Atmospheric Dynamics with Phase Changes and Extreme Rainfall Events

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

Water vapor in the atmosphere plays a critical role in extreme weather events. A pressing challenge for the world scientific community, and the topic of this award, is to better understand the dynamical role of water and its influence on atmospheric energetics. A better understanding would help shape future social and economic policy decisions. In particular, more accurate prediction of extreme rainfall events has the potential to save human lives, as well as to better mitigate hundreds of billions of dollars in disaster losses. In addition to advancing scientific and mathematical understanding, the proposed activities also support the training of junior researchers with interdisciplinary expertise. To position these new researchers for future success, mentoring will be provided by the PIs to develop the knowledge, skills and experience necessary for integrating mathematics with the atmospheric sciences. For example, modern weather prediction relies on incorporation of physical insight and observational data into numerical algorithms to solve the mathematical description of atmospheric dynamics in terms of equations. Furthermore, beyond weather predictions themselves are the users of weather predictions, such as government agencies, the insurance industry and other businesses. To assess the risks associated with weather events and their impacts, technical skills are needed in both mathematics and atmospheric sciences. Phase changes of water are a key part of the hydrological cycle. Of particular importance for weather is the phase change from water vapor to liquid water within clouds, and the subsequent formation of precipitation. The heat released from these phase changes can drive atmospheric circulations, and, conversely, atmospheric circulations shape the formation of cloud patterns and precipitation. This coupling between water and atmospheric fluid dynamics is nonlinear and remains a challenge to understand. The award activities aim to improve our fundamental understanding--both mathematical and physical--of moist atmospheric dynamics with phase changes, with attention to high precipitation events. To meet this aim, a hierarchy of partial differential equations will be studied in order to elucidate foundation aspects of such flows, such as: the influence of waves on large-scale balanced flows; the transfer of energy between kinetic, potential and latent energies; and the propagation of sharp interfaces between unsaturated and saturated flow regions. The methods to be used include asymptotical analysis of wave dynamics in the presence of phase changes, construction of discontinuous analytical solutions, observational data analysis based on energy principles and balance relations, and numerical modeling. Extreme rainfall events in the mid-latitudes are always associated with large poleward fluxes of moisture originating from the tropics, such as the structures called 'atmospheric rivers.' The phenomena of atmospheric rivers and their associated jet streaks are one of the central observations proposed for application studies. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.