| Abstract: | Spatial and temporal variations in moisture conditions across monsoon Asia were investigated using 347 Monsoon Asia Drought Atlas(MADA) grid points and 100 Chinese historical documents sites during the years 1470-2000. We applied Rotated Empirical Orthogonal Function(REOF) analysis to evaluate spatial moisture variability during the past 530 years.The first 13 principal components together explained 61.35% of the total variance, with the First Principal Component(PC1) accounting for 14.1%. After varimax rotation to the first 13 EOFs, we obtained new time series and spatial patterns.These patterns divided monsoon Asia into 13 regions with coherent moisture variability. Drought events were analyzed within these 13 regions. The results indicate that there has been a prominent drying trend in eastern and central Mongolia,Southeast Asia and east China during the last 50 years. Conversely, India and the Tibetan Plateau show a significant increase in moisture around the late 20 th century. We found four drought periods, A.D. 1625-1644, A.D. 1710-1729, A.D.1920 s, and A.D. 1975-1999 occurred widely across monsoon Asia during the past 530 years. On inter-annual time scales,moisture variations in the northwest region of monsoon Asia, the Indian subcontinent and Southeast Asia are influenced by the El Ni?o-Southern Oscillation(ENSO). Thirty-year running correlation coefficient diagnostic analysis revealed that moisture variability in monsoon Asia is associated with the Pacific Decadal Oscillation(PDO). |
