bluuebunny/crossref_metadata_2025 huggingface dataset:
Sea level variability due to meteorological forcing in the northeast Gulf of St. Lawrence
Authors: Garrett Christopher , Toulany Bechara
Published: February 2008

In an attempt to understand the causes of low frequency flow through the Strait of Belle Isle, we relate sea level data from four stations in the northeast Gulf of St. Lawrence to meteorological forcing. Our main tool is a multiple regression, at each frequency, of sea level on local atmospheric pressure and two orthogonal large scale pressure gradients which represent geostrophic winds. The results show an inverted barometer response to atmospheric pressure and a frequency‐dependent response to wind which can be tentatively interpreted in terms of coastal setup due to wind driven longshore currents, or barotropic setup of semi‐enclosed regions (such as the northeast Gulf or the whole Gulf). A simple model for barotropic flow through the Strait is developed in order to provide an estimate, from data at the western end of the Strait, of sea level changes on the Labrador shelf.
SEASAT altimeter determination of ocean current variability
Authors: Bernstein R. L. , Born G. H. , Whritner R. H.
Published: February 2008

Radar altimeters of great precision (≈10 cm), such as the one that flew on the SEASAT satellite, are capable of measuring the small oceanic height variations associated with geostrophic ocean currents. An experiment was conducted in the Kuroshio Current east of Japan, verifying this capability. Air‐expendable bathythermographs (AXBT's) were dropped to coincide with the SEASAT subtrack during flights on September 25 and October 5 and 13, 1978. Changes in surface dynamic height between flights were inferred from the AXBT data. They agreed generally to within ±10 cm of height changes observed in the altimeter data.
Fair weather space charge distribution in the lowest 2 m of the atmosphere
Authors: Kamra A. K.
Published: February 2008

Atmospheric space charge at 0.1, 1, and 2 m above the ground and the potential gradient have been measured in fair weather on level ground. Very large negative space charge values of up to 2 orders of magnitude larger than the normal daytime positive values have been observed to prevail during nighttime when the winds are calm. Changes in the polarity of space charges from positive to negative in the evenings, and from negative to positive in the mornings, are rapid and seem to coincide with the change in sign of the lapse rate at these levels. Nighttime negative space charge density decreases with height, and the daytime positive space charge density increases with height. Enhancement of potential gradient just after sunrise coincides with the morning reversal of the space charge polarity throughout the 2‐m height. The results support the view that convection currents comparable to conduction currents may flow at these levels. Short time changes in space charge density have been studied to show the inhomogeneity in space charge distribution close to the ground. Manifestation of the electrode effect has been observed. Different space charge distributions observed at different times of the day have been discussed with reference to the prevailing meteorological conditions.
Subharmonic transitions and group formation in a wind wave field
Authors: Mollo‐Christensen E. , Ramamonjiarisoa A.
Published: February 2008

Laboratory experiments in which waves from a mechanical wave generator were injected at the upwind end of a fetch‐limited wave field. The injected wave groups appear to grow at the expense of the ambient wind wave field, and the wind profiles in the boundary layer show large fluctuations when waves are injected. The effects observed appear to demonstrate the sensitivity of nonlinear modulational dynamics of surface waves to weak disturbances.
Analysis of remotely sensed long‐period wave motions
Authors: Meadows G. A. , Shuchman R. A. , Lyden J. D.
Published: February 2008

Synthetic aperture radar has been used to image long‐period (15–200 s) gravity waves in the nearshore region of Lake Michigan. These long‐period waves are a response of the sea surface to forcing by a nonmonochromatic, wind‐generated surface wave field. The synthetic aperture radar data were successfully compared with an in situ wave gauge record. Both one‐ and two‐dimensional fast Fourier transforms were generated from near and offshore regions of synthetic aperture radar data. The synthetic aperture radar‐derived near and offshore spectral estimates exhibited both low‐ and high‐frequency wave components. Classical bathymetrically controlled wave refraction was observed for both the short as well as long wave components of the sea surface. This paper demonstrates the ability of X band synthetic aperture radar to detect low‐amplitude, long‐period signals. The signals appear to correspond to a ‘surf beat’ generated by the incident wind wave field.
Observations of the principal tidal currents at Drake Passage
Authors: Nowlin Worth D. , Bottero Joseph S. , Pillsbury R. Dale
Published: February 2008

Twenty‐one long current records collected at 12 positions in Drake Passage are used to describe the principal diurnal (K1 and 01) and semidiurnal (M2 and S2) tidal current constituents in that region between the Atlantic and Pacific Oceans. The tide is predominantly semidiurnal in the northern passage and of mixed type at other locations. One‐quarter of the fluctuation kinetic energy of the records is between periods of 2 hours and 2 days. Approximately 50% of that energy is contained in two narrow bands centered at the diurnal and semidiurnal frequencies (the semidiurnal band also contains significant inertial current energy); the fraction of energy in these bands increases southward across Drake Passage from 39 to 66%. Admittance calculations show that an average of 56% of this band‐passed kinetic energy is coherent with the tidal forcing potential. Least square fitting (by the method of cyclic descent) of 250‐day records at the 10 most energetic short‐term tidal frequencies yields currents essentially coherent with the tidal forcing functions. From these fits the average partitioning of coherent tidal energy among the four principal tidal constituents is estimated: 75% at M2, 16% at S2, 9% at K1, and 3% at 01. Mean tidal ellipses for these four tides are constructed from the fits and used to describe depth and latitudinal variation across the passage and to make comparisons between the years 1975, 1976, and 1977. The variances of coherent diurnal tides in the deep water increase southward, whereas those for coherent semidiurnal tides are smallest in midpassage and increase more to the north than to the south. The noncoherent (residual) portions of the band‐passed currents are isotropic, in contrast to the coherent constituents, which are most energetic in the through‐passage (along‐current) direction. In general, these non‐coherent oscillations are most energetic for depth ranges and locations of greatest hydrostatic stability. The squared coherence and phase relationships between principal axis components obtained from the least square fits showed the K1, M2, and S2 tides to propagate with southward components while the 01 has a northward component of propagation across Drake Passage. Coherence between current meters separated vertically on the same mooring was greatest for the diurnal tide K1. Temporal variability of the tides is described by time series of hodographs and of kinetic energy density of currents in narrow pass bands centered on the four major tidal constituents.
Measurements of charged precipitation in a New Mexico thunderstorm: lower positive charge centers
Authors: Marshall Thomas C. , Winn William P.
Published: February 2008

We designed an instrument to measure the charge and vertical velocity of individual precipitation particles inside thunderclouds. A balloon carried the particle charge instrument, an electric field meter, and a standard meteorological radiosonde upward into thunderclouds over Langmuir Laboratory in central New Mexico. During one balloon flight the instruments encountered two regions of positive charge below the main negative charge center. We identify these positive regions with the lower positive charge centers that have been described in the literature for many years. We find the following points: (1) One region had an estimated total charge of 0.4 C. The other had 2 C. (2) The charge resided on precipitation particles. The particles' charges typically ranged between 10 and 200 pC, but a few particles had charges up to 400 pC. Their diameters lay between an estimated 1–3 mm. The charges were too large to be explained by the polarization induction mechanism. We favor the hypothesis that lightning provided the positive charge in the lower positive charge centers. (3) The motion of the lower positive charge centers enhanced the electrical energy of the storm, but their contribution to the overall electrical budget was small. (4) The field excursions (at the ground) associated with precipitation (FEAWPs) described by C. B. Moore and B. Vonnegut are probably caused by lower positive charge centers descending on precipitation. The larger (2 C) lower positive charge center caused a FEAWP. Negatively charged precipitation particles passed through our instrument near the top of its trajectory just before the balloon was struck by lightning. The charge density on precipitation particles was substantial, but we do not have enough information to comment on the role the particles may have had in generating the main region of negative charge.
Sea surface temperature mapping with the SEASAT microwave radiometer
Authors: Bernstein R. L.
Published: February 2008

Sea surface temperature data from the SEASAT Scanning Multichannel Microwave Radiometer (SMMR) has been mapped for the period July 7 to August 6, 1978, in the western North Pacific, 20°N–50°N, 140°E–180°, and compared against similar maps constructed from all available ship observations. The temperature difference between the SMMR and ship maps has a standard deviation of 0.75°C, about a mean bias of 0.22°C, SMMR being warmer. The average standard deviation of all individual observations about the mapped values is 1.51°C and 2.10°C for SMMR and ship, respectively. Both the SMMR and ship maps exhibit the known major climatological features for the region. In addition, both data types yield similar maps of sea surface temperature anomaly (departure from climatology), with large‐scale (>500 km) anomaly features of 1°–3°C. Aside from having a lower noise level, the SMMR data is superior to the ship data for constructing large‐scale maps because it is more uniformly distributed in space and time.
Numerical solution of water‐wave refraction and diffraction problems in the parabolic approximation
Authors: Tsay Ting‐Kuei , Liu Philip L‐F.
Published: February 2008

A numerical study of water‐wave refraction and diffraction problems is performed. The analysis is based on the linear wave theory and the parabolic approximation, which provides the forward scattered wave field. Two problems are considered in particular: (1) the diffraction of monochromatic waves by a thin breakwater in a slowly varying depth and (2) the wave field near caustics predicted by linear wave ray theory. Numerical solutions of these problems are compared to either analytical results or laboratory experimental data.
Fossil turbulence in the Denmark Strait
Authors: Gibson Carl H.
Published: February 2008

Temperature microstructure measurements by Oakey and Elliott [1980] in the Denmark Strait are interpreted using the fossil turbulence theory of Gibson [1980]. All of the microstructure appears to be fossil temperature turbulence at large scales; that is, remnant temperature fluctuations produced by overturning turbulence which persist after the fluid ceases to be turbulent at the scale of the fluctuations. Most of the microstructure appears to be fossil at all scales. Because completely active turbulence patches were not detected, the turbulent mixing process in the Denmark Strait has been undersampled. Consequently, actual average values of vertical diffusivity and turbulent dissipation of temperature and velocity may be much larger than those estimated from the Oakey and Elliott [1980] dropsonde measurements. This may resolve the discrepancy between the vertical heat flux estimated from bulk flow properties of the boundary overflow region, and a heat flux value 2 orders of magnitude less estimated from the measured dropsonde dissipation rates assuming the microstructure in the region is turbulent rather than fossil turbulence. To reliably infer space‐time average turbulence dissipation rates and diffusivities in the ocean from microstructure measurements apparently requires larger data samples and better models of stratified turbulence than are presently available.
Airborne ice nucleus measurements around the Hawaiian Islands
Authors: Schnell R. C.
Published: February 2008

Atmospheric ice nucleus and aerosol samples were collected with an aircraft at various altitudes over the ocean upwind of the Hawaiian Islands on four days in June 1980. Below the subtropical trade wind inversion, ice nucleus activity was detectable at −10°C in concentrations of 11−1 active at −12°C. Above the inversion, threshold activity decreased to −15°C and colder. Ice nucleus concentrations were about 10−5 of the number of aerosol particles at all levels.
An analysis of the optical features of the near‐bottom and bottom nepheloid layers in the area of the Scotian Rise
Authors: Spinrad Richard W. , Zaneveld J. Ronald V.
Published: February 2008

Profiles of light transmission versus depth have been studied in the region of the Scotian Rise of the North Atlantic at bottom depths between 4900 and 5000 m. A component model has been developed and consists of three components of transmission which can be combined to duplicate accurately any given transmission profile. Two of the components are shown to be representative of several basic phenomena: the particle concentration within a uniform flow and the separation of a benthic nepheloid layer. In the case of a uniform flow it is the relative magnitudes of settling and eddy diffusion which determine the shape of the transmission profile. Separation of the benthic nepheloid layer was inferred to be caused by an occasional cross‐slope velocity component. The physical interpretation of the third component was ambiguous. Eulerian and Lagrangian transformations of the data show that benthic ‘storms’ that were detected at one location and time appeared nearly identical at a later time downstream and that benthic ‘storms’ can be detected over a large distance. Distance and time scales obtained from these transformations show the area of the Scotian Rise to be one characterized by bottom ‘storms’ which keep their general form over periods of at least 2 weeks and for distances traveled of at least 400 km.
Air‐sea particle exchange at a nearshore oceanic site
Authors: Sievering H. , Eastman J. , Schmidt J. A.
Published: February 2008

Field measurements of particle covariance (eddy flux) have been made at a nearshore marine location by using an active scattering aerosol spectrometer interfaced with analog signal processing. A classic interpretation of results identifies a predominant particle upflux in the diameter size range 0.2 < D < 0.5 μm. Chemical characteristics of the aerosol at the site confirm the presence of sea salt in the size range sampled, indicating that recorded upflux events are linked to sea salt particle production at the surface. However, the aerosol at the site is about half (or more) continental in origin. An evaluation of aerosol transformation processes shows that particle growth and decay mediated by the relative humidity gradients present over the sea may have significantly altered the particle covariance results and hampers the quantitative interpretation of the data.
A stratospheric chemical instability
Authors: Fox J. L. , Wofsy S. C. , McElroy M. B. , Prather M. J.
Published: February 2008

The equations which determine partitioning of Clx in steady state have multiple (three) solutions under conditions which might arise in the high‐latitude winter stratosphere. Two of these solutions are stable, one is unstable, to infinitesimal perturbations. The relative stability of solutions is examined by subjecting the system to finite perturbations. The more stable solution is found to eliminate the less stable when semi‐infinite volumes of the two solutions are placed in contact. The high‐ClO, low‐NO2 solution is more stable under most conditions. Transitions from less to more stable states are slow in winter but may occur more rapidly when the seasonal variation of insolation is taken into account.
On the characteristics of some radiation fields from lightning and their possible origin in positive ground flashes
Authors: Cooray Vernon , Lundquist Stig
Published: February 2008

Characteristics of some radiation field waveforms of lightning from thunderstorms Sweden are presented. The waveforms are distinctly different from previously published signatures from intracloud discharges. In general, they are similar to the radiation fields produced by return strokes in negative ground flashes except for the initial polarity, but several important differences are found in the detailed characteristics. The zero‐to‐peak rise times of these waveforms are found to be in the range 5–25 μs. The waveforms begin with an initial portion or front which rises slowly for 3–20 μs to about half of the field peak amplitude. The observed mean values of 13 μs and 9 μs of zero‐to‐peak rise time and front duration, respectively, of these waveforms are about twice the corresponding values observed for negative return strokes. The mean radiation field peak value, normalized to 100 km, for these waveforms is 2 times that for negative return strokes. Some waveforms were preceded by small‐amplitude pulses which are assumed to be produced by a leader process. The mean separation in time of these pulses is about 26 μs, which may be compared with 14 μs observed for negative return strokes. Another important feature is the presence of ‘slow tails’ in some of these waveforms, indicating the presence of long‐lasting currents in their sources. It is suggested that the sources of the observed waveforms are return strokes bringing down positive charge to earth.
On the growth of a thermally modified boundary layer by advection of warm air over a cooler sea
Authors: Hsu S. A.
Published: February 2008

When warm air flows from land over a cooler sea, the air is modified. It is shown that h = cX½, where h is the height (in meters) of this modified layer over the water, X is the distance downwind from the coast (i.e., the fetch), and c is the proportionality constant. This equation is simplified from a theoretical equation and two independent dimensional analyses. Applying the simplified equation to data from four field studies, particularly the 1979 Monsoon Experiments, in which data sets were obtained under 100‐ to 1000‐km‐long fetch conditions, c is found to be approximately 18. Commonly observed values for the pertinent parameters are used. Variation in h is less than 20% as compared with results obtained by using theoretical equations and dimensional analyses individually. Note that this variation is comparable to the contribution of entrainment, which was not taken into account in the other formulas.
Selection of CO2 concentration data from whole‐air sampling at three locations between 1968 and 1974
Authors: Gillette Dale A. , Steele Alfred T.
Published: February 2008

Three methods for rejection of CO2 data were used to obtain CO2 concentration versus time for 1968–1973 for Station Charlie (a ship in the North Atlantic), Niwot Ridge near Nederland, Colorado, and Key Biscayne near Miami, Florida. From examination of the results it was concluded that short‐term variation and error were not large for the Station Charlie data. There was a suggestion of occasional contamination at Key Biscayne and evidence of more frequent contamination at Niwot Ridge, after 1970. Values obtained for annual CO2 increases were 1.3 and 1.2 ppm (1959 SIO index) for Station Charlie and Niwot Ridge. Annual amplitudes were 15, 11, and 9.7 ppm for Station Charlie, Niwot Ridge, and Key Biscayne, respectively.
The determination of geoid undulations and gravity anomalies from SEASAT altimeter data
Authors: Rapp Richard H.
Published: February 2008

The global SEASAT altimeter data set has been edited and adjusted using a crossing arc procedure fixing one long arc to provide control. In doing this a set of 168 master arcs were formed from repeat and near repeat arcs. The adjustment, carried out by D. Rowlands, was done in a global net, and four regional areas. The average crossover discrepancy before the adjustment was ±1.5 m, while after the adjustment (solving for a bias and trend) it was ±28 cm. The examination of the crossover discrepancies by area indicated larger than normal discrepancies in certain areas such as the Hudson Bay, the Mediterranean, and the North and Baltic seas. Some of these discrepancies are caused by invalid tide values applied to the altimeter data in these areas. The adjusted SEASAT sea surface heights were used to predict point values at 1° × 1° intersections in 10 different geographic regions for comparison with corresponding GEOS 3 values. A mean difference (GEOS 3 minus SEASAT) of 1.3±0.67 m was found, the mean difference being caused by different ellipsoid parameters. The adjusted data were also used to determine mean surface heights and gravity anomalies in 37,9051°×1°and 1178 5° equal‐area blocks with some of these values being on land. These estimations were done using least squares collocation using covariances functions scaled to each 5° region. The average predicted standard deviation of the 1°×1° anomalies was ±5.1 mGal, and ±2.7 mGal for the 5° blocks. SEASAT values were compared to the GEOS 3 values, finding a difference of ±7.8 mGal and ±0.87 m for the 1°×1° data, and ±2.2 mGal and ±0.76 m for the 5° data. Comparisons with terrestrial data showed no significant difference between the GEOS 3/SEASAT implied anomalies, although a number of significant discrepancies have been resolved with the SEASAT data.
Generation of internal waves in Massachusetts Bay
Authors: Chereskin Teresa K.
Published: February 2008

Observations of stratified tidal flow over a submarine ridge indicate that the large amplitude and asymmetry of the topography are critical in determining the type of flow response. The observations consist of hydrographic, current meter, and echo‐sounding data and are used as a basis for inferring the generation mechanism of previously observed trains of internal waves. The flow response on ebb and flood tide is categorized according to the Froude number classification of sill flows proposed by Farmer and Smith (1980a). The calculated Froude numbers, response length scale, and duration differ markedly between the two phases of the tide due to the asymmetry of the bank. The development of two features in the acoustic imagery related to wave formation is followed.
On the stratification of turbulent mixed layers
Authors: Mahrt L. , André Jean‐Claude
Published: February 2008

The vertical distribution of density or temperature is studied in turbulent boundary layers stratified by either salt or temperature and driven in an annulus by a rotating screen. With rapidly growing boundary layers the buoyancy flux due to entrainment becomes sufficiently large that the boundary layer is no longer well mixed. Stratification in the boundary layer is largest near the entrainment interface, corresponding to extension of the density transition into the turbulent boundary layer. The stratification in the rest of the boundary layer is smaller and nearly independent of height. The mean boundary layer stratification and structure and integral properties of the density distribution are found to be strongly dependent on the ratio of the entrainment rate to the turbulent velocity scale.
Aqueous oxidation of SO2 by hydrogen peroxide
Authors: Kunen S. M. , Lazrus A. L. , Kok G. L. , Heikes B. G.
Published: February 2008

The aqueous oxidation of S(IV) by H2O2 is one of the principal paths of acid formation in the atmosphere. Several investigators have measured the rate constant for the reaction: H2O2 (a) + S(IV) (a) → H2SO4(a), as a function of temperature and pH. The reactant concentrations used, however, were several orders of magnitude greater than those found in precipitation or cloud particles. We have measured the rate constant at more typical environmental concentrations by using a different analytical technique in which excess S(IV) (10−6 to 10−5M) was reacted with H2O2 (∼10−7M). We followed the decay in H2O2 concentration with time by using an H2O2 luminol‐chemiluminescent instrument. The lower reactant concentrations we use obviate the use of buffers at our working pH range of 4.0 to 5.8. Our measurements of the S(IV)‐H2O2 rate constant were in substantial agreement with the previous measurements. We noted a first order dependence in the rate constant with hydrogen ion concentration and at 22°C find our results can be represented by k = (8.03 ± 0.18) × 107[H+] dm3 mole−1 s−1 when the pH is between 4.0 and 5.8.
Methyl halides in and over the eastern Pacific (40°N–32°S)
Authors: Singh Hanwant B. , Salas Louis J. , Stiles Robin E.
Published: February 2008

Methyl chloride, methyl bromide, and methyl iodide measurements in and over the eastern Pacific (40°N and 32°S latitude) show mean air concentrations of 633 parts per trillion (ppt), 23 ppt, and 2 ppt, and mean surface seawater concentrations of 11.5 ng/l, 1.2 ng/l, and 1.6 ng/l respectively. Long‐term ambient measurements at a marine Pacific site (39°N) show an essentially unchanging background, with some indication of high concentrations of methyl bromide and methyl iodide during summertime. The oceanic data indicate a mean surface supersaturation of 275%, 250%, and 340%, respectively, for these three methyl halides. Depth profiles show that methyl halides are most abundant in the top mixed layer of the ocean. Oceanic concentrations of methyl chloride and methyl bromide are significantly correlated (linear regression coefficient of 0.85), suggesting a common source. No relationship between oceanic methyl iodide concentrations and the other two halides could be found. Coexistence of high concentrations of methyl iodide with relatively low concentrations of methyl chloride and vice versa provided no direct support for the hypothesis that chloride ion reactions with methyl iodide may be the dominant oceanic source of methyl chloride. For the eastern Pacific, mean ocean to air fluxes (in units of 10−7 g cm−2 yr−1) of 13, 1, and 1 are determined for methyl chloride, methyl bromine, and methyl iodide, respectively. When extrapolated to global waters, they provide an adequate source to explain the atmospheric reservoir of these organic halides. Total organic bromine and iodine measurements would suggest that methyl bromide and methyl iodide contribute predominately to the tropospheric bromine and iodine organic reservoir.
The distribution and annual cycle of ozone in the upper stratosphere
Authors: Frederick J. E. , Huang F. T. , Douglass A. R. , Reber C. A.
Published: February 2008

Study of the global distribution of upper stratospheric ozone derived from backscatter ultraviolet (BUV/SBUV) instruments on the Nimbus 4 and 7 satellites reveals the following characteristics for the period June 1970 through May 1972 plus portions of 1978 and 1979. At pressures less than 5 mbar a local midlatitude maximum in the ozone mixing ratio develops in autumn and persists through the winter season in both hemispheres. However, by a pressure of 10 mbar the seasonal trend has reversed, with midlatitude summer values exceeding those in winter. The largest ozone mixing ratios in a global sense occur at tropical latitudes between pressures of 7 and 9 mbar. The general character of this pattern repeats from year to year, although differences in detail exist, especially in winter. This interannual variability in ozone increases the difficulty in extracting small long‐term trends from the available data base. The overall seasonal pattern revealed by the measurements is in accord with photochemical model predictions which include the annual variation in temperature and solar illumination.
The effects of energetic particle precipitation on the atmospheric electric circuit
Authors: Reagan J. B. , Meyerott R. E. , Evans J. E. , Imhof W. L. , Joiner R. G.
Published: February 2008

The solar particle event (SPE) of August 1972 is one of the largest that has occurred in the last 20 years. Since it is so well documented, it can serve as a good example of a major perturbation to the atmospheric electric system. In this paper, ion production rates and conductivities from the ground to 80 km at the peak intensity of the event on August 4 and for 30, 35, and 40 km for the 6‐day duration of the event are presented. At the peak of the event, the proton and electron precipitation currents, the ohmic current, and the vertical electric field are calculated inside the polar cap. The particle precipitation currents at this time greatly exceed the normal air earth current at altitudes above 30 km and produce reversals in the vertical electric field at 28 km and above. Calculations are presented of the vertical electric field at altitudes near 30 km where balloon measurements were made. Good agreement between the calculated and the measured vertical electric field verifies our ability to calculate disturbed conductivities at these altitudes from satellite measurements of proton spectra incident on the atmosphere. Despite the fact that at the peak of the event the vertical electric field near 30 km was shorted out by the solar particles and that the current carried by the solar particles exceeded the fair weather air‐earth current density in the stratosphere by large factors, it is concluded that the largest effect of an SPE of this magnitude on the atmospheric electric circuit is due to the Forbush decrease in the galactic cosmic ray flux rather than to the large increase in solar proton flux.
Variability of current, temperature, and bottom pressure across the west Florida continental shelf, winter 1981–1982
Authors: Marmorino G. O.
Published: February 2008

Observations are analyzed from four current meter moorings deployed on the broad continental shelf in the northeastern Gulf of Mexico from November 29, 1981, to February 8, 1982 (71 days). Consistent with recent modeling studies, the shelf circulation responds within an inertial period to the alternating up‐and‐down‐coast synoptic scale wind forcing. Average response to a 0.5 dyn cm−2 alongshore wind stress (as measured at the coast) is ∼20 cm s−1 off Cedar Key and ∼40 cm s−1 in the north where the shelf narrows (off Cape San Bias). Lower layer currents veer counterclockwise with depth, as in a bottom Ekman layer (e‐folding scale ∼8 m). The pressure field decays offshore (e‐folding scale ∼160 km) and yields a geostrophic current in good agreement with the observed alongshelf flow. Cross‐shelf and vertical variations of the tidal signals compare nicely with results from barotropic theory. Calculations indicate that most of the shoreward propagating tidal energy must be dissipated in depths of <20 m (within 50 km of shore).
Kinematics and correlation of the surface wind field in the South Atlantic Bight
Authors: Weisberg R. H. , Pietrafesa L. J.
Published: February 2008

Surface winds observed at Charleston, South Carolina, and at an offshore buoy located some 300 km to the east of Charleston are analyzed to determine operational transformations for estimating the offshore winds from the coastal winds. Both the statistics describing the wind field at each station along with those describing the correlation between stations are found to be seasonally modulated. Ensemble averaged (by season) transfer functions computed by using the first 3 years of available data are applied to a fourth independent data year for assessing their predictive utility. The transfer functions and predictability are both seasonally modulated and the transformation matrix is nondiagonal (each offshore wind velocity component depends upon both coastal components).
Gulf Stream meanders off North Carolina during winter and summer 1979
Authors: Brooks David A. , Bane John M.
Published: February 2008

Meanders produced most of the subtidal variability in the Gulf Stream off North Carolina during 1979. Recording instruments were moored in the lower half of the water column over the 200‐m and 400‐m isobaths for two periods of 4 months, One in the late winter and one in the late summer. In both seasons, the middepth current speed typically fluctuated between −50 cm s−1 and +100 cm s−1 about a 30 cm s−1 downstream mean. The velocity, temperature, and salinity fluctuations had a prominent weekly time scale in the winter, caused by the meandering stream. In the summer the weekly time scale was less prominent within a generally energetic 3‐ to 10‐day period band. In both seasons, the meandering currents were nearly in phase vertically, and the meanders propagated downstream at ∼40 km d−1. Shallow, in‐shore filaments of warm water, separated from the main stream by bands of cooler surface water, are often extruded from the Gulf Stream front during the shoreward‐most phase (crest) of meanders. Countercurrents, or upstream flow reversals, often occur under the filaments, forming the shoreward limb of cyclonic frontal eddies which are associated with uplifted cool water found upstream of meander crests. The energy source of the meanders off North Carolina remains obscure. The meandering currents locally transferred their kinetic energy to the mean stream, at about the same rate in each season. The loss of energy is consistent with an asymmetry or skewness of the meander process, often seen in satellite images of the surface temperature. The meandering currents were unrelated to the local wind, or to its curl or divergence, in either season. These results collectively point to an upstream source of meander energy, most probably made available by an instability of the Gulf Stream.
Climatology of the southeastern United States continental shelf waters
Authors: Atkinson Larry P. , Lee Thomas N. , Blanton Jackson O. , Chandler William S.
Published: February 2008

Data from 2872 hydrographic stations have been used to determine the oceanographie climatology of the southeastern United States continental shelf waters. The data were sorted by each degree of latitude and by depth into three zones (0–20 m, 21–40 m, 41–60 m). Inner shelf water temperatures were similar to adjacent land air temperatures, while outer shelf temperatures were moderated by the Gulf Stream. Minimum and maximum water temperatures occurred in Georgia and South Carolina inner shelf water. Bottom temperatures were unusually low off Florida in the summer probably because of shelf break upwelling. Surface salinity was lowest adjacent to the rivers and reached minimums in the spring at the time of high runoff. An exception to this occurred in the fall, when strong southward winds apparently advected low salinity coastal water southward and offshore flow was restricted. Heat flux was calculated from changes in monthly mean depth‐averaged inner shelf water temperatures. Heating occurred from March through July with maximum rates of 103 W m−2. Cooling occurred from October through February with maximum rates of −90 W m−2. Bulk stratification was estimated from the difference in near‐surface and near‐bottom monthly mean density. In the spring, stratification increases in inner shelf areas because of decreasing winds and increasing heat flux and runoff. By summer the whole shelf is highly stratified reflecting the contrast between high surface water temperatures and cooler bottom waters. Highest bulk stratification is found over the outer shelf. Stratification decreased with the approach offall with the associated cooling and high winds. Mean flow at midshelf was northward and appears to be produced by an along‐shelf slope of sea level of oceanic origin. Data are available with entire article on microfiche. Order from the American Geophysical Union, 2000 Florida Avenue, N.W. Washington, D.C. 20009. Document C82‐002; $2.50. Payment must accompany order.
Charge on ice crystals in laboratory clouds
Authors: Jayaratne E. R. , Saunders C. P. R.
Published: February 2008

Studies have been made of the electric charges carried on vapor‐grown ice crystals produced in the laboratory by nucleating a cloud of supercooled water droplets. The charges are less than laC (10−18 C) which is considerably below those charges reported elsewhere for similar ice crystal clouds.
Synoptic cloud variations in a low resolution spectral atmospheric model
Authors: Gordon H. B.
Published: February 2008

A spectral model of low resolution (two vertical levels and rhomboidal wave number truncation 15) has been used in simulations of January and July climatologies. The model has self‐generated cloud cover, and it is this aspect that is detailed in this report. The emphasis on cloud production has been chosen partly because of a noticeable lack of detailed information on cloud production from the few other models with self‐generated cloud. The cloud covers produced by each simulation are intercompared by use of global mean values, zonal values, through to instantaneous cloud production. It is found that the two simulations have rather different spatial and temporal characteristics. The global mean cloud cover shows much less variability between seasons than the hemispheric means, implying some stability in global cloud cover.
The mechanism of NO3 and HONO formation in the nighttime chemistry of the urban atmosphere
Authors: Stockwell William R. , Calvert Jack G.
Published: February 2008

The time dependence of the NO3 and HONO profiles observed by Platt et al. (1980a,b) in the nighttime urban atmosphere can be simulated by computer methods. With the assumption that the reaction, HO2 + NO2→ HONO + O2 (21), occurs at the maximum value of the rate constant observed by Howard (1977), k21 ≤ 3 × 10−15 cm3 molec−1 s−1, the time dependence of the [NO3], [O3], and [NO2] data can be fitted reasonably well. According to this hypothesis the HONO and NO3 chemistry are linked in that major nighttime sources of HO2 radicals involved in (21) are derived from two of the several decay reactions of the NO3 species—reactions with formaldehyde and acetaldehyde.
The photochemistry of anthropogenic nonmethane hydrocarbons in the troposphere
Authors: Brewer Dana A. , Augustsson Tommy R. , Levine Joel S.
Published: February 2008

The photochemistry of anthropogenically emitted nonmethane hydrocarbons (NMHC's) in the troposphere was studied by (1) developing a chemical mechanism which includes the reactions of anthropogenically emitted NMHC's and their associated intermediates (alkoxy and alkylperoxy radicals, aldehydes, peroxyacetylnitrate (PAN)) with both hydrocarbon and inorganic species and (2) performing model calculations with the mechanism using a one‐dimensional photochemical model of the troposphere. Calculations represent the region between 30°N and 60°N latitude. The inclusion of the chemistry of NMHC species with short lifetimes against chemical destruction provided detailed information about both the profiles of short‐lived NMHC species and the overall NMHC chemistry. Surface concentrations of emitted hydrocarbons, NOx, and HNO3 were well simulated. Only slight changes in the profiles of OH, HO2, NOx, and HNO3 were obtained when the NMHC chemistry was included. The inorganic nitrogen budget is not significantly altered by the inclusion of NMHC chemistry. The sensitivity of the PAN profile to changes in the magnitudes of NMHC emissions and to the introduction of a heterogeneous loss term to simulate advection was also assessed. Advection may be an important removal process for PAN in the mid‐latitudes.
The peak electromagnetic power radiated by lightning return strokes
Authors: Krider E. Philip , Guo Changming
Published: February 2008

The peak field that is radiated by a distant lightning return stroke almost always occurs within a few microseconds after the onset of the stroke, and therefore this peak is produced at a time when most of the stroke current is still close to the ground. Estimates of the peak electromagnetic (EM) power radiated by return strokes have been made by integrating the Poynting vector of measured fields over an imaginary hemispherical surface that is centered on the lightning source, assuming that ground losses are negligible. Values of the peak EM power from first and subsequent strokes have means and standard deviations of 2±2 ×1010 and 3±4×109 W, respectively. The average EM power that is radiated by subsequent strokes, at the time of the field peak, is about 2 orders of magnitude larger than the optical power that is radiated by these strokes in the wavelength interval from 0.4 to 1.1 μm; hence an upper limit to the radiative efficiency of a subsequent stroke is of the order of 1% or less at this time. From the above values of the radiated power, we also infer that at the time of the initial current peak, (1) the total voltage drop on the high‐current portion of a return stroke must be at least 2 to 7×105 V in first strokes and 2 to 4×105 V in subsequent strokes, (2) the total resistance of the high‐current channel must be at least 6 to 20 Ω in first strokes and 9 to 35 Ω in subsequent strokes, and (3) the energy that is required to form the propagating tip of the channel must be at least 102 to 103 J/m.
Use of long‐lived radon daughters as indicators of exchange between the free troposphere and the marine boundary layer
Authors: Kritz Mark A.
Published: February 2008

Fluxes and exchange coefficients are derived for the transport of 90Sr, 210Pb, 210Bi, and 210Po between the free troposphere and the marine boundary layer and between the boundary layer and the sea surface. Radionuclide concentrations previously measured near Hawaii are used in the derivations. Values obtained for the free troposphere/boundary layer exchange coefficient (expressed as a piston velocity) were 185, 228, and 203 m d−1 for 210Pb, 210Bi, and 90Sr, respectively. The magnitude of the local sea‐surface source of 210Po is also determined.
Parametric dependence of ocean wave‐radar modulation transfer functions
Authors: Plant W. J. , Keller W. C. , Cross A.
Published: February 2008

During the Marine Remote Sensing experiment of 1979 (MARSEN 79), we employed microwave techniques at X and L band to determine the dependence of ocean‐wave radar modulation transfer functions (MTFs) on various environmental and radar parameters. In this paper, we present these MTFs along with coherence functions between the AM and FM parts of the backscattered microwave signal and show that they both depend on several of these parameters. In addition to confirming many of the properties of transfer functions reported by previous authors, this work indicates that MTFs decrease with increasing angle between wave propagation and antenna‐look directions but are essentially independent of small changes in air‐sea temperature difference. Coherence functions are much smaller when the antennas are pointed perpendicular to long waves, however. X band transfer functions measured with horizontally polarized microwave radiation are found to have larger magnitudes than those obtained by using vertical polarization. Under conditions encountered in this experiment, transfer functions are independent of long‐wave amplitude when waves and antennas are aligned. Coherence functions, however, depend strongly on long‐wave amplitude. We show that this dependence implies that in addition to being modulated by long waves, short waves amplitudes fluctuate in response to environmental factors unrelated to long waves. Spectral densities of these fluctuations are shown to be comparable to those of modulations induced by long waves
Tower‐mounted radar backscatter measurements in the North Sea
Authors: De Loor G. P.
Published: February 2008

Measurements of average normalized backscatter made from a platform in the North Sea 10 km off the Dutch coast are reported here. The measurements provide information on the dependency of X band backscatter on grazing angle, wind speed, and look direction. It has been found that for grazing angles under 50° the dependency of backscatter on wind speed is highly sensitive to polarization and look direction. Also an unexplained difference between ground‐based and airborne measurements was observed.
Mass size distributions of chemical constituents of the winter Arctic aerosol
Authors: Hoff R. M. , Leaitch W. R. , Fellin P. , Barrie L. A.
Published: February 2008

Two field experiments, one from November 24 to December 14, 1981, and the second from February 19 to 27, 1982, were conducted at Igloolik, Northwest Territories, Canada, to study the composition and mass size spectrum of arctic haze aerosol. In addition, measurements were made of sulphur dioxide and sulphate. Mass size distributions were obtained for Cl−, NO3−, SO4=, Mg++, Na+, and NH4+ and for elements Cl, Na, V, Mn, I, and Br. The marine aerosol component at larger particle sizes is separated from the anthropogenic aerosol component at smaller particle sizes. Anthropogenic components (NH4+, SO4=, V, and Mn) are found predominantly on submicrometer aerosols. Marine components (Cl−, Na+, and Mg++) are predominantly supermicrometer in size. Results for NO3− and Br indicate that a gas phase component or precursor may exist in the arctic. Different transport during periods of the February experiment indicates higher concentrations for the haze aerosols and SO2 when the trajectories are from Asia. SO2 was found in concentrations of 0.3–4.3 μg/m3 and exceeded sulphate in mass. Possible explanations for the SO2/SO4= concentration ratio are given.
Possible dust devils, vortices on Mars
Authors: Ryan J. A. , Lucich R. D.
Published: February 2008

This paper presents the results of a study of local vortices, and dust devils, on Mars as observed by Viking Landers 1 and 2. It is found that these vortices are most common during Martian spring and summer, as occurs on earth. Seven of the vortices involve wind speeds that may raise dust from the Martian surface. There is no indication that these possible dust devils contribute to the planet‐wide spread of major dust storms. However, it appears that they may help in maintaining the atmospheric dust content. The data indicate that there is no preference in rotation direction, at least to core diameters of 300 m (corresponding to a region of influence of about 3 km diameter).
Sea‐breeze‐like winds across the north wall of the Gulf Stream: An analytical model
Authors: Hsu S. A.
Published: February 2008

Sea‐breeze‐like winds have been observed on the warmer side of the Gulf Stream when synopticscale winds blow from cool shelf water toward a warm water surface (Sweet et al., 1981). It is shown that a simple, thermally driven analytical model can explain satisfactorily the increase in wind speed from the cold to the warmer water side as resulting from horizontal temperature gradient across the Gulf Stream.
Internal waves in the Gulf of California: Observations from a spaceborne radar
Authors: Fu Lee‐Lueng , Holt Benjamin
Published: February 2008

Pronounced signatures of internal waves were detected repeatedly in the Gulf of California by the Seasat synthetic aperture radar (SAR). A series of nine images with exactly repeating ground coverage was used to study the temporal variability of the internal wave field in the area. It was found that the number of observed wave groups was highly correlated with the strength of the local tides: the maximum number occurred during spring tides and the minimum number occurred during neap tides, indicating that the internal waves were tidally forced. Most of the wave activity was found to the north of 28°N where the tides were the strongest in the Gulf. The application of a simple, nonlinear internal wave model to the observations indicated that the peak‐to‐peak amplitude of the observed waves was about 50 m with an uncertainty of a factor of 2. The estimated upper bound for the rate of the loss of tidal energy to internal waves was about 5×1015 erg/s, representing only 10% of the rate of the dissipation of the dominant M2 tide in the Gulf.