第二类热成风螺旋度对登陆台风降水的诊断能力分析台风泰利个例研究

文中利用中尺度数值模式MM5模拟了台风泰利的登陆过程,模拟的台风路径、天气形势和降水都与观测基本一致,能够很好地反映出真实的天气过程.再利用数值模拟结果,研究了第二类热成风螺旋度(H_2)对登陆台风泰利降水的诊断能力,结果表明它对深入内陆的台风强降水具有较好的诊断能力,而对刚登陆前后的台风降水诊断能力不如经典螺旋度.特别地,H_2在提前1 h时与泰利降水达到最高相关系数,且在提前1-5 h时,它与降水的相关性比经典螺旋度的高,表现出十分显著的预示降水增幅的能力.进一步分析表明,在刚登陆前后,泰利台风中心850-200 hPa的风场垂直切变较小(约5 m/s),其最强降水出现在路径右侧300 km半径范围以内,与低空的正温度平流、低空辐合、高空辐散等无明显的关系,而低空相对涡度能够很好地反映降水的变化,这是经典螺旋度与降水在这一阶段相关性优于H_2的主要原因.而在深入内陆后,台风泰利本体环流减弱,受北部西风槽的影响逐渐增强,环境风场垂直切变迅速增大,发生强降水的庐山和大别山区处于顺垂直风切变方向左侧.在东北向的垂直风切变情况下,庐山和大别山强降水区上空有向东的高空急流出流,强高空辐散诱发垂直次级环流,从而激发对流,形成强上升运动区,因此H_2的诊断优势在这一阶段表现得最清楚.     

咸淡水过渡带的多组分离子交换行为研究

以大沽河下游海水入侵砂质含水层为研究对象,采集地下淡水、海水和含水介质样品,并测定其组成和性质。通过渗流装置模拟咸淡水驱替过程,测定驱替过程中含水介质的渗透性参数和主要离子的变化规律,并尝试用数值模拟方法定量研究水敏感性影响下的多组分离子交换过程。研究结果表明,海水驱替淡水情况下,Na+能将砂土吸附的Ca2+、Mg2+、K+交换出来,Na+-Ca2+、Na+-K+交换速度很快,而Na+-Mg2+交换反应持续时间较长;在淡水驱替海水的过程中,溶液中的Ca2+、Mg2+将介质吸附的Na+、K+交换出来,但Ca2+-Na+交换起主导作用。含水介质的动力学参数和突破曲线的拐点变化均进一步验证了咸淡过渡带的水敏感性现象,多组分离子的交换行为导致了水敏感现象的发生。     

Petrology, Mineralogy and Geochemisty of Antarctic Mesosiderite GRV 020175: Implications for Its Complex Formation History

<正>GRV 020175 is an Antarctic mesosiderite,containing about 43 vol%silicates and 57 vol% metal.Metal occurs in a variety of textures from irregular large masses,to veins penetrating silicates, and to matrix fine grains.The metallic portion contains kamacite,troilite and minor taenite.Terrestrial weathering is evident as partial replacement of the metal and troilite veins by Fe oxides.Silicate phases exhibit a porphyritic texture with pyroxene,plagioclase,minor silica and rare olivine phenocrysts embedded in a fine-grained groundmass.The matrix is ophitic and consists mainly of pyroxene and plagioclase grains.Some orthopyroxene phenocrysts occur as euhedral crystals with chemical zoning from a magnesian core to a ferroan overgrowth;others are characterized by many fine inclusions of plagioclase composition.Pigeonite has almost inverted to its orthopyroxene host with augite lamellae, enclosed by more magnesian rims.Olivine occurs as subhedral crystals,surrounded by a necklace of tiny chromite grains(about 2-3μm).Plagioclase has a heterogeneous composition without zoning. Pyroxene geothermometry of GRV 020175 gives a peak metamorphic temperature(～1000℃) and a closure temperature(～875℃).Molar Fe/Mn ratios(19-32) of pyroxenes are consistent with mesosiderite pyroxenes(16-35) and most plagioclase compositions(An_(87.5_96.6)) are within the range of mesosiderite plagioclase grains(An_(88-95)).Olivine composition(Fo_(53.8)) is only slightly lower than the range of olivine compositions in mesosiderites(Fo_(55-90)).All petrographic characteristics and chemical compositions of GRV 020175 are consistent with those of mesosiderite and based on its matrix texture and relatively abundant plagioclase,it can be further classified as a type 3A mesosiderite.Mineralogical, penological,and geochemical studies of GRV 020175 imply a complex formation history starting as rapid crystallization from a magma in a lava flow on the surface or as a shallow intrusion.Following primary igneous crystallization,the silicate underwent varying degrees of reheating.It was reheated to 1000℃,followed by rapid cooling to 875℃.Subsequently,metal mixed with silicate,during or after which,reduction of silicates occurred;the reducing agent is likely to have been sulfur.After redox reaction,the sample underwent thermal metamorphism,which produced the corona on the olivine, rims on the inverted pigeonite phenocrysts and overgrowths on the orthopyroxene phenocrysts,and homogenized matrix pyroxenes.Nevertheless,metamorphism was not extensive enough to completely reequilibrate the GRV 020175 materials.     

Study on the geochemical correlation of crude oils of Palaeocene and Jurassic ages from the Potowar Indus Basin in northern Pakistan

This study deals with a detailed geochemical characterization of three crude oils from the Upper Indus Basin, Punjab, Pakistan. The samples were obtained from three productive oil fields of the Datta Formation (Jurassic), Lochhart (Palaeocene) and the Dhak Pass zone (Palaeocene). The GC parameters for and the bulk properties of Datta Formation oils are essentially coincident with those of the oils from the Dhak Pass Formation in the Upper Indus Basin, Pakistan and the oils likely originate from a marine source rock. In contrast, the Lockhart Formation oils show different behaviors and seem to be originated from dirty carbonate rocks although all three crude oils are mature, being of non-biodegraded and somewhat mixed organic matter origin. Low Pr/Ph values and high C₃₅ homohopane index for the Lockhart Formation oils suggest a source of anoxic environment with low Eh while oils from the Datta Formation and Dhak Pass Formation showed different trends, i.e., lower values of C₃₅ homohopane index indicating different depositional environment than oil from the Lockhart Formation. All three crude oils from the Upper Indus Basin are mature for the hopane ratios, i.e., Ts/Ts+Tm, C₃₂22S/(S+R) and C₃₀ αβ/(αβ+βα) and sterane ratios, i.e., C₂₉22S/(S+R) and C₂₉ββ/(ββ+αα) but oils from the Lockhart Formation seem to be less mature than those from the Palaeocene and Datta Formation according to plots like API° vs. homohopane Index, Pr/Ph vs. sterane. The relative composition of 5α(H), 14β(H), 17β(H)-24-ethylecholestanes and the C₂₉20S/20S+20R index, indicate that all three crude oils are equally mature, which makes it unlikely with respect to the above said plots. This difference is may be due to the migratory chromatography which alters the concentrations of sterane and hoapnes and hence gives different results. These oils do not exhibit UCM and have complete n-alkane profiles indicating non-biodegradation.     

南岭燕山期构造-岩浆热事件与锡田锡钨成矿

燕山期发生的与岩石圈减薄和构造转折有关的壳幔相互作用,引起了地球深部能量和物质向浅部的大规模传输,造成了南岭中生代构造-岩浆热事件,从而为成矿作用提供了必需的热、流体、挥发组分和成矿元素,形成了巨量金属堆积的独特地质背景。处于南岭多金属成矿带中段北缘的锡田锡钨成矿区即是在此热事件作用下,形成了云英岩型、似伟晶岩壳型、夕卡岩型、构造蚀变岩型、石英脉型锡、钨多金属矿床。     

The integration of thermal infrared imaging,discharge measurements and numerical simulation to quantify the relative contributions of freshwater inflows to small estuaries in Atlantic Canada

Nutrient fluxes from developed catchments are often a significant factor in the declining water quality and ecological functioning in estuaries. Determining the relative contributions of surface water and groundwater discharge to nutrient‐sensitive estuaries is required because these two pathways may be characterized by different nutrient concentrations and temporal variability, and may thus require different remedial actions. Quantifying the volumetric discharge of groundwater, which may occur via diffuse seepage or springs, remains a significant challenge. In this contribution, the total discharge of freshwater, including groundwater, to two small nutrient‐sensitive estuaries in Prince Edward Island (Canada) is assessed using a unique combination of airborne thermal infrared imaging, direct discharge measurements in streams and shoreline springs, and numerical simulation of groundwater flow. The results of the thermal infrared surveys indicate that groundwater discharge occurs at discrete locations (springs) along the shoreline of both estuaries, which can be attributed to the fractured sandstone bedrock aquifer. The discharge measured at a sub‐set of the springs correlates well with the area of the thermal signal attributed to each discharge location and this information was used to determine the total spring discharge to each estuary. Stream discharge is shown to be the largest volumetric contribution of freshwater to both estuaries (83% for Trout River estuary and 78% for McIntyre Creek estuary); however, groundwater discharge is significant at between 13% and 18% of the total discharge. Comparison of the results from catchment‐scale groundwater flow models and the analysis of spring discharge suggest that diffuse seepage to both estuaries comprises only about 25% of the total groundwater discharge. The methods employed in this research provide a useful framework for determining the relative volumetric contributions of surface water and groundwater to small estuaries and the findings are expected to be relevant to other fractured sandstone coastal catchments in Atlantic Canada. Copyright © 2009 John Wiley & Sons, Ltd.     

Influential factors on the exchange rate of dissolved inorganic nutrients at the sediment-water interface in Jiaozhou Bay, China

Incubation experiments are carried out to study the exchange rates of dissolved inorganic nutrients including silicate, phosphate, ammonium, nitrite, and nitrate (vSiO3-Si, vPO4-P, vNH4-N, vNO2-N and vNO3-N) at the sediment-water interface in the Jiaozhou Bay. Major factors influencing the exchange rates are discussed in detail, which include the dissolved inorganic nutrient concentrations in porewater (Cpw), water and clay contents, and grain size of the sediments (CH2O, Cclay and GSsed). The results may provide insight into the dynamics of nutrient transport and the environmental capacity of nutrients in Jiaozhou Bay, and should be beneficial to solving the problems caused by excessive nutrient input this area.     

两广交界地区花岗岩中包体的类型，特征与成因

据包体岩相学及矿物学研究，包体岩石为角闪岩相到麻粒岩相的副变质岩，岩石类型有麻粒岩，变粒岩，片麻岩和富云包体，角闪岩相包体形成的温度为633度，压力为460Mpa-550MPa，麻粒岩包体形成的温度为781－883度，压力为530MPa-710MPa，包体为部分熔融形成寄主花岗岩岩浆的源区岩石列余，其中大容－十万大山地区角闪岩相－ 麻粒岩相包体岩石为区域动热变质成因；云开大山地区麻粒岩包体岩石为热穹隆变质成因。     

贡嘎山海螺沟冰川物质平衡、水交换特征及其对径流的影响

在贡嗄山海螺沟冰川研究的基础上，提出计算该冰川物质平衡的两种方法，获得了较一致的结果，表明近10a来物质平衡平均为－470mm，与高亚洲边缘山脉的冰种同样处于强烈的衰退状态，该冰川有很高的物质平衡水平（2544mm)及水交换水平（3819mm)，液相比例高（1／3），较小的稳定性系数（0．20），具有典型的季风海洋型冰川的水交换特征，由于冰川退缩冰川径流增加，预计2020年将达到临界状态，在气候持续暖变湿情况下，预测临界状态将延至2050年左右，冰川面积及储量将大幅度减少小。