bluuebunny/crossref_metadata_2025 huggingface dataset:
Ocean wave‐radar modulation transfer functions from the West Coast Experiment
Authors: Wright J. W. , Plant W. J. , Keller W. C. , Jones W. L.
Published: February 2008

Short gravity‐capillary waves, the equilibrium, or the steady state excitations of the ocean surface are modulated by longer ocean waves. These short waves are the predominant microwave scatterers on the ocean surface under many viewing conditions so that the modulation is readily measured with CW Doppler radar used as a two‐scale wave probe. Modulation transfer functions (the ratio of the cross spectrum of the line‐of‐sight orbital speed and backscattered microwave power to the autospectrum of the line‐of‐sight orbital speed) were measured at 9.375 and 1.5 GHz (Bragg wavelengths of 2.3 and 13 cm) for winds up to 10 m/s and ocean wave periods from 2–18 s. The measurements were compared with the relaxation‐time model; the principal result is that a source of modulation other than straining by the horizontal component of orbital speed, possibly the wave‐induced airflow, is responsible for most of the modulation by waves of typical ocean wave period (10 s, say). The modulations are large; for unit coherence, spectra of radar images of deep‐water waves should be proportional to the quotient of the slope spectra of the ocean waves by the ocean wave frequency.
Modulation of sea surface radar cross section by surface stress: Wind speed and temperature effects across the Gulf Stream
Authors: Weissman D. E. , Thompson T. W. , Legeckis R.
Published: February 2008

During the past several years, many radars (Moskowitz, 1973; Larson et al., 1976) have observed the distinct and interesting features associated with the Gulf Stream and its boundaries. Some of these Gulf Stream radar features are small scale, with dimensions comparable to and slightly greater than long gravity waves. Other features are larger, with dimensions much greater than the length of long gravity waves. This study describes radar cross‐section variations within the Gulf Stream and just outside, seen with a ‘scatterometer’ type measurement. The significant features of these radar cross‐section data were that the Gulf Stream always had a higher cross section per unit area (interpreted here as a greater roughness) than the water on the continental shelf. Also, a steep gradient in cross section often was seen at the expected location of the western boundary. There also were longer scale (10–20 km) gradual fluctuations within the stream. These roughness variations are correlated with the surface shear stress that the local wind imposes on the sea. By using the available surface truth information regarding the wind speed and direction, an assumed Gulf Stream velocity profile and high‐resolution ocean surface temperature data obtained by the very high resolution radiometer on board a NOAA polar‐orbiting satellite, profiles of sea surface stress were calculated for comparison with radar cross‐section data. This study demonstrates that the measured radar cross‐section variations are correlated with computed surface stress and that both surface‐air temperatures and surface winds are important factors in determining surface stress and radar cross section.
Particle size dependence of alkali and alkaline Earth metal enrichment in marine aerosols from Bermuda
Authors: Hoffman E. J. , Hoffman G. L. , Duce R. A.
Published: February 2008

Three cascade impactor samples were collected from a 20‐m‐high tower on the southeastern coast of Bermuda. These samples were analyzed for Na, K, Ca, Mg, and Fe by atomic absorption spectrophotometry. When the alkali‐alkaline earth metal concentrations are corrected for a soil‐derived component, utilizing the atmospheric Fe concentrations, Mg, Ca, and Na are found to be present in the same relative abundances as in seawater for all particle sizes sampled. Potassium also shows no deviation from a bulk seawater composition for particles with radii greater than ∼0.5 μm. However, excess K above that expected from either a bulk seawater or soil source is observed on particles with radii less than ∼0.5 μm. While oceanic chemical fractionation processes during bubble bursting may be responsible for this excess small particle K, it is most likely due to long‐range transport of K‐rich particles of terrestrial vegetative origin.
Measurement of stratospheric water vapor by cryogenic collection
Authors: Pollock W. , Heidt L. E. , Lueb R. , Ehhalt D. H.
Published: February 2008

Cryogenic collection of water vapor and subsequent volumetric measurement in the laboratory were used to measure stratospheric water vapor concentrations. Also measured were the deuterium and tritium content of the water samples. The isotopic measurements provide information not only on contamination during sampling, but also on the origin or previous history of the water vapor. The stratospheric H2O profiles show an increase with altitude which is weak for the high latitudes and steeper around 30°N. Profiles of total hydrogen (the sum of H2O, CH4, and H2) show no significant vertical gradients indicating that the H2O increase was essentially caused by the vertical decrease in the CH4 mixing ratio. Isotopic measurements from one flight over Alaska indicate the same.
Sources and sinks of atmospheric H2S
Authors: Jaeschke Wolfgang , Claude Hans , Herrmann Jürgen
Published: February 2008

In recent years, trace concentrations of H2S have been measured employing a fluorescence analytical method. Automatization of the method caused enhancement of its analytical capacity. Thus it became possible to observe variations of the H2S concentration during days, months, and years at different sampling sites. The obtained data showed that swamps and tidal flats are natural sources of H2S. Their contributions to the atmospheric sulfur cycle are compared with those of volcanic activity measured at Etna (Italy) and with those of anthropogenic activity measured in the environment of Frankfurt (Germany). The observed daily and seasonal variations of the H2S concentrations showed that photochemical reactions are probably the main sink of atmospheric H2S. The measured data of a vertical H2S concentration profile were used to calculate a mean removal coefficient for H2S of 2.27×10−5s−1, corresponding to a mean lifetime of 12.2 hours. The removal coefficient is compared with the reaction constants of some photochemical processes which may determine the atmospheric removal of H2S. This comparison leads to the conclusion that the reaction of H2S with OH radicals is the main sink of atmospheric H2S.
Are the past variations of the stratospheric sulfate burden recorded in central Antarctic snow and ice layers?
Authors: Delmas Robert , Boutron Claude
Published: February 2008

Thirty‐two snow samples, taken from a pit dug at Dome C (central Antarctica) and covering a continuous time period of about 100 years from 1880 (±5 years) up to the present, have been subjected to sulfate analysis. The concentrations determined range from 50 to 150·10−9g g,−1 of snow, with no apparent increase because of global sulfur pollution. The more important fluctuations observed on the sulfate concentration profile seem to be linked to major volcanic eruptions which occurred in the southern hemisphere during the studied time period, in particular Krakatoa in 1883 and Agung in 1963. The experimental and calculated contributions of this last eruption to the sulfate deposition in Antarctica agree satisfactorily. The sulfate background (about
of the overall sulfate deposition during the last 100 years) has most likely a marine origin (‘excess sulfate’.) It is suggested that the past variations of the stratospheric sulfate burden are recorded in Antarctic snow and ice layers and that they could be reconstructed by analyzing the sulfate content in deep ice cores.
Project Gametag: An overview
Authors: Davis D. D.
Published: February 2008

Presented in this first paper of the Gametag series is an overview of the Gametag program. This presentation is intended to provide the reader with background information about several of the important characteristics of the program. These include (1) the sampling strategy and general philosophy of the program; (2) the field‐sampling track; (3) the nature of the sampling platform; (4) a listing of instruments and measurements recorded; (5) Gametag data‐archiving procedures; and (6) a listing of participating institutions, scientific team members, and principal investigators.
Free tropospheric/boundary‐layer airborne measurements of H2O over the latitude range of 58°S to 70°N: Comparison with simultaneous ozone and carbon monoxide measurements
Authors: Routhier F. , Davis D. D.
Published: February 2008

Presented in this paper are the H2O data collected during the 1977 and the 1978 Gametag (Global Atmospheric Measurements Experiment of Tropospheric Aerosols and Gases) field experiments. These data primarily reflect sampling occurring during the horizontal flight legs, involving altitudes of 5–6.5 km (free troposphere) and those in the atmospheric boundary layer at altitudes of ≤2 km. The latitude range covered was 70°N to 58°S. Approximately two thirds of the data were recorded over the open Pacific Ocean with the remaining one third being recorded over continental areas (e.g., Canada and Alaska). The H2O results show that very large variations in the level of this trace gas can occur within the free troposphere over very small geographical distances. They also indicate that over some regions of the Pacific Ocean very low levels of H2O can be found even at tropical and subtropical latitudes. The comparison of Gametag data with existing global dew point compilations suggests that some of the radiosonde middle tropospheric dew point profiles may be significantly in error, the radiosonde results being too high. Comparisons of the Gametag O3 and dew point/H2O data have shown that for the middle troposphere these two variables very frequently are negatively correlated. Comparisons between O3 and CO, when carried out within a given hemisphere, do not show a significant negative or positive correlation. On the basis of our findings, we have concluded that stratospheric/tropospheric dynamic exchange processes, directly and/or indirectly, play a controlling role in defining the tropospheric O3 source strength.
Free tropospheric and boundary‐layer airborne measurements of ozone over the latitude range of 58°S to 70°N
Authors: Routhier F. , Dennett R. , Davis D. D. , Wartburg A. , Haagenson P. , Delany A. C.
Published: February 2008

Reported here are O3 data recorded during the 1977 and 1978 Gametag field experiments. Nearly two thirds of these data were recorded in the free troposphere over the altitude range of 5–6.5 km. The remaining one third were collected in the atmospheric boundary layer, typically 0.3–1 km above the surface terrain. The latitude range covered by these measurements was 58°S to 70°N and involved flight operations over northern Canada, Alaska, the southeastern/central Pacific (northern hemisphere), and the central/western Pacific in the southern hemisphere. This data base is unique in that all ozone measurements were recorded on the same set of three ozone analyzers, on a single aircraft platform, and over a short time span. Key observations include (1) systematically higher average free tropospheric O3 levels in the northern versus southern hemisphere with the global minimum in ozone occurring at tropical latitudes; (2) extensive O3 layering within the free troposphere over large geographical areas of the northern hemisphere and, to a much lesser extent, remote areas of the southern hemisphere; (3) boundary‐layer O3 concentration levels which were consistently lower than free tropospheric O3 levels in remote areas of the northern hemisphere but only slightly lower than those levels observed in the southern hemisphere; and (4) the finding in April/May 1978 of a latitudinal zone, 13°S to 2°N, virtually devoid of boundary layer O3. A comparison of these data with those of other investigators, together with a discussion of the relevancy of these observations to our present understanding of the tropospheric O3 budget, is presented.
Iodine: Its possible role in tropospheric photochemistry
Authors: Chameides W. L. , Davis D. D.
Published: February 2008

A detailed study of the photochemistry of iodine and its oxides indicates that iodine species may play an important, but heretofore ignored, role in the tropospheric photochemical system. Methyl iodide, often observed in the marine troposphere with an average concentration of 5–10 ppt (v/v), is photolyzed and thereby produces I atoms. Chemical interactions with O3, HxOy, and NOx cause I to be converted to other inorganic compounds such as IO, HOI, IONO2, and I2. The production of these species and their subsequent recycling back to I can lead to the catalytic removal of tropospheric O3, the enhancement of the NO2/NO ratio, the destruction of HxOy free radicals, and the conversion of HO2 to OH. Ultimately, tropospheric inorganic iodine (IX) is removed by heterogeneous processes. Calculations using a numerical model to simulate tropospheric photochemistry indicate that iodine may have a strong impact upon the atmospheric O3‐NOx‐HxOy system. The magnitude of these effects is dependent upon the value of several uncertain rate constants and the primary source distributions of CH3I and other organic and inorganic iodine compounds.
The mechanism for dry deposition of ozone to seawater surfaces
Authors: Garland J. A. , Elzerman A. W. , Penkett S. A.
Published: February 2008

A simple model, in which deposition is limited by diffusion through a thin laminar film of water, has successfully described the deposition of several gases to the sea. However, the deposition velocity of ozone to seawater is 10–30 times greater than this model predicts. This enhancement is attributed to significant reactions of ozone with halides and other components of seawater within the laminar surface layer, and a modified version of the model for ozone, and possibly other reactive gases, is proposed. To test the model, comparisons were made of predicted and observed deposition velocities for ozone to solutions of sodium sulphite and nitrite. Measurements of the rate constants for the reaction of ozone with these solutions and with some components of seawater were made with a stopped flow apparatus. The reaction with iodide was too rapid for direct observation, but the rate constant was inferred from measurements of the deposition of ozone to iodide solutions. According to the model, iodide makes a substantial contribution to the deposition of ozone to seawater, but an additional, unidentified reaction is necessary to explain fully the deposition rate. A surfactant species may well be involved. The model indicates that the ozone is destroyed and the oxidation products produced in the top few microns of the sea. The production of molecular iodine at the surface may have significant geochemical consequences.
Experimental sea slicks: Their practical applications and utilization for basic studies of air‐sea interactions
Authors: Hühnerfuss Heinrich , Garrett W. D.
Published: February 2008

Practical applications of organic surface films added to the sea surface date back to ancient times. Aristotle, Plutarch, and Pliny the Elder describe the seaman's practice of calming waves in a storm by pouring oil onto the sea [Scott, 1977]. It was also noted that divers released oil beneath the water surface so that it could rise and spread over the sea surface, thereby suppressing the irritating flicker associated with the passage of light through a rippled surface.

From a scientific point of view, Benjamin Franklin was the first to perform experiments with oils on natural waters. His experiment with a ‘teaspoonful of oil’ on Clapham pond in 1773 inspired many investigators to consider sea surface phenomena or to conduct experiments with oil films. This early research has been reviewed by Giles [1969], Giles and Forrester [1970], and Scott [1977]. Franklin's studies with experimental slicks can be regarded as the beginning of surface film chemistry. His speculations on the wave damping influence of oil induced him to perform the first qualitative experiment with artificial sea slicks at Portsmouth (England) in October of 1773. Although the sea was calmed and very few white caps appeared in the oil‐covered area, the swell continued through the oiled area to Franklin's great disappointment.
Southern hemisphere sea surface temperature variability and apparent associations with Australian rainfall
Authors: Streten N. A.
Published: February 2008

A brief review is given of the spatial and temporal pattern of sea surface temperature (SST) observations for the southern hemisphere. An analysis is made of 20 years (1950–1969) of observations of mean monthly SST for each degree square along the shipping routes, and relative variability is assessed on seasonal, latitudinal, and geographical bases. Highest variability occurs in oceanic regions of the western boundary currents, of current confluence, of upwelling, and also of convergence of low‐level atmospheric flow, notably in the central South Pacific. Within the data limitations the relative areas of above‐ and below‐normal SST are measured for selected tropical ocean regions near Australia for 6 years of extremely high and low extent of annual continental rainfall and for transitions from very dry years to very wet years and vice versa. The 3 extremely dry years are found to occur with an average reduction of some 14% in the area of above‐normal SST as compared with the 3 extremely wet years; the corresponding regional seasonal mean atmospheric pressure is above normal in dry years and below normal in wet years. The greatest interannual changes in rainfall extent are also accompanied by corresponding transitions in the area of above‐normal SST. Evidence suggests that the extent of above‐normal SST over the whole ocean (including higher latitudes) surrounding continental Australia may be closely associated with extreme rainfall years.
Electric field structure in an active part of a small, isolated thundercloud
Authors: Winn W. P. , Moore C. B. , Holmes C. R.
Published: February 2008

A balloon carrying an electric field meter and a standard meteorological radiosonde rose into a relatively small, isolated thunderstorm in central New Mexico on July 16, 1977. The electric field, E, versus altitude between 3200 m (surface) and 7000 m above sea level can be explained reasonably well by the following charge distribution: (1) a 130 m thick layer of positive charge just above the surface with a density of 1.7 × 10−9 C/m3; (2) a localized 1 C of positive charge moving downward on rain with a velocity of 8 m/s at a horizontal distance of 420 m from the balloon; (3) a 1‐km thick ‘layer’ of negative charge between 4800 and 5800 m above sea level with a density of about −5 × 10−9 C/m3. This negative charge spanned a temperature range of about −2 to −5°C. Between 7000 and 10,000 m above sea level, the balloon was near the edge of the cloud where E was low and principally horizontal. Above 10,000 m the balloon ascended into an anvil cloud that was apparently positively charged.
Production of nitrate ions and other trace species by lightning
Authors: Hill R. D. , Rinker R. G.
Published: February 2008

Results of a theoretical determination of HNO2 and HNO3 productions by lightning are presented, and productions of OH, CO, and N2O which relate to questions of the validity of the model and chemistry used in the calculation are also discussed. It is finally concluded that the direct productions of HNO2 and HNO3 by lightning are too small to have been observed in measurements of the NO3− content of rain water. This result appears to be in accord with experiment.
Ocean circulation and fronts as related to ice melt‐back in the Chukchi Sea
Authors: Paquette Robert G. , Bourke Robert H.
Published: February 2008

In summer at the edge of the retreating ice pack in the Chukchi Sea, a sharp temperature and salinity front is formed as the result of ice melt by warm surface water from the south. Beneath this front another front is present, formed from the juxtaposition of the resident winter bottom water under the ice and a water transitional between it and warm summer water flowing northward from Bering Strait. The two fronts may be coincident where the current shears parallel to the ice with low to moderate lateral mixing. They may also be widely separated in areas where the current impinges normal to the ice, most often within ice embayments. On the flanks of rapidly moving streams, wedge‐like frontal interfaces in the lower layer are likely to be found. These fronts are often rich in temperature fine structure. The ice melt‐back patterns and the various frontal arrangements appear to be controlled by steering of the currents by bottom bathymetry.
Low frequency fluctuations off the Natal coast
Authors: Schumann E. H.
Published: February 2008

Conditions on the continental shelf off the Natal coast are described in terms of the effect on fluctuations in currents, temperature, and (to a limited extent) sea level. The results of measurements made at four mooring points along the coast are then analyzed for fluctuations in the 2‐ to 20‐day period range. The longshore wind component is shown to play a major role in the circulation dynamics; however, the effect of topographic variations and the associated flow of the Agulhas Current also serve to produce markedly differing regimes. Thus in the northern region it is found that the currents are almost entirely wind dominated, while further south, nonlocal signals propagating into the regions produce a different form of response. The measurements are not comprehensive enough to allow more detailed investigations as to the nature of these signals.
Tidally induced ‘upwelling’ by the Great Barrier Reef
Authors: Thompson Rory O. R. Y. , Golding T. J.
Published: February 2008

The Great Barrier Reef is similar to some other coral reefs in growing right up to the edge of the shelf in a region of nutrient‐poor surface water but large tides. It is suggested that the resultant strong tidal currents suck in nutrient‐rich water from the depth where the tidal flow speed drops to the fastest internal wave speed. The nutrients could encourage the reef to grow vigorously at the edge of the shelf. Some observations in Cook's Passage (14°32′S, 145°34′E) were made to test the concept and are encouraging.
Time series search for trend in total ozone measurements
Authors: St. John D. S. , Bailey S. P. , Fellner W. H. , Minor J. M. , Snee R. D.
Published: February 2008

Time series analysis of monthly average total ozone measurements at 37 Dobson stations throughout the world shows that no ozone depletion has occurred at these stations through 1979. The trends at the 14 stations with records from 1958–1979 show an average increase of (1.5±1.0)% (95% confidence). The trends at the other 23 stations with shorter data records show an average increase of (1.0±1.7)%; the choice of stations is not critical to the conclusions. The average change is the sum of all long‐term global trends. The confidence limits are calculated from the variation among stations and include all effects that differ from station to station. A comprehensive evaluation of model adequacy indicated that variations in the statistical methodology have only small effects on the results. The uncertainty in the observed average change decreases with each year's new data. It is concluded that a downward trend from whatever cause equal to half that hypothesized by current atmospheric models as due to chlorofluorocarbons (CFC's) would be detected. These stations provide a good early warning of any depletion at the measuring stations that might be due to CFC's.
An estimate of absolute geostrophic velocity from the density field in the northeastern Pacific Ocean
Authors: Coats Douglas A.
Published: February 2008

A pair of hydrographic sections (35°N, 155°W) were analyzed to compute absolute velocity by using a variation of the technique advanced by Stommel and Schott (1977). Absolute velocity is determined from an integrated form of the potential vorticity equation by a technique suggested by Davis (1978). This study is the first application of this technique that allows a direct comparison between the uncertainty in estimating a smooth density field and the amount of imbalance in the system of model equations. Because the amount of incompatibility (imbalance) in the system of equations is far smaller than is allowed by the uncertainty in defining the smooth field, the model equation is considered adequate for this set of data. Below 400 m, the nearly constant zonal isopycnal slope indicates that potential vorticity is uniform on isopycnal surfaces. Since the method depends on resolving flow directions from the intersection of isopycnals and surfaces of constant potential vorticity, the absolute velocity is indeterminate in this region. The model equation does, however, constrain the structure of the meridional density field and requires a poleward shift in the latitude at which successively deeper isopycnals reach their maximum depth. The fact that this poleward translation can be predicted over several degrees of latitude suggests potential vorticity is uniform over a substantial portion of the North Pacific subtropical gyre. This poleward translation of the density field is an aspect of subtropical density fields, in general, and occurs in conjunction with a translation in the field of geopotential anomaly. It is directly related to the curvature in the deep portion of the beta spiral.
Some aspects of the coupling between radiation, chemistry, and dynamics in the stratosphere
Authors: Hartmann Dennis L.
Published: February 2008

A number of mechanisms involving interaction between radiation, photochemistry, and dynamics that may affect the thermal compositional or dynamical structure of the stratosphere are discussed. The effect of coupling between radiative transfer, photochemistry, and advection of ozone by stratospheric winds on the effective relaxation rate of temperature perturbations is illustrated through the use of four examples. It is shown that for the vertical structure typical of planetary waves, ozone fluctuations act to hasten the relaxation of temperature perturbations in the upper stratosphere and to slow the relaxation in the lower half of the stratosphere. Next, the coupling between chemical sources and sinks of ozone and advection of air by motions is discussed. A simple Lagrangian model is employed and related to results from Eulerian model studies. Emphasis is placed upon the large eddy transports produced at the transition level between dynamical and photochemical control of ozone and also upon the mean ozone increases which eddies can produce in regions where there are sharp gradients in both the equilibrium ozone mixing ratio and the relaxation time scale for ozone perturbations. Finally, the variations of the effective relaxation rate of temperature perturbations are shown to be potentially important in determining the mean structure of the stratosphere during the winter season. These variations in the relaxation of temperature perturbations result from ozone variations produced both by chemistry and motions. In particular, a rapid increase in the effective damping rate of planetary waves between the middle and upper stratosphere leads to a rapid increase with height of eddy heat transports produced by the coupling between radiation and dynamics. This in turn can produce a significant modification of the zonal mean structure of the upper stratosphere.
Stratospheric‐mesospheric midwinter disturbances: A summary of observed characteristics
Authors: Labitzke Karin
Published: February 2008

The midwinter temperature changes in the mesosphere and stratosphere are described, using conventional and satellite data. It is shown that over the northern hemisphere the so‐called stratospheric midwinter warmings extend into the upper mesosphere. The differences between both hemispheres are pointed out. The activity of the planetary‐scale waves during the last 16 northern winters and the importance of the amplification of height wave 1 before the beginning of a major warming are discussed. It is shown that during the northern winters the structure of the quasi‐stationary waves shows an irregular interannual variability that can be connected with the variability of the polar stratospheric temperatures. In contrast, the southern stratospheric winters are rather regular.
Aspects of stratospheric sudden warmings studied from a transformed Eulerian‐mean viewpoint
Authors: Palmer T. N.
Published: February 2008

The stratospheric major warmings of 1979 and 1980 are discussed from a transformed Eulerian‐mean viewpoint. For both warmings a high latitude polar night jet core existed prior to the circulation reversal. It is suggested that the position of this jet core was important in the development of the warmings, and some theoretical justification for this is given in terms of the relation between the norm of the Eliassen‐Palm flux and the refractive index of the zonal mean flow. The possibility that the position of the jet arose from the decay of an earlier warming pulse is discussed. Some comparison is made between transformed and standard Eulerian‐mean diagnostics, and from these it is concluded that the transformed picture indeed fulfills expectations that it is closer to a Lagrangian description of the stratosphere during warming conditions. Comparison is also made between the observed warmings and recent numerically simulated warmings. Differences are found, notably in the diagnosis of high latitude acceleration in the 1980 prewarming period and in the position of appearance of the zero wind in the 1979 warming period. The possibility that preconditioning of the zonal flow by an earlier warming pulse is an important aspect in the development of an atmospheric major warming, which may explain the discrepancies with model results, is discussed. Support is drawn from earlier studies of stratospheric warmings.
Parameterization of linear wave chemical transport in planetary atmospheres by eddy diffusion
Authors: Strobel Darrell F.
Published: February 2008

Two‐dimensional transport by linear waves is parameterized by wave velocity and temperature correlations and nonconservative properties of the atmosphere in a residual Eulerian framework. Explicit expressions derived for the eddy tracer flux vector are written in eddy diffusion tensor form, but it is demonstrated that strong coupling of chemistry and temperature through the rate constants, as is the case for ozone, requires additional terms proportional to the mixing ratio and not to its gradient. A variety of limiting cases are discussed. In the residual Eulerian framework the Kyz, Kzy components are nonzero for a nonconservative atmosphere and/or a reactive tracer. Tracers have common transport coefficients in the limit where their chemistry is negligible in comparison to transience. It is shown that the usual one‐dimensional vertical eddy diffusion continuity equation is rigorously valid only when the temperature dependence of the rate constants is negligible and the tracer has strong vertical stratification relative to its horizontal variability.
Layered lightning activity
Authors: MacGorman Donald R. , Few A. A. , Teer T. L.
Published: February 2008

The horizontal extent of lightning channels reconstructed acoustically from several storms is significantly larger than the vertical extent. Furthermore, an examination of all the reconstructed lightning structure in each of three storms, one in Arizona, one in Colorado, and one in Florida, shows that the lightning activity tends to occur in layers 2–3 km thick. In the Arizona and Florida storms, there were two layers of activity. Temperatures at the lower boundary of the layers were near 4°C and −18°C in the Arizona storm and −11°C and −39°C in the Florida storm. In the Colorado storm, there was a single layer having a lower boundary near the 0°C isotherm. Our interpretation is that each of the two layers in the Arizona and Florida storms is associated with a corresponding charged region in the dipole of the thundercloud charge distribution. We suggest that the single layer in the Colorado storm was a result of the dipolar regions being closer together in altitude.
Interannual variability of the equatorial Pacific in the 1960's
Authors: Busalacchi Antonio J. , O'Brien James J.
Published: February 2008

A linear numerical model forced by winds estimated from ships for each month from January 1961, to December 1970, is used to study the interannual variability of the equatorial Pacific. Model pycnocline variability at the Galapagos Islands is very similar to the observed variability of sea level. The maximum significant cross correlation of the two records is near zero lag. The 1963, 1965, and 1969 El Niño events are characterized by a persistently deep pycnocline. The model pycnocline variability at Talara, Peru, leads the observed SST variability by 2 months. The lag structure of pycnocline variability cross correlations indicates that the variability at the equator is related to the excitation of internal Kelvin and Rossby waves. The onset of the 1965 and 1969 El Niño events was triggered by a large amplitude downwelling Kelvin wave excited by relaxation of the easterlies west of the dateline. None of the El Niño events of the 1960's were related to anomalous relaxations of the wind field over the central Pacific. In addition, the seasonal intensification of the southeast trades over the central Pacific was not as strong as during non‐El Niño years. The subsequent cessation of the remotely forced seasonal upwelling caused the pycnoline to be depressed throughout the El Niño year. During the southern summer, reestablishment of the semiannual variability of the southeast trades over the central equatorial Pacific excited a seasonal downwelling Kelvin wave. This second major downwelling impulse resulted in the double peak downwelling signature observed in sea level records. The minor El Niño of 1963 was soley due to the cessation of the semi‐annual wind stress variability east of 180°. The absence of remotely forced upwelling Kelvin waves kept the pycnocline deeper than normal following the seasonal downwelling at the outset of the year. There was not a relaxation of the wind field west of the dateline prior to the 1963 El Niño.
Ocean surface height‐slope probability density function from SEASAT altimeter echo
Authors: Lipa B. J. , Barrick D. E.
Published: February 2008

This paper describes new methods for the interpretation of microwave scatter from the sea. Roughsurface scattering theory has led to an integral equation for the echo voltage in terms of the joint heightslope probability density function (pdf). We have developed methods for the inversion of this equation that do not require the assumption of a model for either the ocean surface or the transmitted pulse. In addition they are far more efficient than traditional grid‐search methods for model fitting. We have applied our methods to SEASAT data taken over Hurricane Fico. Statistical data analysis was performed to give the data covariance matrix and the correlation coefficient between successive waveforms and to trace the propagation of error through the inversion process to give statistical uncertainties in the derived parameters. The usual assumption of Rayleigh statistics is shown to be violated by the data, since the number of degrees of freedom increases linearly with power, independent of sea state; we conclude that this is an instrumental effect. We find that the waveforms are significantly correlated over distances of several kilometers at high sea states and suggest coherence of long ocean waves over these distances as the cause. We obtained waveheight higher‐order parameters by least squares fitting of a Gram‐Charlier model for probability densities to the calculated values. For averages over 160 km of sea, we obtain a mean surface height bias correction, significant waveheight, and height skewness parameter with standard deviations of 4, 0.7, and 15%. In addition to this height bias correction easily removed from the data, we identify another sea‐state‐dependent height bias that can exceed 50 cm. That this exists in the data is proof that one must employ the joint height‐slope pdf in the scattering model, and not merely the height pdf as conventionally used.
An observation of the horizontal and vertical diffusion of a passive tracer in the deep ocean
Authors: Ewart T. E. , Bendiner W. P.
Published: February 2008

An experiment to measure the dispersion of a passive tracer injected at 300 and 1000 m depth in the Pacific 600 miles southwest of San Diego is described. Rhodamine dye was released as a (very nearly). point source, and the subsequent growth of the patch was mapped at various times, up to 66.2 hours after release, using a self‐propelled underwater research vehicle (SPURV), which carried temperature, conductivity, pressure, and dye sensors on a depth cycling trajectory through the patch. The analysis shows that the horizontal diffusion rates decrease with depth, that it is difficult to resolve the mixing in terms of a constant diffusion parameter based on any one of a number of models, that the 300 m results agree with those obtained by Schuert (1970), and that the patch growth began to develop eddy behavior at 66.2 hours when the rms second moment of the dye distribution was (r2)l/2 = 210 m. For the purpose of predicting horizontal mixing, the results indicate that eddy diffusivities of 1150 and 360 cm2/s at 300 and 1000 m, respectively, are the best fit values for spatial scales <200 m horizontally. Although we have focused on horizontal (isopycnal) diffusion, a few aspects of the vertical (diapycnal) characteristics of the patch are also discussed.
A note on using continuity to extend HF radar surface‐current measurements
Authors: Frisch A. Shelby , Leise James
Published: February 2008

We demonstrate the use of the equation of continuity to extend the HF radar surface current measurements across the baseline of two radars and in regions where only single radar coverage is available.
Turbulent transport of electric charge in the marine atmospheric boundary layer
Authors: Markson Ralph , Sedláčék Jan , Fairall Christopher W.
Published: February 2008

Sensible heat, water vapor, aerosols, gaseous pollutants, and electric charge are transported vertically in the marine boundary layer by turbulent processes. The standard eddy correlation method for measuring fluxes from aircraft requires inertial navigation systems, considerable computer power, and large aircraft with gust probes on specially engineered booms to correct for aircraft motions. Only a few laboratories can afford to operate aircraft systems of the required complexity. The development of a method for obtaining routine, high quality, relatively inexpensive measurements of at least one boundary‐layer flux profile from light aircraft (specifically not requiring an inertial platform or angular motion data) could permit enhancement of boundary‐layer research on a new statistical scale. The flux of electric charge (called the eddy current) can be inferred from simple dc measurements of electric field intensity and conductivity from a light aircraft. Recent aircraft measurements off the California coast show good correlation of surface layer eddy current peak values with the surface water vapor flux and the convective mixed layer velocity, w*. The electrical technique also appears to have exceptional sensitivity exceeding that of the eddy correlation technique. It is suggested that the eddy current could be used to infer the flux profiles of other passive scalars. Because space charge undergoes a decay in time, the space charge density does not tend to be well mixed (constant with altitude) in the planetary boundary layer. The ease of measuring space charge density gradient allows accurate determination of the passive scalar eddy diffusion coefficient, K, a parameter that has been difficult to measure in the past. Thus, atmospheric electrical measurements from aircraft have the potential for providing important new information for pollution modeling and studies of boundary‐layer meteorology.
Aerosol characteristics at Mauna Loa Observatory, Hawaii, after east Asian dust storm episodes
Authors: Darzi Michael , Winchester John W.
Published: February 2008

Concentrations of elements, including S, Al, Si, K, Ca, Ti, and Fe, in aerosols sampled sequentially with 3.7‐hour time resolution over a 2‐week period in April and May 1979 at the Mauna Loa Observatory, Hawaii, indicate that long‐range transported ‘background’ crustal dust aerosol can reach concentrations in excess of 20 μg m−3 with more than 8μg m−3 of additional sulfate. Favorable regional meteorology after known dust storm episodes, as well as similarities in crustal element ratios, point to dry areas of northern China as the major source region for this crustal aerosol. Time series analyses for crustal elements show a dominant 21‐hour but no 24‐hour period, a result that can be accounted for by a diurnally varying source process with subsequent modification of periodicity, e.g., by wind speed convergence during transport. Time‐dependent associations between S and the crustal elements, especially high coherency at long periodicities, also imply a long‐range transport for much of the S, possibly from populated areas in eastern Asia, including China and Japan. This source may contribute much of the sulfuric acid believed to cause the relatively high acidity of rainwater observed at higher altitudes in Hawaii. Mauna Loa Observatory, at 3400 m altitude, is apparently an excellent location for detecting Asian dust and pollutant transport during spring with little interference from Hawaii‐derived aerosol.
Distribution of thorium isotopes between dissolved and particulate forms in the deep sea
Authors: Bacon Michael P. , Anderson Robert F.
Published: February 2008

The distribution of 234Th, 230Th, and 228Th between dissolved and particulate forms was determined in 17 seawater samples from the Guatemala and Panama basins. Sampling was carried out in situ with battery‐powered, submersible pumping systems in which the seawater first passed through a Nuclepore filter (1.0‐μm pore size) and then through a cartridge packed with Nitex netting that was impregnated with MnO2 to scavenge the dissolved Th isotopes. Natural 234Th was used as the tracer for monitoring the efficiency of scavenging. For all three isotopes, most of the activity was found in the dissolved form. On the average 4% of the 234Th, 15% of the 228Th, and 17% of the 230Th occurred in the particulate form, though the percentages were found to be strongly dependent on particle concentration. These distributions are not consistent with chemical scavenging models that assume irreversible uptake of Th on particle surfaces. The results can be explained, however, if continuous exchange of Th isotopes between seawater and the particle surfaces is assumed. Vertical profiles of both particulate and dissolved 230Th show increasing concentrations with depth, as required by the assumption of reversible exchange. Some of the dissolved 230Th profiles, however, show a reversal of this trend near the bottom, indicating accelerated scavenging near the water/sediment interface. Kinetics of both adsorption and desorption can be examined if at least two Th isotopes are measured in the same samples. Results show that reaction times are short (a few months) compared to the residence time of suspended matter in the deep ocean (several years), indicating that particles suspended in the deep sea are close to equilibrium with respect to exchange of metals at their surfaces.
Tropospheric N2O variability
Authors: Levy H. , Mahlman J. D. , Moxim W. J.
Published: February 2008

Tropospheric N2O climatologies are simulated with the GFDL general circulation/tracer model for three idealized source specifications: (1) a constant surface flux of 1.44×109 molecules cm−2 s−1 distributed uniformly over the earth's surface with a global source strength of 17 tg N2O yr−1 and an atmospheric lifetime of 131 yr; (2) a 13 month integration of the stable N2O field from experiment 1 with its N2O source removed; (3) a constant surface flux of 2.24×1010 molecules cm−2 s−1 over only those land areas with precipitation in excess of an arbitrary limit of 127 cm yr−1, but with the same global strength (17 tg N2O yr−1) and atmospheric lifetime (131 yr) as in experiment 1. In the boundary layer the model produces an interhemispheric gradient with a minimum in the northern hemisphere (N.H.). This is due to the greater downward transport in the N.H. which results in more dilution of N.H. boundary layer N2O mixing ratios by the N2O poor air from the lower stratosphere. The boundary layer distribution of N2O is also influenced by the distribution of the surface source. The lack of an N2O maximum in the model's N.H. boundary layer suggests that, unlike the model's idealized source, the true source has a large excess in the northern hemisphere. Above the boundary layer the north‐south gradient is controlled by the large‐scale vertical transport which produces a N.H. minimum in N2O mixing ratio. The impact of the surface source distribution is small. Current measurements at 500 mbar have too low a precision to confirm or disprove the model prediction of an interhemispheric gradient with a N.H. minimum in the middle troposphere. The sources of temporal variability in the model's N2O fields are transient motions of all scales acting on mixing ratio gradients, both vertical and horizontal. The model finds that a small surface source of 17 tg N2O yr−1, sufficient to balance stratospheric destruction, is more than able to maintain the observed variability in the boundary layer (≤1.0%). The empirical Junge rule relating temporal relative standard deviation to lifetime clearly does not apply to measurements in the boundary layer. There, the variability is dependent on local meteorology and source strength rather than on atmospheric lifetime. It ranges from <0.1% in regions far from any source to 1.0–2.0% in regions with both a source and weak vertical motion. However, the measurement of local mixing ratio time series in the boundary layer, when combined with local meteorological data, should give considerable information about the surrounding sources.
Atmospheric methyl iodide (CH3I)
Authors: Rasmussen R. A. , Khalil M. A. K. , Gunawardena R. , Hoyt S. D.
Published: February 2008

Global measurements of methyl iodide (CH3I) show that typical concentrations in background air are between 1 and 3 pptv (1 ppt = 10−12) in the boundary layer and drop to half of these values above the boundary layer. Concentrations of CH3I over cities in Oregon were found to be similar to background levels. These low concentrations suggest that CH3I may not affect atmospheric concentrations of free radicals, O3, or the NO2/NO ratio, as recent model calculations had shown. We also found that near‐oceanic regions characterized by high biomass productivity, there is 10 pptv −20 pptv of CH3I. By using these results in conjunction with measurements of CH3I in seawater we calculated a global flux of about 1.3 Tg/year from the oceans, most of it (1 Tg/year) from the small fraction of the ocean with high biomass productivity. All these results are based on more than 450 measurements of CH3I at locations ranging from the arctic circle to the south pole. Uncertainties relating to the global distribution, sources, and sinks are identified and discussed.