Sensitivity Analysis of Potential Evapotranspiration in the Lancang River Basin
澜沧江流域潜在蒸散发敏感性分析

Sensitivity analysis is critical in assessing the impact of climatic variables on potential evapotranspiration (ET0) estimation. A sensitivity analysis of ET0 to perturbations associated with climatic variables is important to improve our understanding of the connections between climatic conditions and ET0 variability. Based on a 46-year daily observed dataset at 35 meteorological stations distributed within or in the vicinity of the Lancang River basin, ET0 was calculated for each station by the Penman-Monteith method. A non-dimensional sensitivity coefficient was employed to identify the sensitivity of ET0 to the variation of air temperature (Tmean), sunshine duration (N), relative humidity (RH), and wind speed (U2) at 3 time scales. Results indicate that the sensitivity coefficient varies greatly over space and time. For the basin as a whole, N is the most sensitive variable, increasing in January and decreasing in July over the study period. An analysis based on the long-term average level show that in general ET0 is most sensitive to N, followed by RH and Tmean. U2 was found to be the least sensitive variable in the basin in most days of a year. These coefficients also exhibit fluctuations throughout a year, especially for Tmean, with its largest value being found in July. Regarding the spatial distribution of the sensitivity coefficients in the basin in January and July, the most prominent change was a reverse distribution of high and low values in the 2 months, reflecting significant spatial differences. As for the temporal trends of the sensitivity coefficients in the basin in January and July, the most prominent change occurred in July, when the sensitivity coefficient for N decreased in most parts of the basin in the south at the Changdu station. The trend was contrary to that of the north of this station, where most stations increased. The increasing trend was also found for the regions in the south of Changdu in January. The large spatial-temporal variability of the sensitivity coefficients indicate that ET0 response to climate change differs greatly with region and season, especially for N. Results of this work can be used as a theoretical basis for future research on the response of ET0 to climatic change in the Lancang River basin.