bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurements of deep currents in the central North Pacific
Authors: Taft B. A. , Ramp S. R. , Dworski J. G. , Holloway G.
Published: February 2008

Two deep arrays of current meters at heights of 1200 and 100 m above the bottom were set under the North Pacific Subtropical Gyre near 30°30'N, 157°45'W; the maximum record length obtained was 19 months. Autospectra show the following characteristics: strong peaks at the M2, S2 tidal frequencies; a broad peak at the diurnal‐inertial peak; a spectral gap centered at 0.02 c h−1; and a regular increase in energy with decreasing frequency below the gap. Rotary components tend to be counterclockwise below 10−2 c h−1 and clockwise above the diurnal‐inertial frequency. The M2 tidal amplitude ranged between 1.0 and 1.6 cm s−1; phase relationships suggest that a significant part of the motion is due to internal wave motion at this frequency. Low‐pass filtered velocity statistics show the following: evidence of nonstationarity in the variances between the first (9 month) and second (10 month) arrays; significant horizontal variation of mean kinetic energy on scales of 100 km; and time‐space averaged eddy kinetic energy is comparable in magnitude to the lowest values measured under the Subtropical Gyre in the western North Atlantic. Currents at 1200 m tended to be greater than at 100 m above the bottom. Spectra of the 100‐m records indicate the presence of two peaks at low frequency: a dominant and ubiquitous peak in the 1/105–1/175 c d−l frequency band; and a secondary peak, which is shown in three of four moorings, in the 1/58–1/75 c d−1 frequency band. Point estimates of the periods of the peaks give average values of 154 and 67 days. Comparison with subtropical western North Atlantic spectra shows that the ‘temporal mesoscale’ period (∼150 d) is somewhat higher in the Pacific data and it does not show the dominance of meridional motions observed in the Atlantic spectra. Plane wave fits to the 154‐day oscillation show the longest wave which closely fits the data has a wave length of 170 km and propagates toward 197°T. The westward phase propagation and particle orbits, which are transverse to the direction of propagation, are consistent with planetary Rossby wave dynamics. This wave does not fit the dispersion relation for flat‐bottom planetary waves; the observed phase speed is greater than that predicted by the dispersion relation. It is shown that either Doppler shifting of the frequency by the mean flow or topographic effects might account for the discrepancy.
An energetics bedload model for a plane sloping beach: Local transport
Authors: Bailard James A. , Inman Douglas L.
Published: February 2008

Bagnold's energetics‐based sediment transport model for streams is used as a basis for the development of a model for the time‐varying transport of bedload over a plane sloping bed. The sediment transport vector is found to consist of two components: the velocity‐induced transport, directed parallel to the instantaneous velocity vector, and the gravity‐induced transport vector, directed downslope. The model is applied to the case of sediment transport within the surf zone for the separate cases of weak and strong longshore currents, relative to the wave (bore) oscillatory water velocity. The results suggest that Bagnold's oscillatory sediment transport model, which forms the basis for a number of longshore sediment transport models, is only correct for the special case of weak longshore currents and near‐normal incident waves. For an arbitrary strength longshore current v and a local incident wave angle α, the longshore transport rate is found to be proportional to 〈ũ3〉 sin α + 〈ũ2〉v(1 + sin2 α) + v3, where ũ; is the wave‐induced oscillatory water velocity. The model also predicts the onshore‐offshore sediment rate, 〈ix〉. For weak longshore currents and near‐normal incident waves, the predicted equilibrium beach slope is equal to tanϕ〈ũ3〉/〈|ũ;|3〉. Strong longshore currents and or significant local wave angle conditions, however, cause a change in this equilibrium beach slope.
Photochemical processes induced by a major warming of the upper atmosphere: Variations in mesospheric trace constituents
Authors: Frederick John E.
Published: February 2008

The temperature rise and enhanced winds during an upper atmospheric warming cause substantial changes in the high level ozone profile of the sunlit winter hemisphere. Calculations based on a photochemical model, using temperatures measured at Fort Churchill during a major warming, predict a factor of 2 variation in the ozone number density near 60 km over a time period of approximately 3 weeks. This temporal variability at a fixed location results from the planetary wave structure of the temperature field and reflects a similar longitudinal behavior at a given time. The ozone number density at fixed altitude is a maximum when the temperature is greatest at and below this level. This is due primarily to thermal expansion of the atmosphere which results in a large increase in pressure at constant altitude. However, chemical activity during a warming decreases the mesospheric ozone mixing ratio at fixed pressure. The ozone mixing ratio at constant pressure during the peak of the event studied is near 75% of its unperturbed value. The predicted variability of ozone in longitude and time demonstrates the need for hemispheric scale information on trace gas abundances, temperature, and winds in order to delineate adequately the response of upper atmospheric composition to a major perturbation.
Tropospheric profiles of NOx
Authors: Kley D. , Drummond J. W. , McFarland M. , Liu S. C.
Published: February 2008

Profiles of the mixing ratio of NOx (NOx = NO + NO2) for the clean troposphere are presented. The NOx mixing ratio increases from 10 pptv in surface air to values of about 200 pptv at the tropopause. The profile of NOx is governed by intrusion of odd nitrogen from the stratosphere into the troposphere. Anthropogenically produced NOx from ground level sources influences the NOx profile only in the lower troposphere.
Seasonality of Southern Ocean sea ice
Authors: Gordon Arnold L.
Published: February 2008

The sea ice cover of the Southern Ocean undergoes a rapid decrease from mid‐November to mid‐January. The atmosphere‐to‐ocean heat flux is insufficient to account for this melting, even in the presence of the high percentage of open water characteristic of the Southern Ocean sea ice. It is estimated that sea‐air heat exchange in the 60° to 70°S zone can account for roughly 50% of the required spring heating. The remainder must be supplied by the relatively warm deep water, residing below the Southern Ocean pycnocline. Deep‐to‐surface water heat flux is accomplished by upwelling of the pycnocline due to the regional Ekman divergence of the surface layer and by cross‐pycnocline mixing. It is estimated that the required vertical mixing coefficient for the pycnocline is 1.5 cm2/s. This value is considered as realistic in view of the relatively weak pycnocline which is a consequence of low levels of fresh water input to the surface layer. It is suggested that the magnitude of fresh water input is a major factor in determining the degree of seasonality of Southern Ocean sea ice.
Springtime evolution of the New England shelf break front
Authors: Posmentier Eric S. , Houghton Robert W.
Published: February 2008

The shelf break frontal shape and T‐S relationships in the frontal vicinity have been observed to undergo a transition in the spring. It is shown that this transition should result from two simple assumptions: (1) during the early spring, the offshore density gradient becomes reversed in a layer of intermediate depth; and (2) the front is gravitationally stable. Observations south of Nantucket preceding and following the transition during 1979 illustrate the metamorphosis from a monotonically sloping front to a convoluted shape which delineates two layers of shelf water and two of slope water. The convoluted shape of both the front and the T‐S curves after the transition are found to be consistent with the observed density gradients if it is further assumed that the front is Margules‐type with a velocity discontinuity of 5 cm/s.
The vertical distribution of stable trace gases at mid‐latitudes
Authors: Fabian P. , Borchers R. , Flentje G. , Matthews W. A. , Seiler W. , Giehl H. , Bunse K. , Müller F. , Schmidt U. , Volz A. , Khedim A. , Johnen F. J.
Published: February 2008

Vertical profiles of H2, CH4, CO, N2O, CFCl3, and CF2Cl2 resulting from gas chromatographic analysis of air samples collected from altitudes between 1.5 and 35.3 km at a latitude of about 44°N are presented. Ten balloon flights were performed with a neon‐cooled cryogenic air sampler designed to collect large air samples at eight different stratospheric heights. Supplementary tropospheric air samples were taken aboard a chartered aircraft. Vertical profiles from 1978 and 1979 are compared with those derived from fights in 1977.
On the detectability of ocean surface waves by real and synthetic aperture radar
Authors: Alpers Werner R. , Ross Duncan B. , Rufenach Clifford L.
Published: February 2008

Real and synthetic aperture radars have been used in recent years to image ocean surface waves. Though wavelike patterns are often discernible on radar images, it is still not fully understood how they relate to the actual wave field. The present paper reviews and extends current models on the imaging mechanism. Linear transfer functions that relate the two‐dimensional wave field to the real aperture radar (SLAR) image are calculated by using the two‐scale wave model. It is noted that a description of the imaging process by these transfer functions can only be adequate for low to moderate sea states. Possible other mechanisms that contribute to the visibility of waves by real aperture radar at higher sea states, such as Bragg scattering from spontaneously generated short waves at peaked crests or in wave breaking regions, and Rayleigh scattering from air bubbles entrained in the water and from water droplets thrown into the air by breaking waves, are discussed in a qualitative way. The imaging mechanism for synthetic aperture radars (SAR's) is strongly influenced by wave motions (i.e., by the orbital velocity and acceleration associated with the long waves). The phase velocity of the long waves does not enter into the imaging process. Focusing of ocean wave imagery is attributed to orbital acceleration effects. The orbital motions lead to a degradation in resolution which causes image smear as well as a SAR inherent imaging mechanism called velocity bunching. The parameter range for which velocity bunching is a linear mapping process is calculated. It is shown that linearity holds only for a relative small range of ocean wave parameters: The likelihood that the transfer function is linear increases as the direction of wave propagation approaches the range direction, as the wavelength increases, and as the wave height decreases. Linearity is required for applying simple linear system theory for calculating the ocean wave spectrum from the gray level intensity spectrum of the image. Although, in general, the full ocean wave spectrum cannot be recovered from the SAR image by applying simple linear inversion techniques, it is concluded that for many cases in which the ocean wave spectrum is relatively narrow the dominant wavelength and direction can still be retrieved from the image even when the mapping transfer function is nonlinear. Finally, we compare our theoretical models for the imaging mechanisms with existing SLAR and SAR imagery of ocean waves and conclude that our theoretical models are in agreement with experimental data. In particular, our theory predicts that swell traveling in flight (azimuthal) direction is not detectable by SLAR but is detectable by SAR.
Low‐frequency temperature fluctuations off Bermuda
Authors: Frankignoul Claude
Published: February 2008

Twenty‐four years of hydrographic stations made by the R. V. Panulirus southeast of Bermuda at approximately semi‐monthly intervals have been used to construct temperature time series at 10 depths ranging from the surface to 2000 m. The data contain no significant seasonal signal at depth ≥250 m. Subsurface temperature spectra have a broad peak in the eddy containing band at periods ∼0 (100 days) and drop rapidly at high frequencies. At very low frequencies, the spectra indicate some redness, down to the largest resolvable time scales. Most of the energy in the temperature fluctuations is concentrated into two vertical modes, which resemble the first two baroclinic normal modes, and explain 60% and 23% of the variance, respectively. The observed spectrum of sea surface temperature (SST) anomalies has substantially more variance at periods of a year and less than SST anomaly spectra estimated from ship reports on 5 × 5° grid. It is suggested that the excess variance is due to the advection of the sea surface temperature pattern by the underlying field of smaller scale eddies, consistently with the observed coherences between surface and deeper temperature records.
The central Pacific near‐equatorial convergence zone
Authors: Ramage C. S. , Khalsa S. J. S. , Meisner B. N.
Published: February 2008

The central Pacific near‐equatorial convergence zone (CZ) lies north of the equator throughout the year. On an average it moves between 4°N in spring and 8°N in autumn, probably in response to annual variation in the strengths of the northeast and southeast trade winds. For 6 weeks in the period November 1977 to January 1978 a NOAA P‐3 research aircraft flew between Hawaii and Tahiti, southward along 150°W and northward along 158°W, at a frequency of one round trip per week. During this time the CZ lay near its climatological latitude. Late season North Pacific and early season South Pacific tropical cyclones caused the CZ to be more variable than usual, especially along 158°W. The aircraft flew at an altitude of 250 m between 11°N and 0.5°S, and the data from these segments of the flights have made possible an examination of the CZ in unprecedented detail. High resolution satellite images, high and low cloud movement vectors, soundings from several island stations, and soundings made by the aircraft while it descended to and ascended from the low‐level segments were all used to determine the large‐ and small‐scale influences on the CZ at the time of each traverse. From the aircraft data time series of selected variables and time‐latitude sections showing variables averaged over 1/4° latitude were plotted. The types of CZ's encountered had several common features and yet were remarkably diverse. Ten s averages revealed that the CZ was almost always clearly delineated by abrupt changes in temperature and humidity. In many cases, convergence and rainfall were greatest at these boundaries while divergence was large somewhere between. Narrow zones with low moist static energy were frequently encountered within the CZ, indicating that a midtropospheric dry layer and compensating sinking existed within the CZ, a region which had been commonly thought to be merely a funnel for moist surface air to be moved to the upper troposphere where the energy of condensation is exported to higher latitudes. Measurements from the gust probe showed that turbulent fluxes of sensible and latent heat were not necessarily greatest in the CZ, implying that the associated sea surface temperature maximum did not regulate the position or intensity of the convergence zone. There are indications that the upper troposphere played an important role. Soundings showed that the trade wind inversion extended to the latitude of the CZ without significant change in height along the trade wind trajectory. The inversion may even extend across the CZ and thus inhibit deep convection. At least in the central Pacific it appears that the CZ may make only a small contribution to the Hadley cell and have little effect on mid‐latitude circulations.
Stress amplification under a moving load on floating ice
Authors: Bates Howard F. , Shapiro Lewis H.
Published: February 2008

The plane‐wave solution found in earlier work for the response of a viscoelastic floating plate to a moving line load is evaluated for a variety of conditions that might occur for floating ice sheets. The equivalent wave loading stress produced in a thin ice sheet by a line load moving at the critical speed is found to exceed the applied static loading stress by a substantial factor. As the ice thickness or the modulus increases, or the water depth decreases, the maximum loading factor decreases. The response of a floating ice sheet to a moving vehicle is discussed in the light of this behavior. The results suggest that ice less than 0.25 m thick might be efficiently broken by several relatively light ice breakers, such as air cushion vehicles, operating in a line abreast at the critical speed.
Swash oscillations on a natural beach
Authors: Guza R. T. , Thornton Edward B.
Published: February 2008

Run‐up (swash) oscillations were measured on a gently sloping beach face for a variety of incident wave conditions. Run‐up energy spectra at wind wave frequencies show an ƒ−3dependence and energy levels that are independent of incident wave height. This suggests saturation. In contrast, run‐up energy at surf beat periods increase approximately linearly with increasing incident wave energy. Thus, in the inner surf zone, where wave breaking limits the energy at wind wave frequencies, the principal manifestation of large incident wind waves is energetic surf beat.
The electrical structure of the hokuriku winter thunderstorms
Authors: Brook Marx , Nakano Minoru , Krehbiel Paul , Takeuti Toshio
Published: February 2008

Lightning charges, locations, and currents have been determined for 12 flashes from four winter storms observed on the Hokuriku coast of Japan during December 1977 through January 1978. Additional data is available from a total of eight winter storms. The heights and magnitudes of the charges in strokes‐to‐ground were calculated from simultaneous measurements of electric field changes made at seven stations covering an area of about 150 km2. Discharges lowering positive charge to earth often exhibit large continuing currents (>104 A) for periods up to 10 ms. One positive discharge involved a peak current value of ≃105 A and a charge that exceeded 300°C after 4 ms. Negative continuing current strokes are generally an order of magnitude smaller, ≃4×103 A, involving charges of 100°C or less. The positive lightning charges are located higher than the negative charges of the same storm, constituting a ‘normal’ bipolar system similar to the charge configuration found in summer thunderstorms. For the eight storms observed during this study, 26 out of a total of 63 strokes‐to‐ground were positive. A strong correlation exists between the fraction of positive ground strokes and the vertical wind shear in the cloud layer. On the basis of this study we suggest that the occurrence of positive strokes‐to‐ground is a consequence of the wind shear. The shear provides a horizontal displacement between the charges that helps to ensure that an initiating positive streamer will continue down to ground rather than into the negatively charged region that would normally be located directly below it. The data suggest that positive strokes‐to‐ground should appear at a threshold shear value in the cloud layer of about 1.5 m/s/km.
A model study of Fuego volcanic aerosol dispersion in the lower stratosphere
Authors: Remsberg E. E. , Turner R. E. , Butler C. F.
Published: February 2008

A zonally averaged time dependent primitive equation model has been used to simulate the dispersion of both a carbon 14 injection and the volcanic aerosol from the 1974 Fuego eruption. Both injections occurred at low latitudes to mid‐latitudes in the northern hemisphere. The eddy flux terms, which provide the major portion of the transport in the lower stratosphere of this model, are specified in a manner similar to Harwood and Pyle. Comparisons with data emphasize the ability of the model to simulate the vertical character of the tracer, while maintaining reasonable meridional transport times. For the aerosol study, the simulated 1/e decay time at 37°N and for the 16‐to 21‐km altitude region is 9 months, whereas lidar measurements at the same latitude yield a decay time of 8 months. The simulated vertical width at half‐maximum for the aerosol tracer at 37°N and 19°N and for 6 months after the event has values of 5.0 km and 3.6 km, respectively, whereas the observed lidar values were 4.4 km and 3.0 km, respectively. Tracer transport to the southern hemisphere also agrees qualitatively with the limited data that are available. Comparisons of our model results with those published using other zonally averaged models indicate that there are major differences in the transport in parameterized zonally averaged models. For the present model, inclusion of a realistic aerosol sedimentation rate moves the vertical position of the model layer peak onto the observed one. The close agreement between data and our model results show that one does not have to invoke aerosol chemical growth processes in order to model the dispersion of this aerosol tracer from 2 months to 1 year after the event.
Observations on tides in the equatorial mesosphere
Authors: Countryman I. D. , Dolas P. M.
Published: February 2008

Backscatter observations of the mesosphere (62–86 km), using the 50 MHz coherent scatter radar at Jicamarca, Peru (12°S, 77°W), are analyzed to obtain tidal and prevailing wind components. The observation periods are four 48‐hour intervals covering December 20–22, 1976, and April 11–13, July 15–17, and October 3–5, 1977. The effects of missing nighttime data on the 12‐ and 24‐hour estimates are taken into account. The diurnal and semidiurnal tidal components appear to show an evanescent mode or higher order propagating modes superimposed on the main diurnal (1,1) mode and the main semidiurnal (2,2) mode, respectively. There are a few indications of complete phase reversal from one height to the next, indicating the presence of standing wave patterns. The diurnal tide amplitudes never realize the amplitude growth with height predicted by theory partly due to interference effects and other loss processes at work in the upper mesosphere.
SEASAT wind and wave observations of northeast Pacific hurricane Iva, August 13, 1978
Authors: Gonzalez F. I. , Thompson T. W. , Brown W. E. , Weissman D. E.
Published: February 2008

SEASAT wind and wave observations collected in the eye of hurricane Iva on August 13, 1978, in the northeast Pacific are examined. The SEASAT‐A scatterometer system (SASS) and scanning multichannel microwave radiometer (SMMR) observations indicate a maximum wind speed of 25–30 m/s. SASS‐derived isotachs indicate a classic banana‐shaped high‐wind‐speed distribution, and the synthetic aperture radar (SAR) imagery displays a large‐scale mean intensity pattern that is in qualitative agreement. Two‐dimensional Fourier transforms of selected SAR scenes show a dominant wave field characterized by wavelengths of 166–211 m, with a fanlike distribution of propagation directions. A simple geometric model is proposed as an explanation of this dominant wave field in terms of prior storm intensity and location. This geometric model, the Ross parametric hurricane wave model, and the SEASAT wind and wave data are then employed to obtain estimates of 43 km for the radius to maximum winds and 6.4 m for the corresponding significant wave height at that radius.
Seabed wave boundary layer measurements and analysis
Authors: Lambrakos K. F.
Published: February 2008

Velocity measurements made at two elevations off a rough sea floor in 18.3 m of water depth in the Strait of Juan de Fuca suggest the presence of a wave boundary layer. The wave velocities measured at 0.69 m off bottom are, overall, larger in magnitude and also shifted in time relative to the velocities measured at 1.85 m. These data were fitted to a two‐parameter damped oscillator velocity model which was then used to obtain results on boundary layer thickness, bottom shear, and friction coefficient. The calculated boundary layer quantities are consistent with those from laboratory data and correspond to rougher flow conditions than those that have been observed in the laboratory. The damped oscillator model implies semiempirical relationships between the boundary layer quantities and the free, stream velocity and period through an apparent bottom roughness parameter.
Observation of the diurnal variation of atmospheric ozone
Authors: Lean J. L.
Published: February 2008

Ozone densities in the stratosphere and mesosphere have been derived from broad‐band photometer measurements of Hartley band absorption of middle ultraviolet radiation. Seven rockets were launched during October–November 1979 from Wallops Island. Six rockets, each carrying one detector comprising two UV photometers, were launched at different times of the day. A seventh rocket, with three similar detectors each having three UV photometers, was launched at the time of a full moon and provided estimates of the nighttime ozone densities. Results from these rocket flights form a basis for investigating ozone diurnal variations. The number of flights provide greater statistical reliability for the ozone profiles than is generally afforded from in situ measurements with a single rocket. During the night, an enhancement in ozone densities occurred at altitudes above about 50 km. At 70 km, for example, the nighttime ozone was determined to be a factor of 6.4 greater than at sunset. In addition, these experiments suggest that near 40 km the magnitude of the ozone density at noon may be greater by 10–15% than the nighttime concentration.
A thundercloud electric field sounding: Charge distribution and lightning
Authors: Weber M. E. , Christian H. J. , Few A. A. , Stewart M. F.
Published: February 2008

An instrumented free balloon measured electric fields and field changes as it rose through a thundercloud above Langmuir Laboratory, New Mexico. The variation of the electric field with altitude implied that the cloud contained negative space charge of density −0.6 to −4 nC m−3 between 5.5 and 8.0 km MSL. The environmental temperature at these levels ranged from −5° to −20°C. Our measurements imply that the areal extent of this negative charge center was significantly greater than that of the cloud's intense precipitation shafts. At altitudes greater than 8 km, the instrument ascended past net positive charge. We also inferred from our measurements positive space charge adjacent to the earth's surface (concentration 0.6 nC m−3) and in the lowest portion of the cloud (1.0 nC m−3). Electric field changes from intracloud lightning were interpreted by using a simple model for the developing streamer of the initial phase. Thunder source reconstructions provided estimates for the orientation of lightning channels. Seven ‘streamers’ so analyzed propagated on the average, at 5×104 m s−1 and carried a current of 390 A. The mean charge dissipated during a flash was 30 C.
Doppler radar echoes of lightning and precipitation at vertical incidence
Authors: Zrnić Dusan S. , Rust W. David , Taylor William L.
Published: February 2008

Digital time series data at 16 heights within two storms were collected at vertical incidence with a 10‐cm Doppler radar. On several occasions during data collection, lightning echoes were observed as increased reflectivity on an oscilloscope display. Simultaneously, lightning signals from nearby electric field change antennas were recorded on an analog recorder together with the radar echoes. Reflectivity, mean velocity, and Doppler spectra were examined by means of time series analysis for times during and after lightning discharges. Spectra from locations where lightning occurred show peaks due to the motion of the lightning channel at the air speed. These peaks are considerably narrower than the ones due to precipitation. Besides indicating the vertical air velocity that can then be used to estimate hydrometeor‐size distribution, the lightning spectra provide a convenient means to estimate the radar cross section of the channel. Subsequent to one discharge, we deduce that a rapid change in the orientation of hydrometeors occurrred within the resolution volume.
A rocket‐borne photometric measurement of O3 and NO2 in the equatorial stratosphere
Authors: Schlyter Paul , Witt Georg
Published: February 2008

A determination of the NO2 and O3 mixing ratios has been made by measuring the attenuation of sunlight at 409 nm and 254, 288, 316 nm from an ascending rocket launched from Kourou, French Guiana (5°N) during the morning twilight of March 21, 1974. A peak NO2 volume mixing ratio of 4.4. x
was measured at 30 km altitude.
Air‐sea exchange of CO2 and evidence for enhanced upward fluxes
Authors: Wesely M. L. , Cook D. R. , Hart R. L. , Williams R. M.
Published: February 2008

The flux of carbon dioxide has been measured by eddy correlation techniques over shallow coastal waters at an outer submerged reef near Miami, Florida, during two weeks in March when the sea water was gradually warming. Large upward fluxes were detected, much larger than expected, and they were nearly linearly proportional to friction velocity u* for the wind speeds of 3–10 m s−1 encountered. In 10 m s−1 winds, the flux was 0.30–0.35 mg m−2 s−1 and the aqueous transfer velocity across the interfacial sublayer was about 0.20 cm s−1. The measured eddy fluxes of submicron particles were also directed upward and displayed a strong, nearly linear dependence on u* similar to the case for CO2. Bubbles could be a source of increased CO2 transport and of particle production by film drops associated with bursting at the surface, but the number of bubbles required seems to be too large when comparisons are made with current knowledge of bubbles produced by breaking waves.
Exchange of H2S between air and water
Authors: Spedding John , Vujcich Mary
Published: February 2008

The overall exchange coefficient expressed on a gas phase basis, Kg, for the transfer of H2S from water to air was measured in the laboratory by using radioactive H2S. The exchange coefficient showed a strong dependence on solution pH that was found to be related to enhancement by ionisation of H2S to HS−. At low pH values, where this enhancement had no effect, the value of Kg was 2.3×10−2 cm s−1. At sea water pH, Kg increased to 0.13 cm s−1 leading to the conclusion that at pH<5 liquid phase resistance dominates the exchange while with increasing pH gas phase resistance becomes increasingly important.
A study of atmospheric diffusion from the LANDSAT imagery
Authors: Viswanadham Y. , Torsani J. A.
Published: February 2008

Detailed analyses of the LANDSAT multispectral scanner (MSS) data of the smoke plumes that originated in eastern Cabo Frio (22° 59′S; 42° 02′W) and crossed over into the Atlantic ocean are presented to illustrate how high‐resolution LANDSAT imagery can aid meteorologists in evaluating specific air pollution events. The eleven LANDSAT images selected are for different months and years. Conventional interpretation techniques are applied to analyze the images with a view to arrive at certain plume characteristics. The analysis of the visible smoke plumes revealed that the plume was 130 km long and attained a maximum width of 937 m, 10 km away from the chimney emitting the effluent. The results show that diffusion is governed primarily by water and air temperature differences. With colder water, low‐level air is very stable and the vertical diffusion is minimal; but water warmer than the air induces vigorous diffusion. The applicability of two empirical methods for determining the horizontal eddy diffusivity coefficient (Ky) in the Gaussian plume formula was evaluated with the estimated standard deviation of the crosswind distribution of material in the plume (σy) from the LANDSAT imagery. Most consistent estimates for Ky are obtained from the formula based on Taylor's theory of ‘diffusion by continuous moment’. Ky values of about 158 m2 s−1 in quasi‐neutral conditions and 49 m2 s−1 in stable conditions are obtained from a plot of σ2y as a function of distance from the source. The rate of kinetic energy dissipation (ε) is evaluated from the diffusion parameters σy and Ky. The ε value ranges from 0.1×10−5 m2 s−3 to 80.2×10−5 m2 s−3 in quasi‐neutral and stable stratifications. These results compare well with the previous experimental values obtained over water surfaces by various workers. They form a data base for use in the development and validation of mesoscale atmospheric diffusion models.
The influence of large‐scale advection on the vertical distribution of stratospheric source gases in 44° and 41° North
Authors: Schmidt Manfred
Published: February 2008

Correlations between deviations from mean profiles of CH4 and N2O vertical distribution in the stratosphere and air mass trajectories in the 100 mbar and 30 mbar level are discussed. The profiles were taken from results of 11 balloon flights over France and 3 flights over Laramie/Wyoming during 1976–1980. The deviations in the profiles appear to depend on the origin of the air masses. Compared with the results from the lower stratosphere, the conditions in the middle stratosphere between 20 and 36 km height are more complex and seasonally dependent. Some possible explanations with respect to the general circulation in the stratosphere and troposphere are given.
Interpretation of atmospheric CO2 measurements at Mt. Cimone (Italy) related to wind data
Authors: Ciattaglia Luigi
Published: February 2008

Technical details on the apparatus and the CO2 program at Mt. Cimone are reported, together with information on the sampling site and on the wind regime. Hourly values of atmospheric CO2 are examined, and a preliminary interpretation is given, taking into account simultaneous observations of wind direction and wind speed at Mt. Cimone. In particular, a seasonal CO2 trend is clearly identified along with a CO2 dependence on synoptic situations, especially wind speed and direction.
Observations of eddy fields in the northwest Atlantic and northwest Pacific by SEASAT altimeter data
Authors: Menard Yves
Published: February 2008

Sea level variability, related to the eddy field activity, can be calculated from repeating tracks of altimetric data, such as the SEASAT 3‐day repeat data (September 13 to October 10, 1978). If we consider the eddy field in geostrophic balance, the geostrophic relation gives the surface eddy velocities. Also, an estimation of the eddy kinetic energy can be deduced under the assumption of quasi‐isotropy of the velocity variability. This approach is used in the northwest Atlantic and northwest Pacific through the processing of SEASAT data. High variability of sea surface topography (up to 20 cm) and high eddy kinetic energy (800–1600 cm2/s2) are detected in the vicinity of the Gulf Stream and the Kuroshio. Power spectra of the observed sea level fluctuations give wavelengths ranging from 100 to 900 km for time scales between 3 and 25 days. Maps of sea surface topography variability and eddy kinetic energy are presented and discussed.
SEASAT synthetic aperture radar (SAR) response to lowland vegetation types in eastern Maryland and Virginia
Authors: Krohn M. Dennis , Milton N. M. , Segal Donald B.
Published: February 2008

Examination of SEASAT SAR images of eastern Maryland and Virginia reveals botanical distinctions between vegetated lowland areas and adjacent upland areas. Radar returns from the lowland areas can be either brighter or darker than returns from the upland forests. Scattering models and scatterometer measurements predict an increase of 6 dB in backscatter from vegetation over standing water. This agrees with the SCWigital number (DN) increase observed in the digital SEASAT data. The brightest areas in the Chickahominy, Virginia, drainage, containing P. virginica about 0.4 m high, contrast with the brightest areas in the Blackwater, Maryland, marshes, which contain mature loblolly pine in standing water. The darkest vegetated area in the Chickahominy drainage contains a forest of Nyssa aquatica (water tupelo) about 18 m high, while the darkest vegetated area in the Blackwater marshes contains the marsh plant Spartina alterniflora, 0.3 m high. The density, morphology, and relative geometry of the lowland vegetation with respect to standing water can all affect the strength of the return L band signal.
SEASAT‐derived ocean surface topography: Comparison with coincident Kuroshio hydrographic data
Authors: Byrne H. Michael , Pullen Patricia E.
Published: February 2008

During the SEASAT repeat‐orbit period, a CTD and deep (1800 m) XBT hydrographic experiment was conducted across the Kuroshio to obtain cotemporaneous surface topography measurements for comparison with the altimeter‐derived surface height measurements. The results showed that the altimeter could detect and measure the change in sea surface topography caused by movement of the Kuroshio and the cold rings that were found in the hydrographic data. After compensation for the small differences in the time of the measurements, the altimeter measured changes in the surface topography that matched those measured by the hydrographic sections with an average difference of 9.6 cm for the 41 comparison points.
Selected man‐made halogenated chemicals in the air and oceanic environment
Authors: Singh Hanwant B. , Salas Louis J. , Stiles Robin E.
Published: February 2008

Latitudinal distribution (40°N to 32°S) of a number of synthetic haiogenated species show that for unreactive species (i.e., fluorocarbon 12(F 12), F 11, F 113, F 114, F 13B1, SF6 and CCl4) the northern hemispheric (NH) burden is only 5 to 10% higher than the southern hemispheric (SH) value. The mean NH/SH concentration ratios for 1,1,1‐trichloroethane; dichloromethane; chloroform; 1,2 dichloroethane; and tetrachloroethene are found to be 1.34, 1.80, 1.90, 2.64, and 5.80, respectively. When compared with available emissions data, the atmospheric budget of these species are compatible with atmospheric residence times (years) of 100(+ 100/ ‐40), 60(+ 40/ ‐ 20), 9(+ 2/ ‐ 1), 0.9(±0.3), 0.6(±0.2), and 0.6(±0.2) for F 12; F 11; 1,1,1‐tricholoroethane; dichloromethane; 1,2‐dichloroethane; and tetrachloroethene, respectively. A ‘mean hydroxyl radical’ concentration of 4–6×105 mol cm−3 and an average interhemispheric exchange rate of 1.2 years best fit the observational data. Based on measurements conducted at 39°N during the period of November 1979 to December 1981, mean atmospheric growth rates of 26(±5), 15(±3), 13(±3), and 6(±3) ppt/yr, are found for F 12; F 11, 1,1,1‐trichloroethane; and carbon tetrachloride, respectively. The F 12 and F 11 measured growth rates are larger than those predicted from emissions data. Oceanic surface water measurements in the Eastern Pacific show that F 12, F 11, and F 113 concentrations are in rough equilibrium with air concentrations, carbon tetrachloride is significantly undersaturated (∼25%), and chloroform, dichloromethane, trichloroethene and tetrachloroethene are oversaturated.
The contribution of volcanoes to the global atmospheric sulfur budget
Authors: Berresheim H. , Jaeschke W.
Published: February 2008

A new assessment of the global volcanic emission rates of H2S, SO2, and SO42− is presented. The assessment is based on the development of a suitable classification of volcanic activity and its application to own measurements and measuring data given in the literature. Using this classification, the volcanic sulfur release is estimated to 1.18×107 t S/a total. This estimate must be regarded as a minimum since the data available for major explosive events are very uncertain. On the other hand the frequency of such events is comparatively low. We estimate a global volcanic emission of 1.52× 07 t SO2/a for the period 1961–1979. Our calculations show that in this period the total SO2 release during eruptive activities was at least 1.0×106 t SO2/a whereas about 14 times as much, namely 1.42×107 t SO2/a, were emitted during noneruptive activities. The importance of the contribution of the noneruptive activity has been neglected in earlier assessments. The average values for the global volcanic H2S and SO42− source strength are found to be around 106 t/a and 107 t/a, respectively. We conclude that during a period of very intensive volcanic activity around the world, like that which recently has started with the eruptions of Soufrière in 1979 and Mount St. Helens in 1980, the global sulfur release during eruptive events may become up to 1 order of magnitude higher than we have calculated but that nevertheless the sulfur emission during the noneruptive activity is dominating.
Imaging radar observations of directional properties of ocean waves
Authors: McLeish William , Ross Duncan B.
Published: February 2008

SEASAT‐A synthetic aperture radar (SAR) and side‐looking airborne radar (SLAR) images of ocean waves are examined in the form of normalized directional distributions of backscatter variance at series of frequencies. This method provides a more detailed description of radar results than have contoured two‐dimensional wave number spectra and reduces some of the uncertainties in relating radar measurements to the waves. The range of aspects of the radar distribution that parallel those of ocean waves is defined. Within this restriction, not only can dominant wave frequencies and directions be determined accurately, but also the shape of a directional peak at a frequency, its directional width, and the background level can be determined approximately. Some of these aspects are examined with SLAR images obtained near reference wave measurements. Through its superior directional resolution, the radar appears to have distinguished two wave trains at a single frequency only 20° different in direction. The SEASAT‐A satellite SAR provided an unusual opportunity to examine directional properties of waves in the hostile environment about Hurricane Fico. A swell highly dispersed in frequency and direction at a distance from the center of 450 km had a minimum observed directional width of 11°. Wave directions, their changes with frequency, and directional widths were in accord with those expected from the hurricane winds. Thematic maps of the direction and width of the swell energy as it spread across the ocean surface show smooth changes in these properties over distance, with relatively small scatter of individual values. These patterns also are in accord with those from a simple hurricane wave emission concept, but details of the distributions show distinct departures that must represent unrecognized smaller‐scale fluctuations of the process.
Measurements of subtidal flow in the Lesser Antilles Passages
Authors: Mazeika Paul A. , Kinder Thomas H. , Burns Donald A.
Published: February 2008

During 1977 we obtained current meter records for up to 284 days length in the two southernmost passages of the Lesser Antilles, St. Vincent Passage, and Grenada Passage. The sub‐inertial velocity variances accounted for 15–77% of the total record variances and the amplitudes of these sub‐inertial fluctuations were similar to record means. The deepest current meters (25–150 m above bottom) had oscillations of about a 14 day period, whereas shallower current meters (greater than 400 m above bottom) were dominated by fluctuations with greater than 30 day periods.
The origin of the 100‐kiloyear ice sheet cycle in the Pleistocene
Authors: Watts Robert G. , Hayder Md. Ehteshamul
Published: February 2008

The response of a simple ice sheet model forced by a periodic change in the climate point exhibits a bifurcation when certain dimensionless parameters undergo realistic changes. It is postulated that this bifurcation may be responsible for the initiation of large glacial cycles about 700,000 years ago following smaller, higher frequency ice sheet advances and retreats before that time.
Characterization of the atmospheric aerosol over the eastern equatorial Pacific
Authors: Maenhaut Willy , Raemdonck Hans , Selen André , Van Grieken René , Winchester John W.
Published: February 2008

By using a polyester sailboat as sampling platform, a series of duplicate aerosol samples was collected by cascade impactors on a trip from Panama to Tahiti in 1979. Elemental analysis mainly by particle‐induced X ray emission (PIXE) indicated, in the samples collected between Panama and the Galapagos Islands, the presence of a substantial crustal component (∼0.4 μg/m3), fine Cu (∼0.4 ng/m3) and Zn (∼0.6 ng/m3), and excess fine S and K (∼100 and ∼2.4 ng/m3, respectively) in addition to the major sea salt elements. The crustal component and fine Cu and Zn are suggested to result from natural continental sources (i.e., eolian dust transport from the American continents and perhaps geothermal emissions). Samples collected west of the Galapagos Islands in the southern trades showed significantly lower concentrations for the nonseawater components. The average Si and Fe levels were as low as 4.8 and 3.3 ng/m3, corresponding to a maximum of 0.066 μg/m3 for an assumed mineral dust component, whereas heavy metal concentrations were all below the detection limits (typically ranging from 0.05 to 0.15 ng/m3 for V, Cr, Mn, Ni, Cu, Zn, and Se). Excess fine S decreased to a mean of 46 ng/m3, a level similar to those reported for other remote marine and continental locations. This all indicates that the marine atmosphere west of the Galapagos was little influenced by natural continental source processes or by anthropogenic emissions. Under these truly marine conditions, several concentration ratios of the major seawater elements were significantly different from those in bulk seawater. Ca, Sr, and S in >1 μm diameter particles were enriched relative to K and Na, with the enrichment being substantially more pronounced (up to 50% or higher) for l–4‐μm diameter particles than for particles >4 μm. Comparison of these data with a similar data set from samples collected over the Atlantic indicates that the departures from seawater composition are significantly larger for the Pacific. Differences in sea‐to‐air fractionation processes, probably involving binding of divalent cations to organic matter in the oceanic surface microlayer, are suggested as being responsible for these observations.
7Be and 210Pb total deposition fluxes at New Haven, Connecticut and at Bermuda
Authors: Turekian Karl K. , Benninger Larry K. , Dion Eric P.
Published: February 2008

The total deposition fluxes of 210Pb and 7Be were determined at New Haven, Connecticut, and Bermuda over approximately the same annual period in 1977–1978. The 210Pb flux has remained virtually constant at New Haven from 1973 to 1978, the flux in the 1977–1978 period being 1.2 dpm/cm2/y. The 210Pb flux at Bermuda is 0.69 dpm/cm2/y. This lower flux than expected from model calculations is due to the establishment of a blocking high pressure cell during the summer which deflects continental air. The 7Be fluxes at New Haven and Bermuda are 22.7 and 17.1 dpm/cm2/y, values consistent with western North Atlantic oceanic standing crop measurements, but higher than some other estimates. Where the difference cannot be attributed to differences in sampling it is ascribable to regional differences compatible with the oceanic data.