Seasonal variation of evapotranspiration and its effect on the surface energy budget closure at a tropical forest over north-east India

This study uses one year of eddy covariance flux observations to investigate seasonal variations in evapotranspiration and surface energy budget closure at a tropical semi-deciduous forest located in north east India. The annual cycle is divided into four seasons, namely: pre-monsoon, monsoon, post-monsoon, and winter. The highest energy balance closure (76%) is observed during pre-monsoon, whereas the lowest level of closure (62%) is observed during winter. Intermediate closure of 68% and 72% is observed during monsoon and post-monsoon seasons, respectively. Maximum latent heat flux during winter (150 W m-2) is half of the maximum latent heat (300 W m-2) flux during monsoon. Evapotranspiration is a controlling factor of surface energy budget closure, with highest rates of closure corresponding to the periods of highest evapotranspiration. The Bowen ratio ranges from 0.93 in winter to 0.27 during monsoon. This is the first time the role of evapotranspiration in the seasonal variation of surface energy budget closure has been reported for any ecosystem in north-east India using eddy covariance measurements.