Remote sensing of atmospheric water vapour from Bhaskara IISAMIR data and its comparison withNOAA-7 water vapour data

Applying the method of ‘statistical linear regression’, atomspheric water vapour over oceanic areas has been estimated from the 19GHz and 22 GHz data of the satellite microwave radiometer (SAMIR) system onboard the Bhaskara II satellite. In the absence of any simultaneousin situ measurements on water vapour over ocean, theSAMIR-derived water vapour data have been compared with like data from theNOAA-7 satellite. It is suggested that a positive bias seen in theSAMIR data could be due to calibration errors in the basic data. In view of the observed bias, the original regression equation is modified and then used to obtain water vapour distributions over ocean for winter and south-west monsoon seasons usingSAMIR data of several orbits.     

Total column ozone retrieval using INSAT-3D sounder in the tropics: A simulation study

The present study examines the potential of infrared sounder observations from Indian geostationary satellite INSAT-3D for the estimation of total column integrated ozone over the tropical Indian region. A dataset with diverse profiles was used to create training and testing datasets using forward simulations from a radiative transfer model for infrared sounder channels. A study was carried out for the standard tropical atmospheric profile to examine the sensitivity of ozone band radiance corresponding to the atmospheric temperature, water vapour, and ozone mixing ratios at different atmospheric pressure levels. Further, statistical retrieval technique has been used for the total column ozone estimation using two different approaches: (i) ozone channel observation along with the a-priori estimate of temperature and water vapour profile and (ii) only sounder channels observations. The accuracy of the retrieval algorithms was examined for different errors in the atmospheric profiles for the method (i) and different sensor noise specification for the method (ii). This study has shown that accurate temperature information is very important for ozone estimation and lower instrument noise results in better ozone estimates.     

The value ofC efor the Arabian Sea during summer monsoon

We estimate, from the moisture budget the bulk aerodynamic coefficient for latent heat flux (C _e) during the monsoon season over the central Arabian Sea. The average value ofC _eunder active monsoon conditions was found to be 2.25 × 10⁻³ which is nearly 60% higher than those previously used.     

Theory and application for retrieval and fusion of spatial and temporal quantitative information from complex natural environment

This paper briefly presents the research progress of the State Major Basic Research Project 2001CB309400, “Theory and Application for Retrieval and Fusion of Spatial and Temporal Quantitative Information from Complex Natural Environment”. Based on the rapid advancement of synthetic aperture radar (SAR) imagery technology, information theory of fully polarimetric scattering and applications in polarimetric SAR remote sensing are developed. To promote the modeling of passive microwave remote sensing, the vector (polarized) radiative transfer theory (VRT) of complex natural media such as inhomogeneous, multi-layered and 3-dimensional VRT is developed. With these theoretical progresses, data validation and retrieval algorithms for some typical events and characteristic parameters of earth terrain surfaces, atmosphere, and oceans from operational and experimental remote sensing satellites are studied. Employing remote sensing, radiative transfer simulation, geographic information systems (GIS), land hydrological process, and data assimilation, the Chinese land data assimilation system (CLDAS) is established. Towards the future development of China’s microwave meteorological satellites, employing remote sensing data of currently available SSM/I (special sensor microwave/imager), AMSU (advanced microwave sounding unit), MTI (microwave temperature imager), etc., with ground-based measurements, several operational algorithms and databases for atmospheric precipitation, water vapor and liquid water in clouds, and other hydrological/hydrological applications are developed. To advance China’s SAR and InSAR (interferometric SAR) technologies, the image processing and analysis of ERS (European remote sensing), Radarsat SAR, and Chinese SAR, etc., the software platforms are accomplished. Based on the researches of multi-information fusion, some simulations, identification, and information extractions of the targets from complex background clutter scenes are studied. Some experiments of radio wave propagation in anomalous atmospheric status are also carried out. Translated from Advances in Earth Science, 2007, 22(2): 111–125 [译自: 地球科学进展]     

HF doppler observations on the occurrence of equatorial spread-F

HF doppler observations of the vertical drift velocity and group height of the 5.5 MHz plasma frequency level of the post-sunset bottomside F-region obtained on a fewESF (equatorial spread-F) and non-ESF days at Trivandrum are presented. The results show that on the non-ESF days, the maximum group height attained is about 400 km and the maximum velocity is less than 30 m/sec. On theESF days, however, the corresponding values are found to be in the range of 400–650 km and 30–50 m/sec. TheESF onset is found to be significantly delayed relative to the velocity peak indicating that it is more closely linked to the layer height than to the drift velocity.     

Rivers, chemical weathering and Earth's climate

We detail the results of recent studies describing and quantifying the large-scale chemical weathering of the main types of continental silicate rocks: granites and basalts. These studies aim at establishing chemical weathering laws for these two lithologies, describing the dependence of chemical weathering on environmental parameters, such as climate and mechanical erosion. As shown within this contribution, such mathematical laws are of primary importance for numerical models calculating the evolution of the partial pressure of atmospheric CO₂ and the Earth climate at geological timescales. The major results can be summarized as follow: (1) weathering of continental basaltic lithologies accounts for about 30% of the total consumption of atmospheric CO₂ through weathering of continental silicate rocks. This is related to their high weatherability (about eight times greater than the granite weatherability); (2) a simple weathering law has been established for basaltic lithologies, giving the consumption of atmospheric CO₂ as a function of regional continental runoff, and mean annual regional temperature; (3) no such simple weathering law can be proposed for granitic lithologies, since the effect of temperature can only be identified for regions displaying high continental runoff; (4) a general law relating mechanical erosion and chemical weathering has been validated on small and large catchments. The consequences of these major advances on the climatic evolution of the Earth are discussed. Particularly, the impacts of the onset of the Deccan trapps and the Himalayan orogeny on the global carbon cycle are reinvestigated. To cite this article: B. Dupré et al., C. R. Geoscience 335 (2003).     

Do we have enough pieces of the jigsaw to integrate CO2 fluxes in the coastal ocean?

Annually integrated air-water CO₂ flux data in 44 coastal environments were compiled from literature. Data were gathered in 8 major ecosystems (inner estuaries, outer estuaries, whole estuarine systems, mangroves, salt marshes, coral reefs, upwelling systems, and open continental shelves), and up-scaled in the first attempt to integrate air-water CO₂ fluxes over the coastal ocean (26×10⁶ km²), taking into account its geographical and ecological diversity. Air-water CO₂ fluxes were then up-scaled in global ocean (362×10⁶ km²) using the present estimates for the coastal ocean and those from Takahashi et al. (2002) for the open ocean (336×10⁶ km²). If estuaries and salt marshes are not taken into consideration in the up-scaling, the coastal ocean behaves as a sink for atmospheric CO₂(−1.17 mol C m⁻² yr⁻¹) and the uptake of atmospheric CO₂ by the global ocean increases by 24% (−1.93 versus −1.56 Pg C yr⁻¹). The inclusion of the coastal ocean increases the estimates of CO₂ uptake by the global ocean by 57% for high latitude areas (−0.44 versus −0.28 Pg C yr⁻¹) and by 15% for temperate latitude areas (−2.36 versus −2.06 Pg C yr⁻¹) At subtropical and tropical latitudes, the contribution from the coastal ocean increases the CO₂ emission to the atmosphere from the global oceam by 13% (0.87 versus 0.77 Pg C yr⁻¹). If estuaries and salt marshes are taken into consideration in the upscaling, the coastal ocean behaves as a source for atmospheric CO₂ (0.38 mol C m⁻² yr⁻¹) and the uptake of atmospheric CO₂ from the global ocean decreases by 12% (−1.44 versus −1.56 Pg C yr⁻¹) At high and subtropical and tropical latitudes, the coastal ocean behaves as a source for atmospheric CO₂ but at temperate latitudes, it still behaves as a moderate CO₂ sink. A rigorous up-scaling of air-water CO₂ fluxes in the coastal ocean is hampered by the poorly constrained estimate of the surface area of inner estuaries. The present estimates clearly indicate the significance of this biogeochemically, highly active region of the biosphere in the global CO₂ cycle.     

A late Holocene paleo-productivity record in the western Gulf of Maine,USA, inferred from growth histories of the long-lived ocean quahog (<Emphasis Type="Italic">Arctica islandica</Emphasis>)

To investigate environmental variability during the late Holocene in the western Gulf of Maine, USA, we collected a 142-year-old living bivalve (Arctica islandica) in 2004, and three fossil A. islandica shells of the Medieval Warm Period (MWP) and late MWP / Little Ice Age (LIA) period (corrected ¹⁴C_AMS = 1030 ± 78 ad; 1320 ± 45 ad; 1357 ± 40 ad) in 1996. We compared the growth record of the modern shell with continuous plankton recorder (CPR) time-series (1961–2003) from the Gulf of Maine. A significant correlation (r ² = 0.55; p < 0.0001) exists between the standardized annual growth index (SGI) of the modern shell and the relative abundance of zooplankton species Calanus finmarchicus. We therefore propose that SGI data from A. islandica is a valid proxy for paleo-productivity of at least one major zooplankton taxa. SGIs from these shells reveal significant periods of 2–6 years (NAO-like) based on wavelet analysis, multitaper method (MTM) analysis and singular spectrum analysis (SSA) during the late Holocene. Based on established physical oceanographic observation in the Gulf of Maine, we suggest that slope water variability coupled with North Atlantic Oscillation (NAO) dynamics is primarily responsible for the observed SGI variability. Special Issue: AGU OS06 special issue “Ocean’s role in climate change—a paleo perspective”.     

Estimation of surface heat flux and inversion height with a Doppler acoustic sounder

In this paper, acoustic sounder (sodar) derived vertical velocity variance (σ _w ² ) and inversion height (Z _i) are used to compute the surface heat flux during the convective activity in the morning hours. The surface heat flux computed by these methods is found to be of the same order of magnitude as that obtained from tower measurements. Inversion heights derived from sodar reflectivity profiles averaged for an hour are compared with those obtained from the σ _w ² /Z profile. Variation of σ _w ² in the mixed layer is discussed. The data were collected during the Monsoon Trough Boundary Layer Experiment 1990 at Kharagpur. The analysis is made for four days which represent the pre-monsoon, onset, active and relatively weak phases of the summer monsoon 1990. The interaction of the ABL with the monsoon activity is studied in terms of the variation of inversion height, vertical velocity variance and surface heat flux as monsoon progresses from June to August.     

Relationship between all-India summer monsoon rainfall and southern oscillation/eastern equatorial Pacific sea surface temperature

The interannual variability of all-India summer monsoon (June to September) rainfall and its teleconnections with the southern oscillation index (SOI) and sea surface temperature (SST) anomaly of the eastern equatorial Pacific ocean have been examined for the period 1871–1978 for different seasons (i.e., winter, spring, summer and autumn). The relationship (correlation coefficient) between all-India summer monsoon rainfall andSOI for different seasons is positive and highly significant. Further examination of 10-, 20- and 30-year sliding window lengths’ correlations, brings out the highly consistent and significant character of the relationships. The relationship between all-India monsoon rainfall andSST for different seasons is negative and is significant at 1 % level or above. Drought years are characterised by negative anomalies ofSOI and positive anomalies ofSST and vice versa with flood years. The relationship betweenSOI andSST is negative and significant at 0.1 % level. The relationships between all-India summer monsoon rainfall,SOI and sst are expected to improve our understanding of the interannual variability of the summer monsoon.     

中国上空的涡动水汽输送

利用1983年国内外149个探空站全年资料,系统地研究了中国大陆上空的涡动水汽输送,包括涡动水汽输送的路径、收支量及其时空分布特点。研究表明,我国夏半年是涡动水汽源地,冬半年是汇地;涡动水汽以春、秋的4、10月最强,30°～40°N间最为活跃;涡动水汽净输送量在华北、西北、东北均超过总输送净量的50%;涡动水汽的经向性十分明显,经由长江流域北界输入北方的涡动水汽量占总输送量的91%强,表明它是把湿润地区暖湿水汽输向干旱、半干旱地区的主要机制,这不仅对北方大气湿度的维持,而且对其降水都有着特殊的贡献。     

Room-temperature equation of state of Li<Subscript>2</Subscript>VOSiO<Subscript>4</Subscript> up to 8.5 GPa

High-pressure single-crystal X-ray diffraction measurements of lattice parameters of the compound Li₂VOSiO₄, which crystallises with a natisite-type structure, has been carried out to a pressure of 8.54(5) GPa at room temperature. Unit-cell volume data were fitted with a second-order Birch-Murnaghan EoS (BM-EoS), simultaneously refining V ₀ and K ₀ using the data weighted by the uncertainties in V. The bulk modulus is K ₀ = 99(1) GPa, with K′ fixed to 4. Refinements of third order equations-of-state yielded values of K′ that did not differ significantly from 4. The compressibility of the unit-cell is strongly anisotropic with the c axis (K ₀(c) = 49.7 ± 0.5 GPa) approximately four times more compressible than the a axis (K ₀(a) = 195 ± 3 GPa).     

Subsurface sequestration of carbon dioxide — an overview from an Alberta (Canada) perspective

To stabilize the atmospheric concentration of greenhouse gases (GHG), a huge reduction of carbon dioxide (CO₂) emissions is required. Although some people believe that this necessitates a considerable reduction in the use of fossil fuels or fuel switching, other options are available that allow the use of fossil fuels and reduce atmospheric emissions of CO₂. Sequestration of CO₂ from fossil fuel combustion in the subsurface could prevent the CO₂ from reaching the surface for millions of years. Geological sequestration of CO₂ in deep aquifers or in depleted oil and gas reservoirs is a mature technology. Despite the huge quantities of CO₂ that can be sequestered in this way, this approach does not provide any economic benefit. This paper discusses a third option, which consists of injecting CO₂ in deep coal seams to sequester the carbon and enhance the recovery of coalbed methane (CBM). Waste CO₂ from CBM-fueled power plants could be injected into CBM reservoirs to produce more methane (CH₄) for the power plant. The 2:1 coal-sorption selectivity for CO₂ over CH₄ supports the feasibility of operating fossil-fueled power plants without atmospheric CO₂ emissions. Other CO₂ sequestration technologies, such as ocean disposal and biofixation, are briefly discussed and the suitability of these approaches is evaluated for use in Alberta, Canada.     

Refinement of the synthetic hydroxyapatite cell parameters

High-precision, computer-refined values of the cell parameters of calcium hydroxyapatite, Ca₁₀(PO₄)₆(OH)₂, have been determined with an X-ray diffractometer, internally standardized by means of sodium chloride. The results obtained are as follows: a ₀=9.4192 Å c ₀/a ₀=0.731 c ₀=6.8867 Å volume=529.2 ų The apatite work was supported by a research grant DE-02105 from the United States Department of Health, Education, and Welfare. I am very grateful to Dr. W. R. Liebenberg, Dr. S. A. Hiemstra and Dr. H. V. R. von Rahden of National Institute for Metallurgy, South Africa for their valuable help and interest and Prof. Nelson Fuson and Prof. James R. Lawson for advice and discussion.     

Influence of moisture transport on stable isotope in precipitation in Yarlungzangbo River basin

The relationship between the variation of δ ¹⁸O in precipitation in Yarlungzangbo River basin and the moisture flux was analyzed with NCEP/NCAR reanalysis grid data and δ ¹⁸O in precipitation at four stations (Lazi, Nugesha, Yangcun and Nuxia) of the region investigated. In terms of spatial variations, there is obviously a positive correlation between them for the entire basin. With the decrease in moisture flux from the downstream to the upstream area, δ ¹⁸O in precipitation became gradually decreased. However, in terms of temporal variations, higher δ ¹⁸O in precipitation during spring is linked to small moisture flux while low δ ¹⁸O in precipitation during summer is linked to large moisture flux. A model involving meteorological data from NCEP/NCAR was subsequently set up which successfully traced the moisture transport trajectories at Yangcun station. Based on the traced moisture transport trajectories and the δ ¹⁸O in precipitation at Yangcun station, the relationship between δ¹⁸O in precipitation in Yarlungzangbo River basin and the moisture transport history was discussed. We found that the humid marine air mass from the Indian Ocean in general has significantly lower δ ¹⁸O values than the continental air mass from the north or local re-evaporation. The fluctuation of δ ¹⁸O in precipitation during the monsoon season is very pronounced; the lower values are usually related to farther distance and multilayer moisture transport, as well as moisture crossing the Himalaya Mountains. __________ Translated from Advances in Earth Science, 2007, 22(8): 842–850 [译自: 地球科学进展]     

The oxygen geochemical cycle: dynamics and stability

The first and possibly only major rise of atmospheric oxygen, from p_O2 ≤ 0.1% PAL (the present atmospheric level) to p_O2 ≥ 10% PAL, appears to have occurred sometime before 2 Ga ago, although the exact time of and the cause(s) for the rise have been hotly debated. Equally important questions on the atmospheric oxygen concern its stability, especially the mechanisms regulating the atmospheric p_O2 level and the causes and magnitude of p_O2 variations since the first major rise of atmospheric oxygen. Previous efforts to model the p_O2 variation during the Phanerozoic time have typically relied on secondary information, such as the carbon and sulfur isotopic records of sedimentary rocks, and on simple dynamics of the geochemical cycles of O, C, S, and P based on box-type models. As a result, many kinetic questions about the variation and stability of atmospheric oxygen could not have been answered. Here we quantitatively evaluate the dynamics and stability of atmospheric O₂ and CO₂, using recent experimental data, field observations, and a new model for the C-O coupled geochemical cycles. We examine the change with time in the fluxes of various compounds (O₂, CO₂, phosphate, organic C, carbonate C, C-bearing reduced volcanic gases, and C-free reduced volcanic gases) among the various reservoirs (atmosphere, soil, surface ocean, deep ocean, the lower crust and mantle, and upper crust) under a variety of scenarios. Our model does not assume steady-state fluxes for any of the reservoirs. Rather, the model incorporates the kinetic experimental data on oxidation of coal, a proxy for kerogen, the dynamics of soil formation and erosion, the kinetics of decomposition of organic matter in the Oceans by aerobic and anaerobic bacteria, the equilibrium ocean-atmosphere carbonate model, the observed relationships among the organic burial flux, dissolved O₂ content of deep ocean, and sedimentation rates, and the three-box model ocean. The important parameters that strongly influence the dynamics of atmospheric O₂, are found to be (a) the total area of soil formation on Earth; (b) the average soil depth; (c) the average rate of physical erosion of soils, which is linked to the average rate of accumulation of clastic sediments in the oceans; (d) the composition and flux of volcanic gas; and (e) the level of atmospheric CO₂. We develop kinetic equations linking these parameters to the production and consumption fluxes of atmospheric oxygen and also to stable p_O2 values. Considering the likely ranges of variations in these parameters in geologic history, we suggest that the atmospheric p_O2 level is likely to have stayed within a very narrow range of 0.6-2 PAL and that the entire ocean, except for local euxinic basins, is likely to have been basically oxygenated since the first major rise of atmospheric oxygen more than 2 Ga ago.     

Tectonic mechanisms associated with P–T paths of regional metamorphism: alternatives to single-cycle thrusting and heating

Metamorphic pressure (P)–temperature (T) paths are commonly used as tools to interpret the tectonic history of orogenic belts, those deformed belts of rocks that record past activity along active plate margins. Many studies and reviews relating P–T path development to tectonics have focused on thrusting–thermal relaxation cycles, with special emphasis on collisional processes. Other studies have assumed that P–T paths resulted from a single tectono-metamorphic event that accounted for the entire burial–exhumation history of the rocks. In many cases, such assumptions may prove invalid.This paper speculates on the relationship of tectonic processes other than thrusting–heating to P–T path development. The processes discussed herein include subduction initiation, triple-junction interactions, initiation and shut off of arc volcanism, subcontinental delamination, and hot spot migration. All of these processes may leave a signature in the metamorphic rock record. Examples are presented from a number of localities, most of which are from the Pacific Rim. Although thrusting–heating cycles have influenced metamorphic evolution in many orogenic belts, the potential impact of other types of tectonic mechanisms should not be overlooked.     

GPS无线电掩星技术监测地球大气

ＧＰＳ无线电掩星技术是从行星掩星（飞行器）探测行星大气^{［１～３］}的遥感技术发展而来的。１９９５年４月３日小型卫星ＭｉｃｒｏＬａｂ１的发射升空，标志着以ＧＰＳ无线电掩星建议为基础ＧＰＳ／ＭＥＴ计划纳入了正式实验阶段。实验结果证实了ＧＰＳ无线电掩星技术在探测地球大气方面潜在的科学价值与实用意义。简要系统地介绍了利用ＧＰＳ无线电掩星技术监测地球大气折射率、温度、气压和水蒸汽丰度等物理参量廓线分布的基本原理、主要误差源和空间分辨率，以及数字模拟结果和初步实验结果，并分析了ＧＰＳ无线电掩星技术在监测全球气候变化和提高数值天气预报精度等方面的潜在贡献。