Abstract: The blowouts at different development stages in the northern sandy zone of the Hulunbuir sandy grasslands were selected to analyze and compare the structure of drifting sand flow based on the simultaneous observation of wind-sand flux over blowout surface (0-200 cm). The purpose of the study was to provide a theoretical basis for wind erosion control in sandy grasslands. The results showed that the wind profiles were in a logarithmic distribution in the sand patches at their different development stages, while the un-eroded grasslands and the blowouts at their extinction stage were in an “S-shaped” distribution because the air flow was disturbed by the underlying surface. The optimal fitting model for sand flux and height over blowout at each development stage was a negative exponential model, and the difference of sand flux in blowout at different development stages was obvious. More than 95% sand flux was distributed within a height of 0-30 cm from the land surface, and 63.97%-90.96% sand flux was distributed in 10 cm height. The sand saltation height was positively correlated with wind speed and in an order of active development>reactivation stage>sand patch>fixed stage>extinction stage>un-eroded grassland. The analyzed results of sand flux coefficient revealed that the high value of sand flux moved upwards over sand patch at the active development and reactivation stages, and the wind-blown sand flux concentrated near ground because of the high vegetation coverage.

Key words: structure of drifting sand flow, sand flux, blowout, sandy grassland, Hulun Buir