Date of Award
Doctor of Philosophy
Geological and Atmospheric Sciences
William J. Gutowski Jr.
Projected increases in temperature and moisture in future climates promote a more favorable environment for very heavy/extreme precipitation events. Although precipitation events at the highest intensities have increased in the last ~50 years and are projected to continue into the future, climate models can have difficulty replicating very heavy events seen in observations, often due to coarse horizontal and vertical resolutions. Global climate models (GCMs) with horizontal resolution spanning usually around 100~300km may be able to replicate winter storms, which have larger spatial characteristics, but often fail to replicate summer events, as Mesoscale Convective Systems (MCSs) dominate the precipitation characteristics in the central U.S. MCSs often occur at a much small spatial scale than winter storms. High resolution (~50km to finer horizontal resolution) regional climate models (RCMs) may provide a better rendition of MCSs. Climate models provide valuable information to the scientific community, as evidenced by an abundance of peer-reviewed literature evaluating extreme events in climate simulations. Continued improvement in the structure of climate models has produced results more consistent with observations.
GCMs from the Coupled Model Intercomparison Project – Phase 5 (CMIP5), and RCMs from the North American Regional Climate Change Assessment Program (NARCCAP) are used in this study. The domain examined is an upper Mississippi region. In Chapter 2, CMIP5 models are compared with observations during the winter (December-February) months. The analysis reveals that CMIP5 models agree fairly well observations, though coarser resolution GCMs produce a smoother spatial distribution of heavy precipitation. In the remaining studies, NARCCAP RCMs are examined along with observations during the summer months (June – August). Chapter 3 examines the contemporary climate. Results show that while most models produce credible simulations of widespread very heavy events with respect to observations, biases are present for particular simulations, and is highlighted in this study. In Chapter 4, climate change of summertime widespread very heavy precipitation events is examined. Most models project a decrease in average precipitation but an increase in intensity and frequency of very heavy precipitation. Areas of projected precipitation increase occur in areas where conditions will become more favorable for convective storm development.
Kawazoe, Sho, "Evaluation of regional, very heavy precipitation events in the upper Mississippi region using climate model ensembles" (2016). Graduate Theses and Dissertations. 15734.