Quantitative analysis on the dynamic characteristics of megadunes around the Crescent Moon Spring, China

The Crescent Moon Spring is a precious natural heritage. However, the dynamic characteristics of megadunes around the Crescent Moon Spring are not well known. This paper quantitatively studied the character- istics and changes of megadunes around the Crescent Moon Spring by interpreting aerial photographs taken in 1985 and 2004 and analysing the dune crestlines and the wind data collected from 2011 to 2012. Results revealed that pyramid dunes were formed by a complex wind regime. The Crescent Moon Spring was not buried by shifting sands because of the stable wind regime and relative stability of pyramid dunes. The crestlines of the dunes around the spring moved northward between 1985 and 2004. The south-facing slip faces were also exposed to wind ero- sion, whereas the other faces were under deposition, thus indicating that the southerly wind was relatively en- hanced. Limiting the scale of tall windbreaks and architectures in the Dunhuang oasis at the north of the spring was necessary to maintain the dynamic equilibrium of the wind regime and sand transport.

Progress on research and mitigation of wind-blown sand risk in Dunhuang Singing Sand Mountain and Crescent Spring Scenic area,China

The Singing Sand Mountain and Crescent Spring Scenic Spot in Dunhuang,Northwest China is a world-renowned desert attraction that is also an integral component of the Dunhuang UNESCO Global Geopark.This scenic area underwent a 30-year transformation,i.e.,from a severe sand risk with spring water threatened by sand burial due to dune deformation,to restoration of the original sand flow field and mitigation of the sand burial problem.The current paper summarizes the research on the intensive monitoring of the dynamic change of star dunes near the spring,observation of wind and sand flow movement,and then restoring the harmonic vibration of the sand particles(singing sand)that were previously silenced.The existing and prospective impacts of anthropogenic and natural forces on the deformation of the sand dunes are investigated by integrated methods,guiding the implementation of mitigating measures with significant ameliorative effects.Contrast to common sand control practices that aim to reduce wind speed and stop blown sands,our research highlights the importance of maintaining the natural wind flow field in stabilizing surrounding dunes.These mitigation measures consist of removing excessive vegetation and newly constructed buildings to recover the original wind flow field and sand transport activity.Such research and mitigation efforts ensure the scientific protection and restoration of the special desert landform,and contribute to the mutual enhancement of the conservation and exploitation of this desert scenic spot and similar sites.

Morphology and formation mechanism of sand shadow dunes on the Qinghai-Tibet Plateau

The formation and development of dunes depend on wind-blown sand movement which is affected by the characteristics of sand material, topography, wind regimes and other factors. In this paper, we investigated two sand shadow dune groups in Shigatse and Za＇gya Zangbo of Tibet and an individual dune in Da Qaidam of Qinghai, and analyzed their topographies and morphologies, and the physical characteristics of the sand, wind regime and sand transport. Formed under harsh conditions behind hills, these mature sand shadow dunes are hundreds of meters long, have significant ridges and crescent dunes downwind, and have a hill pass on one or both sides. Wind tunnel experiments revealed that the hill gap and wind velocity are important factors in the formation of these dunes Sand shadow dunes formed only when the gap spacing is two-thirds of the hill height. When wind velocities are 20 m/s, the sand body is divided into two parts. The hill pass allows the transport of sand by wind, creating a ＂nar- row-pipe effect＂, which causes the transported material to gradually accumulate in the center of the shadow zone. We observed that the following are needed for sand shadow dunes to form： （1） strong winds, sufficient sand, suitable obstacles and a dry climate; （2） one or both sides of the obstacle forming the shadow zone must have a hill pass; and （3） the windward side of the obstacle must have a wide, flat area, providing adequate spacing for wind flow and transport of material and the leeward side must have a sufficiently broad, flat area to allow the release of the transported material. Research results on these newly discovered dunes on the Qinghai-Tibet Plateau could contribute to the understanding of dune geomorphology.

Computational fluid dynamics evaluation of the effect of different city designs on the wind environment of a downwind natural heritage site

Disturbance in wind regime and sand erosion deposition balance may lead to burial and eventual vanishing of a site.This study conducted 3D computational fluid dynamics(CFD)simulations to evaluate the effect of a proposed city design on the wind environment of the Crescent Spring,a downwind natural heritage site located in Dunhuang,Northwestern China.Satellite terrain data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer(ASTER)Digital Elevation Model(DEM)were used to construct the solid surface model.Steady-state Reynolds Averaged Navier-Stokes equations(RANS)with shear stress transport(SST)k-ωturbulence model were then applied to solve the flow field problems.Land-use changes were modeled implicitly by dividing the underlying surface into different areas and by applying corresponding aerodynamic roughness lengths.Simulations were performed by using cases with different city areas and building heights.Results show that the selected model could capture the surface roughness changes and could adjust wind profile over a large area.Wind profiles varied over the greenfield to the north and over the Gobi land to the east of the spring.Therefore,different wind speed reduction effects were observed from various city construction scenarios.The current city design would lead to about 2 m/s of wind speed reduction at the downwind city edge and about 1 m/s of wind speed reduction at the north of the spring at 35-m height.Reducing the city height in the north greenfield area could efficiently eliminate the negative effects of wind spee.By contrast,restricting the city area worked better in the eastern Gobi area compared with other parts of the study area.Wind speed reduction in areas near the spring could be limited to 0.1 m/s by combining these two abatement strategies.The CFD method could be applied to simulate the wind environment affected by other land-use changes over a large terrain.

Anatomical variation of infra-pyloric artery origination： A prospective multicenter observational study (IPA-Origin)

Objective： Infra-pyloric artery （IPA） is an important anatomical landmark in treatment of gastric cancer and is the key vessel for pylorus-preserving gastrectomy and subgroup of infra-pyloric lymph nodes. However, its anatomical variation is not thoroughly understood. Our study aimed to clarify the origination of the IPA. Methods： We did this prospective, multicenter, open-label, observational study at gastric surgery departments of 34 hospitals in China. Gastric cancer patients aged 18 years or older and scheduled to undergo elective total or distal gastrectomy were assigned. During the surgery, IPA dissecting and exposing the origination point with photographs or video clips were required. The primary outcome was the origination of the IPA. Analysis of variance, χ2 tests and Fisher＇s tests were used to analyze the differences between groups. The study is registered at Clinicaltrials.gov （No. NCT03071237）. Results： Between May 8 and July 31, 2017, 429 patients were assigned for the study, and 419 （97.7%） patients had the IPA dissected and recorded through photograph or video and were included in the primary outcome analysis. The median age was 62 years old, and 73.7% were male. Among the patients, 78.5% received laparoscopic surgery. Single IPA origination was identified in 398 （95.0%） patients, including gastroduodenal artery （GDA） in 154 （36.8%） patients, anterior superior pancreaticoduodenal artery （ASPDA） in 130 （31.0%） patients, and right gastroepiploic artery （RGEA） in 114 （27.2%） patients. Fifteen （3.6%） patients were identified with multiple IPA and 6 （1.4%） patients were identified as IPA absence. The differences in the distribution of surgical approach （P=0.003） and geographic area （P=0.030） were statistically significant. No difference was shown in sex, age, gastrectomy type, tumor location, and clinical T, N and M stage. Conclusions： Our study found that the IPA originates from GDA, ASPDA and RGEA in similar proportions. Laparoscopic surgery may be more helpful in dissection of the IPA than open surgery.

Classification of full-polarization ALOS-PALSAR imagery using SVM in arid area of Dunhuang

Classification is an important process in interpretation of synthetic aperture radar （SAR） imagery. As an advanced instrument for remote sensing, the polarimetric SAR has been applied widely in many fields. The main aim of this paper is to explore the ability of the full-polarization SAR data in classification. The study area is a part of Dunhuang, Gansu Province, China. An L-band full-polarization image of Dunhuang which includes quad-polarization modes was acquired by the ALOS-PALSAR （Advanced Land Observing Satellite-the Phased Array type L-band Synthetic Aperture Radar）. Firstly, new characteristic information was extracted by the difference operation, ratio operation, and principal component transform based on the full-polarization （HH, HV or VH, VV） modes SAR data. Then the single-, dual-, full-polarization SAR data and new SAR characteristic information were used to analyze quantitatively the classification accuracy based on the Support Vector Machines （SVM）. The results show that classification overall accuracy of single-polarization SAR data is poor, and the highest is 56.53% of VV polarization. The classification overall accuracy of dual-polarization SAR is much better than single-polarization, the highest is 74.77% ofHV ＆ VV polarization data. The classification overall accuracy of full-polarization SAR is 80.21%, adding the difference characteristic information, ratio characteristic information and the first principal component （PC1） respectively, the overall accuracy increased by 3.09%, 3.38%, 4.14% respectively. When the full-polarization SAR data in combination with the all characteristic information, the classification overall accuracy reached to 91.01%. The full-polarization SAR data in combination with the band math characteristic information or the PC1 can greatly improve classification accuracy.

Methods for calculating glacier area and length in a mountainous area based on remote-sensing data and a digital elevation model

In a mountainous region, the glacier area and length extracted form the satellite imagery data is the projected area and length of the land surface, which can’t be representative of the reality; there are always some errors. In this paper, the methods of calculating glacier area and length calculation were put forward based on satellite imagery data and a digital elevation model (DEM). The pure pixels and the mixed pixels were extracted based on the linear spectral un-mixing approach, the slop of the pixels was calculated based on the DEM, then the area calculation method was presented. The projection length was obtained from the satellite imagery data, and the elevation differences was calculated from the DEM. The length calculation method was presented based on the Pythagorean theorem. For a glacier in the study area of western Qilian Mountain, northwestern China, the projected area and length were 140.93 km2 and 30.82 km, respectively. This compares with the results calculated by the methods in this paper, which were 155.16 km2 and 32.11 km respectively, a relative error of the projected area and length extracted from the LandSat Thematic Mapper (TM) image directly reach to -9.2 percent and -4.0 percent, respectively. The calculation method is more in accord with the practicality and can provide reference for some other object’s area and length monitoring in a mountainous region.

Wind tunnel simulation of the effects of freeze–thaw cycles on soil erosion in the Qinghai–Tibet Plateau

Intense freezing and thawing actions occur in the Qinghai-Tibet Plateau because of its high elevation and cold temperature. The plateau＇s unique environment makes it easy to generate wind erosion under dry, windy weather conditions, resulting in the emergence ofdesertification. As a major form of freeze-thaw erosion, freeze-thaw and wind erosion is displayed prominently on the Qinghai-Tibet Plateau. Therefore, in this study, soil samples were collected from the surface of the plateau to undergo freeze-thaw and wind erosion simulation experiments. Results show that wind erosion strength increases with an increasing number of freeze-thaw cycles, water content in the freezing-thawing process, and the difference in freeze-thaw temperatures. Therefore, in the conditions of water participation, the main reason for the freeze-thaw and wind erosion in the Qinghai-Tibet Plateau is the damage to the soil structure by repeated, fierce freeze-thaw actions, and the sand-bearing wind is the main driving force for this process. The research results have theoretical significance for exploring the formation mechanism of freeze-thaw and wind erosion in the Qinghai-Tibet Plateau, and provide a scientific basis for freeze-thaw desertification control in the plateau.

Climate change inferred from aeolian sediments in a lake shore environment in the central Tibetan Plateau during recent centuries

Studies of the past climate variation on the Tibetan Plateau(TP) are currently limited in number and low in density and temporal resolution. We investigated the climate condition from about 400 years before present(B.P.) in the central TP at the shore of Co(means "lake") Nag using aeolian sediments. A 2.7-m sand profile with 57 sediment samples and six optically stimulated luminescence(OSL) samples were studied through grain-size analysis, geochemical elements and parameters, and depositional rate estimation. A previous assumption was verified that sand deposition at the shore of Lake Co Nag originated from hills to the east. Two significant wet periods between 90–140 and about 380 years B.P. were indicated by the variation of element profiles and sediment depositional rates. Aeolian activity is sensitive to variations from different seasonal changing patterns of climate factors in the study area, and aeolian sediments respond differently to climate conditions during the cold little ice age(LIA) and the warm 20 th century. Present day dry seasons of winter and spring might be much warmer and drier compared to seasons of 400 years ago although summer precipitation has increased, resulting in significantly more aeolian activity and higher depositional rate(about 6 times compared to 380–240 years ago) of sandy sediments. Aeolian problems like blown-sand deposition and desertification may be worse in a projected warming future in the central TP as well as other cold and high altitude regions. Our results suggest an agreement with environmental evolution during the little ice age and the 20 th century in a broader scale on the TP.

Sand control effect of HDPE sandbreak nets with different porosity structure

Straw checkerboard sand barriers with a porous structure that consists of a pervious upper portion and a dense lower portion are widely used to achieve great sand control effect.Considering this,and resolving the serious earth surface undercutting problem after HDPE sandbreak net checkboard barriers setting,the authors used HDPE(high-density polyethylene)materials to prepare new sandbreak materials with a similar porous structure.Through wind tunnel simulations and field sand control monitoring,we compared the sand control effect of three HDPE sandbreak nets with different porosity structure.Compared to the sandbreak net with uniform porosity structure,the three types of HDPE sandbreak nets with different porosity structure had poorer effect on reducing sand transport rates,but had longer effective protection distance before sandbreak nets at low wind velocity conditions(<12 m/s),longer effective protection distance at high wind velocity(>14 m/s)and longer effective protection distance between sandbreak nets at all experimental wind velocity conditions.Wind and sand control effect characteristics of HDPE sandbreak nets with different porosity structure provide an ideal material on semiburied checkerboard sand barriers for sand stabilization.By contrast,uniform-type sandbreak nets are used as materials on high upright sand fences for sand blocking.These HDPE sandbreak nets can be used to replace traditional sandbreak materials and have a very high potential for widespread and popular application in aeolian sand disaster control.

Analyses on the Types,Distributions and Characteristics of Vegetation and Soil along Qinghai-Tibet Railway

[Objeective] The research aimed to study the types, distributions and characteristics of vegetation and soil along Qinghai -Tibet Rail- way. [ Method]Types, distributions and characteristics of vegetation and soil along Qinghai -Tibet Railway were studied by field investigation meth- od. [Result] The vegetation along Qinghai -Tibet Railway was dominated by alpine grassland and meadow, while the soil was dominated by alpine steppe soil and meadow soil corresponding along the railway. They both concentrated distnbutions at the section from Kunlun Mountain to Nyainqen- tanglha Mountain. [ Conclusion] The research could provide the basis for disaster control and resource development of Qinghai-Tibet Railway.

Overall efficiency of a V-shaped nylon net fence in preventing sand damage to the Mogao Grottoes

A V-shaped nylon net fence installed in 1990 on top of the Mogao Grottoes is shown to be effectively resisting aeolian sand damage to the grottoes. The structure guides and causes deposition of sand from westerly wind （the primary hard wind）, but to some extent hinders the inverse function of easterly wind carrying sand away from the grottoes toward Mount Mingsha. The gobi side by the fence experiences higher wind speed, so that on which are easily formed undercutting pits, and the deposited sands on it generally form double-peak structures due to abundant sand sources. If the earth surface characteristics in gobi areas by both sides of the fence are quite varied, the erosion and deposition features of the accumulating sand section are similar in different seasons; however, if the earth surface characteristics are similar, the features become irregular in different seasons. Sand depositions with long slope feet are formed along the south and north sides of V-shaped nylon net fence. Disrupted by strong westerly wind and northwesterly wind, sand accumulations by north of the fence are in form of single peaks. Although the operation duration of the V-shaped nylon net fence has exceeded its design life （10 years）, our observations indicate that it is still effective in reducing wind-driven sand damages to the Mogao Grottoes, so it should not be withdrawn.

A method to obtain soil-moisture estimates over bare agricultural fields in arid areas by using multi-angle RADARSAT-2 data

Soil moisture is an important parameter for agriculture, meteorological, and hydrological studies. This paper focuses on soil-moisture estimation methodology based on the multi-angle high-and low-incidence-angle mode RADARSAT-2 data obtained over bare agricultural fields in an arid area. Backscattering of the high-and low-incidence angles is simulated by using AIEM(advanced integral equation model), with the surface-roughness estimation model built based on the simulated data. Combining the surface-roughness estimation model with the backscattering model of the low-incidence-angle mode, a soil-moisture estimation method is put forward. First, the natural logarithm(ln) of soil moisture was obtained and then the soil moisture calculated. Soil moisture of the study area in Dunhuang, Gansu Province, was obtained based on this method; a good agreement was observed between the estimated and measured soil moisture. The coefficient of determination was 0.85, and the estimation precision reached 4.02% in root mean square error(RMSE). The results illustrate the high potential of the approach developed and RADARSAT-2 data to monitor soil moisture.

Glacier extraction based on ASAR,DEM and texture feature of ASAR using SVM in the Western Qilian Mountains,Northwest China

This paper is focused on the method for extracting glacier area based on ENVISAT ASAR Wide Swath Modes （WSM） data and digital elevation model （DEM） data, using support vector machines （SVM） classification method. The digitized result of the glaci- er coverage area in the western Qilian Mountains was extracted based on Enhanced LandSat Thematic Mapper （ETM＋） imagery, which was used to validate the precision of glacier extraction result. Because of similar backscattering of glacier, shadow and wa- ter, precision of the glacier coverage area extracted from single-polarization WSM data using SVM was only 35.4%. Then, texture features were extracted by the grey level co-occurrence matrix （GLCM）, with extracted glacier coverage area based on WSM data and texture feature information. Compared with the result extracted from WSM data, the precision improved 13.2%. However, the glacier was still seriously confused with shadow and water. Finally, DEM data was introduced to extract the glacier coverage area. Water and glacier can be differentiated because their distribution area has different elevations; shadow can be removed from the classification result based on simulated shadow imagery created by DEM data and SAR imaging parameters; finally, the glacier coverage area was extracted and the precision reached to 90.2%. Thus, it can be demonstrated that the glacier can be accurately semi-automatically extracted from SAR with this method. The method is suitable not only for ENVISAT ASAR WSM imagery, but also for other satellite SAR imagery, especially for SAR imagery covering mountainous areas.

Microclimate and CO_2 fluxes on continuous fine days in the Xihu desert wetland,China

The Xihu desert wetland is located in an extremely arid area in Dunhuang,Gansu province of Northwest China.The area is home to an unusual geographic and ecological environment that is considered unique,both in China and the world.Microclimate is not only related to topography,but is also affected by the physical properties of underlying ground surfaces.Microclimate and CO2 flux have different characteristics under different underlying surface conditions.However,until now,few studies have investigated the microclimate characteristics and CO2 flux in this area.The eddy covariance technique（ECT） is a widely used and effective method for studying such factors in different ecosystems.Basing on data from continuous fine days obtained in the Dunhuang Xihu desert wetland between September 2012 and September 2013,this paper discussed and compared the characteristics of daily microclimate variations and CO2 fluxes between the two periods.Results from both years showed that there was a level of turbulent mixing and updraft in the area,and that the turbulent momentum flux was controlled by wind shear under good weather conditions.The horizontal wind velocity,friction wind velocity and vertical wind velocity were commendably consistent with each other.Air temperature in the surface layer followed an initial decreasing trend,followed by an increasing then decreasing trend under similar net radiation conditions.With changes in air temperature,the soil temperature in the surface layer follows a more obvious sinusoidal fluctuation than that in the subsoil.Components of ground surface radiation during the two study periods showed typical diurnal variations.The maximum diurnal absorption of CO2 occurred at around 11：00（Beijing time） in the Xihu desert wetland,and the concentrations of CO2 in both periods gradually decreased with time.This area was therefore considered to act as a carbon sink during the two observation periods.

刷状沙柳沙障固沙性能风洞模拟

与传统的沙柳沙障人工逐根布设不同,刷状沙柳沙障采用机械编织形成,有类似拒马的外形,布设后稳定性好,也便于施工。对一种以沙柳枝条为原料的刷状沙障固沙性能进行了风洞模拟。结果表明:(1)在第1道沙障前风速略有降低,在第1、2、4道沙障处,风速增加较大。在经过每道沙障后,风速下降较大,形成一个降速区。(2)沙障正下方沙面多表现为侵蚀状态。迎风的第1道沙障,侵蚀现象最严重,随着时间推移,甚至发生掏蚀现象。沙障之间多处于堆积状态,第1格堆积最严重,其后堆积程度减弱。(3)沙障设置后,风沙流结构呈复杂的指数下降曲线。8、12、16、20 m·s^(-1)风速下的集沙量分别减少86.8%、81.6%、53.4%、67.8%。这表明刷状沙柳沙障有较好的固沙性能。由于沙障的扰动,沙物质向上飘散,使地表10~14 cm高度以上进沙口的集沙量有所增加。

Mechanisms of the formation of wind-blown sand hazards and the sand control measures in Gobi areas under extremely strong winds along the Lanzhou-Xinjiang high-speed railway

The Lanzhou-Xinjiang high-speed railway(HSR)traverses areas of the Gobi Desert where extremely strong winds are frequent.These strong winds cause sand/gravel hazards,an unaddressed issue that often seriously compromises the safe operation of the HSR.This paper studies the mechanisms leading to wind-blown sand hazards and the outcomes of sand control projects in these areas.The main findings are as follows:(1)Cold northern airflows over the Tian Shan mountain range are accelerated by the wind tunnels and downslope effect as they pass over complex terrain comprising passes,gullies,and proluvial fans.Consequently,the wind intensity often increases two-to threefold,creating frequent high-speed winds that lead to severe sand damage along the HSR.(2)In the Gobi areas with extremely strong winds,sand grains can be lifted as high as 9 m from the ground into the air,far higher than in other areas of the desert.The sand transport rate decreases exponentially with increasing height.Both wind speed and particle size determine saltation height.Coarser particles and stronger winds provide the particles with a higher kinetic energy as they collide with the ground.In the wind zones of Baili and Yandun,the analysed study areas,the saltation layer height of wind-blown sand/gravel exceeds 3 and 2 m,respectively.(3)Based on the above findings,recently emerging sand control materials,suitable for the areas of interest,were screened and developed.Furthermore,under the proposed principle of‘supplementing blocking with trapping’,a comprehensive sand control measure was established,featuring sandblocking belts comprised of multiple rows,and high,vertical sand-trapping installations with a large grids size.The installed system showed a high efficacy,reducing sand transport rate by 87.87%and significantly decreasing the deposition of sand along a trial section of the HSR.

Aeolian sediment transport over sandy gobi:Field studies in the Nanhu gobi along the Hami-Lop Nor Railway

Wind-blown sand over sandy gobi with an abundant sediment supply can cause severe sand hazards.However,compared with the study of aeolian transport over gravel gobi with a limited sediment supply,less attention has been devoted to sandy gobi,and thus,our understanding of wind-blown sand movement on sandy gobi is still poor.Here,we report the results of observations of three transport events on a sandy gobi along the Hami-Lop Nor Railway based on high-frequency saltation particle count and horizontal sediment flux measurements coupled with instantaneous wind velocity measurements.The results reveal that,unlike the notably intermittent aeolian saltation over gravel gobi,continuous transport occurred on the sandy gobi.The mean saltation layer height was 0.23±0.07 m,and it was positively related to both the grain size of surface particles and the wind velocity regardless of the gobi type.The sediment transport rates could be expressed as the power function Q=ap/g[u^(*)(u^(*2)-u^(*)t^(2))]b,and the scaling parameter(b)reached to 2.5,which is much larger than that of other gobi areas(b=1).Our findings suggest that the wind-blown sand over sandy gobi is much more severe than that over gravel gobi,and the Nanhu sandy gobi is the major sand source for sand hazards of the Hami-Lop Nor Railway.Sand-fixation measures such as checkerboard sand barriers with enhanced checkerboard size and barrier height should be the main subject of sand control systems for the Hami-Lop Nor Railway in sandy gobi.

Estimation of wind erosion from construction of a railway in arid Northwest China

A state-of-the-art wind erosion simulation model,the Wind Erosion Prediction System and the United States Environmental Protection Agency's AP 42 emission factors formula,were combined together to evaluate wind-blown dust emissions from various construction units from a railway construction project in the dry Gobi land in Northwest China.The influence of the climatic factors:temperature,precipitation,wind speed and direction,soil condition,protective measures,and construction disturbance were taken into account.Driven by daily and sub-daily climate data and using specific detailed management fles,the process-based WEPS model was able to express the beginning,active,and ending phases of construction,as well as the degree of disturbance for the entire scope of a construction project.The Lanzhou-Xinjiang High-speed Railway was selected as a representative study because of the diversities of different cli-mates,soil,and working schedule conditions that could be analyzed.Wind erosion from different working units included the building of roadbeds,bridges,plants,temporary houses,earth spoil and barrow pit areas,and vehicle transportation were calculated.The total wind erosion emissions,7406 t,for the first construction area of section LXS-15 with a 14.877 km length was obtained for quantitative analysis.The method used is applicable for evaluating wind erosion from other complex surface dis-turbance projects.

中国海南岛海岸鸣沙群的发现及其意义

海岸鸣沙的分布,被认为是优质海滩的体现,研究发现中国海南岛有海岸鸣沙分布,填补了中国没有海岸鸣沙的空白.清水湾和神州半岛独特的海湾地貌,以及与之形成的独特的破浪动力过程,塑造出粒度分选良好的海岸鸣沙.对清水湾和神州半岛海岸鸣沙与巴丹吉林沙漠鸣沙矿物组成、粒度分布和表面结构,以及鸣沙发声的声学特征观测和测量,对比研究发现:(1)海岸鸣沙矿物组成中石英含量明显高于沙漠鸣沙,而长石含量明显低于沙漠鸣沙;(2)海岸鸣沙粒径粗于沙漠鸣沙,中沙和粗沙组分含量明显增多;(3)海岸鸣沙表面具有典型的水下机械刻蚀作用而成的“V”形撞击坑和化学溶蚀作用而成的深邃溶蚀坑,这种发育良好的表面多孔状物理结构正是控制鸣沙发声机理的重要因素;(4)海岸鸣沙频谱较之沙漠鸣沙窄,高频成分占比高,声音相对尖锐.