bluuebunny/crossref_metadata_2025 huggingface dataset:
An analysis of SEASAT altimeter measurements over a coastal area: The English Channel
Authors: Le Provost C.
Published: February 2008

To assess the extent to which it is possible to use satellite altimetric measurements over coastal areas, the SEASAT observations made over the English Channel were intensively analyzed. Over this shallow water area, tides are very important (of the order of several meters), which introduces a large space and time variability of the sea surface elevations. A model of tidal prediction for the area studied was used to eliminate this variability. As meteorological effects can also introduce significant sea surface variations, a numerical storm surge model was also used. Thus it was possible to remove the main part of the sea surface time variations from the altimetric measurements. The analysis of six successive flights over the same ground track, during the Bermuda orbit, shows that the tidal and meteorological predictions are accurate and that the main deviations remaining in the altimetric signal result from large imprecision in the satellite ephemeris, of the order of several meters. From a detailed study of six other flights over the Channel, including a matching of the satellite tracking at the different crossing points, an altimetric geoid was established: as a first approximation it is in good agreement with the more recent geoids produced over this area; however, some significant differences can be seen which are of interest to geodesists.
Interpretation of synthetic aperture radar measurements of ocean currents
Authors: Rufenach Clifford L. , Shuchman Robert A. , Lyzenga David R.
Published: February 2008

Synthetic Aperture Radar (SAR) experiments have been performed over the last few years to measure ocean currents inferred from shifts in the Doppler spectral peak. Interpretations of aircraft SAR measurements, when compared with limited surface values, tend to underestimate the currents by about 25%. A theory is developed that modifies the classical Doppler expression showing that the radar measurements are dependent on the radar processor (system) bandwidth and the received signal bandwidth. Measured bandwidths give a correction that increases the inferred current values by about 25%, bringing the measurements into good agreement. This new correction lends credence to the theory and increases the potential for application of SAR systems to future ocean current measurements. SAR measurements should include the determination of processor and signal bandwidths such that this correction can be applied.
Mean heat and momentum budgets during upwelling for the coastal waters off northwest Africa
Authors: Richman James , Badan‐Dangon Antoine
Published: February 2008

Mean heat and momentum budgets for the upwelling region off northwest Africa during March and April 1974 are estimated at midshelf, 32 km from the coast, using current and temperature measurements at six depths in 73 m of water. In the heat budget, the mean cross‐shelf circulation transports 1.14×107 W m−1 offshore, while fluctuations in the cross‐shelf circulation transport an additional 1.9×106 W m−1 offshore. This offshore heat flux is compensated by the net radiative heat gain in the region of 4.8×106 W m−1 and an alongshore heat flux due to the mean circulation of 5.1×106 W m−1 as indicated by southward cooling of the surface mixed layer of 0.5°C per 100 km. In the cross‐shelf momentum budget, the alongshore flow is nearly geostrophic with the Coriolis force being approximately balanced by the steric sea level slope. For the alongshore momentum budget, the surface wind stress is balanced by the bottom stress, alongshore pressure gradient, and Coriolis force associated with the net onshore mass transport. A three‐dimensional momentum balance with significant alongshore pressure gradients results even if the coordinate system is rotated 6° counterclockwise so that no net cross‐shelf mass transport occurs.
Mesoscale oceanographic features associated with the central Bering Sea ice edge: February–March 1981
Authors: Muench Robin D.
Published: February 2008

Midwinter 1981 observations from the central Bering Sea shelf showed a hydrographic structure which was two layered in temperature, salinity, and density. This structure was confined to a 100‐km‐wide band which coincided approximately with the ice edge. The colder, lower‐salinity upper layer was continuous in its T‐S properties with homogeneous water to the north beneath the ice. The warmer, more saline lower layer was similarly continuous with water to the south near the shelf break. A northwestward baroclinic flow of the surface relative to 75 dbar was associated with the layered structure. The layered structure and associated flow appear to be regular winter features associated with the ice edge in this region. Input of low‐salinity water from melting of ice along the edge is adequate to maintain the layered structure, and its associated baroclinic circulation, against the effects of tidal and wind mixing. The resulting observed oceanographic features were similar to those which have been found in association with midshelf and shelf break fronts in other regions and appear to define a dynamically controlled boundary between the cold, low‐salinity water on the northern shelf and the warmer, more saline water near the shelf break.
An objective procedure for detecting and correcting errors in geophysical data: 2. Multidimensional applications
Authors: Fleming Henry E. , Hill Michael L.
Published: February 2008

The one‐dimensional objective procedure for detecting and then correcting errors arising in geophysical data, developed in the previous paper of this series, is extended to higher dimensions. The data again must be sampled at equal increments of time or distance, but the spacings can be different in each dimension. Of interest are only those errors larger in magnitude than the background noise level. Errors occurring in isolation, clusters, and corners are treated as in the first paper; however, the appropriate generalizations to higher dimensions are developed in detail. Underlying the success of the error detection and correction procedure is the alternating subset method, which is extended to higher dimensions. Complete step‐by‐step instructions are given for the two‐dimensional procedure. Finally, a two‐dimensional example is presented to demonstrate the kinds of improvements afforded by the procedure.
Polarized microwave radiation transfer in precipitating cloudy atmospheres: Applications to window frequencies
Authors: Huang Runheng , Liou Kuo‐Nan
Published: February 2008

A microwave radiation transfer model taking into account Mie scattering polarization effects is developed for a plane‐parallel precipitating cloudy atmosphere. In the model the azimuthally averaged Mie scattering phase matrix elements are expressed in terms of double Legendre polynomial expansion and the cloud temperature is approximated by a linear function of the optical depth. The complete solution of the fundamental transfer equation is derived utilizing the discrete‐ordinates method for horizontal and vertical polarization components. Using this model, the brightness temperature and degree of polarization for three microwave window frequencies of 19.35, 37.0, and 85.5 GHz are calculated for a number of rainfall rates over both land and ocean surfaces. We show that the brightness temperature computed for 85.5 GHz using a simple Rayleigh scattering approximation is underestimated by about 7°K for a layer thickness of 4.7 km and a rainfall rate of 5 mm/hr. Effects of the Mie scattering function and nonisothermal cloud structure must both be included for brightness temperature calculations of 37 and 85.5 GHz when thick precipitating clouds are involved. Moreover, we also find that there is a significant degree of polarization for emergent radiation of 19.35 GHz at a zenith angle of 50° under a light rainfall condition over ocean surfaces. Over land surfaces, polarization produced by precipitating clouds is rather small for the three window frequencies. Finally, we show that the existence of ice particles in the upper part of a precipitating cloud largely reduces the upward radiances of the 85.5 GHz frequency.
Observations of unusual structures of high‐latitude stratospheric electric fields
Authors: Madsen M. M. , D'angelo N. , Iversen I. B.
Published: February 2008

We report the observation, by means of balloon‐borne sensors, of three cases of unusual stratospheric electric field structures at high latitudes. In all three cases a region of downward directed electric field is flanked by regions with upward field. In two out of the three cases, the central downward field is much stronger than the average fair weather field. The vertical current densities involved are <5×10−11 A/m2. These field structures are observed only about 0.5% of the time.
Thermodynamic properties in chemical reaction processes of seawater
Authors: Endo Harumi , Shigehara Koji
Published: February 2008

Theoretical expressions for thermodynamic parameters of the chemical reaction processes of ionic hydration in seawater are obtained by using the kinetic model of hydrated water molecules around ions in liquid water. Assuming the additivity law between the instantaneous (∞) thermodynamic quantities of electrolytes in seawater and that of the remaining nonhydrated water (i.e., free water), we split the relaxational (r) quantity of seawater from the equilibrium one (0) by subtracting the ∞ value. The quantity (∂T/∂P)S,0, which may be related to potential temperature, can be divided into instantaneous and relaxation, respectively. The relaxational quantity (∂T/∂P)S,ralways becomes negative, while the instantaneous one (∂T/∂P)S,∞is always positive. Both absolute values of (∂T/∂P)Sforrand ∞ decrease with increasing salinity and temperature, respectively. This fact is illustrated in terms of the ionic hydration.
Parameterization of carbon dioxide 15 μm band absorption and emission
Authors: Ou Szu‐Cheng S. , Liou Kuo‐Nan
Published: February 2008

A parameterization scheme for carbon dioxide 15 μm band absorption and emission is developed based on the line‐by‐line transmittance data presented by Fels and Schwarzkopf (1981). We derive two polynomial equations to represent the broadband emissivity as functions of the temperature and pressure corrected path length. A detailed error analysis has been performed, and the root mean square errors are shown to be on the order of 5 and 7.5% for the lower and upper atmosphere cases, respectively. Cooling rates calculated from the emissivity parameterization approach show errors within about 5% when they are compared with those computed from exact line‐by‐line integrations.
Balloon borne LIDAR measurements of stratospheric hydroxyl radical
Authors: Heaps William S. , Mcgee Thomas J.
Published: February 2008

A balloon‐borne laser radar (LIDAR) system for the determination of stratospheric hydroxyl radical concentration has been constructed and flown by Goddard Space Flight Center. The system measured hydroxyl in the 34–37 km altitude range throughout an afternoon and early evening yielding the first post‐sunset hydroxyl determinations ever obtained. Daytime values (∼5×106 cm−3) were somewhat lower than previous measurements using in situ resonance fluorescence. Nighttime values (∼7×105 cm−3@2100 CDT) were higher than predicted by current one‐dimensional (1‐D) models. Possible sources of these discrepancies along with improvements possible in future systems are outlined.
Infrared absorption spectroscopy applied to stratospheric profiles of minor constituents
Authors: Louisnard N. , Fergant G. , Girard A. , Gramont L. , Lado‐Bordowsky O. , Laurent J. , Le Boiteux S. , Lemaitre M. P.
Published: February 2008

Infrared absorption by O3, NO, NO2, N2O, HNO3, CO, COS, CH4 and H2O have been observed from a balloon platform at 40 km of altitude and 44°N latitude with a grille spectrometer. The resolution is, for the most part, better than 0.1 cm−1. An analysis is made of the causes of uncertainties. Height profiles are deduced for these species down to 20 km. The mixing ratios near 40 km are 8.5±1.5 ppm for ozone, 8. ±1 ppm for water vapor, and 19±5 ppb for carbon monoxide. Nitric acid and carbonyl sulfide exhibit a decreasing profile with altitude. Mixing ratios near 30 km are <10–10 for COS and 8±1 ppb for HNO3. Some common observations are made, related to the particular temperature profile, which emphasize the importance of simultaneous measurements of stratospheric species and meteorological parameters.
Simulation of NOx partitioning along isobaric parcel trajectories
Authors: Solomon Susan , Garcia Rolando R.
Published: February 2008

A numerical study is presented of the chemistry of NOx (NO + NO2 + NO3 + 2 × N2O5) in air parcels assumed to travel on constant pressure surfaces for a period in early February 1977. Airflow was observed to be stable and largely barotropic during this period. Strong coupling between photochemical and dynamical effects is found to play an important role in determining the distributions of these species. Comparison of model results to observations of the total column abundance of NO2 (Noxon, 1979) yields good agreement and implies that attention should be given to dynamical conditions when comparing model calculations and observations of odd nitrogen species in the stratosphere.
Atmospheric CO2 content in the last 120,000 years: The Phosphate‐Extraction Model
Authors: Keir R. S. , Berger W. H.
Published: February 2008

Broecker [1982] has proposed that during the retreat of the Wisconsin ice sheets, atmospheric CO2 increased because of the extraction of phosphorus from the ocean as sea level rose. Using a time‐dependent box‐model, we examine the consequences of the phosphate extraction hypothesis over the last 120,000 years, assuming that δ18O change in core V28‐238 is analogous to sea level variation. The model takes into account the total CO2 and alkalinity balance in the deep sea and in an ‘upper’ reservoir consisting of the surface ocean and atmosphere, which are assumed to be in equilibrium. Dissolution of deep‐sea calcium carbonate sediment is assumed to respond to the supply of particulate carbonate from the ‘upper’ box and to the dissolved carbonate‐ion concentration of the deep sea. Assuming 1015 mole of phosphorus and 1017 mole of carbon were extracted during deglaciation, the predicted increase in pCO2 is 54 ppm. Variation of pCO2 follows the ice‐volume forcing function with a 1000 yr lag, which is the input residence time of water in the deep sea. The accumulation (supply minus dissolution) of CaCO3 and the percent preservation (accumulation over supply) follow the derivative of the ice‐volume function. Both are similar to the solution index and percent fragments of core V28‐238. In addition, unusually good preservation is predicted during deglaciation due to carbon extraction. If phosphorus but not carbon is assumed to be extracted, the accumulation of CaCO3 varies little, remaining near a value equivalent to the river input.
Cumulus cloud transport of transient tracers
Authors: Gidel Louis T.
Published: February 2008

A theoretical framework is developed for including cumulus cloud transport, rainout of water soluble gases, and aqueous phase chemistry into gas phase photochemical models. Cloud populations are represented as ensemble distributions of individual clouds of various heights. An individual cloud is represented as a one‐dimensional, steady state plume with height independent radius entraining air from the boundary of the cloud. The model is applied to several hypothetical atmospheric tracers to show how clouds may affect the tropospheric distributions of ozone, NOy, SO2, PAN, hydrocarbons, and other gases. Although the numerical experiments were based on cloud mass fluxes from diagnostic studies in the tropics and thus are not representative of the entire globe, it was found that an increasing mixing ratio with height in the free troposphere can be produced for some gases with only a surface source when clouds are present. This suggests that some reactive tropospheric species with primarily surface sources may play a somewhat more important role in tropospheric chemistry than is presently believed depending on the global distribution of cloud mass fluxes. Deficiencies in existing photochemical models due to the way clouds are typically treated are discussed.
The Atmospheric Lifetime Experiment: 1. Introduction, instrumentation, and overview
Authors: Prinn R. G. , Simmonds P. G. , Rasmussen R. A. , Rosen R. D. , Alyea F. N. , Cardelino C. A. , Crawford A. J. , Cunnold D. M. , Fraser P. J. , Lovelock J. E.
Published: February 2008

The Atmospheric Lifetime Experiment is designed to determine accurately the atmospheric concentrations of the four halocarbons CFCl3, CF2Cl2, CCl4, and CH3CCl3, and also of N2O with emphasis on measurement of their long‐term trends in the atmosphere. Comparison of these concentrations and trends for the four halocarbons with estimates of their industrial emission rates then enables calculations of their global circulation rates and globally averaged atmospheric lifetimes. The experiment utilizes automated dual‐column electron‐capture gas chromatographs which sample the background air about 4 times daily at the following globally distributed sites: Adrigole, Ireland (52°N, 10°W); Cape Meares, Oregon (45°N, 124°W); Ragged Point, Barbados (13°N, 59°W); Point Matatula, American Samoa (14°S, 171°W); and Cape Grim, Tasmania (41°S, 145°E). We review the climatology of these “clean air” sites and their ability to describe the global air mass. The instrumentation and methods for data acquisition and processing are then described. An overview of the data obtained and the trends derived during the 3‐year period from July 1978 through June 1981 for each of the five species being measured is presented. The comparative behavior of the species with latitude and time is emphasized. The global average surface concentrations of CFCl3, CF2Cl2, CH3CCl3, CCl4, and N2O are increasing at annually averaged rates of 5.7, 6.0, 8.7, 1.8, and 0.2% per year, respectively, at the midpoint of the 3‐year period of the measurements.
Wetfall chemistry studies around a large coal‐fired power plant in the southeastern United States
Authors: Patrinos A. A. N. , Dana M. Terry , Saylor R. E.
Published: February 2008

A wetfall chemistry study was conducted within a 15‐km radius of a large coal‐fired power plant in the southeastern United States. The study was conducted during the winter of 1981 and included event precipitation sampling on a dense network of 31 stations, selected air chemistry monitoring at two sites, and extensive meteorological measurements. The precipitation samples were analyzed for all major inorganic ionic species, including dissolved sulfur dioxide. The meteorological network included a preexisting network of 49 recording rain gages and four surface windsets, the power plant's fully equipped meteorological station, and a bistatic acoustic sounder. This paper presents the results from five of the sampled storms. Plume washout is evident in most target area samples, and sulfur, hydrogen ion, and chloride ion were found to be the predominant plume‐related species. Concentrations in the affected regions exceeded the background levels by up to 100% in the case of sulfur and of hydrogen ion, and by up to 145% in the case of chloride ion. Two of the storms were characterized by excess dissolved SO2 amounts in the target samples; for these storms, scavenging model simulations of dissolved SO2 concentrations indicated that deposition of sulfur by SO2 scavenging within 12 km was probably less than 2% of the total emitted. Based on the measured Cl− in rainwater, an estimate of the source strength (coal Cl content) using conventional gas scavenging theory appears reasonable.
Radon 222 from the ocean surface
Authors: Dueñas C. , Fernandez M. C. , Martinez M. Perez
Published: February 2008

The flux of 222Rn from shallow water off the bay of Málaga has been measured by the accumulation method. The mean value of 67 atoms m−2 s−1 was obtained, compared with a range of values from 11 to 116 atoms m−2 s−1 calculated from near‐surface 222Rn profiles in seawater obtained by other investigators. Quantitative relations between the flux of 222Rn and 222Rn concentrations in surface water and the temperature of seawater were found. A correlation was also found between the flux of 222Rn and the wind speed at the moment of taking the sample.
Measurement and modeling of the concentrations of terpenes in coniferous forest air
Authors: Hov Øystein , Schjoldager Jørgen , Wathne Bente M.
Published: February 2008

In a coniferous forest area northeast of Oslo, Norway, air samples were collected by adsorption on activated carbon and analyzed by gas chromatography with a high resolution glass capillary column and flame ionization detection. During June and August 1980, seven terpenes were identified with a total concentration range of 8.8–70.7 ppbC (parts per billion, as carbon). α‐Pinene, terpinene, and p‐cymene occurred in the highest concentrations. A one‐dimensional vertical grid model of the atmospheric boundary layer with a detailed mechanism for inorganic and organic gas phase chemical turnover was applied to assess the vertical variability of the terpene concentrations as a function of the ozone concentration, the source strength of the terpenes, the time of the day, the upwind air composition, etc. The calculations showed that very little of the terpene emissions remained airborne after 4–8 hours, in contrast to the anthropogenic hydrocarbons. It was found that the anthropogenic fraction of the hydrocarbons may dominate in concentration, even though the natural part of the source is the larger one. Emission of 2000 μg(m2 h)−1 of terpenes was calculated to give ground level concentrations of total terpenes of up to about 25 ppbC, comparable to or less than the measured concentrations. Terpene emission at this rate was shown to suppress the hydroxyl concentration compared to a model case with zero terpene emissions, while the impact on ozone during daytime was negligible.
Rural measurements of the chemical composition of airborne particles in the eastern United States
Authors: Wolff George T. , Kelly Nelson A. , Ferman Martin A. , Morrissey Mark L.
Published: February 2008

Quantitative measurements of particulate composition were made at three rural sites: in central South Dakota, on the Louisiana Gulf Coast, and in the Blue Ridge Mountains of Virginia. The first two sites were selected to determine background concentrations in continental polar and maritime tropical air masses, respectively, which affect the eastern United States during the summer. The Virginia site was selected as a receptor site, downwind of the midwestern source areas. The South Dakota data established the background concentrations. These concentrations were similar to the levels in Louisiana when air parcels arrived from the Gulf of Mexico, without recently passing over the United States. Levels of fine particles (diameters less than 2.5 μm) were highest in Virginia and were due chiefly to sulfate. Using trajectory and statistical analyses, it is shown that the residence time of an air parcel over the midwestern source area was the most important variable in determining the sulfate levels in the Blue Ridge Mountains.
Effects of heterogeneous processes on NO3, HONO, and HNO3 chemistry in the troposphere
Authors: Heikes Brian G. , Thompson Anne M.
Published: February 2008

Atmospheric measurements of trace oxides of nitrogen, i.e., NO3, HONO, and HNO3, are at variance with accepted photochemical theory. In particular, measured NO3 levels at night are lower than expected from photochemical equilibrium, observed HONO concentrations increase throughout the night, and HNO3 or NO3− is produced rapidly in cloud and plume. We investigate theoretically the potential role of wet particles in the chemistry of NO3, HONO, and HNO3 through a model that incorporates H‐N‐O photochemistry and a heterogeneous scavenging parameterization. The model includes effects due to temperature, pressure, photostationary state number, photolysis rate, diffusion rate, and sticking coefficient. Application of the model to suitable NO3 case studies reveals that low NO3 concentrations could result from the reaction of NO with NO3 provided NO is present at night. However, in the absence of NO, low NO3 can result from heterogeneous loss of NO3 and N2O5 provided their sticking coefficients are greater than 10−3. In the study of HONO we find that a nocturnal production by heterogeneous H2O reactions is insufficient to account for observed levels of HONO. Model sensitivity calculations demonstrate that the formation of HNO3 or NO3− in cloud can occur through two distinct and complementary mechanisms. The route, OH + NO2→ HNO3, can account for considerable HNO3 formation in cloud but only during daylight hours. A heterogeneous mechanism consisting of NO3 and N2O5 absorption and reaction on droplets is shown to be a viable source of HNO3 in cloud during all hours.
Influence of oceanic heat transport upon the sensitivity of a model climate
Authors: Spelman M. J. , Manabe S.
Published: February 2008

The influence of oceanic heat transport on the sensitivity of climate to an increase of the atmospheric CO2 concentration is studied by comparing the CO2‐induced changes of two mathematical models. The first model is a general circulation model of the coupled ocean‐atmosphere system which includes ocean currents. In the second model the oceanic component of the first model is replaced by a simple mixed layer without ocean currents. Both models have limited computational domain with idealized geography and annual mean insolation. For each model, the sensitivity of climate is evaluated from the difference between the equilibrium climates of the normal CO2 and 4 times the normal CO2 concentrations. The results indicate that the presence of ocean currents reduces the sensitivity of surface air temperature because of the difference in magnitude of the surface albedo feedback effect. The poleward transport of heat by ocean currents raises the surface temperature at high latitudes, shifts poleward the margins of snow and sea ice, decreases the contribution of the albedo feedback effect, and reduces the sensitivity of climate. The equilibrium response of climate is compared with the transient response of climate to a sudden increase of atmospheric CO2 content. According to this comparison, the latitudinal dependence of the equilibrium response of zonally averaged surface temperature is qualitatively similar to the transient response approximately 25 years after the time of the sudden CO2 increase. This result suggests that the distribution of the zonally averaged temperature change in response to a gradual increase of atmospheric carbon dioxide also resembles the distribution of the equilibrium response provided that the characteristic time scale of the CO2 increase is longer than 25 years.
Turbulent current measurements in a wind‐wave tank
Authors: Lin Jung‐Tai , Gad‐el‐Hak Mohamed
Published: February 2008

Laboratory experiments were conducted in a wind‐wave tank to study the turbulence characteristics in the air and wave boundary layers generated by wind and waves. The turbulent air boundary layer over the water surface was surveyed using two hot‐wire probes. It was found to be a good simulation of an atmospheric boundary layer over a body of water. Capacitance probes were used to record the wave height. Spectra, wave phase velocity, dominant wavelength and frequency, and other statistics of the wind waves were computed. The water boundary layer below the water surface was surveyed using an array of 10 cross‐element hot‐film probes to measure the stream wise and vertical components of velocity. Various turbulence statistics including mean velocity, root‐mean‐square velocity fluctuations, Reynolds stress, dissipation rate, spectra, and higher‐order statistics were computed. Similarity profiles were found for the mean subsurface current and the rms turbulent fluctuations in the streamwise and vertical directions. The velocity spectra indicated the relative importance of the wave‐induced motion, which attenuated ex‐pontentially with depth.
Isotopic tracers in polar seas and glacier ice
Authors: Paren J. G. , Potter J. R.
Published: February 2008

The relationship between isotope concentration and salinity provides important evidence on the origin of water masses. In polar regions it can be used to deduce the isotopic composition of melting ice. We discuss a source of error implicit in the use of isotope salinity diagrams for this purpose. We argue that conventional δ18O and δD salinity diagrams should be abandoned in favor of (1 ‐ S) δ18O and (1 ‐ S) δD salinity diagrams which are physically more meaningful and which introduce no significant error.
Optimum expulsion of brine from sea ice
Authors: Criminale W. O. , Lelong M‐P.
Published: February 2008

A simple model is constructed to exploit the concept of drainage “trees” as observed during the process of expulsion for desalination of sea ice. Linear analysis is used together with a consistent approximation procedure for solution of the system to determine critical minimum Rayleigh numbers for the onset of instability. It is found that the system functions optimally when there is both a finite angle of tilt of the drainage channel as well as no tilt at all. The determination of the nonzero angle depends critically on the lateral mean density gradient, and numerical values for critical angles of inclination to the vertical obtained agree quantitatively with those reported.
Wind‐driven ice drift in a shallow sea
Authors: Overland J. E. , Mofjeld H. O. , Pease C. H.
Published: February 2008

The free‐drift equations are solved for ice floes in a shallow sea of neutral stratification, typical of many high‐latitude continental shelves. Solutions for ice drift and current velocity are obtained as a function of wind stress, ice thickness, and water depth. The ocean is modeled by second‐order closure, which allows continuous solutions from 5 m total depth to deep water. Results are presented with drag coefficients for the air/ice, ice/water, and water/bottom interfaces specified from recent surveys from the Bering Sea Shelf, a region with broad areas of water depths between 20 and 50 m. The solution shows little dependence on water depth for depths greater than 30 m. This occurs because turbulent mixing is a decreasing function of water depth and offsets other influences of finite depth. However, for water depths less than 30 m, ice velocities can change rapidly with wind speed and water depth, and the presence of turbulence from tidal shear is very important for coupling wind‐driven ice drift to the bottom. For the deep‐water limit, the second‐order closure solution confirms analytic solutions that indicate an increase of 20% in the ratio of ice speed to wind speed as the wind speed increases from 10 to 25 m/s.
Patterns of suspended particle distribution and transport in a large fjordlike estuary
Authors: Baker Edward T.
Published: February 2008

Seasonal and spatial patterns of the distribution and transport of suspended particles in Puget Sound, a large fjordlike estuary, are a product of the interaction of the subtidal circulation with surface and bottom particle sources. The particle distribution differs from the distribution of hydrographic properties and is characterized by four persistant features: (1) a thin (<10 m), high‐turbidity surface layer, (2) a thick (∼50 m), low‐turbidity zone centered around the level of no net motion between net seaward and landward flow, (3) horizontal particle fronts at the sill entrances, and (4) a bottom nepheloid layer maintained by local resuspension. Removal of particles from the surface waters by advective downwelling at the seaward sill and gravitational settling throughout the basin make Puget Sound an efficient particle trap. Particles sedimented on the basin floor are transported preferentially landward by the action of erosion/deposition cycles enhanced by fortnightly intrusions of new marine water.
An estimate of the upwelling rate in the equatorial Atlantic based on the distribution of bomb radiocarbon and quasi‐geostrophic dynamics
Authors: Wunsch Carl
Published: February 2008

Estimates of the near‐surface Upwelling in the tropical Atlantic ocean (15°S to 15°N), made by Broecker et al. (1978) from a radiocarbon box model and by Wunsch (1984) from a quasi‐geostrophic inversion, differ considerably (in the former case the range was estimated as about 17–20 Sv, while the latter obtained an absolute maximum of about 10 Sv). To understand these two apparently contradictory results, Δ14C constraints were added to the inverse model with realistic estimates of the observational errors in all fields (including the radiocarbon). It is found that the radiocarbon constraints are consistent with the quasi‐geostrophic model and with an upwelling estimated as 7–10 Sv. The near‐surface circulation in the tropical Atlantic is dominated by a northward flux of warm water across the equator necessary to feed the heat losses at high northern latitudes. The Δ14C balance is maintained by the advection of southern hemisphere waters of comparatively low radiocarbon concentration into the tropical zone by upwelling from below of very low radiocarbon water and by its removal to the north, also by advection. The major uncertainty in the radiocarbon calculations derives from the sparcity of sampling so that very great extrapolations are required to estimate the zonal mean Δ14C concentrations and the time histories between the prebomb period and 1972.
Analysis of a relationship between the vertical distribution of inorganic carbon and biological productivity in the oceans
Authors: Viecelli J. A.
Published: February 2008

If the assumption of steady state is made then over large temporal and spatial scales, a balance between the downward flux and oxidation of organic detritus and upward mixing of inorganic carbon determines the vertical distribution of inorganic carbon in the ocean. From a mathematical statement of this balance using an empirical formula for the downward organic flux determined by Suess (1980) I derive an expression for the vertical inorganic carbon profile containing one parameter Cp/k, the ratio of primary productivity measured by the 14C incubation method to trie effective vertical eddy mixing coefficient. The best estimate for this ratio obtained by minimizing the variances between the available inorganic carbon concentration data and the derived curve is 1.5×10−3 mol C m−4. This ratio is consistent with average primary productivities in the range of 100–170 gCm−2 yr−1 if one uses recent k value estimates based on radiocarbon and tritium measurements (Broecker et al., 1980; Stuiver, 1980; Stuiver and Quay, 1981) and is equivalent to 20–34 gCm−2 yr−1 of new production using the definition of Eppley and Peterson (1979).
Subinertial current oscillations in western Long Island Sound
Authors: Ullman David S. , Wilson Robert E.
Published: February 2008

The spatial structure of subinertial current fluctuations in a section across western Long Island Sound is investigated by using the method of empirical orthogonal functions. The variability in the deeper areas of the section is found to be dominated by a setup response to the longitudinal wind. Toward the southern side of the basin, much of the variance cannot be explained by this mechanism. Spectral analysis indicates that the currents in this area have increased short period variance, with periods between 40 and 55 hours, and tend to be highly polarized. A model of topographic waves in an infinite channel with a symmetric exponential bottom profile is shown to predict the polarization and cross‐channel structure of velocity fluctuations in this band. High rotary coherence between counter‐rotating current and wind components in this band, where the group velocity of the wave is nearly zero, suggests the possibility of a resonant response to wind forcing.
Mesoscale variability in marine winds at mid‐latitude
Authors: Overland James E. , Wilson Judith G.
Published: February 2008

Wind data were collected by the National Oceanic and Atmospheric Administration WP‐3D aircraft on low‐level (50 and 90 m) crosswind and along‐mean‐wind tracks of approximately 350 km during the Storm Transfer and Response Experiment in November and December 1980. Observed mesoscale variations in the marine wind fields are characterized by the velocity correlation tensor for three atmospheric regimes: cloud streets, open and closed cellular convection, and prefrontal warm air advection. The dominant scale of mesoscale variation in the offshore wind field normal to the mean wind direction in the case of old continental air flowing over a warmer ocean, producing cloud streets, was 27 km. For this case, the standard deviation in momentum transfer, which was calculated from 2‐km subsets of the flight track by the bulk aerodynamic method assuming a constant drag coefficient, was 13% of the synoptic scale (330km) mean. The dominant scale of mesoscale variation for open cellular convection was 62km, and the dominant scale for closed cellular convection was 90 km. The standard deviation of mesoscale momentum transfer (scales greater than 2 km; constant drag coefficient) for a 345‐km flight track containing both cell types was 26% of the synoptic scale mean. The warm air advection case had no measurable mesoscale variability. For each regime a model of the horizontal velocity correlation tensor, which can be used to estimate a mesoscale variability, is fitted to the observed velocity correlation tensor with velocity component and weather regime dependent coefficients. This general model is consistent with an interpretation of the mesoscale wind field as an ensemble of coherent structures, associated with cloud type, in which the spatial variability of the wind field in each weather regime is associated with physically determined dominant length scales (i.e., cells or rolls), as contrasted with a continuum interpretation of two‐dimensional turbulence. To accurately describe regional winds and fluxes at the sea surface, wind speed and temperature data should be averaged over the dominant mesoscale length scale with either a suitable time average or a spatial average, such as can be obtained by scatterometry, or an estimate of the mesoscale variability should be explicitly stated. It is also suggested that enhanced vertical flux in the oceanic mixed layer occurs at length scales of atmospheric boundary layer structures.
Conditions for interface surfacing, upper bounds on extent of ventilation, and formation of bottom lenses above topography
Authors: Cushman‐Roisin Benoit
Published: February 2008

Conditions under which the interface of a rotating, layered model can surface and form geostrophic fronts are investigated. It is shown how a simple one‐dimensional, reduced‐gravity model, despite its oversimplicity, can lead to surfacing criteria and upper bounds on the extent of the ventilation area created by the separation of two newly formed fronts. First a no‐surfacing theorem is established under restrictive conditions. Then, by relaxing conditions one by one, wind, coast, and topography effects are investigated and front properties derived. The present search for frontogenetical criteria and ventilation upper bounds, which per se is a novel approach to frontal studies, is aimed at complementing the existing frontal stability studies by offering additional information on front properties. Extension to multilayered and two‐dimensional models is briefly anticipated, calling for additional work before more general criteria can be formulated.
Local wind forcing of a coastal sea at subinertial frequencies
Authors: Lewis James K. , Reid Roberto
Published: February 2008

An analytical, normal mode, two‐layer model is presented that gives the response of a coastal region to local wind forcing. The model is linear and is developed in frequency space, the latter allowing one to compare the model responses directly with the results of current meter/wind data spectral and coherence analyses. The theoretical development indicated the requirement of a frictional parameter in both the barotropic and baroclinic modes to balance the wind stress at lower frequencies. Experimentation with the model and current and wind data collected 20 km off the Texas coast showed the requirement for both frictional effects throughout the subinertial frequency range. With appropriate frictional parameters, the model predicts the response of the Texas coastal region to local wind forcing quite well, using data from the fall and winter of 1978–1979. However, during the summer of 1978, the model consistently underpredicted the energy levels of the currents. Since the summer is a period of low wind stress energy for the Texas shelf, this underprediction most likely indicates the presence of nonlocally generated shelf wave phenomena.
Short‐term temporal variability of eolian particles in surface waters of the northwestern North Pacific
Authors: Uematsu Mitsuo , Duce Robert A. , Nakaya Shyu , Tsunogai Shizuo
Published: February 2008

The concentrations of particulate Al and total suspended particulate matter (TSP) were measured in surface waters at 42 stations on a cruise from Tokyo to Alaska and return during the summer of 1978. The mean particulate Al concentration in early July (5.5 μg kg−1) was almost 8 times higher than in mid‐August (0.72 μg kg−1). However, the mean TSP concentration was only twice as high. The high particulate Al concentration in the surface waters during early July was correlated with high atmospheric dust concentrations over this area. This dust was likely transported from the desert regions of central and eastern Asia. The data suggest that atmospheric mineral matter deposited on the ocean surface was removed to deeper waters within 1 month. The temporal variability of atmospheric concentrations and deposition of mineral matter may significantly affect the distributions and fluxes of this material in the North Pacific.
Variations in atmospheric mixing height across oceanic thermal fronts
Authors: Hsu S. A. , Fett Robert , La Violette Paul E.
Published: February 2008

When an oceanic thermal front is under the influence of an atmospheric high‐pressure system, differences in atmospheric mixing height across the front exist, mainly because of the gradient in the sea‐surface temperature (SST). To study and estimate these differences, an analytical model based on a basic thermodynamic equation is devised. The model states that ΔH = KΔT, where ΔH and ΔT are the difference in the mixing height in meters and SST in degrees Celsius across the front, respectively, and K (in m/°C) is related to the entrainment coefficient, wind speed, transfer coefficient for sensible heat flux, local change of the potential temperature in the mixed layer, advection due to winds, and radiative processes due to clouds. On the basis of pertinent field experiments conducted over the Gulf Stream, in the Korea Strait, and over the Alboran Sea, the composite value of K is found to be approximately 38 m/°C. The limitation of using a constant K is discussed.
Determination of wave height spectrum by means of a joint probability density function
Authors: Yamazaki Hidekatsu , Herbich John B.
Published: February 2008

Most of the wave information systems are based on the spectral representation of the observed wave data. Spectral analysis describes the wave energy distribution as a function of frequency for a given wave data set. However, spectral analysis may not provide the joint statistical distribution of wave heights and periods. An alternative spectrum estimation by means of the joint probability density function of wave heights and periods is presented. The wave height joint probability spectra are defined as the second moment of wave height of joint probability in terms of the frequency domain. Good agreement between the joint probability density spectra and fast Fourier transform and autoregressive spectra was obtained.
Velocities, turbulence, and skin friction in a deep‐sea logarithmic layer
Authors: Gust Giselher , Weatherly Georges L.
Published: February 2008

Speed, turbulence, skin friction, and drag measurements made with metal‐clad hot wires, epoxy‐coated hot films, and Savonius rotors are reported for a deep‐sea boundary layer at a water depth of ∼5000 m. They include data from heights z < 30 cm, a region hitherto only investigated in detail by Chriss and Caldwell (1982) for a shelf site. A mean speed logarithmic layer was observed at 3 < z < 200 cm. The difference between the friction velocity u*log determined from the speed profiles and the skin friction u*skin measured by flush‐mounted hot films was statistically significant at the 95% level in five out of eight analyzed burst intervals. This result suggests form‐drag influence on the vertical mean flow profile. Although identified from the mean speed data as a hydrodynamically rough boundary layer, the turbulence and bottom stress intensities at the deep‐sea site were found to be reduced by more than 40% compared to smooth‐wall open‐channel flow and planetary boundary layers. Applicability of the universal law of the wall has not been confirmed for this deep‐sea boundary layer.
Density and velocity fine structure enhancement in oceanic eddies
Authors: Miller Jerry L. , Evans David L.
Published: February 2008

Advection‐diffusion models of the oceanic thermocline require a global ocean, mean vertical eddy diffusivity of about 1 cm2 s−1; however, maximum values estimated from microstructure measurements at mid‐gyre locations are generally smaller and, occasionally, 1–2 orders of magnitude less, depending on the particular assumptions made by individual analysts. Mesoscale features are high kinetic energy sources, which may fuel vertical mixing mechanisms on fine structure scales, resulting in local enhancements of eddy diffusivity above the canonical value of 1 cm2 s−1. The effects of one such mechanism, the Kelvin‐Helmholtz instability, are assessed for a Gulf Stream ring and a mid‐thermocline eddy. The necessary Richardson numbers are computed from Yvette profiles obtained in these features and are accurate to within about 10% for Ri = 1, and more accurate at the critical value Ri = 0.25. A plausible extension of the Miles‐Howard theorem for a nonparallel shear flow is formulated for a two‐dimensional perturbation. The shear appropriate for this Richardson number calculation is well approximated by the total shear for slowly depth‐varying direction, as is the case for the vast majority of the data. Upper and lower bounds on the vertical scale for the Richardson number calculation are set by the shear spectra and the Ozmidov scale. Median Richardson number was lower toward the center of the eddy because of a large decrease in Brunt‐Vaisala frequency (N2) and was depressed on the fringes by high shear. Lower median Ri is also found at the center of the ring as a result of low N2. Lower bounds on vertical eddy diffusivity are estimated based on the assumptions of a simple, mixing‐length model and of complete mixing of each region where Ri is less than 0.25. The spatial distribution of this quantity within the eddy and the ring mirrors that of median Ri. Values range from Az ∼ 1.1 cm2 s−1 near the center of the eddy and 0.90 cm2 s−1 near the center of the ring to zero in regions outside of the features where no Ri less than 0.25 were observed.