bluuebunny/crossref_metadata_2025 huggingface dataset:
Odd nitrogen production by meteoroids
Authors: Park Chul , Menees Gene P.
Published: February 2008

The process by which odd nitrogen species (atomic nitrogen and nitric oxide) are formed during atmospheric entry of meteoroids is analyzed theoretically. An ablating meteoroid is assumed to be a point source of mass with a continuum regime evolving in its wake. The amounts of odd nitrogen species, produced by high‐temperature reactions of air in the continuum wake, are calculated by numerical integration of chemical rate equations. Flow properties are assumed to be uniform across the wake, and 29 reactions involving five neutral species and five singly ionized species are considered, as well as vibrational and electron temperature nonequilibrium phenomena. The results, when they are summed over the observed mass, velocity, and entry angle distribution of meteoroids, provide odd nitrogen species annual global production rates as functions of altitude. The peak production of nitric oxide is found to occur at an altitude of about 85 km; atomic nitrogen production peaks at about 95 km. The total annual rate for nitric oxide is 4 × 107 kg; for atomic nitrogen it is 1.7 × 108 kg.
Remote acoustic monitoring of natural suspensate distributions, active suspensate resuspension, and slope/shelf water intrusions
Authors: Orr Marshall H. , Hess Frederick R.
Published: February 2008

Acoustic data, transmissometer data, and calculations are presented which indicate that high‐frequency acoustic backscattering systems can become a valuable tool in the remote monitoring of suspended particle distributions and active resuspension areas. Data are also presented which show that acoustic backscattering systems can be used to remotely detect slope/shelf water frontal zones. Towed acoustic systems should be able to map the extent of the frontal zone and add significantly to the understanding of frontal zone processes.
Winter cycle of sea surface thermal patterns, northeastern Gulf of Mexico
Authors: Huh Oscar K. , Wiseman William J. , Rouse Lawrence J.
Published: February 2008

During the winter of 1976–1977 a time series of NOAA satellite data was obtained which documented the seasonal cycle of sea surface temperatures. Data were obtained as both marine‐enhanced images and computer compatible tapes. Fall cooling initially affected only the lakes and estuaries. A band of cold inner shelf waters then formed along the coast. This expanded seaward to the shelf break as the winter season progressed. At the extreme of winter cooling, two major thermal fronts remained: one near the shelf edge, separating the shelf from deep gulf surface waters, and the other the cyclonic boundary of the Loop Current. The onset of spring warming was indicated by an increase in surface temperatures in the shallow inshore areas. The seasonal cycle was completed with the formation of nearly isothermal surface waters throughout the region, a condition characteristic of the summer season.
The front overlaying the continental slope in the eastern Bering Sea
Authors: Kinder T. H. , Coachman L. K.
Published: February 2008

We use hydrographic data to delineate a diffuse, large (nearly 1000 km long), and persistent (years) haline front which overlies the continental slope in the eastern Bering Sea. The front marks a transition between the waters above the deep basin, where the horizontal salinity gradient is almost zero and the flow is geostrophic, and the waters above the broad shelf, where salinity gradients are large and the flow is tidally dominated. We suggest that the change in mixing from the oceanic regime above the deep basin to the tidal regime over the shelf is responsible for the front. Because our arguments do not depend upon features unique to the Bering Sea slope, similar fronts should be found where freshwater runoff can dominate the density gradient and where strong boundary currents are absent.
Short‐term variability in the bottom boundary layer of the deep Ocean
Authors: Greenewalt D. , Gordon C. M.
Published: February 2008

A series of 130 CTD profiles of temperature and salinity were measured in and above the benthic homogeneous layer at a location on the Blake‐Bahama Outer Rise (28°00′N, 71°30′W). Four sets of measurements were made over a 3‐day period. In order to observe the short‐term behavior of the boundary layer, individual profiles in each set were separated in time by about 4 min or in distance by about 30 m. Layer thickness changes of up to 20 m were observed in less than an hour. The fact that the variations in homogeneous layer thickness and the shape of the overlying temperature gradient are coherent and progressive suggests internal waves as a source of short‐term thickness variability. At the site where the greatest short‐term variability was observed, this interpretation is supported by the calculated Brunt‐Väisälä period (2.3 hours) and the lack of correlation between the thickness and temperature of the homogeneous layer. At another site, however, increasing layer thickness was accompanied by rising temperature within the layer, a feature indicating that mixing in of the overlying water may also produce thickness changes.
Analysis of lightning data from the DMSP satellite
Authors: Turman B. N.
Published: February 2008

A lightning detector, consisting of 12 silicon photodiodes, each with a field of view of 700 × 700 km on the earth, has been flown on a Defense Meteorological Satellite Program satellite. Peak amplitude of the lightning flash was digitized within a range of 16 discrete levels, and the largest amplitude observed within a 1‐s sample interval was recorded. Approximately 10,000 lightning flashes were analyzed. The frequency of occurrence of peak lightning power within the range 108–1010 W has been obtained. The median power level was 1 × 109 W, and about 2% of the lightning flashes had peak power greater than 1010 W. These data are compared to similar results from a ground‐based experiment. Lightning flash rate per unit area of cloud cover in a storm complex was 4 × 10−5 s−1 km−2. The long‐term flash rate per unit surface area on the earth was 6 × 10−8 s−1 km−2, but this value may be biased toward high rates by the method of selecting the data base.
Nitrogen‐sulfur compounds in stratospheric aerosols
Authors: Farlow Neil H. , Snetsinger Kenneth G. , Hayes Dennis M. , Lem Homer Y. , Tooper Bernadine M.
Published: February 2008

Two forms of nitrosyl sulfuric acid (NOHSO4 and NOHS2O7) have been tentatively identified in stratospheric aerosols. The first of these can be formed either directly from gas reactions of NO2 with SO2 or by gas‐particle interactions between NO2 and H2SO4. The second product may form when SO3 is involved. Estimates based on these reactions suggest that the maximum quantity of NO that might be absorbed in stratospheric aerosols could vary from one‐third to twice the amount of NO in the surrounding air. If these reactions occur in the stratosphere, then a mechanism exists for removing nitrogen oxides from that region by aerosol particle fallout. This process may typify another natural means that helps cleanse the lower stratosphere of excessive pollutants.
Evidence for a solar cycle signal in tropospheric winds
Authors: Nastrom G. D. , Belmont A. D.
Published: February 2008

Amplitudes and phases of the 11‐year solar cycle in wind speed and temperature at radiosonde levels have been determined. These results are based on 174 stations over the northern hemisphere for the 25‐year data period 1949–1973. Amplitudes and phases were estimated by the method of time‐lagged correlation with the quasi‐periodic 10.7‐cm solar radio flux. The largest atmospheric amplitudes are near the tropopause level during winter, where in several regions over 40% of the interannual variance of the wind speeds is explained by the solar cycle. The hemispheric patterns of amplitude and phase suggest that the year‐to‐year latitudinal oscillations of the jet stream and the amplitude of the major standing long waves both appear to vary with the solar cycle. It is suggested that these results are due to changes in ultraviolet radiation, causing changes in ozone, and thus in stratospheric temperature, height, and wind fields. These changes may influence long‐wave vertical propagation characteristics and the direct radiation exchange between the stratosphere and troposphere. Possible problems with this hypothesis are discussed. To verify this hypothesis, the morphology of the solar cycle changes in stratospheric wind and temperature and the associated effect on tropospheric standing waves must be estimated. These results show that atmospheric responses to the solar cycle vary with longitude as well as with latitude. Hence studies of the atmospheric solar cycle must avoid arbitrarily combining stations over broad geographical areas or as zonal means.
Flow structures of the benthic ocean
Authors: Armi Laurence , D'Asaro Eric
Published: February 2008

Three‐dimensional structure of the near‐bottom density field was observed with a towed yo‐yoing profiler and a fixed current/temperature measuring array on the Hatteras abyssal plain. A great variety of structures were seen. Immediately above the bottom a well‐mixed bottom layer extends vertically 5–60 m, with less than 1 m°C potential temperature change. This mixed layer is often capped by a region of strong vertical potential temperature gradient, with up to 100‐m°C potential temperature change in ∼10 m. The boundary layer may be uniform for 10 km or exhibit a bottom temperature gradient of up to 20 m°C/km. Interior layers of nearly constant potential temperature and horizontal extent of 2–100 km are seen ∼25% of the time above the bottom mixed layer. When an interior layer is present, the bottom mixed layer is thinner. On many occasions an interior layer was seen to be horizontally continuous with the bottom mixed layer, suggesting formation of interior layers by detachment of the bottom mixed layer. A benthic front was observed. Differential horizontal advection is required to explain the observed structures. Velocity fluctuations above 1 cph increase in energy near the bottom, presumably a signature of turbulence in the mixed layer; these fluctuations are modulated by the passage of structures observed in the moored record.
Determination of the complex refractive index and size distribution of atmospheric particulates from bistatic‐monostatic lidar and solar radiometer measurements
Authors: Reagan J. A. , Byrne D. M. , King M. D. , Spinhirne J. D. , Herman B. M.
Published: February 2008

A method is presented for inferring both the size distribution and the complex refractive index of atmospheric particulates from combined bistatic‐monostatic lidar and solar radiometer observations. The basic input measurements are spectral optical depths at several visible and near‐infrared wavelengths as obtained with a solar radiometer and backscatter and angular scatter coefficients as obtained from a bistatic‐monostatic lidar. The spectral optical depth measurements obtained from the radiometer are mathematically inverted to infer a columnar particulate size distribution. Advantage is taken of the fact that the shape of the size distribution obtained by inverting the particulate optical depth is relatively insensitive to the particle refractive index assumed in the inversion. Bistatic‐monostatic angular scatter and backscatter lidar data are then processed to extract an optimum value for the particle refractive index subject to the constraint that the shape of the particulate size distribution be the same as that inferred from the solar radiometer data. Specifically, the scattering parameters obtained from the bistatic‐monostatic lidar data are compared with corresponding theoretical computations made for various assumed refractive index values. That value which yields best agreement, in a weighted least squares sense, is selected as the optimal refractive index estimate. The results of this procedure applied to a set of simulated measurements as well as to measurements collected on two separate days are presented and discussed.
Circulation of Na, Cl, and Br in the tropical marine atmosphere
Authors: Kritz Mark A. , Rancher Jacques
Published: February 2008

Concentrations of Na, Cl, Br, and I in aerosols and Cl, Br, and I in inorganic gases were measured in the marine atmosphere off the west African coast (∼0°N, ∼0°W) in June 1977 and used to estimate their mean lifetimes and rates of production. Mean concentrations (in micrograms per cubic meter) during an 8‐day, stable, rain‐free period of the voyage follows: for paniculate Na 4.0, Cl 5.3, Br 0.017, and 1 0.004; for inorganic gas Cl 1.0, Br 0.012, and 1 0.013. The results of a steady state analysis suggest a ∼3‐day mean residence time for the marine aerosol during the period of our observations, a ∼667 μg m−2 d−1 loss rate of Cl (probably as HCl) from the marine aerosol, and a subsequent
‐day mean residence time in the marine atmosphere. A similar analysis for gaseous inorganic Br gave a
μg m−2 d−1 mean loss rate from the marine aerosol and a ∼7‐day mean residence time. Computed dry deposition coefficients were (in centimeters per second) ∼0.4 for the marine aerosol, ∼0.77 for gaseous inorganic Cl, and ∼0.24 for gaseous inorganic Br.
Evidence for a continuous spectrum of equatorial waves in the Indian Ocean
Authors: Eriksen Charles C.
Published: February 2008

Seven‐month records of current and temperature measurements from a moored array centered at 53°E on the equator in the Indian Ocean are consistent with a continuous spectrum of equatorially trapped internal inertial‐gravity, mixed Rossby‐gravity, and Kelvin waves. A model spectrum of free linear waves analogous to those for mid‐latitude internal gravity waves is used to compute spectra of observed quantities at depths greater than about 2000 m. Model parameters are adjusted to fit general patterns in the observed spectra over periods from roughly 2 days to 1 month. Measurements at shallower depths presumably include forced motions which we have not attempted to model. This ‘straw‐person’ spectrum is consistent with the limited data available. The model spectru Ē (n, m, ω) = K · B(m) · C(n, ω), where Ē is an average local energy density in the equatorial wave guide which has amplitude K, wave number shape B(m) ∝ (1 + m/m*)−3, where m is vertical mode number and the bandwidth parameter m* is between 4 and 8, and frequency shape C(n, ω) ∝ [(2n + 1 + s2)½ · σ3]−1 where n is meridional mode number, and s and σ are dimensionless zonal wave number and frequency related by the usual dispersion relation. The scales are (β/cm)½ and (β · cm)½ for horizontal wave number and frequency, where cm is the Kelvin wave speed of the vertical mode m. At each frequency and vertical wave number, energy is partitioned equally among the available inertial gravity modes so that the field tends toward horizontal isotropy at high frequency. The transition between Kelvin and mixed Rossby‐gravity motion at low frequency and inertial‐gravity motion at high frequency occurs at a period of roughly 1 week. At periods in the range 1–3 weeks, the model spectrum which fits the observations suggests that mixed Rossby‐gravity motion dominates; at shorter periods gravity motion dominates. The model results are consistent with the low vertical coherence lengths observed (roughly 80 m). Horizontal coherence over 2 km is consistent with isotropic energy flux. Evidence for net zontal energy flux is not found in this data, and the presence of a red wave number shape suggests that net flux will be difficult to observe from modest moored arrays. The equatorial wave spectrum does not match across the diurnal and semidiurnal tides to the high‐frequency internal wave spectrum (the latter is roughly 1 decade higher).
Vertical wave number spectra of temperature fine structure in the equatorial Pacific
Authors: Hayes S. P. , Powell C. J.
Published: February 2008

We report observations of vertical fine structure in temperature along a meridional section from 10°N to 2°S at 125°W in the eastern Pacific. Structures are studied in two depth intervals, 300–600 m and 690–990 m, which are below the major influence of the surface currents and the equatorial undercurrent. On the basis of the TS relationship and the reasonably linear temperature and density profiles in these depth intervals, temperature fluctuations are used to infer vertical displacement fluctuations. We observed that vertical displacement spectra at the northern end (5°N to 10°N) of the section are consistent with midlatitude observations. At the equator the spectral level increases by almost 1 order of magnitude. Displacement spectra from the two depth intervals scale in a manner consistent with a WKBJ approximation. The increase is more pronounced for wave lengths longer than 10 m. From a 13 hour time series on the equator, we observed that the increased variance at high wave numbers (k > 0.02 cycle m−1) was associated with high‐frequency changes (ƒ > 0.08 cph), while the low wave number variance was associated with lower frequencies.
The exchange of infrared radiative energy in the troposphere
Authors: Wu Man‐li C.
Published: February 2008

On the basis of an atmospheric condition of a six‐layer general circulation model of the National Center for Atmospheric Research, the spatial and the spectral partition of the long‐wave radiation energy exchange in the model atmosphere is investigated and its implications are discussed. It is found that most of the energy is exchanged between adjacent layers and through the wings of strong lines. The strong line approximation is found to be a good approximation for water vapor transmittance. Cooling to space, however, is found to be a poor approximation for the total cooling rate. Both the strong line and cooling to space approximation are discussed in the content of the energy exchange findings.
Activities of the global biosphere as reflected in atmospheric CO2 records
Authors: Pearman G. I. , Hyson P.
Published: February 2008

A two‐dimensional global atmospheric diffusion simulation model is used to establish zonal and monthly average net surface fluxes of carbon dioxide (CO2) which are consistent with the variations in CO2 concentration observed at six monitoring stations distributed globally. These fluxes represent the zonally averaged net ecosystem production of primarily terrestrial biosphere. Annually, the global net ecosystem production during the photosynthetically more active season removed 6.8×1012 kg of carbon from the atmosphere, returning it during the less active winter months. This turnover represents about 14% of the annual continental net primary production of carbon and 0.8% of the total terrestrial biomass. During the growing season, net ecosystem production appears to be relatively independent of latitude in the northern hemisphere (∼6×10−9 kg carbon m−2 s−1). The model indicates that time correlations between the CO2 concentration at different altitudes of the northern hemisphere with the interhemispheric advection of air results in a net interhemispheric CO2 flux which becomes zero when the South Pole CO2 concentration is on average 0.92 ppmv above that at Mauna Loa, Hawaii. The influence of both the net and the gross atmospheric biospheric exchange of carbon on the atmospheric stable carbon isotope ratio is modeled. On time scales of a year the gross turnover of carbon has an insignificant effect, and all isotopic effects can be related to the net exchanges. It is argued that as with concentration, long‐term trends in isotopic composition will be best observed in the southern hemisphere.
SO2 versus sulfate wet deposition in the eastern United States
Authors: Dana M. Terry
Published: February 2008

Precipitation event samples from the Multi‐State Atmospheric Power Production Pollution Study (MAP3S) precipitation chemistry network have been analyzed for both dissolved SO2 and sulfate. Because SO2 oxidizes rapidly to sulfate in collected samples, special sampling and handling techniques were used to preserve the dissolved SO2 for analysis. About 2 years of concentration data show that dissolved SO2 can contribute significantly to the wet deposition of sulfur in the eastern U.S. region during the cooler months (October–March). On an annual basis, this contribution is on the order of 5% of the total sulfur wet deposition. The SO2 component can be as much as 80% of the total sulfur in individual wintertime samples, and it can exceed 50% of the weighted monthly mean deposition at certain sites. These results are compatible with estimates made on the basis of known SO2 solubility properties. Regional measurements of nonurban SO2 air concentrations can be combined with precipitation pH data and the solubility of SO2 to make estimates of the likely contribution of SO2 to the total sulfur deposition over the eastern U.S. region. It appears, however, that these estimates should be calculated on an event‐by‐event basis, with a recognition of the many variables involved.
Estimation of corona current beneath thunderclouds
Authors: Standler Ronald B.
Published: February 2008

The intense electric field beneath a thunderstorm often produces corona discharge from bushes and trees. The average steady state corona current per unit horizontal area, Jc, is approximately proportional to the time rate of change of the electric field at the ground when the value of the field changes sign following a lightning flash. This paper derives this relationship and proposes that the contribution of corona discharge to the charge budget of a thunderstorm be evaluated from measurements of the electric field at many sites below a thunderstorm rather than from direct measurement of the corona current.
Freshwater and Atlantic water in the Kara Sea
Authors: Hanzlick Dennis , Aagaard Knut
Published: February 2008

Hydrographic data from the Kara Sea show significant storage of freshwater (∼2.5 years of river input). This provides a buffer against large changes in ice and hydrographic conditions that might otherwise result from an anomalous year's runoff. The distribution of freshwater in the Kara Sea closely corresponds to bottom contours, indicating strong bathymetric influence on the spreading pattern. Observations also indicate areas within the Kara Sea in which the upward flux of sensible heat influences the thickness and the extent of ice coverage. Warm, saline Atlantic water which flows into the Kara Sea is particularly important in this regard. However, there is evidence that the flow of Atlantic water bifurcates in the northern reaches of the Kara Sea, so that one portion continues southward while the other curves back and exits with relatively little local heat loss.
Ocean current wave interaction study
Authors: Hayes John G.
Published: February 2008

A numerical model has been developed to incorporate refraction of ocean surface gravity waves by major ocean currents. The model is initialized with directional wave spectra and verified with aircraft synthetic aperture radar X band spectra, laser profilometer spectra, and pitch and roll buoy data. Data collected during the Marineland test experiment are used as surface truth observations for the wave‐current study. Evidence of Gulf Stream refraction and trapping of surface waves as well as caustics in the current is shown and modeled assuming a nonuniform Gulf Stream distribution. Frequency and directional resolution of the wave spectral distribution and the current refraction patterns illustrates the need for further study of ocean current‐wave interaction in wave refraction studies.
Importance of eddy heat flux in a heat budget for Oregon coastal waters
Authors: Bryden Harry L. , Halpern David , Pillsbury R. Dale
Published: February 2008

A heat budget for Oregon coastal waters during the summer upwelling season in 1973 is estimated from current and temperature measurements at a distance of 15 km from the Oregon coast. In this heat budget, the time‐averaged onshore‐offshore circulation transports heat offshore at an estimated rate of 4.5×104 cal cm−1 s−1. This offshore heat transport is compensated by a combination of onshore eddy heat flux, alongshore variation of alongshore heat transport, radiative heat gain by coastal waters, and cooling of coastal waters during summer. Of these mechanisms, the eddy heat flux is most important, balancing 40% of the offshore heat transport by the mean circulation. The eddy heat flux is directed down the mean horizontal temperature gradient and thus removes potential energy from the mean circulation. Removal of energy by eddies is estimated to be 70% of the energy put into the water column by the wind stress acting on the surface current. By removing energy from the mean circulation, eddies provide a mechanism limiting the magnitude of the alongshore circulation in Oregon coastal waters.
Respective influence of global pollution and volcanic eruptions on the past variations of the trace metals content of Antarctic snows since 1880's
Authors: Boutron Claude
Published: February 2008

Forty‐eight successive dated snow samples collected in central east Antarctica covering a continuous time sequence between 1880's and 1977 have been analysed for Na, Mg, K, Ca, Fe, Al, Mn, Pb, Cd, Cu, Zn, and Ag in ultraclean conditions. For all the elements, both the concentrations and the enrichment factors observed in 1977 are very close to the ones observed 100 years ago, then confirming that the influence of global pollution is actually negligible for these elements in the remote areas of the southern hemisphere. During the last 100 years, the variations of the enrichment factors of Pb and Zn are shown to parallel rather well those of the global volcanic activity, which suggests that the high atmospheric enrichments observed presently for these two metals are likely linked with volcanism. Between 1912 and 1916 (±5 years), there is a very strong signal showing a definite peak for the concentrations of most of the elements: It could be linked with a major Antarctic volcanic eruption.
Determination of cloud water acidity at a mountain observatory in the Adirondack Mountains of New York State
Authors: Falconer R. E. , Falconer P. D.
Published: February 2008

A ground‐based, cloud water collection system capable of intercepting significant volumes of water from clouds has been in operation at a mountain field station in the Adirondack Mountains of New York State for three summer seasons. An analysis of cloud water pH for August–September 1977 and 1979 strongly suggests that acid input to the ecosystem due to clouds at Whiteface Mountain may be significantly more important than that due to the much‐discussed phenomenon of acid precipitation. The mean pH of nonprecipitating clouds was 3.55 during 1977 and 3.50 during 1979; approximately 90% of all observations were found in the pH interval between 2.66 and 4.66. In the event that precipitation is intercepted concurrently with cloud droplets, a minimum dilution of the cloud water acidity by a factor of 60–80% can be expected. Other aspects of the collection and pH analysis of cloud water at Whiteface Mountain are also discussed.
Evaporation coefficient for the sea surface from eddy flux measurements
Authors: Anderson R. J. , Smith S. D.
Published: February 2008

Eddy correlation measurements of water vapor, heat, and momentum fluxes have been made at a fixed tower near the water's edge on a low, sand island. The evaporation data collected extend the range of conditions to cooler water (larger Bowen ratio) and include cases of stable stratification and downward vapor flux. The evaporation coefficient CE has a value of 1.3 × 10−3 in neutral conditions, varies with stability in accordance with accepted empirical profile laws, and increases significantly with increasing wind speed at this shoal location. The Bowen ratio of sensible to latent heat flux varies widely with meteorological conditions.
An efficient, accurate algorithm for calculating CO2 15 μm band cooling rates
Authors: Fels Stephen B. , Schwarzkopf M. D.
Published: February 2008

A fast, accurate method for obtaining atmospheric carbon dioxide transmission functions for the 15 μm band is presented. Tables of transmissivities for CO2 mixing ratios of 330 and 660 ppmv on standard pressure grids comprising geopotential heights ranging from 0 to 80 km and using standard temperatures are included. An algorithm for interpolating from these values to any desired temperature profile and to any other pressure grid is detailed.
Response of equatorial oceans to periodic forcing
Authors: Philander S. G. H. , Pacanowski R. C.
Published: February 2008

Oscillating wind with a period P induce variability with the following characteristics in the upper few hundred meters of the equatorial zone (5°N to 5°S) of the ocean. (1) P < 10 days: these winds fluctuate too rapidly to generate strong currents and excite primarily waves. (2) 10 days < P < 50 days: At these periods the winds generate intense equatorial jets in the upper 50 m, but at greater depths the variability has a small amplitude. Nonlinear eastward jets are more intense, are narrower, and are deeper than the corresponding westward jets so that winds with a zero mean value give rise to a mean eastward surface current. If the wind is always westward, then its fluctuating component intensifies the eastward equatorial undercurrent maintained by the mean winds. The surface flow is eastward and convergent when winds that are always westward go through a weak phase. (3) 50 days < P < 150 days: An eastward pressure force exists sufficiently long to generate an intense eastward equatorial undercurrent. Variability has a large amplitude in the surface layers and in the thermocline. Eastward phase propagation associated with Kelvin waves is prominent in the upper ocean because the nonlinear currents impede the Rossby waves. (4) P > 150 days: The amplitude of variability is almost independent of frequency. An equilibrium response which is in phase with the forcing and which corresponds to a succession of steady states is approached asymtotically. These time scales are for a basin 5000 km wide. If the width of the basin exceeds 5000 km, then the 150 daytime scale increases. In the deep ocean below the thermocline, motion corresponds to propagating waves generated by the divergence of the nonlinear currents in the upper ocean.
Multiple reflection effects on irradiance in the presence of Arctic stratus clouds
Authors: Wendler Gerd , Eaton Frank D. , Ohtake Takeshi
Published: February 2008

For under a stratus cloud cover and for identical solar heights, irradiation values are about 70% higher in spring than in late summer at Barrow in northern Alaska. A possible explanation for these differences is by interseasonal variations in cloud thickness and water content in the atmosphere. However, we demonstrate that multiple reflection is mostly responsible for it. In spring there is a very high surface albedo (∼80%), while in summer the surface albedo is low (∼15%). Hence multiple reflection between the surface and the lower extent of the stratus cloud cover is important when snow is on the ground but fairly unimportant after the snow has melted. To verify our assumption, airborne measurements were carried out for the same cloud but over surfaces of different albedos, namely, snow covered tundra (∼80%), broken sea ice (20–40%), and open water (4–16%). These data show clearly that if the surface albedo is raised, multiple reflection is the cause of the strong increase in irradiation. The interaction by multiple reflections of the spectral characteristics of various ground surfaces with the stratus clouds also was found to be displayed in the spectral irradiance received from the cloud cover.
HF radar measurements of long ocean waves
Authors: Lipa B. J. , Barrick D. E. , Maresca J. W.
Published: February 2008

Sea‐echo data from three separate narrow‐beam HF radar experiments on the Pacific Ocean are analyzed here by techniques presented in Lipa and Barrick (1980). Only those wave spectral components whose periods exceeded 10 s were included. Close agreement of radar‐deduced wave field parameters with surface observations confirms the validity of the second‐order theoretical solution for the echo Doppler spectrum, upon which this analysis is based. Depending on the particular experiment, a variety of wave parameters are extracted, including rms wave height, mean wave direction, dominant period, angular spread of the wave field, the nondirectional wave height spectrum, and higher Fourier angular coefficients versus wave frequency. The radar‐deduced wave parameters fall within the combined error bounds estimated for the radar and buoy wave observations; consequently, we contend that the primary source of error for radar data is finite sample size. Typical accuracies for specific parameters resulting from observations averaged over a 2‐hour period are ±5% for wave height, ±0.5 s for wave period, and ±7° for wave direction. Hence the utility of HF radars for long‐wave measurements has been validated.
On the circulation of the western Gulf of Mexico with observations from April 1978
Authors: Merrell William J. , Morrison John M.
Published: February 2008

In April 1978 the circulation pattern in the western Gulf of Mexico was dominated by a cyclonic circulation feature centered near 25°20'N, 95°20'W and an anticyclonic circulation feature centered near 23°30'N, 95°50'W. The north‐south scales of both gyres are approximately 225 km, while the east‐west scales are greater than 450 km. An eastward geostrophic transport of 29.7 × 106 m3/s is found between the centers of the cyclone and the anticyclone. We believe that both the anticyclone and the cyclone migrated to the western Gulf from the Loop Current region of the eastern Gulf. The anticyclone is probably supplemented by a wind‐driven circulation as described by Blaha and Sturges, and an eastward extension of the wind‐driven current which flows to the south along the lower Texas shelf may intensify the cyclone and/or anticyclone. Also, this extension of the Texas shelf current may tend to confine the anticyclone to the south and the cyclone to the north of the current's location.
A case study relating high ground level ozone to enhanced photochemistry and isentropic transport from the stratosphere
Authors: Haagenson P. L. , Shapiro M. A. , Middleton P. , Laird A. R.
Published: February 2008

Exceptionally high ozone ground level concentrations (>200 ppb) observed in Denver, Colorado, on the afternoon of March 4, 1978, are explained in terms of enhanced photochemistry combined with isentropic transport of ozone from the stratosphere. The maximum ozone concentrations observed on March 4 is the highest recorded for the 1975–1978 period. Inspection of the local pollutant and meteorological data shows high early morning accumulation of precursor gases and enhanced potential for afternoon photochemical activity. Objective cross‐sectional analysis and trajectories on isentropic surfaces indicate that some air parcels that mixed into the boundary layer over the city on the afternoon of March 4 were derived from a stratospheric intrusion 3 days earlier. It is concluded that a combination of these factors resulted in the exceptionally high ozone concentrations.
Effects of solar elevation and cloudiness on snow albedo at the South Pole
Authors: Carroll John J. , Fitch Bruce W.
Published: February 2008

Upward and downward fluxes of shortwave radiation (0.285 < λ < 2.8 μm) measured at Amundsen‐Scott Station (South Pole) during the summers of 1975, 1976, and 1977 are analyzed to determine effective surface albedos as functions of cloudiness (N) and solar elevation angle (A). For nonovercast conditions (N ≤ 0.25) the albedo decreases linearly from 0.97 at A ≲ 2° to a minimum of 0.83 ± .005 for A ≳ 20°. With near overcast conditions (N ≳ 0.7), linear decrease is also found from 0.93 at A < 2° to 0.84 ± 0.005 for A > 18°. The nonovercast results are compared with albedos reported for other Antarctic plateau stations. The higher values at the South Pole are attributed to slower rates of surface snow metamorphosis there due to lower maximum sun elevations and absence of diurnal radiative flux and temperature cycles. Arguments are presented to resolve conflicting reports that cloudiness both increases and decreases the snow albedo, and our results show that the effect of clouds depends on the solar elevation angle.
A comparison of SEASAT 1 altimeter measurements of wave height with measurements made by a pitch‐roll buoy
Authors: Webb D. J.
Published: February 2008

Measurements of significant wave height made by a pitch‐roll buoy during the Joint Air‐Sea Interaction Experiment (JASIN) are compared with measurements made at the same time by the SEASAT 1 radar altimeter as processed by the Jet Propulsion Laboratory SEASAT algorithms. Comparisons are made for eight occasions during which the significant wave height lay between 0.7 and 2.3 m. The radar altimeter is found to underestimate slightly the wave heights when compared with the pitch‐roll buoy. The mean ratio of the measurements is 0.96±0.04, and the standard deviation of individual comparisons about this mean is 0.10.
Radiation absorption coefficients of polycrystalline ice from 400–1400 nm
Authors: Grenfell Thomas C. , Perovich Donald K.
Published: February 2008

Absorption coefficients have been measured for bubble‐free polycrystalline ice over the spectral region 400–1400 nm. In order to obtain an easily measurable attenuation at short wavelengths (400–500 nm), a 2.83 m block was used. The technique employed to grow large quantities of bubble‐free ice is presented in detail. The absorption coefficients agree very well with previous results in the infrared and appear to provide greater accuracy and spectral detail at visible wavelengths.
Two‐dimensional interferometric positions of VHF lightning sources
Authors: Hayenga Craig O. , Warwick James W.
Published: February 2008

Using a new radio interferometric technique, we present observations of VHF lightning radiation source positions. The crossed base line interferometer provides the directions of arrival (azimuth and elevation) of VHF lightning radiation. Much flexibility exists in the choice of instrument parameters such as operating frequency and sampling interval. The present instrument operates at 34.3 MHz and provides an average position for every 2.5 μs of lightning radiation. Observations indicate that each 2.5 μs position should be attributed to a single discrete source in the sky. The positions of such sources define the temporal and spatial development of breakdown and rapid charge acceleration during the lightning flash. We have obtained VHF source positions correlated in time with electric field measurements. This allows us to identify the various processes occurring during a discharge and to compare the VHF phenomena with previously observed lightning phenomena. We have analyzed six flashes completely and portions of others. All six flashes contained ground strokes and two had intracloud discharges following the ground flash. We present data from three flashes that showed features common to the flashes we analyzed. The initial (preceding the first return stroke) and intracloud portions consisted of a large number of bursts of 20 μs average duration occurring on the average every 100 μs. The positions within each burst developed in a systematic, nearly linear, sequence with apparent speeds of ∼107 m/s. The relative positions from burst to burst drifted through the sky with speeds ∼105 m/s. In intracloud portions this drift was predominantly horizontal. In ground flashes the VHF sources drifted downward, in effect the leader for the first return stroke. They terminated at the return stroke.
Measurements of a saturated range in ocean wave spectra
Authors: Forristall George Z.
Published: February 2008

Wavestaff measurements made in the Gulf of Mexico and Waverider measurements from the Baltimore Canyon area have been used to study the form of ocean wave spectra at high frequencies. The observations are statistically consistent with the idea that the tail of the spectrum is in equilibrium with the local wind. Analysis showed that the spectral range between the mean wave frequency and about two and one half times that frequency is consistently proportional to the inverse of the fourth power of the frequency. At higher frequencies, the classical inverse fifth power law seems to hold. In the inverse fourth power range, the amplitude of the spectrum is also proportional to the wind friction velocity. These relationships should permit a reliable specification of this saturated range when only local wind observations are available. If the significant wave height and mean period are known, the amplitude of the tail of the spectrum can be predicted with somewhat greater accuracy. However, this relationship should be used with caution when the height and period statistics are influenced by swell.
Momentum transfer to the thermosphere by atmospheric tides
Authors: Teitelbaum Hector , Vial François
Published: February 2008

Propagation of the atmospheric tides results in a vertical flux of zonal momentum. This flux converges at altitude levels where dissipative processes take place. The deposition of the momentum contributes to the acceleration of the atmosphere resulting in a mean zonal wind. The latitude distribution of this acceleration depends on the relative importance of the mechanical and thermal dissipation. For instance, the first propagating mode, the mechanical dissipation of which takes place at 100 km altitude, induce an acceleration directed eastward above 20° latitude and westward between the equator and 20° latitude. This inversion is shown to be in agreement with the available experimental data.
Stratospheric eddy diffusion coefficients from tracer data
Authors: Massie S. T. , Hunten D. M.
Published: February 2008

Global distributions of nitrous oxide, methane, ozone, and carbon 14 are used to estimate four sets of stratospheric eddy diffusion coefficients. A photochemical equilibrium model calculates O(3P), O(1D), H, HO2, OH, H2O2, NO, and NO2 densities, as a function of altitude, latitude, and time. The calculated O(1D), OH, and observed Cl densities are used to obtain the eddy profiles associated with the methane and nitrous oxide distributions, for altitudes between 10 and 40 km. Application of a constant flux condition to the seasonally averaged ozone data yields eddy values below 20 km. Time‐dependent carbon 14 calculations produce eddy coefficients between 13 and 27 km. A composite profile is obtained by comparing the four sets of coefficients. Further, carbon 14 computations are used to test these profiles as well as those recommended in reports issued by the National Academy of Sciences in 1976 and 1979. The composite eddy profile produces the best agreement.
Effects of islands on equatorial waves
Authors: Yoon Jong‐Hwan
Published: February 2008

The effects of islands on equatorially trapped waves induced by the sudden onset of zonal wind are investigated by solving the shallow water equations numerically. The energy propagation associated with an equatorial Kelvin wave is almost unaffected by an island on the equator. The energy transmission ratio is over 0.8 even when the north‐south extent of the island is the same as the Rossby deformation radius. It is also shown that the Maldive Islands in the Indian Ocean and the Gilbert Islands in the Pacific Ocean do not affect the energy flux associated with Kelvin waves significantly. The sea level near the island, however, differs significantly from the sea level associated with an equatorial Kelvin wave in the absence of an island. This result has important implications for the interpretation of sea level measurements at equatorial islands. On the other hand, the energy propagation of equatorial Rossby waves (the lowest mode in the north‐south direction) is greatly affected by an island on the equator. The energy transmission ratio is less than 0.3 when the north‐south extent of the island is the same as the radius of deformation.
Observations of internal wave reflection off sloping bottoms
Authors: Eriksen Charles C.
Published: February 2008

Current and temperature spectra exhibit intensification and polarization near sloping bottoms over a band of frequencies centered at the local internal wave critical frequency. Examples are drawn from a variety of island, seamount, and continental slope observations. Waves propagating down from mid‐depth change energy density, wave number, and azimuth when they reflect off the bottom, providing a natural perturbation to the deep ocean interior internal wave spectrum. Deviations from linear theory are interpreted as evidence for dissipation through subsequent shear instability and/or nonlinear interaction. Topographic features appear likely to be energy sinks for internal wave energy.
A model for radionuclides in sediments influenced by mixing and compaction
Authors: Christensen Erik R.
Published: February 2008

A model for the activity of radionuclides in sediments has been set up based on the one‐dimensional advection‐diffusion equation. The model considers sedimentation, mixing, and compaction. Observed distributions of deposit‐feeding organisms, and the nature of physical disturbances, indicate that a gaussian diffusion coefficient may be appropriate. Two‐layer models with constant and gaussian mixing, respectively, in the upper layer are compared with measured Pb 210 profiles for two cores from Green Bay, Lake Michigan, and it is found that the maximal diffusion coefficient D0 in the gaussian model is considerably greater than the constant D value, e.g., D0 ≳ 4 versus D = 0.2 cm2/year, if compaction effects are neglected. The solution for the gaussian model is based on an approximate power series method. Compaction can be taken into account by using an exponential sedimentation rate or bulk sediment density. By comparing with measured data for a Lake Ontario core it is seen that compaction alone can give an appreciable flattening of the activity curves near the top layers.
Structure and variability of the alboran sea frontal system
Authors: Cheney Robert E. , Doblar Randy A.
Published: February 2008

Physical characteristics of the Alboran Sea in the western Mediterranean were examined in October 1977 during a survey by ship and aircraft. The main features observed were a distinct oceanic front coinciding with the jet of incoming North Atlantic water and an associated anticyclonic gyre in the western half of the basin. The front was confined to the upper 200 m and was a continuous feature extending from the Strait of Gibraltar 500 km eastward to the prime meridian. Of particular interest was the observed variability of the anticyclonic gyre. In 10 days between two surveys the center of the gyre shifted 50 km westward. This shift may correspond to changes in strength of the North Atlantic inflow as inferred by local wind and the average atmospheric pressure over the western Mediterranean.
A parameterization of effective soil temperature for microwave emission
Authors: Choudhury B. J. , Schmugge T. J. , Mo T.
Published: February 2008

The observed microwave brightness temperature of soils depends upon the soil temperature profile, which in a remote sensing application will not be known in any detail. In this paper we discuss a parameterization of effective soil temperature, which when divided into the brightness temperature gives the emissivity, in terms of surface (T0) and deep (T∞) soil temperatures as T = T∞ + C(T0 ‐ T∞). A coherent radiative transfer model and a large data base of observed soil moisture and temperature profiles are used to calculate the best fit value of the parameter C. For 2.8, 6.0, 11.0, 21.0, and 49.0 cm wavelengths the C values are, respectively, 0.802±0.006, 0.667±0.008, 0.480±0.010, 0.246±0.009, and 0.084±0.005. The parameterized equation gives results that are generally within 1 or 2% of the exact values.