Evaluation of the CMIP5 general circulation models for simulating the precipitation and temperature of the Koshi River Basin in Nepal

Pragya Pradhan,Sangam Shrestha,S Mohana Sundaram,Salvatore G P Virdis

doi:10.2166/wcc.2021.124

Pragya Pradhan, Sangam Shrestha + Show 2 more

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https://doi.org/10.2166/wcc.2021.124

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Abstract

AbstractThis study evaluates the performance of 12 different general circulation models (GCMs) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to simulate precipitation and temperature in the Koshi River Basin, Nepal. Four statistical performance indicators: correlation coefficient, normalised root-mean-square deviation (NMRSD), absolute NMRSD, and average absolute relative deviation are considered to evaluate the GCMs using historical observations. Seven different climate indices: consecutive dry days, consecutive wet days, cold spell duration index, warm spell duration index, frost days, very wet days, and simple daily intensity index are considered to identify the most suitable models for the basin and future climate impact assessment studies. Weights for each performance indicator are determined using the entropy method, with compromise programming applied to rank the GCMs based on the Euclidian distant technique. The results suggest that CanESM2 and CSIRO-MK3.6.0 are the most suitable for predicting extreme precipitation events, and BCC-CSM 1.1, CanESM2, NorESM1-M, and CNRM-CM5 for extreme temperature events in Himalayan river basins. Overall, IPSL-CM5A-MR, CanESM2, CNRM-CM5, BCC-CSM 1.1, NorESM1-M, and CSIRO-Mk3.6.0 are deemed suitable models for predicting precipitation and temperature in the Koshi River Basin, Nepal.

Highlights

Climate change is a key driver of sustainability in the Himalayan region (Wester et al 2019)
Climate change impact studies on Himalayan river basins are carried out using different climate models such as general circulation models (GCMs) and regional climate models (RCMs) (Lutz et al 2016; Rajbhandari et al 2016)
The Koshi River Basin is highly influenced by the wet season (May–September), the 80% of the total annual rainfall falls in the wet season (Table 4)

Summary

Introduction

Climate change is a key driver of sustainability in the Himalayan region (Wester et al 2019). The mountains of the Himalayan region play a vital role in the regulation and distribution of water resources and contain the headwaters of 10 major river systems: the Amu Darya, Brahmaputra, Ganges, Indus, Irrawaddy, Mekong, Salween, Tarim, Yangtze, and Yellow, which provide services to 1.3 billion people downstream (Eriksson et al 2009). The snow and ice stored in the headwater regions of these major rivers sustain seasonal water availability in the downstream areas through snowmelt runoff (Immerzeel et al 2009; Nepal et al 2014). There is snowmelt as well as changes in precipitation and temperature, potentially affecting the hydrology of headwater basins in the Himalayan region. The selection and identification of climate models for Himalayan river basins, which represent both the existing and future

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