Abstract: Based on the 2019 eddy covariance observations and meteorological observation data, the characteristics of the variation in energy balance and evapotranspiration of the sparse shrub ecosystem in the northeastern edge of Ulan Buh Desert were studied, and its energy closure and distribution were analyzed. The total net radiation during the observation period was 2 758 MJ·m^-2, and the diurnal variation of the net radiation showed a single-peak type quadratic curve with obvious seasonal variation characteristics. Each energy component showed changes similar to the net radiation, and the absolute value of each item showed the following order: net radiation > sensible heat flux > soil heat flux > latent heat flux. The sum of soil heat flux was positive, indicating that the soil is a heat sink. The turbulent flux was dominated by sensible heat, which accounted for 62% of net radiation, 4% of latent heat, and 1% of soil heat flux during the observation period. The energy balance closure in the study area was not achieved. The energy closures of the half-hour period and daily average flux calculated by the least square method were 64% and 67%, respectively. The energy balance ratio ranged from 0.54 to 0.73, and the energy closure was 65% during the day and 20% at night. The total evapotranspiration during the observation period was 85.6 mm, which was larger than the total amount of precipitation (79.6 mm). The daily average evapotranspiration intensity was 0.36 mm·d^-1. The evapotranspiration changed significantly with the plant growth in different periods, and the monthly cumulative evapotranspiration reached the peak in July.

Key words: Ulan Buh Desert, eddy covariance, energy balance, evapotranspiration, energy closure