摘要:

A simple theoretical model is developed to describe the steady flow of an estuary onto an adjacent continental shelf. A two‐layer density stratification is assumed for the shelf water, and the fluid motion is driven by the positive (upper layer) and negative (lower layer) mass fluxes associated with a pair of point sources located at the mouth of the estuary. The dynamics are linear and include the effects of Coriolis acceleration, turbulent friction, and bottom topography. Analytic solutions for the one‐layer single‐source problem are found for two special depth profiles. A boundary layer solution is found for the power law depth profileh(y)= αyk, and a global solution is found for the log law profileh(y)=H0[1 + α 1n (y/Lb)] for small α ≪ 1. Both solutions indicate that the far‐field flow is asymmetrically concentrated toward the right‐hand coast in the northern hemisphere, a consequence of the basic balance between topographic vortex stretching and bottom friction. This mechanism also applies when a constant along‐shore current is present. In the two‐layer case the flow in the upper layer generally tends to be concentrated toward the left‐hand coast, since the upper fluid feels (1) the interface and not the bottom topography and (2) the interfacial drag exerted by the lower fluid toward the right‐hand coast. A brief comparison is made between model predictions and observations for the Hudson and Ch

ISSN:0148-0227    

DOI:10.1029/JC083iC02p00873

年代:1978

数据来源: WILEY

摘要:

Models based on stream tube geometry and geostrophy are used to describe the passage of a strong river through a long narrow (fjord‐type) lake. Analysis is specifically applied to the entry of the Thompson River into Kamloops Lake, British Columbia. Lake‐river interaction is considered in three stages of flow: a sinking plume stage during which the incoming river water sinks to a depth where its density matches that of the incoming river, a horizontal spreading stage during which the movement of river water is unconstrained by bottom and/or shoreline effects, and a shorebound stage during which the flow of river water downlake occurs principally in a balance between cross‐stream pressure gradients and the Coriolis force. Exchanges of mass and momentum are parameterized by entrainment and friction coefficients evaluated from field data. Results of this study show, in general, that river‐induced currents influence or even dominate circulation patterns within a fjo

ISSN:0148-0227    

DOI:10.1029/JC083iC02p00885

年代:1978

数据来源: WILEY

摘要:

Expendable bathythermograph observations have revealed large cold core cyclonic current rings to the east of 60°W in a region that mechanical bathythermograph observations (Parker, 1971) indicated to be devoid of rings. As a class these rings are larger than typical Gulf Stream rings that form and drift west of 60°W. The typical diameter (15°C at 500 m) there is around 100 km, while the eastern Sargasso rings are 200 km and more in diameter. Several of these eastern rings were observed on each of four cruises in the northern Sargasso Sea in 1974 and 1975. The overall picture of the region east of 60°W obtained was a very noisy one, dominated by large‐diameter, large‐amplitude eddies. One of the eastern rings was seen in all four cruises and was observed to drift westward for over 730 km at an average speed of 4.4 km/d, starting at 56°30′W and 34°40′N and passing north of Bermuda. The character of the dissolved oxygen anomalies in the cores of the eastern rings suggests a possible formation region at the eastern end of the Sargasso Sea gyre, around 40°W. Hence the eastern rings may have already been a year old when first observed in November 1974. A single deep hydrographic section showed the center of the deep circulation to lie considerably further southwest than the near‐surface circulation center, although this could be a distortion due to a large seamount. Moored current meter data suggest a level of no motion within eastern rings at about 2000 m, giving a weak anticyclonic circulation of 4 × 106m3/s below that level, compared with the 45 × 106m3/s cyclonic circulation above 2000 m. On several occasions, smaller‐scale upward displacements of the thermal structure were seen at the sides of eastern rings. It is not known whether these represented interactions with smaller rings or some breakdown of t

ISSN:0148-0227    

DOI:10.1029/JC083iC02p00901

年代:1978

数据来源: WILEY

摘要:

Various differences and similarities between warm and cold frontogenesis are numerically modeled. The hydrostatic adiabatic Boussinesq primitive equations are integrated on a two‐dimensional grid. The frontogenesis is forced by an along‐front gradient of potential temperature and by a vertically sheared cross‐front wind field. The model develops fronts with the proper vertical circulations, strengths, and slopes; more positive relative vorticity than negative relative vorticity is produced, and the frontal zone at the surface develops in a zone of convergence. Model results indicate that cold fronts will propagate faster than warm fronts and that the fronts will develop on the time scale of 1–3 days. Nonlinear advections brake the frontogenesis for cold fronts in the model and are almost entirely responsible for realistic frontogenesis of warm fronts in the model. Conceptual models of both warm and cold frontogenesis are developed which clarify the origin of the vertical circulation and some of the frontogenesis pr

ISSN:0148-0227    

DOI:10.1029/JC083iC02p00915

年代:1978

数据来源: WILEY

摘要:

High‐resolution gamma ray spectroscopy has been used to obtain214Bi/214Pb specific activity ratios from an extended series of high‐volume air samples taken at a height of 20 m. Afternoon samples exhibited214Bi/214Pb activity ratios that ranged from 0 to 2.5 with a mean value of 0.84 ± 0.04. Morning samples exhibited ratios that ranged from 0 to 1.6 with a mean value of 0.87 ± 0.03. Afternoon samples with ratios greater than 1.0 were associated with southwest winds and214Pb specific activities less than 130 pCi/m3. Morning samples with ratios greater than 1.0 were associated in most cases with southwest winds and with214Pb specific activities less than 220 pCi/m3. Afternoon214Pb specific activity values ranged from 5 to 388 pCi/m3with a mean of 91.7 ± 7.1 pCi/m3. Morning214Pb specific activities ranged from 23 to 664 pCi/m3with a mean of 224.2 ± 20.3 pCi/m3. An improved sampling system used for these measurements reduced the likelihood that observed abnormal activity ratios were artifacts of the sampling pr

ISSN:0148-0227    

DOI:10.1029/JC083iC02p00929

年代:1978

数据来源: WILEY

摘要:

Seventy‐five ground level and six parachute descent grab samples of tropospheric air have been made at a variety of locations throughout the world over a 6‐month period. The N2O mixing ratios in the samples have been determined by electron capture gas chromatography to an absolute accuracy of about 5%, an estimate that is based on the results of several interlaboratory comparisons of calibration standards. The mean ground level N2O mixing ratio from these measurements was 326 ppbv (parts per billion by volume), referenced to ‘dry air,’ and was found to be remarkably constant. The residual standard deviation was 5.3 ppbv. This worldwide mean is consistent with other recent measurements but is considerably larger than many of the earlier measurements. The present data indicate that the N2O residence time in the troposphere is very likely to be greater than 11 years. Furthermore, the data separately show that the possibility of a current annual increase in the N2O mixing ratio by more than 4% seems to be excluded. The parachute descent data, taken just below the tropopause, have a slightly smaller mean, 318 ppbv, but support the contention that the present tropospheric N2O mixing ratio is well above 3

ISSN:0148-0227    

DOI:10.1029/JC083iC02p00935

年代:1978

数据来源: WILEY

摘要:

Meridional profiles of the H2mixing ratio in surface air were obtained by continuous registrations during a ship cruise from Hamburg, West Germany, to Santo Domingo, Dominican Republic, in 1973. Vertical and meridional profiles in the troposphere were measured during a research flight from Cologne, West Germany, to Punta Arenas, Chile, in 1974. The average H2mixing ratio of surface air was 0.582 ± 0.003 ppmv (parts per million by volume) in the northern hemisphere. In the upper troposphere it was found to be 0.561 ± 0.001 ppmv, 1.3% higher than the average of 0.554 ± 0.002 ppmv in the upper troposphere of the southern hemisphere. The horizontal distribution appears to be rather uniform. The vertical profiles also exhibited a rather uniform distribution of H2. However, vertical gradients near the ground were occasionally observed. They are ascribed to strong sources and sinks at the surface. The H2mixing ratio in the lower stratosphere appeared to be slightly higher than that in the troposphe

ISSN:0148-0227    

DOI:10.1029/JC083iC02p00941

年代:1978

数据来源: WILEY

摘要:

The photochemistry of several unreactive and moderately reactive nonmethane hydrocarbons (NMHC) in the background troposphere and stratosphere was investigated. A one‐dimensional steady state model was employed to determine the vertical distributions of C2H6, C2H2, C3H8, C4H10, and C5H12. The impact of these species upon the tropospheric and stratospheric odd‐hydrogen, odd‐oxygen, chlorine, and carbon systems was studied for various possible free radical profiles and eddy diffusion coefficients. Our results indicate that NMHC probably have only a small effect upon the background atmospheric photochemistry, although they might constitute a nonnegligible source of atmospheric CO. Also, Cl atoms, in predicted present‐day concentrations, comprise the major sink for stratospheric NMHC. Finally, if the chlorovinyl molecule (CHCl = CH) were stable in the lower stratosphere, it would then be conceivable that C2H2could be partially effective as a chain terminator to impede catalytic removal of stratospheric O3by Cl

ISSN:0148-0227    

DOI:10.1029/JC083iC02p00947

年代:1978

数据来源: WILEY

摘要:

Analysis of data obtained by the backscatter ultraviolet (BUV) experiment on the Atmosphere Explorer E satellite has provided equatorial ozone mixing ratio profiles for equinox and solstice conditions. The combination of these results with a pure oxygen chemical model yields the rate of odd oxygen loss due to the sum of the odd hydrogen, nitrogen, and chlorine cycles. Use of recent mid‐latitude stratospheric measurements of HOx, NOx, and ClOxwith the BUV data provides an independent calculation of the catalytic loss. Below 45 km the agreement between the two sets of loss rates is satisfactory. At higher altitudes the odd hydrogen cycle provides far more Oxloss than can be tolerated by the BUV measurements if the photodissociation of O2is the only source and has the currently accepted magnitude. The results suggest either a tropical HOxconcentration smaller than is now believed or the presence of a very large source of odd oxygen in the upper stratosphere and lower mesospher

ISSN:0148-0227    

DOI:10.1029/JC083iC02p00953

年代:1978

数据来源: WILEY

摘要:

The Doppler spectrum of high‐frequency radar echoes from the sea consists of dominant peaks due to first‐order Bragg scatter surrounded by a higher‐order continuum. Most applications to date have been based on the first‐order lines, requiring multiple observations and large or moving antennas. In contrast, inversion of the second‐order structure can yield the complete directional ocean wave spectrum from a single radar observation. In this report we describe the first inversion of measured second‐order echo spectra from a 21.75‐MHz narrow‐beam radar looking in a single direction. Estimates of the directional ocean wave spectrum are compared with surface truth provided by tilt buoy and weather station, and fair agreement is found. This initial success is indicative of the potential of this technique for remote sensing of

ISSN:0148-0227    

DOI:10.1029/JC083iC02p00959

年代:1978

数据来源: WILEY