Assessing Heatwave Severity and Trends in the Southwest Coast Region of Bangladesh Using Heat Index
Humaira Rahman Logna *
Department of Geography and Environment, Jahangirnagar University, Dhaka 1342, Bangladesh.
Md Anarul Haque Mondol
Department of Geography and Environment, Jahangirnagar University, Dhaka 1342, Bangladesh.
Sworna Akter
Department of Geography and Environment, Jahangirnagar University, Dhaka 1342, Bangladesh.
Hafizur Rahman
Department of Environmental Science and Management, School of Environment and Life Sciences, Independent University, Bangladesh (IUB), Dhaka 1245, Bangladesh.
*Author to whom correspondence should be addressed.
Abstract
Background and Aims: Bangladesh is among the countries highly susceptible to heatwaves and heat stress. This study aims to analyse the severity and growing intensity of heatwaves in the southwest coast region of Bangladesh. It investigates the potential increase in the frequency of seasonal heatwaves and of moderate and severe heatwaves in the southwest coast region.
Place and Duration of Study: The southwest coast region of Bangladesh, from 1981 to 2020.
Methodology: Heat Index (HI) was calculated from air temperature and humidity data using Steadman’s formula for apparent temperature. The Bangladesh Meteorological Department’s standard definition and classification of heatwaves were applied to the HI values, and temporal trends were detected using the Mann-Kendall test. Intensification of seasonal, moderate and severe heatwaves was measured using linear regression, the coefficient of determination, and statistical significance tests.
Results: The results show statistically significant intensification of heatwave patterns across the region (P = .01 in Bhola; P < .001 in Khulna, Barishal and Satkhira; τ = 0.28–0.54). The temporal trend of heatwaves indicates that Khulna was the most affected by heat stress. The intensification of moderate and severe heatwaves is more noticeable after 2000 (April-September). However, severe heatwaves intensified most during the last decade (post-2011). The monsoon season experiences the most heatwaves, particularly in Barishal (slope = 1.27, R2 = 0.65). The strongest increasing trend in moderate heatwaves was also observed in Barishal (slope = 1.11, P-value < .001), followed by Khulna (slope = 0.91, P-value < .001). Khulna showed the strongest rising trend in severe heatwaves (slope = 0.75, P-value < .001). Most heatwaves in the southwest coast region lasted 3 days, although longer events were also observed (IQR = 5-7).
Conclusion: The findings show spatial variability in heatwave behaviour, underlining the need for more localised adaptive measures to cope with increasing heat. To understand nationwide heatwave risks, future studies should cover a broader region and include additional socioeconomic indicators to assess the impact of heatwave occurrences on the local population.
Keywords: Heatwaves, heat index, humidity, coastal region, Bangladesh