Spatiotemporal changes of precipitation extremes in Bangladesh during 1987-2017 and their connections with climate changes, climate oscillations, and monsoon dynamics

This study provides a comprehensive framework to explore the spatiotemporal changes in precipitation extremes in Bangladesh, an important South Asian country, over the 1987-2017 period and their links with climate changes, large-scale climate oscillations (i.e., El Nin similar to o-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD)), and the East Asian Summer Monsoon (EASM) dynamics. Precipitation extremes are measured by ten extreme precipitation indices (EPIs) recommended by the Expert Team on Climate Change Detection and Indices. The comprehensive framework consists of an iterative-based Mann-Kendall trend analysis to explore the trends in the EPIs across the country and a joint analysis based on a Pearson product-moment correlation analysis and a multivariate linear regression to investigate the links of the EPIs with local to global climate changes, ENSO, IOD, and EASM dynamics. This study finds that precipitation extremes show clearly regional and seasonal differential changes across Bangladesh. All of the 28 stations across Bangladesh show positive trends for consecutive dry days, while 21 out of 28 stations show negative trends in annual total wet-day precipitation. Maximum 1-day precipitation amount and 5-day precipitation amount are increasing over the coastal areas during the monsoon season and decreasing in winter for most parts of Bangladesh. The trends of precipitation extremes show a clear spatial dependency on topography and distance from the coastline. Precipitation extremes in Bangladesh appear to respond more actively to IOD, local to global climate changes, and EASM than ENSO, especially for annual total wet-day precipitation, very and extreme wet days, and wet spells. In addition, precipitation extremes in coastal regions are more responsive to global warming than in inland regions. Most of the EPIs show negative associations with local temperature anomalies and the EASM strength. This study provides a new comprehensive look at the important links of extreme precipitations variations with climate changes, largescale climate oscillations, and EASM dynamics across Bangladesh.