This study investigates the moisture sources that supply East Asian (EA) precipitation and their interannual variability. Moisture sources are tracked using the Water Accounting Model-2layers (WAM- 2layers), based on the Eulerian framework.WAM-2layers is applied to five subregions over EA, driven by the ERA-Interim reanalysis from 1979 to 2015. Due to differences in regional atmospheric circulation and in hydrological and topographic features, the mean moisture sources vary among EA subregions. The tropical oceanic source dominates southeastern EA, while the extratropical continental source dominates other EA subregions. The moisture sources experience large seasonal variations, due to the seasonal cycle of the EA monsoon, the freeze-thaw cycle of the Eurasian continent, and local moisture recycling over the Tibetan Plateau. The interannual variability of moisture sources is linked to interannual modes of the coupled ocean- atmosphere system. The negative phase of the North Atlantic Oscillation increases moisture transport to northwestern EA in winter by driving a southward shift in the midlatitude westerly jet over the Mediterranean Sea, the Black Sea, and the Caspian Sea. Atmospheric moisture lifetime is also reduced due to the enhanced westerlies. In summers following El Niños, an anticyclonic anomaly over the western North Pacific increases moisture supplied from the South China Sea to the southeastern EA and shortens the traveling distance. A stronger Somali Jet in summer increases moisture to the Tibetan Plateau and therefore increases precipitation over the eastern Tibetan Plateau. The methods and findings in this study can be used to evaluate hydrological features in climate simulations.@en

Sediment transport provides a critical bridge between hydrodynamics and morphodynamics. Sediment transport behaviour has obvious impacts on morphodynamic development. Long-term morphodynamic modelling enables examination of large scale morphological patterns, such as channel-shoal patterns in estuaries and deltaic channel structures. Non-cohesive sand is mostly used as the material in shaping morphology. However, most of estuaries and deltas in nature are partly or fully dominated by cohesive sediment or mud. There are researches on sand-mud interactions and their implications on total sediment transport (van Ledden, 2003). It is increasingly aware that adding mud to the system can make a big differences on the large scale morphodynamic development behaviour (Edmond and Slinger, 2009; Gelynese et al., 2010; Caldwel and Edmond, 2014). However mud transport is notoriously difficult to be defined properly in the model given the combined sensitivity to a few fundamental parameters (Partheniades, 1965; Mehta, 2014). It is thus not clearly known how mud have controls on development of large scale morphodynamics and the sensitivity to the mud property. @en

Model results suggest that 1) varying lateral bed-slope factor has strong impacts; larger value leads to gentler channel-shoal interface or smaller lateral channel bedslope. 2) Different sediment transport formulas lead to considerable differences in morphodynamic patterns. 3) Sediment transport formulas considering both suspension and bed load transport tolerate a smaller morphological acceleration factor and requires a larger bed-slope factor.@en

Estuarine morphodynamics undergo significant changes due to declined sediment supply from river, rising sea-level, and human interferences (Syvitski and Saito, 2007; Syvitski et al., 2009). The Yangtze Estuary is such a case whose decadal morphodynamic evolution was broadly examined. It was documented that the subaqueous delta shifted from deposition to erosion since the early 2000s due to sediment supply reduction after the Three Gorges Dam (Yang et al., 2015) while some others reported that the estuary mouth bar area sustains accretion until 2010 (Luan et al., 2016; Zhu et al., 2016). The mouth bar area of the Yangtze Estuary is where the turbidity maximum exists. To clarify the morphodynamic changes therein, we examine the two large scale shoals, i.e. the Hengsha flat and the Jiuduan shoal, based on bathymetric data between 1958 and 2016 and satellite images since 1985.@en