Collaborative Research: Investigating the Zonal Mean Atmospheric Circulation Changes under Global Warming and the Linkage to the Hydrological Response and Extremes

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Under the climate forcing of the unabated growth of the concentration of greenhouse gases (GHGs), the global atmospheric circulation and hydrological cycle are bound to change. Despite the pivotal role of the atmospheric circulation in climate change and climate feedback, our understanding in its natural variability, its response to global warming forcing, and the associated impacts on the temporal and spatial distributions of the precipitation remains limited, due in part to the diversity of the background wind configurations throughout the annual cycle.This project aims to develop a comprehensive understanding of the sensitivities and mechanisms of the atmospheric circulation response to GHG warming forcing throughout the annual cycle, and to link the circulation changes to the changes in the mean and extremes of precipitation. The investigators will combine purposefully designed sensitivity experiments using a hierarchy of atmospheric models with analyzing the Intergovernmental Panel on Climate Change (IPCC) Coupled Model Intercomparison Project Phase 5 (CMIP5) model simulations, a new set of ultra-high resolution climate simulations and the existent observations and reanalysis. They will revolve around three inter-related scientific themes: (1) sensitivities and mechanisms of the mean circulation responses to global warming forcing under different circulation regimes (corresponding to different seasons and different sectors of the globe); (2) the leading mode of variability under different circulation regimes and the linkage between the unforced intrinsic mode of variability to the mean response to global warming forcing; (3) connection between the leading mode of variability, as occurs naturally or as a result of climate change forcing, and precipitation extreme fingerprint. This work will improve our understanding of (1) characteristics of atmospheric circulation and the relationship between the mean and the leading mode of variability; (2) the seasonal dependence in the response of the circulation over different sectors of the globe; (3) mechanism-based interpretation of the response of hydrological cycle and its extremes to GHG warming. Broader impacts encompass the following aspects: (1) The confidence gained in regional hydrological projection is valuable to water resource management and water policy making; (2) Several graduate and undergraduate students from two institutions will be trained and extensively involved; (3) Modeling outputs from this project will be archived in the "community-oriented" High Performance Storage System (HPSS) archive service system at National Center for Atmospheric Research (NCAR) to facilitate the sharing of the data to broader scientific communities.