中文摘要：

风蚀输沙起动条件与输沙率预测是风蚀预报、沙尘数值预报与风沙地貌演化以及防沙治沙工程研究所需的关键参数，因而一直是风沙物理学研究的重点课题。早期的研究主要关注稳态输沙过程，对野外实际输沙过程的预测存在相当大的误差。近年高频的实时同步输沙、风速测量显示：大气边界层近地表风速脉动强烈，因而导致野外实际输沙具有高度的时空变化。研究发现：风沙输运的非平常性与边界层湍流结构密切相关，因而会对沙粒起动条件判断、输沙率预测等产生影响。回顾了近20年中非平稳输沙研究在实验、理论以及数值模拟方面的进展，并提出了目前存在的问题和今后发展的趋势。

英文摘要：

The threshold condition and mass flux of aeolian sediment transport are the essential quantities for wind erosion prediction, dust storm modeling and geomorphologieal evolution, as well as the sand control engineering design. As a consequence, they have long been the key issues of windblown sand physics. Early researches on aeolian sediment transport focus mainly on steady transport process. While recently, synchronous, high frequency measurements show that wind field in atmospheric boundary layer is always unsteady, showing up as intense fluctuation of wind speed, which thus results in the intense spatial-temporal variability of aeolian sand transport. It has been proven that unsteady sand/dust transport is closely related with boundary layer turbulence and affects significantly the determination of threshold condition and the prediction of aeolian transport rate. The researches of experiment, theory analysis and numerical simulation on unsteady sand/dust transport in recent two decades are reviewed. Finally, open questions and future developments are suggested.