On the Impact of WRF Model Vertical Grid Resolution on Midwest Summer Rainfall Forecasts

Eric A. Aligo Department of Geological and Atmospheric Sciences, Iowa State University, Ames, Iowa

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William A. Gallus Jr. Department of Geological and Atmospheric Sciences, Iowa State University, Ames, Iowa

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Moti Segal Department of Agronomy, Iowa State University, Ames, Iowa

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Abstract

Weather Research and Forecast (WRF) model exploratory sensitivity simulations were performed to determine the impact of vertical grid resolution (VGR) on the forecast skill of Midwest summer rainfall. Varying the VGR indicated that a refined VGR, while adopting the widely used North America Regional Reanalysis (NARR) for initial and lateral boundary conditions, does not necessarily result in a consistent improvement in quantitative precipitation forecasts (QPFs). When averaged over a variety of microphysical schemes in an illustrative case, equitable threat score (ETS) and bias values actually worsened with a greater overpredicted rainfall for half of the rainfall thresholds when the VGR was refined. Averaged over strongly forced cases, ETS values worsened for all rainfall thresholds while biases mostly increased, indicating a further overprediction of rainfall when the number of levels was increased. Skill improved, however, for all rainfall thresholds when the resolution above the melting level was increased. Skill also improved for most rainfall thresholds when the resolution in the surface layer was increased, which is attributed to better-resolved surface turbulent momentum and thermal fluxes. Likewise, a refined VGR resulted in improvements in weakly forced cases, which are governed mostly by thermodynamic forcing and are sensitive to vertical profiles of temperature and moisture. Application of the factor separation method suggested that the refined VGR more frequently had a negative impact on skill through the interaction between lower-atmospheric processes and microphysical processes above the melting level.

Corresponding author address: Eric A. Aligo, Iowa State University, 3010 Agronomy Hall, Ames, IA 50011. Email: ealigo@iastate.edu

Abstract

Weather Research and Forecast (WRF) model exploratory sensitivity simulations were performed to determine the impact of vertical grid resolution (VGR) on the forecast skill of Midwest summer rainfall. Varying the VGR indicated that a refined VGR, while adopting the widely used North America Regional Reanalysis (NARR) for initial and lateral boundary conditions, does not necessarily result in a consistent improvement in quantitative precipitation forecasts (QPFs). When averaged over a variety of microphysical schemes in an illustrative case, equitable threat score (ETS) and bias values actually worsened with a greater overpredicted rainfall for half of the rainfall thresholds when the VGR was refined. Averaged over strongly forced cases, ETS values worsened for all rainfall thresholds while biases mostly increased, indicating a further overprediction of rainfall when the number of levels was increased. Skill improved, however, for all rainfall thresholds when the resolution above the melting level was increased. Skill also improved for most rainfall thresholds when the resolution in the surface layer was increased, which is attributed to better-resolved surface turbulent momentum and thermal fluxes. Likewise, a refined VGR resulted in improvements in weakly forced cases, which are governed mostly by thermodynamic forcing and are sensitive to vertical profiles of temperature and moisture. Application of the factor separation method suggested that the refined VGR more frequently had a negative impact on skill through the interaction between lower-atmospheric processes and microphysical processes above the melting level.

Corresponding author address: Eric A. Aligo, Iowa State University, 3010 Agronomy Hall, Ames, IA 50011. Email: ealigo@iastate.edu

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  • Aligo, E. A., Gallus W. A. Jr., and Segal M. , 2007: Summer rainfall forecast spread in an ensemble initialized with different soil moisture analyses. Wea. Forecasting, 22 , 299314.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Baldwin, M. E., and Mitchell K. E. , 1997: The NCEP hourly multi-sensor U.S. precipitation analysis for operations and GCIP research. Preprints, 13th Conf. on Hydrology, Long Beach, CA, Amer. Meteor. Soc., 54–55.

  • Betts, A. K., 1986: A new convective adjustment scheme. Part I: Observational and theoretical basis. Quart. J. Roy. Meteor. Soc., 112 , 677692.

    • Search Google Scholar
    • Export Citation
  • Betts, A. K., and Miller M. J. , 1986: A new convective adjustment scheme. Part II: Single column tests using GATE wave, BOMEX, ATEX and arctic air-mass data sets. Quart. J. Roy. Meteor. Soc., 112 , 693709.

    • Search Google Scholar
    • Export Citation
  • Bryan, G. H., Wyngaard J. C. , and Fritsch J. M. , 2003: Resolution requirements for the simulation of deep moist convection. Mon. Wea. Rev., 131 , 23942416.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Colle, B. A., and Yuter S. E. , 2007: The impact of coastal boundaries and small hills on the precipitation distribution across southern Connecticut and Long Island, New York. Mon. Wea. Rev., 135 , 933954.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Davis, C., and Coauthors, 2004: The Bow Echo and MCV Experiment: Observations and opportunities. Bull. Amer. Meteor. Soc., 85 , 10751093.

  • Ebert, E. E., 2001: Ability of a poor man’s ensemble to predict the probability and distribution of precipitation. Mon. Wea. Rev., 129 , 24612480.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Ek, M. B., Mitchell K. E. , Lin Y. , Rogers E. , Grunmann P. , Koren V. , Gayno G. , and Tarplay J. D. , 2003: Implementation of Noah land surface model advances in the National Centers for Environmental Prediction operational mesoscale Eta model. J. Geophys. Res., 108 , 8851. doi:10.1029/2002JD003296.

    • Search Google Scholar
    • Export Citation
  • Gallus W. A. Jr., , and Segal M. , 2001: Impact of improved initialization of mesoscale features on convective system rainfall in 10-km Eta simulations. Wea. Forecasting, 16 , 680696.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gallus W. A. Jr., , Correia J. Jr., and Jankov I. , 2005: The 4 June 1999 derecho event: A particularly difficult challenge for numerical weather prediction. Wea. Forecasting, 20 , 705728.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gilmore, M. S., Straka J. M. , and Rasmussen E. N. Precipitation and evolution sensitivity in simulated deep convective storms: Comparisons between liquid-only and simple ice and liquid phase microphysics. Mon. Wea. Rev., 132 , 18971916.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Grams, J. S., Gallus W. A. Jr., Koch S. E. , Wharton L. S. , Loughe A. , and Ebert E. E. , 2006: The use of a modified Ebert–McBride technique to evaluate mesoscale model QPF as a function of convective system morphology during IHOP 2002. Wea. Forecasting, 21 , 288306.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hong, S-H., and Lim J-O. , 2006: The WRF single-moment 6-class microphysics scheme (WSM6). J. Kor. Meteor. Soc., 42 , 129151.

  • Hong, S-H., Dudhia J. , and Chen S-H. , 2004: A revised approach to ice microphysical processes for the bulk parameterization of clouds and precipitation. Mon. Wea. Rev., 132 , 103120.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Janjić, Z. I., 1994: The step-mountain Eta coordinate model: Further developments of the convection closure schemes. Mon. Wea. Rev., 122 , 927945.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Janjić, Z. I., 2002: Nonsingular implantation of the Mellor–Yamada level 2.5 scheme in the NCEP mesomodel. NOAA/NWS/NCEP Office Note 437, 61 pp.

    • Search Google Scholar
    • Export Citation
  • Jankov, I., and Gallus W. A. Jr., 2004: MCS rainfall forecast accuracy as a function of large-scale forcing. Wea. Forecasting, 19 , 428439.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jankov, I., Gallus W. A. Jr., Segal M. , Shaw B. , and Koch S. E. , 2005: The impact of different WRF model physical parameterizations and their interactions on warm season MCS rainfall. Wea. Forecasting, 20 , 10481060.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jankov, I., Gallus W. A. Jr., Segal M. , and Koch S. E. , 2007: Influence of initial conditions on the WRF-ARW model QPF response to physical parameterization changes. Wea. Forecasting, 22 , 501519.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jewett, B. F., and Wilhelmson R. B. , 2006: The role of forcing in cell morphology and evolution within midlatitude squall lines. Mon. Wea. Rev., 134 , 37143734.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kain, J. S., and Fritsch J. M. , 1993: The role of the convective “trigger function” in numerical forecasts of mesoscale convective systems. Meteor. Atmos. Phys., 49 , 93106.

    • Search Google Scholar
    • Export Citation
  • Kallos, G., and Segal M. , 1991: On the meteorological conditions during postprecipitation periods: Implications to pollutant dispersion. J. Appl. Meteor., 30 , 297311.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kimball, S. K., and Dougherty F. C. , 2006: The sensitivity of idealized hurricane structure and development to the distribution of vertical levels in MM5. Mon. Wea. Rev., 134 , 19872008.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lin, Y-L., Farley R. D. , and Orville H. D. , 1983: Bulk parameterization of the snow field in a cloud model. J. Appl. Meteor., 22 , 10651092.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lindzen, R. S., and Fox-Rabinovitz M. , 1989: Consistent vertical and horizontal resolution. Mon. Wea. Rev., 117 , 25752583.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Markowski, P. M., Rasmussen E. N. , Straka J. M. , and Dowell D. C. , 1998: Observations of low-level baroclinicity generated by anvil shadows. Mon. Wea. Rev., 126 , 29422958.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Mass, C. F., Ovens D. , Westrick K. , and Colle B. A. , 2002: Does increasing horizontal resolution produce better forecasts? The results of two years of real-time numerical weather prediction over the Pacific Northwest. Bull. Amer. Meteor. Soc., 83 , 407430.

    • Search Google Scholar
    • Export Citation
  • Ookouchi, Y., Segal M. , Kessler R. C. , and Pielke R. A. , 1984: Evaluation of soil moisture effects on the generation and modification of mesoscale circulations. Mon. Wea. Rev., 112 , 22812292.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Panofsky, H. A., and Dutton J. A. , 1984: Atmospheric Turbulence: Models and Methods for Engineering Applications. John Wiley and Sons, 397 pp.

    • Search Google Scholar
    • Export Citation
  • Pecnick, M. J., and Keyser D. , 1989: The effect of spatial resolution on the simulation of upper-tropospheric frontogenesis using a sigma-coordinate primitive equation model. Meteor. Atmos. Phys., 40 , 137149.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Roebber, P. J., and Eise J. , 2001: The 21 June 1997 flood: Storm-scale simulations and implications for operational forecasting. Wea. Forecasting, 16 , 197218.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Roebber, P. J., Schultz D. M. , Colle B. A. , and Stensrud D. J. , 2004: The risks and rewards of high-resolution and ensemble numerical weather prediction. Wea. Forecasting, 19 , 936949.

    • Search Google Scholar
    • Export Citation
  • Rogers, E., Black T. , Ferrier B. , Lin Y. , Parrish D. , and DiMego G. , 2001: Changes to the NCEP Meso Eta analysis and forecast system: Increase in resolution, new cloud microphysics, modified precipitation assimilation, modified 3DVAR analysis. NWS Technical Procedures Bulletin 488, 21 pp. [Available online at http://www.emc.ncep.noaa.gov/mmb/mmbpll/eta12tpb/.].

    • Search Google Scholar
    • Export Citation
  • Rosenberg, N. J., Blad B. L. , and Verma S. B. , 1983: Microclimate. John Wiley and Sons, 495 pp.

  • Schaefer, J. T., 1990: The critical success index as an indicator of warning skill. Wea. Forecasting, 5 , 570575.

  • Segal, M., Purdom J. F. W. , Song J. L. , Pielke R. A. , and Mahrer Y. , 1986: Evaluation of cloud shading effects on the generation and modification of mesoscale circulations. Mon. Wea. Rev., 114 , 12011212.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Shaw, B. L., 2004: An objective inter-comparison of WRF, MM5, and NCEP ETA shortrange quantitative precipitation forecasts for the International H2O Project (IHOP) domain. Extended Abstracts, Fifth WRF/14th MM5 Users’ Workshop, Boulder, CO, National Center for Atmospheric Research, 3.6. [Available online at http://www.mmm.ucar.edu/mm5/workshop/workshop-papers_ws04.html.].

    • Search Google Scholar
    • Export Citation
  • Skamarock, W. C., Klemp J. B. , Dudhia J. , Gill D. O. , Barker D. M. , Wang W. , and Powers J. G. , 2005: A description of the Advanced Research WRF version 2. NCAR Tech. Note NCAR/TN-468+STR, 88 pp. [Available online at http://www.wrf-model.org/wrfadmin/docs/arw_v2.pdf].

    • Search Google Scholar
    • Export Citation
  • Stein, U., and Alpert P. , 1993: Factor separation in numerical simulations. J. Atmos. Sci., 50 , 21072115.

  • Thompson, G., Field P. R. , Hall W. D. , and Rasmussen R. M. , 2006: A new bulk microphysical parameterization for WRF (&MM5). Preprints, Seventh WRF Users’ Workshop, Boulder, CO, National Center for Atmospheric Research, 1.11.

  • Tribbia, J. J., and Baumhefner D. P. , 1988: The reliability of improvements in deterministic short-range forecasts in the presence of initial state and modeling deficiencies. Mon. Wea. Rev., 116 , 22762288.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Warner, T. T., and Hsu H-M. , 2000: Nested-model simulation of moist convection: The impact of coarse-grid parameterized convection on fine-grid resolved convection. Mon. Wea. Rev., 128 , 22112231.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wei, H., Segal M. , Gutowksi W. J. Jr., Pan Z. , Arritt R. W. , and Gallus W. A. Jr., 2001: Sensitivity of simulated regional surface thermal fluxes during warm advection snowmelt to selection of the lowest model level height. J. Hydrometeor., 2 , 395405.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Weisman, M. L., Skamarock W. C. , and Klemp J. B. , 1997: The resolution dependence of explicitly modeled convective systems. Mon. Wea. Rev., 125 , 527548.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Weisman, M. L., Davis C. , and Done J. , 2004: The promise and challenge of explicit convective forecasting with the WRF model. Preprints, 22nd Conf. on Severe Local Storms, Hyannis, MA, Amer. Meteor. Soc., 17.2. [Available online at http://ams.confex.com/ams/pdfpapers/81383.pdf.].

  • Zhang, D-L., and Wang X. , 2003: Dependence of hurricane intensity and structure on vertical resolution and time-step size. Adv. Atmos. Sci., 20 , 711725.

    • Crossref
    • Search Google Scholar
    • Export Citation
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