Analysis of the onset, withdrawal, and variability of monsoon rainfall in the face of climate change

Climate change is affecting the precipitation system in Bangladesh, particularly in the northwestern hydrological zone. This study analyzed the monsoon rainfall variability from 1991 to 2015, revealing a shifting pattern and past trends. This study used the Mann–Kendall test and Sen’s slope (MAKESENS) statistical model to evaluate the annual total rainfall and monsoon rainfall. Approximately 71–78% of the total rainfall occurred during the monsoon season at all stations, with Rangpur being the rainiest and Rajshahi being the driest. The annual rainfall trend decreased, with highly variable arrival and withdrawal days. The monsoon arrived early by 2 to 39 days and late by 1 to 72 days from the reference day. The withdrawal of monsoon rainfall occurred 1 to 38 days early and 1 to 39 days late. These findings can be used to plan and manage agricultural practices at the local level in northwestern Bangladesh.