Jason-1: Assessment of the System Performances     

J. Perbos  P. Escudier  F. Parisot  G. Zaouche  P. Vincent  Y. Menard  F. Manon  G. Kunstmann  D. Royer  L. -L. Fu 《Marine Geodesy》2003,26(3):147-157

On 7 December 2001, Jason-1 was successfully launched by a Boeing Delta II rocket from the Vandenberg Air Force Base, California. The Jason-1 satellite will maintain the high accuracy altimeter service provided since 1992 by TOPEX/Poseidon (T/P), ensuring the continuity in observing and monitoring the Ocean Dynamics (intraseasonal to interannual changes, mean sea level, tides, etc.). Despite one-fourth the mass and power, the Jason-1 system has been designed to have basically the same performance as T/P, measuring sea surface topography at a centimetric level. This new CNES/NASA mission also provides near real-time data for sea state and ocean forecast. The first two months of the Jason-1 mission have been dedicated to the assessment of the overall system. The goals of this assessment phase were:

1. To assess the behavior of the spacecraft at the platform and payload levels (Jason-1 being the first program to call on the PROTEUS versatile multimission platform for Low and Medium Earth Orbit Missions developed in partnership between Alcatel Space and CNES);

2. To verify that platform performance requirements are met with respect to Jason-1 requirements;

3. To verify that payload instruments performance requirements evaluated at instrument level are met;

4. To assess the performance of the Jason-1 Ground System.

This article will display the main outputs of the assessment of the system. It will demonstrate that all the elements of the onboard and ground systems are within the specifications. Provision of data to the Jason-1 Science Working Team started at the end of March 2002. This is the goal of a six-month phase after closure of the initial assessment phase to derive the error budget of the system in terms of altimetry user products.  相似文献   

Seasonal variation of pteropods from the Western Arabian Sea sediment trap     

R. Mohan  K. Verma  L. P. Mergulhao  D. K. Sinha  S. Shanvas  M. V. S. Guptha 《Geo-Marine Letters》2006,26(5):265-273

Sediment trap samples collected from the Western Arabian Sea yielded a rich assemblage of intact and non-living (opaque white) pteropod tests from a water depth of 919 m during January to September 1993. Nine species of pteropods were recorded, all (except one) displaying distinct seasonality in abundance, suggesting their response to changing hydrographical conditions influenced by the summer/winter monsoon cycle. Pteropod fluxes increased during the April–May peak of the intermonsoon, and reached maximum levels in the late phase of the southwest summer monsoon, probably due to the shallowing of the mixed layer depth. This shallowing, coupled with enhanced nutrient availability, provides ideal conditions for pteropod growth, also reflected in corresponding fluctuations in the flux of the foraminifer Globigerina bulloides. Pteropod/planktic foraminifer ratios displayed marked seasonal variations, the values increasing during the warmer months of April and May when planktic foraminiferal fluxes declined. The variation in fluxes of calcium carbonate, organic carbon and biogenic opal show positive correlations with fluxes of pteropods and planktic foraminifers. Calcium carbonate was the main contributor to the total particulate flux, especially during the SW monsoon. In the study area, pteropod flux variations are similar to the other flux patterns, indicating that they, too could be used as a potential tool for palaeoclimatic reconstruction of the recent past.  相似文献   

Transient fluid motion due to the forced horizontal oscillations of a vertical cylinder     

P. McIver 《Applied Ocean Research》1994,16(6):347-351

The problem of the forced horizontal oscillations of a vertical cylinder extending throughout the fluid depth is considered on the basis of the linearised theory of water waves. A new integral form is given for the frequency-domain solution and the procedure is then used to obtain an explicit time-domain solution.  相似文献   

In situ velocity profiles in gassy sediments: Kiel Bay     

S. S. Fu  R. H. Wilkens  L. N. Frazer 《Geo-Marine Letters》1996,16(3):249-253

Acoustic behavior of gas-bearing sediments is significantly different from that of gas-free sediments. In situ velocity profiles and acoustic signal characteristics in gas-bearing sediments of the upper several meters of the sea floor in Kiel Bay are presented in this study. Observed velocities in gas-bearing sediments are both higher and lower than those of the gas-free sediments. Small amounts of gas appear to cause signal reverberation without much attenuation. whereas large amounts of gas cause substantial attenuation.  相似文献   

Seasonal variation of global surface pressure and water vapor   总被引：1，自引：0，他引：1  

TSING-CHANG CHEN  JAU-MING CHEN  SIEGFRIED SCHUBERT  LAWRENCE L. TAKACS 《地球，A辑:动力气象学与海洋学》1997,49(5):613-621

Previous studies have shown that the seasonal variation of global-mean surface pressure ( p _s) results from variation of global-mean water vapor pressure ( p _w). The current study, employing the global data generated by Version 1 of the Goddard Earth Observing System (GEOS-1) Data Assimilation System, shows that seasonal variations of regional p _s and p _w tend to be out of phase (particularly in the subtropics of the two hemispheres) and that the magnitude of the former variation is generally much larger than that of the latter. The seasonal variations of these two quantities are maintained by airmass and water vapor transports by the global divergent circulation, which is driven by the latent heat released by cumulus convection over the water vapor sink, as the "water mass forcing" mechanism predicted. Since p _w and p _s are used often in depicting the climate system, assessments of climate change in terms of the global-mean and regional variations of these two variables should be interpreted with caution.  相似文献   

The Shandong mud wedge and post-glacial sediment accumulation in the Yellow Sea   总被引：14，自引：0，他引：14  

J. P. Liu  J. D. Milliman  S. Gao 《Geo-Marine Letters》2002,21(4):253-254

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Zinc concentration effect at the organismal,cellular and subcellular levels in the eastern oyster     

Meiller JC  Bradley BP 《Marine environmental research》2002,54(3-5):401-404

The purpose of this research was to demonstrate a concentration effect of zinc exposure at organismal, cellular and sub-cellular levels in the eastern oyster and to find associated protein expression signatures (PES) for each concentration of zinc. Oysters were exposed to six concentrations of zinc for 48 h in a controlled environment. At the organismal level, fecal material was observed as a measure of physiological health during metal exposures. At the cellular level, lysosomal destabilization was measured using hemolymph. This cellular response was significant only at the highest concentration, when the fecal index was lowest. Protein responses were monitored in the oyster following exposure to zinc. Gill tissue was excised and homogenized, and then analyzed using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and digital image analysis. Protein expression signatures were found to be specific to each concentration. The protein responses were linked to the other biological parameters measured, each of which followed a concentration gradient of zinc.  相似文献   

The effect of copper pollution on mitochondrial degeneration     

E. Aloj Totaro  F.A. Pisanti  P. Glees  A. Continillo 《Marine environmental research》1986,18(4)

The authors describe the effect of copper pollution on the mitochondria from various areas of the Torpedo marmorata central nervous system. A high percentage of swollen mitochondria has been observed in neurons from animals experimentally exposed to high level of copper (4 ppm). The correlation with age pigment granules is discussed.  相似文献   

Mean current velocity measurement from a movable base     

N. P. Bulgakov  V. I. Remchukov  A. G. Evgushchenko 《Physical Oceanography》1994,5(5):395-399

This paper discusses the possibility of measurement of the current velocity vector characteristics averaged over the time of continuous regular down-up probings from a moving carrier. The measurements can be carried out either from a moving vessel or from a helicopter, floating on or hovering above the sea surface. As an illustration for the suggested technique,in situ observations compiled by a free-component (±XYZ) VEGA-3 probe in the Guiana current region in March 1990 are provided. Comparison of the results with buoy data shows good agreement within the accuracy limits of the instruments employed.Translated by Vladimir A. Puchkin.  相似文献   

Fine structure of the temperature field and the transfrontal exchange in the East Kamchatka current     

I. A. Zhabin  V. P. Tapinov  G. I. Yurasov 《Physical Oceanography》1993,4(1):81-84

CTD data are used to study the relationship between the temperature field fine structure and the location of the frontal zones and synoptic eddies in the region adjacent to the eastern coast of the Kamchatka peninsula. High levels of fine structure activity were observed in the frontal zone of the East Kamchatka current and in the peripheries of anticyclonic eddies. Estimates of the coefficient of the horizontal turbulent exchange and the transfrontal (lateral) heat flux are derived.Translated by Mikhail M. Trufanov.  相似文献