IOWA STATE UNIVERSITY OF SCIENCE AND TECHNOLOGY

Intellectual Merit Accurate simulation of the initiation and morphological evolution of mesoscale convective systems (MCSs) is important for both rainfall and severe weather forecasting. Near cloud-permitting grid spacing (NCPGS) is used increasingly often, even in quasi-operational settings; however, convective initiation in these simulations may be improperly depicted due to relatively coarse grid spacings relative to cloud elements, along with deficiencies in initialization data. Morphological evolution also may be inaccurately portrayed for similar reasons, and may be influenced even more strongly by deficiencies in microphysical schemes which affect the simulated cold pools. The PIs’ prior research in this NSF program for over a decade has examined methods to improve Quantitative Precipitation Forecasting (QPF) for warm season convection. The present renewal proposal is an extension of our prior research, making use of NCPGS in the Weather Research and Forecasting (WRF) model to improve understanding of convective initiation and morphological evolution of Midwestern MCSs, and to explore techniques leading to improved QPF. The proposed work will make use of an extensive archive ofMCS events and simulations gathered through our prior research projects, which span both the IHOP and BAMEX field observation periods, and recent NOAA Hazardous Weather Testbed projects. The research will address three primary goals. First, detailed analysis of simulations and observations of convective initiation and morphological evolution will be performed to further understanding about the processes playing important roles. Second, tests will be performed to examine sensitivity of the simulations to both microphysical parameterizations/processes and new scale-appropriate methods of applying convective parameterizations. Finally, we will explore several methods for improving QPF guidance, making use of new entity-based verification techniques and ensembles. Application of the factor separation approach will assist with interpretation of results, both for ensemble and sensitivity studies and in quantifying spatial versus temporal errors in rainfall fields. Broader Impacts This research effort has several broader impacts. First, it addresses one of the most challenging short-range forecasting problems today, accurate prediction of warm season convective systems and their rainfall, and should help forecasters improve public safety with respect to flooding and severe weather. Improved understanding of the development and evolution of Midwestern convective systems also has economic benefits in this agricultural region. Second, the use of theWRF model as the primary tool for the proposed research will facilitate broader impacts on the research community, since the WRF model is the primary vehicle used for both research and short-range operational forecasting in the United States. The study will support several graduate students, and its research themes will be used as well by undergraduate meteorology majors at Iowa State for required original research projects. Research results will be incorporated into two mesoscale meteorology courses taught by one of the PIs. Publication of research results in atmospheric science journals and presentation at conferences and workshops, along with talks at National Weather Service offices and media interviews will permit research findings to directly benefit operational forecasters and through them, the general public.

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