Sources of moisture for China and their variations during drier and wetter conditions in 2000-2004: a Lagrangian approach

We provide an overview of the sources of moisture that affect the major regimes of precipitation in China during the extended boreal summer (from April to September), as well as some indication of the variations in these sources during drier and wetter conditions. The Lagrangian FLEXPART model was used to identify the contributions of humidity to the moisture budget in a region by computing the changes in specific humidity along the backward trajectories of air masses for the previous 10 d. We carried out analyses for 2000 to 2004 and identified those years that had the highest and lowest average rates of precipitation in 13 different regions in China, each of which is characterised by different regimes in terms of precipitation. Although the period of the study was relatively short, the results suggest that the contributions of moisture from the East and South China Seas are significant for precipitation in the eastern and southeastern coastal areas, while the Arabian Sea and the Bay of Bengal are important sources of moisture for the southern and central regions of China. Moreover, the northern regions receive some moisture from western Asia. Our analysis of wetter and drier years suggests that, in general, a more unstable atmosphere prevailed over the different target areas during all wetter periods considered.