Influence of El Niño–Southern Oscillation on the long-term record of floods over Bangladesh.

The present study analyzed a long-term record of major floods over Bangladesh under the influence of El Niño–Southern Oscillation (ENSO). Bangladesh is highly vulnerable to floods, and ENSO has a great influence on it. El Niño (La Niña) represents the warm (cold) phase of the ENSO cycle. Southern Oscillation Index data and a long-term flood records have been identified from National Oceanic and Atmospheric Administration, Bureau of Meteorology, Australia, and historical archives, respectively. Synoptic features—precipitation, wind, geopotential height, precipitable water, relative humidity, and surface runoff data—were used to examine the influence of ENSO. Result shows that the Indian summer monsoon contributes the major flood events and largely influenced by both El Niño and La Niña events, with a slightly higher frequency for the latter. Physical mechanisms (distribution of precipitation, wind, geopotential height, precipitable water, relative humidity, and surface runoff) supported these flood events; however, they are quite distinct during El Niño and La Niña condition. Moreover, ENSO's impacts to the Bangladesh region are different to the west part of the monsoon region. Therefore, if ENSO forecast is reliable, the predictability of the monsoon-related flood events can be improved. [ABSTRACT FROM AUTHOR]