Estimation of the Land Surface Emissivity in the Hinterland of Taklimakan Desert   总被引：3，自引：2，他引：1  

LIU Yong-qiang  Ali MAMTIMIN  HUO Wen  YANG Xing-hua  LIU Xin-chun  MENG Xian-yong  HE Qing 《山地科学学报》2014,(6):1543-1551

An accurate accounting of land surface emissivity(ε) is important both for the retrieval of surface temperatures and the calculation of the longwave surface energy budgets.Since ε is one of the important parameterizations in land surface models(LSMs),accurate accounting also improves the accuracy of surface temperatures and sensible heat fluxes simulated by LSMs.In order to obtain an accurate emissivity,this paper focuses on estimating ε from data collected in the hinterland of Taklimakan Desert by two different methods.In the first method,ε was derived from the surface broadband emissivity in the 8–14 μm thermal infrared atmospheric window,which was determined from spectral radiances observed by field measurements using a portable Fourier transform infrared spectrometer,the mean ε being 0.9051.The second method compared the observed and calculated heat fluxes under nearneutral atmospheric stability and estimated ε indirectly by minimizing the root-mean-square difference between them.The result of the second method found a mean value of 0.9042,which is consistent with the result by the first method.Although the two methods recover ε from different field experiments and data,the difference of meanvalues is 0.0009.The first method is superior to the indirect method,and is also more convenient.  相似文献   

Pediment response to drainage basin evolution in south-central Arizona     

Phillip H. Larson  Ronald I. Dorn  R. Evan Palmer  Zack Bowles  Emma Harrison  Scott Kelley 《自然地理学》2014,35(5):369-389

The Sonoran Desert portion of the Basin and Range physiographic province contains a number of streams that now flow across once-closed basins. We explore here the research questions of if and how granitic rock pediments respond to the transition from rimming endorheic basins to bordering through-flowing streams. Granitic rock pediments of the northern Usery and eastern McDowell Mountains once graded to the closed Miocene–Pliocene Pemberton basin that occupied the present-day location of the confluence of the Salt and Verde Rivers. The process of lake overflow, which integrated these rivers, first aggraded fill terraces that, in turn, caused aggradation of a mantle of transported grus on bedrock pediments. Subsequent episodic incision of the Salt and Verde rivers lowered the base level; this led to the development of erosional features such as rolling topography of a degrading pediment mantle; exposure of the former piedmont angle and its associated zones of enhanced bedrock decay and regolith carbonate; and exposure of spheroidally weathered bedrock and emerging tors, some of which experienced 20^th century erosion. The granitic pediments of the former Pemberton Basin, which now transport grus to the Salt and Verde rivers, have actively adjusted to aggradational and degradational events associated with drainage integration and do not appear to be inherited from an ancient wet climatic interval.  相似文献   

腾格里沙漠不同类型沙丘土壤水分含量与地形-植被因子关系研究          下载免费PDF全文

孙琰蕙  张定海  张志山 《干旱区地理》2022,45(5):1570-1578

土壤水分是沙区主要的生态限制因子,其分布受气候、地形和植被等众多因素的影响。以腾格里沙漠沙坡头地区3种类型的沙丘（固定沙丘、半固定沙丘和流动沙丘）为研究对象,利用方差分析和冗余分析（RDA）等方法对沙丘不同部位和不同深度土壤水分的分布特征及其与地形-植被因子之间的关系进行了综合分析。结果表明：（1） 不同类型沙丘上0~300 cm的土壤水分随着深度的增加而增加,表层土壤水分的波动程度大于中层和深层。（2） 固定沙丘不同部位及不同深度的土壤水分之间没有明显的差异,半固定沙丘和流动沙丘迎风坡与丘底的土壤水分高于背风坡和丘顶。（3） 固定沙丘上的土壤水分受地形-植被因子的影响较半固定沙丘和流动沙丘小,影响固定沙丘土壤水分的主要因子有坡向、高差和灌木多度。（4） 地形-植被因子与研究区绝大多数半固定沙丘和流动沙丘的土壤水分均有负相关关系。研究揭示了腾格里沙漠土壤水分的分布规律及其与地形-植被因子的关系,对制定相应的防风固沙措施以及建立科学合理的植物固沙模式有积极的指导作用。  相似文献   

THE PRECIPITATION INFILTRATION AND RUNOFF RECHARGING EXPERIMENT OBSERVATION IN THE TAKLIMAKAN DESERT     

王学全  高前兆 《中国地理科学(英文版)》1999,9(3):284-288

１　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｌｏｃａｌｐｒｅｃｉｐｉｔａｔｉｏｎｉｓｍｏｓｔｉｍｐｏｒｔａｎｔａｖａｉｌａｂｌｅｆｒｅｓｈｗａｔｅｒｓｏｕｒｃｅｉｎｄｅｓｅｒｔｓ．ＴｈｅＴａｋｌｉｍａｋａｎＤｅｓｅｒｔｂｅｌｏｎｇｓｔｏａｎｅｘｔｒｅｍｅａｒｉｄｂｅｌｔ．Ａｃｃｏｒｄｉｎｇｔｏａｆｅｗｙｅａｒｓ’ｌｉｍｉｔｅｄｏｂｓｅｒｖａｔｉｏｎｄａｔａ，ｉｔｉｓｅｓｔｉｍａｔｅｄｔｈａｔｔｈｅｐｒｅｃｉｐｉｔａｔｉｏｎｓｈｏｕｌｄｂｅｉｎｔｈｅｒａｎｇｅｏｆ３０－５０ｍｍａｎｎｕａｌｌｙ．Ｈｏｗｅｖ…  相似文献   

兰州第四纪黄土/古土壤序列物源演变: 来自于碳酸盐矿物的证据^*          下载免费PDF全文

蔡青松  杨光亮  范育新  颜雪域  高敏敏  张青松  王荣华  郭雪莲 《古地理学报》2022,24(3):583-598

黄土/古土壤的物源研究对于揭示第四纪气候变化和青藏高原隆升历史具有重要意义。本研究以位于黄土高原西部1.4 Ma以来的兰州黄土/古土壤沉积序列为研究对象,基于X射线衍射技术分析了黄土/古土壤中的主要矿物组成,侧重于碳酸盐矿物含量,追溯了兰州黄土/古土壤的直接物源。结果显示: (1)1.4 Ma以来兰州地区黄土/古土壤沉积物的主要直接源区为柴达木盆地沙漠区和阿拉善干旱区。(2)基于二元混合模型计算的潜在原始源区对兰州黄土白云石和总碳酸盐矿物的相对贡献率以及长石与石英比值结果一致支持1.4 Ma以来兰州黄土原始物源发生了多次变化。1.4~1.1 Ma和0.9~0.3 Ma青藏高原东北缘造山带(昆仑山、祁连山)和中亚造山带对兰州黄土的贡献相当,而1.1~0.9 Ma和0.3 Ma以来,中亚造山带对兰州黄土的物源贡献增加,这可能分别是对中更新世气候转型和0.3 Ma以来青藏高原及邻近地区干冷气候增强的响应。1.15 Ma和0.8 Ma兰州黄土/古土壤中高的白云石含量、碳酸盐矿物总含量以及0.8 Ma长石与石英比值的快速升高可能是对“昆黄运动”的响应,进而造成了昆仑山、祁连山对黄土高原物源贡献的增加。  相似文献   

Grain‐Size Characteristics of Dune Networks in China's Tengger Desert          下载免费PDF全文

Zhengcai Zhang  Zhibao Dong  Jiyan Li 《Geografiska Annaler: Series A, Physical Geography》2015,97(4):681-693

Grain‐size characteristics of dune networks in the Tengger Desert of northwestern China were investigated. Grain‐size parameters (mean, standard deviation, skew, and kurtosis) were determined on dune surfaces at windward toe, stoss, crest and leeward toe locations. Multiple discriminant analyses were applied to distinguish deposition environments. Results indicated that the aeolian sediment is mainly composed of very fine and fine sand in the dune networks of the Tengger Desert. Sorting improves as grain size becomes finer. However, the relationships between mean grain size, skew, and kurtosis vary in space. There is a negative relationship between skew and sorting; similarly, the relationships between sorting and skew, and skew and kurtosis change in space. The sediment deposition environment includes aeolian sediment and lacustrine sediment. The lacustrine sediment provides the source material for dune windward toe and stoss formation and development, but the aeolian sediment provides the source material for dune crest and leeward toe formation and development. According to the log‐probability of grain size distributions, aeolian sediments in dune networks are composed of two distinct saltation populations.  相似文献   

21世纪初期气候波动下浑善达克沙地荒漠化动态变化分析   总被引：2，自引：1，他引：1  

李春兰  朝鲁门  包玉海  银山  张继权  阿拉腾图雅  包刚  胡日查  罗娟 《干旱区地理》2015,38(3)

基于EOS-MODIS遥感数据,利用GIS计算出归一化植被指数(NDVI)和植被覆盖指数(PV),计算得到荒漠化指数(DI)对浑善达克沙地荒漠化进行识别,根据像元数统计不同荒漠化类型的面积及其变化数据,再分析荒漠化面积与气象要素的相关性,进而得出近13 a在气候波动下浑善达克沙地荒漠化的动态变化。结果表明:浑善达克沙地年平均气温呈下降趋势,年平均降水量呈增加趋势,且平均降水量对荒漠化动态变化的影响比平均气温对荒漠化动态变化的影响大。在气候波动影响下浑善达克沙地以荒漠化面积缩小为主,中度荒漠化,重度荒漠化和极重度荒漠化对荒漠化的演替贡献较大,表现为高程度荒漠化向低程度荒漠化转换。空间分布上,表现为西部极重度荒漠化面积明显减少,主要转化为重度荒漠化类型,东中部重度荒漠化明显减少,主要转化为未荒漠化和轻度荒漠化类型。  相似文献   

Stable isotopic signatures of the modern land snail Eremina desertorum from a low-latitude (hot) dry desert—A study from the Petrified Forest,New Cairo,Egypt     

《Chemie der Erde / Geochemistry》2015,75(1):65-72

This study was conducted on recent desert samples—including (1) soils, (2) plants, (3) the shell, and (4) organic matter from modern specimens of the land snail Eremina desertorum—which were collected at several altitudes (316–360 m above sea level) from a site in the New Cairo Petrified Forest. The soils and shell_{E. desertorum} were analyzed for carbonate composition and isotopic composition (δ¹⁸O, δ¹³C). The plants and organic matter_{E. desertorum} were analyzed for organic carbon content and δ¹³C. The soil carbonate, consisting of calcite plus minor dolomite, has δ¹⁸O values from −3.19 to −1.78‰ and δ¹³C values −1.79 to −0.27‰; covariance between the two values accords with arid climatic conditions. The local plants include C3 and C4 types, with the latter being dominant. Each type has distinctive bulk organic carbon δ¹³C values: −26.51 to −25.36‰ for C3-type, and −13.74 to −12.43‰ for C4-type plants.The carbonate of the shell_{E. desertorum} is composed of aragonite plus minor calcite, with relatively homogenous isotopic compositions (δ¹⁸O_mean = −0.28 ± 0.22‰; δ¹³C_mean = −4.46 ± 0.58‰). Most of the δ¹⁸O values (based on a model for oxygen isotope fractionation in an aragonite-water system) are consistent with evaporated water signatures. The organic matter_{E. desertorum} varies only slightly in bulk organic carbon δ¹³C values (−21.78 ± 1.20‰) and these values suggest that the snail consumed more of C3-type than C4-type plants. The overall offset in δ¹³C values (−17.32‰) observed between shell_{E. desertorum} carbonate and organic matter_{E. desertorum} exceeds the value expected for vegetation input, and implies that 30% of carbon in the shell_{E. desertorum} carbonate comes from the consumption of limestone material.  相似文献   

Groundwater recharge through an alluvial fan in the Atacama Desert,northern Chile: mechanisms,magnitudes and causes     

John Houston 《水文研究》2002,16(15):3019-3035

The Chacarilla fan in the Atacama Desert is one of several formed in the Late Miocene at the foot of the Pre‐Andean Cordillera overlying the large, complex, Pampa Tamarugal aquifer contained in the continental clastic sediments of the fore‐arc basin. The Pampa Tamarugal aquifer is a strategic source of water for northern Chile but there is continuing doubt over the resource magnitude and recharge. During January 2000 a 1 in 4 year storm in the Andes delivered a 34 million m³ flash flood to the fan apex where c. 70% percolated to the underlying aquifers. Groundwater recharge through the fan is calculated to be a minimum of 200 l/s or 6% of the long‐term catchment rainfall. These figures are supported by hydrochemical data that suggest that recharge may be 9% of long‐term rainfall. Isotopic data suggest groundwater less than 50 years old is transmitted westward through the permeable sheetflood sediments of the fan overlying the main aquifer. Analysis of this and other events shows that the hydrological system is non‐linear with positive feedback. The magnitude of groundwater recharge is dependent on climatic variations, antecedent soil moisture storage and changes in channel characteristics. Long‐term declines in groundwater level may partly result from climatic fluctuations and the causes of such fluctuations are discussed. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

The extent of desertification on Saudi Arabia   总被引：2，自引：0，他引：2  

Ammar?A.?AminEmail author 《Environmental Geology》2004,46(1):22-31

Desertification is the process that turns productive deserts into non-productive deserts as a result of poor land-management. Desertification reduces the ability of land to support life, affecting wild species, domestic animals, agricultural crops and humans. The reduction in plant cover that accompanies desertification leads to accelerated soil erosion by wind and water. South Africa is losing approximately 300–400 million tons of topsoil every year. As vegetation cover and soil layer are reduced, rain fall impact and run-off increases. This paper discusses the extent of desertification, its potential threat to sustained irrigated agriculture and possible measures adopted to control ongoing desertification processes to minimize the loss of agricultural productivity in an arid country such as the Kingdom of Saudi Arabia.  相似文献