Impact of the Mean Daily Air Temperature Calculation on the Rainfall-Runoff Modelling

Abstract

Conceptual rainfall-runoff models besides precipitation and discharge data generally require estimates of the mean daily air temperature as input data. For the estimation of the mean daily air temperature, there are different methods available. The paper presents an evaluation of the impact of the mean daily air temperature calculation on the rainfall-runoff modelling results. Additionally, other measured variables and rating curve uncertainty were assessed. Differences in the mean daily air temperature values were evaluated for the 33 meteorological stations in Slovenia and additional investigations were conducted for four selected meso-scale catchments located in different climates. The results of the application of four equations for the mean air temperature calculation yielded the mean absolute error values between 0.56–0.80 °C. However, the results of rainfall-runoff modelling showed that these differences had an almost negligible impact on the model results. Differences in the mean simulated discharge values were no larger than 1%, while differences in the maximum discharge values were a bit larger, but did not exceed 5%. A somewhat larger impact on the model results was observed when precipitation and water level measurements’ uncertainty was included. However, among all analysed input data uncertainties, the rating curve uncertainty can be regarded as the most influential with differences in the simulated mean discharge values in the range of 3% and differences in the maximum discharge values up to 14%.

Climate Variability and Trends in Imotski, Croatia: An Analysis of Temperature and Precipitation

“…The mean annual temperature is the average of the mean monthly temperatures, while the mean monthly temperatures are the average of the mean daily temperatures. The mean daily temperature is calculated according to the expression [31][32][33][34][35] used in some central and eastern European countries (e.g., Croatia, Slovenia, Serbia) as follows:…”

“…where T 7 , T 14 , and T 21 are temperatures measured at 7, 14, and 21 h (local time). The equation in use today is over a century old and was formulated based on the assumptions and understanding of that time [32,36]. Daily minimum and maximum temperatures are read using minimum and maximum thermometers in the meteorological station at 2 m above the ground.…”