关键词: 科尔沁沙地, 横向沙丘群, 丘间走廊, 次生气流, 气流偏转

Abstract: In accordance with the classic theory of blown sand physics, horizontal roll vortex with transverse axis in the lee side of transverse dune could be expected because of flow separation. However, very stable S and SW winds can be frequently perceived and observed in interdune corridors (IDCs) under the circumstances of prevailing winds (NW) by means of field expeditions and observations in more dunefields in many years conducted in the Korqin Sandy Land, Northeast China, rather than imagined reverse flows in near surface boundary layers. In order to make sure the characteristics of the odd secondary flows in IDCs and their geomorphic importance, a stretch of typical transverse dunefield was selected in the western part of the Korqin Sandy Land, and wind observations were undertaken using 3 automatic weather stations during high wind events in windy seasons. The results show that:(1) the unique secondary flows in the IDCs are rather stable, which are mainly from the south in winter and the southwest in spring, which substantially deviate from local prevailing wind direction (NW); (2) although wind velocity is greatly reduced by 30%-50% due to the hollow effect as compared with the upwind crest, spasmodic sand drifts occur by instantaneous gusts; (3) the turbulence intensity is significantly larger than other positions (upwind crest and lower downwind stoss) in spring and that in winter, while stratification stability is less than that in winter, tending to be unstable; (4) the unique secondary flow could, to a large extent, dig down the bottom of IDCs and help advance dune in winter, whereas it could not only deepen the IDCs but also make IDCs broaden gradually in spring.

Key words: Korqin Sandy Land, transverse dunefield, interdune corridor, secondary flow, flow deflection