Sensitivity of the MM5 mesoscale model to physical parameterizations for regional climate studies: Annual cycle

Copyright 2007 by the American Geophysical Union. This study was financially supported by projects REN2002-04584-C04-01-CLI, REN-2002-04584-C04-04-CLI, CGL2005-06966-C07-04/CLI and CGL2005-06966-C07-05/CLI of the Spanish Ministry of Science and Technology. Jesús Fernández received support from the Department of Education, Universities and Research of the Basque Autonomous Government through grant BFI04.52. J. Sáenz received support by the research groups’ support program, project 9/UPV 00060.310-15343/2003, University of the Basque Country. The gridded precipitation and temperature data were supplied by the Climate Impacts LINK Project (UK Department of the Environment Contract EPG 1/1/16) on behalf of the Climatic Research Unit, University of East Anglia. The boundary conditions were downloaded from the NCEP/NCAR Web server. The National Institutes of Meteorology of Spain and Portugal provided access to daily records of temperature and precipitation at several sites. Other surface and boundary data were provided by the MARS system of the ECMWF. The authors thank the Pennsylvania State University/National Center for Atmospheric Research numerical model home page for making the MM5 model publicly available. Authors made extensive use of the Generic Mapping Tools software [Wessel and Smith, 1991]. GTOPO30 topography data are distributed by the Land Processes Distributed Active Archive Center (LP DAAC), located at the U.S. Geological Survey’s EROS Data Center http://LPDAAC.usgs.gov. We appreciate the comments on the manuscript made by Jimy Dudhia. The comments by three anonymous reviewers have also improved the final version of this manuscript.
We present an analysis of the sensitivity to different physical parameterizations of a high-resolution simulation of the MM5 mesoscale model over the Iberian Peninsula. Several (16) 5-year runs of the MM5 model with varying parameterizations of microphysics, cumulus, planetary boundary layer and longwave radiation have been carried out. The results have been extensively compared with observational precipitation and surface temperature data. The parameterization uncertainty has also been compared with that related to the boundary conditions and the varying observational data sets. The annual cycles of precipitation and surface temperature are well reproduced. The summer season presents the largest deviations, with a 5 K cold bias in the southeast and noticeable precipitation errors over mountain areas. The cold bias seems to be related to the surface, probably because of the excessive moisture availability of the five-layer soil scheme used. No parameterization combination was found to perform best in simulating both precipitation and surface temperature in every season and subregion. The Kain-Fritsch cumulus scheme was found to produce unrealistically high summer precipitation. The longwave radiation parameterizations tested were found to have little impact on our target variables. Other factors, such as the choice of boundary conditions, have an impact on the results as large as the selection of parameterizations. The range of variability in the MM5 physics ensemble is of the same order of magnitude as the observational uncertainty, except in summer, when it is larger and probably related to the inaccuracy of the model to reproduce the summer precipitation over the area.
Mininsterio de Ciencia y Tecnolgía (MCYT), España
Departamento de Educación, Política Lingüística y Cultura (Gobierno Vasco)
Universidad del País Vasco / Euskal Herriko Unibertsitatea (UPV / EHU)
Depto. de Física de la Tierra y Astrofísica
Fac. de Ciencias Físicas
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