23 May 2023
 | 23 May 2023
Status: this preprint is currently under review for the journal HESS.

Statistical and Machine Learning Downscaling Methods to Assess Changes to Rainfall Amounts and Frequency in Climate Change Context- CMIP 6

David Antonio Jimenez Osorio, Andrea Menapace, Ariele Zanfei, Eber José de Andrade Pinto, and Bruno Brentan

Abstract. General Circulation Models (GCMs) simulations result on grids ranging from 50 km to 600 km, and, therefore, this coarse spatial resolution requires data processing, whereby the application of downscaling techniques has become a standard procedure. The main approaches employed are Statistical DownScaling (SDS) and Dynamic DownScaling (DDS). The former SDS consists of Linear Methods (LM), Stochastic Weather Generators, and Artificial Intelligence DownScaling techniques (IADS). Being computationally less demanding and highly portable, most studies apply LM, and IADS approaches to develop the downscaling. However, it is needed to evaluate whether these approaches allow obtaining representative, in the development of rainfall frequency analysis (RFA), in the estimative of the total precipitation (TP) and the number of rainy days (RD) both water year and multiannual level, as well as identify whether any of these approaches provide better results for the last generation of GCM’s made available for CMIP 6. On this basis and considering only the models with a horizontal resolution of 100 km that participated in the SSP1-2.6 and/or SSP5-8.5 scenarios of CMIP6, the present study aim to evaluate the performance of Delta Method (DM), Quantile Mapping (QM) and Regression Trees (RT) to develop RFA, estimate the TP and RD, based on rainfall series obtained by DownScaling, respect to estimative developed with historical records. The results show that the application of DM, RT and QM does not guarantee a temporal correlation between the TP and RD estimated with DownScaling and historical series, likewise, it is observed that in the estimation of RFA, the application of RT generates better results than QM. Finally, it is evident that not applying any DownScaling technique and applying QM generates similar results.

David Antonio Jimenez Osorio et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2023-55', Kyunghun Kim, 07 Aug 2023
  • RC2: 'Comment on hess-2023-55', Anonymous Referee #2, 24 Aug 2023

David Antonio Jimenez Osorio et al.

David Antonio Jimenez Osorio et al.


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Short summary
Most studies that aim to identify the impacts of climate change employ General Circulation Models, however, due to their low spatial resolution, it is necessary to apply scale reduction techniques. In the absence of studies, this work evaluated the performance of three techniques to develop frequency analyses and to estimate both the number of rainy days and the total precipitation per water year. The result showed that the performance of the techniques varies according to the analyzed variable.