On the Use of CloudSat and MODIS Data for Estimating Hurricane Intensity   总被引：2，自引：0，他引：2  

Zhengzhao Luo Stephens  G.L. Emanuel  K.A. Vane  D.G. Tourville  N.D. Haynes  J.M. 《Geoscience and Remote Sensing Letters, IEEE》2008,5(1):13-16

This letter presents preliminary results concerning the use of new observations from the A-Train Constellation for testing a new technique of remotely sensing hurricane intensity from space based on modeling a hurricane as a balanced, convectively neutral vortex. The key observational requirements are simultaneous, accurate measurements of cloud-top height, cloudtop temperature, and cloud profiling information across the center of the storm, although there are ways to bypass the need for cloud-top temperature. In this letter, the Moderate Resolution Imaging Spectroradiometer onboard Aqua provides an estimation of the cloud-top temperature, and the near-simultaneous CloudSat observations provide the essential cloud-top height and cloud profiling information. Initial results indicate that the new technique is a promising method for estimating storm intensity when compared post facto to the best track database. Potential uncertainties and room for further refinement of the technique are discussed.  相似文献   

Is the optical image of a non-Lambertian fractal surface fractal?     

Korvin  G. 《Geoscience and Remote Sensing Letters, IEEE》2005,2(4):380-383

This letter generalizes Pentland's result about the fractal dimension of the optical image of rough natural surfaces, without imposing his requirement that the reflection is Lambertian. Instead, it is assumed that the reflectance coefficient is proportional to the focusing/defocusing due to local surface curvature. It will be proved for this case that the density distribution across the optical image inherits the fractal dimension of the mapped surface.  相似文献   

饱和岩石的各向异性及非线性黏弹性响应   总被引：25，自引：2，他引：25       下载免费PDF全文

席道瑛  刘斌  田象燕 《地球物理学报》2002,45(1):109-118

在MTS伺服压机上对不同饱和状态的砂岩、大理岩标本进行了垂直层理和平行层理两个方向的正弦波加载试验,研究了饱和岩石的各向异性及非线性黏弹性行为. 在最大载荷低于岩石的屈服点时,获得的衰减、杨氏模量、泊松比、波速都表现出显著的各向异性,同时它们还具有较明显的应变振幅效应和频率效应. 随着应变振幅的增大,衰减近似呈线性增长,杨氏模量和泊松比近似呈线性下降. 在0.005-4Hz频段内除衰减不明显依赖频率以外,杨氏模量、泊松比、波速对频率的依赖性都较强; 当频段扩大到15Hz时,这4个参数都表现出较强的频率效应. 饱和岩石的衰减、杨氏模量、泊松比、波速均随饱和液体的黏滞系数增大而增大.  相似文献   

Completing the Neogene geological time scale between 8.5 and 12.5 Ma     

《Earth and Planetary Science Letters》2007,253(3-4):340-358

A much improved high-resolution magnetostratigraphy is presented for the interval between 8.5 and 12.5 Ma in the deep marine astronomically tuned Monte dei Corvi Beach section in northern Italy. This section contains the formally designated boundary between the Middle and Upper Miocene defined by the Tortonian GSSP. The natural remanent magnetization is carried by an unusual low-temperature component of primary origin. According to interpretations of isothermal remanent magnetization (IRM) acquisition curves, the palaeomagnetic signal is most probably carried by iron sulphides, such as greigite or pyrrhotite. The resultant magnetostratigraphy is reliable and can be straightforwardly calibrated to the Astronomically Tuned Neogene Time Scale (ATNTS2004) showing that the section ranges from Chron C5An.2n up to C4.2r-1. The inferred correlation of the Tortonian GSSP to the older part of Chron C5r.2n is confirmed, thereby guaranteeing global correlation potential. In addition, the Monte dei Corvi Beach section has been re-tuned to the new numerical solution La2004 for the interval between 8.5 and 12.9 Ma. This exercise shows that the characteristic cycle patterns are not consistent with a single solution with fixed values for dynamical ellipticity and tidal dissipation. For the younger part of the section, sedimentary cycles show an excellent fit with intricate details of precession/obliquity interference in the nominal La2004_(1,1) solution. However, this solution produces serious mismatches between the sedimentary cycles and the precession/obliquity interference in the interval older than ∼ 10.2 Ma. For this interval changes in tidal dissipation value (while keeping dynamical ellipticity constant at its present-day value) are necessary to maintain a perfect fit. A detailed visual comparison reveals a very good to excellent fit with La2004_(1,1.2) and, to lesser extent, with La2004_(1,0.5). However, La2004_(1,1.2) is the preferred tuning target for the moment in the interval older than 10.2 Ma. The astronomical (re)tuning on precessional scale to La2004_(1,1) yielded slightly different astronomical ages for each basic cycle and, hence, also for the calcareous plankton events and magnetic reversal boundaries with uncertainties ranging within a few thousand years. The age of the Tortonian GSSP turns into 11.625 Ma instead of the previously published 11.608 Ma. Our ages should replace existing ages in the Astronomically Tuned Neogene Time Scale (ATNTS2004).  相似文献   

Tectono–Magmatic Evolution and Metallogenesis along the Northeast Jiangxi Deep Fault, China     

Ying Ye  Hidehiko Shimazaki  Masaaki Shimizu  Shouxi Hu 《Resource Geology》1998,48(1):43-50

Abstract: From the southernmost part of Jiangsu province to the northeastern part of Jiangxi province, China, the Northeast Jiangxi Deep Fault runs for about 400 km length with a width of 30 to 40 km. This fault marks the suture zone of two ter-ranes of Proterozoic age. At the both sides of the fault, Yanshanian granitic activity is recognized. That is, the Dexing-Wuyuan porphyry belt on the NW side of the fault, and the Damaoshan-Lingshan granite belt on the SE side. The former activity is characterized by the occurrence of small stocks of granodioritic composition, rich in siderophile elements but poor in LIL elements. No distinct Eu anomaly is recognized in the REE pattern, and a low initial ⁸⁷Sr/⁸⁶Sr ratio is reported. Magnetite, sphene and apatite are observed as accessory minerals. On the contrary, granitic activity on the SE side of the fault is characterized by the occurrence of composite batholiths, in general of granitic to monzogranitic composition, rich in LIL and alkali elements but poor in siderophile and alkali earth elements. A strong Eu anamaly is recognized in the REE pattern, and initial ⁸⁷Sr/⁸⁶Sr ratios are as high as 0. 716. Fluorite, zircon and REE minerals are observed as accessory minerals. These two contrasting granitic activities are refered to as syntexis– and transformation–types, respectively, following the classification commonly used in China, and have similar petrochemical characteristics to those defined for the magnetite– and ilmenite–series, and I– and S-type granitoids. Considering that the above igneous activity occurred far from the supposed subduction zone along the East Coast of China, intracontinental A-type (continent to continent) subduction is proposed to have occurred northwestwards along the NE Jiangxi Deep Fault during Yanshanian time due to a strong compressional stress from SE to NW. A-type subduction introduced the continental slab to some depth, and resulted in the production of the paired granitic activity observed on both sides of the fault. Many mineral deposits are associated with both granitic belts. In the Dexing-Wuyuan porphyry belt, the Dexing porphyry Cu and Yinshan polymetallic deposits are representative, whereas in the Damaoshan-Lingshan granite belt, several tens of rare metal deposits are known such as the Geyuan Nb–Ta–W–Sn deposits. Metal assemblages of those deposits reflect the source materials of magmas in both granitic belts.  相似文献   

Elastic properties of eclogite rocks from the Bohemian massif   总被引：1，自引：0，他引：1  

Vladislav Babuška  Jiří Fiala  D. J. Mayson  R. C. Liebermann  Reviewer J. Buben 《Studia Geophysica et Geodaetica》1978,22(4):348-361

Summary Compressional velocity anistropy has been studied in detail at atmospheric pressure for 78 specimens of 23 types of eclogite rocks from the Bohemian massif. For nine of these rock types, compressional and shear velocities were measured as a function of pressure to750 MPa at room temperature. The velocity anisotropy for both compressional and shear waves is less than4% at high pressure. The velocities increase with increasing garnet content and decrease with increasing symplectitization. The Moldanubian eclogites have significantly higher velocities, on the average, than the eclogites from the Kruné hory crystalline complex, although the densities of both groups are comparable.  相似文献   

Long-term evolution of the aerosol debris cloud produced by the 2009 impact on Jupiter     

A. Sánchez-Lavega  G.S. Orton  R. Hueso  L.N. Fletcher  E. García-Melendo  I. de Pater  H.B. Hammel  A. Simon-Miller  F. Marchis  O. Mousis  J. García-Rojas  M. Cecconi  K. Noll  S. Pedraz  P. Kalas  W. Golisch  P. Sears  V. Reddy  R. Binzel  W. Grundy  J. Emery  A. Rivkin  C. Thomas  D. Trilling  K. Bjorkman  A.J. Burgasser  H. Campins  T.M. Sato  Y. Kasaba  J. Ziffer  R. Mirzoyan  H. Bouy 《Icarus》2011,214(2):462-476

We present a study of the long-term evolution of the cloud of aerosols produced in the atmosphere of Jupiter by the impact of an object on 19 July 2009 (Sánchez-Lavega, A. et al. [2010]. Astrophys. J. 715, L155-L159). The work is based on images obtained during 5 months from the impact to 31 December 2009 taken in visible continuum wavelengths and from 20 July 2009 to 28 May 2010 taken in near-infrared deep hydrogen-methane absorption bands at 2.1-2.3 μm. The impact cloud expanded zonally from ∼5000 km (July 19) to 225,000 km (29 October, about 180° in longitude), remaining meridionally localized within a latitude band from 53.5°S to 61.5°S planetographic latitude. During the first two months after its formation the site showed heterogeneous structure with 500-1000 km sized embedded spots. Later the reflectivity of the debris field became more homogeneous due to clump mergers. The cloud was mainly dispersed in longitude by the dominant zonal winds and their meridional shear, during the initial stages, localized motions may have been induced by thermal perturbation caused by the impact’s energy deposition. The tracking of individual spots within the impact cloud shows that the westward jet at 56.5°S latitude increases its eastward velocity with altitude above the tropopause by 5-10 m s⁻¹. The corresponding vertical wind shear is low, about 1 m s⁻¹ per scale height in agreement with previous thermal wind estimations. We found evidence for discrete localized meridional motions with speeds of 1-2 m s⁻¹. Two numerical models are used to simulate the observed cloud dispersion. One is a pure advection of the aerosols by the winds and their shears. The other uses the EPIC code, a nonlinear calculation of the evolution of the potential vorticity field generated by a heat pulse that simulates the impact. Both models reproduce the observed global structure of the cloud and the dominant zonal dispersion of the aerosols, but not the details of the cloud morphology. The reflectivity of the impact cloud decreased exponentially with a characteristic timescale of 15 days; we can explain this behavior with a radiative transfer model of the cloud optical depth coupled to an advection model of the cloud dispersion by the wind shears. The expected sedimentation time in the stratosphere (altitude levels 5-100 mbar) for the small aerosol particles forming the cloud is 45-200 days, thus aerosols were removed vertically over the long term following their zonal dispersion. No evidence of the cloud was detected 10 months after the impact.  相似文献   

Hydrated minerals on Europa’s surface: An improved look from the Galileo NIMS investigation     

Thomas B. McCord  Gary B. Hansen  Paul Hayne 《Icarus》2010,209(2):639-717

The surface composition of Europa is of great importance for understanding both the internal evolution of Europa and its putative ocean. The Near Infrared Mapping Spectrometer (NIMS) investigation on Galileo observed Europa and the other Galilean satellites from 0.7 to 5.2 μm with spatial resolution down to a few kilometers during flybys by the spacecraft as it orbited Jupiter. These data have been analyzed and results published over the life of the Galileo mission and afterward. One result was the discovery of hydrated minerals at some locations on Europa and Ganymede. The data are noisy, especially for Europa, due to radiation affecting the NIMS electronics and detectors, and other artifacts are also present. The NIMS data are now being reprocessed using the accumulated knowledge gained over the entire missions to remove noise spikes and compensate for some other defects in the data. We are analyzing these reprocessed data in an attempt to defined better the nature of the hydrate spectral features and improve their interpretation. We report here on analyses of two NIMS reprocessed observations for the 0.7-3-μm region. A revised hydrate spectrum is calculated and mapped in detail across two lineaments. The spectrum shows the expected distorted water features but little or no spectral structure in these features. A narrow, weak spectral feature appears at 1.344 μm, which is weakly correlated with lower albedo. Several other weak features may be present but are difficult to confirm in these limited data sets. The hydrate signature shows the greatest strength within and toward the center of the lineaments, confirming and strengthening the association of the hydrate with these endogenic features. This trend may indicate that the material in the lineaments is youngest toward the center and has more water frost coverage toward the edge. A small, visually dark, circular feature has a spectrum that shows both hydrate and crystalline water ice features and perhaps contains a hydrate different in spectral characteristics and perhaps composition than found in the lineament.  相似文献   

Modal mineralogy of CV3 chondrites by X-ray diffraction (PSD-XRD)     

K.T. Howard  G.K. Benedix  P.A. Bland  G. Cressey 《Geochimica et cosmochimica acta》2010,74(17):5084-252

Using position sensitive detector X-ray diffraction (PSD-XRD) we determine a complete modal mineralogy for all phases present in abundances greater than 1 wt% in Vigarano, Efremovka, Mokoia, Grosnaja, Kaba and Allende. Reduced CV3 samples are comprised of (vol%): olivine (83-85%); enstatite (6.5-8.1%); anorthite (1.1-1.2%); magnetite (1.4-1.8%); sulphide (2.4-5.1%); Fe, Ni metal (2-2.2%). The oxidized samples are comprised of: olivine (76.3-83.9%); enstatite (4.8-7.8%); anorthite (1.1-1.7%); magnetite (0.3-6.1%); sulphide (2.9-8.1%); Fe, Ni metal (0.2-1.1%); Fe-oxide (0-2.7%) and phyllosilicate (1.9-4.2%). When our modal data is used to calculate a bulk chemistry that is compared to literature data a near 1:1 correlation is observed. PSD-XRD data indicates that olivine compositions may span almost the entire Fe-Mg solid solution series in all CV samples and that these contain a component (4-13%) of fine-grained olivine that is more Fe-rich (>Fa₆₀) than is typically reported. Modal mineralogy shows that there are mineralogic differences between CV3 samples classified as oxidized and reduced but that these sub-classes are most clearly distinguished by the relative abundance of metal and Ni content of sulphide, rather than abundance of magnetite. The most significant difference in modal mineralogy observed is the relative absence of phyllosilicate in reduced CV that essentially escaped aqueous alteration.Fayalite, ferrous olivine and magnetite are typically considered secondary alteration products. The abundances of these minerals overlap in oxidized and reduced samples and correlate positively supporting common conditions of formation in a relatively oxidizing environment. The abundances of fayalite, ferrous olivine and magnetite show no relationship to petrographic type and if these abundances were used as a proxy for alteration, Allende would be the least altered CV - contrary to all previous data. The implication is that thermal metamorphism on the parent body was de-coupled from formation of Fe-rich secondary minerals. Low temperature fluid-assisted metamorphism can also not easily explain the origin of fayalite, ferrous olivine and magnetite, since the reduced CVs appear to be largely unaffected by this process. Parent body models require an anhydrous low-temperature mechanism of secondary alteration. The alternative is that these phases formed prior to accretion of the final CV parent body.  相似文献   

饱和多孔岩石弛豫衰减对时间和温度的依赖性   总被引：19，自引：4，他引：15  

席道瑛  刘斌  刘卫  易良坤 《地球物理学报》2000,43(6):827-834

通过饱和多孔岩石的低频亚共振试验 ,得到了饱和多孔岩石的内耗峰是典型的弛豫峰的结论 .不同的饱和液体、不同的岩石导致不同的弛豫峰特征 ,饱和岩石的弛豫特性 ,是寻找油田、地热田和预测储层的物性基础 .试验结果表明 ,饱和多孔岩石都具有一个共同的特性---时间和温度的等效性 ,即降低温度与增加振动频率是等效的 ,这就是饱和多孔岩石的弛豫共性 .  相似文献