Title: On the Role of Large Scale Atmospheric Circulation in Weather Extremes
Abstract: Changes in weather extremes such as heat waves, cold spells, and heavy precipitation are responsible for a large part of climate-related damage, yet our understanding of these extreme events is limited. Extreme weather events are identified by either the probability distribution function (PDF) of meteorological variables (e.g., temperature, moisture, or precipitation) or the pattern of large-scale circulations (e.g., jet stream meandering or blocking). Yet the probability distribution of these events often displays non-Gaussian tails that are common to the PDFs of dynamical or chemical tracers subject to the advection-diffusion processes, and the tails of these PDFs are particularly important for our understanding of weather extremes. In this talk, I will discuss an approach to transforming the prototypes of the advection-diffusion dynamics to the analysis in weather extremes. Such a transformation highlights the Lagrangian perspective of atmospheric dynamics and connects the PDF of weather events to the large scale atmospheric circulation quantitatively. This framework allows us to relate the source of non-Gaussianity of near-surface temperature to the nonlinear advection of temperature and the large scale jet stream variability. It also provides a useful diagnostic for the hydrological cycle in terms of thermodynamic and dynamic contributions over a full probability distribution of precipitation events.