The meteorological stations across Bangladesh.

Heat waves significantly impact people’s lives and livelihoods and are becoming very alarming and recognized as hot topics worldwide, including in Bangladesh. However, much less is understood regarding recent hotspots, the frequency of heat waves over time, and their underlying causes in Bangladesh. The objective of the study is to explore the current scenario and frequency of heat waves and their possible causes across Bangladesh. The Mann-Kendall and Sen’s slope techniques were used to determine seasonal and annual temperature trend patterns of heat wave frequencies. Daily maximum temperature datasets collected from the Bangladesh Meteorological Department (BMD) during 1991–2021 are applied. The frequency of days with Tmax≥ 36°C as the threshold was used to compute different types of heat waves based on the BMD’s operational definition. The results show that the mild heat wave (MHW) days followed the subsequent hotspot order: Rajshahi (103) > Chuadanga (79), Ishurdi (60), and Jessore (58), respectively. The frequency of days with Tmax≥36°C was persistence for many days in 2014, especially in the western part of Bangladesh compared to other parts. Similarly, the heat waves condition shown its deadliest event by increasing more days in 2021. The highest increasing trend was identified at the Patuakhali site, with a rate of 0.516 days/year, while the highest decreasing trend was noticed at the Chuadanga site, with a rate of -0.588 days/year. The frequency of days (Tmax≥36°C) is an increasing trend in the south-western part of Bangladesh. The synoptic condition in and around Bangladesh demonstrates that the entrance of heat waves in Bangladesh is due to the advection of higher temperatures from the south/southwest of the Bay of Bengal. The outcomes will guide the national appraisal of heatwave effects, shedding light on the primary causes of definite heatwave phenomena, which are crucial for developing practical adaptation tools.

热浪对人类生活与生计造成显著影响，如今其威胁性日益凸显，已成为包括孟加拉国在内的全球热议话题。然而目前学界对孟加拉国境内的近期热浪热点、长期热浪发生频次及其潜在成因的认知仍较为匮乏。本研究旨在探究孟加拉国全境的热浪现状、发生频次及其潜在成因。研究采用曼-肯德尔检验（Mann-Kendall）与森斜率（Sen’s slope）分析法，以明确热浪频次的季节与年度温度趋势特征。本研究使用了孟加拉国气象部门（Bangladesh Meteorological Department, BMD）1991年至2021年的逐日最高气温（Tmax）数据集。依据孟加拉国气象部门的业务定义，本研究以日最高气温≥36℃为阈值，计算不同等级的热浪发生频次。研究结果显示，轻度热浪（mild heat wave, MHW）日数的热点区域排序依次为：拉杰沙希（103天）＞朱帕当加（79天）、伊舒尔迪（60天）与杰索尔（58天）。2014年，日最高气温≥36℃的天数持续偏多，其中孟加拉国西部区域的超标天数较其他地区更为显著。同样，2021年热浪日数进一步增加，达到该研究时段内最严重的热浪事件水平。帕图阿哈利站点的热浪频次增长趋势最为显著，增速为0.516天/年；而朱帕当加站点的下降趋势最为明显，降幅为-0.588天/年。孟加拉国西南部区域的日最高气温≥36℃天数整体呈上升趋势。孟加拉国及其周边的天气形势分析表明，该国的热浪事件主要源于孟加拉湾南部/西南部的暖平流输送。本研究结果可为国家层面的热浪影响评估提供参考，明确特定热浪事件的核心成因，对制定切实可行的热浪适应措施具有重要意义。