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<p>Heat wave days (HWDs) in Bangladesh have surged dramatically, increasing over 12-fold between 1994 and 2024, with recent maxima exceeding 60 HWDs per year in regions like Rajshahi, Khulna, and Dhaka. This escalation far outpaces the ~ 0.9&#xa0;°C rise in mean annual temperature, indicating a nonlinear intensification driven by land–atmosphere feedbacks, synoptic-scale circulation anomalies, and regional land use changes. Historically concentrated in the northwest, extreme heat events have spatially homogenized post-2014, with all divisions including coastal and temperate zones experiencing &gt; 30 HWDs in 2024. Five ‘mega-heat’ years (≥ 200 national HWDs) occurred between 2014 and 2024, reducing the return period from ~ 30 to &lt; 2&#xa0;years, signifying a breakdown in climate stationarity. Thermodynamic diagnostics reveal vertically stacked warming, suppressed convection, and persistent high-pressure ridging (cluster 1 conditions), especially over the Meghna Basin. This heating is vertically reinforced by a mid- to upper-tropospheric high-pressure ridge (500–300&#xa0;hPa), acting as a thermal dome that traps heat, limits vertical moisture transport, and enhances atmospheric stability, thereby sustaining HW intensity. The presence of deep atmospheric dryness coupled with strong subsidence represents key hallmarks of intense HW conditions prevailing over the Meghna Basin.</p>

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Climatological assessment of pre-monsoon heatwave days in Bangladesh and their relationship to Indo Pacific circulation anomalies

  • 期刊论文

  • 发表日期：

    2025年12月26日

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  • Murad Ahmed Farukh,
  • Partha Pratim Brahma,
  • Md. Sazzad Hossain,
  • Md. Jahidul Hoque,
  • Saida Islam Sejuti,
  • Ummoy Sumaia Shammy,
  • Khondakar Sumsul Arefin

摘要

Heat wave days (HWDs) in Bangladesh have surged dramatically, increasing over 12-fold between 1994 and 2024, with recent maxima exceeding 60 HWDs per year in regions like Rajshahi, Khulna, and Dhaka. This escalation far outpaces the ~ 0.9 °C rise in mean annual temperature, indicating a nonlinear intensification driven by land–atmosphere feedbacks, synoptic-scale circulation anomalies, and regional land use changes. Historically concentrated in the northwest, extreme heat events have spatially homogenized post-2014, with all divisions including coastal and temperate zones experiencing > 30 HWDs in 2024. Five ‘mega-heat’ years (≥ 200 national HWDs) occurred between 2014 and 2024, reducing the return period from ~ 30 to < 2 years, signifying a breakdown in climate stationarity. Thermodynamic diagnostics reveal vertically stacked warming, suppressed convection, and persistent high-pressure ridging (cluster 1 conditions), especially over the Meghna Basin. This heating is vertically reinforced by a mid- to upper-tropospheric high-pressure ridge (500–300 hPa), acting as a thermal dome that traps heat, limits vertical moisture transport, and enhances atmospheric stability, thereby sustaining HW intensity. The presence of deep atmospheric dryness coupled with strong subsidence represents key hallmarks of intense HW conditions prevailing over the Meghna Basin.