Selection of an Ensemble of Atmospheric and Oceanic General Circulation Models of the CMIP-6 Project for estimating possible runoff changes in the Volga and Kama basins

Abstract

In modern conditions of climate change and increasing pressure on water resources, river forecasting is becoming one of the urgent tasks of rational water use. The main tool for long-term climate characteristics prediction are the Atmospheric and Oceanic General Circulation Models (AOGCM). In this paper, we assessed the quality of a number of climatic characteristics by the CMIP-6 (Coupled Model Intercomparison Project, Phase 6) AOGCMs for the Volga and Kama basins in order to access the possibility of their use to river runoff in the 21st century forecasting. A comparison was made of the data produced by the models for the period 1985-2014 and ERA5 reanalysis data (temperature and precipitation) as well as with observational data on river runoff. The reproduction error of the average values, standard deviations, and the coincidence of series trends evaluated. It is shown that the models demonstrate very different quality of the reproduction of water balance characteristics results. When using these models to predict possible changes in river flow in the future, it is necessary to take into account these uncertainties and apply methods to reduce the impact of systematic errors.