bluuebunny/crossref_metadata_2025 huggingface dataset:
Lake Huron winter circulation
Authors: Saylor James H. , Miller Gerald S.
Published: April 2008

Twenty‐one current meter moorings were deployed in Lake Huron during winter 1974–1975. The moorings were set in November 1974 and retrieved approximately 6 months later. The stations were configured on a coarse grid to measure the lake‐scale circulation during winter. Water temperature was also recorded in nearly all of the 65 current meters deployed. Results reveal a strong cyclonic flow pattern in the Lake Huron Basin persisting throughout the winter. The observed winter circulation was in essence very similar to what is now believed to be the summer circulation of epilimnion water, although the winter currents penetrated to deeper levels in the water column and were more intense. Winter cyclonic flow persisted in a nearly homogeneous water mass, while summer currents have been shown to exhibit an almost geostrophic balance with observed water density distributions. This suggests that the current field driven by prevailing wind stresses across the lake's water surface may be largely responsible for maintaining the horizontal gradients of water density observed in the lake during summer. Analyses of energetic wind stress impulses reveal the prevailing wind directions that drive the dominant circulations. When combined with results of summer surveys, the winter studies permit a description of the annual cycle of horizontal current speed variation with depth in Lake Huron.
Typhoon June winds estimated from scanning microwave spectrometer measurements at 55.45 GHz
Authors: Grody N. C. , Hayden C. M. , Shen W. C. C. , Rosenkranz P. W. , Staelin D. H.
Published: April 2008

Microwave radiometric measurements in the 60‐GHz oxygen band are considered, to infer atmospheric wind fields associated with tropical storms. On the basis of the thermal wind equation the radial derivative of brightness temperature is related to the vertically weighted tangential wind through a wind weighting function. The theory is tested in an analysis of Nimbus 6 scanning microwave spectrometer (Scams) 55.45‐GHz data through typhoon June in November 1975. Scams‐derived winds are obtained for 3 days throughout the storm area and are compared with 700‐mbar aircraft reconnaissance winds. Major differences with the reconnaissance winds occur primarily near the storm center presumably owing to Scams' insufficient horizontal resolution. Also discussed are the errors due to upper level wind contributions and instrumental noise.
The response of stratospheric constituents to a solar eclipse, sunrise, and sunset
Authors: Herman J. R.
Published: April 2008

The combination of measurements and detailed stratospheric modeling of time‐dependent events can be used to confirm chemical mechanisms and their laboratory rate constants or to deduce additional atmospheric properties such as the temperature structure. Sunset, sunrise, and a solar eclipse are events that are characterized by a relatively strong forcing function of brief duration. For these time scales, the detailed time‐dependent photochemical and vertical diffusion equations can be solved to predict the variations of minor constituents that are physically important and accessible to current measurement techniques. Careful simultaneous solutions of these equations have shown a significant daytime variation of ozone down to altitudes of about 30 km that can affect the interpretation of spectral absorption type experiments. The calculated sunset variations of [NO] and [HO] show a log linear concentration decay for limited time periods that can be readily converted into atmospheric temperatures by using known reaction rates up to about 70‐km altitude. Measurements of the time‐dependent behavior of [NO] and [NO2] during the eclipse of February 26, 1979, are expected to be made from the U2 aircraft at 20‐km altitude. If the measurements have sufficient sensitivity, they can be used along with the model predictions to confirm some laboratory chemical rate constants and to estimate the [ClO]/[ClNO3] ratio at 20‐km altitude.
Comparison of seasonal variations of upper stratospheric ozone concentrations revealed by Umkehr and Nimbus 4 BUV observations
Authors: DeLuisi John J. , Mateer Carlton L. , Heath Donald F.
Published: April 2008

This paper reports the results of a comparison between upper stratospheric ozone concentration profiles in the region between 22 and 1.4 mbar, as determined from surface‐based Umkehr observations and satellite Nimbus 4 BUV observations. The Umkehr data, consisting of monthly averages of observations extending over several years or longer, were obtained at three stations located in the northern hemisphere and two in the southern hemisphere. The BUV data were obtained during the period from May 1970 to March 1971. Aside from some bias in the magnitudes of the Umkehr and BUV data, marked annual cycles of ozone concentration in the upper stratosphere are clearly revealed. Above 4 mbar the profiles show a summer minimum and a winter maximum, while below 4 mbar the annual variation is reversed from this pattern. In the northern hemisphere the winter maximum is accompanied by a secondary minimum of 1‐ to 2‐month duration near 3 mbar. This short‐term minimum is much less obvious in the southern hemisphere data. Some of the problem of attempting to monitor long‐term changes in the upper stratosphere are discussed briefly.
On the generation of the seasonal coastal upwelling in the Gulf of Guinea
Authors: Clarke Allan J.
Published: April 2008

Seasonal upwelling in the coastal waters of the Gulf of Guinea is unusual because classical coastal upwelling theory does not even qualitatively hold there; there is no significant relationship between the upwelling and the local longshore wind stress. In this paper an attempt is made to qualitatively explain the Gulf of Guinea seasonal upwelling using coastal trapped forced wave dynamics. Two independent sets of data were used to compare theory with observation. Both indicate that provided dissipation of the travelling wind‐forced wave is taken into account, the theory agrees qualitatively with observation. The implication is that the upwelling is generated by coastal wind forcing several hundred kilometers east of the upwelling region. The Gulf of Guinea coastal upwelling therefore does not seem to be related to upwelling generated along the equator or to deep ocean basin forcing—it is not an ‘anti El Niño,’ as has been postulated elsewhere.
Low‐frequency sea level and current fluctuations along the coast of northwest Italy
Authors: Elliott Alan J.
Published: April 2008

Two‐month long records of current, sea level, and wind stress, collected during April and May of 1977, are analyzed for locations in the shallow waters off the coast of northwest Italy. The mean current was directed along the coast towards the northwest with a strength of 5.0–6.0 cm s−1; this flow continued past the island of Elba, progressing from the Tyrrhenian Sea into the Ligurian Sea. Sea level fluctuations were coherent along the Ligurian coast of Italy and were mainly due to a wind‐induced setup caused by the semienclosed nature of the basin; only a fraction of the sea level disturbances in the Tyrrhenian Sea propagated into the Ligurian basin. There was low coherence between the nearshore current and sea level, suggesting that shelf waves may play only a minor role in the dynamics of the region. Instead, the relation between the wind stress, current, and the slope of the sea level suggested that the region displays characteristics similar to those of a semienclosed area. The alongshore currents were coherent with the wind at the 5‐day time scale; this agrees with the period of cyclone activity in the area and suggests that the shelf waters respond coherently when the wind field is spatially well organized during cyclogenesis. Consequently, an adequate hydrodynamic model of the region would need to couple both the atmospheric and the coastal responses.
Height and period distributions for waves off Mangalore Harbour—west coast
Authors: Dattatri J. , Raman H. , Shankar N. Jothi
Published: April 2008

The results of the investigations conducted to study the distributions of wave heights and wave periods of successive waves are presented in this paper. Ocean wave data obtained off the Mangalore Harbour on the west coast of India are utilized for this purpose. The study indicates that the Rayleigh distribution for the wave heights is valid well beyond the narrow band assumption. The theoretical model for the above period distribution proposed by Longuet‐Higgins does not provide a better fit for the observed data than the Rayleigh distribution does for the square of the wave period. Certain characteristics associated with the joint probability distribution proposed by Longuet‐Higgins are not confirmed by the data analyzed.
Isotopic composition of river runoff on the U.S. east coast: Evaluation of stable isotope versus salinity plots for coastal water mass identification
Authors: Torgersen T.
Published: April 2008

Measurements of δD and some δ180 measurements were made on 36 rivers which drain the east coast of the United States. The data are consistent with the work of Friedman et al. (1964). The streamflow data of Bue (1970) were used to estimate the mean isotopic composition of runoff entering the Gulf of Maine, the Mid‐Atlantic Bight, and the South Atlantic Bight. Assuming binary mixing between central Atlantic water and these fresh runoff waters, coastal water in the Gulf of Maine is isotopically indistinguishable from runoff into the Mid‐Atlantic Bight and runoff from the St. Lawrence at salinities greater than 32‰. However, up to salinities of 34‰ the mean isotopic composition of runoff into the South Atlantic Bight is sufficiently different from the Mid‐Atlantic Bight that the identification of coastal water masses in and around Cape Hatteras by δD and/or δ180 versus salinity plots should be possible.
Observation of a large meander in the Agulhas Current
Authors: Gründlingh Marten L.
Published: April 2008

An analysis of four monthly surveys of the Agulhas Current in 1973 revealed a meander of 200‐km amplitude off the southern African east coast. The phase velocity of the advecting meander is estimated at 20 cm s−1 in a southwesterly direction, and evidence was found of weak upwelling in a cyclonic eddy trapped inside the meander.
Summertime synoptic variability of the Middle Atlantic Shelf Water/Slope Water Front
Authors: Mooers Christopher N. K. , Garvine Richard W. , Martin Wayne W.
Published: April 2008

A quasi‐synoptic study of the shelf water/slope water front off New Jersey, Delaware, and Maryland in mid‐July 1977 revealed an isolated body of very cold (<6°C) water in the near‐bottom ‘cold pool.’ Its volume at least halved over 10 days during which nearby shelf waters were perturbed by two anticyclonic (warm core) eddies located over the continental slope. Water colder than 6°C lay along the bottom between the 80‐ and 100‐m isobaths and was about 30 m thick. The seaward edge of the cold pool (here denoted as colder than 8°C) marked the inshore boundary of the shelf water/slope water subsurface temperature front, with 10°C variations per 2–20 km, depending upon alongshelf location. The thermocline underwent large displacements and deformations over 10 days, indicative of vigorous upwelling and downwelling and large potential vorticity changes at the shelf break. The dominant scales of variability (or correlation scales) in the thermal fields were 30 km alongshelf, 10 km cross shelf, and 10 to perhaps 20 days. (The internal radius of deformation on the outer shelf is about 15–25 km.) There was substantial vertical structure on the scale of 10 m or less. A surface convergence zone coincided with a surface roughness band (‘tide rip’) near the shelf break, and internal gravity wave activity seemed intense there too. Two independent estimates of vertical velocity at the shelf break suggested values of about 10−2 cm/s, one for a time scale of a week or longer and the other for a time scale of at least a few hours. Over Wilmington Canyon a large ‘lip’ of cold pool intruded into the slope water along the southwestern side of the Canyon, perhaps undergoing entrainment and ‘calving’ by an anticyclonic eddy located over the slope. There was further evidence of offshore entrainment throughout the water column between the two eddies.
Sea ice ridging over the Alaskan Continental Shelf
Authors: Tucker W. B. , Weeks W. F. , Frank M.
Published: April 2008

Sea ice ridging statistics obtained from a series of laser surface roughness profiles are examined. Each set of profiles consists of six 200‐km long flight tracks oriented approximately perpendicular to the coastline of the Chukchi and Beaufort seas. The landward ends of the profiles were located at Point Lay, Wainwright, Barrow, Lonely, Cross Island, and Barter Island. The flights were made in February, April, August, and December 1976, and one additional profile was obtained north of Cross Island during March 1978. It was found that although there was a systematic variation in mean ridge height
with season, with the highest values occurring in late winter, there was no systematic spatial variation in h at a given time. The number of ridges/km (μ) also are high during the late winter with the highest values occurring in the Barter Island and Cross Island profiles. In most profiles, the ice 20–60 km from the coast is more highly deformed (higher μ values) than the ice either nearer the coast or farther seaward. The Wadhams model for the distribution of ridge heights gives better agreement with observed values in the higher ridge categories than does the Hibler model. Estimates of the spatial recurrence frequency of large pressure ridges are made by using the Wadhams model and also by using an extreme value approach. In the latter the distribution of the largest ridges per 20 km of laser track was found to be essentially normal. Wadhams' distribution consistently predicts slightly larger ridge sails than does the extreme value approach. The main factors currently limiting the accurate prediction of the temporal recurrence of large pressure ridges are limited knowledge of the drift of near‐shore ice and data that would permit the assessment of year to year variability in μ.
The pressure field along the western margin of the North Atlantic
Authors: Csanady G. T.
Published: April 2008

The surface elevation field over a shelf‐slope region is subject to a parabolic differential equation, the timelike coordinate being longshore distance in the direction of propagation of vorticity waves. Two source terms in this equation contain long‐isobath and cross‐isobath density gradients. In the absence of long‐isobath variations the particular solution of the equation containing the cross‐isobath density gradient source term describes a steric setup distribution, which represents a plausible extension of the dynamic height method to shallow water. When long‐isobath variations of density are also present, the steric setup solution is complemented by a residual field, which is essentially a diffusive smoothing out of the steric setup distribution. The steric setup distribution calculated for the shelf‐slope region of the Northwest Atlantic from Cape Hatteras to the Grand Banks shows two major features: a mound of water associated with the St. Lawrence outflow and a rapid drop at the shelf break associated with an upper slope mean current having a surface velocity of the order of 20 cm s−1. The effects of the St. Lawrence outflow are felt mainly over the Scotian Shelf and in the Gulf of Maine. The shelf break current is apparently a boundary layer component of the cyclonic gyre between the Gulf Stream and the North American mainland.
Nonlinear analysis of a simple Sea Ice—Ocean Temperature Oscillator Model
Authors: Moritz Richard E.
Published: April 2008

A simple model of climatic fluctuations in mean ocean temperature and latitudinal extent of sea ice (Saltzman, 1978) is investigated to determine the effects of nonlinearity and the initial state of the system. Solutions of the governing equations are analyzed as trajectories in a phase plane with coordinates corresponding to the sine of ice edge latitude η and mean ocean temperature θ. The model is found to be transitive for all physically plausible initial values such that all solutions go to θ0 = 278°K and η0 = 0.885 as the time goes to infinity. The nonlinear term does not alter the qualitative nature of the model response to perturbations from the equilibrium values, which is characterized by damped linear oscillations about η0, θ0. The distance from the model ice edge over which active melting or freezing is allowed determines the period and decay time constant for the oscillations. The plausible lower limit for this distance parameter leads to the freezing point in the ocean from seemingly reasonable initial values, but the modeling approximations cease to apply when θ reaches the freezing point. The model illustrates one of many possible modes of internal oscillations within the earth's climatic system.
The reflection of impulses from a nonlinear random sea
Authors: Jackson Frederick C.
Published: April 2008

Non‐Gaussian ocean wave statistics are accounted for in a simple model of the reflection of radar impulses from the sea at near‐vertical incidence. In the geometrical optics approximation to microwave backscatter, the impulse response of the sea surface is proportional to the joint probability density function (pdf) of wave height and slope, where the wave height corresponds to the appropriate propagation delay time and the slope satisfies the condition for specular reflection. The joint pdf is calculated according to the theory of Longuet‐Higgins (1963) on the distributions of variables in a ‘weakly nonlinear’ random sea. The long‐crested approximation is made, a Phillips wave spectrum is assumed, and the Gram‐Charlier series is truncated after skewness terms. It is found that the height and height‐slope skewness coefficients bear the ratio 1:2 and that consequently, the impulse response of the sea at vertical incidence is very nearly equal to wave height pdf. The mean of the distribution, however, is not located at true mean water level but is negatively biased in an amount equal to the height skewness coefficient times the rms wave height. The derived impulse response and conditional cross section versus wave height are in excellent agreement with the Yaplee et al. (1971) observations. It is suggested that the empirically determined and theoretically predicted sea state bias be corrected for in the routine processing of satellite radar altimeter data.
A developing turbulent surface shear layer model
Authors: Csanady G. T.
Published: April 2008

The development of a surface shear layer, following the sudden application of wind stress, is governed by a steady increase in total momentum and a downward penetration of the shear flow region. Analogy with the turbulent boundary layer suggests a two‐layer conceptual model with an interface layer at the surface and an outer layer below. The growth of the outer layer may be supposed to be described by an entrainment law and an eddy viscosity proportional to local length and velocity scales. Matching to an interface layer yields a surface velocity increasing only very slowly with time and having a typical magnitude of 30u*. A comparison with constant viscosity and space dependent viscosity models shows that a unique feature of the developing shear layer model is the vertical penetration of a shear impulse, followed by low shear in the developed region of the flow. Some scant experimental data seem to support this model, but systematic experimental work on the problem is yet to be carried out.
Increased atmospheric CO2: Zonal and seasonal estimates of the effect on the radiation energy balance and surface temperature
Authors: Ramanathan V. , Lian M. S. , Cess R. D.
Published: April 2008

The climatic effects of increased atmospheric CO2 are discussed in the context of the effect upon two basic components of the climate system, namely, (1) latitudinal and seasonal radiative heating of the surface‐troposphere system and (2) the enhancement of latitudinal and seasonal surface temperatures. Radiative transfer model calculations show that the radiative heating of the surface‐troposphere system (caused by increased CO2) undergoes substantial latitudinal and seasonal variations. The seasonal variations are most pronounced at high latitudes. The increased CO2 heating of the surface and troposphere is significantly different for clear sky and overcast sky conditions. These CO2 heating calculations were then incorporated within a seasonal energy balance climate model for the northern hemisphere. Despite the significant seasonal variations in surface‐troposphere heating due to increased CO2, the seasonal model results, when annually averaged over all latitudes, yield essentially the same CO2‐induced increase in hemispherical mean surface temperature as does an annual energy balance model. The seasonal model, however, shows a strong seasonal variation at high latitudes for the increase in zonal surface temperature due to increased atmospheric CO2. For example, the CO2‐induced enhancement in the zonal surface temperature for 80°–90°N is more than 3 times as great in the summer as in the winter.
Observations of rapid changes in the orientation and degree of alignment of ice particles along an Earth‐space radio propagation path
Authors: Cox D. C. , Arnold H. W.
Published: April 2008

Rapid changes (<¼s) have been observed in the depolarization of earth‐space radio signals propagating through ice clouds. This paper presents the first observations of the rapid changes in the degree of alignment and in the orientation of the anisotropy axis of the ice particles producing the depolarization. The ice particles appear to be aligned by the intense electric field in thunderstorms and appear to realign rapidly with the new field directions existing after lightning discharges.
Global climatic interpretation of the deuterium‐oxygen 18 relationship for precipitation
Authors: Merlivat Liliane , Jouzel Jean
Published: April 2008

A theoretical model is derived to account for the deuterium‐oxygen 18 relationship measured in meteoric waters. A steady state regime is assumed for the evaporation of water at the ocean surface and the subsequent formation of precipitation. The calculations show that the deuterium and oxygen 18 content in precipitation can be taken as linearly related. From the slope and the intercept (known as the deuterium excess) of the δD‐δ18O linear relationship for precipitation we compute the mean values on a global scale of the evaporating ocean surface temperature and the relative humidity of the air masses overlying the oceans. The deuterium excess is primarly dependent on the mean relative humidity of the air masses formed above the ocean surface. Paleoclimatic data may be obtained by this isotopic method from the analysis of old water and ice samples. A moisture deficit of the air over the ocean, equal to only 10%, in comparison to 20% for modern conditions, is deduced from the deuterium‐oxygen 18 distribution measured in groundwater samples older than 20,000 years.
Contributions of cloud and precipitation particles to the electrical conductivity and the relaxation time of the air in thunderstorms
Authors: Kamra A. K.
Published: April 2008

Electrical conductivity caused by the charged cloud and precipitation particles in thunderstorms has been calculated. It is found that this conductivity may be 1 or perhaps 2 orders of magnitude higher than the clear air conductivity at the same altitude. Since this conductivity increases with the precipitation intensity, liquid water content, electric field, and the electrical charges on the particles, it may show large fluctuations in thunderstorms in both space and time. In spite of this high conductivity, however, it is argued that the corresponding relaxation time may not necessarily be small, being especially so for individual charged particles and for space charge regions of small dimensions. A possible reconciliation of the discrepencies in the earlier studies and the measurements has been discussed on the basis of the present results.
Stratospheric NO2: 1. Observational method and behavior at mid‐latitude
Authors: Noxon J. F. , Whipple E. C. , Hyde R. S.
Published: April 2008

This paper describes a method for obtaining the abundance and altitude of stratospheric NO2 by using ground‐based spectroscopy at twilight. The method is then used to study the behavior of NO2 over Colorado at 40°N; a companion paper discussed observations elsewhere. Large changes in both the abundance of NO2 and in its diurnal variation are commonly seen at mid‐latitude and appear to reflect the role of quasi‐horizontal transport in the stratosphere on a global scale.
Stratospheric NO2: 2. Global behavior
Authors: Noxon J. F.
Published: April 2008

This paper discusses observations of the total daytime stratospheric column abundance of NO2 made over the range in latitude from 40°S to the North Pole. The equatorial abundance is less by a factor of 2 than at mid‐latitude. A summer maximum in the northern hemisphere exists, and the amplitude of the seasonal variation increases from 2 at mid‐latitude to over 6 at 65°N. In winter, when there is not a warming in progress in the stratosphere and there is strong zonal flow, there is an abrupt drop in NO2 abundance near 50°N. The decrease occurs over only a few degrees of latitude where the temperature near 30 km exhibits a poleward drop as well. During a warming, the ‘cliff’ disappears as a result of rapid meridional transport of mid‐latitude stratospheric air into the Arctic.
A note on velocity determination from hydrographic data
Authors: Killworth Peter D.
Published: April 2008

It is demonstrated that geostrophic, hydrostatic, density‐conserving oceanic flow regimes permit evaluation of the absolute velocity field at a point, provided merely that certain gradients of density are known at that point. This differs from previous schemes which involved hydrographic data at many points in the vertical. Inaccuracies in data, however, limit the usefulness of the method.
Relationship between the lipid compositions of marine aerosols, the sea surface microlayer, and subsurface water
Authors: Marty J. C. , Saliot A. , Buat‐Ménard P. , Chesselet R. , Hunter K. A.
Published: April 2008

Aerosols, surface microlayer, and subsurface water samples have been collected during the ‘Midlante’ cruise of the R/V Jean Charcot (May 1974) in the northeastern tropical Atlantic, taking all possible precautions against shipboard contamination. The concentrations of n alkanes, total hydrocarbons, and fatty acids (C12 to C32 were obtained by gas‐liquid chromatography in these aerosol samples as well as for the dissolved and particulate fractions of the microlayer and subsurface waters. The aqueous phase fatty acids are of obvious planktonic origin, but an anthropogenic source cannot be definitely discounted for the aqueous phase n alkanes. On average, fatty acid lipids, n alkanes, and total hydrocarbons are all enriched in the microlayer by factors of 2–5. The three aerosol samples show a strong similarity in composition, and all differ from the corresponding aqueous samples in having lauric acid C12 as the dominant acid instead of C16, typical of planktonic lipids, as found for the water samples. The hydrocarbon distributions of the aerosols, which resemble petroleum‐derived materials, are characteristically different from those of the subsurface and microlayer, which are similar and appear to have a marine origin. The overlying n alkane distributions of all three sample types are similar, however, being generally regular without predominance of n alkanes with n even or odd, and are also quite different from distributions characteristic of terrigenous dust containing hydrocarbons derived from higher plants.
A hybrid parametrical wave prediction model
Authors: Gunther H. , Rosenthal W. , Weare T. J. , Worthington B. A. , Hasselmann K. , Ewing J. A.
Published: April 2008

The development of a numerical wave prediction model incorporating a parametrical wind‐sea model and a characteristic swell model is described. The parametrical model is an extension of an earlier two‐parameter model to the full five Jonswap spectral parameters. An application is presented in which the model is used to hindcast severe wave conditions in the North Sea as part of an engineering study to define long‐term extreme wave statistics for the area. The limitations of the model and the needs for future research are discussed.
A gravity wave‐critical level encounter observed in the atmosphere
Authors: Merrill John T. , Grant John R.
Published: April 2008

The radar and balloon data of Gossard et al. (1970) for an event on August 6, 1969, are examined and calculations presented showing that the wavelike motions observed by the radar are Kelvin‐Helmholtz instabilities; the layer of intense wind shear that surrounds the height of the radar returns is shown to be a critical layer for gravity waves themselves generated higher in the atmosphere. The observed wind and temperature profiles are used in a linear shear instability calculation that shows a narrow band of unstable wavelengths generated at a shear layer some 770 m above the surface; the waves are evanescent upward but transport momentum downward to the critical level at 300 m, where the absortion enhances the wind shear and the reduced Richardson number leads to Kelvin‐Helmholtz instability. The results of the analysis further indicate that the properties of the Kelvin‐Helmholtz instabilities are consistent with the strong wind shear that critical level absorption would produce, and that the motion of the radiosonde balloon can be accounted for by superposing on the mean flow a slowly growing unstable wave. Thus the observations show the entire history of a shear instability event, from generation to absorption at a critical level.
The problem of nighttime stratospheric NO3
Authors: Herman J. R.
Published: April 2008

Detailed calculations of the behavior of the NO3 column content as a function of time after sunset show that it takes nearly 2 hours to increase from daytime values of approximately 1011 cm−2 to nighttime values of 1014 cm−2. These results appear to be in conflict with the measured [NO3] rise time of 40 min after sunset obtained from the 662‐nm absorption data of Noxon et al. (1978). Changes in the rate constants affecting the NO, NO2, NO3, N2O5 system, the atmospheric temperature, and the amount of NO2 are not able to bring the calculated rise time for the NO3 column content into agreement with observations.
Edge waves on complex beach profiles
Authors: Holman R. A. , Bowen A. J.
Published: April 2008

In order to interpret field data in terms of edge wave modes, investigators usually assume that the beach profile is linear, allowing the use of simple analytical solutions for edge wave structure and wavelength. The validity of this assumption is checked by using a numerical model to find the edge wave modes on a typical concave beach. Results show that estimates of edge wave wavelength using the plane beach assumption can be wrong by ±100% at a fixed mean sea level with a further error of ±50% introduced by the tides. Greatly improved estimates can be made if the value of beach slope is chosen to reflect suitably the offshore extent of the edge wave. A rule of thumb for calculating the effective beach slope βe is
, where h is the water depth at distance x′ from shore, L is the edge wave wavelength, and n is the edge wave mode number. The motion of the offshore profile of the edge wave due to a change of tidal elevation is dramatically different on a concave beach than on a plane beach. The tendency for the profile to move offshore for a drop in tide is compensated by the decrease in mean beach slope and hence reduction in wavelength and offshore extent of the wave. For a fixed instrument a drop in tide may lead to a profile shift onshore or offshore or no shift at all. Edge wave damping on a concave beach is shown to change as a function of tide. At low tide the surf zone width is increased while edge wave wavelength is decreased, both factors increasing damping. Thus edge wave spectra taken at low tide may be less energetic than those at high tide, particularly at high frequencies.
Scales of gravity waves generated by instability in tropospheric shear flows
Authors: Greene G. E. , Hooke W. H.
Published: April 2008

Early theoretical models suggested that waves generated by instability of a shear layer in a gravitationally stratified fluid should have wavelengths perhaps 7 times the shear layer thickness. More recent work, however, has discovered that the presence of a rigid lower boundary (such as the earth's surface) introduces new unstable modes at substantially larger wavelengths. In this brief note we show that observations of gravity waves generated by shear instability in the temperate‐latitude troposphere support this more recent conclusion.
Some aspects of the nighttime effect of VLF atmospherics in relation to sea thunderstorm
Authors: Sarkar S. K. , Bhattacharya A. B.
Published: April 2008

The phenomenon of sea thunderstorm effect on the nighttime records of VLF atmospherics at 10 and 20 kHz over the tropical station Calcutta (22°34′N, 88°24′E) has been examined for the period June 1976 to May 1978. The disturbance reveals first an enhancement and then a large fall, and in between these two there is a nearly steady level. This variation is named the ‘nighttime effect.’ Important results obtained from the analysis of 204 such effects are that (1) most of the nighttime effects appear to cluster around midnight, (2) a high correlation exists between the duration of enhancement and fall, and (3) magnitudes of enhancement and fall are greater at 10 kHz than those at 20 kHz. All the characteristic features of this nighttime effect and their probable origins have been critically analyzed and discussed in relation to sea thunderstorms of the adjacent Bay of Bengal.
Interannual atmospheric variability and associated fluctuations in Arctic Sea ice extent
Authors: Walsh John E. , Johnson Claudia M.
Published: April 2008

Observational data are used to evaluate quantitatively the relationships between arctic sea ice extent and the high‐latitude atmospheric circulation on the seasonal time scale. The sea ice data set contains 300 monthly grids of observed sea ice concentrations. The atmospheric variables include sea level pressure, surface temperature, 700‐mbar height, and 700‐mbar temperature. Statistically significant correlations between the dominant modes of atmospheric and sea ice variability are found at atmospheric lags of up to 2 months and ice lags of up to 4 months. The surface temperature field generally shows the strongest relationship to the sea ice fluctuations. The strongest correlations between ice anomalies and subsequent atmospheric fluctuations are found in the autumn months of increasing ice extent. Evidence of ice‐atmosphere coupling is also found in the mid‐latitude fields of the North Atlantic. The meteorological difference fields derived from years of extreme ice extent contain statistically significant pressure differences of up to 10–15 mbar, surface temperature differences of up to 8°–9°K, and 700‐mbar height differences of up to 16–18 decameters. The anomaly centers tend to migrate seasonally with the ice edge. The statistical predictability of large‐scale sea ice fluctuations decays to the level of no skill at a forecast interval of 5–6 months.
Modification of the atmospheric polonium 210 to lead 210 ratio by volcanic emissions
Authors: Lambert G. , Buisson A. , Sanak J. , Ardouin B.
Published: April 2008

Volcanic gases are very rich in long‐lived radon daughters, especially in 210Po. Thus more than 50×103 Ci per year of 210Po are injected into the troposphere by a normal volcanic activity, and more than 1×103 Ci per year into the stratosphere by volcanic explosions. These fluxes should account for one half of the 210Po content in both of these reservoirs. On the contrary the volcanic sources of 222Rn and 210Pb are generally negligible with regard to the soil production. This new result could explain most of the discrepancies observed by comparing the activity ratios of the different radon daughters, including the existence of 210Po/210Pb figures superior to one (overequilibriums). Stratospheric aerosol residence times calculated on this basis are found to be shorter than the previous figures.
Calculation of absolute velocities from different parameters in the western North Atlantic
Authors: Schott Friedrich , Zantopp Rainer
Published: April 2008

The method proposed by Stommel and Schott (1977) to calculate absolute currents from geostrophic currents and isopycnal slopes is reformulated to include compressibility for the use of in situ density and temperature. It is found that the compressibility terms in the equation based on in situ density are quite important already in the upper few hundred meters. For a data set from the western North Atlantic, absolute current calculations are presented for in situ density, potential density, temperature, potential temperature, salinity, and specific volume anomaly, and they all yield similar results. The use of specific volume anomaly in Schott and Stommel's (1978) analysis does not seem to be the cause of the observed depth tendency.
The space‐time structure and variability of the shelf water‐slope water and Gulf Stream surface temperature fronts and associated warm‐core eddies
Authors: Halliwell George R. , Mooers Christopher N. K.
Published: April 2008

The space‐time structure and variability of three thermal features on the surface of the Northwest Atlantic—the shelf water‐slope water front; the Gulf Stream front; and warm‐core, anticyclonic eddies— were examined between September 1, 1975, and August 31, 1977, using weekly satellite‐derived charts of surface temperature fronts. The temporal and spatial correlation scales of both the shelf‐slope and Gulf Stream fronts were about 2 weeks and 80 km, respectively. The rms amplitude of both fronts increased from about 25 to 80 km in the first 1,000 km northeastward from Cape Hatteras. The dominant Gulf Stream meanders had wavelengths of about 320 km and periods of 7–8 weeks, and they propagated downstream jit a speed of about 6 cm/s. The warm‐core eddies averaged about 100 km in diameter and propagated southwestward from Georges Bank at an average speed of 6 cm/s; they decreased hi diameter from about 120 to 90 km and increased in speed from about 4 to 7 cm/s in moving from the Georges Bank‐to‐Hudson Canyon subdomain to the Hudson Canyon‐to‐Cape Charles subdomain. Some large Gulf Stream meanders induced perturbations of the shelf‐slope front. Eddies forced seaward perturbations of the front, which propagated southwestward with the eddies. (There were more rapidly propagating disturbances which also moved southwestward along the shelf‐slope front; they may have been due to coastally trapped waves.) There was significant interannual variation in the mean position of the Gulf Stream front and the number and intensity of warm‐core eddies shed by the Stream, though the correlation scales of its front did not change. Consequently, there were substantial interannual variations in the inferred entrainment of shelf waters by warm‐core eddies. Furthermore, the correlation scales of the shelf‐slope front had interannual variation. The results of this study agree with earlier, more limited estimates, and they extend the statistical analyses to the space‐time continuum of long waves and meanders with the aid of wave number‐frequency spectra and empirical orthogonal functions. These analyses quantify the broadbanded nature of the various perturbations and their interactions. Thus a holistic view of the principal surface thermal features of the Northwest Atlantic, and their interactions, is provided.
A reexamination of Bagnold's Granular‐Fluid model and bed load transport equation
Authors: Bailard James A. , Inman Douglas L.
Published: April 2008

Bagnold's bed load transport model is reexamined by using only the momentum equation, the Coulomb yield criteria and the definition of the rate of energy dissipation for a shearing fluid. The general form of Bagnold's bed load equation is rederived but with two specific differences: Coulomb's yield criteria tan ϕ = T/P holds only at the interface between regions of shearing and nonshearing grains, and the ratio of the mean to maximum granular velocity Ū/Umax enters as an additional factor.
Observations of stratified flow past Three‐dimensional barriers
Authors: Baines P. G.
Published: April 2008

Experiments on stratified flow at large Reynolds numbers over barriers with gaps, towed along the bottom of a long tank, are described. The primary purpose of the observations was to determine the circumstances under which fluid flows over the barrier or is deflected horizontally around the barrier through the gap. A range of gap widths (including zero) was used, and the barrier had ‘Witch of Agnesi’ profile with height ∼ half width. For the two‐dimensional barrier (i.e., zero gap), blocked fluid was observed upstream if F = U/Nh < 0.5. For the same barrier with a gap, if F < 0.5, all the fluid incident below a certain height zs ( 0.5 all (or almost all) of the fluid incident on the barrier flowed over it, and the motion was predominantly two‐dimensional in the vertical plane.
The effect of the sea breeze circulation on surface ozone levels at Wallops Island, Virginia
Authors: Parsons C. L. , Williams M. E.
Published: April 2008

Surface measurements of windspeed, direction, and ozone concentration collected at Wallops Island, Virginia, during the summers of 1977 and 1978 are analyzed to study the effects of the dominant mesoscale sea breeze circulation on the local photochemical oxidant levels. A bimodality in the atmospheric dynamics is linked to systematic variations in ozone concentration. It is concluded that during certain phases of the two circulation modes, increased wind speed reduces the resistance of the earth's surface to the deposition of ozone, and decreased ozone concentration levels result. For other phases, light winds occur, signifying high resistance to deposition and high ozone levels. This modulation by the local dynamics is a major impediment for pollutant studies in coastal environments, especially those centering on transport, because it tends to mask other processes that may be occurring.
Sulfur and halogen chemistry of the stratosphere and of volcanic eruption plumes
Authors: Lazrus A. L. , Cadle R. D. , Gandrud B. W. , Greenberg J. P. , Huebert B. J. , Rose W. I.
Published: April 2008

The major eruption of Volcan de Fuego caused an enhancement of 1.6×109 kg of SO4= in the stratosphere 6 months after the eruption. Measurable changes in nitric acid, vapor and particulate chloride were not observed. Subsequent data suggests that HCl was not injected into the stratosphere. The first simultaneous measurements of halogen and sulfur content of gases and particles in explosive eruption plumes is reported. The average percents of elements in particles were sulfur, 2.5±2.1; chlorine, 18±12; and fluorine, 38±29. The average molecular ratio of HCl/SO2 and HCl/HF were 0.41±0.26 and 14±12 in the Guatemalan eruption plumes.
Circumpolar measurements of ozone, particles, and carbon monoxide from a commercial airliner
Authors: Pratt R. , Falconer P.
Published: April 2008

Trace constituent data are presented from the unique flight of an airliner around the world over both poles. Relatively high resolution and simultaneous measurements of ozone, carbon monoxide, light‐scattering particles, condensation nuclei, and meteorological parameters were obtained. The mutual variations of the data in the polar stratospheres, and in the tropical upper troposphere, are discussed in their meteorological setting. The data from the Arctic lower stratosphere are consistent with a tropospheric source of condensation nuclei, but not of carbon monoxide. Carbon monoxide mixing ratios in the Antarctic stratosphere averaged 44 ppbv. In the tropical troposphere they averaged 66 ppbv over the Pacific versus 89 ppbv over Africa. A local area of higher concentration (115 ppbv) was encountered over tropical Africa; its possible relation to carbon monoxide production by vegetation and deep convection is discussed. Evidence was found in the tropical upper troposphere of distinct boundaries between air masses of different temperature, ozone content, and particle content.
The probability distribution of the predicted CFM‐induced ozone depletion
Authors: Ehhalt D. H. , Chang J. S. , Butler D. M.
Published: April 2008

It is argued from the central limit theorem that the uncertainty in model predicted changes of the ozone column density is best represented by a normal probability density distribution. This conclusion is validated by comparison with a probability distribution generated by a Monte Carlo technique. In the case of the CFM‐induced ozone depletion, and based on the estimated uncertainties in the reaction rate coefficients alone the relative mean standard deviation of this normal distribution is estimated to be 0.29.
Tropospheric NO measurements up to 7 km
Authors: Schiff H. I. , Pepper D. , Ridley B. A.
Published: April 2008

Mixing ratios of nitric oxide were measured by the chemiluminescence method as part of the 1977 and 1978 Global Atmospheric Measurement Experiment of Tropospheric Aerosols and Gases (Gametag) missions. Since the method is not highly specific it can provide only upper limits for the NO mixing ratio. Values for maritime air were ≤30–40 parts per trillion by volume (pptv) and showed little variation with latitude or whether or not the measurements were taken in or above the boundary layer. Over continental North America mixing ratios in unpolluted air were ≤40–60 pptv, independent of altitude. Values in excess of 1 ppbv were obtained in industrial regions, over forest fires, and even over small Eskimo villages in northern Canada. In polluted air the values decreased with an increase in altitude.
A review of multiparameter radar observations of precipitation
Authors: Rogers R. R.
Published: April 2008

From the earliest years of radar meteorology, efforts have been devoted to multiparameter observations: the measurement of one or more signal properties, ordinarily in addition to the signal intensity, to give added information about the precipitation. Studies employing variable polarization or Doppler frequency measurement were among the first such techniques and over the years have proved fruitful in terms of the information provided. During the past decade there has been such an increase in the use of Doppler radar in meteorological research that radar‐measured wind fields are becoming nearly as routine as reflectivity fields. Research has continued in variable polarization techniques, which appear to provide a means of distinguishing remotely between various precipitation types. Investigations of the correlation between the copolarized and cross‐polarized components of the received signal have given new insight into the falling behavior of precipitation particles. A great deal of new information will evidently be made available by combining coherent signal processing techniques with variable polarization measurements.
URSI Symposium workshop report: Multiple‐parameter radar measurements of precipitation
Authors: Hall M. P. , Atlas D. , Barge B. L. , Crane R. K. , Mon J.‐P. , Rogers R. R. , Seliga T. A.
Published: April 2008

A feature of the URSI Commission F Open Symposium on Multiple‐Parameter Radar Measurements of Precipitation was a lively workshop session covering each of the three broad topic areas of the meeting. Though reports of successful workshop sessions can never be fully comprehensive, this report covers the main points discussed in the three areas.