Index-Based Study of Future Precipitation Changes over Subansiri River Catchment under Changing Climate

Abstract

This study focuses on the long-term (2011-2100) changes in precipitation indices under different climate change scenarios in Subansiri river basin, a tributary of Brahmaputra River in Northeast India. The fifth phase coupled model intercomparison project (CMIP5) data for different representative concentration pathways (RCPs) scenarios as suggested by Intergovernmental Panel on Climate Change (IPCC) is used for the study. Statistical downscaling model (SDSM) is used to downscale the precipitation. Three global climate model (GCM) datasets from earth system model and geophysical fluid dynamics laboratory (namely ESM2G, ESM2M, and GFDL-CM3) with four RCP scenarios (namely RCP2.6, RCP4.5, RCP6.0, and RCP8.5) were used for generating daily precipitation time series for a time period of 2011 to 2100. Precipitation based indices were computed on a multi-decadal time scale to detect the changes in precipitation pattern and its distribution. Total five precipitation stations were selected for downscaling and precipitation indices analysis. The non-parametric Mann-Kendall test method was used for the trend analysis of the precipitation indices. Indices based analysis of the precipitation shows an increase in the intensity of precipitation whereas a decrease in number of precipitation days on the lower part of the basin. The increase in number of rainy days followed by a decrease in intensity in the upper station was observed. Long-term (2011-2100) future projection of precipitation for annual precipitation shows statistically significant increase of minimum 1.8% at station 1 (for RCP2.6) to maximum 11% in station 3 (for RCP8.5) as compared to observed period annual precipitation.

Keywords: downscaling, CMIP5, RCP, precipitation indices, trend analysis, Subansiri river