Impact of the Eastward Shift in the Negative‐Phase NAO on Extreme Drought Over Northern China in Summer

Abstract

AbstractThe frequency of extreme drought events in northern China has increased since the mid‐1990s, and such a decadal anomalous trend may have a vital influence on national economics and food supply. Based on the analysis of observational datasets and experiments conducted by a linear baroclinic model, this study claims that the intraseasonal circulation anomalies related to extreme drought are linked to the eastward shift in the negative phase of the summer North Atlantic Oscillation (SNAO). When the SNAO is in a negative phase, the cyclonic eddy‐driven jet can enhance the eastward extension of the North Atlantic jet stream (NAJS), contributing to a closer connection between the NAJS and the Asian‐African jet stream and enhancing the waveguide. The cyclonic eddy in the exit of the jet stream excites anomalous Rossby wave energy that originates from the NAJS exit and spreads to the Caspian Sea, Mongolia, and northern China; this associated wave train, which is similar to the Silk Road Pattern (SRP), enhances the anticyclonic anomaly over northern China, establishing a pronounced link with extreme drought in northern China. Thus, the negative phase of the SNAO may be a contributing driver of extreme drought in northern China.