The primary objective of my research is to understand the fundamental dynamical processes in the atmosphere and improve the state-of-the-art climate models, which could give us better apprehension and prediction of the changing climate. At present, my research interests are in the dynamics of atmospheric circulations and their variabilities in the changing climate, with a focus on subseasonal tropical-extratropical interaction and the influence of large-scale circulations on weather extremes. My research apparatus is built with a fusion of advanced statistical methods, idealized general circulation models (GCM), and state of the art climate models.
The mechanisms of subseasonal variabilities of midlatitude jet streams made the main theme of my Ph.D. research. I investigated two distinct variabilities of the North Atlantic jet stream: the north-south meanders, and the poleward shift of zonal wind anomalies. I identified the circumglobal wave trains associated with tropical convection anomaly as a crucial driver of the meanders of the North Atlantic jet (Yuan et al. 2011). On the other hand, the interaction between Rossby wave breaking and the critical latitude propels the poleward shift of zonal wind anomaly: synoptic scale Rossby waves propagate equatorward and break when encountering their critical latitudes, forming a new critical latitude slightly poleward, where subsequent wave breaking takes place (Yuan et al. 2013). A further investigation of the tropical influences on midlatitude weather was completed in my postdoctoral work at Peking University. I found that winter-time tropical convection anomalies over the Maritime Continent could excite planetary waves, which propagate toward the eastern Pacific and develop a circulation pattern that makes the west-coast United States more prone to drought in the following spring. This teleconnection circulation pattern, also known as the eastern Pacific (EP) pattern, was extracted using an advanced analysis method -- the self-organizing map (SOM), which in many aspects is superior to the conventional feature extraction methods such as Empirical Orthogonal Functions (EOF) analysis (Yuan et al. 2015). My current work at Duke University is directed to the response of large-scale circulations in the changing climate, and its effects on regional weather patterns and the frequency of extreme events.Accompanying the change in the large-scale circulations, anomalous moisture flux convergence could increase the severity and risk of drought or flood in some regions.