Variability of CO concentrations in the Venus troposphere from Venus Express/VIRTIS using a Band Ratio Technique     

C.C.C. Tsang  F.W. Taylor  S.J. Liddell  G. Piccioni  S.B. Calcutt 《Icarus》2009,201(2):432-443

A fast method is presented for deriving the tropospheric CO concentrations in the Venus atmosphere from near-infrared spectra using the night side 2.3 μm window. This is validated using the spectral fitting techniques of Tsang et al. [Tsang, C.C.C., Irwin, P.G.J., Taylor, F.W., Wilson, C.F., Drossart, P., Piccioni, G., de Kok, R., Lee, C., Calcutt, S.B., and the Venus Express/VIRTIS Team, 2008a. Tropospheric carbon monoxide concentrations and variability on Venus with Venus Express/VIRTIS-M observations. J. Geophys. Res. 113, doi: 10.1029/2008JE003089. E00B08] to show that monitoring CO in the deep atmosphere can be done quickly using large numbers of observations, with minimal effect from cloud and temperature variations. The new method is applied to produce some 1450 zonal mean CO profiles using data from the first eighteen months of operation from the Visible and Infrared Thermal Imaging Spectrometer infrared mapping subsystem (VIRTIS-M-IR) on Venus Express. These results show many significant long- and short-term variations from the mean equator-to-pole increasing trend previously found from earlier Earth- and space-based observations, including a possible North-South dichotomy, with interesting implications for the dynamics and chemistry of the lower atmosphere of Venus.  相似文献   

Analysis of thermal emission from the nightside of Venus at 1.51 and 1.55 μm     

C.F. Wilson  C.C.C. Tsang  F.W. Taylor  S. Erard  P. Drossart  R.C. Holmes 《Icarus》2009,201(2):814-817

We present radiative transfer modelling of thermal emission from the nightside of Venus in two ‘spectral window’ regions at 1.51 and 1.55 μm. The first discovery of these windows, reported by Erard et al. [Erard, S., Drossart, P., Piccioni, G., 2009. J. Geophys. Res. Planets 114, doi:10.1029/2008JE003116. E00B27], was achieved using a principal component analysis of data from the VIRTIS instrument on Venus Express. These windows are spectrally narrow, with a full-width at half-maximum of ∼20 nm, and less bright than the well-known 1.7 and 2.3 μm spectral windows by two orders of magnitude.In this note we present the first radiative transfer analysis of these windows. We conclude that the radiation in these windows originates at an altitude of 20-35 km. As is the case for the other infrared window regions, the brightness of the windows is affected primarily by the optical depth of the overlying clouds; in addition, the 1.51 μm radiance shows a very weak sensitivity to water vapour abundance.  相似文献   

Shear wave velocity modelling in crustal rock for seismic hazard analysis   总被引：2，自引：1，他引：2  

A.M. Chandler  N.T.K. Lam  H.H. Tsang 《Soil Dynamics and Earthquake Engineering》2005,25(2):167-185

P-wave velocity data along with the thickness of sedimentary and crystalline layers within bedrock were collected from all global regions and presented in the Global Crustal Model CRUST2.0, published in 2001. This well-organised database provides invaluable potential contributions towards future seismic hazard modelling, particularly for stable continental regions (SCRs), where there is a scarcity of representative strong motion records for conventional modelling purposes. The P-wave velocity information presented in CRUST2.0 has been converted herein to S-wave velocity information. The latter is especially important for purposes of seismic hazard modelling. The value of the CRUST2.0 model has therefore been greatly enhanced by the important findings presented and further developed in this paper. By making the best use of available information on crustal conditions, the amplification behaviour of seismic waves affecting a region, an area or a site for any given earthquake scenario may be predicted. The developed methodology, which is intended for worldwide applications, has been illustrated by case studies in which model S-wave velocity profiles were developed for different geological regions within North America. The model profiles were found to be in excellent agreement with field measurements reported for each respective region.  相似文献   

Estimating non‐linear site response by single period approximation     

Hing‐Ho Tsang  Adrian M. Chandler  Nelson T. K. Lam 《地震工程与结构动力学》2006,35(9):1053-1076

Site effects characterize the filtering mechanisms within the soil sedimentary layers overlying bedrock. In regions of high seismicity such as California where strong motion records are relatively abundant, site coefficients can be developed by regression of recorded ground shaking parameters. In regions of low‐to‐moderate seismicity or of high seismicity but with a paucity of recorded strong motion data, such empirical models cannot be obtained in the same way. This study describes the theoretical development of a simple, rational manual procedure to calculate site coefficients, based on a single period approximation (SPA), and to construct displacement response spectra (RSD) for soil sites. The proposed simplified model, which takes into account the non‐linear behaviour of soil that is dependent on the level of shaking, impedance contrast at the soil–bedrock interface and the plasticity of soil material, has been verified by comparison with results obtained from non‐linear shear wave analyses and data recorded during the 1994 Northridge earthquake. The proposed model is believed to be a convenient tool for calculating non‐linear site responses and constructing site‐specific response spectra, which has the potential of being incorporated into code provisions. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

A study of caprock hydromechanical changes associated with CO2-injection into a brine formation   总被引：1，自引：0，他引：1  

Jonny Rutqvist  Chin-Fu Tsang 《Environmental Geology》2002,42(2-3):296-305

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Introductory editorial to the special issue on the DECOVALEX-THMC project     

Chin-Fu Tsang 《Environmental Geology》2009,57(6):1217-1219

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A comparative review of hydrologic issues involved in geologic storage of CO<Subscript>2</Subscript> and injection disposal of liquid waste   总被引：1，自引：0，他引：1  

Chin-Fu Tsang  Jens Birkholzer  Jonny Rutqvist 《Environmental Geology》2008,54(8):1723-1737

The paper presents a comparison of hydrologic issues and technical approaches used in deep-well injection and disposal of liquid wastes, and those issues and approaches associated with injection and storage of CO₂ in deep brine formations. These comparisons have been discussed in nine areas: injection well integrity; abandoned well problems; buoyancy effects; multiphase flow effects; heterogeneity and flow channeling; multilayer isolation effects; caprock effectiveness and hydromechanics; site characterization and monitoring; effects of CO₂ storage on groundwater resources. There are considerable similarities, as well as significant differences. Scientifically and technically, these two fields can learn much from each other. The discussions presented in this paper should help to focus on the key scientific issues facing deep injection of fluids. A substantial but by no means exhaustive reference list has been provided for further studies into the subject.  相似文献   

Joint Russian-American hydrogeological-geochemical studies of the Karachai-Mishelyak system, South Urals, Russia     

E. G. Drozhko  Y. U. Glagolenko  Y. G. Mokrov  G. A. Postovalova  L. M. Samsonova  A. V. Glagolev  S. A. Ter-Saakian  M. L. Glinsky  N. A. Vasil'kova  A. V. Skokov  H. A. Wollenberg  C.-F. Tsang  W. Frangos  R. D. Solbau  K. A. Stevenson  W. M. Lowder  M. G. Foley 《Environmental Geology》1997,29(3-4):216-227

 In September 1994, a Russian-American team conducted hydrogeological, geochemical, geophysical, and radiometric measurements in the territory of the Mayak Production Association, Russia. The primary purpose of these operations was to examine the frontal area of a radioelement- and nitrate-laden groundwater plume moving from the disposal site, Lake Karachai, toward the Mishelyak River. Activities encompassed (1) isolation of hydrologic intervals in two wells and production of water from these intervals, to compare isolated versus open-well sampling methods and to determine hydraulic transmissivities of the aquifer(s); (2) surface and soil-water sampling, accompanying radiometric measurements and subsequent chemical analyses; and (3) electrical resistivity profiling in areas of expected contrasting resistivity. Preliminary results indicate that (1) ⁶⁰Co, ¹³⁷Cs, and ⁹⁰Sr are present in small concentrations (∼0.1% of permissible levels) in water of the Mishelyak River; (2) analyses of water samples collected by a downhole sampler and of water produced from packed-off intervals agree within limits of laboratory accuracy, attesting to the efficacy of the sampling methods presently used by the Russian workers; (3) considerable differences in contaminant concentrations exist between nearby wells, supporting the concept that the plume from Lake Karachai toward the Mishelyak River is controlled by steeply dipping fractures and shear zones; and (4) strong contrasts occur between the electrical resistivities of soil and bedrock. Further collaborative work is strongly recommended and should include more detailed isolation of intervals in wells by multi-packer installations, to better determine the geochemical and hydrological characteristics of the Karachai-Mishelyak system; deployment of a broader soil water and soil sampling array; a more detailed examination of the distribution and concentration of radionuclides by high-resolution field gamma spectrometry; and a detailing of the area's electrical resistivity setting, using a mobile electromagnetic measurement system. Received: 22 January 1996 · Accepted: 1 April 1996  相似文献   

Introduction to the Special Issue: "Subsurface flow and transport: from theoretical studies to actions at field sites"     

Chin-Fu Tsang  Vsevolod M. Shestakov 《Environmental Geology》2002,42(2-3):125-126

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Human damage assessments of coastal flooding for Hong Kong and the Pearl River Delta due to climate change-related sea level rise in the twenty-first century     

Yu  Qiwei  Lau  Alexis K. H.  Tsang  Kang T.  Fung  Jimmy C. H. 《Natural Hazards》2018,92(2):1011-1038

Natural Hazards - The adverse impact of climate change-associated extreme weather events is becoming more significant globally, particularly the flood impact on coastal and low-lying areas such as...  相似文献