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1.
Extraction of surface currents from first-order CODAR sea echo requires use of a model that allows signals from two bearings to contribute to the Doppler spectrum at a given frequency. This is called the dual-angle situation, and it applies over much of the coverage area. Two dual-angle techniques have appeared in the literature: a least-squares algorithm used with a crossed-loop antenna system, and a closed-form approach applied to a four-element square array. We evaluate these methods against realistic signal and noise scenarios encountered in CODAR operations, and study noustatistical biases remaining after infinite-ensemble averaging of the input voltage cross-spectral data. Based on these simulations, biases produced with the closed-form methods exceed those for the crossed-loop system analyzed with least squares by typically 150 percent. 相似文献
2.
We report here on the observation and offline detection of the meteotsunami off the New Jersey coast on June 13, 2013, using coastal radar systems and tide gauges. This work extends the previous observations of tsunamis originating in Japan and Indonesia. The radars observed the meteotsunami 23 km offshore, 47 min before it arrived at the coast. Subsequent observations showed it moving onshore. The neighboring tide gauge height reading provides confirmation of the radar observations near the shore. 相似文献
3.
In this paper we describe the results of a detailed analysis of CODAR measurements made from a single site during the Atlantic Remote Sensing Land Ocean Experiment (ARSLOE). The passage of a storm front generated a surge followed by wind and current reversal, superimposed on the normal semi-diurnal tides. These data have been used previously to illustrate methods for the extraction of surface-current velocities from CODAR data [1]. Here we examine the unique spatial detail provided by CODAR out to 25 km and supported by other instrumentation during this storm. A picture of the water dynamics emerges that is entirely consistent with the physical processes expected over these spatial scales. 相似文献
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5.
Philip H. Heckel ;Aleksandr S. Alekseev ;James E. Barrick ;Darwin R. Boardman ;Natalya V. Goreva ;Tatiana N. Isakova ;Tamara I. Nemyrovska ;Katsumi Ueno ;Elisa Villa ;David M. Work 《《幕》》2008,31(3):319-325
We propose that the level at which the conodont species Idiognathodus simulator (Ellison 1941) (sensu stricto) first appears be selected to mark the base of the Gzhelian Stage, because we believe that this is the optimal level by which this boundary can be correlated. This taxon has a short range and a wide distribution, as shown by correlation of glacial-eustatic cyclothems across the Kasimovian-Gzhelian boundary interval among Midcontinent North America and the Moscow and Donets basins of eastern Europe, based on scale of the cyclothems along with several aspects of biostrati- graphy. Outside of these areas, I. simulator (sensu stricto) is known also from other parts of the U.S., and is reported from the southern Urals and south-central China in its expected position between other widespread taxa. Its first appearance is consistent with the current ammonoid placement of the boundary (first appearance of Shumardites cuyleri), and it is also compatible with certain aspects of the distribution of Eurasian fusulinid faunas (e.g., lectotype ofRauserites rossicus). 相似文献
6.
G. Chen D. Davis J. Crawford B. Heikes D. O'Sullivan M. Lee F. Eisele L. Mauldin D. Tanner J. Collins J. Barrick B. Anderson D. Blake J. Bradshaw S. Sandholm M. Carroll G. Albercook A. Clarke 《Journal of Atmospheric Chemistry》2001,38(3):317-344
Reported are the results from a comparison of OH,H2O2CH3OOH, and O3 observationswithmodel predictions based on current HOx–CH4reaction mechanisms. The field observations are thoserecorded during the NASA GTE field program, PEM-Tropics A. The major focus ofthis paper is on thosedata generated on the NASA P-3B aircraft during a mission flown in the marineboundary layer (MBL) nearChristmas Island, a site located in the central equatorial Pacific (i.e.,2° N, 157° W). Taking advantage of thestability of the southeastern trade-winds, an air parcel was sampled in aLagrangian mode over a significantfraction of a solar day. Analyses of these data revealed excellent agreementbetween model simulated andobserved OH. In addition, the model simulations reproduced the major featuresin the observed diurnalprofiles of H2O2 and CH3OOH. In the case ofO3, the model captured the key observational feature whichinvolved an early morning maximum. An examination of the MBL HOxbudget indicated that the O(1D) + H2Oreaction is the major source of HOx while the major sinks involveboth physical and chemical processes involving the peroxide species,H2O2 and CH3OOH. Overall, the generally goodagreement between modeland observations suggests that our current understanding ofHOx–CH4 chemistry in the tropical MBL isquite good; however, there remains a need to critically examine this chemistrywhen both CH2O and HO2are added to the species measured. 相似文献
7.
HF radar detection of tsunamis 总被引:1,自引:0,他引:1
Belinda J. Lipa Donald E. Barrick John Bourg Bruce B. Nyden 《Journal of Oceanography》2006,62(5):705-716
This paper demonstrates that HF radar systems can be used to detect tsunamis well before their arrival at a coastline. We
solve the equations of motion and continuity on the ocean surface using models to simulate the signals produced by a tsunami
approaching the east U.S. coast. Height and velocity profiles are derived along with expressions for the radar-observed current
velocities in terms of bathymetry and tsunami height and period. Simulated tsunami-generated radial current velocities are
superimposed on typical maps of radial velocity generated by a Rutgers University HF radar system. A detection parameter is
defined and plotted to quantify the progress of the tsunami, which is shown to be detectable well before its arrival at the
coast. We describe observations/warnings that would have been provided by HF radar systems at locations in the path of the
2004 Indian Ocean tsunami. 相似文献
8.
Robert C. Barrick John I. Hedges Michael L. Peterson 《Geochimica et cosmochimica acta》1980,44(9):1349-1362
Hydrocarbon compositions have been determined for 210Pb-dated sediment cores collected at 23 sites within the inland marine waters of northwestern Washington State, U.S.A. Concentrations of total aliphatic hydrocarbons (TAH) and an unresolved complex mixture (UCM) are significantly higher in surface sediments near urban areas than at all other locations with a chronology that indicates a predominantly anthropogenic origin. Concentrations of chromatographically resolvable alkanes are comparatively uniform; the major constituents are plant wax n-alkanes and a naturally-occurring suite of fossil isoprenoid and n-alkanes. Pristane concentrations decrease sharply near the sea-sediment interface suggesting rapid degradation of a plankton-derived component. A saturated multibranched, but nonisoprenoid, C20 hydrocarbon and two novel mono-olefinic analogs have been isolated along with a previously unreported suite for four acyclic multibranched C25 polyenes. Structural and distributional similarities between the C20 and C25 multibranched hydrocarbons suggest that they may be structurally homologous and share a common source. 相似文献
9.
The history of research and development that led to the successful demonstration of the four microwave remote sensing instruments on Seasat (the scatterometer, radiometer, altimeter, and synthetic aperture radar (SAR)) is briefly reviewed in this paper. 相似文献
10.
This paper describes the first reported high-resolution remote measurements of sea-ice velocities during the summer Arctic pack-ice breakup, made with a high-frequency (HF) radar system (CODAR, for Coastal Ocean Dynamics Applications Radar) located on Cross Island, Alaska. Each 36-min observation also gives the positions of the ice edge, the moving ice, and the open water, with an azimuthal and distance resolution of5deg and 1.2 km, respectively, to a range of 15 km. The statistical uncertainties in speed are typically 2-4 cm/s. The ice breakup was observed over a two-day period starting with low ice velocity and no open water and ending with ice and current velocities of approximately 40 cm/s. The position of the ice edge is verified by a simultaneous synthetic aperture radar (SAR) image. To compare the ice, current, and wind velocities, a uniform velocity model was fitted to the measurements of radial velocity. The speed of both ice and current under free drift conditions was found to lie between 2 and 5 percent of the wind speed and the direction within20deg of the wind direction. 相似文献