The El Niño-Southern Oscillation (ENSO) and seasonal flooding – Bangladesh
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Although the El Niño-Southern Oscillation (ENSO) affects one-quarter of the globe to a significant extent, scientific research in Bangladesh relating to ENSO is just beginning. The prime objective of this paper is to provide an improved description of the ENSO-related flooding variability in Bangladesh. Information analyzed for this study includes: i) locally available Bangladesh rainfall and flood-affected area data, and ii) globally available precipitation, sea surface temperature (SST), and atmospheric circulation data.
The study revealed that Bangladesh climate – despite weak quantitative correspondence between the strength of ENSO and the rainfall anomaly – has particularly a strong relation when SOI (Southern Oscillation Index) extremes, negative SOIs for dry, and positive SOIs for wet. In the case of a moderate anomaly in the SOI, the index-climate relation appeared to be contradictory and, in particular, Bangladesh is wet during moderate El Niño years. Therefore, while the relation between SOI – rainfall in the upstream Ganges-Brahmaputra-Meghna (GBM) basins in India is strong, the same SOI – rainfall relationship offers limited applicability in the context of Bangladesh climate. So, understanding the broad-scale features of the Asian monsoon with especial emphasis to Bangladesh is essential. Further, the simultaneous development of SOI – rainfall relationship limits its use for seasonal forecasting in Bangladesh. Therefore, this study, in addition to examining the SOI – rainfall relationship, emphasizes the role of the warm/cold sea surface temperature (SST) in the tropical Pacific/Indian Ocean along with atmospheric circulation patterns for seasonal climate predictions in Bangladesh. It concludes that a close co-operation between the local institutions and those of International forecast centers would be essential for seasonal climate forecasting in Bangladesh.
KeywordsAtmospheric Circulation Seasonal Flooding Southern Oscillation Index Seasonal Climate Seasonal Forecast
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