Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 13 11 2009 10.5194/hess-13-2233-2009 http://www.hydrol-earth-syst-sci.net/13/2233/2009/ http://www.hydrol-earth-syst-sci.net/13/2233/2009/hess-13-2233-2009.html http://www.hydrol-earth-syst-sci.net/13/2233/2009/hess-13-2233-2009.pdf 2233 2240 2009-11-25 Extracting statistical parameters of extreme precipitation from a NWP model J. Eliasson jonase@hi.is O. Rögnvaldsson T. Jonsson University of Iceland, Institute of Environmental and Civil Engineering, Iceland Institute for Meteorological Research, Reykjavik, Iceland Icelandic Meteorological Office, Iceland Precipitation simulations on an 8×8 km grid using the PSU/NCAR Mesoscale Model MM5 are used to estimate the M5 and C_i statistical parameters in order to support the M5 map used for flood estimates by Icelandic engineers. It is known a priori that especially wind anomalies occur on a considerably smaller scale than 8 km. The simulation period used is 1962–2005 and 73 meteorological stations have records long enough in this period to provide a validation data set. Of these only one station is in the central highlands, so the highland values of the existing M5 map are estimates. A comparison between the simulated values and values based on station observations set shows an M5 average difference (observed-simulated) of −5 mm/24 h with a standard deviation of 17 mm, 3 outliers excluded. This is within expected limits, computational and observational errors considered. A suggested correction procedure brings these values down to 4 mm and 11 mm, respectively. Anders, A. M., Roe, G. H., Durran, D. R., and Minder, J. R.: Small-scale spatial gradients in climatological precipitation on the Olympic peninsula, J. Hydrometeorol., 8(5), 1068–1081, 2007. Chien, F. C. and Jou, B. J. D.: MM5 ensemble mean precipitation forecasts in the Taiwan area for three early summer convective (mei-yu) seasons, Weather and Forecasting, 19(4), 735–750, 2004. Chrochet, P.: A study of regional precipitation trends in Iceland using a high-quality gauge network and ERA-40, J. Climate, 20(18), 4659–4677, 2007. Eliasson, J.: Statistical Estimates of PMP Values, Nordic Hydrology, 25(4), 301–312, 1994. Eliasson, J.: A statistical model for extreme precipitation, Water Resour. Res., 33(3), 449–455, 1997. Eliasson, J.: Design values for precipitation and floods from M5 values, Nordic Hydrology, 31(4–5), 357–372, 2000. Grell, G. A., Dudhia, J., and Stauffer, D. R.: A Description of the Fifth-Generation Penn State/NCAR Mesoscale Model (MM5), NCAR/TN-398+STR. National Center for Atmospheric Research, Boulder, CO, 107 pp., 1995. Førland, E. P., Allerup, P., Dahlström, B., Eloma, E., Jónsson, T., Madsen, H., Perälä, J., Rissanen, P., Vedin, H., and Vejen, F.: Manual for operational correction of Nordic precipitation data, Klima Report 24/96, The Norwegian Meteorological Institute, Norway, 1996. Hanna, E. Cappelen, J., Allan, R., et al.: New Insights into North European and North Atlantic Surface Pressure Variability, Storminess, and Related Climatic Change since 1830, J. Climate, 21(24), 6739–6766, 2008. Hanna, E., Jonsson, T. and Box, J. E.: An analysis of Icelandic climate since the nineteenth century, Int. J. Climatol., 24(10), 1193–1210, 2004. Haraldsdóttir, S. H., Ólafsson, H., Durand, Y., Mérindol, L., Giraud, G.: SAFRAN-Crocus snow simulations in an unstable and windy climate, Ann. Glaciol., 32, 339–344, 2001. Minder, J. R., Durran, D. R., Roe, G. H., and Anders, A. M.: The climatology of small-scale orographic precipitation over the Olympic Mountains: Patterns and processes, Q. J. Roy. Meteorol. Soc., 134(633), 817–839, 2008. Reisner, J., Rassmussen, R. J., Bruintjes, R. T.: Explicit forecasting of supercooled liquid water in winter storms using the MM5 mesoscale model, Q. J. Roy. Meteorol. Soc., 124B, 1071–1107, 1998. Rognvaldsson, O., Bao, J.-W., and Olafsson, H.: Sensitivity simulations of orographic precipitation with MM5 and comparison with observations in Iceland during the Reykjanes Experiment, Meteorologische Zeitschrift, 16(1), 87–98, 2007a. Rognvaldsson, O., Jonsdottir, J. F., and Olafsson, H.: Numerical simulations of precipitation in the complex terrain of Iceland – Comparison with glaciological and hydrological data, Meteorologische Zeitschrift, 16(1), 71–85, 2007b. Rognvaldsson, O., Jonsdóttir, J. F., and Olafsson, H.: Dynamical downscaling of precipitation in Iceland 1961–2006, Hydrol. Res., in revision, 2009. Serafin, S. and Ferretti, R.: Sensitivity of a mesoscale model to microphysical parameterizations in the MAP SOP events IOP2b and IOP8, J. Appl. Meteorol. Climatol., 46(9), 1438–1454, 2007. Zangl, G., Aulehner, D., Wastl, C., and Pfeiffer, A.: Small-scale precipitation variability in the Alps: Climatology in comparison with semi-idealized numerical simulations, Q. J. Roy. Meteorol. Soc., 134(636), 1865–1880, 2008.