Multi-scale variations and future projections of dry-wet conditions over the monsoon transitional zone in East Asia:...

The East Asian monsoon transitional zone (MTZ) is a northeast-southwest oriented belt between the wet monsoon areas and the northwestern dry areas of China with a fragile ecology and high climate sensitivity. The climate in the MTZ is characterized by strong instability and large variability, resulting in frequent occurrence of extreme weather and climate events. A number of studies have focused on the dry-wet characteristics from different perspectives, taking into account the increasing problems of water scarcity and ecological risks. This study reviews the multi-scale variations, underlying mechanisms and future projections of dry-wet conditions over the MTZ under global warming. The main findings over the last few decades are summarized as follows: 1) the interannual variability of summer precipitation is under the combined impacts of oceanic forcings and internal atmospheric teleconnection patterns at mid-high latitudes; 2) an interdecadal decrease in summer precipitation amount in the MTZ was observed in the late 1990s due to a Silk-Road pattern-like wave train triggered by the combined impacts of the Atlantic Multidecadal Oscillation-like SST warming over the North Atlantic and positive-to-negative phase shift of the Pacific Decadal Oscillation (PDO); 3) a pronounced drying trend has been observed during 1951-2005, which is mainly attributed to human activities and internal atmospheric variability, including increased aerosols, land-use changes, thermal forcing over the Tibetan Plateau, and the phase shift of the PDO; and 4) the summer precipitation in the MTZ is projected to increase under global warming with considerable uncertainties mainly due to internal atmospheric variability, including the Arctic Oscillation and the Polar-Eurasian pattern. This review attempts to provide a clear and systematic picture on the distinctive changing features of dry-wet conditions over the MTZ, and to attract the interest of the scientific community in climate change over this unique "transition" domain.