Revisiting the statistical method for estimating the Probable Maximum Precipitation (PMP): from theoretical concepts to a satellite-based spatial approach in the state of Minas Gerais

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Abstract
Probable Maximum Precipitation (PMP) estimates have recently become a legal requirement for the design of high-hazard hydraulic structures in Brazil. However, the distinctions between the PMP concept and the available estimation models are not well understood by researchers and practitioners, causing confusion on what PMP estimates actually mean and a lack of comprehension about the inherent but implicitly neglected risk. In this paper, we revisit the statistical method proposed by Hershfield (1961, 1965), discussing theoretical aspects and modeling assumptions for highlighting its conceptual incompatibility with physical upper bounds for rainfall amounts. We also derive a new envelope curve for frequency factors for the Brazilian territory and apply it for constructing a satellite-based spatialized daily PMP map in Minas Gerais (MG). Results suggest the original method provides an unrealistic envelope curve for maximum frequency factors and indicate much lower values in Brazil. Moreover, the bias correction procedure of satellite retrievals proved effective in reproducing site-specific daily rainfall characteristics in MG. Despite the method’s theoretical inconsistencies, our approach provides a more realistic appraisal of statistical PMP estimates for supporting decision-making in the country.
Funding Information
  • Conselho Nacional de Desenvolvimento Científico e Tecnológico
  • Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
  • Fundação de Amparo à Pesquisa do Estado de Minas Gerais

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