Fig. 2: Weak minus strong JJAS composites of climatological fields and “tagged” moisture anomalies.

a JJAS mean precipitation anomalies from the European Centre Medium-Range Weather Forecasts Reanalysis Fifth generation (ERA-5)⁷¹ (left), vertically integrated zonal flux anomalies (middle), and meridional moisture flux anomalies (right) from ERA-5⁷¹ (shaded). b JJAS moisture anomalies from ARAB (left), SIO (middle), and LND (left). c, d JJAS moisture (% TPW) (shaded) from ARAB (left), BoB (middle), NIO (right), SIO (left), PCO (middle), LND regions (right) are superimposed by simulated vertically integrated moisture flux anomalies over the same period (1979–2010). Circles in all panels mark the locations of the cave records discussed in the text. The strong (1983, 1988, and 1994) and weak (1982, 1987, 2002, 2004, and 2009) monsoon seasons are defined as positive (negative) departures of one standard deviation from the mean of All India Rainfall⁵⁴. The weak monsoon years are characterized by (i) negative precipitation anomalies over much of continental India except over northeast, northern BoB, and the coastal Myanmar regions; (ii) reduced vertically integrated zonal moisture flux along the climatological axis of the LLJ over the Arabian Sea, compensated by anomalously enhanced northwest-southeast trending zonal moisture flux across north India (with its core at ~25°N) and near the equator; (iii) negative meridional moisture flux anomalies, particularly east of 75°E over the Indian subcontinent.