Downscaling daily extreme temperatures with genetic programming

A context‐free genetic programming (GP) method is presented that simulated local scale daily extreme (maximum and minimum) temperatures based on large scale atmospheric variables. The method evolves simple and optimal models for downscaling daily temperature at a station. The advantage of the context‐free GP method is that both the variables and constants of the candidate models are optimized and consequently the selection of the optimal model. The method is applied to the Chute‐du‐Diable weather station in Northeastern Canada along with the National Center for Environmental Prediction (NCEP) reanalysis datasets. The performance of the GP based downscaling models is compared to benchmarks from a commonly used statistical downscaling model. The experiment results show that the models evolved by the GP are simpler and more efficient for downscaling daily extreme temperature than the common statistical method. The different model test results indicate that the GP approach significantly outperforms the statistical method for the downscaling of daily minimum temperature, while for the maximum temperature the two methods are almost equivalent. However, the GP method remains slightly more effective for maximum temperature downscaling than the statistical method.