bluuebunny/crossref_metadata_2025 huggingface dataset:
H2O frost point detection on Mars?
Authors: Ryan J. A. , Sharman R. D.
Published: February 2008

The Viking Mars landers contain meteorological instrumentation to measure wind, temperature, and pressure but not atmospheric water content. The landings occurred during local summer, and it was observed that the nocturnal temperature decrease at sensor height (1.6 m) did not exhibit a uniform behavior at either site. It was expected that the rate of decrease would gradually slow, leveling off near sunrise. Instead, a leveling occurred several hours earlier. Temperature subsequently began a more rapid decrease which slowed by sunrise. This suggested that the temperature sensors may be detecting the frost point of water vapor. Analysis of alternative hypotheses demonstrates that none of these are viable candidates. The frost point interpretation is consistent with other lander and orbiter observations, with terrestrial experience, and with modeling of Mars' atmospheric behavior. It thus appears that the meteorology experiment can help provide a basis toward understanding the distribution and dynamics of Martian water vapor.
Rate of reaction of OH With HNO3
Authors: Wine P. H. , Ravishankara A. R. , Kreutter N. M. , Shah R. C. , Nicovich J. M. , Thompson R. L. , Wuebbles D. J.
Published: February 2008

The kinetics of the reaction OH + HNO3→k2products has been studied over the temperature range 224–366 K. OH radicals were produced by pulsed (laser or flash lamp) photolysis of HNO3. The course of the reaction was monitored by detecting OH using the resonance fluorescence technique. A total of 27 bimolecular rate constants (derived from 150 individual experiments) were determined under varying conditions of temperature, pressure, photolysis photon flux and wavelength, diluent gas identity, and flow rate. In all experiments the HNO3concentration was constantly monitored by 184.9‐nm absorption. The data are best described by the following Arrhenius expression:k2= (1.52 ± 0.38) × 10−14exp [(+649 ± 69)/T] cm3molecule−1s−1. The stratospheric implications of these new rate data have been assessed by using a one‐dimensional transport‐kinetic model. Reductions in O3depletion due to chlorofluoromethane release and NOxinjection are calculated. The magnitude of these reductions is strongly dependent on the identity of the reaction products.
Observations of a summertime reversal in circulation in the Strait of Juan De Fuca
Authors: Frisch A. S. , Holbrook J. , Ages A. B.
Published: February 2008

While measuring currents in the Strait of Juan de Fuca, we recorded an unusual 3‐day reversal in the surface current, from seaward to landward, in apparent response to the southerly winds of a coastal storm. The reversal was monitored by four surface drifters and three moored current meter arrays that recorded the current at 20‐ to 130‐m depths. Spatial details of the reversal pattern, mapped by an HF current‐sensing radar at the boundary between the inward and outward flow, showed a complex surfacecirculation pattern with a strong southerly flow toward New Dungeness Spit. Although such reversals have been previously recorded in nonsummer months, their appearance in the summer, when coastal cyclonic storms are uncommon and river discharge is high, is unusual.
Atmospheric CO2 and climate: Importance of the transient response
Authors: Schneider Stephen H. , Thompson Starley L.
Published: February 2008

Preliminary studies suggest that the thermal inertia of the upper layers of the oceans, combined with vertical mixing of deeper oceanic waters, could delay the response of the globally averaged surface temperature to an increasing atmospheric CO2 concentration by a decade or so relative to equilibrium calculations. This study extends the global analysis of the transient response to zonal averages, using a hierarchy of simple energy balance models and vertical mixing assumptions for water exchange between upper and deeper oceanic layers. It is found that because of the latitudinal dependence of both thermal inertia and radiative and dynamic energy exchange mechanisms, the approach toward equilibrium of the surface temperature of various regions of the earth will be significantly different from the global average approach. This suggests that the actual time evolution of the horizontal surface temperature gradients— and any associated regional climatic anomalies—may well be significantly different from that suggested by equilibrium climatic modeling simulations (or those computed with a highly unrealistic geographic distribution of ocean thermal capacity). Also, the transient response as a function of latitude is significantly different between globally equivalent CO2 and solar constant forcing runs. It is suggested that the nature of the transient response is a major uncertainty in characterizing the CO2 problem and that study of this topic should become a major priority for future research. An appendix puts this issue in the context of the overall CO2 problem.
A mechanism for the formation of large icebergs
Authors: Holdsworth G. , Glynn J. E.
Published: February 2008

The calving of floating glaciers to form icebergs is a major form of ice loss from the Antarctic ice sheet. Disintegration of massive, unconfined, seaward extending ice shelves or glacier tongues gives rise to the largest type of iceberg, some of which have horizontal dimensions exceeding 100 km. Several ice tongues are known to exhibit a quasi‐cyclic pattern of calving and subsequent regrowth. A mechanism that would seem to explain this type of calving behavior is based on the vibrational characteristics of the system of a buoyant ice plate floating in shallow water. Ocean wave energy, responsible for the motion, is intercepted by the glacier, either directly from open ocean or after transmission through, and subsequent filtering by, sea ice. The glacier also acts as a wave filter, with filtering characteristics depending on the ice thickness. When a dominant frequency occurring in the incident wave spectrum coincides with one of the natural frequencies of the glacier, then a resonant motion will occur. For relatively high modes of oscillation, low level, but sustained cyclic bending stresses may lead to crack propagation and subsequent fatigue failure in the ice. The contribution of other mechanisms which induce tensile stresses in the ice are considered to be very important in an overall view of the calving problem, and some of these mechanisms are discussed in relation to the vibration mechanism. It is possible to view the proposed vibration mechanism as a trigger which raises the resultant stresses in the ice to the point where fracture will occur.
Seasonal and latitudinal variation of 14CO and the tropospheric concentration of OH radicals
Authors: Volz Andreas , Ehhalt Dieter H. , Derwent Richard G.
Published: February 2008

Ground‐based measurements of the concentration of 14CO are reported. The data exhibit a well‐defined seasonal variation at mid‐latitudes with a maximum of 25 ± 2 molecule cm−3 during winter and a minimum of 11 ± 1 molecule cm−3 during summer. The measurements also indicate a strong latitudinal variation, with the lower concentrations occurring in the tropics. The data are interpreted using a 2‐D time‐dependent model. To balance the sources of both 14CO and 12CO, an average tropospheric OH concentration of (6.5‐2+3) × 105 molecule cm−3 is required. In addition, the 12CO production rate from biological processes including the oxidation of nonmethane hydrocarbons is found to be 1250 × 1012 g CO yr−1.
Ozone in the upper stratosphere and mesosphere
Authors: Prather Michael J.
Published: February 2008

A detailed photochemical model of the upper stratosphere and mesosphere is compared with three extensive sets of ozone observations: Atmospheric Explorer‐E backscattered ultraviolet experiment (BUV), Nimbus‐4 BUV, and rocket flights from Wallops Flight Center (ROCOZ). The Nimbus‐4 and rocket observations are most sensitive to ozone between 30 and 50 km, whereas observations from AE‐E measure the abundance of ozone up to 70 km. The photochemical model accurately reproduces the observed relationship between BUV intensity and local solar zenith angle, although the absolute calibration on AE‐E appears to be in error. The AE‐E observations and the model both exhibit a morning‐afternoon asymmetry, with more ozone in the morning owing to the build up of HOx species in the afternoon. Seasonal changes in atmospheric temperature produce an annual maximum in tropical mesospheric ozone during June‐July‐August. The amplitude of the observed effect is somewhat larger than calculated by the model. Some problems appear to remain with the presently accepted kinetic rates for HOx species in the atmosphere.
Sea level variations in relation to coastal flow around the Gulf of Alaska
Authors: Reed R. K. , Schumacher J. D.
Published: February 2008

Adjusted sea level deviations at six tide stations around the Gulf of Alaska were examined in light of our recent knowledge of the flow regime. On the east side of the gulf, a maximum in the deviations seems to be caused by winter barotropic flow on the shelf. On the north side of the gulf, the maximum in fall is apparently produced by a marked increase in flow of the baroclinic coastal current. Farther west the seasonal sea level signal is appreciably reduced.
Satellite‐tracked drift buoy observations of the near‐surface flow in the eastern mid‐latitude North Pacific
Authors: McNally Gerard J.
Published: February 2008

The surface and near‐surface (30 m) currents of the eastern mid‐latitude Pacific obtained from 32 satellite‐tracked drifting buoys during the period June 1976 through August 1977 are discussed. These observations of oceanic currents are merged with and are compared to Fleet Numerical Weather Center's daily estimates of surface winds for the same period. Statistical comparisons of these data sets reveal that the drifters move systematically approximately 30° to the right of the surface wind at approximately 1.5% of the wind speed. This relationship between drifter movement and surface winds occurs during the entire period except for the summer months of 1976 when independent of the surface winds the buoy trajectories indicate mesoscale eddy motions with 100 km and 30 day time and space scales, respectively. Drifter liftimes exceeded that of the 9‐m diameter parachute drogues set at 30 m depth, thus enabling a comparison of the currents derived from the drifter motions at the surface and 30 m. These comparisons reveal no systematic difference in the drifter motions with and without drogues. These results suggest a rather uniform flow in the upper 30 m during periods of steady winds. The estimates of the nature of near‐surface currents obtained from the drifters differ from those predicted by Ekman's classical theory of wind‐driven flow, in that there is no evidence of either a reduction in speed or change in direction of the currents over the upper 30 m.
On the distribution of copper, nickel, and cadmium in the surface waters of the North Atlantic and North Pacific Ocean
Authors: Boyle Edward A. , Huested Sarah S. , Jones Susan P.
Published: February 2008

Concentrations of copper, nickel, and cadmium have been determined for about 250 surface water samples. Nonupwelling open‐ocean concentrations of these metals are Cu, 0.5–1.4 nmol/kg; Ni, 1–2 nmol/kg; and Cd, less than 10 pmol/kg. In the equatorial Pacific upwelling zone, concentrations of Ni (3 nmol/kg) and Cd (80 pmol/kg) are higher than in the open ocean, but Cu (0.9 nmol/kg) is not significantly enriched. Metal concentrations are higher in cool, nutrient‐rich eastern boundary currents: Cu, 1.5 nmol/kg; Ni, 3.5 nmol/kg, and Cd, 30–50 pmol/kg. Copper is distinctly higher in the coastal waters of the Gulf of Panama (3–4 nmol/kg) and also higher in the shelf waters north of the Gulf Stream (2.5 nmol/kg); these copper enrichments may be caused by copper remobilized from mildly reducing shelf sediments and maintained by a coastal nutrient trap. In the open ocean, events of high‐Cu water (1.5–3.5 nmol/kg) are seen on scales up to 60 km; presumably, these are due to the advection of coastal water into the oceanic interior. The lowest copper concentrations in the North Pacific central gyre (0.5 nmol/kg; (Bruland, 1980)) are lower than in the Sargasso Sea (1.3 nmol/kg), while for nickel the lowest concentrations are 2 nmol/kg in both the North Pacific and the North Atlantic. Nickel and cadmium, while generally correlated with the nutrients in surface waters, show distinct regional changes in their element‐nutrient correlations. The residual concentrations of trace metals in the surface waters of the ocean can be explained if biological discrimination against trace metals relative to phosphorus increases as productivity decreases.
Bubble and aerosol spectra produced by a laboratory ‘breaking wave’
Authors: Cipriano Ramon J. , Blanchard Duncan C.
Published: February 2008

The relative contribution of jet and film drops from bursting bubbles to the sea‐salt component of the marine aerosol is poorly understood. An analysis of the bubble and aerosol spectra produced by a laboratory model of a breaking wave or whitecap shows that film drops may play a much more important role than previously accorded. The model strongly suggests that most of the droplets smaller than 5–10 μm in diameter originate as film drops, derived from bubbles larger than 1 mm. The water‐to‐air flux of such droplets is adequate to account for the majority of maritime cloud condensation nuclei. The model also suggests that droplets larger than 20–25 μm originate as jet drops, derived from bubbles smaller than 1 mm. The model breaking wave produces an upwelling plume of bubbles whose concentration for all bubble sizes vastly exceeds the steady state or background bubble population observed at sea at depths greater than 1 m. Bubbles of up to 10 mm diameter were produced, and the bubble flux reached 200 cm−2 s−1. Whitecap bubble spectra, presently unavailable, are therefore essential in making more accurate assessments of marine aerosol production.
Lidar observation of gravity and tidal waves in the stratosphere and mesosphere
Authors: Chanin Marie‐Lise , Hauchecorne Alain
Published: February 2008

Lidar measurements of atmospheric density and temperature in the altitude range 30‐to 80 km have been performed during the last 2 years from the Observatory of Haute‐Provence (latitude 44°N, longitude, 6°E). The potential of this technique for studying the middle atmospheric structure is presented and preliminary results on wave propagation are discussed. It is shown that wave‐like structures are observed systematically in this height range. Fourier analysis indicates that most of the energy is transported by waves of vertical wavelengths on the order of 8 to 15 km. The amplitude of the density variations is shown to follow a ρ−l/2 law up to 70 km. The characteristics of the observed density waves suggest that they are caused by a superposition of internal gravity waves propagating upward from the troposphere and a diurnal tide component in the range 30–50 km. Such waves are able to induce quite significant perturbations in atmospheric density and therefore temperature on an hourly basis. The Lidar technique is able to monitor those variations for the first time from a ground station operating continuously.
Southern hemisphere stratospheric aerosol measurements: 3. Size distribution 1974–1979
Authors: Gras J. L. , Laby Jean E.
Published: February 2008

The stratospheric aerosol particle size distribution has been measured at 34°S for the period 1974–1979. Results from two measuring techniques—in situ single‐particle counting and jet impaction—agree well. The size distribution is shown to be described equally well by either a log‐normal or zero‐order logarithmic function. Observed distributions below 22 km agree substantially with model predictions for r>0.1 μm but indicate fewer particles at smaller radii.
Geochemistry of the Amazon: 1. Precipitation chemistry and the marine contribution to the dissolved load at the time of peak discharge
Authors: Stallard R. F. , Edmond J. M.
Published: February 2008

Analyses of precipitation and surface water are used to estimate the fluxes of marine cyclic salts through that part of the Amazon River system draining past Obidos (80% of the basin) at the time of peak discharge in June. Amazon precipitation chemistry can be devided into two principal components: marine and terrestrial. The marine component (determined from analyses of marine rain) consists of Na, K, Mg, Ca, and Cl in approximately sea‐salt proportions, with S doubly enriched. The excess sulfur is probably derived from gas phase inputs. The terrestrial component makes an important contribution of K, Ca, S, and N, much of which can be related to biological emissions. The emission of reduced sulfur in the marine and terrestrial environment and nitrogen in the terrestrial environment is responsible for a natural ‘acid rain’ in the Amazon region with a pH from 4.7 to 5.7. This is about one tenth the acidity of polluted urban rain. The chloride content of lowland rivers, which drain regions lacking significant geologic sources of chloride, shows a systematic decrease in chloride with increasing distance from the ocean. This trend is used to define the cyclic salt background for Amazonian surface waters. Cyclic salts, in general, make only a minor contribution, relative to terrestrial inputs, to the chemistry of Amazon Basin rivers, even those draining intensely weathered terrains. An estimated 17.6%‐Cl, 6.9%‐Na, 1.3%‐Mg, 3.6%‐S, 0.4%‐K, and 0.1%‐Ca of the dissolved load at Obidos during peak discharge is cyclic.
Photochemistry of phosphine and Jupiter's Great Red Spot
Authors: Noy N. , Podolak M. , Bar‐Nun A.
Published: February 2008

We present the results of an experimental investigation of the ultraviolet photolysis of mixtures of phosphine in hydrogen. Under no circumstances could red phosphorus be produced in this system. Rather, the product was always yellow. The measured indices of refraction of the phosphorus produced were used to fit the variation of reflectivity of Jupiter's Great Red Spot with wavelength. It was found that the phosphorus particles have to be small (0.05 μm) and their layer should have an optical depth of about one at λ=0.4 μm.
Identification of acetylene (C2H2) in infrared atmospheric absorbtion spectra
Authors: Goldman A. , Murcray F. J. , Blatherwick R. D. , Gillis J. R. , Bonomo F. S. , Murcray F. H. , Murcray D. G. , Cicerone R. J.
Published: February 2008

Infrared atmospheric absorption spectra at ∼0.02 cm−1 resolution obtained during a balloon flight made on March 23, 1981, show absorption features attributable to C2H2. These features are used to derive a preliminary mixing ratio of ∼25 pptv near 9 km. This mixing ratio falls into the range of values we calculate for upper tropospheric C2H2 in a photochemical/transport model but well below values measured previously in samples collected by other researchers.
Compact, intrathermocline eddies in the Sargasso Sea
Authors: Dugan J. P. , Mied R. P. , Mignerey P. C. , Schuetz A. F.
Published: February 2008

We report observations of isolated lenses of constant‐temperature water embedded in the permanent thermocline in the Sargasso Sea. These features are observed to have vertical extents of ≲220 m, horizontal dimensions of ≲65 km, and residence depths near 700 m. A dynamic model is constructed which permits a balance among the pressure gradient, Coriolis, and cyclostrophic forces and maintains the lens against gravitational collapse. A result is that anticyclonic rim velocities approaching 20 cm s−1 are permitted and that these eddies have finite radii of the order of 50 km, at which their thicknesses fall to zero.
Inventory of global methane sources and their production rates
Authors: Sheppard J. C. , Westberg H. , Hopper J. F. , Ganesan K. , Zimmerman P.
Published: February 2008

On the basis of 17 ecosystems, it is estimated that 9.1×1014 g CH4/year are emitted into the atmosphere from the biosphere. Enteric fermentation in animals and humans, decomposition of organic wastes, and biomass burning contribute an additional 2.0×1014 g CH4/yr. Various fossil sources emit another 1×1014 g CH4/yr. When all sources are considered, they emit 12.1×1014 g CH4 each year. As with earlier inventories, this study indicates that the fossil methane contribution is less than 10% of the total annual global production rate. Chemical kinetic relationships are established between the bacteriamediated anaerobic decomposition of humic matter, the mean residence time (MRT) of humus, and methane fluxes. These equations and the 14C specific activity are used to obtain an average MRT of 1365 years for the earth's 1.8×1018 grams of humic carbon. Use of the global methane production rate and the concentration of atmospheric methane results in an average 3.3 year residence time and an average global hydroxyl radical concentration of 2.7×106 per cm3.
The direct and scattered solar flux within the stratosphere
Authors: Herman J. R. , Mentall J. E.
Published: February 2008

Solar ultraviolet flux data were obtained within the atmosphere by using Fastie‐Ebert double monochromators carried on a balloon‐borne gondola and a rocket payload. Both the direct and scattered components of the solar ultraviolet flux at wavelengths from 190 to 320 nm were measured at the balloon float altitude of 40 km. The nearly identical spectrometer carried on the rocket flight measured the direct solar flux from 60 to 38 km during a parachute descent. The ozone column content above 40 km and the temperature profile and ozone density below 40 km are deduced from the scattered and direct solar flux components. It is shown that the Nimbus 7 solar flux data is consistent with the present data and with the ozone absorption cross sections of Inn and Tanaka (1959). The same is not true with the solar flux data of Broadfoot (1972), where a systematic error is clearly evident. The calculated and measured values of the scattered solar flux are found to agree quite closely. The scattered flux at 40 km is shown to be 20% of the direct flux at wavelengths longer than 300 nm and about 10% within the Schumann‐Runge band region of O2. This implies increased rates of photolysis for the production of O(1D), O(3P), and other minor species throughout most of the stratosphere and mesosphere. The 10% scattering within the O2 Schumann‐Runge band region leads to a 2% increase in O3 density at 40 km.
Stability of ammonia in the primitive terrestrial atmosphere
Authors: Kasting James F.
Published: February 2008

A one‐dimensional photochemical model is used to calculate the rate at which ammonia would have been destroyed in the earth's atmosphere for assumed NH3 mixing ratios of 10−8 to 10−4. The calculated NH3 destruction rates are then compared with possible abiotic and biotic sources for ammonia. Abiotic sources were probably sufficient to maintain the NH3 mixing ratio of 10−8 needed for life to have evolved but were too small to sustain the mixing ratios of 10−5 or more necessary to produce significant greenhouse warming. The atmospheric ammonia concentration may have increased during the Archean as a result of biological activities but probably remained below the level required to generate measurable thermal effects.
Space charge layers created by coronae at ground level below thunderclouds: Measurements and modeling
Authors: Chauzy S. , Raizonville P.
Published: February 2008

High electric fields created by thunderclouds at ground level are enhanced by the irregularities of the surface. This causes corona discharges to occur. The generated ions, when they are not blown away, form a space charge layer which reduces the magnitude of the electric field at ground level. During the LANDES 79 experiment (south western France), electric field soundings have been performed. The sensor is a balloon‐borne double field‐mill device designed for measuring the vertical and horizontal components of the external electric field. At several occasions, a strong vertical field increase with height was detected in the lower part of the sounding. This reveals the existence of important space charge layers near the ground. Space charge density profiles are deduced from electric field soundings. They display density values running from 2 to 7 nC m−3, distributed over shallow layers. A numerical model taking into account ion capture by the neutral aerosol particles leads to theoretical charge density profiles which display features close to those of the experimental profiles. Computation shows that the initial number of neutral aerosol particles has a drastic effect on both density maximum values and layer depths. According to aerosol density, charge density values run from 0.6 nC m−3 (in clean air) up to 3.1 nC m−3 (high aerosol density).
Solution of the equation of radiative transfer for remote sensing over nonuniform surface reflectivity
Authors: Kaufman Yoram J.
Published: February 2008

A fast yet accurate approximate solution has been developed for radiative transfer in an atmosphere bounded by a surface with nonuniform reflectivity for the purpose of remotely sensing aerosol characteristics (optical thickness and scale height). This solution is derived for the upward radiation at zenith for scattering and absorbing atmospheres and with surface reflectivity in the form of a ‘two‐halves’ field (two halves of field of a different reflectivity such as a sea shore). Any vertical distribution of absorbers and scatterers can be used. The resultant solution is used to develop expressions for the atmospheric line spread function and the atmospheric Modulation Transfer Function. This function can be applied to calculate the upward radiance for any surface reflectivity. The results of calculations are compared with numerical results calculated by the Monte Carlo method. The present results are shown to fit the Monte Carlo calculations almost exactly. This comparison shows that the present fast solution can be used for any surface reflectivity when aerosol optical thickness τA ≤ 1, and from the near UV to the near IR spectrum. The solution is also compared with high resolution satellite data (80 m resolution) obtained from Landsat 1 images of the African coast taken during ground measurements of the aerosol characteristics. The comparison shows that the present approximation can predict the measured radiances over a nonuniform surface reflectivity. It is shown that the horizontal range of the adjacency effects (the range at which the high reflectivity area affects the zenith radiance over the low reflectivity area) are proportionally dependent on the average elevation of the aerosols while independent of their exact vertical profile. In addition, this range is not very sensitive to the aerosol size distribution, optical thickness, and surface reflectance. Thus, this range can be used to retrieve the scale height of aerosols from zenith radiances detected from space.
Longshore dispersion over a flat beach
Authors: Ostendorf David William
Published: February 2008

We model the longshore dispersion of a passive, conservative pollutant in the surf zone formed by two‐dimensional, monochromatic water waves of near‐normal incidence breaking over a plane, flat, impermeable beach under presumedly uniform temporal, vertical, and longshore conditions. Such pollutants disperse in a Fickian manner through a plane moving at the areal averaged longshore current speed when the shore‐normal concentration variation is small, with a longshore dispersivity reflecting diffusive and advective transport processes. We adopt an existing estimate of the turbulent diffusion and modify an existing longshore current model to derive a theoretical estimate of the longshore dispersivity; we calibrate the simple model with field data, generating accurate and physically plausible results.
The role of sublimation and condensation in the formation of ice sheet surface at Mizuho Station, Antarctica
Authors: Fujii Yoshiyuki , Kusunoki Kou
Published: February 2008

Three methods were used to determine the sublimation and condensation at Mizuho Station in 1977–1978, that is, direct observations with an evaporimeter filled with ice and repeated measurements of offset stakes and indirect estimation using an empirical formula derived from meteorological parameters. A comparison of three methods shows satisfactory agreement, especially in the weekly average of sublimation in the 1977–1978 summer, while condensation is insignificantly small. Condensation prevailed from the middle of April to the middle of September and sublimation in the remainder of 1977. The annual amounts of condensation and sublimation in 1977 are estimated to be 0.6 g cm−2 and 5.4 g cm−2, respectively. The daily amount of sublimation showed its maximum of 92 mg cm−2 on December 22, 1977, at the summer solstice. The annual amount of sublimation much affected the annual net accumulation of 5.8 g. The sublimation and condensation contributed in the formation of glazed surface consisting of multilayered ice crusts. This glazed surface is representative in the katabatic wind region in Mizuho Plateau, and the structure of the ice crust reflects the mass balance due to sublimation and condensation on both sides of the crust. Sublimation rate varies with the direction of the sloping faces of sastrugi, being the maximum on the north‐facing slope, which receives the maximum solar radiation.
In situ holographic measurements of the sizes and settling rates of oceanic particulates
Authors: Carder Kendall L. , Steward Robert G. , Betzer Peter R.
Published: February 2008

A free‐floating sediment trap equipped with a holographic particle velocimeter (HPV) was deployed for 14.4 hours at a depth of 30 m in the western North Atlantic Ocean. The system recorded the in situ sizes, shapes, orientations, and settling rates of microscopic particles moving through the laser beam. The primary data reduction revealed particles from the system's lower limit of resolution, 15 micrometers in diameter, to 250 micrometers in diameter with settling velocities ranging from 0.0190 to 0.2302 cm/s (16–198 m/day). Individual particle densities, calculated from a modified Stokes equation, ranged from 1.37 to 5.10 g/ml. The presence of high density particles was independently corroborated through individual particle analysis of the trapped material with a computer‐controlled, scanning electron microscope equipped with an energy dispersive X‐ray analyzer. In the future, in situ holographic systems might be used to further our understanding of primary productivity, sediment erosion/deposition, and particle aggregation/disruption/dissolution.
Southern ocean bottom water of the Australian‐New Zealand sector
Authors: Rodman M. R. , Gordon A. L.
Published: February 2008

The bottom water characteristics of the southeast Indian Ocean and southwest Pacific Ocean reveal northward transfer of cold water across the mid‐ocean ridge at the Discordance Zone near 120°E and at the Balleny Fracture Zone near 155°E. A principal northward flow, which transfers cold continental margin waters of Antarctic origin to lower latitudes within the South Indian Basin, occurs to the east of Kerguelen Plateau. Within the South Indian Basin, near the 0°C isotherm, the θ/S, θ/O2, and θ/Si relations display significant slope changes. The more variable water below 0°C is of local origin, while the water above 0°C represents larger scale regional effects.
The North Atlantic tritium distribution in 1972
Authors: Sarmiento J. L. , Rooth C. G. H. , Roether W.
Published: February 2008

The distribution of tritium in the North Atlantic in 1972 is compared with the distribution of salinity and the first‐order potential voracity as mapped on six constant potential density surfaces in the North Atlantic. The picture presented suggests an advective transport regime which is consistent with currently developing notions of the large‐scale gyre structure. Lateral mixing along isopycnals appears to be important in the northwestern region of the subtropical gyre, and vertical (cross‐isopycnal) mixing needs to be invoked only in near surface layers.
Carbon monoxide in seawater (Atlantic Ocean)
Authors: Conrad R. , Seiler W. , Bunse G. , Giehl H.
Published: February 2008

In 1978–1980, measurements of dissolved carbon monoxide in seawater were carried out during three ship expeditions in the northern and southern Atlantic Ocean, covering an area between 53°N and 35°S. Measurements in surface water were performed by a continuously working equilibration technique that allowed for the determination of small and rapid variations of the dissolved CO. Carbon monoxide concentrations in the water body increased toward the sea surface, there reaching saturation factors of up to 50 with respect to atmospheric CO. The daily average CO saturation increased with average chlorophyll a concentration and light intensity and decreased with wind speed. The dissolved CO showed strong diurnal variations, with maximum values in the afternoon. Diurnal variations were observed within the entire euphotic zone, indicating that CO is both produced and consumed in the seawater. Carbon monoxide production in seawater was mainly due to photooxidation of dissolved organic matter. Photobiological and microbial CO production processes were of minor importance. Carbon monoxide destruction was due to a light‐independent microbial metabolism. Based on average CO saturation factors of 30±20 in the surface water of the ocean, the total source strength for atmospheric CO is calculated to 10–180 Tg yr−1.
Mid‐latitude model analysis of solar radiation, the upper layers of the sea, and seasonal climate
Authors: Charlock Thomas P.
Published: February 2008

A simplified, time‐dependent energy balance climate model is run at the latitude belt 40°–50°N. The model solves for the temperatures of the land, air, and 12 vertical oceanic layers, and it includes a wind stirred mixed layer. Because the attenuation of solar radiation in the model ocean varies significantly with wavelength in the visible, fine wavelength resolution radiative transfer for Rayleigh scattering and ozone absorption is used between 340 and 720 nm. The optical properties of the model clouds are functions of the cloud liquid water contents. A change in model ocean optical turbidity from relatively clear (Jerlov I) to particle rich (Jerlov III) conditions decreases the effective thickness of the oceanic layer in which heat is stored seasonally and increases the seasonal variation of sea surface temperature by 2°–3°C. A decrease in the liquid water content of clouds by a factor of 4 warms the model climate and increases the seasonal variation of sea surface temperatures by 2°–3°C. A 2°–3°C change in the seasonal variation of sea surface temperature is also obtained by varying oceanic mixing through a factor of 2 change in the surface wind speed. The model climate is also affected by a diurnal resolution of the oceanic mixed layer. The gross features of the model upper ocean isotherm structure, plotted as a functions of depth and date, are not strongly sensitive to changes in optical water type, cloud liquid water content, or wind induced mixing.
Settling velocity distribution of natural aggregates
Authors: Hawley Nathan
Published: February 2008

An analysis of previous experimental determinations of aggregate settling rates for particles <100 μm in diameter shows that these particles fall significantly more quickly than Stokes' law predicts, with the deviations being most pronounced for smaller particles. This implies that previous sediment flux calculations which have used a form of Stokes' law to obtain aggregate velocities may have significantly underestimated the contribution from the smaller aggregates. The measured fall velocity distributions are described as the sum of normally distributed populations (four for the lacustrine data, two for the marine) whose means, standard deviations, and weights have been determined. Sample calculations of collision frequency show that because of the increased settling velocities and the use of a distribution of velocities for a given particle size, collisions due to differential settling rates are the governing nonbiological process in the formation of natural aggregates.
A note on cross spectrum and coherence calculations
Authors: Saunders Kim David , Hamrick Fred C.
Published: February 2008

The physical oceanographic literature contains many instances of cross spectral and coherence calculations in which statistical stability is achieved through band averaging of the cross spectrum in frequency space. ‘Constant Q’ averaging is often used, sometimes with unexpected results. We show how ‘constant Q’ frequency smoothing of the cross spectrum can lead to erroneous estimates of coherence. We propose that the well known technique of segment averaging using a number of raw spectral estimates computed from a sequence of time‐domain windowed data be used for routine coherence (or cross‐spectrum) calculations. The effects of window shape on coherence estimation are also considered.
The role of active volcanism in enrichment of the atmosphere in chalcophile elements
Authors: Menyailov I. A. , Nikitina L. P. , Shapar V. N. , Miklishansky A. Z.
Published: February 2008

A study made on the geochemistry of gaseous products for the Tolbachik basaltic eruption in Kamchatka (1975–1976) has shown that magmatic gases, submicron ash, and aerosols are enriched in chalcophile elements. Active volcanism represents one of the main sources. The annual input of chalcophile elements from the volcanoes of the world to the atmosphere is found to be in agreement with the amounts brought into the oceans by the water‐soluble component of the river runoff.
A model for microwave emission from vegetation‐covered fields
Authors: Mo T. , Choudhury B. J. , Schmugge T. J. , Wang J. R. , Jackson T. J.
Published: February 2008

A radiative transfer model for simulating the measured brightness temperatures over vegetation‐covered fields is studied. The model treats the vegetation as a uniform layer, or canopy, with a constant temperature over a moist soil which emits polarized microwave radiation. The equation of radiative transfer is solved analytically subject to boundary conditions at the soil surface and canopy top. Scattering by the vegetation is primarily in the forward direction and given by a single scattering albedo ω*. The effect of soil surface roughness is introduced by modifying the smooth surface reflectivity with a roughness height parameter h and polarization mixing factor Q. The analytic formula for the microwave emission has four parameters, h, Q, τ0* (effective canopy optical thickness), and ω*. The model provides a good representation of the observed angular variations for both the horizontally and vertically polarized brightness temperatures at 1.4 GHz and 5 GHz frequencies over fields covered with grass, soybean, and corn. The effective canopy optical thickness is found to be directly proportional to the amount of water present in the vegetation canopy, while the effective canopy single scattering albedo depends on the type of vegetation.
A branch grain theory of temperature gradient metamorphism in snow
Authors: Sommerfeld Richard A.
Published: February 2008

Temperature gradient metamorphism in snow results in the development of branch grains at the expense of other types of grains. At constant density, the development of branch grains decreases the strength, thermal conductivity, and crystal number density while increasing the mean crystal size. A theory is developed that uses the following major assumptions: (1) at growth sites the thermal gradient is a function of crystal separation and (2) vapor flux is a function of local thermal gradient. A computer model based on the theory is compared with stereological measurements of snow from a carefully controlled experiment. The model calculates grain size distributions within the accuracy of the measurements. The major conclusion is that the theory explains the main process in temperature gradient metamorphism. The inclusion of surface energy considerations and stereological refinements would probably improve the theory when techniques for stereological analysis become more accurate.
The seasonal variation of the atmospheric SO2 to SO42− conversion rate
Authors: Meagher James F. , Bailey Elizabeth M. , Luria Menachem
Published: February 2008

Data collected during eight separate field studies conducted at four coal‐fired power plants were combined to investigate the dependence of the nonaqueous phase SO2 oxidation rate on various meteorological parameters. The data exhibited a strong seasonal trend with average morning SO2 oxidation rates varying from a winter low of 1.5×10−3 h−1 to a summer high of 1.3×10−2 h−1.
SAR imagery and surface truth comparisons of internal waves in Georgia Strait, British Columbia, Canada
Authors: Hughes B. A. , Gower J. F. R.
Published: February 2008

The surface roughness patterns caused by internal waves in Georgia Strait on the west coast of Canada were used as an imagery target for the SEASAT synthetic aperture radar (SAR) on July 30, 1978. In these patterns there is strong modulation of short surface waves including the Bragg wavelength for resonant microwave reflection. In the sheltered waters of the strait, the complicating effects of longer waves are greatly reduced. The roughness patterns were also observed with an airborne SAR, by aerial photography, and by shipborne surface roughness and subsurface current measurements. The data show the response of the SAR's to the anisotropic roughness patterns measured by the ship. The SAR signal intensity is shown to be moderately correlated with Bragg wave or total roughness energy, but not with the facet area aligned to give specular reflection.
Sea ice motion measurements from SEASAT SAR images
Authors: Leberl F. , Raggam J. , Elachi C. , Campbell W. J.
Published: February 2008

Satellite imaging radar is expected to become the prime instrument for mapping the distribution and motion of sea ice on a periodic basis, The observational independence from weather, fog, and clouds and the fact that it provides its own illumination are decisive advantages that imaging radar has in the remote sensing of sea ice. The SEASAT spacecraft launched in 1978 included such an imaging radar, and approximately one fourth of all SEASAT SAR observations are of sea ice in the Beaufort Sea. Data from seven sequential orbits of the satellite were selected to study the capabilities and limitations of spaceborne radar application to sea‐ice mapping. The results are encouraging: (1) There is no difficulty in identifying homologue ice features on sequential radar images; (2) The accuracy is entirely controlled by accuracy of the orbit data and the geometric calibration of the sensor; (3) Conventional radargrammetric methods serve well for satellite radar ice mapping; (4) Ground control points can be used to calibrate the ice location and motion measurements in the cases where orbit data and sensor calibration are lacking. Ice motion was found to be approximately 6.4±0.5 km per day. However, higher accuracies are feasible with better timing calibration of the sensor events and knowledge of the orbit. The accuracy of pixel location was also determined over land areas. It was found that with the use of one control point in 10,000 km2 the accuracy is about ±150 m. With higher density of control points (7 in 1000km2) the location accuracy improves to the image resolution (i.e., ±25 m). This is applicable for both optical and digital data.
Bottom‐water observations in the Vema fracture zone
Authors: Eittreim Stephen L. , Biscaye Pierre E. , Jacobs Stanley S.
Published: February 2008

The Vema fracture zone trough, at 11°N between 41° and 45°E, is open to the west at the 5000‐m level but is silled at the 4650‐m level on the east where it intersects the axis of the Mid‐Atlantic Ridge. The trough is filled with Antarctic Bottom Water (AABW) with a potential temperature of 1.32°C and salinity of 34.82 ppt. The bottom water is thermally well mixed in a nearly homogeneous layer about 700 m thick. The great thickness of this bottom layer, as compared with the bottom‐water structure of the western Atlantic basin, may result from enhanced mixing induced by topographic constriction at the west end of the fracture zone trough. A benthic thermocline, with potential temperature gradients of about 1.2 mdeg m−1, is associated with an abrupt increase in turbidity with depth at about 1200 m above bottom. A transitional layer of more moderate temperature gradients, about 0.4 mdeg m−1, lies between the benthic thermocline above and the AABW below. The AABW layer whose depth‐averaged suspended paniculate concentrations range from 8 to 19 μg L−1, is consistently higher in turbidity than the overlying waters. At the eastern end of the trough, 140 m below sill depth, very low northeastward current velocities, with maximums of 3 cm s−1, were recorded for an 11‐day period.
Climatic information over the last century deduced from a detailed isotopic record in the south pole snow
Authors: Jouzel J. , Merlivat L. , Petit J. R. , Lorius C.
Published: February 2008

A continuous and very detailed deuterium profile was obtained from the analysis of about 900 firn samples from the south pole representing the snow accumulated over the last 100 years. Seasonal variations are well preserved in the firn, allowing the samples to be dated back to 1887 with an accuracy probably better than 5 years. This dating is consistent with the results of other independent methods, such as stratigraphic observations (back to 1927) and artificial β radioactivity and tritium measurements (back to 1955). The resulting mean annual accumulation over the 1887–1978 period is equal to 9.2 g cm−2. The value between 1887 and 1957 (9.5 g cm−2) is significantly higher (30% and 40%) than values previously obtained at the same site over comparable time spans. A decrease in annual snow accumulation is deduced from a comparison of the 1887–1930 and 1930–1978 periods (from 10.0 to 8.5 g cm−2). From a thorough examination of data relative to the very well documented 1957–1978 period, mean annual and maximum deuterium values and annual deuterium amplitude are shown to be correlated with the corresponding mean annual and summer temperatures and the annual temperature amplitude. The degree of correlation depends on the tropospheric level considered. On the other hand, winter temperature and deuterium minima are poorly correlated, which is attributable to the large temperature inversion during winter. Experimental temperature‐isotope (D and 18O) gradients are consistent with theoretical gradients, taking into account that snow formation is a nonequilibrium process. As a whole, this work is very encouraging for the use of stable isotopes as a tool for past temperature reconstruction over periods for which only weak variation are expected. This is applied over the 1887–1978 period to the mean annual, winter, and summer temperatures along with the annual temperature amplitude.