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Preliminary study: testing the sensitivity of the model to simulate this CI case.

Numerical investigation of the multi-scale processes inducing convection initiation for the 12 June 2002 IHOP case study. Sophie Bastin, Tammy Weckwerth, Fei Chen, Kevin Manning. Preliminary study: testing the sensitivity of the model to simulate this CI case. NCAR.

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Preliminary study: testing the sensitivity of the model to simulate this CI case.

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  1. Numerical investigation of the multi-scale processes inducing convection initiation for the 12 June 2002 IHOP case study Sophie Bastin, Tammy Weckwerth, Fei Chen, Kevin Manning Preliminary study: testing the sensitivity of the model to simulate this CI case. NCAR Acknowledgements: M. Weisman, S. Trier, M. Pagowsky, D. Posselt, D. Birkenheuer, and others (mesouser, …)

  2. Why did CI occur here? Motivations • Better understanding of the influence of the processes at different scales on the location and timing of convection

  3. Numerical simulations • Control simulation • MM5 model version 3.7 • 1 domain, 4-km horizontal resolution • 44 vertical levels, about 20 half-sigma levels within the boundary layer • Initialization at 12Z on June 12 (cold start), from NCEP Eta analyses (40 km resolution) • Objective analysis and observations nudging (it’s not a forecast) • Eta PBL parameterization, no cumulus scheme, Reisner2 microphysics scheme, Noah LSM • Sensitivity tests: • Domain(s) size • Initialization: time, 3D fields (NCEP ETA, RUC, LAPS, ECMWF), soil moisture and temperature fields (HRLDAS) • Parameterizations: PBL processes, microphysics scheme, cumulus scheme

  4. Control simulation (1) Surface wind at 21 UTC (= initial time + 9h) simulation OK mesonet data

  5. Control simulation (2) Surface temperature at 21 UTC OK mesonet data simulation

  6. Control simulation (3) Relative humidity at 21 UTC OK mesonet data simulation

  7. CONTROL simulation (4) Column-integrated cloud water 20 UTC 19 UTC 21 UTC 22 UTC

  8. Sensitivity study (1)

  9. Sensitivity study (2)

  10. Sensitivity to domains Control simulation 2 domains Surface mixing ratio and wind at 21 UTC Column-integrated cloud water at 21 UTC

  11. Sensitivity study (2)

  12. Sensitivity to initial time Reflectivity, potential temperature and surface wind at 16 UTC Control simulation Initialization at 00 UTC

  13. Conclusion and future prospects • Main results: • Current parameterizations do not guarantee high degree of accuracy in reproducing an outflow boundary. • The number of factors involved in good simulations makes the success of high resolution simulations of thunderstorms a matter of …luck. • Future works • Sensitivity to 3D fields initialization • Simulation of gravity waves (GV) and horizontal convective rolls (HCR) • sensitivity to the horizontal resolution (trying 2km) • WRF model • Analysis of the pre-storm environment in the different simulations to understand the physical processes affecting convection initiation (absence of GV and HCR = reasons of failure?)

  14. Sensitivity study (2)

  15. Sensitivity to PBL parameterization MRF PBL deeper, surface humidity weaker, moisture gradient at the dryline weaker ETA Humidity more concentrated in the PBL and moisture gradient stronger, propitious to the development of convection CI slightly delayed with the MRF parameterization Control simulation MRF param.

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