2.1 Study area description
Bangladesh, positioned in subtropics has a hot and warm sub-humid climate which is mostly triggered by the monsoonal system, modulating topography, and complex hydrogeologic setting (Fig. 1). Most parts of the country are floodplain, excluding for few hilly regions in the southeastern and eastern areas (Rahman and Islam, 2019). The daily temperature in the country ranged between 18 °C and 32 °C with a mean of 26°C whereas the mean annual rainfall was 2400 mm (Islam et al. 2020a). The climate of the country is predominated by four seasons such as pre-monsoon hot monsoon (March–May), rainy and moist monsoon period (June-August), and post-monsoon (September- November) and dry winter (December–February) seasons (Islam et al. 2020a). The region is characterized by Hot and humid monsoon with high rainfall and dry and mild cold winter. Seasonal variations in temperature and rainfall are distinct features. Outlines of seasonal wind integrated with local geographic features create an irregular rainfall pattern over Bangladesh. The wind is normally light which varies its direction and intensity based on monsoonal circulation. The sunshine hour duration is elevated because of its position near to the equatorial belt.