Downscaling GCM data for climate change impact assessments on rainfall: a practical application for the Brahmani-Baitarani river basin

Abstract

The delta of the Brahmani-Baitarani river basin, located in the eastern part of India, frequently experiences severe floods. For flood risk analysis and water system design, insights in the possible future changes in extreme rainfall events caused by climate change are of major importance. There is a wide range of statistical and dynamical 5 downscaling and bias-correction methods available to generate local climate projections that also consider changes in rainfall extremes. Yet the applicability of these methods highly depends on availability of meteorological observations at local level. In the developing countries data and model availability may be limited, either due to the lack of actual existence of these data or because political data sensitivity hampers 10 open sharing.We here present the climate change analysis we performed for the BrahmaniBaitarani river basin focusing on changes in four selected indices for rainfall extremes using data from three performance-based selected GCMs that are part of the 5th Coupled Model Intercomparison Project (CMIP5). We apply and compare two widely used 15 and easy to implement bias correction approaches. These methods were selected as best suited due to the absence of reliable long historic meteorological data. We present the main changes -likely increases in monsoon rainfall especially in the Mountainous regions and a likely increase of the number of heavy rain days. In addition, we discuss the gap between state-of-the-art downscaling techniques and the actual options one is 20 faced with in local scale climate change assessments.

Spatiotemporal characteristics of future changes in precipitation and temperature in Central Asia

“…The Delta and BMA downscaling methods are common statistical downscaling techniques that have been widely used in the GCM ensemble (Onyutha et al, ; Yang et al, ). By assuming that the relative changes observed from GCMs are more representative than the absolute ones, the Delta downscaling method accounts for climatic changes by the perturbations from a multi‐model median (Dahm et al, ; Onyutha et al, ). All the GCMs participated in the downscaling process equally.…”

Assessment of future flood inundations under climate and land use change scenarios in the Ciliwung River Basin, Jakarta

“…Wu et al () analysed the impact of climate change on floods in the Beijiang River Basin, China using CMIP5 GCM data. Dahm et al () used HadGEM2‐ES and MIROC‐ESM, GFDL‐CM3 of the CMIP5 for the Brahmani‐Baitarani River Basin in India, and focused on changes in the four selected indices for precipitation extremes. GCM outputs are not suitable for direct use in a climate change impact assessment at the local/basin level (Christensen et al ., ; Sunyer et al ., ), and downscaling enhances the GCM outputs and increases their suitability for local/basin scale climate change impact assessments.…”

Spatially-explicit simulation of two-way coupling of complex socio-environmental systems: Socio-hydrological risk and decision making in Mexico City

“…The impact of urban growth on watershed runoff was simulated by loosely linking SLEUTH, a cellular automata urban sprawl model (Clarke et al, 1997), with SWAT-SCS-CN, a water balance model that relates runoff to land cover type, soil condition, daily precipitation, and evapotranspiration inputs (SCS, 1972). Climate change effects on precipitation and evapotranspiration were modeled using the delta change method, which transformed available historical observations into future projections (Dahm, 2016).…”