P2C2: Tropical Pacific Influences on Atmospheric Blocking across Climates

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Atmospheric blocking events are persistent weather patterns, most often high-pressure systems, that divert the mid-latitude jet stream and storms for days to weeks and can be associated with extreme weather such as heat waves, cold spells, droughts, and flooding. There is significant uncertainty surrounding the response of atmospheric blocking and its related extreme events to anthropogenic climate change, including their frequency, intensity, and duration, as well as their modulation by climate variability. The mean climate state and anomalies of the tropical Pacific during El Niño-Southern Oscillation (ENSO) events influence atmospheric blocking; however, these impacts vary depending on the ENSO “flavor” (Eastern or Central Pacific). Thus, part of the uncertainty in blocking projections is due to uncertainties in the projected changes in both the tropical Pacific mean state and ENSO diversity and their potential interactions. This project aims to investigate the relationship between ENSO diversity, atmospheric blocking and extreme events in observations and existing and new targeted model experiments. Via a paleoclimate model-proxy synthesis, the project will potentially enable the assessment of biases and the development of constraints for future projections of atmospheric blocking and associated weather extremes as they are influenced by the tropics.The work focuses on a systematic and hierarchical investigation of the relationship between atmospheric blocking and associated weather extremes that will specifically consider the impact of different states of tropical Pacific mean climate and of ENSO diversity. To this end, the researchers will relate atmospheric blocking characteristics and extreme event frequency to the state of the tropical Pacific at multiple time scales (multidecadal, interannual) and, diagnose the underlying mechanisms via a synthesis of diagnostic analysis of GCM present-day and past climate experiments, new high-resolution (~15km) model experiments designed to isolate the role of the tropical Pacific, statistical modeling of weather extremes, and paleoclimate proxy records. This investigation will offer new insights into the impact of the tropics on midlatitude extreme events and allow for a quantitative synthesis of paleoclimate proxies and models to assess model skill in representing these relationships. The ultimate goal is to devise metrics that reduce model uncertainty in simulations of externally-forced changes in blocking, in other words calculate constraints for blocking projections based on simulation skill of tropical Pacific mean state and diversity. The potential broader impacts include a comprehensive framework for integration, validation and interpretation of past climate and modern observations to evaluate future climate projections at regional and global scales. This project has the potential to improve the prediction of extreme weather and assessment of risk associated with the intersection of climate change and variability, atmospheric blocking, and extreme events, and develops knowledge and resources that are increasingly being used by academic institutions, government agencies, and private-sector R&D companies, including insurance companies, banks, and consulting firms.The research will provide scientific training for graduate and undergraduate students on new technologies on weather and climate risk analysis in Title III - Asian American and Native American Pacific Islander-Serving Institutions (AANAPI). Additionally, a new online outreach module will be developed to be incorporated in the biennial SOEST Open House Activities for K-12 visitors and the general public (~10-minute activities), designed to raise awareness and understanding of the distinct impacts of ENSO flavors. This new module will be designed as an ENSO impacts game, where the players will place a Sea Surface Temperature anomaly corresponding to different ENSO flavors, which will change the position of the jet stream on the board. They will then be asked to guess the ENSO impacts in multiple locations, including Hawaii (wet/dry, warm/cold) as they relate to changes in the jet stream, and will be assigned scores based on hits and misses. The module will be shared publicly to be used by educators across the country.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.