CAREER: Contextualizing Changes in Extreme Precipitation

Extreme precipitation events impact infrastructure, including dams, culverts, nuclear power plants, and highways, that must be built and maintained to withstand these events over their lifetime. This project will address three fundamental questions aimed at advancing understanding of extreme precipitation: 1) how does the precipitation distribution depend on spatial and temporal scales? 2) what are the comparative roles of aerosol and greenhouse gas forcing in determining the precipitation distribution? and 3) how do stratospheric aerosol injections impact extreme precipitation changes?

These questions are specifically motivated by the need to better understand the value of high-resolution modeling for understanding precipitation extremes, to understand if aerosol forcing can explain the discrepancy between observed and modeled changes to extreme precipitation events over the past few decades, and to understand why extreme precipitation decreases despite holding temperatures fixed in model projections of stratospheric aerosol injection. The scientific goals of this project are in line with the principal investigator’s goal to build a career around understanding precipitation extremes as they unfold over the next decades.

An educational component is also integrated into this project providing research experiences for undergraduates related to the science objectives; training students on the use of data for real world problems co-identified in workshops with highway engineers; and integrating the science results into graduate and undergraduate level courses.

The principal investigator has previously developed a novel approach to the analysis of the precipitation distribution by defining shift and intensity modes of the distribution. The shift mode is defined as a uniform shift in the amount distribution to higher or lower intensity by a set amount, while the intensity mode is defined as an increase in the amount distribution by the same factor across intensity bins.

In the context of these two modes of the precipitation distribution, this project will test the hypotheses that 1) increasing the resolution of the precipitation dataset shifts the precipitation distribution to higher intensities without changing its shape; 2) aerosol forcing over the past several decades has had a larger impact on the intensity mode of the precipitation distribution relative to the shift mode, and that this impact differs from that of greenhouse gases; and 3) stratospheric aerosol injection masks the temperature effects on the precipitation distribution, leaving only the direct response to determine the distribution change, which differs from that of the temperature response in terms of its impact on the shift and increase modes. Results of this work will be used to produce information co-designed during workshops with Northeast US highway engineers, with an integrated educational component to allow students to gain experience in addressing stakeholder needs related to precipitation extremes.

In addition to supporting the principal investigator, the project requests funds for a postdoctoral researcher, two graduate students, and one undergraduate student researcher each summer.

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.