秦岭地区气溶胶对地形云降水的抑制作用   总被引：12，自引：3，他引：9  

戴进  余兴  Rosenfeld Daniel 《大气科学》2008,32(6):1319-1332

以华山站为影响站, 周围的西安、渭南和华阴作为对比站, 通过影响站与对比站降水之比——地形强化因子(Ro)的变化趋势以及Ro与能见度关系的分析, 定量研究了秦岭地区气溶胶对地形云降水的抑制作用。Ro的演变分析表明: 有观测以来Ro逐年递减, 减幅为14%～20%, 即影响站与对比站相比降水量减少了14%～20%; Ro的减少趋势与能见度递减、气溶胶递增相吻合, 说明气溶胶的增加抑制了地形云降水。Ro的递减主要是减少了中小雨 (日雨量小于30 mm) 的天数, 这种影响对浅薄的生命期较短的地形云降水作用更明显, 对于华山站, 30 mm以下的降水都会受到入云气溶胶的抑制作用, 而西安站为5 mm以下, 入云气溶胶浓度越高, 就有越厚的降水云受气溶胶影响而抑制降水; 在以动力强迫抬升为主的春秋季, 气溶胶抑制华山地形云降水20%左右, 最大可达25%; 在热对流条件下, 气溶胶对地形云和对平原地区云的抑制作用基本相当。不同风速风向下Ro的变化趋势表明, Ro递减随风速增大而加快, 迎风向 (240°～30°) 大风 (≥5 m/s) 时减少降水超过30%。由Ro与能见度关系的定量分析发现, 当能见度在14 km时Ro为1.8左右, 随着能见度的降低Ro逐渐减小, 当能见度小于8 km时,R0约为1.2, 减小了30%左右; 华山对于华阴的Ro与能见度呈线性关系, 相关系数达0.81。最后, 根据研究结果归纳出气溶胶抑制秦岭地区地形云降水的初步物理模型。  相似文献   

基于内涝模型的西安市区强降水内涝成因分析   总被引：7，自引：0，他引：7  

王建鹏  薛春芳  解以扬  金丽娜  薛荣 《气象科技》2008,36(6):772-775

利用西安市近10～40年降水资料、市政信息资料,采用统计学方法,分析了强降水内涝的成因.结果表明:短时强降水或过程量偏大的降水天气过程是引发西安市内涝的直接气象因素;排水能力的强弱是发生内涝关键因素;随着城市化的发展,极端雨强的强度及大于10 mm/h降水的总时次数均有上升趋势,强降水发生概率的提高加强了内涝灾害发生频率及强度,城市效应是内涝加强的主要原因.用西安市强降水内涝仿真模型来进行模拟试验表明:西安是一个内涝发生降水雨强临界值偏低的城市,小时雨强3 mm/h、13 mm/h是发生内涝、严重内涝的临界值,天气预报、雨情监测重点及市政防御关键部位是西北区.总体上缩小井距效果好一些.  相似文献   

浅水湖泊水生植被遥感监测研究进展   总被引：1，自引：0，他引：1  

罗菊花  杨井志成  段洪涛  陆莉蓉  孙喆  辛逸豪 《遥感学报》2022,26(1):68-76

在浅水湖泊中,水生植物具有净化水质、抑制藻类、提供鱼类食物和栖息环境等生态功能,同时,其过度扩张也会加速湖泊淤浅和沼泽化、引起湖泊二次污染等环境负效应.实时动态地掌握湖泊水生植被类群和种群的空间分布及其面积、生物量等指标信息,对湖泊生态修复和评估、水生植被恢复和管理等具有重要现实意义.遥感技术的大面积、实时、动态等特点...  相似文献   

An unusual timing and spectral state of a black hole microquasar XTE J1550-564     

Ying-Kang Jin Shuang-Nan Zhang Ti-Pei Li 《中国天文和天体物理学报》2009,9(2)

An unusual timing and spectral state of a black hole microquasar XTE J1550-564 observed with RXTE is analyzed. Millisecond variabilities are found, which are significantly shorter than the minimum possible time scale in the light curves of black hole binaries, as suggested by Sunyaev & Revnivtsev (2000). The X-ray spectral fitting result indicates that there is an unusual soft component in the spectrum, which may be responsible for the millisecond variabilities. The millisecond variabilities as well as the unusual soft spectral component should be produced from some small, but independent active regions in the accretion disk.  相似文献   

Flare-induced signals in polarization measurements during the X2.6 flare on 2005 January 15     

Meng Zhao  Jing-Xiu Wang  Sarah Matthews  Ming-De Ding  Hui Zhao  Chun-Lan Jin 《中国天文和天体物理学报》2009,9(7)

Flare-induced signals in polarization measurements which were manifested as apparent polarity reversal in magnetograms have been reported since 1981. We are motivated to further quantify the phenomenon by asking two questions: can we distinguish the flare-induced signals from real magnetic changes during flares, and what we can learn about flare energy release from the flare-induced signals? We select the X2.6 flare that occurred on 2005 January 15, for further study. The flare took place in NOAA active re-gion (AR) 10720 at approximately the central meridian, which makes the interpretation of the vector magnetograms less ambiguous. We have identified that flare-induced signals during this flare appeared in six zones. The zones are located within an average distance of 5 Mm from their weight center to the main magnetic neutral line, have an average size of (0.6±0.4)×1017 cm2, duration of 13±4 min, and flux density change of 181±125 G in the area of reversed polarity. The following new facts have been revealed by this study: (1) the flare-induced signal is also seen in the transverse magnetograms but with smaller magnitude, e.g., about 50 G; (2) the flare-induced signal mainly manifests itself as apparent polarity reversal, but the signal starts and ends as a weakening of flux density; (3) The flare-induced signals appear in phase with the peaks of hard X-ray emission as observed by the Ramaty High Energy Solar Spectroscopic lmager (RHESSI), and mostly trace the position of RHESSI hard X-ray footpoint sources. (4) in four zones, it takes place cotemporally with real magnetic changes which persist after the flare. Only for the other two zones does the flux density recover to the pre-flare level immediately after the flare.The physical implications of the flare-induced signal are discussed in view of its relevance to the non-thermal electron precipitation and primary energy release in the flare.  相似文献   

基于TIFF和XML标准的瓦片金字塔模型     

贲进  童晓冲  张衡  丛凤波 《测绘科学技术学报》2005,22(3):184-186

随着数字地球、数字城市研究的深入,多分辨率空间数据模型已成为GIS研究的热点之一,瓦片金字塔作为管理栅格型空间数据的有效手段更得到了广泛应用.文中分析了普通金字塔模型的缺点,在此基础上设计并实现了符合TIFF和XML标准的通用数据模型;通过应用证明了模型的实用价值.  相似文献   

Magnetic susceptibility of ultrahigh pressure eclogite: The role of retrogression   总被引：1，自引：0，他引：1  

Haijun Xu  Zhenmin Jin  Roger Mason 《Tectonophysics》2009,475(2):279-714

Retrograde metamorphism played the dominant role in changing the low-field rock magnetic properties and density of 198 specimens of variably retrograded eclogites from the main borehole of the Chinese Continental Scientific Drilling Project (CCSD) and from surface outcrops in the Donghai area in the southern part of the Sulu UHP belt, China. Bulk magnetic susceptibility (κ) of unretrogressed UHP eclogite is controlled by whole-rock chemical composition and ranges from 397 to 2312 μSI with principal magnetic susceptibility carrying minerals paramagnetic garnet, omphacite, rutile and phengite. Partially retrograded eclogites show large variations in magnetic susceptibility between 804 and 24,277 μSI, with high mean magnetic susceptibility values of 4372 ± 4149 μSI caused by appreciable amounts of Fe-Ti oxide minerals such as magnetite, ilmenite and/or titanohematite produced by retrograde metamorphic reactions. Completely retrograded eclogites have lower susceptibilities of 1094 ± 600 μSI and amphibolite facies mineral assemblages lacking high magnetic susceptibility minerals. Jelínek's corrected anisotropy (P_j) of eclogites ranges from 1.001 to 1.540, and shows a positive correlation with low-field magnetic susceptibility (κ). Arithmetic mean bulk density (ρ) shows a steady decrease from 3.54 ± 0.11 g/cm³ (fresh eclogite) to 2.98 ± 0.06 g/cm³ (completely retrograded eclogite). Retrograde metamorphic changes in mineral composition during exhumation appear to be the major factor causing variations in low field magnetic susceptibility and anisotropy. Retrograde processes must be taken into account when interpreting magnetic surveys and geophysical well logs in UHP metamorphic terranes, and petrophysical properties such as density and low-field magnetic susceptibility could provide a means for semi-quantifying the degree of retrogression of eclogite during exhumation.  相似文献   

胶州湾东北部海域生态环境污染状况研究   总被引：4，自引：1，他引：3  

韩彬  辛明  陈发荣  李培昌  宋转玲  王小如 《岩矿测试》2009,28(6):524-528

根据2004年5月和2005年5月两次对胶州湾东北部海域海水的盐度、pH、溶解氧、化学需氧量、无机氮、活性磷酸盐、铜、铅、锌、镉、多环芳烃和有机氯农药以及表层沉积物中有机碳、石油烃、硫化物、铜、铅、镉、汞、多环芳烃和有机氯农药测定结果,并结合2001年以来历史资料,对胶州湾东北部海域生态环境质量历史变化趋势进行了分析,该海域生态环境中除个别要素如活性磷酸盐、铅、镉、汞等重金属含量有所增加外,其他污染要素含量相对稳定且有下降趋势,2001—2005年该海域生态环境质量相对稳定,仅部分要素有加重趋势。  相似文献   

藏西班公湖斑岩铜矿带成矿斑岩地球化学及Pb、Sr、Nd同位素特征   总被引：9，自引：1，他引：8  

辛洪波  曲晓明  王瑞江  刘鸿飞  赵元艺  黄玮 《矿床地质》2009,28(6):785-792

对班公湖铜矿带2个具有代表性的斑岩铜矿床--多不杂铜矿床和尕尔穷铜矿床进行了详细的岩石地球化学和Pb、Sr、Nd同位素特征研究表明,与冈底斯铜矿带相比,该铜矿带含矿斑岩大离子不相容元素的富集程度相对减弱,而高场强元素和重稀土元素的亏损程度明显减轻,轻、重稀土元素的分馏程度减弱,且具有Eu的弱正异常,岩石在氧化性上更强一些;从Pb、Sr、Nd同位素特征来看,班公湖铜矿带含矿斑岩更富含放射性成因铅,~(143)Nd/~(144)Nd比值明显降低,其源区更接近印度洋沉积物区域,表明该铜矿带含矿斑岩的岩浆源区更浅,有更多的地壳物质加入;班公湖铜矿带含矿斑岩形成的构造环境属于活动大陆边缘区域,而冈底斯铜矿带明显偏离了活动大陆边缘区域,表明班公湖斑岩铜矿带形成于碰撞后地壳隆升阶段,而冈底斯铜矿带则形成于碰撞后地壳伸展阶段.  相似文献   

西藏班公湖岛弧带含硫化镍超基性岩的源区性质与基底背景   总被引：5，自引：1，他引：4  

江军华  王瑞江  曲晓明  辛洪波 《矿床地质》2009,28(6):793-802

青藏高原班公湖一怒江成矿带上的超基性岩型硫化镍矿化是近年来在西藏地区发现的矿化新类型.文章根据成矿带西段班公湖地区含镍超基性岩体的岩石地球化学和Sr、Pb同位素分析结果,论述了含镍超基性岩浆的源区性质及生成条件,并根据锆石U-Pb LA-ICP-MS年龄测定结果,探讨了藏西北地区的基底背景.研究发现,班公湖地区的含镍超基性岩体以富集大离子不相容元素Rb、Th、U、Sr、Pb,亏损Ba、K为特点,高场强元素亏损Nb、Ti,富集Ta;稀士元素相对球粒陨石亏损强烈,但轻稀土元素相对富集.这些特点一致反映出含矿岩浆产生于受俯冲沉积物熔体交代的富集型岩石圈地幔源区.岩浆的生成深度较浅,为尖晶石二辉橄榄岩相,源区部分熔融程度较低,大体在10%左右.岩石中集中出现一批24.79亿年的残留锆石年龄,标志着当时班公湖中特斯洋盆沉积物的物源区较为单一,主要来自太古代末-元古代初的古老基底,并且推测太古代与元古代之交(25亿年)有可能是藏西北的一个古陆壳快速生长期.  相似文献