bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of tropospheric desert aerosols at solar wavelengths by multispectral radiometry from Landsat
Authors: Otterman J. , Fraser R. S. , Bahethi O. P.
Published: February 2008

Characteristics of tropospheric desert aerosols are derived by comparing nadir spectral reflectivities computed from the radiative transfer models with reflectivities measured from Landsat. Over the ocean, reflectivities are compared, but over land the comparison is carried out by determining the ratios of the nadir reflectivity of the surface‐atmosphere system over heavy aerosol concentration to the reflectivity of the underlying surface. This remote sensing technique is found to be a sensitive approach for measuring n2, the imaginary part of the refractive index. The desert aerosols under study, in the Iran and Pakistan area, are essentially pure scatterers, inasmuch as an n2 value of 0.001±0.001 was determined for each of the four Landsat spectral bands, that is, for a spectral interval from 0.5 to 1.1 μm.
The SEASAT altimeter wet tropospheric range correction
Authors: Tapley Byron D. , Lundberg John B. , Born George H.
Published: February 2008

The wet tropospheric path delay for the SEASAT altimeter height measurements is on the order of 10–50 cm. The model for the tropospheric range correction must be accurate to 5 cm or better to achieve an overall 10 cm accuracy for the SEASAT altimeter height measurements. The wet tropospheric range correction is calculated either by using Fleet Numerical Oceanographic Center (FNOC) global interpolations of surface‐level atmospheric pressure, temperature, and water vapor pressure or by using SEASAT Multichannel Microwave Radiometer (SMMR) antenna temperature measurements at the 18, 21, and 37 GHz frequencies. The SMMR wet tropospheric correction algorithm is expressed as a linear function of the corresponding brightness temperatures. The algorithm is optimized by adjusting two scaling parameters to minimize the differences between the SMMR and radiosonde determined range corrections. The differences between the radiometer and radiosonde corrections have a standard deviation of 2.79 cm, while the standard deviation for the correction based on the FNOC global interpolation is 5.73 cm.
Surface wind analyses for SEASAT
Authors: Brown R. A. , Cardone V. J. , Guymer T. , Hawkins J. , Overland J. E. , Pierson W. J. , Peteherych S. , Wilkerson J. C. , Woiceshyn P. M. , Wurtele M.
Published: February 2008

To establish SEASAT sensor wind measuring capabilities, the best possible surface winds were needed. Fortunately, during the 99 days of SEASAT operation, two large scale experiments were conducted. The first, the Gulf of Alaska Experiment (GOASEX), was directed at obtaining data in conjunction with SEASAT. The second, the Joint Air Sea Interaction Experiment (JASIN), was an independent and much more comprehensive air and sea investigation and fortunately provided excellent comparison data for SEASAT. In addition, several storms provided good qualitative comparison windfields. Since the windfields have been developed independently of satellite‐determined winds, this paper deals only with the surface wind analysis and its accuracy. A subsequent paper will use these results to discuss the satellite sensor predictions compared with these data sets.
The carbon isotopic composition of atmospheric methane
Authors: Stevens C. M. , Rust F. E.
Published: February 2008

Recent measurements of the carbon isotopic abundance of atmospheric methane give a value of δ(13C/12C) = −47.0 ± 0.3‰, which is significantly different from earlier values measured by others between 1950 and 1970. The isotopic composition of various sources and the possibility of a temporal trend are discussed. The average methane concentration measured was 1.66 ppm, which is in accord with the increase in concentration since 1965–1970 observed in other studies.
Role of relaxation and contact times in charge separation during collision of precipitation particles with ice targets
Authors: Gross Gerardo Wolfgang
Published: February 2008

The relaxation time of charge transfer and the contact time are two of the parameters controlling charge separation when ice particles collide with one another or with liquid water droplets. For maximum efficiency of charge separation, the relaxation time should be of the same order as the contact time. The relaxation time of charge transport in ice was systematically determined as a function of impurity content and temperature. The contact time for ice/ice collisions was estimated from theory. Depending on the impurity species and their concentration, the relaxation time may be increased or decreased by orders of magnitude with respect to pure ice. Only particles of the order of 10−2 m radius seem to have contact times sufficiently long to give appreciable charge separation by ion transport in collisions between pure or slightly doped (0.1 ppm chloride) ice particles in a dry environment. Charge separation mechanisms involving liquid water and those operating by the transfer of electrons from surface states largely relax these conditions. These results have implications for cloud electrification models involving collision mechanisms.
Methane and nonmethane hydrocarbon concentrations in the North and South Atlantic marine boundary layer
Authors: Cofer Wesley R.
Published: February 2008

Methane and nonmethane hydrocarbon (NMHC) data were collected in the Atlantic marine boundary layer from 40°N to 32°S latitude during October and November 1980. Average volume mixing ratios for CH4 of 1.69±0.02 ppmv were obtained north of the intertropical convergence zone (ITCZ) and 1.60±0.02 ppmv south of the ITCZ. The hemispheric CH4 gradient was very sharp, decreasing rapidly between 14°N and 10°N latitude. Gaseous NMHC concentrations (based on response as CH4) were measured simultaneously and found to lie consistently within the standard error for the individual measurements (±0.02 ppmv) after correction for water vapor interference. The correction for water vapor response was large, frequently as much as 80% of the raw NMHC signal. Application of the student's t distribution test to the NMHC data set established that the mean northern and southern hemispheric NMHC mixing ratios measured, 0.016 and 0.010 ppmv, respectively, were statistically different at the 95% confidence level. These results indicate volatile NMHC mixing ratios average less than 0.02 ppmv over the Atlantic and represent the first set of semicontinuous NMHC measurements spanning the North and South Atlantic marine boundary layer.
Photochemical coupling between the thermosphere and the lower atmosphere: 1. Odd nitrogen from 50 to 120 km
Authors: Solomon Susan , Crutzen Paul J. , Roble Raymond G.
Published: February 2008

A two‐dimensional photochemical model which treated the troposphere and stratosphere has been extended to include the mesosphere and lower thermosphere. The model is described, and particular emphasis is placed on the transport and chemistry of nitric oxide. Large amounts of NO are produced in the lower thermosphere both by solar radiation during quiet times and through auroral ionization. Using reasonable descriptions of dynamical processes in the two‐dimensional model, substantial amounts of NO produced in the thermosphere can reach the stratosphere, particularly at high latitudes during polar winter. This process provides a coupling between the upper and lower atmosphere which may play a significant role in the photochemistry of odd nitrogen and odd oxygen in the stratosphere.
Resolution of basaltic and continental aerosol components during spring and summer within the boundary layer of Hawaii
Authors: Darzi Michael , Winchester John W.
Published: February 2008

An important continental aerosol component, up to 70% of the total dust load during the spring, has been resolved from the local basaltic component using short time‐step (3.7 hr) sampling at the Hawaiian Volcano Ovservatory (HVO), a site below the inversion layer at 1.2 km altitude. The median continental contribution for approximately 2‐week periods from mid‐March to mid‐June 1979 ranged from 1 to 2μg m−3, whereas from mid‐June to early September 1979 this component was not found, being less than the detection limit of ⅓ its spring magnitude. Over the 6‐month period, the median concentrations for the basaltic aerosol ranged from about 0.2 to 18 μg m−3, a variation associated with local rainfall. This basaltic component exhibits a strong diurnal variation, resulting from the local wind regime, with a ratio of a mid‐afternoon maximum to an early morning minimum of up to 20 or more. Of the six lithophilic elements examined (Al, Si, K, Ca, Ti, and Fe), Si shows the greatest earth/air fractionation, with the continental and local basaltic aerosols being depleted by more than 35% relative to an average crustal and Hawaiian basaltic rock composition, respectively. Time series analysis of the concentrations and a detailed examination of the element ratios indicate that local and continental soils are the only important determinants of the overall aerosol composition at this site for these elements. Compositional differences between the continental dust at HVO and that sampled concurrently at the Mauna Loa Observatory (3.4 km altitude) may be due to the presence of two distinct dust plumes over Hawaii originating from different desert regions in Asia.
A long geoclimatic record from the Permian
Authors: Anderson Roger Y.
Published: February 2008

A 260,000‐year, continuous, annual geoclimatic time series has been compiled from the varved Permian Castile and Bell Canyon Formations of the Delaware Basin, southeastern New Mexico, and southwestern Texas. The last 200,000 years of the record was obtained from calcite‐laminated anhydrite and anhydrite‐laminated halite, which formed as a result of seasonal and annual deposition in the evaporite basin. The time series is based on measured thickness of individual varves. Analyses of calcium sulfate, calcium carbonate, and organic matter were made on 50‐year intervals in the evaporite part of the sequence. Time series of the major components were examined by using smoothed graphic plots, variance spectra, and moving correlation coefficients. The longest oscillation recorded in the series that may be of climatic origin has a period of about 100,000 years. The calcium sulfate record contains 9–11 distinct oscillations with an average period of about 20,000 years. The strongest oscillation has a preferred spectral period of 2700 years and is recorded throughout the series as thickness changes in calcium sulfate, as events controlling halite deposition, and as episodes of basin freshening. A broad spectral response near a period of about 200 years reflects changes in sulfate, carbonate, and halite thickness. Shorter periods do not have consistent spectra. The time series contains no preferred periods that have not already been identified in previously described records. The climatic changes appear to be the result of a deterministic response to orbital effects at the longer periods and stochastic processes at the shorter periods. An unusually strong response near 2700 years is associated with episodic freshening of the basin. This period has been well established in the Holocene paleoclimatic record, and its presence in the Permian suggests a deterministic origin.
Comparison between the accuracies of a new discretization method and an improved Fourier method to evaluate heat transfers between soil and atmosphere
Authors: Hechinger E. , Raffy M. , Becker F.
Published: February 2008

To improve and evaluate the accuracy of Fourier methods for the analysis of the energy exchanges between soil and atmosphere, we have developed first a Fourier method that takes into account the nonneutrality corrections and the time variation of the air temperature and which improves the linearization procedures and, second, a new discretization method that does not imply any linearization. The Fourier method, which gives the exact solution of an approximated problem, turns out to have the same order of accuracy as the discretization method, which gives an approximate solution of the exact problem. These methods reproduce the temperatures and fluxes predicted by the Tergra model as well as another set of experimental surface temperatures. In its present form, the Fourier method leads to results that become less accurate (mainly for low wind speeds) under certain conditions, namely, as the amplitude of the daily variation of the air and surface temperatures and their differences increase and as the relative humidities of the air at about 2 m and at the soil surface differ. Nevertheless, the results may be considered as generally satisfactory. Possible improvements of the Fourier model are discussed.
A study of the bottom boundary layer over the Eastward Scarp of the Bermuda Rise
Authors: Bird Arlene A. , Weatherly Georges L. , Wimbush Mark
Published: February 2008

Velocity and temperature measurements from the bottom boundary layer (BBL) over the Eastward Scarp of the Bermuda Rise in water depth of 4620 m show little variability over an 8‐month period. The free‐stream flow 62 m above the bottom was south‐southeasterly following the isobaths in the region with an average speed of 22 cm/s. The current vector in the BBL rotated an average of 5° in a counterclockwise sense between 62 and 0.8 m above the bottom. The thickness of the BBL was ∼40 m and the average magnitude of the bottom stress was ∼0.7 dynes/cm2. Mean speed profiles, height of the BBL, and the magnitude of the bottom stress predicted by a model compare favorably with the observations, but the model predicts a rotation of the current vector between 62 and 0.8 m more than twice that measured. The time‐dependent nature of the flow field is also reproduced by the model. The Bermuda Rise data and speed profile measurements at the base of the Scotian Rise show that the M2 clockwise polarized tide is damped more than the mean current as the bottom is approached in the BBL. This phenomenon is reproduced by the model and can be explained by differing effective Ekman layer thicknesses associated with tidal and steady components of the flow.
Microwave emissions from soils with rough surfaces
Authors: Tsang L. , Newton R. W.
Published: February 2008

The effect of surface roughness on the thermal microwave emission of soils has been studied with the Kirchoff approach. A model is presented that includes both the coherent and incoherent reflectivities of the rough surface. It is demonstrated that both the coherent and incoherent terms must be included in order for theoretical computations to provide good agreement with the experimental data, especially for wet soil, where surface roughness causes a dramatic increase in brightness temperature. In addition, the model including both the coherent and incoherent terms allows one to use the physically measured surface height deviations of the rough surface in the model. Previous models have required that an effective height, not equal to the actual surface height measurements, be used in order for theoretical computations to match measurements.
Spring season flow of the Tsushima current and its separation from the Kuroshio: Satellite evidence
Authors: Huh Oscar K.
Published: February 2008

Attempts to determine where and how separation between the Kuroshio and Tsushima Current occurs have been inconclusive. Spring season satellite data acquired over a number of years reveals two conditions important to this question: (1) an areally extensive zone of mixing between the Kuroshio and shelf waters occurring along the edge of the East China Sea shelf, and (2) plumes of warm water from the Kuroshio extending into the mixed water west of Kyushu. This mixed water is observed to form the Tsushima Current in the outer shelf of the northern East China Sea and Korea Strait. Warm plumes branching from the north wall of the Kuroshio are seen with particular clarity in imagery of April 23, 1981, and February 21, 1982. Details of the split suggest that branching was a transient event.
Wind‐stress coefficients over sea surface from breeze to hurricane
Authors: Wu Jin
Published: February 2008

The empirical formula proposed recently relating wind‐stress coefficient to wind velocity, C10 = (0.8 + 0.065 U10) × 10−3, appears to be applicable even in hurricanes. This formula also agrees with the correlation curve proposed earlier, C10 = [κ/ln(1/aC10F2)]2, F = U10/(gZ)1/2, where a = 0.0185 is the Charnock constant and Z = 10 m is the anemometer height.
Volcanic aerosol phosphorus, chlorine, and sulfur at Kilauea, Hawaii
Authors: Darzi Michael , Winchester John W.
Published: February 2008

Aerosol concentrations of P, Cl, S, and major soil‐derived elements were measured sequentially at the Hawaiian Volcano Observatory (HVO) from March to September 1979, with 3.7‐hour time resolution using a Nuclepore‐filter sampler. The filters were analyzed by particle‐induced X ray emission (PIXE). Comparison with diurnal variations in the air flow inferred from major soil elements, e.g., Fe, as well as measurements made previously at fumaroles near HVO, indicate that the P, Cl, and S may be attributed mainly to volcanic emissions from Kilauea. From April 23 to June 30, P was found with concentrations up to 1000 ng m−3, but before and after those dates, P was generally below the detection limit of 50–80 ng m−3. Cl and S were frequently found over the entire sampling period, also with concentrations up to 1000 ng m−3. However, when P was found, Cl was almost never detected simultaneously. The mutually exclusive occurrences of P and Cl suggest volatility release of HCl from aerosol particles by reaction with strong acid associated with P. If strong acidity is due to H2SO4, it is not well predicted by S, which may also include other sulfates or sulfur, since aerosol S concentrations are not well correlated with P or Cl. The behavior of these three elements suggests that the volcanic sources of P are more localized than those of Cl or S. It is significant that concentrations of aerosol P can be as high as aerosol Cl and S, all apparently of primary volcanic origin, indicating that volcanism may be an important, but hitherto unrecognized, process in the atmospheric geochemical cycling of phosphorus.
Lightning and surface rainfall during Florida thunderstorms
Authors: Piepgrass Michelle V. , Krider E. Philip , Moore Charles B.
Published: February 2008

Electric field records have been computer analyzed to determine the lightning statistics for air‐mass thunderstorms at the NASA Kennedy Space Center, Florida. The results for 79 summer storms which produced 10 or more discharges during the years 1976–1980 indicate that cloud and cloud‐to‐ground discharges occur at a mean rate of about 2.4 discharges per minute per storm. The maximum flashing rate over a 5‐min interval was 30.6 discharges per minute on July 14, 1980. Estimates of the monthly area density of all discharges during June, July, and August 1974 through 1980 range from 4 to 27 discharges per km2 per month, with a systematic uncertainty of perhaps a factor of 2 in the sampled area. The mean and standard deviation of the monthly area density over the above years was 12±8 discharges per km2 per month, and the mean area density of just cloud‐to‐ground (CG) flashes is estimated to be 4.6±3.1 CG flashes per km2 per month. Tipping‐bucket rain gauges were operated at each field‐mill site during 1976, 1977, and 1978 as part of the Thunderstorm Research International Program, and the statistics on rainfall are given for 28 storms in 1977 and 1978. Two thunderstorms, one small and one large, were favorably located and relatively stationary, so that the lightning data and surface rainfall could be directly compared. In these storms, there was a good correlation between lightning and rainfall when the latter lagged the former by times of 4 and 9 min. The average rainfall associated with each lightning is estimated to be about 6.7×103 m3 per discharge during the small storm and about 8.5×103 m3 per discharge during the large storm. The average rain volumes associated with each cloud‐to‐ground flash are estimated to be 1.8×104 m3 per CG flash and 2.2×104 m3 per CG flash during these storms, values that are in good agreement with estimates by other investigators.
About the reversal of mean zonal wind during the stratospheric warming of 1970–1971
Authors: Krüger W. , Schmitz G.
Published: February 2008

Special aspects of the dynamics of the stratospheric sudden warming 1970–1971 are investigated by using daily data. During the period of December 1970 until March 1971, several atmospheric levels are analyzed in order to demonstrate the development of the major stratospheric warming. The wave‐1 and wave‐2 propagation, the mean zonal wind and temperature, and the horizontal eddy fluxes of momentum and heat are considered, and the development of the zonal wind is analyzed on the basis of the mean momentum equation. It turns out that the equatorward eddy momentum fluxes at high latitudes associated with planetary waves were crucial in effecting the zonal wind reversal as was discussed by O'Neill and Taylor [1979] for the warming of January 1977. In addition, the present paper indicates that a negative meridional phase gradient entailing an equatorward momentum flux propagated from the troposphere up to the stratosphere.
The structure of planetary waves up to the lower mesosphere based on data analyses and model calculations
Authors: Grieger N. , Schmitz G.
Published: February 2008

For six winters, planetary waves and associated meridional fluxes of momentum and heat have been analyzed up to mesospheric heights. The December monthly mean of planetary wave amplitude one (two) reaches its maximum at 40 km (30 km) of 700 gpm (300 gpm) at 60°N. Further, the reflection of planetary waves in the stratosphere has been discussed by model results as well as by analyzed data. It was shown that the stationary wave‐one amplitude and phase in the upper troposphere strongly depend on stratospheric wind conditions. Especially, the evidence of this dependence in the analyzed data supports the idea that extraterrestrial or anthropogenic influences on the stratosphere can lead to consequences in tropospheric heights.
Laboratory measurement of water surface bubble life time
Authors: Zheng Q. A. , Klemas V. , Hsu Y.‐H. L.
Published: February 2008

The bubble life times of various water samples were measured in the laboratory. The statistical features of bubble life time on water surfaces are discussed. The measurement results showed that the distribution of bubble life times of various water samples follow a Rayleigh distribution and that the mean life times are a function of the bubble sizes. The total average of life times of various sizes for tap water is 2.24 s, it is 2.98 s for Delaware Bay water, and 3.89 s for Atlantic Ocean water, respectively. Comparing the statistical features of the bubble life time generated under different conditions, we found that the bubble life times are independent of the methods used to generate them.
Exponential growth and atmospheric carbon dioxide
Authors: Laurmann John A. , Rotty Ralph M.
Published: February 2008

The adequacy of assumptions required to project atmospheric CO2 concentrations in time frames of practical importance is reviewed. Relevant issues concern the form assumed for future fossil fuel release, carbon cycle approximations, and the implications of revisions in fossil fuel patterns required to maintain atmospheric CO2 levels below a chosen threshold. In general, we find that with a judiciously selected exponential fossil fuel release rate, and with a constant airborne fraction, we can estimate atmospheric CO2 growth over the next 50 years based on essentially surprise free scenarios. Resource depletion effects must be included for projections beyond about 50 years, and on this time frame the constant airborne fraction approximation has to be questioned as well (especially in later years when the fossil fuel use begins to taper off). For projections for over 100 years, both energy demand scenarios and currently available carbon cycle models have sufficient uncertainties that atmospheric CO2 levels derived from them are not much better than guesses.
Simultaneous measurements of vertical distributions of stratospheric NO3 and O3 at different periods of the night
Authors: Rigaud P. , Naudet J. P. , Huguenin D.
Published: February 2008

Simultaneous measurements of NO3 and O3 were performed at different periods of the night from stratospheric balloons launched from the CNES balloon station at Aire‐sur‐l'Adour in September 1980 and September 1981. The experimental NO3 vertical profiles compare favorably with those predicted by the photochemical theory. Differences can be explained by the dependence of the recombination rate of NO2 and O3 upon altitude. The O3 concentrations above 30 km measured by spectrophotometry around λ = 660 nm present a remarkable stability. Measurements obtained by means of this technique could be used as a reference for the detection of long‐term variations of O3.
Lightning propagation and flash density in squall lines as determined with radar
Authors: Mazur Vladislav , Rust W. David
Published: February 2008

The propagation of lightning has been studied using radar techniques. The rise time of radar echoes is explained by ionized channel propagation through the radar beam. The calculated values agree well with those obtained experimentally. Measurements of the radial velocity of streamer propagation (along the antenna beam) show speeds of at least 2.5× 05 m/s. The time‐range variations in lightning echoes are indicative of (1) new ionization as streamers develop into different parts of the cloud, (2) channel decay during which adequate ionization exists for radar detection, or (3) continuing current. Lightning flash density has been determined for two squall lines, one in the USSR (using a 2‐m wavelength radar) and the other in the United States (using a 23‐cm wavelength radar). The United States study shows that the maximum lightning density tends to be near the leading edge of the precipitation cores in developing cells. As a cell in the squall line develops and the total lightning density increases, long discharges are produced, but shorter ones predominate. In contrast, as the cell dissipates, short flashes diminish or cease, and the long flashes dominate the lightning activity.
Roughness of the marine geoid from SEASAT altimetry
Authors: Brown R. D. , Kahn W. D. , McAdoo D. C. , Himwich W. E.
Published: February 2008

The geographical variability of short wavelength geoid power spectra (geoid roughness) has been mapped for the world's oceans between latitudes 72°N and 72°S. A spectral analysis of SEASAT altimeter data, reduced to sea surface heights, has been performed at 2‐min intervals for 15 consecutive days of the 3‐day repeat orbit. The geoid roughness represented by these spectra for wavelengths shorter than about 220 km is separated from the total sea height variance and is displayed in the form of a global contour map. The global average geoid roughness is 32 cm RMS, varying from a high in excess of 2 m RMS near deep ocean trenches to a low of 2 cm RMS in the southeast Pacific near the east Pacific rise. This average value agrees well with previous estimates based on gravimetry and GEOS 3 altimetry, In general, the smoothest areas in the marine geoid overlie relatively young sea floor adjacent mid‐ocean spreading centers, where even short wavelength topographic variations tend to be isostatically compensated.
Evaluation of SEASAT SMMR wind speed measurements
Authors: Cardone V. , Chester T. , Lipes R.
Published: February 2008

The SEASAT scanning multichannel microwave radiometer (SMMR) is able to measure the wind speed at the ocean surface through the change in ocean surface microwave emissivity caused by the wind. In this paper we compare the SMMR‐derived wind speeds to the wind speeds derived from an active microwave scatterometer also aboard the SEASAT, the SEASAT A scanning scatterometer (SASS), Four orbits that passed over the severe storm that damaged the Queen Elizabeth II are examined in detail. These orbits and five others were used to investigate effects which degrade the SMMR wind retrievals. When the data are filtered for such effects, we find that the SMMR winds agree with the SASS winds with a scatter (1σ) of less than 2 m/s about a bias of 1 to 2 m/s.
Southern ocean mean monthly waves and surface winds for winter 1978 by Seasat radar altimeter
Authors: Mognard Nelly M. , Campbell William J. , Cheney Robert E. , Marsh James G.
Published: February 2008

Data acquired by the SEASAT radar altimeter during the 3 month satellite lifetime are analyzed in a study of the sea state of the southern hemisphere oceans. The lifetime of the SEASAT satellite, July 7 to October 10, 1978, corresponds to the Antarctic winter. Mean monthly maps of wind speed, significant wave height, and swell have been generated from the altimeter measurements along the satellite tracks. These maps delineate spatial and temporal differences of these parameters in the Atlantic, Indian, and Pacific oceans. Several features of the Southern Ocean wind and wave fields agree with conventional descriptions. For example, the principle zonal wind regimes established by the Southeast Trades and Westerlies are clearly evident in the monthly averages. Significant wave height and swell also exhibit minima near the Doldrums at low latitudes with steady increases southward to the latitudes of the Westerlies. However, superimposed on these general patterns is significant variability with horizontal scales as small as 1000 km. The maps also document a gradual migration of the region of absolute maximum wind and wave from the Atlantic eastward to the Indian Ocean and finally into the Pacific.
SEASAT wave height measurement: A comparison with sea‐truth data and a wave forecasting model—Application to the geographic distribution of strong sea states in storms
Authors: Queffeulou Pierre
Published: February 2008

The SEASAT altimeter derived wave height (‘on‐board’ estimate) has been successfully compared with ship reports over the North Atlantic Ocean, for 163 passes of SEASAT, from September 15 to October 9, 1978. Satellite wave height measurements reveal features of great interest: first, SEASAT data are used to evaluate the spectral wave forecasting model, DSA 5, of the French Meteorological Office (La Météorologie Nationale). Then, the analysis of 26 SEASAT passes through low‐pressure areas shows the geographic distribution of strong sea states in storms and the large variations of wave height over short distances, an important observation for wave modeling and ship routing.
Tropical Pacific sea surface temperatures measured by SEASAT microwave radiometer and by ships
Authors: Liu Cho‐Teng
Published: February 2008

Sea surface temperatures (SST) obtained from the SEASAT scanning multichannel microwave radiometer (SMMR) are compared with in situ SST observations in the eastern and central tropical Pacific Ocean for late July 1978. Comparing pairs of SMMR and ship SST (injection temperatures), we find that the SMMR SSTs are biased 0.90C lower than ship SSTs, with a standard deviation (relative to the bias) of 1.70C. Since ship SSTs tend to concentrate along shipping lanes, while SMMR SST's are distributed nearly uniformly, the statistics based on data‐to‐data comparisons are spatially biased; in addition, there is ambiguity in comparing the spatially averaged (149 km×149 km) SMMR SST against the point‐observed ship SST. These ambiguities in data comparison can be reduced by comparing the SST fields derived from these data. The result shows that the SMMR‐derived SST field (TSMMR) is, on the average, lower than the ship‐derived SST field Tship by 0.80C with a standard deviation of 0.80C. Adjusted for 0.20C to 0.70C warm bias of ship SST [Saur, 1963; Tabata, 1978], this set of SMMR SST has a bias −0.6° to −0.1°C. The difference between rship and TSMMR shows a strong regional dependence, as found in comparing SST fields derived either from different data sets or from the same data set but with different methods [Barnett et al., 1981]. In our case, the standard deviation of the difference between these two fields is found to be inversely proportional to the spatial density of ship data. The implications are that the spatial variation of the SST field may be better derived from SMMR SST than from ship SST, which is handicapped by its nonuniform data distribution, and, after determining the biases of both SMMR and ship SST, these two data sets may complement each other for constructing SST fields.
The temperature and salinity fine structure of the ocean under the Ross Ice Shelf
Authors: Foster Theodore D.
Published: February 2008

A series of temperature and salinity profiles was made in the ocean under the Ross Ice Shelf at 82°22.5′S, 168°37.5′W where the ice was 420 and the underlying seawater 240 m thick. The water structure consisted of a fairly well‐mixed, low salinity layer at the in situ freezing point of the ice‐water interface about 30 m thick, a transition layer characterized by intrusions about 85 m thick, a strongly stratified layer with increasing temperature and salinity about 50 m thick, another transition layer characterized by intrusions about 45 m thick, and an isohaline bottom layer with a nearly abiabatic temperature gradient about 30 m thick. The temperature fluctuations in the two transition layers can be attributed mainly to intrusive activity even though internal wave activity was highest in these regions. In the central stable layer, internal waves probably contribute to the temperature fluctuations equally with intrusions. The internal wave ‘dropped’ displacement spectrum seems to be very similar to those found in the open ocean. Some profiles showed intrusions in the top transition layer colder than the top boundary layer, and some showed intrusions in the bottom transition layer warmer than the bottom boundary layer, indicating that horizontal shear must be present. Internal waves of near inertial frequency excited by the semidiurnal tides combined with shear‐induced instabilities seem to be the likely causes of the observed fine structure.
High‐resolution spectral estimation of synthetic aperture radar ocean wave imagery
Authors: Jackson P. L. , Shuchman R. A.
Published: February 2008

A new two‐dimensional spectral estimation procedure, termed semicausal, is applicable to analysis of ocean gravity waves. Spectral estimates of both reference functions and actual synthetic aperture radar data of ocean waves have been generated using semicausal techniques and compared to fast Fourier transform estimates of identical data sets. The semicausal method can successfully generate spectral estimates of truncated data sets and data sets with two closely spaced frequency components. The semicausal estimate is sensitive to the autoregressive order and exhibits spectral splitting in some cases. Its noise sensitivity is similar to that of the Fourier transform.
A mechanism for the formation of ice edge bands
Authors: Wadhams Peter
Published: February 2008

We propose a mechanism for the formation of multiple bands at an ice edge that is subjected to an off‐ice wind. The wind moves the outermost floes seaward faster than the interior ice, dilating the marginal ice zone and opening up random polynyas. In the largest of the polynyas, the off‐ice wind generates a significant fetch‐limited wave spectrum, which produces a wave radiation pressure on floes at the downwind end of the polynya, increasing their velocity. They are herded against their downwind neighbors, creating a band of high ice concentration. The band is stabilized by an internal compacting stress due to the exponential decay of the wind‐wave spectrum across the band and to a slower decay of swell incident from seaward. The band's growth terminates when it encounters a second downwind polynya of sufficiently large size. We show how an array of ‘immature’ bands generated in this way ‘matures’ by selective mergers into larger, regularly spaced bands of approximately equal width.
Drag measurements for first‐year sea ice over a shallow sea
Authors: Pease C. H. , Salo S. A. , Overland J. E.
Published: February 2008

For a free‐drift case a method is developed for simultaneously determining air (Ca) and water (Cw) drag coefficients by solving the vertically integrated stress balance equation for sea ice. The method allows the algebraic determination of Ca and Cw from measurements of relative wind and relative current at single reference levels, from estimates of the densities of all three fluids and ice thickness, and from estimates of the accelerations caused by the nonsurface stress terms derived from position measurements. The method treats the ice as a natural drag plate and therefore includes contributions from both skin and form drag. One shortcoming of the technique is that if the relative wind and current are colinear, then only the ratio of Ca and Cw can be determined. Another is that the accelerations caused by other forces need to be independently determined. An experiment was conducted on a single floe in the eastern Bering Sea over the continental shelf during March 1981. The site was about 80 km from the ice edge and was occupied for approximately 3 days following the passage of a storm which had broken the pack into 10–20 m diameter floes. Both profile and slab inversion estimates of drag were made from the current meter and anemometer measurements at the site: Ca at 3 m was 4.55×10−3 by the profile method, compared to 3.63–4.39×10−3 for slab, depending on assumptions; Cw at 1.1 m by profile was 24.2×10−3, compared to 18.3–22.0×10−3 for slab. The two methods gave results which were not statistically separable and which were among the highest drags observed for sea ice. The instantaneous stress balance on the floe included contributions from material acceleration, Coriolis force, the two surface stresses, and sea‐surface tilt relative to mean current and tide.
A coupled ice‐ocean model of upwelling in the marginal ice zone
Authors: Røed Lars Petter , O'Brien James J.
Published: February 2008

A dynamical coupled ice‐ocean numerical model for the marginal ice zone (MIZ) is suggested and used to study upwelling dynamics in the MIZ. The nonlinear sea ice model has a variable ice concentration and includes internal ice stress. The model is forced by stresses on the air/ocean and air/ice surfaces. The main coupling between the ice and the ocean is in the form of an interfacial stress on the ice/ocean interface. The ocean model is a linear reduced gravity model. The wind stress exerted by the atmosphere on the ocean is proportional to the fraction of open water, while the interfacial stress ice/ocean is proportional to the concentration of ice. A new mechanism for ice edge upwelling is suggested based on a geostrophic equilibrium solution for the sea ice medium. The upwelling reported in previous models invoking a stationary ice cover is shown to be replaced by a weak downwelling due to the ice motion. Most of the upwelling dynamics can be understood by analysis of the divergence of the across ice edge upper ocean transport. On the basis of numerical model, an analytical model is suggested that reproduces most of the upwelling dynamics of the more complex numerical model.
Measurements of salinity and volume of brine excluded from growing sea ice
Authors: Wakatsuchi Masaaki , Ono Nobuo
Published: February 2008

The volume of brine excluded from growing sea ice and its salinity were measured using a brine sampler. The measurements were made, in both laboratory and field, under various growth conditions of the sea ice. The salinity of the brine becomes higher, and the volume flux decreases as the sea ice growth rate decreases. Consequently, the salt flux of the brine decreases with decreasing growth rate. In the case of sea ice growth at a constant rate, as the sea ice becomes thicker, the salinity of the brine excluded increases while its volume flux decreases. However, the salt flux is nearly independent of the ice thickness increase, at least up to a thickness of 15 cm. For sea ice growth rates between 1.7×10−5 and 1.4×10−4 cm s−1, and for a seawater salinity of 33.0‰, the brine salinity ranged from 42.3‰ to 92.7‰, the volume flux ranged from 6.3×10−6 to 3.4×10−5 cc cm−2 s−1, and the salt flux ranged from 6.4× 0−7 to 1.5×10−6 g cm−2 s−1.
Numerical study of the water movement driven by brine rejection from nearshore Arctic ice
Authors: Kowalik Zygmunt , Matthews J. B.
Published: February 2008

A numerical model of brine‐induced circulation is used to study circulation in the lagoons and shelf waters of the Beaufort Sea. The model solves the equations of motion, continuity, and salt transport. The salt flux is set as a function of the salinity difference between growing sea ice and seawater and the rate of ice growth. Several experimental runs show that under‐ice haline circulation is controlled by salt flux and bottom configuration. An idealized model of a shallow arctic lagoon gives currents of 1 cm s−1 for brine‐induced circulation under landfast ice. This agrees very well with observations.
Acoustic and electric signals from lightning
Authors: Balachandran Nambath K.
Published: February 2008

Observations of infrasound apparently generated by the collapse of the electrostatic field in the thundercloud, are presented along with electric field measurements and high‐frequency thunder signals. The frequency of the infrasound pulse is about 1 Hz and amplitude a few microbars. The observations seem to confirm some of the theoretical predictions of Wilson (1920) and Dessler (1973). The signal is predominated by a compressional phase and seems to be beamed vertically. Calculation of the parameters of the charged region using the infrasound signal give reasonable values.
Crater Lake revisited: Concentration changes in water column radionuclides, 1967 to 1981
Authors: Volchok Herbert L. , Bowen Vaughan T. , Clark William R. , Ball Lary R.
Published: February 2008

A small‐scale resampling of Crater Lake water was carried out in 1981. Water from three depths (surface, 3 m, and 14 m) was obtained and analyzed for 3H, 90Sr, 137Cs, and plutonium. The results indicate that 3H and 90Sr quantitatively remain in the water column and that the lake is well mixed. Twenty‐five percent of the 137Cs and more than 90% of the plutonium has been removed from the water column, presumably into the sediment.
Gulf Stream frontal statistics from Florida Straits to Cape Hatteras derived from satellite and historical data
Authors: Olson Donald B. , Brown Otis B. , Emmerson Steven R.
Published: February 2008

A 5 year record (1976–1980) of weekly Gulf Stream paths digitized from the U.S. Navy Ocean Frontal Analysis is analyzed to define a mean Gulf Stream path and weekly space‐time series of fluctuations about the mean between the Florida Straits and Cape Hatteras. This satellite‐derived Gulf Stream frontal mean locus is used as a natural coordinate system in which NODC historical expendable bathythermograph (XBT) data is averaged to determine the mean cross stream hermal structure. The results show that the satellite‐derived front; that is, the cold wall of the stream as derived from IR imagery is in good agreement with a classical definition of the stream path. The Gulf Stream path is discussed in relationship to the bottom topography. Frontal location time series at various locations along the Gulf Stream are analyzed to generate occupation statistics and spectra for stream position. A steady increase in the variance of stream position occurs from Cape Canaveral to the Charleston Bump. This trend is followed by a sharp increase in variance just downstream of the bump and then a gradual decay from approximately 33°N to Cape Hatteras. A similar distribution of variance is found in the depth of the 15°C isotherm. An annual signal is seen in the path data all along the U.S. east coast. The stream front north of Charleston (∼32°N) exhibits the strongest annual variation with the surface front being further offshore in the late winter and early spring. This annual signal is not obvious at the thermocline level (15°C). It is consistent, however, with observed shifts in the isotherm patterns in the upper 100 m.
Diagnostic and prognostic numerical circulation studies of the South Atlantic Bight
Authors: Blumberg Alan F. , Mellor George L.
Published: February 2008

Some of the results from a series of diagnostic and prognostic numerical simulations of the circulation in the South Atlantic Bight (SAB) are described. The numerical model developed for the study is a three‐dimensional, primitive equation, time dependent, σ coordinate model with an imbedded, turbulent closure submodel which should yield realistic Ekman surface and bottom layers. An implicit numerical scheme in the vertical direction and a mode‐splitting technique in time are adopted for computational efficiency. A significant portion of the paper is concerned with realistic specification of initial conditions for temperature and salinity, surface forcing, and lateral open boundary conditions. The latter are determined by a simple diagnostic (geostrophic and Ekman dynamics) model which provides dynamically consistent temperature, salinity, and velocity boundary conditions. It appears from an exaination of the numerical simulations that the full model yields results that share many features in common with our general understanding of the circulation of the South Atlantic Bight; the region includes shallow shelf waters as well as deeper water dominated by the Gulf Stream. Data for synoptic skill assessment, however, are not available.
Distribution of Antarctic intermediate water over the Blake Plateau
Authors: Atkinson Larry P.
Published: February 2008

During a cruise in September 1980 over the Blake Plateau we observed a northward spread of Antarctic Intermediate Water (AAIW) in the main axis of the Gulf Stream. The AAIW appeared as a lobe less than 60 km wide extending to at least 31°N. The lobe was characterized by negative salinity anomalies of 0.15×10−3, elevated nutrient concentrations, and lowered oxygen concentrations. Tentative evidence suggests that a parcel of AAIW was located over the central Blake Plateau, and geostrophic calculations indicate it may have been attached to the main Gulf Stream deep flow.
Orbital forcing, climatic interactions, and glaciation cycles
Authors: Le Treut Hervé , Ghil Michael
Published: February 2008

We consider forced oscillations of a nonlinear climatic oscillator. The oscillator includes radiation balance, oceanic thermal inertia, a highly simplified hydrological cycle, the mass balance and plastic flow of ice sheets, the elasticity of the earth's crust, and the viscosity of its upper mantle, as well as their various interactions. This system exhibits self‐sustained periodic oscillations with amplitude of a few degrees Celsius in the absence of any periodic forcing. The oscillator's free period, depending on model parameters, lies roughly between 5000 yr and 15000 yr (5–15 ka). The model is subjected to forcing at the astronomical periodicities of precession, 19 and 23 ka, obliquity, 41 ka, and eccentricity, 100 ka and 400 ka. The forcing is assumed to act on the climatic system by variations in mean annual insolation, in the case of eccentricity, as well as by its effect on the ice‐mass balance through the nonlinear precipitation‐temperature feedback.

The effects investigated only cause small changes in ice mass V and global temperature T when self‐sustained oscillations are absent. In their presence, nonlinearly resonant response to the forcings leads to large changes in T and V; this response obtains at the frequency of the forcing, due to the mechanism of entrainment. The nonlinear character of the response also leads to combination tones. These are linear combinations of the forcing frequencies with integer coefficients, among which the largest occur near 100 and 10 ka. Sharp peaks in spectral density at the forcing frequencies and at their combination tones are superimposed on a continuous background. The spectral power in the background decreases with increasing frequency, like random red noise. This deterministic aperiodic behavior limits the predictability of glaciation cycles.