Open loop system of eddy covariance method and conventional micro-meteorological system were employed in the study for the long-term positioning observation to investigate the energy budget,surface-atmosphere water vapor exchange process and the relationship with meteorological factors in the Horqin Sandy Land,a semiarid area.The primary objective was to compare and analyze the flux data of both sandy dune and meadow area.The results showed that the net radiation on four typical sunny days was low in the morning and evening,it reached the peak value around noon,and its curve was “parabola-shaped”.The average maximum appeared during the period of 14:00-16:00 pm at all sites in winter,spring,summer and fall.The latent heat flux over meadow was significantly higher than that on sand dune,and even it reached 4 times in spring and autumn.During crop growth season (in August),the accumulated latent heat flux reached the highest value in a year,and the extreme value of meadow area was basically equal with that of sand dune.In January,the latent heat flux difference between two sites tended to be smaller and fluctuated in a certain range.In general,the sensible heat flux over a meadow was lower than that over a dune.One thing to be concerned was that the negative sensible heat appeared after 18:00 and 17:00 pm in spring and summer over meadow site,respectively.In sunny days of winter,spring and summer,the starting and ending time when the different value between the meadow and sandy land was significant became earlier,but that in autumn was postponed.The source area was changed with the change of wind directions,the higher the proportion of wind frequency was,the longer the contribution distance of source area would be.There was a negative correlation between evapotranspiration of the two underlying surfaces and precipitation,the evapotranspiration values of the two underlying surfaces after rain were 14% and 40% lower than those on sunny day respectively,the daily evapotranspiration was regularly changed with wind speed fluctuation on sunny day,but the high wind speed was unfavorable for evapotranspiration of meadow.
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