Preprints
https://doi.org/10.5194/gmd-2024-9
https://doi.org/10.5194/gmd-2024-9
Submitted as: methods for assessment of models
 | 
22 Feb 2024
Submitted as: methods for assessment of models |  | 22 Feb 2024
Status: this preprint is currently under review for the journal GMD.

Generalized drought index: A novel multi-scale daily approach for drought assessment

João Careto, Rita Cardoso, Ana Russo, Daniela Lima, and Pedro Soares

Abstract. Drought is a complex climatic phenomenon characterized by water scarcity recognized as the most widespread and insidious natural hazard, posing significant challenges to ecosystems and human society. In this study, we propose a new daily based index for characterizing droughts, which involves standardizing precipitation and/or precipitation minus potential evapotranspiration data. The performance of this new index is assessed with data from the evaluation runs of the Coordinated Regional Climate Downscaling Experiment for the European domain and the observational data from the Iberian Gridded Dataset, covering the period from 1989 to 2009. Comparative assessments are conducted against the daily Standardized Precipitation Index (SPI), the Standardized Precipitation Evapotranspiration Index (SPEI), and a simple Z-Score standardization of climatic variables. Seven different accumulation periods are considered (7, 15, 30, 90, 180, 360, and 720 days) with three drought levels: moderate, severe, and extreme. The evaluation focuses mainly on the direct comparison amongst indices, added value assessment using the Distribution Added Value and a simple bias difference for drought characteristics. Results reveal that not only does the new index allow the characterization of flash droughts, but also demonstrates added value when compared to SPI and SPEI, especially for longer accumulation periods. In comparison to the Z-Score, the new index shows slightly greater gains, particularly for extreme drought events at lower accumulation periods. Furthermore, an assessment of the spatial extent of drought for the 2004–2005 event is performed using the observational dataset. All three indices generally provide similar representations, except for the Z-Score, which exhibits limitations in capturing extreme drought events at lower accumulation periods. Overall, the findings suggest that the new index offers improved performance and adds value comparatively to similar indices with a daily time step.

João Careto, Rita Cardoso, Ana Russo, Daniela Lima, and Pedro Soares

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gmd-2024-9', Anonymous Referee #1, 25 Mar 2024
  • RC2: 'Comment on gmd-2024-9', Anonymous Referee #2, 01 Apr 2024
João Careto, Rita Cardoso, Ana Russo, Daniela Lima, and Pedro Soares
João Careto, Rita Cardoso, Ana Russo, Daniela Lima, and Pedro Soares

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Short summary
In this study, a new drought index is proposed, which not only is able to identify the same events but also can improve the results obtained from other established drought indices. The index is empirically based and is extremely straightforward to compute. It is as well, a daily drought index with the ability to not only assess flash droughts but also events at longer aggregation scales, such as the traditional monthly indices.