bluuebunny/crossref_metadata_2025 huggingface dataset:
Intercomparison tests of moored current measurements in the upper ocean
Authors: Halpern David , Weller Robert A. , Briscoe Melbourne G. , Davis Russ E. , McCullough James R.
Published: February 2008

During the August‐September 1977 Mixed Layer Experiment (Mile) and the July‐September 1978 Joint Air‐Sea Interaction (Jasin) project, moored current measurements were made in the upper ocean with Savonius rotor and vane vector‐averaging current meters (VACM), dual orthogonal propeller vector‐measuring current meters (VMCM), and dual orthogonal acoustic travel‐time vector‐averaging current meters (ACM). Wind speeds and significant wave heights reached 20ms−1 and 5 m. The influence of mooring motion upon ACM, VACM, and VMCM measurements are described. In the mixed layer above about 30 m depth where mean currents are relatively large, the effect of a surface‐following buoy upon ACM, VACM, and VMCM velocity fluctuations at frequencies less than 0.3 cph was negligible; at frequencies above 4 cph, the VACM data contained the largest amount of mooring induced contamination. Below the mixed layer at depths greater than about 75 m, a subsurface mooring should be used; however, when a surface‐following buoy was used, then VMCM data better approximated the spectrum of the fluctuations than VACM data. A spar‐buoy should not be used to measure currents at depths as deep as 80 m. The frequency‐dependent differences between VACM and VMCM and between VACM and ACM measurements are described. At frequencies less than 0.3 cph, the differences between the VACM and ACM or the VMCM records were not significant with 95% confidence limits, were always positive, and above 80 m depth were less than 20%. At frequencies above 4 cph, the VACM‐VMCM differences were about 5 times larger than the VACM‐ACM differences.
Effects of meteoric debris on stratospheric aerosols and gases
Authors: Turco R. P. , Toon O. B. , Hamill P. , Whitten R. C.
Published: February 2008

We consider the interactions of meteoric dust particles and metal vapors with stratospheric aerosols and gases. We utilize the detailed calculations of meteor ablation and recondensation rates made by Hunten et al. (1980) to obtain a fairly precise characterization of meteoric dust height and size distributions. We quantify the contribution of meteor residues to aerosol composition, the role of meteoric dust as condensation nuclei, and the effects of meteor debris on aerosol size distributions. We give estimates of particle surface areas, and discuss the potential importance of heterogeneous chemistry for stratospheric trace gases. We also investigate the interaction between H2SO4 vapor, which is associated with stratospheric aerosols, and meteor metal vapors, which are responsible for stratospheric metal ion composition. Our model predictions compare favorably with observational data on the elemental composition of aerosols, stratospheric particle size distributions, condensation nuclei abundances and sulfate mass mixing ratios. We conclude that meteoric particles may dominate the natural stratospheric aerosols at small (<0.01μm radius) and large (>1.0 μm) sizes under normal conditions. We show that metallic meteoric elements may act to neutralize sulfuric acid vapor above 20 km, significantly reducing ambient H2SO4 abundances. We also demonstrate that model calculations which neglect particle interactions can seriously overestimate stratospheric metal vapor concentrations.
Seawater and nonseawater aerosol components in the marine atmosphere of Samoa
Authors: Maenhaut Willy , Darzi Michael , Winchester John W.
Published: February 2008

Two multi‐element aerosol components and a third fine particle sulfur component have been identified in the marine atmosphere of Samoa based on elemental composition, time variation, and particle size distribution characteristics. On the basis of Pixe (proton induced X ray emission) analyses of 34 cascade impactor samples (17 simultaneous pairs), each of six particle size fractions, collected at 50 m height, July 16 to September 20, 1976, the components are (1) Cl, Br, K, and Sr in >0.5 μm aerodynamic diameter particles, Ca in 0.5–4 μm particles, and S in >1 μm particles, in proportions resembling, but not identical to, seawater composition; (2) a nonseawater component in >4 μm particles, consisting of 80% of the Ca and median weight ratios for excess Ca/Zn = 3.4, Cu/Zn = 0.11, Ti/Pb = 1.0, Ti/Zn = 0.06, and Fe/Zn = 0.24; (3) S in <1 μm particles with a geometric mean concentration of 63(1.15) ng/m3, comparable to coarse mode S concentrations and similar to values found elsewhere in the southern hemisphere. A wind speed bias against sampling >4 μm particles during prevailing 1–15 m/s winds was evaluated for K, Cl, and S, indicating zero wind speed >4 μm concentrations for component (1) to be on the average 2.0 times greater than measured. Differences in processes for transfer of the elements through the sea surface to jet and film drops may account for the observations.
7Be in Sargasso Sea and Long Island Sound waters
Authors: Aaboe Erik , Dion Eric P. , Turekian Karl K.
Published: February 2008

7Be was measured in surface waters of the western Sargasso Sea and Long Island Sound. The calculated standing crop in the Sargasso Sea is equal to that predicted from precipitation collectors. Long Island Sound is deficient in 7Be; virtually none exists in the water column, and less than half of the expected standing crop has been reported for the sediments. A possible sink for the missing 7Be may be the salt marshes or tidal mud flats ringing Long Island Sound.
An investigation of gravity waves on a global scale using TWERLE data
Authors: Massman William J.
Published: February 2008

The results of a hemispheric experiment to investigate gravity waves with intrinsic periods between 0.5 and 3 hours are presented. Over 200 wave observations were made by using the vertical oscillations of drifting constant‐volume balloons gathered with a pressure sensor, a temperature sensor, and an altimeter. Since these wave observations are 38% of the total sample, the results indicate that these waves are ubiquitous. All observations are made at nearly the same level in the atmosphere (140–170 mbar); at low latitudes the observations are in the tropical upper troposphere and at mid‐ and high latitudes they are in the lower stratosphere. The observed intrinsic frequency, the average amplitudes of the atmospheric pressure perturbation and vertical velocity, the vertical fluxes of wave energy and horizontal momentum, the total wave energy density, the vertical group velocity of the wave, and the wave action density are shown. The distributions of the average amplitudes show a few very large values for both regions. The distributions of vertical energy flux and vertical group velocity indicate that the dominant wave in the lower stratosphere of the mid‐ and high latitude is an evanescent or trapped wave, while in the upper tropical troposphere upward propagating, untrapped internal waves dominate. The distributions of wave action density are very similar for the two regions, while the distributions of intrinsic frequency, total wave energy density, and vertical flux of horizontal momentum are different for the two regions. The balloonborne observing system proved to be extremely good; however, the experimental system could be improved by making in situ measurements of the lapse rate and horizontal wind shear and by including a horizontal accelerometer. Such a completely instrumented system could prove to be very useful in determining how these waves influence the mean flow on a global scale.
Shelf break circulation in the northern Gulf of Alaska
Authors: Niebauer H. J. , Roberts J. , Royer T. C.
Published: February 2008

Current observations from a mooring on the continental shelf near the shelf break in the Gulf of Alaska, with supporting hydrographic and meteorological data, are discussed for the period 1976 to March 1977. The described features suggest strong influence by the cyclonic Alaska Gyre for the periods April–June 1976 and October 1976 to March 1977. From July–September 1976 there is evidence of current veering and rotation. It is hypothesized that these current fluctuations are eddies which are important in mixing processes across the shelf.
Atmospheric measurements of CF4 and other fluorocarbons containing the CF3 grouping
Authors: Penkett S. A. , Prosser N. J. D. , Rasmussen R. A. , Khalil M. A. K.
Published: February 2008

Careful measurements by GC/MS techniques on atmospheric carbon tetrafluoride confirm that its concentration in 1979 was constant at about 69.9 pptv (standard deviation is 7.2 pptv). It is almost certainly produced entirely by emissions from the aluminium industry. Other compounds in the atmosphere containing the CF3 group have been identified by GC/MS as C2F6, CF3Cl, CF3Br, and C2F5Cl. The concentrations of the first pair are about 4 pptv, and the latter two are about 0.7 pptv and 4 pptv, respectively. The C2F6 is produced simultaneously with CF4 in the manufacture of aluminium. CF3Cl, CF3Br, and C2F5Cl are probably produced by the chemical industry. The environmental importance of these compounds is discussed in the context of two papers on CF4 recently published by Cicerone (1979) and by Wang et al. (1980).
The photodissociation of water vapor in the mesosphere
Authors: Nicolet Marcel
Published: February 2008

An analysis of the photodissociation of water vapor has been made for mesospheric conditions. The simultaneous action of two spectral ranges, namely the Lyman‐alpha radiation and the O2 Schumann‐Runge bands, must be considered. The H2O photodissociation frequency owing to Lyman‐alpha is represented by J(H2O, Ly‐α) = J∞ exp [−4.17 × 10−19N0.917], where N is the total number of O2 absorbing molecules, and J∞ = (3.5 ± 1.0) × 10−6 s−1 for quiet sun conditions and reaches (1.25 ± 0.35) × 10−5 s−1 for very active sun conditions. The H2O photodissociation frequency resulting from the O2 Schumann‐Runge band spectral range is represented by J(H2O, SRB) = J∞(H2O, SRB) exp [−4.8 × 10−10N0.466] for N ≤ 1020 cm−2, and J(H2O, SRB) = J∞(H2O, SRB) exp [−4.6 × 10−8N0.366] for 1020 < N ≤ 1022 cm−2. The mean value which has been adopted for J∞(H2O, SRB) = (1.3 ± 0.3) × 10−6 s−1 while a median value could be (1 ± 0.5) × 10−6 s−1 based on all observational data.
Comparison between measured and computed concentrations of sulphur compounds in eastern North America
Authors: Voldner E. C. , Olson M. P. , Oikawa K. , Loiselle M.
Published: February 2008

A concentration/deposition model has been developed for application to the Long‐Range Transport of Air Pollutants (LRTAP) program within the Canadian Department of the Environment. The Lagrangian model computes concentration and deposition fields of sulphur compounds as well as precipitation pH over North America. Four‐day, backward trajectories are computed from three‐dimensional objectively analyzed windfields, which are available 4 times a day. The pollutants are assumed well mixed throughout the mixing layer. The mixing height varies diurnally and seasonally according to mixing height climatologies. Precipitation data are obtained from 24 hour objective analyses and SO2 source emissions from a North American emission's inventory. Wet and dry deposition and chemical transformation processes are parameterized. Model predicted air and precipitation sulphate concentrations have been compared with those measurements by different monitoring networks in eastern North America. The agreement between measured and computed quantities is generally good. The occurrences of air pollution episodes are duplicated in space and time. Average computed and measured concentration/deposition fields are generally within 60%. The paper gives a description of the model, shows its sensitivity to changes in values of key parameters, and gives results from a comparison study in 1977. Further, some problems encountered when using actual measured data for model comparison are discussed.
The determination of tropospheric nitrous oxide
Authors: Weiss R. F. , Keeling C. D. , Craig H.
Published: February 2008

A two‐step technique, in which the N2O/CO2 ratio is measured by ultrasonic phase‐shift gas chromatography and the dry air CO2 concentration is measured by nondispersive infrared analysis, has been developed for the determination of the mole fraction of nitrous oxide in dry air. The N2O concentration is given by the product of these two independent measurements and has a precision (±1 standard deviation) ranging between 0.3 and 0.5%. The absence of systematic errors has been verified by extensive standard intercomparisons and by independent cross checks of the sample extraction procedures. The results of extensive measurements by this technique, reported in a companion paper, fix the mean tropospheric dry air mole fraction of nitrous oxide in the northern hemisphere as of January 1, 1978 at 300.2±0.6 parts per billion, including systematic uncertainties.
Estimating the ozone budget in the boundary layer by use of aircraft measurements of ozone eddy flux and mean concentration
Authors: Lenschow D. H. , Pearson R. , Stankov B. B.
Published: February 2008

A fast response chemiluminescent ozone sensor was mounted in a National Center for Atmospheric Research Queen Air aircraft instrumented for air motion, temperature, and humidity measurements. The vertical flux of ozone was then obtained by the eddy correlation technique for several flights in the day‐time atmospheric boundary layer over eastern Colorado. Because of the range and mobility of the aircraft, this technique can be utilized for a wide variety of situations. For example, a flight leg over an interstate highway shows large negative fluctuations in O3 due to vehicular emission of NO that are well correlated with positive temperature and vertical velocity fluctuations. On one flight the significant terms in the mean ozone concentration budget (and also, for comparison, the sensible heat and humidity budgets) were evaluated from the airplane measurements. For this flight, which occurred under clear skies over range and cropland about 100 km northeast of Denver, the time rate of change of ozone density in the lower half of the boundary layer was about 2.4 ng m−3 s−1. This was several times larger than the contributions by horizontal advection and the divergence of the vertical eddy flux of ozone. Thus, most of the observed increase in ozone concentration must have been the result of internal photochemical production of ozone. This may be the first well‐documented example where the rate of O3 increase with time is shown to be balanced by photochemical production of O3. The deposition velocity of ozone for this case was about 0.47 cm s−1.
Monthly and seasonal variability in the ocean‐ice‐atmosphere systems of the North Pacific and the North Atlantic
Authors: Walsh John E. , Sater John E.
Published: February 2008

Four regional indices of sea ice variability and thirty years of monthly sea surface temperature (SST) and sea level pressure (SLP) data are used to evaluate the large‐scale interactions within the ocean‐ice‐atmosphere systems of the North Pacific and the North Atlantic. A direct association between positive (negative) SST anomalies and light (heavy) ice in the Bering Sea is indicated. The SST/ice coupling in the northern Alaskan waters is also statistically significant. The SST anomalies in both the North Pacific and the North Atlantic appear as persistent responses to atmospheric forcing. The SLP distributions over both oceans correlate significantly with the arctic SLP distribution, although the midlatitude atmospheric circulation shows no systematic tendency to lead or lag the arctic circulation. Sea ice fluctuations correlate most highly with the atmospheric forcing over antecedent periods of approximately 9 months in the northern Alaskan waters, 3–4 months in the Bering Sea, and 5–7 months in the East Greenland Sea. The strength of the 9‐month mean onshore air flow component describes over 70% of the northern Alaskan ice variance.
Circulation of the Caribbean Sea: A well‐resolved inverse problem
Authors: Roemmich Dean
Published: February 2008

The Caribbean Sea is selected as a region where the large‐scale circulation is well determined by historical hydrographic measurements through application of the inverse method. A simple example is used to illustrate the technique and to demonstrate how some physically relevant quantities may be well determined in the formally underdetermined inverse problem. The geostrophic flow field in the Caribbean is found by imposing mass and salt conservation constraints in seven layers separated by surfaces of constant potential density. An unsmoothed solution is displayed that has weak dependence on an initial choice of reference level. In addition, a unique smoothed solution is shown. Above σθ = 27.4, the total flow leaving the western Caribbean is estimated to be 29 × 106 m3 s−1, in agreement with direct measurements. This flow is made up of 22 × 106 m3 s−1 entering the Caribbean from the east and flowing across the southern half of the basin as the Caribbean Current, and 7 × 106 m3 s−1 entering from the north through Windward Passage. Both of these currents show small‐scale variability that diminishes with distance from the respective passages. The deep flow has no net transport, as required by the shallow exit, but a well organized clockwise recirculation is found in the deep eastern Caribbean.
Modeling of anisotropic electromagnetic reflection from sea ice
Authors: Golden K. M. , Ackley S. F.
Published: February 2008

The contribution of brine layers to observed reflective anisotropy of sea ice at 100 MHz is quantitatively assessed, and a theoretical explanation for observed reflective anisotropy is proposed in terms of anisotropic electric flux penetration into the brine layers. The sea ice is assumed to be a stratified dielectric consisting of pure ice containing ellipsoidal conducting inclusions (brine layers) uniformly aligned with their long axes perpendicular to the preferred crystallographic c axis direction. The asymmetrical geometry of the brine layers is shown to produce an anisotropy in the complex dielectric constant of sea ice. The contribution of these layers to the reflective anisotropy is examined with a numerical method of approximating the reflected power of a radar pulse incident on a slab of sea ice. Mixture dielectric permittivities are calculated for both the electric fields parallel and perpendicular to the c axis direction. These permittivities are then used to calculate power reflection coefficients at each interface in the air/sea ice/sea water system. Significant bottom reflection (R≈0.09) occurs when the polarization is parallel to the c axis. However, when the polarization is perpendicular to the c axis, the return is almost completely extinguished (R<0.003). This extinction is due primarily to absorptive loss associated with the conducting inclusions and secondarily to an impedance match at the ice/water interface that results in transmission rather than reflection of the wave.
Determination of vertical profiles of aerosol size spectra from aircraft radiative flux measurements: 2. The effect of particle nonsphericity
Authors: Welch R. M. , Cox S. K. , Kondratyev K. Ya.
Published: February 2008

The effect of particle nonsphericity upon the retrieval of panicle size distributions, computed from aircraft radiative flux measurements, has been examined for the data of September 4, 1974. The particle inversion procedure is identical to that described by Kondratyev et al. (1981), involving quadramodal particle size spectra. Nonspherical particle attenuation coefficients and phase functions were calculated according to the semi‐empirical approach developed by Pollack and Cuzzi. It was found that variations of the phase function by nonspherical panicles affected the retrieval of particle size spectra to a far greater degree than did variations of panicle scattering efficiency. Nonspherical panicles generally have smaller values of asymmetry factor than do their spherical counterparts. The inferred size spectra of nonspherical panicles show decreased values both of large and small panicle number densities along with a broadening of the large particle mode to include particles of larger sizes.
Turbidity of the atmosphere determined from satellite: Calculation of optimum wavelength
Authors: Koepke Peter , Quenzel Heinrich
Published: February 2008

With the object of determining the atmospheric turbidity (aerosol optical depth) from upward emerging spectral radiances, an evaluation was made of that wavelength at which the variability of the radiance owing to the variability of the turbidity predominates the variability caused by the perturbing optical parameters. This has been done by numerical modeling of the variability of the radiances owing to the variability of all optically acting atmospheric constituents (no clouds) and the underlying rough ocean for maritime aerosols and Saharan dust. It is found that the optimum wavelengths are 0.75 and 0.87 μm. In addition, it has been found that low sun and low observation elevation angles are preferable.
The annual variation of atmospheric CO2 concentration observed in the northern hemisphere
Authors: Pearman G. I. , Hyson P.
Published: February 2008

Records of the annual variation of the atmospheric carbon dioxide concentration at Mauna Loa, Point Barrow, and Weathership P are examined for secular changes. The amplitude of the annual variation appears to have increased in recent years with a best estimate of the rate of change, based on the Mauna Loa data, of 0.45±0.42% yr−1. This change is discussed in terms of changes in biospheric respiration and photosynthesis and the use of fossil fuels. The analysis does not allow for the separation of several possible causes of amplitude change. However, if the change is interpreted as reflecting enhanced biospheric growth, the effect is equivalent to a 8% change in the net summer uptake of carbon over the years 1959–1978 and to a growth of the northern hemisphere seasonal biosphere of 0.5×1012 kg of carbon per year. Such a conclusion is consistent with recent inventory studies, which indicate that temperate zone forests have acted as a net sink of about 1012 kg of carbon per year in recent decades.
Vertical turbulence diffusivity for weak or strong stable stratification
Authors: Weinstock J.
Published: February 2008

A theoretical relation is derived for the vertical turbulent diffusivity Kzz in weak as well as strong stable stratification. This relation expresses Kzz in terms of the buoyancy frequency (Brunt‐Väisälä frequency), the energy dissipation rate ε, and the characteristic energy‐containing wave number k0. A previous relation was limited to strong stable stratification.
A comparison of near‐surface CODAR and VACM measurements in the Strait of Juan De Fuca, August 1978
Authors: Holbrook J. R. , Frisch A. S.
Published: February 2008

Three days of simultaneous near‐surface current measurements made by Coastal Ocean Dynamics Applications Radar (CODAR) and surface‐moored Vector‐Averaging Current Meters (VACM) in the Strait of Juan de Fuca are compared. The study focuses on the mean flow and tidal components that contained approximately 79% of the kinetic energy. The mean speed and direction differences were less than 7 cm/s and 10°, respectively. The K1 and M2 tidal constituents agreed to within 14 cm/s with a mean difference of 5.2 cm/s. This study demonstrates that CODAR yields estimates of the near‐surface currents that are comparable with conventional VACM arrays to 10–15 cm/s.
Ocean mesoscale variability from repeat tracks of Geos‐3 altimeter data
Authors: Douglas Bruce C. , Cheney Robert E.
Published: February 2008

The Geos‐3 satellite altimeter observed numerous sea surface profiles along nearly repeated tracks in the western North Atlantic during its 3.5‐year lifetime, enabling observation of the variation of sea surface topography along these tracks. Analysis of 14 north‐going and 13 south‐going sets of repeated tracks has yielded the variability of the surface at a resolution of 1° from 25° to 41°N latitude and from 60° to 80°W longitude. The observed rms variation of surface topography ranges from about 8 cm in the Sargasso Sea to a maximum of 48 cm in the Gulf Stream meander region, in agreement with known mesoscale energetics of this region.
Vertical fine structure observations in the eastern equatorial Pacific
Authors: Hayes S. P.
Published: February 2008

Measurements of vertical displacement and horizontal velocity finestructure near the equator at 110°W in the eastern Pacific Ocean are reported. Profiles were scaled to a constant Brünt‐Väisälä frequency ocean (No = 1 cph) in accordance with a WKBJ approximation. A total of 57 CTD casts between 3°N and 3°S taken during five cruises in 1979 were analyzed. Results show an equatorial enhancement of vertical displacement variance for vertical wavelengths longer than 50 sdbar (stretched decibars). This enhancement is similar to that which has been reported at 125°W and 179°E. Differences between locations can be accounted for by the observed temporal variability at 110°W. Coherence between vertical displacement profiles separated in time by delays of 2 hour to 120 hour indicate that the high wave number structures were largely associated with time scales of 4 days and less. Meridionally, vertical structures longer than 300 sdbar were coherent within 50 km of the equator. We interpret this vertical displacement fine structure enhancement as high wave number equatorially trapped inertial‐gravity waves. The velocity fine structure measurements in July 1979 also indicate equatorially enhanced horizontal kinetic energy for vertical wave lengths longer than 100 sdbar. The velocity structures persisted over the 56 hour of measurement and appeared to have longer time scales than the vertical displacements. Meridional energy exceeded zonal energy; however, the two components were coherent. We interpret these velocity structures as inertial‐gravity waves which were produced off the equator and are propagating through the equatorial region.
Oceanic CO2 produced by the precipitation of CaCO3 from brines in sea ice
Authors: Jones E. P. , Coote A. R.
Published: February 2008

Carbon dioxide is produced in brines formed during the growth of sea ice as a result of preferential precipitation of calcium carbonate. This process can explain the observed CO2 supersaturation in some arctic waters and could produce a CO2 flux into the ocean in ice‐covered waters of 1.5 mol m−2 y−1 or a total of 6×1013 mol y−1 for both the arctic and antarctic regions.
Simulation of nitrogen constituent measurements from the August 28, 1976, Stratoprobe III flight
Authors: Evans W. F. J. , McElroy C. T. , Kerr J. B. , McConnell J. C.
Published: February 2008

A simulation of the altitude distributions of HNO3, NO2, and NO measured on the Stratoprobe balloon flight of August 28, 1976, has been carried out by using a time‐dependent stratospheric model with extensive photochemistry. The measured ozone and temperature profiles were employed in the simulation. The simulated ratios for HNO3/NO2 and HNO3/NO are significantly larger than the measured ratios for HNO3/NO2 and HNO3/NO in the altitude range 20–30 km. Since these ratios are proportional to the hydroxyl densities, it is proposed that the actual hydroxyl densities are a factor of 3–5 lower than calculated in the model, using current chemical rate data. By assigning a pressure dependence to the OH + HO2 reaction rate as well as including the OH + HNO3 reaction rate to reduce the OH densities in the model over this altitude range, an empirical simulation of the measured ratios was obtained. The pressure dependence chosen for the rate was such that reasonable agreement with existing measurements of hydroxyl densities at higher altitudes was still obtained.
Estimates of interhemispheric transport of radioactive debris by the east African low‐level jet stream
Authors: Rangarajan C. , Eapen C. D.
Published: February 2008

The movement of air masses across the equator by way of the east African low‐level jet stream has been studied using fission products from the French nuclear tests of the South Pacific as tracers. The studies show that the transit time of air masses from Malagasy to India is 3–6 days and about 75% of the air mass on the west coast of India is from the southern hemisphere.
The distribution of NOx and the production of ozone: Comments [on “On the origin of tropospheric ozone” by S. C. Liu et al.]
Authors: Fishman Jack
Published: February 2008

The distribution of the oxides of nitrogen (NOx) in the troposphere is the most critical parameter for understanding the photochemical component of the tropospheric ozone cycle. Recent studies by Liu et al. (1980) and Kley et al. (1981) have derived tropospheric NOx distributions that we believe are not consistent with most of the recent NOx measurements and that, consequently, may lead to an incorrect interpretation of the tropospheric ozone budget.
Interannual atmospheric angular momentum variability 1963–1973 and the Southern Oscillation
Authors: Stefanick Michael
Published: February 2008

The total angular momentum variability of the atmosphere (below 75 mbar) for the 120‐month period May 1963 to April 1973 is determined (using a data set provided by A. Oort, Geophysical Fluid Dynamics Laboratory) and compared with the observed length of day (l.o.d.) variations during this time. With the mean, annual, and semi‐annual cycles removed, the angular momentum shows an irregular oscillation with periods of 3 to 4 years during this decade. The corresponding relative change that this would produce in the length of day is approximately ±0.2×10−8 which agrees with the observed interannual l.o.d. variations 1963–1973. This oscillation is evidently related to the well‐known oscillation in tropical air (and sea surface) temperatures which is part of the Southern Oscillation and lags behind the temperature oscillation by a few months. A simple thermal wind argument indicates that the observed amplitude (1°C) of the oscillation in tropical temperatures can produce a relative change in the rotation of the earth on the order of 0.2×10−8. Variations in the length of day and a Southern Oscillation Index are shown to be very similar during the 20‐year period 1955–1974.
Tools for oceanic small‐scale, high‐frequency flows: metal‐clad hot wires
Authors: Gust Giselher
Published: February 2008

A set of commercially available seawater‐resistant hot wire sensors has been used to measure velocities, turbulence intensities, and Reynolds stresses with spatial resolutions between 0.4 and 5 mm and 3–dB frequency response of 18 Hz. During tests and actual measurements, each exceeding 1000 hours in seawater, mostly with suspended sediments, slimes, bacteria, and algae, experience has been obtained since 1973 on long‐term stability, sensitivity, repeatability, directional resolution, permanent seawater exposure, contamination, and corrosion. Ruggedness and performance of metal‐clad hot wire probes under shallow and deep‐sea conditions up to 69–MPa (10,000 psi) pressure indicate that hot wires can be built to work well in the ocean.
The gulf stream front: A comparison between SEASAT altimeter observations and theory
Authors: Kao Timothy W. , Cheney Robert E.
Published: February 2008

In a recent paper by Cheney and Marsh (1981), SEASAT altimeter data were used to derive quantitative information on sea surface height anomalies across the Gulf Stream. In another recent paper by Kao (1980), the dynamics of the Gulf Stream front was investigated, and a similarity solution was obtained. The model gives a universal shape of the sea surface height rise and the width of that anomaly across the Gulf Stream. In this paper we present a quantitative comparison between the model and six Gulf Stream altimeter profiles representing a broad range of conditions. The remarkable closeness of fit is mutually reinforcing to both the model and to the role of satellite altimetry in ocean dynamics. Comparisons of the data with the well‐known theories of Stommel (1966) and Charney (1955) are also made, and implications of these comparisons are explored.
The three‐parameter model of the submarine light field: Radiant energy absorption and energy trapping in nepheloid layers
Authors: Stavn Robert Hans
Published: February 2008

The three‐parameter model of the submarine light field is here proposed. The model consists of three physical parameters: the scalar irradiance (E0), downwelling vector irradiance (Ez), and average cosine (μ) of the submarine light field. This model is derived from a general exponential decay equation that is valid for all submarine light fields free of horizontal divergence. From the exponential decay equation we derive equations for the calculation of radiant power absorbed in a given depth interval and the radiant power scattered into or out of that interval. Calculations of the radiant power attenuation in an East German lake demonstrate that a nepheloid layer functions as an energy trap.
Evaluation of atmospheric attenuation from SMMR brightness temperature for the SEASAT satellite scatterometer
Authors: Moore R. K. , Birrer I. J. , Bracalente E. M. , Dome G. J. , Wentz F. J.
Published: February 2008

To measure the radar backscatter from the ocean with enough accuracy to allow determination of the wind vector, the effect of attenuation in precipitating regions over the sea must be considered. The attenuation can be determined reasonably well from a knowledge of the brightness temperature observed by a microwave radiometer. For the SEASAT this radiometer was the SMMR. Two algorithms were developed to relate radiometric measurements and attenuation and hence to correct the measured values of scattering coefficient. The two algorithms were compared with the best available information on precipitation, but no direct information on attenuation was available. Hence, the basic comparisons reported here are between the wind vectors reported by surface observers and those determined by the SASS measurements with and without correction for atmospheric attenuation. In general, the attenuation correction appears to improve the results obtained. However, the ‘correction’ is not as good as it should be because of the differing size of the 18 GHz radiometer footprint and the SASS footprint, and because the scan patterns are different so that averages from several radiometer footprints may be involved in a single SASS correction.
Intercomparison of wind speeds inferred by the SASS, altimeter, and SMMR
Authors: Wentz F. J. , Cardone V. J. , Fedor L. S.
Published: February 2008

SEASAT carried three wind speed microwave sensors: a scatterometer (SASS), an altimeter (ALT), and a five‐frequency radiometer (SMMR). The winds inferred by these three sensors along with colocated in situ anemometer measurements are intercompared. The in situ comparisons show an agreement of about 2 m/s. A larger statistical data base is obtained by intercomparing the three sensors in the absence of in situ data. For nadir observations at wind speed below 10 m/s, the three instruments track each other very well and seem responsive to wind as low as 2 m/s. However, for winds above 10 m/s the ALT winds are biased low relative to the SASS and SMMR winds. The discrepancy at high wind speeds between the SASS and ALT is due to using different model functions in the geophysical processing. When properly filtered for land, sun glitter, and rain, the SASS and SMMR winds agree remarkably well. For 329 SASS and SMMR comparisons over a wind speed range from 2 to 20 m/s, the mean difference is 0.03 m/s, the standard deviation is 1.42 m/s, and the correlation is 0.95. The ability of the SMMR to measure wind speed is adversely affected by proximity to land and sun glitter. The SMMR cell must be at least 600 to 700 km from land, and the sun angle must be greater than 20° to ensure accurate winds. Both SASS and SMMR retrieve wind speeds near the eye of Hurricane Fico that are in good agreement with each other and with surface observations. Light rain of about 2 mm/h does not appear to seriously degrade the performance of the SASS or SMMR.
Near‐shore currents measured in ridge‐and‐swale topography off Long Island, New York
Authors: Lavelle J. W. , Swift D. J. P.
Published: February 2008

Eighteen near‐shore current records within an area 11 km2 on the Long Island inner shelf have been examined for indication of small‐scale topographic influence. In the frictionally influenced near‐shore water column, currents over the 39‐day records are generally oriented slightly clockwise of the longshore direction toward the principal axis of the local ridge‐and‐swale topography. This orientation angle is largest and closest to the local topographic axis when semidiurnal tidal currents dominate other flows, a result which may suggest that tidal currents play a role in molding the local topography. Viscous tidal current theory for a constant depth surface describes the observed dependence of the semidiurnal (M2) tidal current ellipticity and ellipse orientation on depth. The inferred vertical eddy viscosity coefficient ranges from 5 to 35 cm2/s.
Ozone monitoring in the troposphere and lower stratosphere: Evaluation and operation of a ground‐based lidar station
Authors: Pelon Jacques , Mégie Gérard
Published: February 2008

Ozone monitoring in the troposphere and lower stratosphere has been performed on an operational basis by using a ground‐based lidar station set up in 1980 at the Haute Provence Observatory (France). A description of the experimental system is given with a special emphasis on the technical achievements that take into account the optimization criteria of the differential absorption laser technique used in the measurements. The results obtained during several experiments in 1980–1981 are discussed in terms of ozone variability in the troposphere and lower stratosphere, ozone exchanges between these two altitude regions, and tropospheric ozone budget.
Combined refraction and diffraction: Comparison between theory and experiments
Authors: Liu Philip L‐F.
Published: February 2008

Laboratory experiments (Hales, 1980) concerning the wave field near a breakwater are used to compare with a uniform asymptotic theory developed by Liu et al. (1979). The breakwater was installed on a linear plane beach, and the orientation of the breakwater is perpendicular to the bottom contours. Excellent agreement between the theory and experimental data is observed. Numerical solutions based on the asymptotic theory are also given for the wave field near a detached breakwater.
Warm water interactions in the Barrow Canyon in winter
Authors: Garrison G. R. , Paquette R. G.
Published: February 2008

An extensive set of salinity‐temperature measurements was taken in the ice‐covered Barrow Canyon in early April 1976. An intrusion of relatively warm water into the mid‐depth of the canyon is believed due to a surge‐driven mixing of the Atlantic Layer with Arctic Ocean surface water on the upper continental slope.
Photochemical coupling between the thermosphere and the lower atmosphere: 2. D region ion chemistry and the winter anomaly
Authors: Solomon Susan , Reid George C. , Roble Raymond G. , Crutzen Paul J.
Published: February 2008

The primary source of ionization in the D region is provided by photoionization of nitric oxide by Lyman alpha radiation. The observation of enhanced electron densities in winter at middle and high latitudes therefore has often been attributed to enhanced nitric oxide densities in this region. This phenomenon is often called winter anomaly or winter anomalous absorption. The problem has been studied by combining an ion chemical model with a two‐dimensional time‐dependent model of the neutral atmosphere. The model extends from the ground to the base of the lower thermosphere and includes nitric oxide transport from the thermosphere as well as auroral production. The calculated nitric oxide distribution exhibits substantial seasonal and latitudinal variations, which strongly influence the ion chemical composition and simulate the winter anomaly very well. Other aspects of coupling between neutral and ion chemistry are also explored.
On the adequacy of the fixed locations of the surface‐based international network for inferring interannual ozone variability
Authors: Heath Donald F. , Schlesinger Barry M. , Kaveeshwar V. G. , Angell James K.
Published: February 2008

The consistency between interannual global ozone variations inferred from observations at the limited number of station locations of the surface‐based international ozone network and those derived from satellite observations with nearly complete global coverage has been investigated. Monthly ozone averages based upon the complete set of total ozone soundings derived from the backscattered ultraviolet instrument on the Nimbus 4 satellite have been compared with averages derived from a subset of these measurements taken within the vicinity of the stations of the surface‐based network. Comparisons have been made as well between averages derived from backscattered ultraviolet measurements over station locations and those derived from observations with the Dobson and M‐83 instruments. The number of stations in the north temperate zone appears adequate to represent monthly ozone averages to within 0.5%, except during the early phase of the northern hemisphere spring maximum when the total ozone fields change appreciably over scales well below global. However, the geographical distribution of stations does not properly represent different latitudes. The resultant error in the derived change in north temperate zone ozone between 1970 and 1971 is 0.5%. In the tropical and south temperate zones, ozone averages for use in deriving seasonal variability and trends are generally uncertain by about 1%. The precision is poorer than for the north temperate zone because the number of stations is appreciably smaller. However, in the south temperate zone, the average from the sample may differ from the average derived from the full data set by as much as 5% in some months, when major local maxima or minima in ozone appear southeast of Australia, where southern stations are concentrated. The uncertainty in the global averages which results is comparable in size to typical year‐to‐year changes.
The flux and mixing rates of Antarctic bottom water within the North Atlantic
Authors: Whitehead J. A. , Worthington L. V.
Published: February 2008

Calculation was made of the northward flow of Antarctic Bottom Water into the western North Atlantic Basin through a passageway approximately 300 km wide between the Ceara Rise and the Mid‐Atlantic Ridge at about 4°N. Two moorings carrying four current meters each were placed in the region where currents were expected to be the greatest and were left for 360 days. The current was not steady, but exhibited large surges with approximately a 60‐day time scale whose cause is unknown. Current meters in the fastest flowing region all exhibited a net northward flow. It is estimated that approximately 0.8×106 m3 s−1 of water colder than 1.9°C (potential temperature) flowed on the average into the North Atlantic, with this number possibly being too small by 0.3×106 m3 s−1 or too big by 0.1×106 m3 s−1 depending upon estimates of the width of the region, which the current meters sample. However, these numbers differ from geostrophic estimates of 1.98×106 m3 s−1, the disagreement coming almost entirely from the fact that the geostrophic estimates give a sizeable flux of water colder than 1.2°C while the current meters do not. Based upon the two different flux rates, residence times and mixing coefficients are calculated for Antarctic Bottom Water for each 0.1°C potential temperature interval from 1.0°C to 1.9°C. Finally, some comments on the dynamics of the northward flow are made.
The flux of dimethylsulfide from the oceans to the atmosphere
Authors: Barnard W. R. , Andreae M. O. , Watkins W. E. , Bingemer H. , Georgii H.‐W.
Published: February 2008

The role of biogenic dimethylsulfide from the ocean surface as a source of atmospheric sulfur has so far been largely based on the results of mass balance calculations and on a small number of determinations of DMS in seawater. On a cruise of the R/V Meteor across the Atlantic from Hamburg, F.R.G., to Montevideo, Uruguay, we have sampled the surface ocean at short intervals and analyzed over 300 seawater samples aboard ship immediately after collection. Simultaneously, the atmospheric concentration of DMS has been measured at 13 m above the ocean surface. Biological and chemical oceanographic data have been collected during the cruise to aid in the interpretation of the findings on DMS. A number of vertical profiles to the bottom of the ocean were analyzed for DMS and other parameters. The concentrations of DMS in the surface ocean ranged from 17.7 to 743 ng S(DMS)/1, with a mean of 91 ng S(DMS)/1 (n = 231) for the area traversed. This mean is significantly higher than previous work had suggested. The highest concentrations of DMS were found in productive regions on the continental shelves, in marginal seas and in some estuaries. The vertical distribution of DMS is closely related to the distribution of primary productivity, as measured by chlorophyll and nutrient concentrations. Low concentrations (≤10 ng S(DMS)/1) were found in the deep ocean. From these distributions and from our work on pure cultures of marine algae we conclude that marine primary producers are the dominant source of DMS to seawater and consequently to the atmosphere. The concentrations of DMS in the atmosphere ranged from 2 to 44 ng S(DMS)/m3. The mean concentration of 6.1 ng S(DMS)/m3 is significantly lower than postulated concentrations of 40–200 ng S(DMS)/m3 for marine background atmosphere, thus questioning the rates and mechanisms given for reactions of DMS in this environment. Model calculations for the transfer of DMS across the air‐sea interface, using the data on DMS in seawater and the concentration of DMS in the atmosphere, suggest a global flux of 34–56×1012 g of sulfur in the form of DMS per year from the oceans to the atmosphere.
Condensation sampling of soluble atmospheric trace gases
Authors: Farmer J. C. , Dawson G. A.
Published: February 2008

The condensation of water vapor onto a cooled surface can be used as a method of sampling atmospheric components; the method is investigated theoretically and experimentally. From solutions to the heat and mass flow within the convective boundary layer, it is shown that the method has greatest collection efficiency for highly soluble gases. Discrimination against particulates and relatively insoluble gases should be excellent. The method is illustrated by some measurements of NH3, HNO3, HNO2, SO2, HCl, H2O2, HCHO, HCOOH, and CH3COOH in the vicinity of Tucson, Arizona. Concentrations are in the part‐per‐billion range or below. Diurnal variations in these concentrations are discussed. Explanations are offered for a discrepancy between theoretical and actual rate of collection of water vapor.
Parameterization of IR cooling in a middle atmosphere dynamics model: 1. Effects on the zonally averaged circulation
Authors: Apruzese John P. , Schoeberl Mark R. , Strobel Darrell F.
Published: February 2008

A computationally efficient two‐stream parameterization of IR cooling is developed for a middle atmosphere dynamics model. The parameterization combines the monochromatic feature of an emissivity formulation with the computational simplicity of a single spatial integral to evaluate the monochromatic transfer equation. Our calculations show strong radiative control of the mesopause region (radiative relaxation rate > [5 days]−1) and the need for substantial deceleration of the mean zonal winds (∼40 m s−1 day−1) Calculated temperatures show good agreement in the summer hemisphere where planetary wave activity is negligible, but in the polar night of the winter hemisphere they are ∼30°K too cold which suggests planetary wave heating must make up the deficit. With observed ozone densities our globally averaged radiative equilibrium temperatures in the 65–75 km region are too cold and an additional heat source ∼1°K day−1 is required.