Global circulation from SEASAT altimeter data     

Theo Engelis 《Marine Geodesy》2013,36(1):45-69

Abstract

A set of time‐averaged sea surface heights at 1° intervals, derived from the adjusted SEASAT altimeter data, and the GEML2 gravity field are used to estimate the long‐wavelength stationary sea surface topography. In order to reduce the leakage of energy in the estimated sea surface topography, the GEML2 field is augmented by the Rapp81 gravity field to generate geoidal undulations with wavelengths consistent with the ones of sea surface heights. These undulations are subtracted from the sea surface heights, and the resulting differences are subjected to filtering in order to recover sea surface topography with minimum wavelengths of 6000 km and an estimated accuracy of 20–25 cm. These estimates agree well with oceanographic and other satellite‐derived results.

The direction of current flow can be computed on a global basis using the spherical harmonic expansion of sea surface topography. This is done not only for the SEASAT/GEML2 estimates, but also using the recent dynamic topography estimates of Levitus. The results of the two solutions are very similar and agree well with the major circulation features of the oceans.  相似文献   

A MODIFIED WEATHER GENERATOR(WGEN)FOR THE GENERATION OF DAILY WEATHER VARIABLES     

Theo Chidiezie Chineke 《Acta Meteorologica Sinica》1997,(3)

Long series of daily weather data are frequently needed to evaluate diachronic climatic impacton water resources,the effects of watershed changes on hydrology and to use in a variety ofweather and general circulation models.A computer generation model called WGEN that wasdeveloped in the United States of America,was modified in this study and applied to Nigerianweather data spanning the period between 1969 to 1988 and covering 17 sites located in thedifferent climatic zones in Nigeria.The model generated the monthly mean maximum and minimumtemperatures,solar radiation,total rainfall,and number of wet and dry days with high accuracy,95% of the times.The Mann-Whitney U-test revealed that the number of months per year forwhich observed and generated weather variables were significant,was less than 4 in majority of thesites.  相似文献   

The African Climate as Predicted by the IAP Grid-Point Nine-Layer Atmospheric General Circulation Model (IAP-9L-AGCM)   总被引：4，自引：3，他引：4  

Chineke Theo Chidiezie  Bi Xunqiang  Wang Huijun  Xue Feng 《大气科学进展》1997,14(3):409-416

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Intercomparison of Two Hydroxyl Radical Measurement Techniques at the Atmosphere Simulation Chamber SAPHIR     

Eric Schlosser  Birger Bohn  Theo Brauers  Hans-Peter Dorn  Hendrik Fuchs  Rolf Häseler  Andreas Hofzumahaus  Frank Holland  Franz Rohrer  Lutz Olaf Rupp  Manfred Siese  Ralf Tillmann  Andreas Wahner 《Journal of Atmospheric Chemistry》2007,56(2):187-205

At the atmosphere simulation chamber SAPHIR in Jülich both Laser-Induced Fluorescence Spectroscopy (LIF) and Long-Path Differential Optical Laser Absorption Spectroscopy (DOAS) are operational for the detection of OH radicals at tropospheric levels. The two different spectroscopic techniques were compared within the controlled environment of SAPHIR based on all simultaneous measurements acquired in 2003 (13 days). Hydroxyl radicals were scavenged by added CO during four of these days in order to experimentally check the calculated precisions at the detection limit. LIF measurements have a higher precision (σ= 0.88×10⁶ cm^–3) and better time resolution (Δt = 60 s), but the DOAS method (σ= 1.24×10⁶ cm^–3, Δt = 135 s) is regarded as primary standard for comparisons because of its good accuracy. A high correlation coefficient of r = 0.95 was found for the whole data set highlighting the advantage of using a simulation chamber. The data set consists of two groups. The first one includes 3 days, where the LIF measurements yield (1 – 2) ×10⁶ cm^–3 higher OH concentrations than observed by the DOAS instrument. The experimental conditions during these days are characterized by increased NO_x concentration and a small dynamic range in OH. Excellent agreement is found within the other group of 6 days. The regression to the combined data of this large group yields unity slope without a significant offset.  相似文献   

The role of antelope trampling on scarp erosion in a hyper-arid environment, Skeleton Coast, Namibia     

Jan Boelhouwers  Theo Scheepers 《Journal of Arid Environments》2004,58(4):9

The role of animal trampling in a hyper-arid environment is evaluated. Field observations on fluvial terraces of the Uniab fan in Namibia suggest that animal impact on level surfaces with gravel armouring is minimal. However, animal trampling along tracks across scarp slopes results in scarp recess and initiate cutback development. With continued growth ephemeral fluvial processes become more dominant and obscure the animal impact. Animal trampling effects are pronounced in hyper-arid environments due to the low rates of other slope processes. However, it is argued that large herd migration may have contributed significantly to cutback development in other environments, especially in Africa, but may be very difficult to substantiate by landform analysis.  相似文献   

Paleomagnetic studies combined with fission-track datings on the western arc of Sulawesi, east Indonesia     

Sadao Sasajima  Susumu Nishimura  Kimio Hirooka  Yoichiro Otofuji  Theo Van Leeuwen  Fred Hehuwat 《Tectonophysics》1980,64(1-2)

Paleomagnetic studies in conjunction with fission-track dating on the western arc of Sulawesi yield important evidence bearing on the tectonic history of the area. During the Paleogene to Early Miocene time interval the paleomagnetic pole for southwestern Sulawesi was situated at 36.5°E 44.8°N. This pole position is significantly different from that in the time interval Middle Miocene to Recent, which is consistent with the north pole of the axial geocentric dipole. This fact suggests that subsequent to the Paleogene to Early Miocene period, possibly 19–13 m.y. B.P., a major tectonic event occurred which caused about 40 degrees of anticlockwise rotation of the area. It is suggested by the present work that the postulated collision followed by welding of eastern Sulawesi with western Sulawesi during the Pliocene (Katili, 1978) may be the tectonic event mentioned above. In addition, our data does not support the hypothesis that western Sulawesi has been derived from the dispersal of Gondwanaland.  相似文献   

The geography of containerization: half a century of revolution,adaptation and diffusion   总被引：1，自引：0，他引：1  

Jean-Paul Rodrigue  Theo Notteboom 《GeoJournal》2009,74(1):1-5

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Late Carboniferous foreland basin formation and Early Carboniferous stretching in Northwestern Europe: inferences from quantitative subsidence analyses in the Netherlands     

Henk Kombrink  Karen A. Leever‡  Jan-Diederik van Wees†  ‡  Frank van Bergen†  Petra David†  Theo E. Wong 《Basin Research》2008,20(3):377-395

The large thickness of Upper Carboniferous strata found in the Netherlands suggests that the area was subject to long-term subsidence. However, the mechanisms responsible for subsidence are not quantified and are poorly known. In the area north of the London Brabant Massif, onshore United Kingdom, subsidence during the Namurian–Westphalian B has been explained by Dinantian rifting, followed by thermal subsidence. In contrast, south and east of the Netherlands, along the southern margin of the Northwest European Carboniferous Basin, flexural subsidence caused the development of a foreland basin. It has been proposed that foreland flexure due to Variscan orogenic loading was also responsible for Late Carboniferous subsidence in the Netherlands. In the first part of this paper, we present a series of modelling results in which the geometry and location of the Variscan foreland basin was calculated on the basis of kinematic reconstructions of the Variscan thrust system. Although several uncertainties exist, it is concluded that most subsidence calculated from well data in the Netherlands cannot be explained by flexural subsidence alone. Therefore, we investigated whether a Dinantian rifting event could adequately explain the observed subsidence by inverse modelling. The results show that if only a Dinantian rifting event is assumed, such as is found in the United Kingdom, a very high palaeowater depth at the end of the Dinantian is required to accommodate the Namurian–Westphalian B sedimentary sequence. To better explain the observed subsidence curves, we propose (1) an additional stretching event during the Namurian and (2) a model incorporating an extra dynamic component, which might well explain the very high wavelength of the observed subsidence compared with the wavelength of the predicted flexural foreland basin.  相似文献   

Variability of residual fluxes of suspended sediment in a multiple tidal-inlet system: the Dutch Wadden Sea     

Maximiliano Sassi  Matias Duran-Matute  Thijs van Kessel  Theo Gerkema 《Ocean Dynamics》2015,65(9-10):1321-1333

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A review of the synthesis and characterisation of pillared clays and related porous materials for cracking of vegetable oils to produce biofuels     

J. Theo Kloprogge  Loc V. Duong  Ray L. Frost 《Environmental Geology》2005,47(7):967-981

This paper presents an overview of the modification of clay minerals by propping apart the clay layers with an inorganic complex. This expanded material is converted into a permanent two-dimensional structure, known as pillared clay or shortly PILC, by thermal treatment. The resulting material exhibits a two-dimensional porous structure with acidic properties comparable to that of zeolites. Synthetic as well as natural smectites serve as precursors for the synthesis of Al, Zr, Ti, Fe, Cr, Ga, V, Si and other pillared clays as well as mixed Fe/Al, Ga/Al, Si/Al, Zr/Al and other mixed metal pillared clays. Biofuels form an interesting renewable energy source, where these porous, catalytically active materials can play an important role in the conversion of vegetable oils, such as canola oil, into biodiesel. Transesterification of vegetable oil is currently the method of choice for conversion to biofuel. The second part of this review focuses on the catalysts and cracking reaction conditions used for the production of biofuel. A distinction has been made in three different vegetable oils as starting materials: canola oil, palm oil and sunflower oil.  相似文献