Space- and time-varying associations between Bangladesh’s seasonal rainfall and large-scale climate oscillations

Understanding teleconnections of a region’s climate can be beneficial to seasonal outlooks and hydro-climate services. This study aims at analyzing the rainfall over Bangladesh with selected indices, including El Niño/Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), Pacific Decadal (PDO), Atlantic Multidecadal (AMO) indices. Rainfall data spanning from 1965 2017 in seven hydrological regions are used derive three rains, namely pre-monsoon (March–May), monsoon (June–September), post-monsoon (October November) for correlation- wavelet coherence (WC)-based teleconnection analyses. Among rain shows negative correlations, strongest IOD ENSO Correlations between pre-monsoon/monsoon indices subject notable spatial temporal variations. For instance, correlations (monsoon) South Central (South West) region (ENSO) index shift positive after 1980s, whereas comprehensive further enhanced early recent epochs. WC analysis not only corroborates findings correlation shorter time scales (e.g., 1–4 years), but also reveals significant longer 8–16 years). We find that rains experience phase change scales. In contrast, consistent anti-phase WC, more dominant scale. Both analyses indicate association patterns PDO mimic those ENSO. Lastly, results AMO suggest quite distinct Bangladesh’s Ocean.