How Will Global Warming Change the Storm Tracks? Investigating the Importance of Diabatic Processes using High-resolution Simulations

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It is expected that the tracks and intensities of extratropical cyclones will change over coming decades as climate warms, though the magnitudes and even the signs of these changes remain uncertain. The potentially competing effects of weaker lower-tropospheric temperature contrasts and enhanced specific humidity, further complicated by the uncertain influences of an expected deepening of the troposphere, stronger baroclinicity in the upper troposphere, and an altered global circulation, lead to great uncertainty in projecting changes in extratropical cyclones and stormtracks and, in turn, in projecting how their roles in Earth's climate system will change.Studies of the dynamics of individual storms reveal that the release of latent heat, through the diabatic production of low-level potential vorticity, is critical for storm development and for producing damaging winds and flooding rains. These dynamics should be more vigorous in a warmer and moister atmosphere, but the scales of the relevant features fall below the resolved spatial scales of global climate models. This project will test the hypothesis that individual storms and the stormtracks, including their climatically important poleward transports of heat and moisture, are sensitive to model resolution, and that this sensitivity is greater in a warmer climate. A program of high-resolution model simulations of the North Atlantic stormtrack under current day and climate-change conditions will be carried out to test this hypothesis using the Weather Research and Forecasting (WRF) model, in regional and global configurations. The intellectual merit of this project is in systematically exploring the two-way interactions between diabatic effects in storms and the global climate system. Changes in extratropical storms and stormtracks have potentially important impacts on society, through their effects on the availability of water and on the risks of damaging winds, flooding rains, and high waves. More reliable projections of these changes and improved understanding of their associated uncertainties are a potential societal benefit from this research and a broader impact of this project. Additional broader impacts include the mentoring of graduate and undergraduate researchers, education and outreach based on project results, and the value, to the broader climate research community, of using the WRF model in climate applications.