Development of a supersonic pan-evaporimeter for dynamic analysis of evaporative demand in a greenhouse

抄録

A supersonic pan-evaporimeter was developed for performing dynamic analysis of evaporative demand in a greenhouse. The pan-evaporimeter comprises two parts: a small-sized cylindrical container (a diameter of 27 cm, a height of 15 cm) filled with water and a supersonic water-level detector. The pan evaporation rate (E_pan) can be evaluated for an arbitrary time interval on the basis of the decrease in the water level due to evaporation from the pan-evaporimeter. The performance and validity of the panevaporimeter were examined by analyzing the characteristics of E_pan on an hourly basis and its relation with the solar radiation, air temperature and humidity, wind speed, in addition, the transpiration rate of a tomato plant (Tr) in a greenhouse. A positive linear relationship was clearly obtained between the hourly E_pan and the environmental elements, and then sensitivity of E_pan to the environmental elements was revealed. Furthermore, a good correlation was found between the E_pan and the Tr on hourly basis for one day. These results suggest that the developed pan-evaporimeter is a useful tool for analyzing the dynamics of evaporative demand and for estimating the transpiration rate in a greenhouse.