Abstract
Understanding teleconnections of a region’s climate can be beneficial to seasonal outlooks and hydro-climate services. This study aims at analyzing the teleconnections of seasonal rainfall over Bangladesh with selected climate indices, including El Niño/Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO) indices. Rainfall data spanning from 1965 to 2017 in the seven hydrological regions are used to derive three seasonal rains, namely the pre-monsoon (March–May), monsoon (June–September), and post-monsoon (October and November) rains, for correlation- and wavelet coherence (WC)-based teleconnection analyses. Among the three seasonal rains, the post-monsoon rain shows the negative correlations, strongest with the IOD and ENSO indices. Correlations between the pre-monsoon/monsoon rain and climate indices are subject to notable spatial and temporal variations. For instance, correlations between the pre-monsoon (monsoon) rain in the South Central (South West) region and the IOD (ENSO) index shift from negative to positive after the 1980s, whereas the comprehensive negative correlations of the post-monsoon rain with the IOD and ENSO indices further enhanced from the early to recent epochs. WC analysis not only corroborates the findings of correlation analysis at shorter time scales (e.g., 1–4 years), but also reveals significant coherence at longer time scales (e.g., 8–16 years). We find that the pre-monsoon and monsoon rains experience the phase change in WC from shorter to longer scales. In contrast, the post-monsoon rain shows the consistent anti-phase WC, more dominant at the longer time scale. Both correlation and WC analyses indicate that the association patterns of the PDO mimic those of ENSO. Lastly, the analysis results of the AMO suggest quite distinct and significant association between Bangladesh’s rainfall and the Atlantic Ocean.
Highlights
Teleconnection refers to the remote association of local or regional hydrometeorological variables with large-scale atmospheric/oceanic circulation patterns
4 Results and discussion 4.1 Composite analysis for three seasonal rains Prior to examining the results of teleconnection analysis, we explored the general mechanism of rainfall variability in Bangladesh using composite analysis
We developed composite maps for the anomalous fields of 850-mb vector wind and geopotential height (GPH) and precipitable water during the wet and dry years corresponding to each of the seasonal rains, identified based on the country’s average seasonal rainfall amount higher and lower the 67th and
Summary
Teleconnection refers to the remote association of local or regional hydrometeorological variables with large-scale atmospheric/oceanic circulation patterns. Numerous teleconnection studies have revealed that South Asian Monsoon (SAM) is modulated by many large-scale circulation patterns, including the El Nino-Southern Oscillation (ENSO) [64, 63, 47, 40, 37], Indian Ocean Dipole (IOD) [56, 8, 9, 69], Atlantic Multidecadal Oscillation (AMO) [79, 23, 36], and Pacific Decadal Oscillation (PDO) [34, 35, 38, 60, 59]. [52] found moderate correlation between monthly rainfall and the Southern Oscillation Index (SOI) during the period 1981–2004. [51]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
