Fig. 1: Results from the IsoGSM2 tagging simulation.
a Schematic representation of moisture source regions considered in this study (color-coded by names: the Arabian Sea, Red Sea, and the Gulf of Oman (ARAB), Bay of Bengal (BoB), northern Indian Ocean (10°N to 10°S (NIO), southern Indian Ocean (10°S to 20°S (SIO), land surfaces (as shown) (LND), and the western part of the Pacific Ocean (as shown) (PCO). Locations of the speleothem δ18O records discussed in the text are marked by yellow circles. The core monsoon zone (CMZ, approximately from 18°N, 28°N, and 69°E, 89°E) is depicted by a polygon. b Hovmöller diagram showing the seasonal evolution of tagged vapor as a fraction of total precipitable water (TPW) (%) from each source region (longitudinally averaged between 70°E and 94°E) and spanning between −5°S and 40°N. The June to September monsoon season is highlighted by dotted black lines. c Histograms showing relative contributions of each vapor source (%) to TPW averaged over the CMZ for pre-monsoon (April–May, MAM), monsoon (June–September, JJAS), and post-monsoon (September–October, SO) seasons. d Correlations between IsoGSM238 simulated monthly anomalies of oxygen isotopic composition of precipitable water (δ18Opw) and fractional moisture (%) for each vapor source over the CMZ during pre-monsoon, monsoon, and post-monsoon seasons (circles). Monthly anomalies were calculated by removing the long-term climatological mean (1979–2010) for each calendar month of the pre-monsoon (April–May), monsoon (June through September), and post-monsoon (October) seasons from each month’s individual value. The circles’ sizes are proportional to the Pearson correlation coefficients (r). The shaded boxes indicate values that are statistically significant (P < 0.05 one-tailed, t test; after accounting for autocorrelation). The period of the analysis is from 1979 to 2010.
