Climate precursors of satellite water marker index for spring cholera outbreak in Bengal Delta region

Abstract:

For spring cholera outbreak over the Bengal Delta region, satellite water marker (SWM) index in early-winter (October-December) is proposed as a good indicator. In this study, we investigated climate precursor of the SWM over the northern Bay of Bengal (BoB) with a lagged correlation analysis among SST, rainfall anomalies over India, and SWM anomaly over BoB. The results suggest that the positive rainfall anomaly by monsoon-ENSO relationship (i.e. enhanced rainfall over India during La Nina) can increase the turbidity and turbid river discharge over the Bengal Delta. Such monsoon-ENSO relationship and rainfall induced change of coastal water conditions (SWM) and biological activity (Chlorophyll-a) are also confirmed in the composite map. The La Nina signal can be traced back two seasons ahead of March-May season and hence could be a useful predictor. This study has been conducted as a part of the international and multidisciplinary project PODCAST (Pathways Of Dispersal for Cholera And Solution Tools), which aims to investigate climate influence on environmental reservoirs for cholera and help reduce outbreak risks for human health.