bluuebunny/crossref_metadata_2025 huggingface dataset:
Energy saturation and phase speeds measured on a natural beach
Authors: Thornton Edward B. , Guza R. T.
Published: February 2008

Field measurements of wave height and speed from 7‐m depth shoreward are described. The experiment plan consisted of a shore‐normal transect of closely spaced (compared to a dominant wave length) velocity, pressure, and elevation sensors on an almost plane profile having an inshore slope of 1:50. As the waves shoal and begin to break, the dominant dissipative mechanism is due to turbulence generated at the crest, and wave heights become increasingly depth controlled as they progress across the surf zone. Wave heights in the inner surf zone are strongly depth dependent; the envelope of the wave heights is described byHrms= 0.42 h. The depth dependence of the breaking wave height is shown to be related to the kinematic instability criterion. Celerity spectra were measured by using phase spectra calculated between pairs of adjacent sensors. Inshore of 4‐m depth, the celerity was found distant over the energetic region of the spectrum. A ‘mean’ celerity was compared with linear theory and was within +20% and −10%, showing good agreement for such a nonlinear, dissipative region.
The structure of circulation: MESA physical oceanographic studies in New York Bight, 2
Authors: Mayer Dennis A.
Published: February 2008

The structure of velocity in New York Bight (NYB) is examined for motions in the low frequency meteorological band (periods greater than 3 days) and for those in the semidiurnal band during the years 1975, 1976, and 1978. An empirical modal analysis suggests that, in the lower part of the water column in the unstratified season, nearly 80% of the low frequency energy is in phase across the shelf and is organized along the major isobaths. These motions exhibit a remarkable coherence that is visually apparent across the shelf for distances up to 80 km. Near‐surface motions are less organized presumably because of the surface wind stress field. Maximum coherence between the observed wind stress and currents occurs with wind angles that vary from 60°T near the New Jersey coast to 80°T at mid‐shelf just northeastward of the Hudson Shelf Valley which is consistent with the analysis of sea level records by Wang [1979]. Wind‐coherent motions represent about 50% of the low frequency energy in the northern section of NYB off Long Island and as much as 70% in the southern section off New Jersey. The analysis suggests the existence of a wind‐coherent disturbance propagating south westward on the outer shelf at about 540 km/day. This phase speed is consistent with earlier studies [Ou et al., 1981]. In the higher frequencies, the M2 semidiurnal tidal current is in phase and rotates clockwise throughout NYB with the major axes organized approximately across the shelf.
A time‐dependent ice sheet model: Preliminary results
Authors: Bindschadler Robert A. , Gore Robert
Published: February 2008

A numerical model of ice sheet flow is developed, and preliminary results are described. This model includes vertical resolution of temperature, stress, and strain rate which represents a considerable improvement over previous vertically averaged ice sheet models. The model follows the flow of ice along a flow line within an ice sheet drainage basin. Longitudinal stresses and basal sliding are included. Basal sliding is dependent on the base shear stress and a specified distribution of basal water pressure. The numerical methods used to solve the coupled set of stress and velocity equations for the static and time‐evolutionary cases are discussed. A steady state profile simulating an ice stream is calculated for a particular set of input parameters, and changes in the profile are examined for different choices of parameters. Preliminary studies of response behavior are completed using a simplified ice sheet geometry with a fixed terminus or grounding line. The results of these studies illustrate ice sheet thinning in response to a lowered sea level or to a reduction in the extent of ice rises (or pinning points) within ice shelves.
A new method for measuring radon exhalation
Authors: Fernandez P. , Quindos L. S. , Soto J. , Villar E. , Guedalia D.
Published: February 2008

A method for measuring radon exhalation based on the determination of radon profile into the soil by gamma spectrometry using an INa(Tl) detector is developed. Detection efficiency is determined by employing Monte Carlo method. Experimental results are described, and they show the workability of the method.
Bathymetric prediction from SEASAT altimeter data
Authors: Dixon T. H. , Naraghi M. , McNutt M. K. , Smith S. M.
Published: February 2008

The linear response function technique is used to analyze two 1300‐km tracks of SEASAT altimeter data and corresponding bathymetry in the Musician Seamounts region north of Hawaii. Bathymetry and geoid height are highly correlated in the 50‐ to 300‐km wavelength range. A predictive filter is developed which can operate on SEASAT altimetry in poorly surveyed oceanic regions to indicate the presence of major bathymétrie anomalies. Modeling of the bathymetry‐geoid correlation in the Musician region is attempted using the elastic plate model. The flexural rigidity D of the plate is not well constrained by our data but appears to lie in the range 5×1021 N m ‐ 5×1022 N m at the time of loading. Since the Musician Seamounts and the crust on which they lie are both Late Cretaceous in age, this value represents the effective flexural rigidity of very young lithosphere that was ‘frozen in’ at the time of voicanism, The modeling indicates that the general form of a predictive filter will strongly depend on various geologic parameters, especially the effective flexural rigidity. Hence, some a priori geologic constraints are necessary to estimate successfully the bathymetry from the altimeter data. Alternately, if high‐quality bathymetry is available, a crude estimate of the age of loading (i.e., voicanism) can be made from the altimeter data.
First SEASAT altimeter data analysis on the western Mediterranean Sea
Authors: Bernard J. , Barlier F. , Bethoux J. P. , Souriau M.
Published: February 2008

Within recent years, a new satellite technique has been successfully developed for studying the oceans: altimetry. The SEASAT experiment presents a particular interest because of the great accuracy of the altimeter data, though its capabilities are bounded by the accuracy of the trajectory restitution. The altimetric signal variations result from both marine and tectonic effects, the discrimination of which may be difficult. In the present study on the western Mediterranean Sea, the altimeter data processing, the satellite trajectory, and the geoid features are considered. The satellite topography of the Mediterranean Sea surface shows irregularities which are 1 order of magnitude greater than the expected oceanic effects and so are mainly connected to the earth structure. In fact, in spite of neglecting the oceanic effects, correlation with emerged land (islands) or immerged land (bathymetry) and also with main tectonic features can be seen. In particular, evidence exists for isostatic compensation of Airy type in the continental margins and oceanic areas.
Coastal sea level response to frontal passages on the Louisiana‐Texas shelf
Authors: Chuang Wen‐Ssn , Wiseman William J.
Published: February 2008

Sea level variations resulting from wind forcing along the Louisiana‐Texas shelf are examined on 5‐month winter records. Local weather patterns during the winter are dominated by cold‐front passages. The associated surface wind field is well organized, predominantly in the cross‐shelf direction. Regional sea level response, however, shows considerable variability; it is mainly a response to alongshore wind at Galveston, but cross‐shelf wind at Eugene Island. This spatially nonuniform response appears to be due to the different water depth over the inner shelf, which is shallower off Eugene Island and favors direct cross‐shelf wind setup. A friction model is applied to each region, and the results compare well with observations.
Numerical simulation of the Weddell Sea pack ice
Authors: Hibler W. D. , Ackley S. F.
Published: February 2008

To investigate the role of ice dynamics on the seasonal cycle of Antarctic sea ice, a series of 2‐year simulations of the Weddell Sea pack ice are carried out. The simulations employ the dynamic thermodynamic model developed by Hibler (1979) and use a 1‐day time step on an 18×15 grid with a resolution of 222 km. Daily atmospheric data from 1979 are used to drive the simulations. With atmospheric temperature fields modified to reflect buoy observations, the simulations yield a seasonal cycle of ice with maximum and minimum extents close to that observed. Except for portions of the western Weddell, the advance of the ice is found to be primarily thermodynamic in nature, while the rapid decay depends critically on the presence of both leads and lateral ice advection. The average fraction of open water is substantial even in winter, and varies from a minimum of 10% in September to a maximum of 35% in March. These values are in general agreement with estimates from satellite microwave data. In early summer the ice motion causes a residual tongue of ice to extend eastward from the Antarctic Peninsula in agreement with observations. Mean ice thicknesses are consistent with observations and vary from about 3 m in the perennial ice in the western Weddell to 1 m in first‐year ice in the eastern Weddell. Possible feedback between the ice extent and atmosphere are investigated by simulations with the surface air temperatures constrained to below‐freezing values in the presence of ice. These ‘coupled’ simulations yield a more realistic rapid decay in summer with dynamics included, but an unrealistically small decay without dynamics. Simulated ice drift results yield mean drift rates of about 5 km/day, in good agreement with buoy drift observations but with slightly inadequate northward transport in the western Weddell. Near the ice edge the drift rates are relatively insensitive to the ice strength. Near the coast, however, lower strengths are found to yield a decrease in northward drift rates.
Evidence for quasi‐periodic components in Dobson network total ozone records
Authors: Guthrie Paul D.
Published: February 2008

Power spectrum analysis has been applied to the total ozone time series at each of a sample of Dobson stations with records of more than 15 years in the interval 1957 to 1981. The distributions of strongly periodic or quasi‐periodic signals in these spectral estimates, for three spectral estimators and two levels of confidence, show distinct features. These appear at the previously known or suspected periods of 3.5–4.0 years, 27 months, and 21 months as well as the previously unreported period of 11.5 months. Possible geophysical implications are discussed.
Corona point measurements in a thundercloud at Langmuir Laboratory
Authors: Weber M. E. , Stewart M. F. , Few A. A.
Published: February 2008

A meteorological radiosonde, modified by the attachment of vertically oriented, pointed, metal rods, and associated insrumentation, was released beneath a thundercloud at Langmuir Laboratory, New Mexico. In addition to information on temperature and winds, the instrument provided an estimate of the vertical component of the cloud electric field by measurement of corona current induced in the rods. Charge volumes inferred from the sounding were (1) negative charge at 6.6 km msl (temperature −12°C), where northwesterly winds apparently advected the charge toward the cloud's most intense precipitation echoes, (2) positive charge at 11.6 km msl (−50°C) where the winds flowed northward into the cloud's anvil, (3) a 200‐m‐thick screening layer of negative charge at the cloud's upper surface, and (4) a small, concentrated region of charge near the cloud base. These charged regions were evident in volumes of low precipitation intensity (log Z ≲1.5), which were well away from the storm's convective center.
Vertical dispersion of inertial waves in the upper ocean
Authors: Rubenstein David M.
Published: February 2008

A linear model of the vertical dispersion of near‐inertial waves is developed. A porosity distribution near the bottom of the computational domain minimizes bottom reflections and simulates an ocean of infinite depth. The model is used to show that the vertical dispersion of near‐inertial waves in the upper ocean may, under certain conditions, contribute significantly to the observed rapid decay of inertial oscillations in the surface layer. The kinetic energy of inertial oscillations at mid‐latitudes decays with an e folding time scale of 10 days or less, when the parameter λ(km)/N(cph)d(m) is less than or of the order of unity, where λ is the wavelength of the wind‐generated near‐inertial waves, N is the Väisälä frequency in the upper pycnocline, and d is the surface layer thickness. At the top of the pycnocline the model predicts a velocity maximum, which develops as energy propagates downward, out of the surface layer. However, when the upper pycnocline is sufficiently peaked, a resonant frequency interference effect is predicted. This effect modulates the dissipation of surface layer inertial oscillations, and their magnitude after a storm need not decay monotonically. We also make qualitative comparisons with deep‐ocean current meter observations taken during the Mixed Layer Experiment (MILE) and with shallow water (105 m) observations taken in the Baltic Sea.
Physical/biological structure and exchange across the thermohaline shelf/slope front in the New York Bight
Authors: Houghton Robert W. , Marra John
Published: February 2008

During the summer, the shelf/slope water from in the New York Bight is thermohaline with strong temperature and salinity gradients occuring on isopycnals connecting shelf and slope water. The dominant lateral exchange is via slope water intrusions above and below the cold pool, a remnant of winter‐mixed shelf water. These intrusions create environments favorable for double‐diffusive processes. However, measured values of the density ratio Rρ over the shelf imply weak vertical mixing (Kυ∼10−1 cm−1), which is consistent with heat and salt fluxes into the persistent cold pool. Convergent circulation driven by cabbeling and vertical mixing enhanced by double‐diffusion at the outer edge of the cold pool may be responsible for the abrupt deepening of the chlorophyll a maximum layer.
On Gulf Stream variability and meanders over the Blake Plateau at 30°N
Authors: Lee Thomas N. , Waddell Evans
Published: February 2008

Current and temperature variability of the Gulf Stream at 30°N was observed with a subsurface array of current meter moorings from August 1980 to October 1981. Energetic current fluctuations in the 2–14 day period band accounted for 45–70% of the total observed variability. Flow perturbations in the cyclonic shear zone tended to have a cyclonic sense of rotation and were 180° out of phase from anticyclonic flow perturbations within the anticyclonic shear region. These fluctuations appear to result from northward propagating wave‐like meanders of the Gulf Stream axis. The fluctuations do not appear to be directly related to local wind forcing. Observations of near‐bottom flow on the Blake Plateau east of the Gulf Stream showed periods of prolonged southward currents lasting up to 40 days with speeds in excess of 30 cm s−1. The mean flow was also southward due to these strong events. The source of the southward flow is unknown. It may be connected to cold‐core eddies that are not detectable in the surface with remote sensing or possibly a remnant of the southward undercurrent that has been observed beneath the Gulf Stream off Cape Hatteras and on the deep slope of the Blake Escarpment.
Stratospheric NO2: 3. The effects of large‐scale horizontal transport
Authors: Noxon J. F. , Henderson W. R. , Norton R. B.
Published: February 2008

This paper discusses several extended sets of measurements of stratospheric NO2 near 20°N and in the region 40°N–70°N. The principal concern at high latitude is with the relation between the NO2 column abundance and quasi‐horizontal flow patterns in the stratosphere near 30 km. It appears that NO2 can serve as a tracer of such flow, particularly at higher latitude in winter when the flow is rapid in comparison with the rate of photochemical readjustment. When polar air, originally low in NO2, is delivered to lower latitude, one observes a drop in NO2 abundance; the drop is less the lower the latitude of observation owing to the greater time available for NO2 to be released from the polar night storage species. A study of total ozone column abundance and the flow at 100 mbar indicates a close relation between them similar to that for NO2 at higher altitude.
Poker Flat MST radar observations of shear‐induced turbulence
Authors: Smith Steve A. , Romick Gerald J. , Jayaweera Kolf
Published: February 2008

Wind speed and Cn2 measurements made with the Poker Flat, Alaska, MST radar are used to study the development of clear air turbulence (CAT) near the tropopause. Arguments and observations indicating that Cn2 is proportional to the intensity of turbulence are presented. The relationship between wind shear and turbulence is examined by using time‐lagged cross correlations between vertical wind shear and log Cn2 time series. From analysis of data taken with spatial resolutions of 2200 m and 750 m, it is found that the correlation improves as the time and spatial resolutions of the measurements improve. The implications for forecasting CAT are discussed, based on the correlation results and a comparison of radar data with National Weather Service CAT forecasts.
Variations in atmospheric angular momentum on global and regional scales and the length of day
Authors: Rosen Richard D. , Salstein David A.
Published: February 2008

Twice‐daily global analyses of the zonal winds prepared by the U.S. National Meteorological Center for the period from January 1, 1976, through December 31, 1981, have been used to construct a time series of the atmosphere's angular momentum (M). This series is spectrally analyzed and compared with independent observations of changes in the solid earth's rate of rotation. The most prominent feature in the M time series is an annual signal, and this is mirrored by similar behavior in changes in the length of the day (l.o.d.). Other noteworthy fluctuations in M and l.o.d. on time scales of less than a year also occur, however, and these too agree well with each other. In this regard, a near 50‐day fluctuation in both time series, also noted in other studies, is especially visible. We conclude on the basis of these comparisons that indeed most of the variability in our time series for M is real and that, as others have suggested, the atmosphere plays a dominant role in forcing changes in l.o.d. on time scales of about a year and less. We divide the globe into a number of belts to investigate the contributions made by different parts of the atmosphere to the changes found in the global statistic M. Our approach is to calculate empirical orthogonal functions that define the major spatial modes of variation among the regional time series of angular momentum. As expected, we find the annual cycle in M is associated with seasonal changes in the major jet streams of the two hemispheres, with the larger of these changes occurring in the northern hemisphere. Nonseasonal changes in M emerge from the imbalances among regional variations in momentum, with the largest contributions on time scales less than a year coming from the regions 10°–25°S and 20°–35°N.
The variation with frequency of the long‐period tides
Authors: Carton J. A.
Published: February 2008

The oceanic response to long‐period tidal forcing in closed basins approaches equilibrium for periods much longer than a month for moderate values of dissipation. At a given frequency the response is closest to equilibrium near the eastern wall of the basin. Global calculations of the Mf and Mm tides, made using a 2°×2° grid, are presented. Changes in the length of day have also been computed for these tides.
Frequency analysis of wave heights based on wave envelope
Authors: Tayfun M. Aziz
Published: February 2008

Analysis and prediction of the heights of sea waves in terms of a conventional crest‐to‐trough definition present practical and theoretical difficulties. As a closely related alternative, the envelope of waves can directly be used as a reference for a wave height measure that is continuous in time. This concept is explored to show that not only it is consistent with the theoretical specification of irregular waves but that it also provides a remarkably efficient approach for the frequency analysis of wave heights in typical applications. Theoretical arguments and a specific case study reveal that the proposed approach generates frequency estimates which are improved in statistical quality and compare better with the available theories on the distribution of wave heights.
An observational study of water vapor in the mid‐latitude mesosphere using ground‐based microwave techniques
Authors: Bevilacqua R. M. , Olivero J. J. , Schwartz P. R. , Gibbins C. J. , Bologna J. M. , Thacker D. J.
Published: February 2008

Ground‐based spectral line measurements of the 22.2‐GHz water vapor atmospheric emission line are used to deduce the mesospheric water vapor profile. The results generally indicate that the water vapor mixing ratio is independent of height or increases slowly in the 50‐ to 60‐km range with typical values of between 5 and 8 parts per million by volume (ppmv). (Thacker et al. (1981) give an analysis of the 1980 data sets obtained in this experiment, which indicated the existence of a pronounced layer of water vapor near 65 km. The reanalysis of these data contained in this paper, which includes the estimation and removal of spectral baselines, results in marked smoothing of the water vapor mixing ratio profile in the lower mesosphere, and the peak is much less pronounced.) Above 65 km the mixing ratio is seen to decrease rather rapidly to values of near 1 ppmv at 85 km. This decrease is far steeper than that expected from photochemical considerations. There has also been a large amount of variability observed in the water vapor profiles, especially on the day‐to‐day time scale. The water vapor retrievals have been used to estimate the vertical component of the upper mesospheric eddy diffusion coefficient (Kz). This analysis has indicated either that vertical transport time scales in the mesosphere are perhaps an order of magnitude longer than previous studies have shown or that present understanding of the factors important in controlling the vertical distribution of water vapor in the mesosphere is inadequate.
The reaction NH2 + PH3 → NH3 + PH2: Absolute rate constant measurement and implication for NH3 and PH3 photochemistry in the atmosphere of Jupiter
Authors: Bosco S. R. , Brobst W. D. , Nava D. F. , Stief L. J.
Published: February 2008

It has been suggested that the photochemistries of NH3 and PH3 are linked in the upper atmosphere of Jupiter. Specifically, the reaction NH2 + PH3 → NH3 + PH2 would, if the rate were fast enough at Jovian stratospheric temperatures, regenerate ammonia in the upper atmosphere while at the same time accelerating the decomposition of phosphine. The absolute rate constant for this reaction has been measured over the temperature interval 218–456 K using the technique of flash photolysis‐laser‐induced fluorescence (FP‐LIF). NH2 radicals were produced by flash photolysis of ammonia highly diluted in argon, and the decay of fluorescent NH2 photons was measured by multiscaling techniques. At each of the five temperatures employed in the study the results were shown to be independent of variations in [PH3], total pressure (Argon), and flash intensity (i.e., initial [NH2]). The rate constant results are best represented for 218 ≤ T ≤ 456 K by the expression k = (1.52 ± 0.16) × 10−12 exp (−928 ± 56/T) cm3 molecules−1 s−1, where the error quoted is 1 standard deviation. This represents the first determination of the rate constant for the reaction NH2 + PH3. The data are compared with an estimate made in order to account for results of the radiolysis of NH3‐PH3 mixtures. The Arrhenius parameters determined here for NH2 + PH3 are contrasted with those for the corresponding reactions of η and OH with PH3. The results are also discussed theoretically and the implications considered for models of the photochemistry of the atmosphere of Jupiter. Since we now find that the rate constant for the reaction NH2 + PH3 → NH3 + PH2 is 2 orders of magnitude shower than required in the model, it appears that this reaction can make only a negligible contribution to both the recycling of NH3 and the decomposition of PH3 in the upper atmosphere of Jupiter.
Large‐scale atmospheric mixing derived from meridional profiles of krypton 85
Authors: Weiss W. , Sittkus A. , Stockburger H. , Sartorius H. , Münnich K. O.
Published: February 2008

Two north‐south sections of the atmospheric concentration of 85Kr are presented. The most striking feature of these sections is a large concentration jump at the respective geographical position of the intertropical convergence. In October 1980 the 85Kr concentration of the northern hemisphere was about 1.5 pCi/m3 higher than the one observed in the southern hemisphere. Due to a temporal increase of the northern 85Kr concentrations the concentration difference observed in March/April 1981 was 2.5 pCi/m3. Hemispheric residence times of 1 and of 1.7 years are estimated from the two 85Kr sections. The poleward increase of the northern 85Kr concentrations is in agreement with a meridional diffusivity of 1.6×1010 cm2/s. Five years of a continuous 85Kr record from two stations at 47.9°N, 7.8°E (difference in altitude 1000 m) are presented. The data show a temporal increase of 0.5 pCi m−3 yr−1, a seasonal variability with an amplitude of 1–2 pCi/m3, and numerous peaks. Most of the peaks originate from European 85Kr sources. It is estimated that the yearly contribution of these sources to the global 85Kr discharge is at least 10%. The seasonal variability of the 85Kr concentrations is tentatively explained by the seasonality of the vertical mixing intensity within the lower atmosphere.
Temporal distributions of radiostrontium isotopes and radon daughters in rainwater during a thunderstorm
Authors: Burchfield L. A. , Akridge J. D. , Kuroda P. K.
Published: February 2008

The concentrations of 89Sr, 90Sr, 137Cs, 210Pb, 212Pb, and 210Po were measured in sequentially sampled rainwater during a thunderstorm occurring at Fayetteville, Arkansas, on January 29, 1981. Approximately concordant mean residence times ranging from 43 to 136 days were obtained from the observed ratios of 89Sr/90Sr and 210Po/210Pb. The 212Pb/210Pb ratio was found to correlate negatively with the 210Po/210Pb ratio. The variation of the 212Pb/210Pb ratio appeared to have resulted from turbulent mixing of air masses, and it increased sharply after the rainfall reached a peak value.
Current response at the shelf break to transient wind forcing
Authors: Petrie Brian D.
Published: February 2008

An analysis of current meter and hydrographic data collected from an array of moorings situated at the shelf break off Nova Scotia is presented. In particular, the focus is on the ocean response to moderate (10 to 20m s−1) transient winds of two or more days duration blowing parallel to the local bathymetry. Under these conditions, upwelling occurs at the shelf break from depths of 400 m and with peak vertical velocities of about 2 mm s−1. The upwelling appears to be confined to within 10 km of the slope. Acceleration, Coriolis, and pressure‐gradient terms are important for the along‐ and cross‐slope momentum balances. Local topographic variations contribute to the anomalously large bottom currents on the shoreward side of the shelf break. Both coastal sea level and the shelf break circulation respond coherently to synoptic wind forcing, but quantitative agreement with two‐layer shelf models is poor.
Rotating‐fluid experiments with an atmospheric general circulation model
Authors: Geisler John E. , Pitcher Eric J. , Malone Robert C.
Published: February 2008

The traditional apparatus for rotating‐fluid experiments in the laboratory is an annular container of fluid situated on a turntable. A fundamental difficulty in applying to atmospheric circulation problems the knowledge and understanding of the behavior of rotating fluids gained from these experiments is the geometrical difference between a rotating annulus and a rotating spherical shell. With a view toward identifying features of rotating fluid flow that are dependent on the geometry, we have undertaken rotating annulus‐type experiments with a numerical model in spherical coordinates. Rather than construct and test a model specifically for this purpose, we found it expedient to modify an existing general circulation model of the atmosphere by removing the model physics and replacing the lower boundary with a uniform surface. We present here a regime diagram derived from these model experiments, interpret its major features, and contrast these with the major features of rotating annulus regime diagrams. A narrow region where one or two zonal wave numbers are dominant is found within the wave regime. In contrast to the situation in the annulus, there is no upper symmetric regime in our results, and wave activity at low rotation rates appears to be maintained by barotropic rather than baroclinic processes
The two‐scale radar wave probe and SAR imagery of the ocean
Authors: Plant William J. , Keller William C.
Published: February 2008

A two‐scale formulation of oceanic backscatter of microwave radiation, which has previously been applied to the dual‐frequency scatterometer, is applied here to the two‐scale radar wave probe and SAR imagery of the ocean. A two‐scale radar wave probe is a microwave system which coherently detects signals scattered from a very small patch of the ocean surface. It is shown that a SAR image may be described as a convolution of the AM part of the output of a two‐scale wave probe with the power spectrum of the FM part of the output. Thus SAR images are not faithful reproductions of cross‐section variations over the surface. Distortions occur as a result of variable surface velocities. Examples of this distortion are derived from two‐scale wave probe data taken in the Gulf of Mexico. Application of a focusing correction does not remove the distortion from the simulated image of a nearly sinusoidal, azimuth‐traveling wave. Large V/R0 ratios minimize the distortion, however.
Nitric oxide in the upper stratosphere: Measurements and geophysical interpretation
Authors: Harvath J. J. , Frederick J. E. , Orsini N. , Douglass A. R.
Published: February 2008

A rocket‐borne parachute‐deployed chemiluminescence instrument has obtained seven new measurements of atmospheric nitric oxide for altitudes between 30 and 50 km at mid‐latitudes. These results, when combined with profiles measured by an earlier version of the instrument, cover all four seasons and provide a more comprehensive picture of upper stratospheric nitric oxide than has been available previously. At the highest altitudes studied, the vertical gradient in mixing ratio displays positive and negative values during different observations with the largest values tending to appear at the greatest heights in summer. Examination of the differences among the profiles, which exceed a factor of 3 near the stratopause, suggests that they arise from the action of transport processes which carry air into the mid‐latitude upper stratosphere from regions of the atmosphere that contain widely different odd‐nitrogen abundances.
Methane sulfonic acid in the marine atmosphere
Authors: Saltzman E. S. , Savoie D. L. , Zika R. G. , Prospero J. M.
Published: February 2008

Methane sulfonic acid (MSA) is an oxidation product of the reaction of OH radical with dimethyl sulfide and, hence, should be an important constituent of marine air. MSA concentrations in marine aerosols ranged from 0.009 to 0.075 μg/m3 in samples from the Pacific and Indian oceans and Miami, Florida. In the samples from remote areas (Pacific and Indian oceans), MSA levels averaged 6.7% (S = 1.9) of the non‐sea‐salt (nss) SO4=. In the Miami area, ratios were occasionally lower because of the impact of local sulfur emissions (probably pollutant SO2). MSA concentrations in seven rainwater samples collected at Miami, Florida, ranged from 0.001 to 0.034 ppm. Cascade impactor samples from Miami, Florida, and the Gulf of Mexico indicate that MSA occurs primarily in the smaller particles, as does nss SO4= values. In the two samples analyzed, MSA is concentrated on slightly coarser particles than nss SO4=. The size distributions of both MSA and nss SO4= differ markedly from that of sea salt Na+, suggesting that at least the first step in the oxidation of organosulfur compounds is a gas phase reaction. The observed concentrations of MSA in marine air are the result of formation from gas phase reaction of dimethyl sulfide (and other volatile organosulfur compounds) with OH radical and destruction by aqueous phase reaction with OH radical in aerosols. Preliminary experiments indicate that MSA oxidation probably yields SO4= under atmospheric conditions. Therefore, MSA destruction is a potentially important pathway for the formation of nss SO4= in the marine atmosphere. The magnitude of the fluxes involved in the organosulfur cycle cannot be calculated from the MSA data because of the uncertainty in the free radical chemistry of aerosols.
10Be/9Be ratios in recent and ancient mollusks
Authors: Kaufman A. , Magaritz M. , Peters B. , Goldbert M. B. , Kaim R. , Gerber J. , Hering W. , Paul M. , Henning W. , Kutschera W. , Brenner I. B.
Published: February 2008

Marine mollusk shells from various oceans and seas were analysed for their concentration of 10Be by accelerator mass spectrometry (AMS) and of 9Be by inductively coupled plasma atomic emission spectrometry (ICPAES). The ratio 10Be/9Be varied appreciably for different shells, indicating strong dependence on local conditions. However, the lowest ratio was measured in a Pleiocene shell from Italy, consistent with its age of 2.5 to 3 million years.
A note on linear surface wave‐current interaction over slowly varying topography
Authors: Kirby James T.
Published: February 2008

A mild slope wave equation is derived which governs the propagation of linear surface waves in the presence of large ambient currents. The equation is shown to differ from two previously derived models, and arguments for the validity of the new version in comparison to previous versions are presented. A linearized evolution equation and parabolic equation approximation are constructed in order to show the correspondence between the present corrected version and a previously derived version of the time‐dependent Schrödinger equation.
Interactions of nearshore bars with incoming wave groups
Authors: Symonds G. , Bowen A. J.
Published: February 2008

Results from a theoretical model of long wave generation by a time varying break point over a linear shore parallel bars are presented. Standing wave solutions between the shoreline and the mean break point over the bar are obtained, and two possible resonance conditions are identified. First, a quarter wave resonance condition is defined, having a node in the sea surface elevation at the forcing region over the bar. Second, a half wave resonance occurs when the surface elevation has an antinode at the bar crest. The model results predict a resonant response corresponding to the half wave resonance but a quarter wave resonance is not seen, the response being limited by an outgoing energy flux in the form of a seaward propagating progressive wave. The occurrence of an elevation antinode at the bar crest leads to the possibility of convergence in suspended load at this point and hence to a possible mechanism for the maintenance of the bar. At resonance the constructive modes, those tending to maintain the bar, are amplified, while the destructive modes, those tending to create a trough at the bar position, are actually suppressed by the topography.
Observations and simulation of a bottom Ekman layer on a continental shelf
Authors: Dickey T. D. , Van Leer J. C.
Published: February 2008

A numerical model was used to simulate the bottom Ekman layer of a continental shelf region. The basis for the model was the Mellor and Yamada level
turbulence closure scheme. Conservation equations for momentum, turbulent kinetic energy, and turbulent length scale were utilized in the model. The model was used to simulate data taken from a Cyclesonde mooring on the Peruvian continental shelf in May 1976 as part of the Joint II Coastal Upwelling Ecosystems Analysis program. The Cyclesonde provided mean horizontal velocity, temperature, salinity, and pressure data. An intense poleward undercurrent drove the bottom flow regime. The most striking feature of the data was the clockwise Ekman veering of velocity vectors as the bottom was approached. A 48‐hour period was chosen for the model simulations. The vertical profile of speed (48 hours mean) simulated by the model fell within the error bars of the data. The corresponding Ekman spiral display of the model results also showed good agreement with the observations.
Interannual variations and longer‐term changes in the sea state of the North Atlantic from 1970 to 1982
Authors: Neu H. J. A.
Published: February 2008

A 13‐year (1970–1982) time series of 12‐hourly wave charts of the North Atlantic has been analyzed for variations in the sea state. Two types of variation were determined: first, strong 3‐ to 7‐year fluctuations; second, a continuous increase in the sea state during the 13 years. It appears that the former is the result of variations in cyclonic activities over the western North Atlantic and that the latter is caused by a steady increase in the strength of the prevailing westerly winds. The existence of such fluctuations and changes in the wave activity will affect long‐term predictions and are expected to have an important impact on the upper‐level physical, chemical, and biological processes of the ocean.
Response of the East Antarctica ice sheet to sea‐level rise
Authors: Alley Richard B. , Whillans Ian M.
Published: February 2008

A nonsteady ice‐flow model that explicitly includes longitudinal stresses is used to study the effects of marginal changes on the interior portions of an ice sheet. Sea‐level rise is found to cause a wave of thinning to propagate upglacier, and this wave is slowed, diffused, and damped. At the ice divide at dome C in central East Antarctica, post‐Wisconsinan sea‐level rise is modeled as having caused 110 m thinning, with response now 70% complete. If accumulation rates increased by 10% at the same time, then calculated net thinning has been only 75 m. Ice‐sheet response to changes in sea level and accumulation rate is relatively rapid; response to temperature changes is an order of magnitude slower. Response times are shorter if the marginal position of an ice sheet is controlled.
Observations of wind‐induced, subtidal variability in the Delaware estuary
Authors: Wong Kuo‐Chuin , Garvine Richard W.
Published: February 2008

Sea level and current observations made in the Delaware estuary during autumn of 1982 were examined for evidence of wind‐forced subtidal variability. The large subtidal sea level fluctuations at the mouth of the Delaware were found to be forced primarily by the wind stress component over the continental shelf nearly parallel to shore, indicating coastal Ekman transport to the right of the wind. Local wind forcing within the estuary is shown to be insignificant. The subtidal sea level in the interior of the estuary was found to be driven by the wind through a combination of two remote forcing mechanisms: one acting at the mouth of the Delaware through direct estuary‐shelf coupling and a second acting locally over the Chesapeake Bay and being transmitted from the upper Chesapeake through the Chesapeake and Delaware Canal, which links the two estuaries. In the upper Delaware estuary we found predominantly barotropic subtidal current fluctuations superimposed on a much weaker two‐layer gravitational circulation. These current fluctuations were produced primarily by the local subtidal surface slope generated by the difference between the two remote forcing mechanisms. The evidence strongly suggests that the Chesapeake and Delaware Canal plays a critical role in the subtidal circulation of the Delaware estuary.
The oceanic production of atmospheric sea salt
Authors: Blanchard Duncan C.
Published: February 2008

Over two decades ago, Eriksson calculated that 109 t (t = metric ton, or 103 kg) of atmospheric sea salt are produced by the oceans each year, but Blanchard argued that the rate was closer to 1010 t yr−1. It seems likely that Eriksson's value is too low because of errors introduced into the salt dry deposition calculations by using mean winds and neglecting the standard deviation, while Blanchard's value probably is too high because of wrong assumptions in calculating the salt wet deposition. Future work must make clear what altitude the salt is being cycled through.
On vertical motion, divergence, and the thermal wind balance in cold‐dome meanders: A diagnostic study
Authors: Chew Frank , Bane John M. , Brooks David A.
Published: February 2008

Wavelike meanders are observed along the length of the Florida Current from the Florida Keys to Cape Hatteras. These propagating meanders are three‐dimensional; each has a cold dome; and the meandering flow that overtakes the dome in a cyclonic turn is characteristically stronger when flowing offshore than when flowing onshore. We focus on vertical motion as a key to understanding the interdependence of the downstream propagation, the upwelling in the cold dome, and the skewness in the strength of the meandering flow. Inferred from a composite of drogue and temperature observations, the pattern of vertical motion is one of upwelling that extends throughout the water column formed by the forepart of the translating dome and its overlying on shore flow and a downwelling that similarly extends vertically through the rear part of the dome and its overlying offshore flow. It is shown that the vertical motion and the translation of the meander are interrelated, and both enter importantly in the acceleration of the water columns and hence in the skewness in the strength of the meandering flow component. As the thermal wind changes with the divergence accompanying the vertical motion, it also provides a twisting mechanism to help restore the thermal wind balance.
Structure and seasonal characteristics of the Gaspe Current
Authors: Benoit J. , El‐Sabh M. I. , Tang C. L.
Published: February 2008

CTD and current meter data from the northwestern Gulf of St. Lawrence were analyzed to study the structure and variability of the Gaspé Current. Since the current is buoyancy driven, its properties are strongly influenced by the seasonal variation of the freshwater discharge from the St. Lawrence estuary. From June to November, maximum speed decreases from 110 cm s−1 to 60 cm s−1. High vertical shears exist in the upper 40 m of the water column. During the same period, the width of the current decreases, and the position of the current maximum shifts from near the shore to about 14 km from the shore. These changes in the structure can be understood in terms of geostrophy and baroclinic deformation radius. In the temperature/salinity field the most prominent change from June to November is the continuing increase of surface salinity. Temperature change occurs mainly in the September‐November period, when atmospheric cooling accelerates. The effect of atmospheric cooling is also reflected in the density distribution, with the result that in November currents in the upper 30 m are seaward in the entire section (from Sept‐Iles to Marthe de Gaspé), while in the summer months the currents are seaward in the southern part and westward in the northern part of the section. Momentum balance of the current system is also investigated. It was found that east of Pointe‐des‐Monts, geostrophic balance is maintained, while west of Pointe‐des‐Monts the observations do not seem to be consistent with the assumption of geostrophy.
Estimates of oceanic horizontal heat transport in the tropical Pacific
Authors: Pares‐Sierra Alejandro F. , Inoue Masamichi , O'Brien James J.
Published: February 2008

Meridional heat transport in the tropical Pacific is estimated using a linear numerical model with realistic boundaries and forced by 18 years of observed wind, covering the period from January 1962 to December 1979. The long‐term mean heat transport estimated in this study is similar to the estimates based on heat balance and radiation considerations and on complex numerical models that account for thermodynamics as well. This points to the dominant role played by the adiabatic process, the only heat transport mechanism present in this study, in the heat balance for the equatorial Pacific. The combined Ekman and geostrophic heat transport can account for the net meridional heat transport, except near the equator, where continuity requirements dictate. The Ekman and geostrophic transport oppose each other, and their small difference in magnitude gives rise to the net meridional heat transport, resulting in transport away from the equator for the southern hemisphere and north of 6°N, while for the band between 6°N and the equator an equatorward transport is present. Seasonal and interannual variations are found to be as large as, or even larger than, the long‐term mean. Seasonal variations in meridional heat transport are in accordance with seasonal variations in zonal winds via Ekman transport, while the geostrophic transport remains more or less constant on this time scale. The results are a net poleward heat transport in the winter hemisphere and a equatorward transport in the summer hemisphere. At the interannual time scale, variabilities in both Ekman and geostrophic components contribute to the interannual variability in heat transport. Major features of the interannual variations in meridional heat transport appear to be associated with the El Nino events. It is interesting to note that the interannual variations associated with El Nino events are not restricted to the near‐equatorial region. Phase locking between the interannual variations and the annual cycle is evident in the data set. Major findings in this study, based on an adiabatic model, are expected to carry over to more realistic nonlinear numerical models.