Abstract:

In order to analyze potential evapotranspiration in the past 55 years for trend of its variation and validate whether and how "evaporation paradox" existed in Jiangxi Province, monthly meteorological data of the years of 1957-2011 were gathered from 15 national-level meteorological observatories in Jiangxi Province. On such a basis, potential evapotranspiration (E_T0) was calculated with the Penman-Monteith formula for analysis of spatio-temporal variation rule of E_T0 with the spatial interpolation and data mining technology, partial derivatives of each variable of the Penman-Monteith formula derived, and causes of the E_T0 variation and their sensitivities to each variable quantitated with the help of total differential and partial derivative coefficient of each variable. Results show that since 1970 annual mean E_T0 in Jiangxi Province had been declining significantly, while temperature there rising remarkably, thus forming obvious "evaporation paradox". Mean potential evaporation of a year, the flood season and the non-flood season was 0.20, 0.10 and 0.31 mm·d^-1, respectively, lower in the years after 1970 than in the years before that. Especially the decrease in sunshine hour and mean wind velocity caused the three indices to fall by 0.19 and 0.04, 0.25 and 0.04, 0.25 and 0.04 mm·d^-1, respectively. Meanwhile, the partial derivative of E_T0 was the biggest to sunshine hour and mean wind velocity. Analysis in the study demonstrates that the rules of variation of E_T0 and temperature in Jiangxi Province was mainly determined by duration of sunshine hour and mean wind velocity.

Key words: evaporation power, evaporation paradox, sensitivity analysis, Penman-Monteith formula