INVESTIGATING VEGETATION-ATMOSPHERE WATER EXCHANGE BY USING HIGH FREQUENCY SPECTROSCOPY VAPOR ISOTOPE OBSERVATIONS

Abstract

In this study, we first time test the feasibility of partitioning evapotranspiration using high frequency in-situ measurements of water vapor isotopes in a paddy field, Mase, Japan. By combining isotope measurements with Keeling plot method and Craig-Gordon model, transpiration is found representing more than 90% of the total evapotranspiration flux at the daily scale. However, the errors in this method could not be neglected. The primary cause of these errors is demonstrated to be the underestimate of water evaporation estimated by Craig-Gordon model. The variation of measured water vapor d-excess is significantly affected by the dominant components of evapotranspiration on diurnal time scale, it is suggested that the vegetation play a significant role in land surface water exchange process.