Assessment of characteristic changes of regional estimation of extreme rainfall under climate change: A case study in a tropical monsoon region with the climate projections from CMIP6 model

Climate change is perceived to be the main reason in affecting global rainfall patterns. The estimation of rainfall extremes based on historical data, hence, might undervalue the risk related to the design of water infrastructure system. Bangladesh, a tropical monsoon region, is highly vulnerable to climate change; however, little is investigated in the changes of extreme rainfall under climate change. Also, the impact of climate change on the behavioural changes of regional estimate of extreme estimation is understudied. The goal of this study is to examine the characteristic changes of regional estimate of extreme rainfall at the daily time scale under the backdrop of climate change in Bangladesh. The multi-model ensemble method consists of several global climate models (CMIP6 GCMs) and two emission scenarios were employed to assess the effect of climate change in two time horizons: 2021-2060 and 2061-2100. The regional index-flood approach comprised of index value and growth curve (estimated using generalized extreme value, GEV, distribution) was used to quantify the return period values of extreme rainfall. The above approach was applied to observed as well as simulated rainfall data to quantify the changes in extreme quantiles. There is a significant increase of index value under climate change. There is a tendency to have a higher estimate of index value in the far future than the immediate future. The higher estimate is also detected under the higher emission scenario compared to the medium emission scenario. The changes in growth curves are region specific and do not follow the same characteristics as the index value. A similar behaviour of shape of GEV is noticed at present and future conditions. Overall, an increased value of about 22% in 100-year return level is expected by the end of this century under the changing conditions of climate.

Automated summary

This study focuses on exploring the characteristic changes of extreme rainfall estimation at the daily time scale in Bangladesh under the background of climate change. The results indicate a significant increase in index value under climate change, with about a 22% increase in the 100-year return level of extreme rainfall expected by the end of this century.