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Abstract

It is well established that tropical climate has variations on timescales ranging from a few hours to decades. It remains a challenge, however, to decouple the relative contributions of warming-related changes and decadal to multidecadal scale variations. Our work here focuses on the long-term river discharge in the Ganges basin, with a broader goal to understand the basin response to rainfall. We find similarities between the two from sub seasonal to decadal scales, and on examining the strength of these variations for different seasons we also find a marked difference in their strength between the monsoonal and post monsoonal seasons. A continuous wavelet transform analysis reveals that a 13-year cycle persists in discharge and rainfall for most of the recorded period. Finally, we explore for identical decadal scale features in the sea level pressure, which is known to have a broad large-scale correspondence with rainfall. We find similar features in the tropics with large hot spots of decadal variability in the southeast Asian region (which happens to encompass the Ganges basin too) and the south tropical Atlantic Ocean region.