Sensitivity of the reference evapotranspiration to key climatic variables in Shandong Province, China

摘要

The aim of this work was to predict responses of reference evapotranspiration (ET_o) to perturbations of four climatic variables in Shandong province, China. For this purpose, ET_o was estimated based on the FAO-56 Penman-Monteith equation and the non-dimensional relative sensitivity coefficient was employed. Climatic variables (i.e., daily air temperature, sunshine duration, wind speed and daily relative humidity) at 12 meteorological stations covering whole area (1960 to 2013) were collected firstly and used for the analysis. Results showed that ET_o had positive sensitivities to air temperature, sunshine duration and wind speed, opposite to what were observed to relative humidity. The sensitivity of climatic parameters to ET_o showed a decreasing trend: relative humidity ＞ sunshine duration ＞ wind speed ＞ air temperature. The sensitivity coefficients of different factors varied in time and space. From 1960 to 2013, the sensitivity coefficient of sunshine duration (S_n) showed a downward trend at a rate of (-4.3e-4) per annum. The sensitivity coefficient of wind speed (Sws) and relative humidity (S_(RH)) increased at a rate of (3.9e-4) per annum and (1.9e-3) per annum respectively, while the sensitivity coefficient of air temperature (S_T) waved with a tiny decrease trend. The values of S_T and S_n in southern were larger than in northern region. The values of S_(WS) in southern and northeast region were smaller than that in the northern area. Srh in the central region was lower than other area, opposite to what were observed in coastal areas.