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

预计随着气候变暖，温带气旋的路径和强度将在未来几十年发生变化，尽管这些变化的幅度甚至迹象仍不确定。对流层下层温度对比减弱和比湿度增强的潜在竞争效应，再加上对流层预计加深、对流层上层斜压性增强和全球环流改变的不确定影响，使预测温带气旋和风暴路径的变化，进而预测它们在地球气候系统中的作用将如何变化，都具有很大的不确定性。对单个风暴动力学的研究表明，潜热的释放，通过低位势涡的非绝热产生，是风暴发展和产生破坏性风和洪水的关键。在一个更温暖、更湿润的大气中，这些动态应该更加强烈，但相关特征的尺度低于全球气候模式的分辨率空间尺度。这个项目将检验这样一个假设，即单个风暴和风暴路径，包括它们在气候上重要的热量和水分向极地的输送，对模型分辨率很敏感，而且在气候变暖的情况下，这种敏感性更大。在当前和气候变化条件下，北大西洋风暴路径的高分辨率模式模拟程序将在区域和全球配置中使用天气研究与预报（WRF）模式来验证这一假设。这个项目的智力价值在于系统地探索了风暴的绝热效应与全球气候系统之间的双向相互作用。温带风暴和风暴路径的变化通过对水的可用性以及破坏性风、洪水和大浪的风险的影响，对社会产生潜在的重要影响。对这些变化进行更可靠的预测，并提高对其相关不确定性的理解，是本研究的潜在社会效益，也是本项目的更广泛影响。其他更广泛的影响包括对研究生和本科生研究人员的指导，基于项目结果的教育和推广，以及在气候应用中使用WRF模式对更广泛的气候研究界的价值。

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.