Atmospheric Blocking: Dynamics and Responses to Climate Change

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Atmospheric blocking events are an important contributor to high impact extreme weather events. Improving the forecasts of blocking events and assessing how the frequency, severity, and location of such events may change with climate change are of substantial societal importance. Synoptic eddies have been shown to play a critical role in the dynamics of atmospheric blocking events by maintaining the blocking pattern but the understanding of their role is currently not sufficiently complete and quantitative. The goals of the proposed research are 1) to improve the dynamical understanding of atmospheric blocking events through developing a quantitative assessment of synoptic-eddy forcing of blocks. 2) to employ this dynamical understanding to investigate how blocking events will change with climate change and how blocks can be better simulated in climate and weather models. The proposed research will employ numerical experiments with a hierarchy of general circulation models, reanalysis data, and archived results of full-physics general circulation models such as Coupled Model Intercomparison Project models. The research has three components: the first is to study the eddy-forcing mechanism using idealized modeling experiments which to isolate and develop a quantitative understanding of this mechanism. The same idealized framework will be used to investigate how the speed and latitude of jet streams, different patterns of quasi-stationary planetary waves, and moisture modulate this mechanism. The second component is to test this understanding using the reanalysis data and to gain further insight into the dynamic of observed blocking events. The third component is to apply this understanding to examine the performance of full-physics models in simulating blocking, and to provide a more reliable and conclusive prediction on how blocking events will change in the future.