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

Abstract

The study of rainfall variability is important to reveal the detailed characteristics of the precipitation system under climate change. The variation in monsoon rainfall during 1991–2015 in the northwestern hydrological zone in Bangladesh, which includes the Bogura, Rangpur, Dinajpur, Rajshahi, and Pabna meteorological stations, was analyzed to examine the past trend, arrival, and withdrawal pattern, and shifting of monsoon rainfall. The annual total rainfall and monsoon rainfall were analyzed to evaluate their trend using a statistical model called MAKESENS. Approximately 71–78% of the total rainfall occurred during the monsoon season at all stations. Rangpur was the rainiest station (2193 mm/year) and Rajshahi was the driest station (1394 mm/year). There was a decreasing trend of annual rainfall at most of the stations. The arrival and withdrawal days of the monsoon rainfall at all stations were highly variable; the arrival day varied between 1 May and 23 August, and the withdrawal day varied between 19 August and 27 October. The monsoon arrived early by 2 to 39 days and late by 1 to 72 days from the reference day (1 May). The withdrawal of monsoon rainfall occurred 1 to 38 days early and 1 to 39 days late from the reference day. The shifting of the monsoon did not reveal any significant pattern. The results of this study can be used to plan and manage agricultural practices at the local level of the northwestern Bangladesh.