Articles | Volume 10, issue 10
Atmos. Chem. Phys., 10, 4757–4774, 2010

Special issue: VAMOS Ocean-Cloud-Atmosphere-Land Study (VOCALS) (ACP/OS inter-journal...

Atmos. Chem. Phys., 10, 4757–4774, 2010

  26 May 2010

26 May 2010

The PreVOCA experiment: modeling the lower troposphere in the Southeast Pacific

M. C. Wyant1, R. Wood1, C. S. Bretherton1, C. R. Mechoso2, J. Bacmeister3, M. A. Balmaseda4, B. Barrett5, F. Codron6, P. Earnshaw7, J. Fast8, C. Hannay9, J. W. Kaiser4, H. Kitagawa10, S. A. Klein11, M. Köhler4, J. Manganello12, H.-L. Pan13, F. Sun2, S. Wang14, and Y. Wang15 M. C. Wyant et al.
  • 1Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA
  • 2Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, Los Angeles, CA, USA
  • 3Global Modeling and Assimiliation Office, NASA Goddard Space Flight Center, Greenbelt, MD, USA
  • 4Research Department, European Center for Medium-Range Weather Forecasts, Reading, UK
  • 5Department of Geophysics, University of Chile, Santiago, Chile
  • 6Université Pierre et Marie Curie, Laboratoire de Meteorologie Dynamique, Paris, France
  • 7Met Office, Exeter, Devon, UK
  • 8Atmospheric Sciences and Global Change, Pacific Northwest National Laboratory, Richland, WA, USA
  • 9Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, CO, USA
  • 10Meteorological College, Japan Meteorological Agency, Tokyo, Japan
  • 11Program for Climate Model Diagnosis and Intercomparison, Lawrence Livermore National Laboratory, Livermore, CA, USA
  • 12Center for Ocean-Land-Atmosphere Studies, Calverton, MD, USA
  • 13Environmental Modeling Center, National Centers for Environmental Prediction, Camp Springs, Maryland, USA
  • 14Marine Meteorology Division, Naval Research Laboratory, Monterey, CA, USA
  • 15International Pacific Research Center, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, HI, USA

Abstract. 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.

Final-revised paper