Heatwaves Over Bangladesh: Long-Term Trends and Contributing Factors

Heatwave intensity, duration, and frequency over Bangladesh have risen significantly in recent decades and are projected to increase further under continued global warming. Yet, their underlying characteristics and drivers remain underexplored. This study examines long-term trends and mechanisms of heatwaves across pre-monsoon and monsoon seasons during 1971–2024 using ERA5 reanalysis data. Results show that the monsoon is experiencing an accelerated warming trend, with daily maximum temperature (T2Mmax) increasing at a rate three times greater than that of the pre-monsoon. Simultaneously, daily maximum equivalent potential temperature (EPTmax) is rising nine times and over three times faster than the corresponding T2Mmax rates in the pre-monsoon and monsoon, respectively. These changes have caused the frequency of extreme T2Mmax and EPTmax to increase by 30% and 167% in the pre-monsoon and by 457% and 661% during the monsoon, respectively. Consequently, the number of mean heatwave days has increased by about 25 days during the pre-monsoon and 40 days during the monsoon since 2000. Synoptic analyses reveal that quasi-stationary mid-tropospheric anticyclones are the primary drivers of heatwaves, which promote subsidence, cloud suppression, and enhanced surface radiative heating. Land-atmosphere interactions then further exacerbate these conditions. Collectively, these findings demonstrate that circulation patterns, soil moisture, and humidity play critical roles in driving the intensity and persistence of heatwaves over Bangladesh. This study advances the understanding of regional heatwave dynamics and provides actionable insights for evidence-based climate adaptation, disaster risk reduction, and public health resilience planning in South Asia.