Performance of equations to estimate the hourly actual vapor pressure


  • Aline Aparecida dos Santos
  • Jorge Luiz Moretti de Souza
  • Stefanie Lais Kreutz Rosa


The objective of the present study was to analyze the performance of equations to estimate the hourly actual vapor pressure (ea) in the regions of Paraná State, Southern Brazil, and in the main Brazilian climate types. Four equations were tested, being considered the equation that uses the relative humidity (RH) as standard. Hourly data series from automatic meteorological stations of the Brazilian National Institute of Meteorology (INMET) were used in the analyses, being 25 from the Paraná State (data measured between December 1, 2016 and November 8, 2018) and 8 representing the main Brazilians climate types (Af, Am, Aw, Bsh, Cfa, Cfb, Cwa and Cwb; data measured between December 12, 2018 and December 11, 2019). The association between standard and alternative equations was verified using linear regression analysis, correlation coefficient (r), index of agreement (d) and root mean square error (RMSE). The alternative equations did not differ from the standard equation in the locations of Paraná State (d = 1.0 and r = 1.0; RMSE ≤ 0.02 kPa) and Brazilian climate types (d = 1.0; r ≥ 0.99; RMSE ≤ 0.02 kPa). The equation to be used must be made considering the quality and availability of the necessary input data in each equation. 






I-Land and Water Engineering