Mahsa Sameti; NOZAR GHAHREMAN; Khalil Ghorbani
Abstract
The capability of M5 model tree in estimating reference evapotranspiration in two stations, namely, Shiraz and Kermanshah, was studied. The daily weather data including mean air temperature, sunshine hours, precipitation, dew point temperature, mean relative humidity, wind speed and actual vapor pressure ...
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The capability of M5 model tree in estimating reference evapotranspiration in two stations, namely, Shiraz and Kermanshah, was studied. The daily weather data including mean air temperature, sunshine hours, precipitation, dew point temperature, mean relative humidity, wind speed and actual vapor pressure were collected and used as input variables for daily estimation of potential evapotranspiration by Penman-Montieth and Hargreaves-Samani equations. As the main goal of this study, the performance of M5 model tree in predicting reference evapotranspiration was evaluated. The results showed that the skill of M5 model in predicting ET by both methods was high but its performance in predicting Penman-Montieth values was relatively more, with R2 of 0.975 and 0.973 and RMSE values of 0.346 and 0.361 for Shiraz and Kermanshah, respectively, while the corresponding values for Hargreaves-Samani equation were Shiraz:R2=0.837, RMSE=0.844, and Kermanshah:R2=0.979, RMSE= 0.774. Sensitivity analysis revealed that the most significant variables in Penman-Montieth equation in Shiraz station were, respectively, air temperature, dew point, sunshine hours, and wind, while in Kermanshah station, important factors were air temperature, sunshine hours, wind, relative humidity, and dew point, respectively. Further studies are recommended in other climates for more scrutiny.
NOZAR GHAHREMAN; Azar Sahragard
Abstract
Leaf Wetness Duration (LWD) is a key element in plant water balance. Water wets leaf surfaces following various events such as rainfall, dew formation, etc. The result of the interaction between atmosphere and the plant leaf and canopy characteristics determine the leaves wetness duration (LWD) on the ...
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Leaf Wetness Duration (LWD) is a key element in plant water balance. Water wets leaf surfaces following various events such as rainfall, dew formation, etc. The result of the interaction between atmosphere and the plant leaf and canopy characteristics determine the leaves wetness duration (LWD) on the plant. This variable is measured by electronic sensors, but, due to the difficulty of measurement, various empirical models using meteorological data have been developed for its estimation. Despite their limitations, these models are widely used. In this study, two empirical models of LWD estimation using relative humidity were evaluated at Paliz station in Fars province. The simplest empirical model uses only the relative humidity (RH), and wetness occurs when the RH is greater than a certain threshold. On the basis of different studies under wet conditions, for several plants, a threshold value of 87% RH has been determined for this purpose. In this study, the optimized RH-threshold model did a better job compared to non-optimized constant threshold and the extended threshold models in both warm and cold seasons.