Abstract: vegetation diversity and climate variability are significant in the meadow ecosystem. Energy balance is important to study the ecological effect in the meadow ecosystem. Based on the observational data from the eddy covariance and conventionally meteorological data, the energy balance characteristics during the growth season of 2010 in Horqin meadow were analyzed by methods of a least squares and a linear regression. The results indicate that the energy balance closure rate of meadow during the growth season is 80.4%, and it means that there is an unclosed phenomenon in the study area. At the same time, the closure rate exceeds the average in similar observational sites, so it can conclude that the observational data from the eddy covariance flux measurements are reliable. The diurnal albedo decreases firstly then increases and the minimum value appears at noon; the albedo value fluctuates between 0.040 and 0.120 during the growth season and average is 0.061. In general, it also decreases firstly and then increases. The ratio between net radiation (Rn) and solar radiation (Q) is 0.386, and both are positively linear correlated. Latent heat flux is the main energy expenditure in Horqin meadow, and follows by sensible heat flux. Daily variations of energy balance components and net radiation are same with a single peak; their values increase after sunrise and decrease after reaching the maximum at noon; both peak values and their appearing time are different slightly. The order of ratios that each component account for net radiation under two typical weather conditions is the same with that of averages during the growing season. The variation trends of each component and net radiation are same with a single peak on sunny day, while those are not significant on cloudy day.

Key words: Meadow, Growth season, Eddy covariance, Energy balance, Closure