CAREER: Understanding Forced and Internal Variability in the Pacific and its Impacts on North America

Changes in long-term weather patterns are being felt by society and ecosystems most directly through increases in frequency and magnitude of damaging extreme events, such as heatwaves, wildfires, flood-inducing precipitation, and droughts. A key source of predictability for such events is the Pacific Ocean, situated upstream of and influencing the weather over North America. The scientific community currently does not have a robust understanding of how ocean temperatures in the Pacific are going to change, with several competing ideas on how to reconcile the discrepancy between numerical model simulations and real-world observations. This project investigates the leading candidate hypotheses for these discrepancies. The project thus provides socio-economic benefits and improved national security by increasing our capacity to anticipate changes in the likelihood of extreme weather events and their impacts. The past decade has revealed a substantial mismatch in the magnitude of trends and variability between models and observations in the Pacific, throwing into question our ability to predict its behavior over the next decades, and with that, its impact on extreme weather events. This project will investigate the role of inadequate spatial resolution of current model simulations and erroneous representation of the relative importance of long-term externally forced changes and internally-generated chaotic weather variations, and their impacts on the divergence between modeled and observed conditions. The overarching hypothesis addressed here is that a larger fraction of decadal-scale variability is externally forced than internally generated and that current numerical models are deficient in their representation of this partitioning. The hypothesis is tested through analysis of existing model simulations and new simulations generated from the variable resolution version of the Community Earth System Model (VR-CESM). 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. NSF Award ID: 2543191 | Program: 01002930DB NSF RESEARCH & RELATED ACTIVIT,01002627DB NSF RESEARCH & RELATED ACTIVIT,01003031DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Flavio Lehner | Institution: Cornell University, ITHACA, NY | Award Amount: $703,912 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2543191 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2543191.html