| dc.description.abstract | Abstract
This study developed a vertically integrated hydrological and meteorological real-time monitoring system to investigate the evapotranspiration (ET) of land processes. The multisensor capacitance probe was applied to measure the variation of soil water content for determining the loss of soil water accounting for ET over dry days. The results were compared with other micro-meteorological methods, including the Penman-Monteith equation, the Priestley-Taylor equation, the Bowen ratio method, and the vapor gradient method, for estimating ET or potential ET. The discussions were presented in two parts, the first one used daily average data to analyze the daily ET variations; the second part used ten-minute resolution data to analyze the diurnal ET variation associated with the micro meteorological factors.
The results of the daily analyses were given as the following. Under wet soil conditions, the amounts of ETs estimated by the Penman-Monteith equation, the Priestley-Taylor equation, and the Bowen ratio method showed the similar values with the measured loss of soil water. Under dry soil conditions, the ratios of the estimated ETs to the measured soil-water losses associated with the surface soil water content were found to have an exponential relation. With this exponential relation, the differences between the estimated ET and the water loss can be reduced. Among all methods compared in this study, the Penman-Monteith equation is the best one to estimate ET and the only draw back is the requirement of numerous meteorological data. The vapor gradient method were found to be disappointed on estimating daily ET in this study
The results of the short-time diurnal analyses are presented as below. Under wet soil conditions, the amounts of ETs estimated by the Penman-Monteith equation were most close to the measured loss of soil water. The Priestley-Taylor equation only includes the available energy and is unable to capture the influences of other meteorological variances on ET. The ETs estimated by the Bowen ratio method is oscillated due to the intrinsic unstable approach, so it is unsuitable for estimates ET using high temporal resolution data. | en_US |