The analysis of detailed characteristics of rainfall is of utmost importance for understanding water resources, irrigation, and agriculture. This study investigated detailed characteristics of rainfall of Bangladesh from 1966 to 2019. Rainfall features like the precipitation concentration index (PCI) and seasonality index (SI) were estimated to characterize spatial patterns of rainfall regimes, and innovative trend analysis (ITA) and percent bias (P_BIAS) were used to detect the trend, and its reliability was tested by using the Mann–Kendall (MK) or modified Mann–Kendall (mMK) test. The magnitude of changes was computed by using Sen’s slope estimator (Q), and discrete wavelet transform (DWT) was employed to find out the dominant periodicity of the trend of annual series. SI and PCI revealed that rainfall is mainly seasonal and markedly with the long dry season, and the distribution of rainfall is irregular for the major portion of Bangladesh. The result of ITA and P_BIAS showed a similar trend for all the stations and time scales. ITA showed that 23 stations experienced significant (α = < 0.05) increasing (39.13%) and decreasing (39.13%) trends in annual rainfall. For the seasonal scale, post-monsoon rainfall is dominated by significant increasing trend (60.87%), whereas winter rainfall is dominated by significant decreasing trend (65.28%); besides, both decreasing and increasing trends were found in pre-monsoon and monsoon in Bangladesh. The analysis of DWT confirmed that 4- to 16-year periodic cycle was the dominant component for annual rainfall. The results of detailed analysis of rainfall will be helpful for policymakers and scientists to focus on regional-scale planning about flood and drought situation of the country that will be ultimately helpful for agricultural development and environmental planning.

降雨详细特征的分析对于理解水资源，灌溉和农业至关重要。这项研究调查了1966年至2019年孟加拉国的详细降雨特征。估计了诸如降雨集中指数（PCI）和季节性指数（SI）之类的降雨特征，以表征降雨制度的空间格局，创新趋势分析（ITA）和偏差百分比（P _BIAS）用于检测趋势，并使用Mann-Kendall（MK）或改进的Mann-Kendall（mMK）测试来测试其趋势。通过使用Sen的斜率估计器（Q）计算变化的幅度，并使用离散小波变换（DWT）找出年序列趋势的主要周期性。SI和PCI显示，降雨主要是季节性的，并且明显地与干旱季节有关，而孟加拉国大部分地区的降雨分布是不规则的。ITA和P _BIAS的结果在所有台站和时标上都显示出相似的趋势。ITA显示，有23个站点经历了显着（α = <0.05）年降雨量增加（39.13％）和减少（39.13％）趋势。在季节尺度上，季风后降雨以显着增加趋势为主（60.87％），而冬季降雨以显着减少趋势为主（65.28％）；此外，孟加拉的季风前和季风都有下降和上升的趋势。DWT的分析证实，4至16年的周期性周期是年降雨量的主要组成部分。降雨的详细分析结果将有助于决策者和科学家将重点放在有关该国洪水和干旱情况的区域规模计划上，这最终将有助于农业发展和环境规划。