Wind regime features and their impacts on the middle reaches of the Yarlung Zangbo River on the Tibetan Plateau, China

The wide valley of the Yarlung Zangbo River is one of the most intense areas in terms of aeolian activity on the Tibetan Plateau,China.In the past,the evaluation of the intensity of aeolian activity in the Quxu–Sangri section of the Yarlung Zangbo River Valley was mainly based on data from the old meteorological stations,especially in non-sandy areas.In 2020,six new meteorological stations,which are closest to the new meteorological stations,were built in the wind erosion source regions(i.e.,sandy areas)in the Quxu–Sangri section.In this study,based on mathematical statistics and empirical orthogonal function(EOF)decomposition analysis,we compared the difference of the wind regime between new meteorological stations and old meteorological stations from December 2020 to November 2021,and discussed the reasons for the discrepancy.The results showed that sandy and non-sandy areas differed significantly regarding the mean velocity(8.3(±0.3)versus 7.7(±0.3)m/s,respectively),frequency(12.9%(±6.2%)versus 2.9%(±1.9%),respectively),and dominant direction(nearly east or west versus nearly north or south,respectively)of sand-driving winds,drift potential(168.1(±77.3)versus 24.0(±17.9)VU(where VU is the vector unit),respectively),resultant drift potential(92.3(±78.5)versus 8.7(±9.2)VU,respectively),and resultant drift direction(nearly westward or eastward versus nearly southward or northward,respectively).This indicated an obvious spatial variation in the wind regime between sandy and non-sandy areas and suggested that there exist problems when using wind velocity data from non-sandy areas to evaluate the wind regime in sandy areas.The wind regime between sandy and non-sandy areas differed due to the differences in topography,heat flows,and their coupling with underlying surface,thereby affecting the local atmospheric circulation.Affected by large-scale circulations(westerly jet and Indian monsoon systems),both sandy and non-sandy areas showed similar seasonal variations in their respective wind regime.These findings provide a credible reference for re-understanding the wind regime and scientific wind-sand control in the middle reaches of the Yarlung Zangbo River Valley.

Wind regime for long-ridge yardangs in the Qaidam Basin, Northwest China

Yardangs are typical aeolian erosion landforms,which are attracting more and more attention of geomorphologists and geologists for their various morphology and enigmatic formation mechanisms.In order to clarify the aeolian environments that influence the development of long-ridge yardangs in the northwestern Qaidam Basin of China,the present research investigated the winds by installing wind observation tower in the field.We found that the sand-driving winds mainly blow from the north-northwest,northwest and north,and occur the most frequent in summer,because the high temperature increases atmospheric instability and leads to downward momentum transfer and active local convection during these months.The annual drift potential and the ratio of resultant drift potential indicate that the study area pertains to a high-energy wind environment and a narrow unimodal wind regime.The wind energy decreases from northwest to southeast in the Qaidam Basin,with the northerly winds in the northwestern basin changing to more westerly in the southeastern basin.The strong and unidirectional wind regime for the long-ridge yardangs in the northwestern Qaidam Basin results from the combined effects of topographic obstacles such as the Altun Mountains and of the interaction between the air stream and the yardang bodies.Present study suggests that yardang evolution needs such strong and unidirectional winds in high-or intermediate-energy wind environments.This differs from sandy deserts or sandy lands,which usually develop at low-or intermediate-energy wind environments.Present study clarifies the wind regime corresponding to the long-ridge yardangs'development,and lays firm foundation to put forward the formation mechanisms for yardangs in the Qaidam Basin.

Wind regimes and associated sand dune types in the hinterland of the Badain Jaran Desert,China

Wind controls the formation and development of sand dunes.Therefore,understanding the wind regimes is necessary in sand dune research.In this study,we combined the wind data from 2017 to 2019 at four meteorological stations(Cherigele and Wuertabulage stations in the lake basins,and Yikeri and Sumujilin stations on the top of sand dunes)in the hinterland of the Badain Jaran Desert in China,with high resolution Google Earth images to analyze the correlation between the wind energy environments and dune morphology.The results of data analysis indicated that both the wind direction and sand drift intensity exhibited notable spatial and temporal variations.The highest level of wind activity was observed in spring.Northwesterly and northeasterly winds were the dominant in the Badain Jaran Desert.At the Cherigele,Wuertabulage,and Yikeri stations,the drift potential(DP)was below 200.00 vector units(VU).The wind energy environments in most areas could be classified as low-energy environments.The resultant drift direction differed at different stations and in different seasons,but the overall direction was mainly the southeast.The resultant drift potential(RDP)/DP ratio was greater than 0.30 in most parts of the study area,suggesting that the wind regimes mainly exhibited unimodal or bimodal characteristics.Differences between the thermodynamic properties and the unique landscape settings of lakes and sand dunes could alter the local circulation and intensify the complexity of the wind regimes.The wind regimes were weaker in the lake basins than on the top of sand dunes.Transverse dunes were the most dominant types of sand dunes in the study area,and the wind regimes at most stations were consistent with sand dune types.Wind was thus the main dynamic factor affecting the formation of sand dunes in the Badain Jaran Desert BJD.The results of this study are important for understanding the relationship between the wind regimes and aeolian landforms of the dune field in the deserts.

Late Jurassic-Early Cretaceous Erg Deposits in the Mengyin Basin, Western Shandong Province, China: Inferences about the Wind Regime and Paleogeography

The Late Jurassic-Early Cretaceous Santai Formation, sporadically distributed in western Shandong Province, comprises terrestrial alluvial-eolian successions, which records regional wind patterns and paleogeography in eastern North China. This paper conducts an analysis of eolian stratification, bounding surfaces, facies architecture and paleowind direction of the Santai Formation in the east of the Mengyin Basin, western Shandong Province. Three basic types of eolian stratification are recognized in the Santai Formation, including grainflow strata, wind ripple strata and adhesion strata, and have been grouped into eolian dune and interdune facies associations. The occurrences of reactivation surfaces and superimposition surfaces within eolian dune deposits indicate active compound dunes or draas. The association of adhesion strata with grainflow or windripple strata is the development of a wet eolian system. Cross-strata dip direction indicates different paleowind directions from the lower to the upper part of the Santai paleoerg. The lower part of the paleoerg was characterized by paleowinds blowing from northwest to northeast, whereas the upper part was under the influence of paleowinds consistently towards east to northeast. The identified changes in wind directions possibly suggest wind regime shifts from monsoon circulation to westlies of planetary wind system, which may be related with the collapse of the East China Plateau during the Late Jurassic to Early Cretaceous.

Near-surface wind field characteristics of the desert-oasis transition zone in Dunhuang,China

The desert-oasis transition zone(DOTZ)serves as a buffer area between the desert and oasis.Understanding its wind field characteristics is of great significance for the prevention and control of aeolian disasters in the oasis.In this study,we used meteorological data during 2013–2019 from the portable meteorological stations at five sites(site A on the edge of the oasis,sites B,C,and D in the DOTZ,and site O in the desert)in Dunhuang,China to analyze the near-surface wind field characteristics and their causes,as well as to reveal the key role of the DOTZ in oasis protection.The results showed that the mean wind speed,frequency of sand-driving wind,and directional variability of wind decreased from west to east within the DOTZ,and wind speed was significantly affected by air temperature.The terrain influenced the prevailing winds in the region,mainly from northeast and southwest.Only some areas adjacent to the oasis were controlled by southeasterly wind.This indicated that the near-surface wind field characteristics of the DOTZ were caused by the combined effects of local terrain and surface hydrothermal difference.At site D,the annual drift potential(DP)was 24.95 vector units(VU),indicating a low wind energy environment,and the resultant drift direction(RDD)showed obvious seasonal differences.Additionally,the DOTZ played an important buffering role between the desert and oasis.Compared with the desert,the mean wind speed in the oasis decreased by 64.98%,and the prevailing wind direction was more concentrated.The results of this study will be useful in interpreting the aeolian activity of the DOTZ in Dunhuang.

Covariation of the Indonesian Throughflow and South China Sea Throughflow Associated with the 1976/77 Regime Shift

Changes in the Indonesian Throughflow （ITF） and the South China Sea throughflow-measured by the Luzon Strait Transport （LST）-associated with the 1976/77 regime shift are analyzed using the Island Rule theory and the Simple Ocean Data Assimilation dataset. Results show that LST increased but ITF transport decreased after 1975. Such changes were induced by variations in wind stress associated with the regime shift. The strengthening of the easterly wind anomaly east of the Luzon Strait played an important role in the increase of LST after 1975, while the westerly wind anomaly in the equatorial Pacific contributed significantly to the decrease in ITF transport after 1975; accounting for 53% of the change. After 1975, the Kuroshio Current strengthened and the Mindanao Current weakened in response to a decrease in the total transport of the North Equatorial Current. Both the North Equatorial Countercurrent and the South Equatorial Current weakened after 1975, and an anomalous cyclonic circulation in the western equatorial Pacific prevented the tropical Pacific water from entering the Indian Ocean directly.

面向产黏性卵鱼类繁殖需求的水风光生态协同调度

黏性卵黏附于砾石表面或砾石间隙中、近岸浅坑中发育孵化,对产卵场水文条件有特定需求。水风光互补运行下水电调峰造成日内下泄流量变化率增大,易导致黏性鱼卵暴露于空气中干燥死亡。已有生态流量缺乏日内流量变化率的量化研究,水风光协同调度缺乏鱼类繁殖适宜流量过程的考虑。提出通过计算不同流量工况下鱼类繁殖适宜生境面积的重叠率,以评估不同基准流量下生态适宜的流量变化率。同时,综合考虑水电调峰对新能源消纳及其对水文情势的改变,提出一种面向鱼类繁殖需求的水风光生态协同调度模型。以羊曲坝下河段为例,结果表明,为满足产黏沉性卵鱼类繁殖需求,最大流量增率不宜超过120 m^(3)/(s·h);生态权衡调度方案相比调峰效益最大解,平水和枯水时期分别减少7%和6%的新能源消纳量,减少2%和6%的水电出力,但水文情势的改变量相比降低了15%和21%。研究成果可为鱼类产卵期水电站生态调度优化运行提供技术支撑,促进水电可持续发展。

塔克拉玛干沙漠南缘新月形沙丘移动特征

新月形沙丘的移动特征可以反映区域内风沙运移和地貌演化过程,对于科学开展风沙灾害防治具有重要意义。本文利用卫星遥感影像与气象再分析数据,研究了塔克拉玛干沙漠南缘6个新月形沙丘群2012—2022年的形态变化与移动特征。结果表明:(1)研究区域内新月形沙丘平均移动速率为6.86 m·a^(-1),移动方向与对应区域内盛行风方向基本一致;(2)不同区域内新月形沙丘形态参数之间的关联性呈现显著差异;(3)沙丘高度、下垫面植被覆盖、年均降雨量以及地表温度与沙丘移动速率呈负相关关系,分区拟合结果有差异;(4)且末西南区域的年平均输沙通量约为77120.5 kg·m^(-1)。研究结果反映了新月形沙丘移动规律的复杂性,不同地理环境因子的影响程度或存在显著差异,需结合实地情况进行具体分析。同时,在沙丘演化过程中,形态参数的动态变化反映了沙丘迁移的内在机理,进一步为新月形沙丘的发育机理提供了实证数据,也为沙丘危害防治和土地规划提供了参考依据。

Near-surface wind environment in the Yarlung Zangbo River basin,southern Tibetan Plateau

Aeolian processes have been studied extensively at low elevations,but have been relatively little studied at high elevations.Aeolian sediments are widely distributed in the Yarlung Zangbo River basin,southern Tibetan Plateau,which is characterized by low pressure and low temperature.Here,we comprehensively analyzed the wind regime using data since 1980 from 11 meteorological stations in the study area,and examined the interaction between the near-surface wind and aeolian environment.The wind environment exhibited significant spatial and temporal variation,and mean wind speed has generally decreased on both annual and seasonal bases since 1980,at an average of 0.181 m/(s•10a).This decrease resulted from the reduced contribution of maximum wind speed,and depended strongly on variations of the frequency of sand-driving winds.The drift potential and related parameters also showed obvious spatial and temporal variation,with similar driving forces for the wind environment.The strength of the wind regime affected the formation and development of the aeolian geomorphological pattern,but with variation caused by local topography and sediment sources.The drift potential and resultant drift direction were two key parameters,as they quantify the dynamic conditions and depositional orientation of the aeolian sediments.Wind affected the spatial variation in sediment grain size,but the source material and complex topographic effects on the near-surface wind were the underlying causes for the grain size distribution of aeolian sands.These results will support efforts to control aeolian desertification in the basin and improve our understanding of aeolian processes in high-elevation environments.

东海海岛大气环境中氯离子沉积速率检测与影响分析

为了研究东海海岛大气环境中氯离子沉积速率的影响因素,开展了大气测试点氯离子沉积速率检测,分析了离海岸线距离、测试点方位、季节、降雨量、风向与风能等对氯离子沉积速率的影响。研究表明,氯离子沉积速率随离海岸线距离的增加而降低。摘箬山岛各测试点冬季氯离子沉积速率高于春、夏季,东北方向测试点氯离子沉积速率最大。氯离子沉积速率是风向、风能、降雨量等多因素影响的结果。

Aeolian activity in the southern Gurbantunggut Desert of China during the last 900 years

The mineral dust emitted from Central Asia has a significant influence on the global climate system.However,the history and mechanisms of aeolian activity in Central Asia remain unclear,due to the lack of well-dated records of aeolian activity and the intense wind erosion in some of the dust source areas(e.g.,deserts).Here,we present the records of aeolian activity from a sedimentary sequence in the southern Gurbantunggut Desert of China using grain size analysis and optically stimulated luminescence(OSL)dating,based on field sampling in 2019.Specifically,we used eight OSL dates to construct chronological frameworks and applied the end-member(EM)analysis for the grain size data to extract the information of aeolian activity in the southern Gurbantunggut Desert during the last 900 a.The results show that the grain size dataset can be subdivided into three EMs(EM1,EM2,and EM3).The primary modal sizes of these EMs(EM1,EM2,and EM3)are 126.00,178.00,and 283.00μm,respectively.EM1 represents a mixture of the suspension components and saltation dust,while EM2 and EM3 show saltation dust transported over a shorter distance via strengthened near-surface winds,which can be used to trace aeolian activity.Combined with the OSL chronology,our results demonstrate that during the last 900 a,more intensive and frequent aeolian activity occurred during 450-100 a BP(Before Present)(i.e.,the Little Ice Age(LIA)),which was reflected by a higher proportion of the coarse-grained components(EM2+EM3).Aeolian activity decreased during 900-450 a BP(i.e.,the Medieval Warm Period(MWP))and 100 a BP-present(i.e.,the Current Warm Period(CWP)).Intensified aeolian activity was associated with the strengthening of the Siberian High and cooling events at high northern latitudes.We propose that the Siberian High,under the influence of temperature changes at high northern latitudes,controlled the frequency and intensity of aeolian activity in Central Asia.Cooling at high northern latitudes would have significantly enhanced the Siberian High,causing its position to shift southward.Subsequently,the incursion of cold air masses from high northern latitudes resulted in stronger wind regimes and increased dust emissions from the southern Gurbantunggut Desert.It is possible that aeolian activity may be weakened in Central Asia under future global warming scenarios,but the impact of human activities on this region must also be considered.

基于SST模式的超临界条件下梭形柱气动力及流场特性研究

为研究超临界条件下梭形柱的气动力及流场特性,采用剪切应力运输(Shear Stress Transport, SST)模式进行CFD(Computational Fluid Dynamics)数值试验。通过流场性质分析,总结了梭形柱流场分布规律,并讨论了其气动特性形成的机理。首先建立直径为30 cm的圆柱模型,应用Fluent软件模拟其在超临界条件下(Re=7.2×10^(5))的绕流试验。将数值计算结果与已有文献中风洞试验数据对比,验证了数值模拟的合理准确性。然后保持计算参数、网格模型不变,通过改变梭形柱长短轴之比,分别计算不同扁率梭形柱的气动参数。最后通过流场分布特性分析,解释了气动性质变化的机理。通过研究得到以下结论:梭形柱阻力系数平均值、均方差均随梭形柱扁率增加而增加,且阻力系数平均值随扁率成线性增加。给出了阻力系数估算公式,以便快速估算梭形柱阻力系数。升力系数平均值基本维持在0,均方差随扁率先增大后减小。小扁率梭形柱脱涡频率随扁率增加起伏下降,大扁率梭形柱脱涡频率随扁率快速下降。梭形柱的分离角一般在边缘位置,且边缘位置的平均风压系数、脉动风压系数均随扁率增加而增加。

铁路高架桥对局地风动力的影响——以敦格铁路沙山沟为例

本文通过野外观测、室内分析计算、CFD数值模拟方法,对敦格铁路沙山沟特大桥东西两侧风动力环境特征进行研究分析。结果表明:(1)沙山沟特大桥东西两侧春夏季起沙风主要以NW和WNW风向为主,秋冬季起沙风向主要以SE、S风为主;沙山沟特大桥西侧全年输沙势为284.19 VU,属于中等风能环境,合成输沙势为27.4 VU,合成输沙风向为124°,方向变率指数为0.10,属于小比率,风向多变。(2)沙山沟特大桥东侧年输沙势为31.24 VU,属于低风能环境,合成输沙势为8.97 VU,合成输沙风向为91°,方向变率指数为0.29,属于中比率;沙山沟特大桥西侧平均风速、起沙风频率、输沙势、合成输沙势较大,应加强高架桥西侧沙害监测与防治;根据高架桥西侧风动力环境特点并结合流动沙丘进行模拟,分析得出桥底架空区域及桥面风速均大于起沙风速,输沙能力较强,不易产生积沙。但随着沙丘的前移,桥底架空区域产生积沙及风沙上轨可能性增大。

WIND REGIME IN URBAN PLANNING AND INDUSTRIAL DISTRIBUTION

The function of wind regime in urban planning and general layout of industrial enter-prise is discussed. It is pointed out that if only the dominant wind direction is taken intoconsideration in urban planning and industrial distribution, undesirable layout may result.In regard to this some characteristics of the wind directions in monsoonal China are ana-lysed, a geographical regionalization is proposed and the patterns of urban land-use accord-ing to wind direction are discussed. Finally a new pollution coefficient is suggested.

塔克拉玛干沙漠风况特征研究

通过17个站1996-2000年风资料的统计和计算,对塔克拉玛干沙漠风况特征进行研究,结果发现:(1)塔克拉玛干沙漠作用风系以东北风和西北风为主,在纵向和横向上主风向都呈现出明显变化规律;(2)输沙势计算结果表明,除若羌地区外整个塔克拉玛干沙漠处于低风能环境;(3)大多数区域RDP/DP值都大于0.5,呈现单峰或锐双峰特征。

塔克拉玛干沙漠地面风场特征及周边地区沙丘排列关系分析

通过对1996～2000年17个气象站风资料的分析和计算,结合高空环流形势分析,对塔克拉玛干沙漠近地面风场特征进行了研究,并对风场特征与周边地区沙丘排列方向之间的关系进行了分析.研究表明:①塔克拉玛干沙漠近地面风场特征是在高空西风带的背景下,经过青藏高原、天山山脉的动力分支和抬升等作用下形成的.冬季,尼雅河以东盛行偏东风,以西盛行偏西风;夏季,克里雅河以西地区盛行偏西北风和西风,以东盛行东北风.②从东到西,东北风系影响逐渐减弱而西北风系影响逐渐加强;南北方向变化较为复杂.③除若羌地区外,塔克拉玛干沙漠输沙势都小于200 VU,属于低能风环境,且以单峰或锐双峰为主.在区域分布上,沙漠东部及中部强度较大,西部及南部较小.④沙丘排列方向主要由主、次输沙方向的夹角及二者的输沙比率决定,其走向与最大输沙总量垂直.

科尔沁沙地奈曼旗近5年来风况及合成输沙势

应用奈曼沙漠化研究站1998—2002年的气象资料,统计分析了奈曼旗近5a来的风况特征和输沙势。结果表明:①研究区3～5月起沙风发生频数最高,占全年起沙风的38%～58%;平均风速和最大风速值最大,分别为6.0～7.5m·s-1和9.5～16.9m·s-1。该风况特征与地表冻融、裸露、干旱疏松相耦合,形成了区内的风沙活动期。②在风沙活动期内,风环境基本为锐双峰风况,西北风居主导地位,频数占54%;南风和西南风次之,频数占38%。③在风沙活动期内,研究区属于高风能环境,合成输沙势RDP为66.3VU(风速以m·s-1为单位),合成输沙方向RDD为ESE113°。

基于天气分类的风电场群总体出力特性分析

分析风电场群总体出力特性有助于缓解大规模风电接入后的系统调峰压力,提高风电接纳水平。研究了在不同天气类型下,风电场群总体出力的特性规律。基于气象再分析数据,利用主成分分析和层次聚类法,对影响风电场群地理区域的天气类型进行分类,识别出若干种典型的天气类型。然后结合实际风电出力数据,对不同天气类型下的风电总体出力的波动性和平滑效应进行分析,揭示了天气类型与总体出力特性之间的内在联系。以蒙西电网6个风电场为研究对象,分类得到影响上述风电场的8种典型的天气系统,并对这8种天气类型下风电场群总体出力的特性进行研究。最后基于IEEE 24节点系统分析了在不同天气类型下,风电场群总体出力接入后对系统调峰能力的影响,并根据分析结果对电网调度提出了建议。

塔克拉玛干沙漠起沙风况

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