摘要:

The harmonic method of analyzing and predicting tides was an outstanding scientific accomplishment in the nineteenth century. Except for the building of bigger and better mechanical tide‐predicting machines, procedures were essentially unchanged during the first half of the twentieth century. Cotidal and co‐range charts were empirical, based on observed tides along coastlines and at a few islands. More recently, numerical solutions of Laplace tidal equations have become feasible on newlydeveloped, more powerful computers. Simultaneously, oceanographic engineers have succeeded in measuring tides on the sea floor at great depths. To make pelagic tide data available to the oceanographic community, in particular to those involved in tidal modeling, the IAPSO Advisory Committee on Tides and Mean Sea Level has published a compilation of pelagic tides. The first edition, published in 1979, has harmonic constants for 108 stations, each at least 100 m deep and one nautical mile offshore.

ISSN:0149-0419    

DOI:10.1080/01490418009388000

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The objective of this investigation was to analyze surface circulation patterns in Grays Harbor, Washington, during flood and ebb tide, using National Aeronautics and Space Administration (NASA) aerial photographs and thermal‐IR imagery and low altitude aerial photographs of uranine dye drogues. The application of Landsat‐1 and passive microwave imagery was evaluated but did not prove useful. Water temperature, salinity, and suspended sediment data and the results of hydraulic model studies were used to verify and supplement interpretations from the photographs and imagery. Circulation maps prepared from the thermal imagery were most comparable to circulation patterns observed in the Grays Harbor hydraulic model. The thermal imagery was also useful in mapping nearshore mixing zones and warm water sources, and it showed temperature variations of 4°C between water masses within the harbor and 5–7°C between the water and adjacent tidal flats and land. Current velocities estimated using photographic measurements of sequential dye drogue positions were comparable at some locations to velocities previously measured byin situcurrent meters and in the hydraulic model. The use of remote sensing techniques in conjunction with ground truth data and hydraulic model results, when available, provides a more complete perspective of estuarine processes than is available by using conventional shipboard surveys alone.

ISSN:0149-0419    

DOI:10.1080/01490418009388001

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The U.S. Coast Guard is the United States government agency responsible for providing navigation services to civil and military users in the marine environment. (The environment consists of phases of navigation identified as high seas navigation, coastal and confluence navigation, and harbor and harbor entrance navigation.) This Coast Guard responsibility stems from federal law (14 USC 81), and covers aids to navigation including fixed and floating visual marks (which may carry radar reflectors or radar beacons, sound warning signals) and radio aids to navigation which include marine radiobeacons, Loran‐A, Loran‐C, and OMEGA. The paper provides an update of these radionavigation systems, and takes note of the developing Navigation Satellite Timing and Ranging, Global Positioning System (NAVSTARGPS).

ISSN:0149-0419    

DOI:10.1080/01490418009388002

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

When geoid heights are subtracted from sea surface heights obtained from satellite radar altimetry, the resulting residual heights should measure the exact oceanographic signal which is due to the dynamic processes present. Unfortunately, these results still contain unknown biases due to errors in the determination of the orbits and in the referenced geoidal surfaces. The GEOS‐3 radar altimeter data in the western North Atlantic Ocean area, referenced to two different gravimetric geoids, are used here for this GEOS‐3 Gulf Stream project. Results point out that the orbital errors are not important in the process of extracting the short wavelength oceanic phenomena. Results also indicate that the GEOS‐3 data can be used to correct short wavelength anomalies in gravimetric geoids. These corrections are necessary if sea surface topographies are to be produced.

ISSN:0149-0419    

DOI:10.1080/01490418009388003

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The mean surfaces of several regions of the world's oceans have been estimated using GEOS‐3 altimeter data. Included in these regions are the northwest Atlantic, the northeast Pacific off the coast of California, the Indian Ocean, the southwest Pacific, and the Philippine Sea. These surfaces have been oriented with respect to a common earth center‐of‐mass system by constraining the separate solutions to conform to precisely determined laser reference control orbits. The same reference orbits were used for all regions assuring continuity of the separate solutions. Radial accuracies of the control orbits have been demonstrated to be on the order of 1 m. In the computation of these surfaces, the altimeter‐measured sea surface height crossover differences were minimized by the adjustment of tilt and bias parameters for each pass with the exception of laser reference control passes. The tilt and bias adjustments removed long wavelength errors, which were primarily due to orbit error. Ocean tides were modeled with the (Estes, 1977) global tide model. For comparison purposes the (Mofjeld, 1975) northwest Atlantic tide model was also used for the ocean tide evaluation. The resolution of the estimated sea surfaces varied from 0.25° off the east coast of the United States to about 2° in part of the Indian Ocean near Australia. The rms crossover discrepancy after adjustment varied from 30 cm to 70 cm depending upon geographic location. Comparisons of the altimeter‐derived mean sea surface in the North Atlantic with the 5' × 5' GEM‐8 detailed gravimetric geoid indicated a relative consistency of better than a meter.

ISSN:0149-0419    

DOI:10.1080/01490418009388004

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Ocean tidal signals appear in many geophysical measurements. Geophysicists need realistic tidal models to aid in interpretation of their data. Because of the closeness to resonance of dissipa‐tionless ocean tides, it is difficult for numerical models to correctly represent the actual open ocean tide. As an approximate solution to this problem, test functions derived by solving Laplace's Tidal Equations with ocean loading and self gravitation are used as a basis for least squares dynamic interpolation of coastal and island tidal data for the constituents M2, S2, and K1. The resulting representations of the global tide are stable over at least a ±5% variation in the mean depth of the model basin, and they conserve mass. The paper presents maps of the geocentric tide, the induced free space potential, the induced vertical component of the solid earth tide, and the induced vertical component of the gravitational field for each constituent.

ISSN:0149-0419    

DOI:10.1080/01490418009388005

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The circulation in the Caribbean Sea and Gulf of Mexico exhibits considerable variability, which manifests itself in the form of changes in the intensity and location of the major currents. These changes in current intensity and location are coupled with changes in the distribution of the sea‐surface topography. Little is known of the temporal and spatial distribution of currents in the eastern Caribbean Sea. Recent direct measurements suggest a complicated current structure with large meanders and eddies; such a structure implies a complicated sea‐surface topography. An anticyclonic gyre, characterized by a rise in the sea‐surface topography, is frequently found in the western Caribbean Sea. The gyre is bounded on the south and west by intense currents. Sea‐surface slopes of 0.4m/200km have been observed across the southern limb of the gyre, the Cayman Current, and 0.5m/100km across the western limb, the Yucatan Current. There appears to be a seasonal cycle in the intensity of this gyre, which implies seasonal variability in the slope of the sea surface. The sea surface can slope 0.5m/ 100km across the northern edge of the Loop Current. Similar slopes are observed across the western and eastern edges of this flow, which “loops” into the Gulf of Mexico. The position of the northern edge anl associated sea‐surface slopes can vary from 24°N to 28°N during a cycle of the Loop Current intrusion. When an eddy detaches from the Loop, the topography becomes more complicated. For example, a sea‐surface topography section through an eddy and Loop Current would, within 500 km, rise 0.5m/100km, fall 0.5m/100km, and then rise again the same amount. Although the Loop intrusion cycle appears to occur every year, the phase of events in the cycle varies considerably. Data are presented which show that the phase of a particular event in the Loop Current cycle, such as maximum penetration, can occur during any season.

ISSN:0149-0419    

DOI:10.1080/01490418009388006

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor