Major Floods and Tropical Cyclones over Bangladesh: Clustering from ENSO Timescales

Abstract

The present study analyzed major floods and tropical cyclones (TCs) over Bangladesh on El Niño-Southern Oscillation (ENSO) timescales. The geographical location, low and almost flat topography have introduced Bangladesh as one of the most vulnerable countries of the world. Bangladesh is highly vulnerable to the extreme hazard events like floods and cyclones which are impacted by ENSO. ENSO is mainly a tropical event, but its impact is global. El Niño (La Niña) represents the warm (cold) phase of the ENSO cycle. Rainfall and cyclonic disturbances data have been used for the period of 70 years (1948–2017) and compared with the corresponding observations of the Southern Oscillation Index. Result shows that major flood events occurred during the monsoon period, and most of them are during the La Niña condition, consistent with the historical archives of flood events in Bangladesh. Synoptic conditions of these events are well matched during La Niña condition. On the other hand, the major TC cases are in the period of either pre-monsoon or post-monsoon season. The pre-monsoon cases are under neutral (developing La Niña) or El Niño and the post-monsoon cases are under La Niña, consistent with climatology studies that La Niña is favorable to have more intense TCs over the Bay of Bengal.

Influence of Terrestrial Precipitation on the Variability of Extreme Sea Levels along the Coast of Bangladesh

“…Interestingly, the highest SLAs were observed in May (Figure 10a), and the difference in R 2 for these events was generally small. We confirmed that these events mostly occurred in early May in 1995 and 1997, and there were tropical cyclones or tropical depressions over the study area [59,60]. Hence, it is very likely that these ESL events were strongly influenced by SLP and winds, rather than the precipitation effect.…”

“…It was found that the ESLs were influenced by the high precipitation during the monsoon season. The extreme sea levels intensify coastal inundation and cause coastal floods with high precipitation during monsoons [8,32,57,59,65]. Therefore, the attempt of this study relating to predictions of ESL has implications for the reduction of coastal hazards.…”

A Kernel Density Estimation Approach and Statistical Generalized Additive Model of Western North Pacific Typhoon Activities

“…A generalized additive model (GAM) is a powerful and simple technique and easy to interpret based on the flexibility and regularization of prediction functions [32][33][34][35][36][37] Modeling studies will be a great societal value when the risk-mitigation policies are considered and future planning efforts are focused to the most high-risk areas [38][39][40][41][42]. In the present study, we have used a kernel density estimation approach and GAM to observe the typhoon characteristics in the WNP basin.…”

Spatiotemporal Variability of Drought and Its Multi-Scale Linkages with Climate Indices in the Huaihe River Basin, Central China and East China

“…Atmosphere 2021, 12,1446 2 of 20 In recent years, a lot of research has been conducted to detect the possible relation between large-scale climate phenomena and droughts or floods in specific geographical locations [2,5,[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Wahiduzzaman concluded that major flood events over Bangladesh occurred during the monsoon period, and most of them occurred under the La Niña condition [24]. Sobral et al detected the relation between the annual SPI index and the El Niño-Southern Oscillation (ENSO), and found that the events of El Niño and La Niña were not directly related to the variation in rainfall in any region of South Rio de Janeiro (SRJ) [25].…”