bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations of Martian surface winds at the Viking Lander 1 Site
Authors: Murphy James R. , Leovy Conway B. , Tillman James E.
Published: February 2008

Partial failure of the wind instrumentation on the Viking Lander 1 (VL1) in the Martian sub tropics (22.5°N) has limited previous analyses of meteorological data for this site. We describe a method for reconstructing surface winds using data from the partially failed sensor and present and analyze a time series of wind, pressure, and temperature at the site covering 350 Mars days (sols). At the beginning of the mission during early summer, winds were controlled by regional topography, but they soon underwent a transition to a regime controlled by the Hadley circulation. Diurnal and semidiurnal wind oscillations and synoptic variations have been analyzed and compared with the corresponding variations at the Viking Lander 2 middle latitude site (48°N). Diurnal wind oscillations were controlled primarily by regional topography and boundary layer forcing, although a global mode may have been influencing them during two brief episodes. Semidiurnal wind oscillations were controlled by the westward propagating semidiurnal tide from sol 210 onward. Comparison of the synoptic variations at the two sites suggests that the same eastward propagating wave trains were present at both sites, at least following the first 1977 great dust storm, but discordant inferred zonal wave numbers and phase speeds at the two sites cast doubt on the zonal wave numbers deduced from analyses of combined wind and pressure data, particularly at the VL1 site where the signal to noise ratio of the dominant synoptic waves is relatively small.
Meteorological survey of Mars, 1969–1984
Authors: Beish Jeffrey D. , Parker Donald C.
Published: February 2008

Results of a survey of Martian blue, blue‐white, white, and dust clouds contained in the observational archives of the Association of Lunar and Planetary Observers and in the personal files of the late C.F. Capen, Jr. are presented. A statistical analysis of data extracted from the records of 9650 visual and photographic observations of Mars made from 1969 through 1984 has been performed. Seasonal frequencies and trend analyses for each type of observed Martian meteorology are presented.
Ice haze, snow, and the Mars water cycle
Authors: Kahn Ralph
Published: February 2008

Images of the limb of Mars reveal discrete cloud layers between 20 and 80 km above the surface. They appear to be composed of water ice and have a number of characteristics similar to hazes that produce “diamond dust” precipitation in the continental Antarctic of Earth. Temperatures from 170 K to 190 K are deduced at the condensation levels. Eddy diffusion coefficients around 105 cm2 s−1, typical of a nonconvecting atmosphere, are also derived in the haze regions at times when the atmosphere is relatively clear of dust. This parameter apparently changes by more than 3 orders of magnitude with season and local conditions, with important implications for vertical transport of water and dust and for models of photochemistry and middle atmosphere dynamics. For the cases studied, particle sizes vary systematically by more than an order of magnitude with condensation level, in such a way that the characteristic fall time for particles is always about 1 Mars day, which is the dominant thermal forcing time. The hazes may play a key role in the seasonal water cycle of Mars. They provide a mechanism for growing particles large enough to move atmospheric water closer to the surface, thereby improving the efficiency of adsorption and ice deposit formation in the regolith. This is particularly likely in late northern summer, when the rapid hemispheric decrease in atmospheric water vapor may reflect the precipitation of snow. This rapid decrease in late summer involves atmospheric water vapor in about the quantities needed to supply the mid‐latitude regolith with the water that appears in the atmosphere early in the following spring.
A post‐Pioneer Venus reassessment of the Martian dayside ionosphere as observed by radio occultation methods
Authors: Zhang M. H. G. , Luhmann J. G. , Kliore A. J. , Kim J.
Published: February 2008

The dayside altitude profiles of the electron density obtained with the radio occultation experiments on Mariners 4, 6, 7, and 9 and the Viking 1 and 2 spacecraft are collectively reanalyzed to determine the global characteristics of the dayside ionosphere of Mars. These analyses concentrate on the comparison of the properties of both the electron density peaks and the topside profiles with the behavior expected for a Chapman layer and that observed at Venus with the Pioneer Venus orbiter radio occultation experiment. As at Venus, the peak densities at Mars behave much like Chapman layer peaks with only slight departure from a (cosθ)½ dependence, where θ is the solar zenith angle. In contrast, the peak heights depart from ideal Chapman layer behavior at Venus but not at Mars because the dayside neutral atmosphere at Venus depends on solar zenith angle. The global dust storm during the Mariner 9 main mission appears to have elevated the Martian ionosphere as a whole by ∼20–30 km without otherwise notably altering its density profile. These results generally corroborate the findings of earlier studies. An examination of the solar zenith angle dependence of density levels on the topsides of profiles obtained both at Mars and at Venus near solar minimum provides a new perspective on the solar zenith angle variation of the scale heights of the two ionospheres. The key contribution of this study is the improved picture of the solar zenith angle dependences of both the peaks and scale heights of the ionosphere of Mars and their comparison with Venus at solar minimum. In particular, this study illustrates that under the similar conditions where incident solar wind dynamic pressure exceeds peak ionospheric thermal pressure, the Martian dayside ionosphere peaks at higher altitudes in the flanks and has a greater scale height overall. Thus, even (magnetically) unshielded Martian and Venusian ionospheres would present slightly different obstacles to the solar wind.
Phase relations in the transition zone
Authors: Gasparik Tibor
Published: February 2008

Phase relations in the systems MgO‐Al2O3‐SiO2 and CaO‐MgO‐SiO2 have been investigated experimentally at 166–226 kbar pressures and 1350°–2500°C temperatures with a split sphere anvil apparatus (USSA 2000). MgSiO3 ilmenite is stable to lower pressures (175 kbar) than found previously. CaSiO3 perovskite forms at P(bar)=15T(°C)+151,000. Three new high‐pressure phases are reported: a phase with the diopsidic composition (the CM phase), a high‐pressure polymorph of Al2O3, and superphase B with the tentative composition Mg10Si3O14 (OH, F)4. The invariant point for coexisting majorite (Mg4Si4O12), perovskite (MgSiO3), beta phase (Mg2SiO4), and liquid has been located at 224 kbar, 2430°C, with the eutectic melt composition on the enstatite‐forsterite join at 40–44 wt% of forsterite. The melting temperature of MgSiO3 perovskite at 225 kbar is predicted to be 2600°C. The new data made possible the calculation of a temperature‐pressure phase diagram for the system CaO‐MgO‐Al2O3‐SiO2 (CMAS) in the pressure range 0–280 kbar. The mineralogy of the Earth's mantle and the possible mechanisms for producing large seismic velocity gradients in the transition zone are discussed on the basis of the derived phase relations.
The origin of fluvial valleys and early geologic history, Aeolis Quadrangle, Mars
Authors: Brakenridge G. Robert
Published: February 2008

In southern Aeolis Quadrangle in eastern Mars, parallel slope valleys, flat‐floored branching valleys, V‐shaped branching valleys, and flat‐floored straight canyons dissect the heavily cratered plateau sequence. Associated knife‐like ridges are interpreted as fissure eruption vents, and thin, dark, stratiform outcrops are interpreted as exhumed igneous sills or lava flows. Ridged lava plains are also common but are not themselves modified by fluvial processes. I mapped 56 asymmetric scarps or ridges that are probable thrust faults. These faults exhibit an orientation vector mean of N63°W±11° (95% confidence interval), and they transect the lava plains and the older plateau sequence units. By comparison, the vector mean for the 264 valleys mapped is N48°W±12°, with a larger dispersion about the mean. The similar orientations displayed by thrust fault and valley axes suggest that valley locations are partly controlled by preexisting thrust faults and related fracture systems. Most valleys are also arranged orthogonally to, and along the perimeter of, the ridged plains. A possible model for valley development is: (1) freshly outgassed water became entombed as frost, snow, and ice within the cratered terrains during heavy bombardment and the accompanying deposition of impact ejecta, volcanic ash, and eolian materials, (2) effusive volcanism and lava sill emplacement heated subsurface ice in the vicinity of the ridged plains, and faults and fractures provided zones of increased permeability for water transport to the surface, and (3) headward sapping at thermal springs, thermokarst subsidence, and limited downvalley fluid flows then carved and modified the valleys.
Magmatic inclusions in the Holocene rhyolites of Newberry Volcano, central Oregon
Authors: Linneman S. R. , Myers J. D.
Published: February 2008

The 1350 years B.P. Big Obsidian Flow (BOF) at Newberry Volcano in central Oregon contains a wide variety of mafic magmatic inclusions. Although little grain size variation is observed within single inclusions, within the suite textures vary continuously from fine‐grained (“quench”) to coarse‐grained (“cumulate”). The BOF inclusion suite, therefore, defies conventional genetic classifications. Detailed petrographic and geochemical observations require a new model for inclusion formation. Only a few of the finer‐grained inclusions have margins suggestive of liquid‐liquid interaction. Interstitial glass content (≈ 20 vol %) and composition (high‐silica rhyolite) are approximately constant throughout the suite. Mineral compositional zoning is greater in the coarse‐grained than fine‐grained inclusions. Whole inclusion compositions vary significantly but do not correlate well with textural diversity. We interpret the BOF inclusion suite to be a heterogeneous sample set of whole inclusions and parts of disaggregated inclusions. The compositional variability of the suite can be explained by a combination of preentrapment (hybridization) and postentrapment (interstitial liquid loss/gain) processes. Preentrapment hybridization involved mixing of basaltic andesite magma similar to Holocene flank flows and up to 30% rhyolitic liquid. The BOF inclusions may demonstrate the recent existence of mafic magma in the Newberry system. Inclusion features characteristic of small ΔT are consistent with the crystal‐free nature of the BOF, suggesting that the rhyolite may have been superheated. If true, a crystal fractionation origin for the BOF rhyolite is unlikely. The disaggregation of grain size and compositionally zoned inclusions, which produced the observed textural diversity in the BOF suite, compounds problems of interpreting mafic inclusions in silicic volcanic rocks and, more so, in plutonic equivalents.
Paleomagnetic evidence for proterozoic tectonism in the Kapuskasing Structural Zone, Ontario
Authors: Symons D. T. A. , Vandall T. A.
Published: February 2008

The Kapuskasing Structural Zone (KSZ) in the Superior Province of north‐central Ontario is thought to be an oblique cross‐section through Middle Archean crust. Samples from 30 sites in granulite gneisses and anorthosites of the KSZ have been analyzed using alternating field and thermal demagnetization methods. Three remanent magnetization components were found with mean directions of: D = 23°, I = 50° (k =52, α95 = 11°, N = 5 sites) for the A component; D = 73°, I = −68° (k = 50, α95 = 5°, N = 18) for the B component; and D = 332°, I = −59° (k = 53, α95 = 17°, N = 3) for the C component. V. Constanzo‐Alvarez and D. J. Dunlop found similar A and B components in less metamorphosed rocks from the same units to the immediate west. They attributed the A component to uplift at 2.55 Ga with subsequent 15° to 30° WNW tilt and the B component to thermochemical overprinting at 1.1 Ga as the KSZ was reactivated during Keweenawan rifting and volcanism. We also attribute the A component to uplift during the 2.55 Ga Kenoran Orogeny with concomitant 10°±5° WNW downward tilting before intrusion of the 2.45 Ga Matachewan dikes, to give its present paleopole of 33°E, 67° (dp = 6°, dm = 9°, N = 13) using data from both studies. We attribute acquisition of the B component to uplift at about 1.88 Ga, as suggested by recent thermal modeling and tectonic syntheses, to give a paleopole of 124°W, 30°N (dp = 7°, dm = 8°, N = 20). The C component is found in only three sites and may be either an hybrid of a 1.1 Ga Keweenawan CRM with the B component or a fault‐block tilted B component near the Ivanhoe Lake cataclastic zone.
Discharge rates of fluid and heat by thermal springs of the Cascade Range, Washington, Oregon, and northern California
Authors: Mariner R. H. , Presser T. S. , Evans W. C. , Pringle M. K. W.
Published: February 2008

Fluid and heat discharge rates of thermal springs of the Cascade Range have been determined using the chloride inventory method. Discharge rates of thermal spring groups range from 1 to 120 L s−1. Most of the fluid (50%) and heat (61%) are discharged from two hot spring groups in northern Oregon. Total discharge from thermal springs in the Cascade Range of California, Oregon, and Washington is about 340 Ls−1, which corresponds to about 8.2×104 kJ s−1 of heat. This does not include hot springs developed on the flanks of Mount St. Helens after the 1980 eruption. The Cascade Range consists of geologically and technically distinct segments; rates of convective heat discharge by the thermal springs in these segments correlate with volcanic rock extrusion rates for the last 2 m. y. In Oregon and Washington, many streams without known thermal or mineral springs in their drainage basins also were sampled for chloride and sodium to detect chemical anomalies that might be associated with previously unknown thermal or mineral waters. Only three chloride anomalies not associated with known thermal or mineral springs were identified in the streams of the Cascade Range.
Geoscience laser ranging system: Estimated accuracy of geodetic parameters and their dependence on system characteristics
Authors: Cohen Steven C. , Chinn Douglas S. , Dunn Peter J.
Published: February 2008

Covariance analysis of the performance of the Geoscience Laser Ranging System (GLRS) indicates that three‐dimensional relative positions can be recovered to an accuracy of several millimeters over spatial scales from a few kilometers to several hundred kilometers and over temporal scales as short as several days. The key factors influencing the accuracy are range noise, number of targets and their locations, system pointing capability, dwell time on the targets, orbital geometry, and gravity field uncertainties. Based on the present trade‐off studies, GLRS is designed to provide range measurements with 10 mm or better accuracy, fire at a rate of 40 pulses‐per‐seeond, point over a cone extending to 50° from nadir, and operate with a dwell time on individual targets of 2 s or less. Given a strain rate of 10−14/s, estimated GLRS accuracy parameters suggest that the deformation can be detected in less than a month if it extends over 100 km and in less than 6 months if it extends over 10 km.
Introduction to Special Section on the California‐Arizona Crustal Transect: CACTIS, Part 2
Authors: Haxel Gordon B. , Simpson Robert W. , Howard Keith A.
Published: February 2008

In May 1988, a multidisciplinary conference was held in Flagstaff, Arizona, to synthesize recent research on the crustal structural and evolution of a transect across the southern Cordillera. This transect extends from the southern Colorado Plateau southwestward across the Arizona Transition Zone, through the Basin and Range province in the Mojave and Sonoran deserts, to the San Andreas fault system, and thence westward across the Imperial Valley and Peninsular Ranges and into the southern California Borderland. Most discussion concerned the eastern part of the transect, from the Colorado Plateau to the San Andreas fault [Sass et al., 1988;Howard et al., 1990]. For this meeting, the name CACTIS (California‐Arizona Crustal Transect‐Interim Synthesis) was coined by J. Sass.
Magnetization during low‐temperature oxidation of seafloor basalts: No large scale chemical remagnetization
Authors: Beske‐Diehl S. J.
Published: February 2008

Difficulty in removing the effects of grain size dependence have hampered interpretations of magnetic property changes during low‐temperature oxidation of titanomaghemite. For the present study, samples were collected perpendicular to cracks in seafloor basalts to produce subsamples of essentially constant grain size but varying degree of low‐temperature oxidation within a few centimeters. Coarse‐grained samples and those showing evidence of high‐temperature oxidation were excluded. Increasing Curie temperature was used as the most reliable measure of increasing maghemitization. Intensity of natural remanent magnetization (JNRM) consistently decreased with increasing low‐temperature oxidation indicating that any increase in JNRM with age of oceanic crust must be due to other factors. Coercive force (HC) increased until Curie temperatures reached 250°C and then, in samples exhibiting single‐domain behavior, decreased drastically. Because coercive force depended on degree of oxidation in this complex manner, chemical remanent magnetization (CRM) in even slightly oxidized grains should have a different coercivity than the original thermal remanent magnetization (TRM). Most Deep Sea Drilling Project samples in this study have experienced tectonic rotations or field reversals within 1.0 m.y. of extrusion. Thus, field‐controlled CRM, if present, should have different coercivities and a discrete direction and be discernible during alternating field (AF) demagnetization. Alternating field demagnetizations showed no evidence for significant acquisition of field‐controlled CRM. Viscous remanent magnetization (VRM) was the dominant secondary magnetization in samples with several components of remanence. In very fine‐grained basalts, VRM was difficult to remove by AF demagnetization and may be the source of increased dispersion in highly oxidized, oceanic basalts. Mechanisms which may, in part, be responsible for coercivity and VRM changes are (1) an increase in the critical size of domain transitions during low‐temperature oxidation, and (2) incipient phase separation into Fe‐rich and Ti‐rich areas, the Fe‐rich areas being superparamagnetic. The latter mechanism explains the increase in saturation magnetization (JS) and concomitant decrease in JNRM when Curie temperatures are above 360°C.
Structural and electronic properties of Fe2SiO4‐fayalite at ultrahigh pressures: Amorphization and gap closure
Authors: Williams Q. , Knittle E. , Reichlin R. , Martin S. , Jeanloz R.
Published: February 2008

X ray diffraction and infrared spectroscopic measurements to pressures of 45–50 GPa, electrical resistivity and optical absorption to 70–80 GPa, and reflectance measurements to 225 GPa are presented for Fe2SiO4 fayalite at 300 K. Diffraction results document that Fe2SiO4 fayalite becomes amorphous on static loading to pressures in excess of 39 (±3) GPa, a pressure identical to that at which the “mixed phase” regime of fayalite commences under shock compression. As with more polymerized silicates, the high‐pressure amorphization of metastable fayalite is associated with the SiO4 tetrahedron becoming unstable relative to higher coordinations of silicon. Infrared absorption spectroscopy reveals the pressure‐induced change in coordination through a decline in intensity of the tetrahedral asymmetric stretching vibration, accompanied by an increase in amplitude at frequencies characteristic of SiO6 vibrations. The coordination change is not quenchable to zero pressure, and infrared spectra of amorphous fayalite quenched from pressure document that the local structure of the sample is similar to that of crystalline Fe2SiO4. This represents the first example of the static synthesis of a glass without fusion in a silicate containing isolated tetrahedra. The electrical resistivity of initially crystalline Fe2SiO4 drops from approximately 2×105 ohm m at zero pressure to 10−3 ohm m at 79 GPa, with the pressure dependence of the resistivity decreasing at approximately the pressure of the coordination change (and amorphization). The electrical properties are quantitatively consistent with previous measurements, both under static and under shock wave loading. Optical transmission experiments demonstrate that in accord with the rapidly changing electron‐transport properties of Fe2SiO4, a strong absorption edge decreases in energy from the ultraviolet to infrared energies of about 3500 cm−1 (0.4 eV) on compression to 70 GPa. However, the reflectance of Fe2SiO4 is less than 3.1% between 780 and 2100 nm at all pressures to 225 GPa, indicating that amorphous fayalite does not metallize to at least this pressure. We interpret our resistivity and optical results in terms of increased interactions between iron ions with increasing pressure in Fe2SiO4 and an approach toward a Fe3++Fe1+ metallic configuration at high pressures. When combined with previous observations of amorphization at low temperatures and high pressures, our results suggest that transition to an amorphous phase is likely to be a general phenomenon in metastable silicates when the distortion of SiO4 tetrahedra becomes a major mechanism of compression.
Tomographic images of P wave velocity variation at Parkfield, California
Authors: Lees Jonathan M. , Malin Peter E.
Published: February 2008

Tomographie inversion is applied Io delay times from local earthquakes to image three dimensional velocity variations near Parkfield, California. The 25×20 square km region is represented by nearly cubic blocks of 0.5 km per side. Arrival times of P waves from 551 local earthquakes, with depths of 0 to 15 km, were used as sources producing 3135 rays covering the target region. The data were recorded on low‐noise downhole seismographs. A conjugate gradient method is used to invert the resulting sparse system of simultaneous equations. To diminish the effects of noisy data, the Laplacian of the model parameters is constrained to be small within horizontal layers, providing smoothing of the model. The resolution of the model is estimated by calculating point spread functions at blocks of interest. Estimates of standard errors of the model parameters are calculated by the jackknife statistical procedure. The results of the inversion show correlation with some of the local geological and geophysical features. Station corrections removed the long‐wavelength anomaly associated with the contrast of the Salinian block southwest of the San Andreas fault versus the Franciscan to the northeast. A velocity low located a few kilometers northwest of Parkfield (depth 2.5–3.5 km), appears to lie along the gradient of the large Bouguer gravity anomaly associated with the Parkfield syncline. The south‐southeastward extension of the low velocities may relate to reflections observed on the Parkfield, Consortium for Continental Reflection Profiling (COCORP) lines. We speculate on the geological meaning of these features and interpret them either as part of the local strike slip tectonics or a shallow crustal detachment. The correlation of higher‐velocity features and seismic activity may indicate that earthquakes are occurring in more competent zones while aseismic slip takes place in zones of lower‐velocity, less competent rocks.
Analysis of nuclear explosion salmon free‐field ground motion data for nonlinear attenuation
Authors: McCartor G. D. , Wortman W. R.
Published: February 2008

In order to assess the existence and impact of mild nonlinear contributions to the attenuation of seismic signals from underground explosions, free‐field motion data from underground 5.3‐kt nuclear test Salmon have been examined. These data, which were taken in a salt dome at ranges from 166 to 660 m, show moderate strains (10−3 to 10−4) which may provide nonlinear attenuation. The attenuation over an order of magnitude in peak amplitude can be described approximately by an attenuation function Q of a bit less than 10; however, the calculated waveform using this constant Q is noticeably wider than the data. A linear but frequency dependent Q which decreases with decreasing frequency gives a reasonable fit to much of the waveform change as well as the peak amplitude decay with range. The higher‐speed precursor which precedes the main pulse in the data cannot be described by this linear Q. With a spherical finite difference calculation driven by the 166‐m Salmon pulse, it is found that a rapid shear modulus decrease at a 10−4 strain threshold can reproduce the observed precursor and other features of the pulses at greater ranges when a linear broad absorption band with Q ≈ 10 is also added. The attenuation of the Salmon pulse thus can be attributed in part to a nonlinear effect of material failure as well as to a conventional linear mechanism. There are reasons to believe that the attenuation is not linear, but the Salmon data alone cannot verify this view.
Measurement of horizontal motions in Alaska using very long baseline interferometry
Authors: Ma C. , Sauber J. M. , Bell L. J. , Clark T. A. , Gordon D. , Himwich W. E. , Ryan J. W.
Published: February 2008

We have analyzed 6 years of very long baseline interferometry (VLBI) data beginning in 1984 from a network of sites in Alaska, the Yukon, and the conterminous United States. The analysis of these 53 data sets includes constrained, continuous, piecewise‐linear estimation of the site atmospheres and clocks; application of values and correlations from a self‐consistent Earth orientation series derived from other VLBI data; and simultaneous estimation of site positions and velocities. From a solution that includes 21,007 observations with a fit of 40 ps in delay and 64 fs/s in delay rate, we have determined the horizontal velocities of seven sites with precisions of 0.5–2 mm/yr (1σ standard deviation). The three VLBI sites within the Alaska‐Aleutian subduction boundary zone (Yakataga, Kodiak, and Sand Point) have higher instantaneous velocities relative to eastern North America than the interior sites of Alaska (Fairbanks and Sourdough). The estimated velocity of Yakataga relative to Fairbanks is 37.8±1.3 mm/yr at N27°W±2°. Modeling of the Yakataga data suggests that the observed motion is the result of elastic straining of the overriding plate due to a locked main thrust zone with a component of oblique slip. The estimated velocity of Kodiak relative to Fairbanks is 13.6±0.8 mm/yr at N41°W±3°; this result is lower than the rate predicted on the basis of simple elastic dislocation models. The estimated velocity of Sand Point relative to Fairbanks is 6.4±0.9 mm/yr at N65°W±8°. The component of this velocity in the plate direction, 3.5±1.1 mm/yr, is not consistent with either an aseismic slip model (i.e., no strain accumulation in the overriding plate) or a model in which the site is undergoing compressional strain (10.9 mm/yr at ∼N28°W) due to simple subduction at the predicted orientation of Pacific plate convergence. In a North America‐fixed reference frame, the estimated velocities of Fairbanks (1.5±0.5 mm/yr at S12°E±20°) and Sourdough (3.9±1.0 mm/yr at S13°W±13°) are both southward. These results may imply motion of this region relative to stable North America, but more observations are required to reduce the uncertainties in the azimuths. The time evolution of the estimated site positions from VLBI in Alaska are, in general, consistent with constant velocity. However, in 1988 the Yakataga site showed a significant departure from the position predicted from a constant‐velocity model obtained from the previously estimated position. This departure may be static displacement associated with two major strike‐slip earthquakes that occurred in the Gulf of Alaska between the 1987 and 1988 measurement sessions.
The latitudinal and vertical distribution of molecular hydrogen in the troposphere
Authors: Schmidt U.
Published: February 2008

Meridional profiles of the H2 mixing ratio in surface air were obtained by continuous registrations during a ship cruise from Hamburg, West Germany, to Santo Domingo, Dominican Republic, in 1973. Vertical and meridional profiles in the troposphere were measured during a research flight from Cologne, West Germany, to Punta Arenas, Chile, in 1974. The average H2 mixing ratio of surface air was 0.582 ± 0.003 ppmv (parts per million by volume) in the northern hemisphere. In the upper troposphere it was found to be 0.561 ± 0.001 ppmv, 1.3% higher than the average of 0.554 ± 0.002 ppmv in the upper troposphere of the southern hemisphere. The horizontal distribution appears to be rather uniform. The vertical profiles also exhibited a rather uniform distribution of H2. However, vertical gradients near the ground were occasionally observed. They are ascribed to strong sources and sinks at the surface. The H2 mixing ratio in the lower stratosphere appeared to be slightly higher than that in the troposphere.
On the California undercurrent over the continental slope off Oregon
Authors: Halpern David , Smith Robert L. , Reed Ronald K.
Published: February 2008

During July 1975, moored current measurements and a spatially dense approximately isochronal hydrographic survey were made off Oregon. The patterns of geopotential topography, the longshore and onshore‐offshore variations in temperature and salinity, and the current measurements indicated a poleward flow of warmer, more saline water at intermediate depths over the continental slope throughout a longshore distance of about 600 km. The agreement between linear approximations of the north‐south velocity shears determined from baroclinic geostrophic currents and from 3‐day vector‐averaged current measurements was within 3%. The current measurements at intermediate depths indicated a wavelike oscillation, lateral meander, or eddy with a time scale of about 7–10 days, and the surface pattern of the geopotential topography (referred to 1000 dbar) contained eddies or a wavelike feature with a wavelength of about 200 km. Comparison of the time variations of currents recorded simultaneously over the slope and shelf indicated that the subsurface poleward flows observed there were connected.
Variations in the alongshore correlation of sea level along the West Coast of North America
Authors: Osmer Stephen R. , Huyer Adriana
Published: February 2008

We investigated sea level fluctuations at seven locations from San Francisco to Tofino, British Columbia, during a 2‐year period beginning in August 1973. Using overlapping 2‐month periods, we found the alongshore correlation to vary with time and with location along the coast. In winter the fluctuations are correlated along the entire coast from San Francisco to Tofino; at intermediate locations the correlation is higher with Tofino than with San Francisco. In summer, sea level variations at San Francisco and Crescent City are not correlated with those farther north; there is still high alongshore correlation among the stations to the north and also between Crescent City and San Francisco. In all seasons the sea level fluctuations propagate northward, although variations in the wind stress propagate southward. At each location the sea level is usually also correlated with the local wind stress, the wind stress leading by about a day.
Some evidence for boundary mixing in the deep Ocean
Authors: Armi Laurence
Published: February 2008

Profiles of salinity and potential temperature in the deep ocean are presented which suggest the characteristic signature of two complementary mixing processes: vertical mixing within ∼50‐m‐thick layers at boundaries and topographic features and lateral advection and eventual smearing of these mixed layers along iopycnal surfaces. The combined effect of these two processes is often parametrically disguised as a vertical eddy diffusivity in one‐dimensional models. An estimate shows that the two processes can account for all the vertical mixing in the deep ocean without any vertical diffusion in the interior.
Winter season temperature outlooks by objective methods
Authors: Harnack R. P. , Landsberg H. E.
Published: February 2008

An attempt was made to predict categories of cold season temperature for 19 cities in the central and eastern United States. Classification equations were developed by using discriminant analysis based on 23 years of historical data (1949–1971) in which the discriminating variables (predictors) are principal components of the mean 700‐mbar heights during November over the northern hemisphere; sea surface temperatures of the eastern North Pacific, eastern tropical Pacific, and North Atlantic oceans; and a southern oscillation index for the fall season. Separate sets of equations were developed for varying duration of the prediction, from 1 to 4 months, and for two or three categories of mean temperature. An independent sample of years was reserved for testing the reliability of the equations. ‘Forecasts’ made by each set of equations were compared with observed categories of mean temperature for five recent winters (1972–1976), not included in the dependent sample. The sets of equations derived for discriminating between above‐ and below‐normal mean temperatures for the 4‐month season (December‐March) and between three groups for the 3‐month winter season (December‐February) performed significantly better than chance expectation. Values of 63% and 45%, respectively, were correct. Additionally, when the persistence forecast category was the same as the forecast category of our model for the December‐March period in the two‐group discrimination, the prediction category was correct 86% of the time over the five test winters. This situation occurred, on the average, for about half the cities in each year. These results indicate that objective methods, using statistical relationships, can be useful for winter temperature predictions, but considerable improvement is still needed.
Accurate solar ‘constant’ determinations by cavity pyrheliometers
Authors: Willson Richard C.
Published: February 2008

Total solar irradiance was observed outside the earth's atmosphere by three types of absolute cavity pyrheliometer in a June 1976 sounding rocket experiment. The 1367 W/m2 average solar ‘constant’ result is uncertain by less than ±0.5%, the most accurate determination to date. Nearly simultaneous observations by the Nimbus 6 earth radiation budget total irradiance detector of 1389 W/m2 exceeded the rocket result by 1.6%. These recent results are discussed in the context of a summary of solar constant determinations made above the troposphere by cavity pyrheliometers.
Large‐scale Gulf Stream frontal study using Geos 3 radar altimeter data
Authors: Huang Norden E. , Leitao Clifford D. , Parra Carlos G.
Published: February 2008

From data obtained by the Geos 3 radar altimeter, sea surface heights are found by both editing and filtering the raw sea surface height measurements and then referencing these processed data to a 5′ × 5′ geoid. Any trend between the processed data and the geoid is removed by subtracting out a linear fit to the residuals in the open ocean. Data from individual passes are further processed by applying a minimum variance technique at the subsatellite crossing points to produce surface topography maps for the 6 months and an overall mean map which reveal important details about the Gulf Stream system. The differences between the monthly mean and the overall mean are calculated for each of the 6 months to show the temporal and spatial changes of the Gulf Stream front and spawned eddies. The standard deviation map is even more informative and shows preferred locations of Gulf Stream meanders.
Fronts and wave disturbances in Gulf Stream and atmospheric jet stream
Authors: Newton Chester W.
Published: February 2008

Similarities in their basic features, including spatial variations of frontal structure along the current, suggest that Gulf Stream meanders are dynamically analogous to atmospheric jet stream waves, with descending motions upstream and ascending motions downstream from a wave trough. In a symmetrical wave with uniform speed along the current it is shown that confluence, together with the distribution of vertical motions, accounts for the greater baroclinity in the frontal zone at troughs than at crests, a necessary feature of such a wave. Gross features of the three‐dimensional motions are discussed for an eddy in the process of cutting off to form a Gulf Stream ring. Prior to its detachment from the slope water mass, deduced sinking motions exceed, by 2 orders of magnitude, the vertical motions in ring eddies that have become isolated. The large downward volume flux during the formative stage is associated with the asymmetrical structure (more water pouring into a cold tongue on its west side than leaves it on its east side) and with the vertical distribution of volume transport (greater inflow than can be accommodated by horizontal expansion in the upper layers). The inflation time for a Gulf Stream ring is about a month, much shorter than the decay time.
Investigations on snow parameters by radiometry in the 3‐ to 60‐mm wavelength region
Authors: Hofer R. , Mätzler C.
Published: February 2008

We report on a 2‐year period of monitoring parameters of a natural snowpack by ground‐based microwave radiometry on a high‐altitude Alpine test site. The microwave brightness temperatures are compared to a large set of ground‐truth data. Three stages in the seasonal development of the snow cover are easily distinguishable which allow the prediction of the beginning of the snow melting. The moisture content of the melting surface layer is estimated by the aid of the typical daily variations of microwave brightness temperatures in spring. The test site was composed of two snow fields. The first one was lying on slightly reflecting soil, and the second one was lying on a completely reflecting metal foil. By measuring on both fields some microwave snow parameters can be determined. The damping coefficients for microwaves between 5 and 100 GHz were estimated by comparing the results of two extreme theories. Both theories gave results from less than 1 dB/m to more than 30 dB/m depending on the snow state, especially its liquid water content.
Do Sverdrup transports account for the Pacific North Equatorial Countercurrent?
Authors: Meyers Gary
Published: February 2008

Poleward and equatorward geostrophic transports calculated from density are nearly equal to Sverdrup transports calculated from the curl of the wind stress in the North and South Pacific subtropical gyres. But the Sverdrup transports do not account for the Pacific North Equatorial Countercurrent.
Wave setup of harbor water levels
Authors: Thompson Rory O. R. Y. , Hamon Bruce V.
Published: February 2008

Radiation stress by incoming sea surface waves or swell can raise the mean level of water in a harbor by an amount independent of the size of the harbor. This setup can be a significant confounding factor in determining sea level changes, if the sea level gauge is inside a harbor with a moderately shallow entrance. The mechanism is independent of ‘inverse barometer’ or wind setup effects, though it is likely to enhance them.
The Batchelor spectrum and dissipation in the upper ocean
Authors: Dillon Thomas M. , Caldwell Douglas R.
Published: February 2008

Observations of vertical temperature microstructure at ocean station P during the mixed layer experiment (Mile) indicate that the shape of the high‐frequency temperature gradient spectrum depends on the relative strengths of turbulence and stratification. For low Cox number 〈(dT/dz)2〉/〈dT/dz〉2 the linear range of the Batchelor spectrum is not well approximated by observed spectra, while for high Cox number a remarkably close correspondence to the Batchelor spectrum is found. Dissipation rates calculated by the temperature gradient spectrum cutoff wave number method show a dramatic contrast in turbulence between low and high wind speed periods separated by only 3 hours, showing that the response of the mixed layer and transition zone to wind forcing is rapid. Some indication is found that the thermocline may also respond rapidly to surface forcing.
14C distribution in the Atlantic Ocean
Authors: Stuiver Minze
Published: February 2008

The amount of 14C produced by nuclear bomb testing that entered the Atlantic Ocean by late 1972 was 1.71×10−8 μmol/cm2 of ocean surface area for the west Atlantic (36°S–45°N) and 1.18×10−8 μmol/cm2 for the east Atlantic (50°S–28°N) Geochemical Ocean Sections Study stations. There are strong latitudinal differences in the integrated amount of bomb 14C content in Atlantic waters. Bomb‐produced 14C is mostly encountered near the center of the large mid‐latitude gyres, whereas the equatorial region has a lower 14C inventory. The average ocean wide vertical distribution of bomb 14C in the Atlantic can be explained by a vertical eddy diffusion coefficient of 4.0 cm2/s in the surface mixed layer plus thermocline gyre reservoirs. The average 14C activity per unit area measured in the Atlantic yields an CO2 exchange rate of 23 mol/m2 yr, which is equivalent with an atmospheric CO2 residence time of 6.8 years.
Radar observation and model computation of a jet stream‐generated Kelvin‐Helmholtz instability
Authors: Klostermeyer J. , Rüster R.
Published: February 2008

During the passage of a polar front jet stream, one wind component and the radar echo power were recorded by the SOUSY VHF radar located in the Harz Mountains in Germany. The measurements were performed in the troposphere with height and time resolutions of 150 m arid 10 s, respectively. In the lower shear region of the jet stream a Kelvin‐Helmholtz instability (KHI) occurred with a period near 4 min and velocity amplitudes of the order of l m s−1. During the growth stage of the KHI the echo power increased significantly and remained strong even after the KHI had disappeared. It is concluded that a 3‐m turbulence structure which produced the enhanced echo power is part of a broad spectrum of instabilities which started with the generation of the 4‐min KHI. The properties of the observed KHI are compared with those of the fastest growing instability computed from a linear operational model taking into account vertical profiles of the mean wind and temperature which were obtained from the radar and a radiosonde ascent. The computed frequency, growth rate, and velocity profile show excellent qualitative and, partly, even quantitative agreement with the observational results.
Geometric properties of the underside of sea ice
Authors: Rothrock D. A. , Thorndike A. S.
Published: February 2008

Profiles of the underside of sea ice are rough and disorderly. No natural definition of the roughness elements is found; they have all sizes and shapes. This raises questions concerning the practice of identifying and counting pressure ridge keels. The profiles can be characterized by their power spectral density functions. It is found that the spectra vary approximately as (wave number)−3 at high wave numbers. This observation is related to other measures of roughness, including continuity, differentiability, and the fractal or Hausdorff dimension, and to the distribution of the drafts of local maxima. The latter is seen to correspond closely with the ice thickness distribution.
Circulation in the Peruvian upwelling system near 15°S
Authors: Brink K. H. , Halpern D. , Smith R. L.
Published: February 2008

During the March‐May 1977 phase of the Coastal Upwelling Ecosystems Analysis Joint II experiment, an intensive array of current meters, tide gauges, and meteorological sensors was deployed over the Peruvian continental shelf and slope near 15°S. The low‐pass‐filtered (frequency <0.51 cpd) local winds were equatorward (upwelling favorable) throughout the study period, and conditions in the upper 100 m over the shelf indicated an active upwelling circulation. Upwelling events (with time scales 2–10 days) showed clearly in the onshore velocity and temperature records but poorly in the alongshore velocity. Baroclinic, quasi‐geostrophic free coastal trapped waves dominated the alongshore velocity records, and their dynamics are investigated with the help of empirical orthogonal functions and other techniques. The offshore Ekman flux computed from the mean alongshore wind stress of 0.76 dyne cm−2 near the coast was more than twice as large as that computed from near‐surface current measurements at midshelf but 27% smaller than the observed mean onshore flow at the same location. The fluctuating mass and momentum balances were also strongly three dimensional. The alongshore velocity component tended to be geostrophically balanced. Turbulent effects were important both near the surface and near the bottom over the shelf, where estimated eddy viscosities in the boundary layers were typically in the range of 40–60 cm2 s−1. The three dimensionality of the circulation probably reflects the complexity of the local wind driving and of the bottom topography. Appendix tables are available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document J‐80‐008; $1.00. Payment must accompany order.
Sulfur and associated elements and acidity in continental and marine rain from north Florida
Authors: Tanaka Shigeru , Darzi Michael , Winchester John W.
Published: February 2008

Rainwater was sampled for every rainfall occurrence between November 7, 1978, and January 26, 1979, in Tallahassee, Florida, a generally unpolluted area in the southeastern United States, about 50 km north of the Gulf of Mexico. The elemental composition was determined for 12 elements, S, K, Ca, V, Mn, Fe, Ni, Cu, Zn, Br, Sr, and Pb, by proton‐induced X ray emission from 4 ml aliquots of 38 different rain samples. The elemental composition of the rain was found to be different for rain associated with northerly and southerly air flow regimes. In north air flow rain, originating from more polluted northern areas, concentrations of Pb, S, and Fe were higher and strong correlations of Br, Ca, and Fe with Pb were observed. Thus the north air flow rain exhibits polluted and continental characteristics. On the other hand, most elemental concentrations were lower in south air flow rain originating in the Gulf of Mexico, and strong correlations between elements such as S, K, Ca, and Br, but not with Pb, were observed. These results indicated a strong influence by sea spray. The north and south air flow rains also differed significantly in their acidity. In northern rain the average pH was 4.4 with a minimum of 3.7, whereas in southern rain the average pH was 5.3 with a minimum of 4.6. A strong correlation between pH and logarithmic sulfur concentration was observed in northern rain but not in southern rain. This suggests that most of the sulfur in northern rain is sulfuric acid transported from pollution sources, whereas southern rain includes much neutralized seawater sulfate.