Study Of Flux Data On Semi-arid Grassland

With the core of eddy covariance, taking advantages of turbulence observation to investigate the interaction between soil-grassland-atmosphere, the effect of human activity, as well as the carbon and water cycle of grassland ecosystem is significant. Xilinhot grassland is typical of the grassland ecosystem of semi-arid in North China. Soil-atmosphere exchanges of semi-arid grassland have great effects on the evolution of the ecological environment and regional climate change in Inner Mongolia grassland region. Therefore, further study of Inner Mongolia semi-arid grassland soil-atmosphere flux exchanges is necessary. Based on the turbulence data observed by the eddy covariance system at Xilinhot National Climate Observatory in2010, this paper analyzes several methods of turbulence data quality control and assessment, and the local flux characteristics, finally discusses the energy balance of the local situation. The main conclusions are as follows:(1)After the data correction and inspection, the test results show that most of the sampled data quality in2010are good, can satisfy the requirement of the steady state test, which means the turbulences are fully developed.(2) The diurnal variation of CO2flux show nightly positive and daily negative, the variable characteristics present a u-shaped curve and the values in growing season are larger than those in non-growing season. The sensible heat and latent heat fluxes exhibit quadratic curve within a day, and the sensible heat flux is greater than the latent heat flux; in order of most to least, the values of sensible heat flux in different seasons go to summer> autumn> spring> winter, while latent heat flux go to summer> spring> autumn> winter.(3)The albedo of Xilinhot grassland in the morning and evening are large than those in noon which show a u-shaped trend. Because of the snow cover, albedo from January to March, November to December are larger than those from April to October. The Global Radiation and each component all have obvious diurnal and annual variation characteristics. In general, low in the morning and evening, high at noon; low in winter, and high in summer; different seasons and different components have different orders. On sunny day, each radiation component has obvious characteristics, show a change curve with the shape of "Ω";while on cloudy day, under the influence of clouds, radiation component change is complex.(4) The soil heat flux in a day present single-peak quadric curve changes, and in growing season, the values are greater than those in non-growing season. Soil heat flux is driven by solar radiation, for the day, net radiation flux>sensible heat flux> latent heat flux>; for the night, net radiation flux> sensible heat flux> soil heat flux> latent heat flux. Heat flux is larger in summer (or growing season), smaller in winter (or non-growing season). The total energy balance closure of Xilinhot semi-arid grassland is0.747, the growing season is0.789, while the non-growing season is0.571.