bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of seasonal variation upon the sensitivity of a model climate
Authors: Wetherald Richard T. , Manabe Syukuro
Published: February 2008

This study investigates the influences of the seasonal variation of solar radiation based upon the results of numerical experiments with a mathematical model of climate. The model consists of (1) a general circulation model of the atmosphere, (2) a heat‐and water‐balance model of continents, and (3) a simple mixed layer model of the ocean. It has a limited computational domain and idealized geography. Two versions of the model are constructed. In the first version of the model (the seasonal model), a seasonal variation of insolation is imposed at the top of the model atmosphere. On the other hand, an annual mean insolation is prescribed for the second version of the model (the annual model). The response of the seasonal model to the quadrupling of CO2‐concentration in air is compared to the corresponding response of the annual model. It is found that the response of the annual mean surface air temperature of the seasonal model is significantly less than the corresponding response of the annual model. The smaller sensitivity of the seasonal model is attributed to the absence of strongly reflective snow cover (or sea ice) during the summer when the insolation has a near‐maximum intensity. A comparison between the hydrologic responses of the seasonal and the annual models indicates that the latitudinal distributions of these responses have qualitatively similar zonal mean features. However, the zonal mean response of the seasonal model is found to have considerable seasonal variations. For example, in summer the zonal mean soil wetness is reduced extensively over two separate zones of middle and high latitudes in response to the CO2 increase, respectively. Owing to the seasonal variation mentioned above, the latitudinal variation of the annual mean hydrologic response of the seasonal model is less than that of the corresponding response of the annual model.
Tracking Hurricane Anita by HF skywave radar
Authors: Maresca Joseph W. , Carlson Christopher T.
Published: February 2008

Hurricane Anita was tracked across the Gulf of Mexico from August 29, 1977, to September 2, 1977, by using an HF skywave radar. The radar position estimates were made from California, three to five times per day, at the SRI‐operated Wide Aperture Research Facility (WARF). The storm center was located by using the WARF‐derived ocean surface wind direction maps. Seventeen independent wind maps were used to develop the WARF‐derived track. The WARF‐derived positions were compared to coincident temporal positions on the official track produced by the National Hurricane Center, and the relative agreement was 19 km.
The influence of bandwidth on the distribution of heights of sea waves
Authors: Larsen L. H.
Published: February 2008

In a recent paper, Longuet‐Higgins [1980], using theoretical arguments, estimated a relation between the mean Square wave amplitude and variance of the signal for a wave field composed of waves of different frequencies. Using data collected in 90 m of water from the Washington continental shelf, we confirm the trend for the influence of bandwidth on the ratio, ā2/2m0, which was predicted by Longuet‐Higgins. The mean square wave amplitude is ā2, and m0 is the variance of the wave record.
The influence of optical water type on the heating rate of a constant depth mixed layer
Authors: Zaneveld J. Ronald V. , Kitchen James C. , Pak Hasong
Published: February 2008

A simple heat budget model for a radiation‐dominated mixed layer of constant depth is presented. In this model the influence of the vertical irradiance (heat flux) profile is examined by means of the Jerlov [1976] optical water type classification. It is shown that the vertical irradiance profile is important in determining the mixed layer heating rate. The heating rate varies greatly as a function of water type, mixed layer depth, and diffusivity beneath the mixed layer, ranging from 0.098°C/day for oceanic water type I with a mixed layer depth of 20 m and diffusivity beneath the mixed layer of 1.0 cm2 s−1 to 0.316°C/day for coastal type 9 with a mixed layer depth of 10 m and zero diffusivity beneath the mixed layer, a variation of more than a factor of 3.
On the sensitivity of numerical weather prediction to remotely sensed marine surface wind data: A simulation study
Authors: Cane Mark A. , Cardone Vincent J. , Halem Milton , Halberstam Isidore
Published: February 2008

A series of observing system simulation experiments has been performed to assess the potential impact of marine surface wind data on numerical weather prediction. Care was taken to duplicate the spatial coverage and error characteristics of conventional surface, radiosonde, ship, and aircraft reports. These observations, suitably degraded to account for instrument and sampling errors, were used in a conventional analysis‐forecast cycle. A series of five 72‐hour forecasts were then made by using the analyzed fields as initial conditions. The forecast error growth was found to be similar to that in operational numerical forecasts. Further experiments simulated the time‐continuous assimilation of remotely sensed marine surface wind or temperature sounding data in addition to the conventional data. The wind data were fabricated directly for model grid points intercepted by a Seasat‐1 scatterometer (SASS) swath and were placed in the lowest active level (945 mbar) of the model. The temperature sounding experiment assimilated error‐free data fabricated along actual Nimbus orbits. Forecasts were made from the resulting analysis fields, and the impact of the simulated satellite data was assessed by comparing these forecast errors with those of the control forecasts. When error‐free winds were assimilated by using a localized successive correction method (SCM), the impacts in extratropical regions proved to be substantial, especially in lower tropospheric quantities such as surface pressure. In contrast, a less sophisticated assimilation method resulted in negligible impact. The assimilation of error‐free sounder data (again by the SCM) gave impacts comparable to the wind data, suggesting that surface wind data alone may be as valuable as temperature soundings for numerical weather prediction. The effects of nominal SASS errors (±2 m/s in magnitude, ±20° in direction) on the impacts derived from wind data were found to be small.
Evidence for a traveling two‐day wave in the middle atmosphere
Authors: Rodgers C. D. , Prata A. J.
Published: February 2008

Evidence is presented for the existence of a wave number 3, westward traveling 2‐day oscillation in the temperature measurements made by the Nimbus 5 SCR and Nimbus 6 PMR instruments. The wave has largest amplitude in the mesosphere at low latitudes of the summer hemisphere and has a markedly asymmetrical meridional structure. It is suggested that the wave may be a free wave similar to the 5‐day wave identified in Nimbus 5 SCR data by Rodgers (1976). The vertical structure shows little phase tilt and a slight indication of an increase in amplitude with height.
Inertio‐gravity wave induced accelerations of mean flow having an imposed periodic component: Implications for tidal observations in the meteor region
Authors: Walterscheid R. L.
Published: February 2008

The semidiurnal harmonic exhibits great day‐to‐day variability in amplitude and phase. In addition, the variability appears to be substantially local and random, suggesting a connection with gravity wave activity. We suggest that a significant contribution to the observed semidiurnal harmonic at meteor heights might result from inertio‐gravity wave induced accelerations of the mean flow. The rate of wave forcing of the mean wind is related to the Doppler‐shifted phase velocity, so that during alternate phases of an imposed mean wind oscillation interactions with waves that accelerate the mean wind in opposite senses may be favored. Thus the imposed mean wind may modulate the mean‐flow acceleration at the imposed frequency. In this view, the semidiurnal character of the acceleration is a manifestation of the modulation of the interaction process by the semidiurnal tide. The variability of the semidiurnal harmonic would then reflect the local variability of inertio‐gravity wave fluctuations and also nonlinear feedback on the waves. Calculations with a simple time‐dependent wave‐mean‐flow model indicate that a wave‐induced component of the semidiurnal harmonic with amplitudes comparable to the semidiurnal tide itself is possible.
A quantitative approach to long‐range prediction
Authors: Madden Roland A.
Published: February 2008

Considerations are presented which allow for a more quantitative approach to the problem of long range prediction. It is supposed that the interannual variance of time‐averaged meteorological data is composed of approximately separable components. One component called ‘climate noise’ reflects sampling variability of finite time‐averaged weather fluctuations, and it is unpredictable at long lead times. The remaining variance is assumed to be potentially predictable. Climate noise and potential predictability of winter mean temperature are estimated for United States stations. It is further supposed that the potentially predictable part is composed of a component that we cannot now predict and ‘signals’ that we can. A signal is assumed to be in hand through lag correlations associated with the southern oscillation. The impact of the total unpredictable part of the variance, or ‘effective noise,’ on the usefulness of this signal is discussed. The task of improving the value of long‐range forecasts is described as one of transferring more and more of the potentially predictable variations to actually predictable signals.
Nitrogen on Jupiter: A deep atmospheric source
Authors: Prinn Ronald G. , Olaguer Eduardo P.
Published: February 2008

A study of irreversible reactions involving molecular nitrogen on Jupiter indicates that vertical motions are sufficiently rapid in the deep atmosphere to transport large amounts of N2 from the 900°–1700°K levels where it is stable up to the cold visible regions. Both homogeneous gas‐phase and heterogeneous iron‐catalyzed reactions between N2 and H2 were considered. We predict N2 mixing ratios of 0.6–3 ppmv if catalysis is effective and up to 10 ppmv if it is not. Thus N2 may be the most abundant nonequilibrium species in Jupiter's troposphere and potentially detectable by the neutral mass spectrometer which will be on board the 1986 Galileo Entry Probe.
Simulation of the effects of surface fluxes of heat and moisture in a mesoscale numerical model: 1. Soil layer
Authors: McCumber Michael C. , Pielke Roger A.
Published: February 2008

A parameterization for bare soil is developed, which is to be incorporated in a mesoscale numerical prediction model. This parameterization is generalized to accomodate 11 types of soil in addition to peat, using mean soil characteristics. The sensitivity of the scheme to several soil parameters is evaluated by a series of one‐dimensional simulations. It is shown that the most important soil characteristic is the soil moisture, which regulates the strength of the heat fluxes between the atmosphere and the ground.
Methane in the upper water column of the northwestern Gulf of Mexico
Authors: Brooks James M. , Reid David F. , Bernard Bernie B.
Published: February 2008

Shallow subsurface dissolved methane maxima were commonly observed in the northwestern Gulf of Mexico during a series of cruises between 1975 and 1977. Although there were often several methane maxima at various depths at any one particular station, the most prevalent and widespread occurred over a narrow band of σt, in a range from 24 to 26 and could be traced as layers extending along and outward from the continental shelf. These layers generally followed the local stratification and were associated with the upper part of the pycnocline. Advection was undoubtedly of importance in determining the extent and distribution of these methane maxima layers, but in situ production appears to have supported them. Some vertical profiles revealed associations between methane, ATP, and suspended matter maxima. It is postulated that methane forms in situ in reducing microenvironments associated with suspended participates, which are advected from the shelf or which have accumulated in the upper pycnocline due to increase in buoyancy forces.
The effect of a geographical cloud distribution on climate: A numerical experiment with an atmospheric general circulation model
Authors: Meleshko V. P. , Wetherald R. T.
Published: February 2008

This study is an attempt to estimate the effect of a geographical distribution of clouds on climate. A method of determination of a three‐dimensional cloud distribution is proposed. It is based on the solution of the inverse problem for the radiative transfer equation. By using climatic data on total cloud amount, temperature, mixing ratio of water vapor, and satellite data on outgoing longwave radiation, the global distributions of high, middle, and low clouds were computed for July. The derived vertical cloud extension is in fair agreement with available data on the frequency distribution of stratiform and cumulus clouds. Two numerical experiments are carried out with an atmospheric general circulation model in which zonal and geographical cloud distributions are prescribed. The integrations are performed for 60 days with a GFDL model, and the last 30 days are analyzed. The geographical cloud distribution causes the increase of surface temperature over the continents by 2°–4° and leads to a decrease of surface pressure there and an increase over the oceans. The largest changes in the surface pressure, up to ±12 mbar, occur in the middle latitudes of both hemispheres. The largest differences in precipitation are observed in the tropics and over some coastal regions of North and South America. Arid areas in the subtropical belt become more pronounced in case of the geographical distribution of clouds. Estimates of the level of significance for precipitation and surface pressure changes reveal that they are statistically significant in some areas of the globe.
A two‐dimensional model of stratospheric chemistry and transport
Authors: Miller C. , Filkin D. L. , Owens A. J. , Steed J. M. , Jesson J. P.
Published: February 2008

A two‐dimensional chemical model of the atmosphere is described. The model includes the major features associated with advanced one‐dimensional models: 30 active chemical species and all the important chemical reactions connecting them, diurnal effects, and Rayleigh scattering. The species are transported and calculated separately, with the exception of the odd oxygen family [O3, O(3P), O(1D)] and H and N atoms. The transport scheme contains both diffusive and advective terms, with the advective circulation field of Murgatroyd and Singleton (appropriately scaled) used to approximate the Lagrangian mean flow. Comparison of the model predictions with atmospheric observations of long‐lived trace species such as O3, N2O, CF2Cl2, CFCl3, and CH4 suggests that the transport parameterization gives a good representation of actual trace species motions. For constituents which are more active or whose chemistry is less well known, the model is a useful diagnostic tool for assessing our current understanding of atmospheric chemistry. A number of significant discrepancies between experiment and theory are highlighted, the most important being in the Clx and NOy families.
Detection of nighttime atmospheric scattering of lunar UV radiances by the Nimbus 4 BUV instrument
Authors: Stassinopoulos E. G. , Goldberg R. A. , McPeters R. D. , Barth J. M.
Published: February 2008

Morphological studies of nighttime dark current data from the Nimbus 4 backscattered UV experiment clearly indicate enhancements during the period of the full moon. This analysis is based on processed and filtered data which have other known perturbations induced by energetic particle events. In order to obtain truly quiescent dark current background values for the 5‐day study intervals centered about several full moon sequences and for the corresponding new moon intervals, the data were further screened so that isolated elements showing spurious or abnormal enhancements could be removed selectively (∼3%). The results demonstrate the presence and uniqueness of a lunar signal, induced by atmospherically backscattered UV radiation. On the Nimbus 4 instrument this signal is not sufficiently strong to provide an accurate map for global nighttime ozone. However, these results do suggest this as a potential application for future, more sensitive instruments.
Exchange of water vapor between land and ocean in the northern hemisphere
Authors: Rosen Richard D. , Omolayo Aribilola S.
Published: February 2008

Maps of the total amount of water vapor carried by the winds across each segment of coastline in the northern hemisphere are presented for each season. This cross‐coastal flux shows considerable variability over the hemisphere but tends to be largest in the tropics and during summer. The zonal net value of this flux is computed for each 10° belt of latitude. In the annual average, the zonal net value is landward in the tropics, but alternating belts of landward and oceanward zonal net flux exist in mid and high latitudes.
Internal modes in a submarine canyon
Authors: Gordon R. L.
Published: February 2008

A simple analytical model is presented for internal waves in a slot of variable width. This model is used to explain the vertical wave length, directional character, and amplitude enhancement of internal waves observed near the axis of La Jolla Submarine Canyon, offshore of San Diego, California.
The influence on rain chemistry of the Hawaiian Volcano Kilauea
Authors: Harding Duane , Miller John M.
Published: February 2008

From May 1978 through February 1979, 334 samples of rain were collected on a twice‐weekly basis in the summit area of Kilauea Volcano, Hawaii. Throughout the period the volcano was in a noneruptive state. The samples were analyzed for pH and conductivity as well as for the concentration of the anions F−, Cl−, NO2−, PO4−3, Br−, NO3−, and SO4=. At a distance of 0.8 km downwind of the degassing center, rainwater pH was observed to be as low as 3.0 and to have a median pH of 3.6. The maximum observed concentration of SO4= was 36 mg/l. The median pH 11 km downwind was 4.2, which approached the pH measured in precipitation on the island uninfluenced by the volcanic emissions.
Gravity model improvement for SEASAT
Authors: Lerch F. J. , Marsh J. G. , Klosko S. M. , Williamson R. G.
Published: February 2008

Analysis of the data from the SEASAT altimeter, a 10‐cm precision instrument, requires accurate knowledge of the radial position of the spacecraft for oceanographic applications such as the study of tides and ocean circulation as well as for geodetic applications. Initial orbit determinations using the best available geodetic and force models gave radial errors approaching 5 m. The dominant source of this radial error was the gravity field model. Improvements in the gravity modeling were made by successively incorporating the SEASAT laser and Unified S Band ground tracking data, the GEOS 3 altimeter data, and finally, the SEASAT altimeter data. With the most recent model (a set of spherical harmonic coefficients complete to degree and order 36), SEASAT ephemerides have been computed for an orbital arc length of 12 days with an rms radial accuracy of about 70 cm.
Chemistry of south polar snow
Authors: Delmas Robert , Briat Martine , Legrand Michel
Published: February 2008

The chemical composition of trace impurities present in recent Antarctic snow is reviewed and interpreted. In coastal areas, sea salt is found to be important, while at the South Pole this contribution is much lower (10–15% of the bulk deposition). Insoluble impurities play a negligible role. Gas‐derived ions (SO4, NO3, NH4, Cl) are the major components deposited in central Antarctica, the anions forming the more important fraction. When considering the ionic budget of these impurities, the proton is dominant. The Antarctic snow meltwater can therefore be described as a very diluted mixture of natural acids (most likely H2SO4 and HNO3) containing a small amount of neutral salts. The possible sources of all these chemical species are briefly discussed.
Sill processes related to deep water renewal in a fjord
Authors: Geyer W. R. , Cannon G. A.
Published: February 2008

Observations of the gravitational circulation over the sill at the entrance to Puget Sound indicate a fortnightly modulation of the two‐layer flow with a corresponding variation in stratification. Gravitational circulation and stratification reach a maximum during neap tides and a minimum during spring tides. The modulation appears to be a function of the turbulence generation by tidal flow over the sill, which varies as a function of tidal amplitude. The enhanced gravitational circulation during neap tides augments the flux of dense water across the sill region and episodes of bottom water renewal in Puget Sound result. Intrusions of dense water in the main basin of the sound show a fortnightly periodicity with a phase lag appropriate for the propagation of an internal bore from the sill region, commencing at the neap tide. Observations indicate that the intrusions take the form of gravity currents, propagating at approximately 20 cm s−1 down the main basin. The detailed dynamics of the turbulent mixing processes that modulate the onset of inflow were not resolved in this study, but the integrated effect of tidal mixing on the low‐frequency circulation is clearly demonstrated.
Magnitudes and sources of precipitation and dry deposition fluxes of indestrial and natural leads to the North Pacific at Enewetak
Authors: Settle Dorothy M. , Patterson Clair C.
Published: February 2008

A total atmospheric Pb input flux of 7 ng Pb cm−2 yr−1 was measured in the North Pacific Easterlies at Enewetak. Parameters used to measure this flux were ratio of dry deposition flux to precipitation flux; Pb/210Pb in precipitation and seawater; 210Pb flux; washout factor; and Pb concentrations in air, rain, and dry deposition deposits. Relations among these parameters established at Enewetak were used to recompute and confirm previous estimates of lead fluxes to the oceans (ng Pb cm−2 yr−1) at the following locations: North Atlantic Westerlies, 170; North Pacific Westerlies, 50; and South Pacific Easterlies, 3. Prehistoric lead output fluxes to sediments (ng Pb cm−2 yr−1) at these locations have been previously measured and were 4 (Enewetak); 30 North Atlantic Westerlies; 3 North Pacific Westerlies; 4 South Pacific Easterlies. These data show that the rates of atmospheric inputs of lead to the oceans vary directly with variations in rates of upwind emissions of industrial lead from urban complexes on land. In the North Pacific and North Atlantic, present rates of atmospheric lead inputs are 10‐fold greater than prehistoric outputs. In equatorial regions, present inputs and past outputs are more nearly equal. These observations disclose the effects of intense industrial atmospheric emissions of lead in the northern hemisphere westerlies which have overwhelmed prehistoric natural fluxes of lead to the oceans. The average concentration of lead in marine air at Enewetak is 170 pg m−3 and varies less than a factor of 2 from that mean. One to 15% of this lead comes from seaspray, while the remainder comes from sources on land. About 90% of the seaspray lead is industrial, while 80 to 99% of that originating from land sources is industrial. Concentrations of lead in rain at Enewetak range from 6 to 63 pg/g with a mean value of 28. The mean precipitation flux, corrected for recycled lead in sea salts, measured by four different methods, was 6 ng Pb cm−2 yr−1, while the net dry deposition flux measured on horizontal plastic plates was 0.6 ng Pb cm−2 yr−1. The total dry deposition flux measured was 6 ng cm−2 yr−1, but 90% of this lead came from recycled seaspray. Lead isotope tracers show that Japan is the major source of industrial lead at Enewetak during the dry season, while the United States is the major source during the wet season.
Whitecap aerosol productivity deduced from simulation tank measurements
Authors: Monahan E. C. , Davidson K. L. , Spiel D. E.
Published: February 2008

An estimate of dF0/dr, the sea spray aerosol production per increment droplet radius per unit time per unit area of the ocean, has recently been obtained from a term‐by‐term evaluation of the following expression: dF0/dr = dE/drτ−1W(U). The differential whitecap aerosol productivity, dE/dr, the number of aerosol droplets per increment droplet radius produced during the decay of a unit area of whitecap, has been redetermined, for the size range 0.8 μm < r < 8 μ, from the results of recent experiments in the University College, Galway, whitecap simulation tank in which Particle Measuring Systems aerosol spectrometers were used. The characteristic decay time for whitecaps, τ, and the initial whitecap area were in the present study determined from the frame‐by‐frame analysis of cine‐film recordings of whitecaps generated in the simulation tank. The fraction of the sea surface covered by whitecaps W at wind speed U was taken from Monahan and O'Muircheartaigh (1980). The resulting expression, representing the local sea surface aerosol source function in units of m−2 s−1 μm−1 appropriate for inclusion in any model for the prediction of the vertical profile of aerosols within the marine boundary layer, is given by dF0/dr = 5.77 × 10−6U3.41 (ΔdN/dr), where the last term represents the change in aerosol concentration per increment droplet radius, expressed in m−3 μ−1, that occurs in the air within the hood over the tank when an individual whitecap decays.
The subtropical front: Satellite observations during FRONTS 80
Authors: Van Woert Michael
Published: February 2008

Satellite‐derived sea surface temperature, in situ hydrography data, and satellite‐tracked drifter data collected during winter 1979–1980 as part of the FRONTS 80 experiment are used to describe the spatial structure of the North Pacific subtropical front northeast of Hawaii. The satellite observations reveal a deformation scale meander (85 km × 32 km) in association with the front having an evolution time scale of ∼60 days. The satellite measurements of the change in sea surface temperature across the front are typically 1°C within a distance of 10 km. The correlation coefficients between the satellite data and the in situ hydrographic data were computed and found to be significantly nonzero above 800 m. The high correlation at deep levels indicates that the satellite was viewing a feature with sizable vertical extent, not just a surface phenomenon. Additionally, the hydrographic data and drifter trajectories were combined with the satellite‐derived sea surface temperature data. Together they demonstrate that the feature observed by the satellite was nearly stationary during the experiment period. In addition, they also indicate that the flow along the front was nearly in geostrophic balance.
Gas exchange across an air‐water interface: Experimental results and modeling of bubble contribution to transfer
Authors: Merlivat Liliane , Memery Laurent
Published: February 2008

Gas exchange experiments have been performed in a wind‐water tunnel filled with fresh water or seawater. Transfer velocities have been measured for nitrous oxide and argon in a range of wind speeds extending from 3 m/s to 14 m/s. The air‐liquid interface was covered either with only normally developed wind waves or with mechanically generated waves in addition. For u<9 m/s a linear variation of the transfer velocity, kL, with wind speed (and also friction velocity) is observed for both gases. Two distinct relationships link kL and u, depending on the presence of artificially generated waves. In this last case, a mean enhancement of the order of 30% is observed. The ratio of the transfer velocities measured for Ar and N2O is equal to 0.93. This figure does not allow the precise determination of the dependence of kL on the Schmidt number of the gas since molecular diffusivities of Ar and N2O in water are close and not precisely known. For higher wind speeds (u>9 m/s), a jump of the values of kL up to a factor of 3 is observed first for Ar and then for N2O, the ratio kL Ar/kL
being highly variable. This observation is interpreted as being the result of the onset of breaking waves which create bubbles through which mass transfer takes place. No difference for gas exchange either in fresh water or in seawater has been identified from the whole set of experiments. A theoretical model is developed to compute the contribution of bubbles to gas exchange. The transport equations, derived for a single bubble, take into account the diffusive mass flux exchanged between the bubble and the liquid, the hydrodynamic pressure, and the presence of two gaseous components inside the bubble. The equations used to represent the dynamics take care of the orbital motion of water associated with waves. A relation to link sources and spectra of bubble populations is derived. Numerical values for spectral parameters are taken from the literature. It is found that the results of experiments run at 9 m/s and 10 m/s are well explained for N2O and for Ar. A unique distribution of bubbles explains the excess of gas transfer associated with the presence of breaking waves. In a further step the theoretical treatment is extended to compute the transfer velocity kB for gas exchange through bubbles as a function of the concentration gradient in atmosphere and water for three gases, helium, argon, and nitrous oxide. It is shown that in wind tunnel conditions, kB is independent of the concentration gradient. This does not hold at the atmosphere‐ocean interface. The transfer velocity kB is highly dependent on the gas concentrations in air and water when they are close to solubility equilibrium. It is demonstrated that equilibrium must occur at the ocean surface for supersaturation conditions. The higher saturation anomalies and the larger transfer velocities are computed for the less soluble gas. This conclusion is in good agreement with observations made at sea.
Interaction of the Antarctic Circumpolar Current with bottom topography: An investigation using satellite altimetry
Authors: Colton Marie Tippin , Chase Robert R. P.
Published: February 2008

Theoretical studies on the interaction of a zonal current with a zonal ridge, an isolated bump, and a meridional ridge compare favorably with hydrographic observations within the eastward flowing Antarctic Circumpolar Current where it flows over similar topographic features. However, the existing hydrographic data are insufficient for examining the temporal stability and kinematic behavior of the resulting mesoscale structures. In this study, some of these transient features have been compared with patterns in sea surface variability, derived from collinear satellite altimetric data. When these features occurred near the crossing point of two satellite ground traces, it was possible to characterize their length scales, dynamic height relief, and translational and surface geostrophic velocities.
Multiyear sea ice variability in the eastern Bering Sea: An update
Authors: Niebauer H. J.
Published: February 2008

Time series of sea surface temperature (SST), percent ice cover, degree day, and surface wind anomalies are updated from Niebauer [1980] for the period 1974–1982 from the eastern Bering Sea. These data are used to provide further documentation of the recent short‐term (∼1977‐present) climatic warming trend in the region of the eastern Bering Sea. The data analysis indicates that the warming trend is statistically significant and that it ended in 1979. Details of the anomalies in SST, ice and surface, and 700‐mbar winds are updated for the individual winters of 1979–82, are compared and contrasted to the recent multiyear warming trend and are discussed in relation to longer‐term studies of air‐ice‐sea interactions in this region.
Oceanographic conditions in the marginal ice zone north of Svalbard in early fall 1979 with an emphasis on mesoscale processes
Authors: Johannessen O. M. , Johannessen J. A. , Morison J. , Farrelly B. A. , Svendsen E. A. S.
Published: February 2008

During September–October 1979 the Norwegian Remote Sensing Experiment was carried out in the marginal ice zone north of Svalbard. Convergence of the ice cover is correlated with along‐ice edge winds with the ice to the right, while divergence occurs during office winds or calm conditions. A wind‐driven ice edge jet is observed. Wind‐driven upwelling of the pycnocline of up to 7 m was present along the ice edge during a 10‐ to 15‐m/s easterly wind event. The upwelling is due to Ekman divergence at the ice edge, caused by higher wind stress over ice than over open water. The ice edge meanders with a scale of 20–40 km and sheds eddies with a scale of 5 to 15 km into the open water. This scale is of the same order as the Rossby radius of deformation. Eddies with the same scale are also seen in the conductivity, temperature, and depth observations. Conditions during the experiment were such that barotropic instabilities could have generated these eddies.
An ice‐water vortex at the edge of the East Greenland Current
Authors: Wadhams P. , Squire V. A.
Published: February 2008

During the Y mer‐80 cruise in August 1980 we observed an ice feature of 60‐km diameter having the shape of a breaking wave. It lay at the edge of the East Greenland drift ice in Fram Strait with its center at 79°15′N, 00°38′E, and the wave was breaking upstream relative to the East Greenland Current. Two conductivity, temperature, and depth sections across the feature in N‐S and E‐W directions revealed warm (up to 4.3°C) water some 60 km inside the polar front, in lenses centered at 40‐m depth but with an effect to beyond 600 m. The temperature anomalies were accompanied by salinity anomalies so that there was little net effect on the density profile. The form of the sections, together with the ice distribution (observed by vertical photography from a helicopter) and surface motion (observed by tracking four radar transponders) all suggest that the feature is a vortex produced by an instability in the polar front. It has similar characteristics to vortices investigated experimentally and theoretically by Griffiths and Linden (1981a, b, 1982) and observationally by Wadhams et al. (1979).
An investigation of a polynya in the Canadian Archipelago: 2. Structure of turbulence and sensible heat flux
Authors: Smith S. D. , Anderson R. J. , Hartog G. Den , Topham D. R. , Perkin R. G.
Published: February 2008

The Dundas Island polynya is a natural laboratory for the study of atmospheric turbulence and heat exchange between the Arctic Ocean and the atmosphere in extreme (20–34°C) sea‐air temperature differences. A sonic anemometer‐thermometer measured wind and temperature fluctuations at a height of 4.4 m at the downwind edge, where turbulent heat flux was characteristic of the surface flux from the polynya. Profiles of wind, temperature, and temperature fluctuations were also measured. Temperature ramps associated with the passage of convective plumes give skewed temperature distributions. Sensible heat flux is related to wind speed and sea‐air temperature difference by a stability‐dependent bulk coefficient. Formulas describing turbulence structure in convective boundary layers in terms of ‘similarity’ theory are verified and compared with published results taken in less extreme temperature gradients. By using these formulas, heat flux can be estimated from either temperature variance or temperature spectra.
An investigation of a polynya in the Canadian Archipelago: 3. Surface heat flux
Authors: Hartog G. Den , Smith S. D. , Anderson R. J. , Topham D. R. , Perkin R. G.
Published: February 2008

The heat loss from the Dundas Island polynya is calculated for a 3 week period during March 1980. Bulk and free convection formulae based on sonic anemometer‐thermometer measurements are used to calculate the sensible and latent heat fluxes. These terms, along with simple models to calculate the albedo and the long‐wave radiation exchanges, yield a surface heat budget for the polynya. The sensible heat flux for the period March 12, 1980, to April 1, 1980, averaged 204 W/m2 and the mean total heat loss from the polynya was 329 W/m2.
The global distribution of atmospheric carbon dioxide: 2. A review of provisional background observations, 1978–1980
Authors: Fraser P. J. , Pearman G. I. , Hyson P.
Published: February 2008

An attempt is made to bring together provisional data collected throughout the world to construct a global picture of the background atmospheric carbon dioxide concentration distribution. The uncertainties, calibration and sampling difficulties, and measurement needs are discussed, and it is concluded that in general the accuracy of the provisional data at each sampling location is ∼±1 ppmv. Ongoing studies at the main laboratories are likely to significantly improve this accuracy in the near future. The most recent data available (for 1980) indicate annual average northern hemisphere high latitude CO2 concentrations 4 to 5 ppmv above those at high latitudes of the southern hemisphere (∼336 ppmv). The greatest uncertainty in the zonal average concentration exists in the latitude band 10–30°N where surface observations are 2–3 ppmv higher than those measured by continuous analysis at the Mauna Loa Observatory. There is generally good agreement between a model‐generated and the observed annual mean global distributions. The seasonality of concentration is small in the southern hemisphere (∼1–2 ppmv peak to peak) rising to ∼6 ppmv at 20°N and ∼15 ppmv at high latitudes of the northern hemisphere. The total global atmospheric CO2 content, averaged through 1980, is estimated to have been 7.15×1014 kg of carbon with a probable uncertainty of 0.5 to 1.0%.
On the wave number spectrum of oceanic mesoscale variability observed by the SEASAT altimeter
Authors: Fu Lee‐Lueng
Published: February 2008

Variations of sea surface height measured by the SEASAT altimeter in nearly repeat orbits during the last 24 days of the mission are used to compute the wave number spectrum of mesoscale variability in various parts of the oceans. The instrument noise level ( ∼150 cm2/cycles/km) has limited the resulting oceanic spectrum to wavelengths longer than 100 km. We found that the characteristics of the oceanic spectrum are dependent on the energy level of the mesoscale variability. In the high‐energy areas close to major current systems, most of the energy is contained at wavelengths longer than 250 km. At wavelengths shorter than 250 km the spectrum basically follows a k−5 (k is wave number) dependence. In the low‐energy areas remote from major current systems the spectrum follows a k−1 dependence at wave‐lengths from 100 to 1000 km. Based on the assumption of horizontal isotropy of mesoscale variability, scalar‐wave number spectra of sea surface height and geostrophic kinetic energy are also presented. Dynamical implications of these spectra are discussed. The effects of residual geoid and atmospheric water vapor on the computed oceanic spectra have been rigorously examined; it was found that the general characteristics of the oceanic spectra were not significantly affected by them.
Low‐frequency current and temperature variability from Gulf Stream frontal eddies and atmospheric forcing along the southeast U.S. outer continental shelf
Authors: Lee Thomas N. , Atkinson Larry P.
Published: February 2008

Low‐frequency current and temperature time series from the outer shelf between Cape Canaveral, Florida, and Cape Romain, South Carolina, are compared with shipboard hydrographic data, satellite VHRR, coastal and buoy winds, and coastal sea level during the period from February to June 1980. Low‐frequency current and temperature variability along the shelf break was primarily produced by cyclonic, cold core Gulf Stream frontal eddies. These disturbances traveled to the north at speeds of 50 to 70 cm s−1 with periods of 5 to 9 days throughout the experiment and produced cold cyclonic perturbations of the northward mean flow and temperature fields over an along‐shelf coherence scale of 100 km. Frontal eddies appear to be an important mechanism in the observed eastward transport of northward momentum and heat along the shelf edge. They also appear to play a key role in the transfer of eddy kinetic and potential energy back to the mean flow, which suggests an upstream formation region and shear‐induced dissipation. Upwelling velocities of about 10−2 cm s−1 in the cold core provide the major source of new nutrients to the outer shelf. Subtidal flow variability at the 40‐m isobath was a mixed response to Gulf Stream and wind forcing. Barotropic along‐shelf current oscillations were coherent with the local winds and coastal sea level at periods of 3–4 and 10–12 days over along‐shelf scales of 400 km with small phase lags, suggesting a nearly simultaneous frictional equilibrium response to coherent wind‐induced sea level slopes.
Water and acid soluble trace metals in atmospheric particles
Authors: Lindberg S. E. , Harriss R. C.
Published: February 2008

Continental aerosols were collected above a deciduous forest in eastern Tennessee and subjected to selective extractions to determine the water soluble and acid leachable concentrations of Cd, Mn, Pb, and Zn. The combined contribution of these metals to the total aerosol mass is 0.5%, ∼70% of which is attributable to Pb alone. A substantial fraction ( ∼ 50% or greater) of the acid leachable metals are soluble in distilled water. This water soluble fraction generally increased with decreasing particle size and with increasing frequency of atmospheric water vapor saturation during a sampling period. The pattern of relative solubilities (Zn > Mn ≃ Cd > Pb) is similar to the general order of the thermodynamic solubilities of the most probable salts of these elements in continental aerosols with mixed fossil fuel and soil sources.
Influence of the Mediterranean Outflow on the isotopic composition of neodymium in waters of the North Atlantic
Authors: Piepgras D. J. , Wasserburg G. J.
Published: February 2008

The isotopic composition of neodymium in the water column of the eastern North Atlantic near the Strait of Gibraltar has been determined for several depths. The data show that the Mediterranean outflow results in a significant shift in εNd(0) toward more radiogenic values of 143Nd/144Nd in the water column at a 1000‐m depth. This corresponds to a depth in the neighborhood of the salinity maximum associated with the Mediterranean outflow. The core of the Mediterranean outflow gives εNd(0) = −9.8, as compared to εNd(0) ≈ −12 in overlying and underlying waters, demonstrating that the Mediterranean waters are distinct from the Atlantic. From mixing considerations we estimate that pure Mediterranean waters have εNd(0) ≈ −6. Possible sources of this relatively radiogenic Nd could be from drainage of young continental terranes or the injection of remobilized Nd from deep‐sea sediments that have a young radiogenic volcanic component. New data from a depth profile in the western Atlantic is presented. Comparison of Nd data for the eastern North Atlantic with that for the western North Atlantic shows fundamental differences in the water column structures for εNd(0). While both regions show a pronounced maximum in εNd(0), the western basin maximum occurs at the near surface rather than at 1000 m. In addition, deep waters of the eastern basin are found to be more radiogenic than the western basin. These differences indicate several sources of isotopically distinct Nd in the North Atlantic. The deep waters of the North Atlantic (>1000 m) have the lowest values of εNd(0) measured in the oceans. We believe that the source of these low εNd(0) values, which we associate with North Atlantic deep water, is either from freshwater drainage off the Precambrian shields of North America and Asia into the Arctic Ocean or from the injection of ‘older,’ continentally derived REE from deep‐sea sediments. Sm and Nd concentrations are found to increase with depth and εNd(0) changes with depth, indicating both vertical and lateral transport processes from different sources. This suggests a surface source of Nd and injection of REE into the water column from deep‐sea sediments or large‐scale bottom currents with high REE concentrations.
Some meteorological applications of radioactive fallout measurements in Antarctic snows
Authors: Pourchet M. , Pinglot F. , Lorius C.
Published: February 2008

Radioactive fallout measurements, generally performed to determine average snow accumulation rates, can also be used to determine other meteorological information. The following results were obtained from measurements on the Antarctic ice sheet: (1) A strasospheric residence time of 1.5 years for radioisotopes such as 90Sr and 137Cs. (2) A value of approximatively 1 of the ratio ϕ between the concentration measured, in the air (g/m3 STP) and the concentration determined in the snow (g/g), with extreme values of 0.5 and 5. (3) The dry fallout represents between 15 and 25% of the total deposition in the coastal regions and as much as 40 to 60% in the central zones. (4) A precipitation increase of 30% occured after 1965 when compared with the decade 1955–1965.
The solar absolute spectral irradiance at 1216 Å and 1800–3173 Å: January 12, 1983
Authors: Mount George H. , Rottman Gary J.
Published: February 2008

The full‐disk solar spectral irradiance in the spectral range 1800–3173 Å and at Ly α was obtained from a rocket observation above White Sands Missile Range, New Mexico, on January 12, 1983. Comparison with measurements made in May 1983 show no changes within the absolute errors of the experiment. The absolute calibration of the instruments for this flight was accomplished at the National Bureau of Standards Synchrotron Radiation Facility.
13C/12C records in northern hemispheric trees during the past 500 years—Anthropogenic impact and climatic superpositions
Authors: Freyer H. D. , Belacy N.
Published: February 2008

13C/12C data for the past 500 years are reported on two sets of European oak forest trees from the German Spessart and on free‐standing Scots pine trees from Muddus National Park, Sweden. While the forest trees show large nonsystematic variations in the 13C/12C ratio over the 500 years, the free‐standing trees show smaller fluctuations, which can be correlated to climatic changes. Since industrialization of these areas in 1850 A.D., the 13C/12C record for the free‐standing trees has been dominated by a systematic decrease of about 2‰, which is comparable with other mean 13C/12C tree ring data. The calculated Northern Hemisphere 13C/12C record derived from a total of about 50 trees reflects the recent 13C/12C change in atmospheric CO2 observed from 1956 to 1980 A.D.
On the variability of atmospheric carbon dioxide concentration at Barrow, Alaska during winter
Authors: Halter Bradley , Harris Joyce M.
Published: February 2008

Winter variability over periods of 1 to 5 days in surface CO2 concentration at Barrow, Alaska was studied by examining the relation between CO2 concentration and air mass. The largest positive anomalies of CO2 concentration occurred with relatively deep surface‐based Arctic air masses. The long residence time in the Arctic of these air masses is qualitatively compatible with both a natural CO2 source, such as the Arctic Ocean, and transport of anthropogenic CO2 from mid‐latitudes in a manner similar to that proposed for the Arctic haze. Trajectories suggest that the anthropogenic CO2 source region of eastern Asia does not contribute significantly to the positive anomalies. The largest negative CO2 anomalies were associated with the influx of air from the North Pacific or North Atlantic regions above a shallow surface‐based Arctic layer. The moisture sounding data suggest mixing or diffusion of this air aloft to the surface through the inversion layer.