Modeled Influence of East Asian Black Carbon on Inter-Decadal Shifts in East China Summer Rainfall

Two inter-decadal shifts in East China summer rainfall during the last three decades of the 20th century have been identified. One shift occurred in the late 1970s and featured more rainfall in the Yangtze River valley and prolonged drought in North China. The other shift occurred in the early 1990s and featured increased rainfall in South China. The role of black carbon (BC) aerosol in the first shift event is controversial, and it has not been documented for the second event. In this study, the authors used Geophysical Fluid Dynamics Laboratory’s (GFDL’s) atmospheric general circulation model known as Atmosphere and Land Model (AM2.1), which has been shown to capture East Asian climate variability well, to investigate these issues by conducting sensitive experiments with or without historical BC in East Asia. The results suggest that the model reproduces the first shift well, including intensified rainfall in the Yangtze River and weakened monsoonal circulation. However, the model captures only a fraction of the observed variations for the second shift event. Thus, the role of BC in modulating the two shift events is different, and its impact is relatively less important for the early 1990s event.