Assessing the impact of bias correction approaches on climate extremes and the climate change signal

We assess the impact of three bias correction approaches on present day means and extremes, and climate change signal, for six climate variables (precipitation, minimum and maximum temperature, radiation, vapour pressure and mean sea level pressure) from dynamically downscaled climate simulations over Queensland, Australia. Results show that all bias-correction methods are effective at removing systematic model biases, however the results are variable and season-dependent. Importantly, our results are based on fully independent cross-validation, an advantage over similar studies. Linear scaling preserves the climate change signals for temperature, while quantile mapping and the distribution-based transfer function modify the climate change signal and patterns of change. The Perkins score for all the values above the 95th percentile and below the 5th percentile was used to evaluate how well the climate model matches the observational data. Bias correction improved Perkins score for extremes for some variables and seasons. We rank the bias-correction methods based on the Kling-Gupta efficiency (KGE) score calculated during the validation period. We find that linear scaling and empirical quantile mapping are the best approaches for Queensland for mean climatology. On average, bias correction led to an improvement in the KGE score of 23% annually. However, in terms of extreme values, quantile mapping and statistical distribution-based transfer function approaches perform best, and linear scaling tends to perform worst. Our results show that, except linear scaling, all approaches impact the climate change signal. This paper evaluated how different bias-correction methods impact on climate extremes and the climate change signal. We rank the bias-correction methods and provide recommendations for selecting the best approaches. Our results show that most approaches impact the climate change signal, and therefore, care needs to be taken when correcting bias of downscaled simulations. image