NUMERICAL SIMULATION OF FRONTOGENESIS FORCED BY DUST RADIATIVE HEATING          下载免费PDF全文

(申绍华)  (陈受钧) 《Acta Meteorologica Sinica》1994,(2)

In this paper,the frontogenesis forced by dust radiative heating and the radiative effects of an isolated duststorrn ona frontal circulation system are examined by means of two-and three-dimensional numerical models.Results indicatethat as a duststorm breaks out, frontogenesis is caused in by dust radiative heating in the lower atmosphere.A markedisentropic potential temperature layer is formed in the middle troposphere.The low-level convergence occurs along thedirection of the front movement.Atnight,dust radiative cooling results in frontolysis in the lower atmosphere.An obvious vertical circulation is forced by radiative heating of an isolated duststorm along the direction of the pre-vailing wind.It is stronger at day,weaker and reverse at night.The response of the horizontal wind field to dust radiativeforcing is different at different levels.  相似文献   

沙盖黄土丘陵坡地土壤理化特性随地形变化规律研究   总被引：2，自引：0，他引：2  

张丽萍  王小云  张赫斯 《地理科学》2011,31(2):178-183

在陕西神木县与内蒙古东胜市交界的饮马泉小流域,选择有代表性的坡面进行地形剖面和土壤层垂直方向的系统采样。每个样品进行了粒级、土壤质量含水量、土壤有机质测试。经数据的分析模拟,得以下结论:①土壤粒级构成和物理性粘粒含量特征,可以指示研究区土壤的沙化程度和演化趋向,其具有向西北更干旱粗化方向过渡的倾向。②土壤水分随地貌部位的变化规律比较明显,在峁坡顶部和上部,垂向上具有自上而下增加的趋势,而在峁坡下部和坡脚却正好相反。不论何种地貌部位都存在一个相近的土壤蒸发、渗漏、持水能力相对的平衡深度。③土壤的物理性粘粒含量与土壤的水肥关系密切,物理性粘粒含量相对高的土壤剖面,土壤的水肥组合效果较好。④土壤水肥质地的组合效果,丘陵顶部的最差,依次过渡到坡脚的组合效果最好。其进一步表明,地貌因素在土壤形成后的一系列熟化、退化、被侵蚀和沙化的演化过程中,地貌仍起着至关重要的作用。  相似文献   

天山乌鲁木齐河源冰川积雪化学特征及其季节变化     

李忠勤  董志文  张明军  王飞腾 《地球科学》2011,36(4):370-678

高海拔雪冰可以记录源自于地球表面的各种化学物质信号.从2002年9月到2005年10月3年的时段内,在天山乌鲁木齐河源1号冰川积累区采集积雪样品,运用比较法、相关分析法等方法,对其中主要离子、不溶粉尘、痕量金属和δ18O等特征及其季节变化进行了分析研究.分析结果表明,积雪离子浓度大小顺序依次为:Ca2+＞SO₄2-＞NO₃-＞Cl-＞NH₄+＞Mg2+＞Na+＞K+,其中Ca2+是主要的阳离子,SO₄2-是主要的阴离子.离子相关性分析表明,除NO₃-之外,其他离子浓度之间均存在较好的正相关.积雪中δ18O值随时间变化表现出与大气温度变化相反的规律.积雪中不溶粉尘和主要化学离子浓度具有明显的季节变化特征,春季期间浓度明显高于其他季节,表明沙尘活动对冰川区化学物质输入有较大贡献;此外,痕量金属(Cd、Pb、Zn、Al、Fe)季节变化特征表明,人类活动的污染物对于研究区雪冰中的化学特征亦有重要影响.   相似文献   

Sedimentary response to volcanic activity in the Okinawa Trough since the last deglaciation     

蒋富清  李安春  李铁刚 《中国海洋湖沼学报》2010,(1)

To investigate the relationship between volcanic activity and sediment record on regional and temporal scales,158 surface sediment samples were collected from the East China Sea Shelf to the northern Okinawa Trough (OT),and two cores recovered in the northern and southern OT,respectively.Mineralogy,grain-size,and geochemical analyses of those samples show that:1) volcanic glass,volcanic-type pyroxene,hypersthenes,and magnetite increase in sediment influenced by volcanic activity;2) sediment grain sizes (and...  相似文献   

Dredging influenced sediment toxicity of endosulfan and lindane on black tiger shrimp （Penaeus monodon Fabricius） in Chantaburi River estuary in Thailand   总被引：2，自引：0，他引：2  

Jayakody Arachchige SUMITH  Preeda PARKPIAN  Napaporn LEADPRATHOM 《国际泥沙研究》2009,24(4):455-464

Series of experiments, including background sediment elutriate, spiked-sediment elutriate and spiked- water toxicity tests, were carried out to study the effect of dredging on survivability and ecological competence of commercially important shrimp postlarvae of Penaeus monodon Fabricius. The test sediment represented the most contaminated from endosulfan and lindane in the Chantaburi river mouth estuary. The maximum sediment contamination levels were 49.4 μg/kg of endosulfan and 58.1 μg/kg of lindane in dry weight basis. Dose-response studies in static, non-renewal spiked-sediment elutriate toxicity tests revealed that LC 50 （96 h） values for survival effect based on measured concentrations were 0.50 （0.26-0.95） μg/L for endosulfan and 0.92 （0.63-1.34） μg/L for lindane. The LOECs for endosulfan and lindane were 0.141 and 0.429 μg/L, respectively. The NOECs were estimated to be the dissoluted endosulfan and lindane concentrations from the Chantaburi estuary sediment. The effects on phenoloxidase enzyme activity in shrimp postlarvae exposed for sub-lethal to lethal doses in sediment elutriate were not significant （p〉0.05） at all tested dose levels. The worst case dissolution concentrations of endosulfan and lindane in the water column upon simulatory dredging in the Chantaburi estuary were found to be toxic to shrimp postlarvae on lethal and sub-lethal effects. The NOECs of respective chemicals （i.e., 0.034 and 0.16 μg/L） shared the same orders of magnitude for corresponding NOECs established for whole salt water aquatic life by the USEPA and ＂safe＂ levels calculated by 0.01 safety factor approach. In addition, the significance of multiple pollutant assessments for ecological toxicity testing is highlighted.  相似文献   

Quantitatively distinguishing sediments from the Yangtze River and the Yellow River using δEu_N-ΣREEs plot     

JIANG FuQing  ZHOU XiaoJing    LI AnChun & LI TieGang Key laboratory of Marine Geology  Environment 《中国科学D辑(英文版)》2009,(2)

Sediment samples were collected from the lower channel of the Yangtze River and the Yellow River and the contents of rare earth elements (REEs) were measured. In addition, some historical REEs data were collected from published literatures. Based on the δEuN-ΣREEs plot, a clear boundary was found be-tween the sediments from the two rivers. The boundary can be described as an orthogonal polynomial equation by ordinary linear regression with sediments from the Yangtze River located above the curve and sedimen...  相似文献   

Using lightning locating system based on time-of-arrival technique to study three-dimensional lightning discharge processes   总被引：2，自引：0，他引：2  

ZHANG GuangShu  WANG YanHui  QIE XiuShu  ZHANG Tong  ZHAO YuXiang    LI YaJun & CAO DongJie Laboratory for Climate Environment  Disasters of Western China  Cold  Arid Regions Environmental  Engineering Research Institute  Chinese Academy of Sciences  Lanzhou  China  Laboratory for Middle Atmosphere  Global Environment Observation 《中国科学:地球科学(英文版)》2010,(4)

A time-of-arrival(TOA) system based on GPS technology for locating VHF radiation sources from lightning has been developed and used in observation sites in the northern Shandong Province,China.The 3D images of the lightning progression have been obtained successfully for the first time in China.The 3D-channel evolutions of typical negative CG,positive CG and IC lightning flashes have been discussed together with the data of fast electric field change.It was found that significant differences existed between the negative and positive CG lightning flashes in terms of the initiation and propagation of the radiation sources.The preliminary breakdown of a negative CG lightning flash propagated at a speed about 5.2×104 m/s.The stepped leader of negative CG lightning flashes was trigged by negative initial breakdown.Thereafter,it propagated downward at a speed of 1.3×105 m/s.The initial process of the positive CG lightning flashes was also a propagation process of negative streamer.These streamers propagated dominantly horizontally in the positive charge region and accumulated positive charges at the origin of the lightning,and as a consequence,initiated downward positive streamers.A new type of lightning discharge that was triggered by a narrow bipolar pulse(NBP) is discussed in this study.The NBP was originated at altitude of about 10.5 km in the upper positive charge region.As a distinct difference from normal IC flash,its channels extended horizontally all around and produced a lot of radiation sources.The source power of the NBP could approach 16.7 kW,which is much greater than that of normal lightning discharge ranging between 100 mW and 500 W.The 3D propagation of this new type of lightning discharge was observed and obtained for the first time in China.The possible initiation mechanism of this new type of light-ning is discussed here.  相似文献   

我国典型海洋型冰川区高海拔区输出水量变化对气候变暖的响应   总被引：2，自引：0，他引：2  

李宗省  何元庆  温煜华  庞洪喜  贾文雄  和献中  蒲焘 《地球科学》2010,35(1):43-50

通过丽江盆地气象水文观测资料研究发现: 冰雪消融加剧、融水增加, 漾弓江流域径流量明显上升; 高海拔冰雪区消融期提前, 春季径流增加明显; 高海拔冰雪区的径流输出对漾弓江流域水量平衡的贡献量逐年增加, 体现了全球气候变暖背景下高海拔冰雪区对整个流域水循环的重要性.对海螺沟流域实测气象水文资料的分析也表明, 气候变暖背景下, 该流域冰雪区水量输出也逐年上升.两流域高海拔区输出水量的剧烈增加, 明显响应了气候变暖, 表明了流域水循环的加速, 这必然将对区域的发展和资源开发产生重要影响.   相似文献   

Seasonal and Spatial Variability of Microparticles in Snowpits on the Tibetan Plateau, China   总被引：1，自引：0，他引：1  

ZHANG Yulana  c  KANG Shichanga  b  ZHANG Qianggonga  CONG Zhiyuana  ZHANG Yongjuna  GAO Tanguanga  ca Laboratory of Tibetan Environment Changes  L  Surface Processes 《山地科学学报》2010,7(1):15-25

The work presents microparticle concentrations in snowpits from the East Rongbuk Glacier on Mt. Qomolangma (Everest) (ER) (28.02°N, 86.96°E, 6536 m a.s.l.), the Zhadang Glacier on Mt. Nyainqentanglha (NQ) (30.47°N, 90.65°E, 5800m a.s.l.), and the Guoqu Glacier on Mt. Geladaindong (GL) (33.95°N, 91.28°E, 5823m a.s.l.) over the Tibetan Plateau (TP). Variations of microparticle and major ions (e.g. Mg2+, Ca2+) concentrations in snowpits show that the values of the microparticles and ions in the non-monsoon seasons are much higher than those in the monsoon seasons. Annual flux of microparticle deposition at ER is lower than those at NQ and GL, which could be attributed to the long distance away from the possible dust source regions as well as the elevation for ER higher than the others. Compared with other remote areas, microparticle concentrations in the southern TP are much lower than those in the northern TP, but still much higher than those in Greenland and Antarctica. The seasonal and spatial microparticle variations are clearly related to the variations of atmospheric circulation according to the air mass 5-day backward trajectory analyses of HYSPLIT Model. Resultingly, the high microparticle values in snow are mainly attributed to the westerlies and the strong dust storm outbreaks on the TP, while the monsoon circulation brings great amount of precipitation from the Indian Ocean, thus reducing in the aerosol concentrations.  相似文献   

中国大陆科学钻探场址区的地壳速度结构特征   总被引：4，自引：0，他引：4  

王有学姜枚  韩国华 《地球科学》2004,29(6):667-673

为了深入研究大别—苏鲁超高压变质带的深部结构及空间展布特征, 进一步揭示该超高压变质形成的动力学过程, 在中国大陆科学钻探场址区进行了广角反射/折射地震测深调查.根据广角反射/折射地震测深的资料研究, 建立了中国大陆科学钻探场址区的地壳纵波速度结构.从纵向上来看, 研究区域的地壳结构可划分为上、中、下3层: 上地壳的速度小于6.2 0km/s, 厚10余km; 中地壳的速度为6.4 0km/s, 厚亦为10km左右; 下地壳的速度为6.6 0km/s.地壳厚度为31km左右, 且其地壳的平均速度为6.30km/s.上地壳中的速度倒转指示了超高压变质体在地壳内部的空间分布, 且超高压变质体在大陆科学钻探场址及其附近的下部呈现为一隆起形态.   相似文献