bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of weak organic acidity in precipitation from remote areas of the world
Authors: Keene William C. , Galloway James N. , Holden J. David
Published: February 2008

The Global Precipitation Chemistry Project collects precipitation by event to determine the composition of precipitation and processes that control it in five remote regions. Ion balances based on major inorganic species revealed consistent anion deficits at certain sites. This and other evidence suggested that weak organic acids contributed to free acidity. Accurate and precise techniques were developed to measure organic anions and total acidity in precipitation. Twelve samples from a remote site were analyzed for major organic and inorganic chemical constituents. Formic and acetic acids were found in all aliquots which had been treated with a biocide. The disappearance of these acids from untreated aliquots corresponded to a proportionate decrease in free acidity. Weak organic acids contributed 64% of free acidity and 63% of total acidity to precipitation during part of the 1981–1982 wet season at Katherine, Australia. Unmeasured proton donors contributed 21% of total acidity during the period.
On the maintenance of the marine boundary layer‐free tropospheric gradient of transient tracers
Authors: Gidel Louis T.
Published: February 2008

A steady state budget for trace gases in the marine boundary layer is developed from a simple model of the marine boundary layer. Tracer balance is maintained in the marine boundary layer by five processes: (1) large‐scale horizontal convergence of tracer, (2) pumping of tracer out of the marine boundary layer into the free troposphere by clouds, (3) penetration of tracer from the free troposphere into the marine boundary from compensating subsidence in the cloud free air surrounding cumulus clouds, (4) sea surface emission or deposition of the tracer, and (5) in situ photochemical production or loss of tracer within the marine boundary layer. The budget equation is used to derive an expression for the mixing ratio difference between the marine boundary layer and the free troposphere. Cumulus cloud mass flux is found to modulate all other processes that determine the mixing ratio difference between the two regions. A scale analysis indicates that the mixing ratio difference between the marine boundary layer and the free troposphere can be an order of magnitude smaller in disturbed weather conditions when compared with suppressed conditions showing that the difference in chemical concentrations between the free troposphere and the marine boundary layer cannot be rationalized solely on the basis of chemical measurements. The O3 measurements made during GAMETAG (Global Atmospheric Measurements Experiment on Tropospheric Aerosols and Gases) in the marine boundary layer are discussed in the context of the model. Finally, the analysis shows how sea surface emission rates of CH3I, CH3SCH3, H2S, and other reduced sulfur species can be estimated from measurement of the boundary layer‐free troposphere concentration difference combined with measurements of the mass flux deduced from heat and moisture budget by using rawinsonde data. The approach is an alternative to the use of thin film models to estimate sea surface emission rates.
High‐latitude stratospheric winds near summer solstice: The diurnal and semidiurnal solar tides
Authors: D'Angelo N. , Neubert T. , Iversen I. B. , Madsen M. M.
Published: February 2008

A technique for studying winds and tides at altitudes of approximately 30 km is the continuous and precise tracking of zero‐pressure, stratospheric balloons. The CONSOL navigation system allows tracking of a balloon over the North Atlantic for two days or longer. Tidal wind data from 14 balloon trajectories (approximately 670 balloon hours) are presented and compared with theoretical predictions.
Radiative properties of the stratospheric dust cloud from the May 18, 1980, eruption of Mount St. Helens
Authors: DeLuisi John J. , Mendonca Bernard G. , Dutton Ellsworth G. , Box Michael A. , Herman Benjamin M.
Published: February 2008

Measurements of the 2π‐sr (hemispheric) diffuse‐sky, direct, and total (diffuse and direct) transmitted solar flux were made at Boulder, Colorado, during the passage of the Mount St. Helens dust cloud on May 19 and June 3, 1980. The measurements were both narrow‐band and broadband integrated over the solar spectrum. Verification of the presence of the cloud and its vertical profile was obtained by lidar. Analysis of the flux measurements by a perturbation technique yielded volcanic cloud optical properties useful for studies of climate variation. The ratio of backscatter to total scatter, imaginary term of the complex refractive index, albedo of single scatter, and optical depth are determined from the measurements. Estimates of solar radiation absorption and backward and forward scattering by the cloud are given. Certain radiative characteristics of the Agung volcanic cloud and the Mount St. Helens volcanic cloud are compared.
Transport of mineral aerosol from Asia Over the North Pacific Ocean
Authors: Uematsu Mitsuo , Duce Robert A. , Prospero Joseph M. , Chen Liqi , Merrill John T. , McDonald Ray L.
Published: February 2008

Concentrations of atmospheric aluminum—a good indicator of mineral aerosol—have been measured weekly, between January 1981 and March 1982, at the seven stations of the SEAREX Asian Dust Network in the North Pacific. A seasonal transport pattern was found at most of the sites, with high Al concentrations from February to June and low concentrations from July to January. There was a latitudinal gradient in the mean annual atmospheric dust concentration, with the greatest concentrations occurring in the mid‐latitudes. When coupled with statistics of dust storms in Asia and of Kosa (dense dust hazes traced to Chinese origins) in Japan, the data suggest that the dust collected in the network was transported by the westerlies from arid regions in Asia. It is estimated that 6–12×106 tons of Asian dust are transported annually to the central North Pacific; larger quantities are probably deposited over the western North Pacific, closer to the Asian sources. This atmospherically transported mineral aerosol is a significant source of sedimentary material for the North Pacific.
Himalayan winter snow cover area and summer monsoon rainfall over India
Authors: Dey B. , Kumar O. S. R. U. Bhanu
Published: February 2008

The study presented in this paper examines the relationship between satellite‐derived Himalayan snow cover extent in the winter season (December to March) and the amount of summer monsoon rainfall for the period 1971 to 1980. Himalayan snow cover area has been derived from satellite images and northern hemisphere snow cover charts produced by the National Oceanic and Atmospheric Administration‐National Environmental Satellite Service. Indian summer monsoon rainfall was the area‐weighted mean of all meteorological subdivisions of India for the months June through September. The variations of Indian summer monsoon rainfall were compared with the variation of the Himalayan winter snow cover area. There is an inverse relationship (negative correlation) between these two variables, which indicates that more than mean Himalayan winter snow cover area is to be followed by less than normal (India Meteorological Department (IMD)) summer monsoon rainfall over India. The inverse relationships hold true for 8 out of 10 years of the study period. The coefficients of correlation between the Himalayan snow cover area departures from the 10‐year mean and the rainfall departures from IMD normals for all the meteorological subdivisions of India were computed. The negative correlations were found to be maximum in the region between 18°N latitude and the foothills of the Himalayas.
Theory of metamorphism of dry snow
Authors: Colbeck S. C.
Published: February 2008

The growth of ice particles in dry seasonal snow is caused by vapor diffusion among particles due to temperature gradients imposed on the snow cover. The diffusion is calculated by using the potential field solutions for electrostatically charged particles. The stereography of snow is represented by using a log‐normal distribution function for a geometrical enhancement factor defined here. Reasonable crystal growth rates and supersaturations are found. The transition between the growth of highly faceted crystals and the growth of highly rounded crystals is determined by the critical supersaturation for the onset of dislocation aided growth. Thermal convection and the continuous movement of vapor around the particles due to the imposed temperature gradient are accommodated in the theory, although both have little effect relative to the interparticle diffusion. The growth of a layer of faceted crystals just below semi‐permeable crusts is explained by showing that crusts can cause the local supersaturation to exceed the critical value. Faceted crystals are shown to grow most rapidly in the lower, warmer portions of the snow cover because of temperature effects on growth rate.
Surface mixed layer temperature and layer depth in water off the Argentinian Coast
Authors: Blanc Silvia , Goñi Gustavo , Novarini Jorge
Published: February 2008

Analysis of 26 years of bathythermographic data is used to describe the connection between the sea surface temperature and the layer depth in the western South Atlantic, off the Argentinian coast. The area is influenced by the presence of two water masses, subtropical waters and subantarctic waters. A seasonal analysis was carried out for 5° squares. The plotting of mixed layer depth versus surface temperature provides two types of patterns. Evidence suggests that they might be related to the presence of each of the above‐mentioned water masses. A clear relationship was found for data distribution in each subarea. The exponential function L = a exp (‐bTs) was found to fit best the dependence of the mixed layer depth (L) on the surface temperature (Ts). Very defferent ranges were empirically found for the real constants a and b depending on the predominant water mass in each subarea.
Estimating the solar zenith dependence of the clear‐sky planetary albedo for land surfaces from the GOES satellite
Authors: Pinker R. T. , Razgaitis J. A.
Published: February 2008

The diurnal variation in the albedo of natural surfaces has been well established from close‐to‐ground observations. To document similar variation from satellite observations is more complicated because of a lack of relevant information. In this study a unique data base, obtained from an experiment in 1977 over the Great Plains, was utilized. Images from the visible channel(0.55–0.75 μm) of the GOES‐E/VISSR radiometer averaged over 50×50 km2 target areas were collected and screened for ‘clear sky’ cases. This subset of clear brightness radiances was used over 33 targets in the Great Plains to document the solar zenith dependence of the planetary albedo from the geostationary satellite. This information is also indicative of the surface albedo zenith dependence.
Physical aspects of a length scale for the Gulf Stream Front
Authors: Kao Timothy W.
Published: February 2008

A discussion is presented of the physical interpretation of the length scale, λ, introduced in a recent paper by Kao and Cheney (1982) to scale the sea surface height anomaly across the Gulf Stream front. Additional results of sea‐surface height anomaly profiles computed from the hydrographic data from Fuglister's GULF STREAM 60 are also included. In all cases the width of the anomaly is spanned rather precisely by 2λ. The relationship between λ and the internal Rossby radius of deformation λs is discussed.
Tides in the Bay of Bengal
Authors: Murty T. S. , Henry R. F.
Published: February 2008

The amplitudes and phases of the tidal constituents M2, S2, K1, and O1 in the Bay of Bengal are deduced from tide gauge records at 112 locations with the aid of numerical models based on the vertically integrated equations of motion and continuity. Tidal elevations along the southern open boundary of the bay were obtained by interpolation from observations. The results are presented in the form of cotidal charts. These show that the constituents examined have no amphidromic points in the Bay of Bengal apart from a degenerate amphidrome for M2 in the northwest part of the bay.
Factors influencing the loss of fertilizer nitrogen into the atmosphere as N2O
Authors: Conrad R. , Seiler W. , Bunse G.
Published: February 2008

In 1979–1981, experiments were carried out at four field stations near Mainz, Germany, to determine the loss of fertilizer nitrogen into the atmosphere as N2O. Evolution rates from the soil into the atmosphere were measured by using the closed chamber technique. An automatic sampling and analyzing device was developed which allowed frequent determinations of N2O evolution rates (one every 1.5 hours). The N2O production rates were correlated to the surface soil temperature according to the Arrhenius equation and showed a diurnal rhythm with amplitudes reaching, sometimes, 1 order of magnitude. It seems that most of the N2O emitted into the atmosphere is produced in the uppermost soil layer. N2O evolution was stimulated by rain and increased with increasing soil moisture content. Application of fertilizer caused a dramatic increase of N2O evolution rates with values up to 1000 μg N2O–N m−2 h−1. The magnitude of the fertilizer‐induced N2O evolution rates was dependent on the type, the application form, and the amount of fertilizer used. The total loss of fertilizer nitrogen as N2O was in the range of 0.001 to 0.94%.Based on these figures, as well as on data from the literature, the total source strength of mineral fertilizers for atmospheric N2O is calculated to 0.02 to 8 Tg N2O–N yr−1.
The near‐surface circulation of the North Pacific using satellite tracked drifting buoys
Authors: McNally Gerard J. , Patzert William C. , Kirwan A. D. , Vastano Andrew C.
Published: February 2008

The trajectories of 16 satellite‐tracked drifting buoys from February 1976 through May 1980 and their derived velocities are used to construct a Lagrangian realization of the near‐surface circulation of the North Pacific subtropical gyre. A composite transit time around the periphery of this gyre is approximately 4.5 years at an average speed of 15 cm s−1. The details of the surface flow indicated regional differences in mesoscale energetics. Flow variability is low in the eastern and high in the western portions of the northern limb of the gyre. The highest mean speeds and minimum variances are found in the tropical currents of the southern limb. The drifter data is compared with the climatological mean field of dynamic topography (0/500 dbar). This comparison shows significant differences between drifter movement and inferred geostrophic flow. In the eastern mid‐latitude region the direction of the drifter motion and dynamic topography is in good agreement; however, the drifter speeds are 5 times greater. In the eastern and southern branches of the gyre, the current magnitudes of the drifters and geostrophic flow are comparable but their directions diverge. Comparison of the drifter trajectories and climatological seasonal sea level pressure maps reveal that the trajectory departures from the dynamic topography can often be related to atmospheric forcing. In the eastern mid‐latitudes, the large annual signal in the atmospheric westerlies correlates with a fivefold increase in drifter speeds from summer to winter. In the tropics, a small but persistent Ekman flow component causes the drifters to move northward from the equatorial regions where the mean geostrophic flow converges toward the equator. In the eastern limb of the gyre, response to the atmospheric forcing of the Pacific high pressure center causes the trajectories to cross isolines of dynamic topography. The drifters provide a unique insight into the spatial and temporal relationship of geostrophic and wind‐driven flow components that influence the near‐surface circulation of the subtropical gyre.
Effects of time‐varying viscosity on oscillatory turbulent channel flow
Authors: Lavelle J. W. , Mofjeld H. O.
Published: February 2008

A semianalytic model of a time‐dependent bottom boundary layer has been constructed in which flow and time‐variable eddy viscosity are interdependent. Evaluated in the case of oscillatory forcing at tidal frequencies, the model shows that neglecting time variations in viscosity results in underestimates of maximum bottom stress and distortion of the flow profile near times of flow reversal. Acceleration and variable viscosity also add terms proportional to z In (z/z0) and z to the conventional steady state In (z/z0) profile near the bottom. Inferences based on the logarithmic profile for measurements made in time‐dependent boundary layers may consequently yield inaccurate estimates of roughness length and friction velocity. Stress is seen to lag flow at points away from the bottom, as has been observed in measurements, though bottom stress always leads flow aloft. Bottom stress is found to depend linearly on the free‐stream velocity in the limit of time‐invariant viscosity. In the limit of strongly time‐varying viscosity, bottom stress is more nearly quadratic. The friction coefficients are reasonably time independent only when the phase lead θ between bottom stress τB and free‐stream velocity U is incorporated into the bottom friction expression. A generalized bottom drag law for oscillatory flow that encompasses all these features takes the form τB = gβ|U(t/T + θ)|β U(t/T + θ), where β has a value between 0 and 1, and θ is typically a few tens of degrees. In the examples evaluated, when β = 0, gβ (conventionally called r) ranges from 2–15×10−2 cm/s, and when β = 1, gβ (conventionally called CD) ranges from 1–5×10−3, the variation in both cases depending on surface Rossby number.
Long and medium‐scale waves in the lower stratosphere from satellite‐derived microwave measurements
Authors: Yu Wen‐bi , Martin Russell L. , Stanford John L.
Published: February 2008

Global grids have been constructed from high‐quality TIROS‐N microwave sounder unit measurements which closely approximate the 30‐ to 150‐mbar geopotential thickness. The grids compare favorably with conventional analyses. Grids for January 1979 are spectrally analyzed by Fourier transform for zonal wave numbers 1–10 over latitudes 80°N to 80°S. Both time mean and transient medium‐scale waves are discussed in some detail. In the time mean, wave 1 dominates all northern latitudes. In equatorial regions, wave 1 also is dominant, but a secondary spectral peak is noted at wave 4. The most remarkable feature seen is a strong medium‐scale structure with eastward movement in southern (summer) mid‐latitudes. Zonal wave numbers 5 and 6 have periods of about 10–15 days and 5 days, respectively. These results provide independent corroboration of such structures recently reported by several investigators. The mechanism by which the dominant medium‐scale waves are maintained is not understood.
Bathymetric influences upon the character of North Pacific Fronts, 1976–1980
Authors: Levine Edward R. , White Warren B.
Published: February 2008

Thermal fronts in the North Pacific from June 1976 to May 1980 have been mapped at the 300‐m level by using temperature data obtained in the region 30°–45°N, 160°E–160W in the TRANSPAC XBT Volunteer Observing Ship Program. The origins of the paths of the major frontal bands in the study region (i.e., the Kuroshio Extension, the Subarctic Fronts, and the Subtropical Front) appear to be related to the principal bathymetric features of the western mid‐latitude North Pacific (i.e., the Shatsky Rise, the Emperor Seamount Chain, and the Hess Rise). In the long‐term mean, the Kuroshio Extension Front at 35°N was observed to have bifurcated at the Shatsky Rise near 160°E into two bands. One band continued northeast along the Shatsky Rise to 42°N to become the North Subarctic Front. The other band continued zonally eastward where it encountered the Emperor Seamounts, near 36°N, 170°E, and trifurcated into bands which tracked through passages between the Seamounts near 37°N, 34°N, and 32°N, respectively. Downstream, the most northern of these three bands became the South Subarctic Front near 39°N, the middle band continued as the Kuroshio Extension Front at 35°N, and the most southern band became the Subtropical Front near 32°N. The middle band tracked north of the Hess Rise, while the most southern band tracked south of the Hess Rise. A near‐meridional frontal band linked the North and South Subarctic fronts in the Emperor Seamount region near 170°E. In the annual mean and individual seasonal mean maps, the essential character of topographic influence of the long‐term mean was observed. However, the individual frontal bands varied seasonally about the long‐term mean by ±2° of latitude. Also, all four major frontal bands were not always observed, and intermittent linkages and additional filaments also occurred.
Satellite observed behavior of the Terra Nova Bay Polynya
Authors: Kurtz Dennis D. , Bromwich David H.
Published: February 2008

Infrared satellite images indicate that a polynya, surrounded by a zone of loose pack ice, persisted in Terra Nova Bay, Antarctica through the winter of 1979; the feature may recur each year. The affected region (polynya and loose pack) occupied roughly 25000 km2 of the western Ross Sea. Throughout the winter the area of open water fluctuated quasi‐periodically with a period of 15–20 days. Average polynya area was 1000 km2; maximum area was approximately 5000 km2. Fluctuations were associated with the magnitude of the zonal geostrophic wind, with a closing polynya being related to strong, persistent easterlies. An open, or opening, polynya was linked with persistent westerly or weak easterly winds and the probable descent of adiabatically warming, drift‐bearing air from the plateau. This air enters Terra Nova Bay through the Reeves Glacier valley, probably as katabatic surface winds. Polynya formation was probably due to the action of these winds on the coastal pack ice, while areal fluctuations reflected the interplay between the katabatic winds and synoptic scale motions advecting ice toward and away from the bay
Analysis of MARSEN X band SAR ocean wave data
Authors: Shuchman R. A. , Rosenthal W. , Lyden J. D. , Lyzenga D. R. , Kasischke E. S. , Gunther H. , Linne H.
Published: February 2008

Analysis of X band SAR imagery collected during the MARSEN experiment indicates that the APD‐10 SAR system imaged both range‐ and azimuth‐traveling gravity waves. However, only the near‐edge portion of the APD‐10 imagery provided reliable spectral wave estimates. Numerous motion artifacts, which manifest themselves as azimuth‐oriented streaks, are visible on the data and are believed to be caused by breaking waves. Because of the large platform velocity, the APD‐10 SAR data are relatively insensitive to wave enhancement adjustments performed during the processing of SAR signal histories. A modulation transfer function to relate SAR‐derived spectra to in situ measurements has been developed. The transfer function is smaller and falls off more rapidly with wave number for azimuth‐traveling waves than for range‐traveling waves. This is a consequence of the smaller inherent modulation for azimuth‐traveling waves and the degraded resolution in the azimuth direction as a result of motion effects and agrees, at least qualitatively, with theoretical predictions
Sea surface temperature patterns and air‐sea fluxes in the German Bight during MARSEN 1979, Phase 1
Authors: Katsaros Kristina B. , Fiúza Armando , Sousa Fátima , Amann Volker
Published: February 2008

An analysis was made of remotely sensed sea surface temperatures (SST) obtained from aircraft and satellites and of data from hydrological surveys conducted in the German Bight during the Marine Remote Sensing Experiment (MARSEN) phase 1, in the North Sea August 15 to September 15, 1979. The signature of a thermal double frontal structure associated with a coastal front resulting from freshwater runoff and extending along the 30‐m bottom contour at the northeastern edge of the submarine glacial valley of the Elbe river was the most prominent feature in the SST field. Air‐sea fluxes of heat and momentum were computed for the same period from field observations by using recently developed parameterization schemes. It was possible to group the SST patterns according to the intensity of the wind stress and of the net heat gain or loss by the sea. It was found that the thermal signal of the front is more evident at the surface when the wind stress is greater than about 0.5 N m−2. In the summer of 1979 these occasions were also associated with weak heating or with a net cooling of the sea. During periods of weaker wind stress and strong solar heating, a shallow thermocline develops which tends to isolate the frontal cold water from the interface and the SST pattern becomes less organized. Frontal eddies related to the baroclinicity and to the current shear at the frontal zone were visible in the surface distributions of density and on the satellite infrared imagery.
Mesoscale features along the first Oyashio Intrusion
Authors: Vastano Andrew C. , Bernstein Robert L.
Published: February 2008

Satellite and hydrographic observations obtained during May 1981 are used to examine the sea surface and subsurface temperature structures within a portion of the Tohoku Area (38°–43°N) extending east of Japan to 149°E longitude. These data delineate the Oyashio Front and the evolution of mesoscale features dominating the surface layer circulation east of northern Honshu and Hokkaido. A perturbation on the first Oyashio Intrusion generated eddies adjacent to the Oyashio Front and contributed to a jetlike feature with associated, paired vortices that intruded into what has been defined as the “perturbed area” (39°–42°N) southeastward from the vicinity of the Tsugara Strait. NOAA6 satellite Advanced Very High Resolution Radiometer infrared images and sea surface temperature distributions identified specific eddies and fronts, that also appeared as banded warm and cold regions within XBT (expendable bathythermograph) sections. The satellite data helped define the lateral extent of the features, while the sections provided estimates of their vertical extent. A new procedure for the determination of satellite sea surface temperatures was used to produce a composite temperature distribution over a portion of the Tohoku Area. The satellite‐derived temperature estimates exhibited a 0.8°C rms scatter about a 0.6°C warm bias relative to the XBT data. This map displays the intense mesoscale sea surface temperature variability in the region along the Oyashio Front and within the subarctic regime.
Thermohaline circulation below the Ross Ice Shelf: A consequence of tidally induced vertical mixing and basal melting
Authors: MacAyeal Douglas Reed
Published: February 2008

The warmest water below parts of the Ross Ice Shelf resides in the lowest portion of the water column because of its high salinity. Vertical mixing caused by tidal stirring can thus induce ablation by lifting the warm but dense water into contact with the ice shelf. A numerical tidal simulation indicates that vertically well‐mixed conditions predominate in the southeastern part of the sub‐ice‐shelf cavity where the water column thickness is small. Basal melting in this region is expected to be between 0.05 and 0.5 m/yr and will drive a thermohaline circulation having the following characteristics: high salinity shelf water (at −1.8°C), formed by winter sea‐ice production in the open Ross Sea, flows along the seabed toward the tidal mixing fronts below the ice shelf; and meltwater (at −2.2°C), produced in the well‐mixed region, flows out of the sub‐ice‐shelf cavity along the ice shelf bottom. Sensitivity of this ablation process to climatic change is expected to be small because high salinity shelf water is constrained to have the sea‐surface freezing temperature.
Pycnocline development and its consequences in the Middle Atlantic Bight
Authors: Aikman Frank
Published: February 2008

Sciences Seasonal pycnocline development in the shelf and slope waters of the Middle Atlantic Bight is investigated numerically using a one‐dimensional, two‐layer, bulk‐mixing model. The model considers the buoyancy budget of the system and includes both turbulent diffusion and entrainment across the pycnocline that separates the layers as well as a parameterization for mixed‐layer shallowing. Climatic estimates of the surface buoyancy and energy inputs drive the model. The shelf and slope water regimes, however, experience different inputs: freshening, due to river runoff, and a larger net heat gain, due to a more positive air‐sea temperature difference, both contribute to a larger buoyancy input to the shelf water regime; and the wind stress is larger over the slope. Numerical computation of vernal pycnocline development results in the formation of a shelf water pycnocline that is both shallower and more intense than that over the slope. A consequence of this mismatch is a reversal of the offshore density gradient at intermediate depths and an intrusion of slope water into the shelf water pycnocline, called the pycnocline salinity maximum. It is possible that interannual variations in the timing and magnitude of the heating and freshwater input from rivers can cause concomitant variations in salt input via the pycnocline salinity maximum.
Wave setup and wave‐induced currents in coastal zones
Authors: Dolata L. F. , Rosenthal W.
Published: February 2008

The influence of a decaying surface wave field on currents and water level variations is derived in three dimensions. The purpose is to show that surface waves have an influence on current generation outside, as well as inside, the surf zone. Therefore, the wave‐induced source terms for current generation are implemented into a depth‐integrated current model. The resulting currents and water level changes of the numerical simulation of a hypothetic wind and wave field over a gently sloping bottom show that wave‐induced source terms should be included in current and water level models. This inclusion must lead to a revision of model parameters in the wind and bottom stress, which are used to tune the numerical models to meet the observations. Since the observations already include wave setup effects, these have been partly included in the model constants. A comparison between observations and a numerical model with wave‐induced sources will lead to a readjustment of wind‐ and bottom‐induced sources. This task is left for future work.
Radium and barium in the Amazon River system
Authors: Moore Willard S. , Edmond John M.
Published: February 2008

Data for 226Ra and 228Ra in the Amazon River system show that the activity of each radium isotope is strongly correlated with barium concentrations. Two trends are apparent, one for rivers which drain shield areas and another for all other rivers. These data suggest that there has not been extensive fractionation of U, Th, and Ba during weathering in the Amazon basin. The 226Ra data fit a flux model for the major ions indicating that 226Ra behaves conservatively along the main channel of the Amazon River.
Spring breakup and flushing of an Arctic lagoon estuary
Authors: Matthews J. B. , Stringer W. J.
Published: February 2008

Simpson Lagoon is a shallow body of water separated from the Beaufort Sea by a chain of low‐lying barrier islands. Narrow channels are found between the barrier islands, one of which, the Egg Island Channel, is a major connection between the lagoon and the Beaufort Sea. The Kuparuk River produces great quantities of springtime floodwaters which overflow the still‐frozen lagoon. This paper examines the relationships between these floodwaters and the character of the water within the lagoon. Measurements of temperature, salinity, sea level, and currents have been made in Egg Island Channel during 1978 and 1979. Meltwater from the Kuparuk River was observed on satellite images to overflow the 2‐m‐thick bottomfast ice of the lagoon in late May and early June. These floodwaters flush saline (>40‰) water out the 5‐m deep channel and replace it with freshwater at 0°C. Analysis of satellite images for several years shows that overflow occurs on May 31 with a standard deviation of 8 days. Sea level rose 64 cm above mean at peak flood in 1978. Subsequently, channel waters warmed to 8°C in late June and were flushed by cold (∼0°C, saline (∼24‰) water from the Beaufort Sea in mid‐July. Flooding in 1979 was anomalously early, providing additional insight into the flushing process. The return of seawater to the channel is due to wind‐driven currents following the clearing of bottomfast ice in the lagoon. Satellite image analysis shows that ice‐free conditions occur by July 10 with a standard deviation of 8 days.
Convective transport of brine and thaw of subsea permafrost: Results of numerical simulations
Authors: Swift Daniel W. , Harrison William D.
Published: February 2008

A two‐dimensional numerical simulation is used to investigate the circulation of brine in the thawed porous bottom sediments which overlie ice‐bearing permafrost on the continental shelf of the Arctic Ocean. The brine motion is assumed to be governed by Darcy's Law and is effective in transporting salt to the ice‐bearing sediments and therefore effective in determining their thaw rate. The simulations are initiated by assuming that the initial brine concentration in the thawed sediments matches the average annual salinity of the overlying sea water. A diffusive layer along the phase boundary develops at the base of the thawed sediments and thickens to the point where it becomes convectively unstable. The system is followed in time to observe the development of a stable convective flow pattern. Simulations were run at Rayleigh numbers of 1750 and 17,500. In the 1750 Rayleigh number run the boundary layer and convective plumes had characteristic thicknesses of about 2 meters in a 20‐m thick thaw layer. The high Rayleigh number run had thicknesses of only a few tenths of a meter. The high Rayleigh number run is more consistent with the observations, but the results are at sufficient variance with the observations to suggest there is some not yet identified process affecting the transport of brine to the phase boundary.
Acoustic measurements of wind speed and precipitation over a continental shelf
Authors: Lemon David D. , Farmer David M. , Watts D. Randolph
Published: February 2008

During the summer of 1982 at sites on the continental shelf of British Columbia, ambient noise measurements were made in three frequency bands centred at 4.3, 8.0, and 14.5 KHz. The experiment wasdesigned to compare the relationship between ambient noise and Wind speed over a continental shelf with similar previous measurements made in the deep ocean. Ambient noise and simultaneous surface wind speed observations at two locations were consistent with the previously determined relationship 20 log V = a(NSL) ‐ b where V is the surface wind speed at 3 m in meters per seconds, NSL is the observed noise spectrum level in dB re 1μPa2 Hz−1, and a and b are frequency‐dependent constants. The resulting coefficients are similar to those found previously and allow a fit between ambient noise and wind speed to within ±1.5 ms−1 over the observed range of 0–12 ms−1. Although the data are certainly sparse, a clear acoustic signal associated with precipitation was observed and compared with rainfall measurements made at nearby coastal light stations. When Franz's (1959) theoretically determined calibration is used the results show good agreement with the presence or absence of rain and agreement to within a factor of 2 in the measured quantity. The results provide encouraging evidence for the potential use of ambient noise measurements in estimating both wind speed and precipitation.
Katabatic wind forcing of the Terra Nova Bay polynya
Authors: Bromwich David H. , Kurtz Dennis D.
Published: February 2008

The Terra Nova Bay polynya is a perennial winter feature in the western Ross Sea, Antarctica, which occupies roughly 1000 km2, it is formed and maintained by the combined influence of persistent katabatic winds, which advect newly formed bay ice eastward, and the Drygalski Ice Tongue, which prevents northward drifting pack ice from entering Terra Nova Bay. Existence of anomalously strong katabatic drainage along this coast is predicted by Parish's (1982) simulation of wintertime airflow which reveals a pronounced confluence of surface winds upslope from the Reeves Glacier where the winds are further focused by local topography. The simulation is strongly supported by regional sastrugi orientations. Average wintertime atmospheric conditions and ice sheet topography which control surface air drainage are stable on a climatic time scale; therefore, persistent wintertime katabatic winds should be an annual phenomenon. Further evidence comes from multi‐year Landsat images which consistently show windswept, snowfree areas on the Reeves Glacier. In marked contrast to typical Antarctic katabatic winds, strong persistent winter winds are observed at sea level ∼25 km beyond the coastal slope break. Air probably descends as bora‐type winds and is likely to be significantly denser than the air at sea level; conditions are not favorable for hydraulic jumps apparently typical of other katabatic regimes. The horizontal density difference is maintained during airflow across the Nansen Ice Sheet because relatively little air mass modification occurs there in contrast to situations where air moves over an ice‐laden ocean. Observations thus suggest that katabatic winds maintain their identity for some distance seaward of the coast; qualitative trajectory calculations indicate that for representative geostrophic conditions this distance is on the order of the observed polynya width. Estimated ice freezing rates are ∼20 cm day−1, but wind‐generated waves and currents prevent ice from consolidating. The blocking effect of the Drygalski Ice Tongue is a consequence of its orientation with regard to western Ross Sea ice drift patterns; ice tongue length controls polynya width. Absence of such blocking along other coasts experiencing strong katabatic outflow partly explains why similar polynyas do not form there.
Gas exchange rates across the sediment‐water and air‐water interfaces in south San Francisco Bay
Authors: Hartman Blayne , Hammond Douglas E.
Published: February 2008

Radon 222 concentrations in the water and sedimentary columns and radon exchange rates across the sediment‐water and air‐water interfaces have been measured in a section of south San Francisco Bay. Two independent methods have been used to determine sediment‐water exchange rates, and the annual averages of these methods agree within the uncertainty of the determinations, about 20%. The annual average of benthic fluxes from shoal areas is nearly a factor of 2 greater than fluxes from the channel areas. Fluxes from the shoal and channel areas exceed those expected from simple molecular diffusion by factors of 4 and 2, respectively, apparently due to macrofaunal irrigation. Values of the gas transfer coefficient for radon exchange across the air‐water interface were determined by constructing a radon mass balance for the water column and by direct measurement using floating chambers. The chamber method appears to yield results which are too high. Transfer coefficients computed using the mass balance method range from 0.4 m/day to 1.8 m/day, with a 6‐year average of 1.0 m/day. Gas exchange is linearly dependent upon wind speed over a wind speed range of 3.2–6.4 m/s, but shows no dependence upon current velocity. Gas transfer coefficients predicted from an empirical relationship between gas exchange rates and wind speed observed in lakes and the oceans are within 30% of the coefficients determined from the radon mass balance and are considerably more accurate than coefficients predicted from theoretical gas exchange models.
Mass transfer between Gulf Stream rings
Authors: Mied Richard P. , Lindemann Gloria J.
Published: February 2008

Experiments are performed to examine the close interaction of two anticyclonic Gulf Stream rings. A tracer is put in one ring initially, is advected, and diffuses into the other as the pair evolve in time. The appearance of the tracer streak lines is examined in the light of conservation of potential vorticity. Kinematic viscosity and tracer diffusivity are each varied over two orders of magnitude, and tracer behavior changes greatly. This work is analogized to the interaction of a warm‐core ring with the Gulf Stream, with the streamers observed in this work corresponding to those observed in ring/stream interactions.
The generation and propagation of internal gravity waves in a rotating fluid
Authors: Maxworthy T. , D'Hieres G. Chabert , Didelle H.
Published: February 2008

On the basis of a series of experiments in a 2×5 m tank containing a two‐layer salt‐stratified fluid mounted on the large rotating table at the University of Grenoble, we observe and attempt to explain the internal wave motions created by a moving bottom topography, which is oscillated to simulate barotropic tidal flow. We have found that when the flow over the obstacle is very supercritical, the initial wave field is quite asymmetric in plan form but evolves toward a more symmetric shape as time progresses. Large velocities are created along the crests of the waves, and these appear to scale with 2ΩAλ, where Ω is the rotation rate, A the nondimensional wave amplitude, and λ the wave width. When the flow is only slightly supercritical, the transverse velocities are correspondingly smaller, and the wave field approaches the symmetric plan form found by Maxworthy (1979) for the nonrotating case. For our particular combination of stratification and obstacle shape, two major wave systems evolve from two initial pulses created by the obstacle motion. There are of solitary wave type and during the course of the experiments are seen to evolve, combine, and form a series of finite amplitute waves ordered by amplitude. Rotation appears to have little effect on this evolutionary process but does initially affect the wave plan form and amplitude distributions.
The Lake Erie response to the January 26, 1978, cyclone
Authors: Dingman J. Steven , Bedford Keith W.
Published: February 2008

A descriptive analysis of the reponse of Lake Erie to the passage of the blizzard cyclone of January 26, 1978, is presented. This intense extratropical cyclone, the worst ever to cross the Ohio Valley and Great Lakes region of the United States, set numerous record low sea level pressure readings at nearly every recording station surrounding Lake Erie and subjected the lake region to sharp temperature drops and high winds. The lake surface was significantly ice covered during the storm event; it remained virtually intact on the entire Western Basin, and partial ice cover breakup occurred over the Central Basin. The investigation of the water level fluctuations induced by the cyclone are based on data acquired from normal meteorological and water level monitoring stations surrounding the lake. The most unusual aspects of the water surface fluctuations include the observance of a pressure suction induced rise in water level in the Western Basin before the storm passed north of the lake; a maximum storm surge setup occurring between Marblehead, Ohio, and Port Colborne, Canada, and not between the ends of the lake; and a separate oscillatory surge occurring at Port Stanley, Canada. The probable causes and reasons for these fluctuations are thoroughly analyzed in the context of existing theories that deal with how a lake surface responds to external atmospheric forcing functions such as wind stress, sea level pressure changes, and resonance. The effect of the ice cover on the water level fluctuations is also presented.
Measuring the sea ice floe size distribution
Authors: Rothrock D. A. , Thorndike A. S.
Published: February 2008

Sea ice is broken into floes whose diameters range from meters to a hundred kilometers. This fragmentation affects the resistance of the ice cover to deformation and the melting at floe sidewalls in summer. Floes are broken by waves and swell near the ice edge and, throughout the pack, by isostatic imbalances, thermal cracking, winds, and currents. In winter, they are welded together by freezing. Floe size can be measured by several properties p, for instance, area or mean caliper diameter. Two definitions of floe size distribution seem useful: F(p), the fraction of area covered by floes no smaller than p; and N(p), the number of floes per unit area no smaller than p. F(p) can be measured by sets other than areas, such as the fraction of a line or of a point set covered by floes no smaller than p. If N behaves like ρα for small ρ, where ρ is mean caliper diameter, α must be greater than −2 so that the small floes occupy finite area. If −2<α<−1, the perimeter of small floes is infinite. Several summertime distributions have been measured. On a log‐log graph their slopes (local values of α) range from −1.7 to −2.5. One distribution follows a power law; the others have steeper slopes for larger floes and more gradual slopes for smaller floes. Another sampling strategy is to measure the lengths of line segments on floes. The distribution of these chord lengths is equivalent to the distribution of floe diameters. The variance of an estimate of the fraction g of area covered by floes in any size range is g(1 ‐ g)K−1, where K is the equivalent number of independent samples. K can be found from the autocovariance of the indicator function for the chosen size range. For line sampling of a narrow range of floe diameters, K is the ratio of the sample length to the floe diameter.
A note on “Physical oceanography of the Gulf of Maine” by Henry B. Bigelow (1927)
Authors: Mountain David G.
Published: February 2008

The circulation pattern proposed by Bigelow (1927) included a major current of water flowing south‐ward off the southern side of Georges Bank. This pattern is not consistent with recent long‐term current measurements that show that the water there moves westward along the bank isobaths. The measurements made by Bigelow are reviewed to show that a Gulf Stream ring was located south of the bank during his observations and that the ring was likely entraining water off the Georges Bank, consistent with Bigelow's observations.
A theory of the imaging mechanism of underwater bottom topography by real and synthetic aperture radar
Authors: Alpers Werner , Hennings Ingo
Published: February 2008

A simple theoretical model of the imaging mechanism of underwater bottom topography in tidal channels by real and by synthetic aperture radar (SAR) is presented. The imaging is attributed to surface effects induced by current variations over bottom topography. The current modulates the short‐scale surface roughness, which in turn gives rise to changes in radar reflectivity. The bottom topography‐current interaction is described by the continuity equation, and the current‐short surface wave interaction is described by weak hydrodynamic interaction theory in the relaxation time approximation. This theory contains only one free parameter, which is the relaxation time. It is shown that in the case of tidal flow over large‐scale bottom topographic features, e.g., over sandbanks, the radar cross‐section modulation is proportional to the product of the relaxation time and the gradient of the surface current velocity, which is proportional to the slope of the water depth divided by the square of the depth. To first order, this modulation is independent of wind direction. In the case of SAR imaging, in addition to the above mentioned hydrodynamic modulation, phase modulation or velocity bunching also contributes to the imaging. However, in general, the phase modulation is small in comparison to the hydrodynamic modulation. The theory is confronted with experimental data which show that to first order our theory is capable of explaining basic features of the radar imaging mechanism of underwater bottom topography in tidal channels. In order to explain the large observed modulation of radar reflectivity we are compelled to assume a large relaxation time, which for Seasat SAR Bragg waves (wavelength 34 cm) is of the order of 30–40 s, corresponding to 60–80 wave periods.