| The edge of eastern Kumtag Desert’ location is a special region withfragile ecologicalenvironment, where is an important area with the sandstorms occurrence and development inour country. The historical and cultural city of Dunhuang is located in the east of KumtagDesert, so Kumtag Desert becomes a main source of dust to Dunhuang, and the ecotone locatedbetween Dunhuang Oasis and Kumtag Desert becomes a natural barrier to prevent dustinvasion Oasis. Therefore, to study the wind and sand activity characteristics and typicalaeolian geomorphology in desert-oasis ecotone is meaningful for revealing the formation ofregional aeolian landforms. It also provides theoretical reference for desertification combatingin Dunhuang. In this study a statistical analysis on wind regimes in the eastern marginal zoneof the Kumtag Desert and characteristics of profiles of “feather-like dunes” was carried outduring the period from2012to2013. The principle features and findings are listed as follows:(1) The average wind velocity is3.5m/s in the eastern marginal zone of the KumtagDesert, the winds of2-5m/s account for63.7%of all winds, and the wind more than6m/saccounts for10%. Wind velocity increases with the height as a power function. The averagewind velocity has gradually decreased since the1970. Sand-moving wind in the study areaoccurs mainly in April to July and the frequency is56.32percent, and the frequency ofsand-moving wind during16:00to18:00was6percent.(2) This region is affected predominantly by NW and NNE winds during the daytime, andSSE winds during the night, there is a higher accumulated frequency of sand-moving windswith22.62percent in the WNW and17.25percent in the ENE. Finally, sand-moving windsdo not change significantly in daytime and nighttime.(3) There is a higher sand-transport potential in the ENE and WNW directions, and thesand-transport potential is40.83VU and33.24VU, resultant sand-transporting potential (RDP)54.73VU, resultant sand-transporting direction (RDD)189°S. There is a higher drift potential (DP) with71.68VU and sand-transporting potential (RDP) with45VU in the spring, and theRDPis43.31VU and the DP30.6VU in April.(4) The average annual sandstorm days have6days, and spring and summer are theseasons with more dust weather, the sandstorm days and jansa days and dust weather show adecreasing trend during1950to2008.(5) Horizontal aeolian dust flux decays with height in power exponentiation, the totalhorizontal aeolian dust flux through the transect with a height of24m and width of1m is1,759kg a year, of which23.08percent of the total horizontal aeolian dust flux comes from NEand19.97percent from W, and the resultant sand-transporting direction is181.36°S, theresultant sand-transporting465.47kg.(6) The dust is mainly composed of fine sand, very fine sand and silts at the height of0--24m in the eastern marginal zone of the Kumtag Desert. The particle size distribution curvecan be divided into2parts:0-8m is the lower part, where the percentage content of siltsincreased with height, but the percentage content of fine sand decreased with the increase ofheight;8-24m is the upper part, where the percentage content of silts and the percentagecontent of fine sand change little with height. The skewness of dust is “positively biased”,and the frequency curve “single peak curve”, the sorting coefficient of the dust increases withheight. The fine sand and very fine sand take a large proportion in different land surfaces, theaverage grain diameter is in the range from2.46φ to3.08φ in six surfaces, which all the sixsurfaces can supply dust to air potentially.(7) The shrubs and barchan dunes in the eastern marginal zone of the Kumtag Desertand the farmland shelterbelt in oasis have significant effects on wind-provention andsand-stabilization, the horizontal aeolian dust flux in transitional zone and in oasis are reducedby22.57percent to48.54percent than that in desert, and89.64percent to93.9percent,respectively.(8) The direction of “quill” of “feather-like dunes” is NE55°, and the “quill” composesof crescent dunes ridges with the average height of17.65m, whichthe average length of northwest wing is generally72m, longer than their southeast wing. Great fluctuation is foundfrom the profile of the “quill”: the wave length is50-100m, and the wave height10-25m.The average width and slop of the “quill” are127.69m and12.59°, respectively. The averagelength and slop of northwest slope were71.74m and11.65°, respectively. The average lengthand slop of southeast slope were50.09m and13.52°, respectively. The “plume” of “feather-likedunes” is composed of large dome-like sand dune waves, not a “feathery” pattern of light anddark hues as shown in remote sensing images. The average width of the large dome sand dunewaves is641.34m, with a relatively flat profile. The distance between two waves is about400m, and the wave height ranges in1-3m, the average slop length and average gradient are322.37m and1.28°, respectively. |
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