buoyancy, J. Atmos. Sci., 65, 2174–2193, 2008. Bretherton, C., Uttal, T., Fairall, C., Yuter, S., Weller, R., Baumgardner, D., Comstock, K., Wood, R., and Raga, G.: The EPIC 2001 stratocumulus study, B. Am. Meteorol. Soc., 85, 967–977, 2004. 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, doi:10.5194/acp-9-945-2009, 2009. Chen, S. and Sun, W.: A one-dimensional time dependent cloud model, J. Meteorol. Soc. Jpn., 80, 99–118, 2002. Colbo, K. and Weller, R.: The variability and heat budget of the upper ocean under the Chile-Peru stratus, J. Mar. Res., 65, 607–637, 2007. Collins, W., Rasch, P., Boville, B., Hack, J., McCaa, J., Williamson, D., Kiehl, J., Briegleb, B., Bitz, C., Lin, S.-J., Zhang, M., and Dai, Y.: Description of the NCAR Community Atmosphere Model (CAM 3.0), Tech. rep., NCAR, 2004. Davies, T., Cullen, M., Malcolm, A., Mawson, M., Staniforth, A., White, A., and Wood, N.: A new dynamical core for the Met Office's global and regional modelling of the atmosphere, Q. J. Roy. Meteor. Soc., 131, 1759–1782, 2005. de~Szoeke, S., Fairall, C., and Pezoa, S.: Ship observations of the tropical Pacific Ocean along the coast of South America, J. Climate, 22, 458–464, 2009. Field, P. and Wood, R.: Precipitation and cloud structure in midlatitude cyclones, J. Climate, 20, 5208–5210, 2007. Garreaud, R. and Munoz, R.: The diurnal cycle in circulation and cloudiness over the subtropical southeast Pacific: A modeling study, J. Climate, 17, 1699–1710, 2004. Garreaud, R., Rutllant, J., Quintana, J., Carrasco, J., and Minnis, P.: CIMAR-5: A snapshot of the lower troposphere over the subtropical southeast Pacific, B. Am. Meteorol. Soc., 82, 2193–2207, 2001. GFDL-GAMDT: The new GFDL global atmosphere and land model AM2-LM2, J. Climate, 17, 4641–4673, 2004. Ghate, V., Albrecht, B., Fairall, C., and Weller, R.: Climatology of surface meterology, surface fluxes, cloud fraction, and radiative forcing over the south-east Pacific from buoy observations, J. Climate, 22, 5527–5540, 2009. Hahn, C. and Warren, S.: Extended edited synoptic cloud reports from ships and land stations over the globe, 1952–1996, Tech. rep., Carbon Dioxide Informational Analysis Center, Oak Ridge National Laboratory, 1999. Hannay, C., Williamson, D., Hack, J., Kiehl, J., Olson, J., Klein, S., Bretherton, C., and Köhler, M.: Evaluation of forecasted southeast pacific stratocumulus in the NCAR, GFDL, and ECMWF Models, J. Climate, 22, 2871–2889, 2009. Hodur, R.: The Naval Research Laboratory's coupled ocean/atmosphere mesoscale prediction system (COAMPS), Mon. Weather Rev., 125, 1414–1430, 1997. Holtslag, A. and Boville, B.: Local versus nonlocal boundary-layer diffusion in a global climate model, J. Climate, 6, 1825–1842, 1993. Hong, S. and Pan, H.: Nonlocal boundary layer vertical diffusion in a Medium-Range Forecast Model, Mon. Weather Rev., 124, 2322–2339, 1996. Hong, S., Dudhia, J., and Chen, S.: A revised approach to ice microphysical processes for the bulk parameterization of clouds and precipitation, Mon. Weather Rev., 132, 103–120, 2004. Hong, S., Noh, Y., and Dudhia, J.: A new vertical diffusion package with an explicit treatment of entrainment processes, Mon. Weather Rev., 134, 2318–2341, 2006. Hourdin, F., Musat, I., Bony, S., Braconnot, P., Codron, F., Dufresne, J., Fairhead, L., Filiberti, M., Friedlingstein, P., Grandpeix, J., Krinner, G., Levan, P., Li, Z., and Lott, F.: The LMDZ4 general circulation model: climate performance and sensitivity to parametrized physics with emphasis on tropical convection, Clim. Dynam., 27, 787–813, 2006. Janji\'c, Z.: Nonsingular implementation of the Mellor-Yamada level 2.5 scheme in the NCEP Meso model., Tech. rep., NCEP, 2002. Kalnay, E., Kanamitsu, M., Kistler, R., Collins, W., Deaven, D., Gandin, L., Iredell, M., Saha, S., White, G., Woollen, J., Zhu, Y., Chelliah, M., Ebisuzaki, W., Higgins, W., Janowiak, J., Mo, K., Ropelewski, C., Wang, J., Leetmaa, A., Reynolds, R., Jenne, R., and Joseph, D.: The NCEP/NCAR 40-year reanalysis project, B. Am. Meteorol. Soc., 77, 437–471, 1996. Kanamaru, H. and Kanamitsu, M.: Scale-selective bias correction in a downscaling of global analysis using a regional model, Mon. Weather Rev., 135, 334–350, 2007. Klein, S. and Hartmann, D.: The seasonal cycle of low stratiform clouds, J. Climate, 6, 1587–1606, 1993. Klein, S., Jiang, X., Boyle, J., Malyshev, S., and Xie, S.: Diagnosis of the summertime warm and dry bias over the U.S. Southern Great Plains in the GFDL climate model using a weather forecasting approach, Geophys. Res. Lett., 33, L18805, doi:10.1029/2006GL027567, 2006. Köhler, M.: Improved prediction of boundary layer clouds, ECMWF Newsletter, 104, 18–22, 2005. Lamarque, J., Kiehl, J., Brasseur, G., Butler, T., Cameron-Smith, P., Collins, W., Collins, W., Granier, C., Hauglustaine, D., Hess, P., Holland, E., Horowitz, L., Lawrence, M., McKenna, D., Merilees, P., Prather, M., Rasch, P., Rotman, D., Shindell, D., and Thornton, P.: Assessing future nitrogen deposition and carbon cycle feedback using a multimodel approach: Analysis of nitrogen deposition, J. Geophys. Res., 110, D19303, doi:10.1029/2005JD005825, 2005. Lin, Y., Farley, R., and Orville, H.: Bulk parameterization of the snow field in a cloud model, J. Clim. Appl. Meteorol., 22, 1065–1092, 1983. Liu, X., Penner, J., and Herzog, M.: Global modeling of aerosol dynamics: Model description, evaluation, and interactions between sulfate and nonsulfate aerosols, J. Geophys. Res., 110, D18206, doi:10.1029/2004JD005674, 2005. Lock, A., Brown, A., Bush, M., Martin, G., and Smith, R.: A new boundary layer mixing scheme. Part I: Scheme description and single-column model tests, Mon. Weather Rev., 128, 3187–3199, 2000. Ma, C., Mechoso, C., Robertson, A., and Arakawa, A.: Peruvian stratus clouds and the tropical Pacific circulation: A coupled ocean-atmosphere GCM study, J. Climate, 9, 1635–1645, 1996. Martin, G., Bush, M., Brown, A., Lock, A., and Smith, R.: A new boundary layer mixing scheme. Part II: tests in climate and mesoscale models, Mon. Weather Rev., 128, 3200–3217, 2000. Morrison, H. and Gettelman, A.: A new two-moment bulk stratiform cloud microphysics scheme in the community atmosphere model, version 3 (CAM3). Part I: Description and numerical tests, J. Climate, 21, 3642–3659, 2008. Park, S. and Bretherton, C.: The University of Washington shallow convection and moist turbulence schemes and their impact on climate simulations with the community atmosphere model, J. Climate, 22, 3449–3469, 2009. Phillips, T., Potter, G., Williamson, D., Cederwall, R., Boyle, J., Fiorino, M., Hnilo, J., Olson, J., Xie, S., and Yio, J.: Evaluating parameterizations in general circulation models – climate simulation meets weather prediction, B. Am. Meteorol. Soc., 85, 1903–1915, 2004. Rasch, P. and Kristjansson, J.: A comparison of the CCM3 model climate using diagnosed and predicted condensate parameterizations, J. Climate, 11, 1587–1614, 1998. Raymond, D., Esbensen, S., Paulson, C., Gregg, M., Bretherton, C., Petersen, W., Cifelli, R., Shay, L., Ohlmann, C., and Zuidema, P.: EPIC2001 and the coupled ocean-atmosphere system of the tropical East Pacific, B. Am. Meteorol. Soc., 85, 1341–1354, 2004. Richter, I. and Mechoso, C.: Orographic influences on the annual cycle of Namibian stratocumulus clouds, Geophys. Res. Lett., 31, L24108, doi:10.1029/2004GL020814, 2004. Richter, I. and Mechoso, C.: Orographic influences on subtropical stratocumulus, J. Atmos. Sci., 63, 2585–2601, 2006. Rotstayn, L.: A physically based scheme for the treatment of stratiform clouds and precipitation in large-scale models. 1. Description and evaluation of the microphysical processes, Q. J. Roy. Meteor. Soc., 123, 1227–1282, 1997. Rutledge, S. and Hobbs, P.: The mesoscale and microscale structure and organization of clouds and precipitation in midlatitude cyclones. XII: A diagnostic modeling study of precipitation development in narrow cold-frontal rainbands, J. Atmos. Sci., 41, 2949–2972, 1984. Skamarock, W., Klemp, J., Dudhia, J., Gill, D., Barker, D., Wang, W., and Powers, J.: A description of the advanced research WRF version 2, Tech. rep., NCAR, 2005. Siebesma, A. P., Jakob, C., Lenderink, G., Neggers, R. A. J., Teixeira, J., Van Meijgaard, E., Calvo, J., Chlond, A., Grenier, H., Jones, C., Kohler, M., Kitagawa, H., Marquet, P., Lock, A. P., Muller, F., Olmeda, D., and Severijns, C.: Cloud representation in general-circulation models over the northern Pacific Ocean: A EUROCS intercomparison study, Q. J. Roy. Meteor. Soc., 130, 3245–3267, 2004. Smith, R.: A scheme for predicting layer clouds and their water-content in a general-circulation model, Q. J. Roy. Meteor. Soc., 116, 435–460, 1990. Sundqvist, H.: Parameterization scheme for non-convective condensation including prediction of cloud water-content, Q. J. Roy. Meteor. Soc., 104, 677–690, 1978. Sundqvist, H., Berge, E., and Kristjansson, J.: Condensation and cloud parameterization studies with a mesoscale numerical weather prediction model, Mon. Weather Rev., 117, 1641–1657, 1989. Tiedtke, M.: Representation of clouds in large-scale models, Mon. Weather Rev., 121, 3040–3061, 1993. Wang, Y.: An explicit simulation of tropical cyclones with a triply nested movable mesh primitive equation model: TCM3. Part I: Model description and control experiment, Mon. Weather Rev., 129, 1370–1394, 2001. Wang, Y., Sen, O., and Wang, B.: A highly resolved regional climate model (IPRC-RegCM) and its simulation of the 1998 severe precipitation event over China. Part I: Model description and verification of simulation, J. Climate, 16, 1721–1738, 2003. Wang, Y., Xie, S., Xu, H., and Wang, B.: Regional model simulations of marine boundary layer clouds over the southeast Pacific off South America. Part I: Control experiment, Mon. Weather Rev., 132, 274–296, 2004. Williamson, D. and Olson, J.: A comparison of forecast errors in CAM2 and CAM3 at the ARM Southern Great Plains site, J. Climate, 20, 4572–4585, 2007. Wolf, J.-O., Maier-Reimer, E., and Legutke, S.: The Hamburg Ocean Primitive Equation Model, Tech. rep., Deutsches Klimarechenzentrum, 1997. Wood, R. and Hartmann, D.: Spatial variability of liquid water path in marine low cloud: The importance of mesoscale cellular convection, J. Climate, 19, 1748–1764, 2006. Wood, R., Bretherton, C., and Hartmann, D.: Diurnal cycle of liquid water path over the subtropical and tropical oceans, Geophys. Res. Lett., 29, 2092, doi:10.1029/2002GL015371, 2002. Wood, R., Köhler, M., Bennartz, R., and O'Dell, C.: The diurnal cycle of surface divergence over the global oceans, Q. J. Roy. Meteor. Soc., 135, 1484–1493, 2009. Wu, D., Hu, Y., McCormick, M., Xu, K., Liu, Z., Smith, B., Omar, A., and Chang, F.: Deriving marine-boundary-layer lapse rate from collocated CALIPSO, MODIS, and AMSR-E data to study global low-cloud height statistics, Geosci. Remote Sens. Lett., 5, 649–652, 2008. Xu, H., Wang, Y., and Xie, S.: Effects of the Andes on eastern Pacific climate: A regional atmospheric model study, J. Climate, 17, 589–602, 2004. Xu, H., Xie, S., and Wang, Y.: Subseasonal variability of the southeast Pacific stratus cloud deck, J. Climate, 18, 131–142, 2005. Zhang, Y., Rossow, W., Lacis, A., Oinas, V., and Mishchenko, M.: Calculation of radiative fluxes from the surface to top of atmosphere based on ISCCP and other global data sets: Refinements of the radiative transfer model and the input data, J. Geophys. Res., 109, D19105, doi:10.1029/2003JD004457, 2004. Zhao, Q. and Carr, F.: A prognostic cloud scheme for operational NWP models, Mon. Weather Rev., 125, 1931–1953, 1997. Zuidema, P., Painemal, D., de~Szoeke, S., and Fairall, C.: Stratocumulus cloud-top height estimates and their climatic implications, J. Climate, 22, 4652–4666, 2009.