Abstract
This study investigated the convective velocity of ponding water in a vegetated paddy lysimeter. We im-proved the measurement method for convective velocity by reducing the heat to the constantan line of the sensor. Then, to clarify the causes of ponding water convection in the vegetated paddy lysimeter, we conducted a model exper-iment under conditions of inhibited evaporation and with similar water temperature profiles to those in the vegetated paddy lysimeter. In the vegetated paddy lysimeter, the con-vective velocity of ponding water increased from 0.1 to 0.6 mm s−1 between 7:00 and 17:00, an increase that was re-lated to air-water vapor pressure differences. In the model experiment, the convective velocity remained constant at approximately 0.6 mm s−1 and 0.2 mm s−1 during night and day, respectively. In addition, less heat was lost by air-water temperature differences during the day than at night. These results suggest that evaporative heat loss induces the convection of ponding water in a vegetated paddy lysime-ter.
