Abstract: Priestley-Taylor method is developed under the condition of non advection water vapour transport, however, this assumption is hardly satisfied in reality. Some researches introduced the parameter in order to eliminate the error brought by the non-advection assumption. According to many researches, the value of parameter has some uncertainty. This paper tries to introduce an advection coefficient to reflect the influence of advection on evaporation. The case analyses suggest that this method could provide the minimum energy for calculating evaporation in winter. Compared with the original formula, the calculation accuracy of evaporation has been effectively improved, especially in winter and summer.

Key words: advection constant coefficient, complementary relationship model, Priestley-Taylor method, regional evapotranspiration, Wujiang River basin