Search

Stable hydrogen isotopes in monsoonal precipitation (δDp) at three sites (Port Blair, Barisal and Darjeeling) reveal the factors governing δDp variations over a south‐north gradient across the Bay of Bengal. We found that the δDp at each site continuously decreases from May to September and these trends become more pronounced from south to north. The decreasing trends of downstream δDp closely follow the decreasing trends of upstream stable hydrogen isotopes in water vapor (δDv), which indicates that upstream δDv properties shape initial spatiotemporal patterns of the downstream δDp ("shaping effect"). Additionally, our results demonstrate that, during moisture transport, upstream vertical air motions (convection and downward motion) and topographic relief magnify the amplitude of the decreasing trends of downstream δDp ("magnifying effect"). Our findings imply that upstream δDv properties and relevant atmospheric and topographical conditions along the moisture transport pathway need to be considered collectively to better interpret paleoclimate records. Plain Language Summary: The stable isotope records from paleoclimate archives in South Asia have been widely used to indicate the Indian Summer Monsoon (ISM) intensity. However, precipitation stable isotopes across most areas of South Asia show a continuous decrease throughout the monsoon season, which does not track the ISM intensity. Clearly, factors other than the ISM influence the variability of the monsoonal precipitation stable isotopes. Here, we reveal the factors governing the variations of precipitation stable hydrogen isotopes (δDp) over a south‐north gradient across the Bay of Bengal using the δDp at three sites (Port Blair, Barisal and Darjeeling). Our results show that a gradual decreasing trend of δDp from May to September appears at each site. We find that changes in stable hydrogen isotopes in upstream water vapor (δDv) largely control the decreasing trends of downstream δDp from May to September. In addition, we also find that the decreasing trends of δDp gradually strengthen from south to north. These patterns are attributed to the continuous enhancing influences of upstream vertical air motions, including upstream accumulative convection and downward motion, and topographic relief from south to north. These findings help to explain the inconsistency between the lowest δDp and the strongest ISM. Key Points: δDp at each site continuously decreases in May‒September and amplitude of decreasing trends gradually strengthens from south to northUpstream water vapor isotope properties shape the continuous decreasing trends of downstream δDpUpstream vertical air motions and topographic relief magnify the amplitude of the decreasing trends of the downstream δDp [ABSTRACT FROM AUTHOR]

The proliferation of preferential trading agreements (PTAs) in different regions of the world has been a significant development over the last two decades. South Asian countries have been slowly moving towards a South Asia Free Trade Area (SAFTA) in recent years. The desirability of SAFTA has been questioned by some observers recently. Will SAFTA create gains for its members or not? Is it better for South Asian countries to promote non-discriminatory trade liberalisation rather than SAFTA? The main objective of this paper is to address the above questions, especially the desirability of SAFTA, using a global computable general equilibrium (CGE) model. From the existing empirical and theoretical studies, we have identified three viewpoints on the desirability (or viability) of SAFTA: pessimistic, optimistic, and moderate. The results from two policy scenarios (unilateral liberalisation and SAFTA) confirm the pessimistic view by showing that unilateral liberalisation would benefit South Asian countries much more than preferential liberalisation (SAFTA). In fact, under preferential liberalisation, small countries in the region would gain little or even lose. The present political climate in South Asia also seems to support the pessimistic view. [ABSTRACT FROM AUTHOR]