bluuebunny/crossref_metadata_2025 huggingface dataset:
Upper ocean internal waves in the marginal ice zone of the northeastern Greenland Sea
Authors: Eckert Eric G. , Foster Theodore D.
Published: February 2008

Oceanographic measurements obtained in the northeastern Greenland Sea—Fram Strait region were studied in order to characterize internal wave activity in the marginal ice zone (MIZ) of the Arctic Ocean. Experiments were performed with an array of four horizontally separated current meters and a CTD instrument in 1984 as part of the Marginal Ice Zone Experiment. Spectra of horizontal and vertical motion show that within the frequency range from the inertial frequency to 3 cph the MIZ internal wave field is similar in spectral shape and energy content to the wave field found beneath Arctic pack ice. Above 3 cph the MIZ spectra contain more energy than expected based upon both beneath‐ice measurements and the Garrett‐Munk model spectra. Elevated energy levels at high frequencies are shown to be caused by intermittent increases in internal wave activity occurring on time scales from 2 to 12 hours. Phase differences between pairs of time series, computed during the passage of several packets of internal waves, are used to estimate horizontal wave number vectors. A comparison of the calculated wave number vectors to a dispersion relation derived from a simple normal mode model of internal waves suggests that the wave packets may be adequately described as being comprised of lowest‐mode, horizontally propagating internal waves. The interaction of ice‐bottom topography with a sharp, elevated pycnocline is explored as a possible source of the intermittent increases in wave activity. Spectra of vertical displacement and velocity computed from time series of both temperature and density are presented in order to show the influence of intrusive activity in the MIZ. Differences in both spectral shape and energy content, found at frequencies below 2.5 cph, emphasize the need for careful interpretation of temperature‐based measurements of vertical motion obtained over long periods of time in the MIZ.
Field measurements of the suspended sand concentration profiles and fluxes and of the resuspension coefficient γ0 over a rippled bed
Authors: Vincent Christopher E. , Green Malcolm O.
Published: February 2008

Measurements of the acoustic backscatter from suspended sand over a rippled bed and of currents were made near the crest of a ridge‐and‐runnel beach on the macrotidal North Norfolk coast of the United Kingdom. Two 12‐min records were taken close to high water in a depth of 1.7±0.2 m. Visual inspection of the data shows that sand was intermittently suspended to heights of 20–30 cm but that these events were not always correlated with strong wave‐induced currents: the structure of some of the suspension events suggest that they are due to vortex shedding from a rippled bed. The observed time‐averaged concentration profiles were compared with predictions generated using Glenn and Grant's (1987) combined‐flow model. The nondimensionalised concentrations showed good correspondence in the first 8 to 10 cm above the wave boundary layer, supporting the use of a value of 0.74, drawn from atmospheric data, for the constant of proportionality between sediment and momentum diffusivity. Above this height, observed values of the proportionality constant tended to approach 1.0, which may have been due to a decrease in sediment settling velocity with height (which is consistent with finer sand being suspended higher in the flow), or alternatively to nonuniform turbulence in the vicinity of the wave ripples. Absolute concentrations measured 2 cm above the bed were consistent with values of O(10−4) for the empirical constant γ0 in Smith and McLean's (1977) pickup function. Concentrations within the wave boundary layer were observed to decrease much more rapidly than predicted by the model. Sand transport fluxes were computed for both the cross‐shore and alongshore components of the flow using a current profile based on the combined‐flow model of Glenn and Grant (1987). For the two records, vertically integrated fluxes of 1.5‐mg/s/cm width and 0.89‐mg/s/cm width directed towards the shore were calculated for the wave oscillatory component of the transport; the mean flow produced shoreward vertically integrated fluxes of 5.1‐ and 10.5‐mg/s/cm width. The uncertainty associated with these estimates is considerable (±50%). The vertical profile of the total flux (wave oscillatory and mean) for both records showed a strong shoreward transport close to the bed, an offshore transport between 5 and 15 cm above the bed, and a further weak onshore flux above this, demonstrating the necessity for measurements of the whole concentration profile (rather than a few point samples) for the calculation of sand transport over a rippled bed in a wave‐dominated environment.
The branching of the Gulf Stream southeast of the Grand Banks
Authors: Krauss W. , KäSe R. H. , Hinrichsen H.‐H.
Published: February 2008

During March–April 1987, 101 hydrographic stations were occupied on three sections spanning a triangle between the Azores (Faial), the southern tip of the Grand Banks of Newfoundland, and Bermuda. Information on the near‐surface processes in the interior of the triangle were obtained from 32 satellite‐tracked buoys deployed during the cruise and a composite infrared image based on cloud‐free NOAA 9 data during April 1987. The data were combined to analyze the eddy field and the branching of the Gulf Stream into the North Atlantic Current and the Azores Current. Calculations of mass transports through the legs of the triangle gave a total of 46 Sv supplied by the Gulf Stream, 31 Sv of which left the area as the North Atlantic Current and westwind drift north of the Azores. The remaining 14 Sv continued towards east‐southeast as the Azores Current and southern recirculation. Additional conductivity‐temperature‐depth stations from a cruise in April 1986 into the same area allowed also study of the large‐scale circulation within that triangle in deeper layers. The Azores Current appears as a baroclinic stream which reaches down to approximately 1000 m. Intensive mixing was observed at the continental slope of Newfoundland between water of the Labrador Current and the Gulf Stream (mixed water). Owing to cabbeling and consecutive convective mixing, this water penetrates down to 2000 m depth and creates horizontal density gradients to the surrounding Gulf Stream water, which intensifies the North Atlantic Current. This process is considered to be an important energy source for this current.
Growth and energetics of shear waves in the nearshore
Authors: Dodd Nicholas , Thornton Edward B.
Published: February 2008

Nearshore shear waves (also termed FIG or far infragravity waves) are investigated. Equations governing these motions, first observed by Oltman‐Shay et al. (1989) and modeled by Bowen and Holman (1989), are systematically derived using scaling arguments. The validity of these scalings is also verified, and a nondimensional parameter εT is identified as a possible measure of the intensity of the shear waves. This confirms the importance of the seaward facing longshore current shear, (or backshear), in determining the size and range of instability in the problem. The energy transfer between the mean flow (longshore current) and these oscillations is studied by deriving the energy equations. It is demonstrated that a necessary condition for the instabilities to grow is that the cross‐shore gradient of the horizontal Reynolds stress be nonzero. This suggests the possible importance of shear waves in nearshore mixing. This analysis is then applied to two simplified longshore current‐beach profiles; the first for constant depth (Bowen and Holman, 1989) and the second a more realistic sloping beach profile.
Modulation of short waves by surface currents: A numerical solution
Authors: Hwang Paul A. , Shemdin Omar H.
Published: February 2008

Modulation of short waves by surface currents subjected to wind input and breaking dissipation is investigated. The dissipation is expressed as a power law function of the action density. The solution is presented in the form of an integral equation, and the method of characteristics is applied to obtain numerical results. The numerical solution compares favorably with the relaxation theory when the surface current is weak, and it can be applied to a strong current condition, where the linear assumption used in the derivation of the relaxation theory is no longer valid. The modulation response to various wind and wave parameters, such as short‐wave wavelength, surface wind stress, long‐wave frequency and steepness, different dissipation functions, and interaction length or duration between long and short waves, are discussed.
On eddy scales in the eastern and northern North Atlantic Ocean as a function of latitude
Authors: Krauss W. , Döscher R. , Lehmann A. , Viehoff T.
Published: February 2008

Infrared satellite images and two ensembles of satellite‐tracked buoys have been used to analyze eddy scales in the central and eastern North Atlantic between 35°N and 60°N. Both data sets yield eddy scales which decrease northward from the subtropical Atlantic and can be closely related to the Rossby radius of the first baroclinic mode.
Ring evolution in general circulation models from path analysis
Authors: Kirwan A. D. , Indest A. W. , Liu Juping , Clark N.
Published: February 2008

The thesis explored here is the use of path data for comparing primitive equation models with observations. Such comparisons naturally focus on the inversion of path data for fundamental kinematic characteristics and subsequent descriptive interpretations of both models and observations. The analysis here focuses on uncertainties that may affect this interpretation. These include random position errors and numerical noise introduced by the nonlinear inversion ansatz as well as dynamical processes that introduce both low‐ and high‐frequency variability in the kinematic fields. After each of these effects is assessed, the inversion ansatz is applied to paths generated from an eddy‐resolving general circulation model of the Gulf of Mexico. Model Loop Current ring centers determined from different paths are found to be consistent and in good agreement with observations in the abyssal gulf. In addition, these centers are compared with the model surface and interface pressure anomaly centers. The simulated paths showed ejection of mass from the Loop Current ring as it interacted with the western slope. Observed and simulated ring kinematics inferred from appropriate paths are also made and compared with observations for the slope region. The paper concludes with a discussion of the potential for using simulated and observed path data for extracting flow physics and quantifying comparisons between models and observations.
The anatomy of a freezing lead
Authors: Gow Anthony J. , Meese Debra A. , Perovich Donald K. , Tucker Walter B.
Published: February 2008

Winter leads are regions of intense ice growth with resultant large fluxes of heat to the atmosphere and salt to the ocean. They constitute a major source of new ice in the Arctic basin. During the 1988 drift phase of the Coordinated Eastern Arctic Experiment we were afforded a unique opportunity to conduct a detailed, long‐term study of a freezing lead. Measurements were made from September 17 to November 18, during which time the ice grew from open water to a thickness of 0.56 m. Cores were removed from the lead ice on a routine basis and analyzed for ice temperature, salinity, density, and structure. From these measurements the derived quantities of brine volume, porosity, heat flux to the atmosphere, and salt flux to the ocean were computed. In addition to this 2‐month time series study of ice cores, the spatial variation in lead ice properties was investigated on September 30. Thin‐section studies of ice structure indicated that the upper 0.05–0.15 m of the ice sheet was granular and that the lower portion was columnar. Typically, a portion of the granular layer was snow ice. Once the transition from granular to columnar ice had occurred, granular ice did not reappear. As the ice grew thicker the c axes of the ice crystals became aligned within the horizontal plane. This alignment direction corresponded closely with the inferred direction of the current at the ice/water interface. Vertical temperature profiles in the ice were approximately linear. Salinity profiles were usually C‐shaped with bulk salinities ranging from 9 to 6‰, before stabilizing at 6‰ for ice thicker than 0.35 m. Core data were used to compute the flux of heat to the atmosphere and the flux of salt to the ocean for seven time intervals during the experiment. Heat fluxes ranged from 89 to 29 W/m2 with an average of 50 W m−2, roughly 3 times the corresponding value from multiyear ice. The flux of salt from the lead ice to the ocean varied from 0.51 to 0.06 kg m−2 d−1, averaging 0.21 kg m−2 d−1.
Solar heating of a stratified ocean in the presence of a static ice cover
Authors: Perovich Donald K. , Maykut Gary A.
Published: February 2008

Conductivity, temperature, and depth measurements were carried out in an isolated transverse lead in static, shorefast ice in Mould Bay, Prince Patrick Island, Northwest Territories, during a 3‐week period at the height of the melt season. Currents beneath the ice appeared to be weak and largely tidal in nature. Initially, the water was vertically uniform and at the salinity‐determined freezing point down to a depth of at least 20 m. By the end of the experiment the water column consisted of three distinct layers: a well‐mixed, nearly fresh surface meltwater layer; a very stable half‐meter‐thick halocline centered somewhat below the bottom of the ice; and a thermally stratified layer of constant salinity extending down to at least 25 m. The halocline was characterized by a temperature maximum that was about 2°C warmer than the surrounding water. This temperature maximum in the pycnocline effectively trapped shortwave energy absorbed in the lower layer and prevented it from melting the overlying ice. Theoretical calculations demonstrate that the thermal structure observed beneath the pycnocline was controlled by the input of shortwave radiation and that vertical heat transport was largely the result of diffusive processes. The presence of leads drastically increases the amount of energy stored in the water. In regions where leads are common, it is likely that this energy will significantly accelerate the decay and removal of the ice once it becomes mobile and once the pycnocline is erased.
On the generation of nonlinear internal Kelvin waves in a rotating channel
Authors: Melville W. K. , Renouard D. P. , Zhang X.
Published: February 2008

Recent observations have shown that islands and constrictions may be the sites of significant internal wave activity in sea straits. In this paper we examine one generation mechanism: resonant forcing by transcritical flow past topography. Experiments were conducted on the large rotating platform at the Coriolis Laboratory, Institut de Mécanique de Grenoble, Grenoble, France. A slender body was towed through a two‐layer stratified rotating channel, simulating the flow past an island or constriction in a strait. For a range of Froude numbers, blockage coefficients, and rotation rates, nonlinear internal Kelvin waves were generated upstream. The dependence of the wave parameters on the Froude number, Rossby number, and blockage coefficient was measured. The transition between subcritical and supercritical flow is found to occur at Froude numbers greater than unity, to depend on the blockage, but to be essentially independent of the internal Rossby radius of deformation. The results are compared with recent similar measurements of single‐layer flows in nonrotating channels, and good agreement is obtained. The nonlinear Kelvin waves which are generated upstream are found to be similar in all respects to those described by Renouard et al. (1987).
Oxygen and nitrate new production and remineralization in the North Atlantic subtropical gyre
Authors: Sarmiento Jorge L. , Thiele Gerhard , Key Robert M. , Moore Willard S.
Published: February 2008

New estimates are obtained of oxygen utilization rates on isopycnal surfaces in the North Atlantic subtropical gyre thermocline based on tritium inventories (2.4–3.5 mol m−2 yr−1) and 228Ra measurements (8.5±0.8 mol m−2 yr−1). Arguments are given for why the tritium inventory oxygen utilization rate estimate may be too low. The 228Ra results are combined with recent estimates of oxygen utilization within the thermocline (Jenkins, 1987) as well as estimates of oxygen production in the mixed layer (Spitzer and Jenkins, 1989; Musgrave et al., 1988), to suggest a tentative overall oxygen balance for the whole water column. The new production of oxygen in the surface ocean (∼ 4.6±1.6 mol m−2 yr−1) appears to be lower than the estimated utilization within the thermocline (∼ 8.5±0.8 mol m−2 yr−1), suggesting that there may be a net lateral import of organic matter into the thermocline equivalent to a new production of ∼ 3.9±1.8 mol m−2 yr−1. The nitrogen balance is consistent with these results. An estimate for the total nitrogen remineralization rate in the thermocline is obtained from the oxygen utilization rate by using an −O2∶N Redfield ratio of 9.1±0.4 for remineralization (Minster and Boulahdid, 1987), giving a nitrogen remineralization rate of ∼ 0.93±0.10 mol m−2 yr−1. Subtracting off the estimated lateral export of nitrate of ∼ 0.51± 0.21 mol m−2 yr−1, which is presumed to be balanced by a lateral import of dissolved organic nitrogen (Rintoul and Wunsch, 1990), gives a nitrate flux into the surface of ∼ 0.42±0.23 mol m−2 yr−1, which is comparable to the estimate of 0.6±0.2 mol m−2 yr−1 obtained by Jenkins (1988) near Bermuda as well as the 100‐m particulate nitrogen flux of 0.33 mol m−2 yr−1 obtained Altabet (1989) near Bermuda.
Stability of free surface sediment flow
Authors: Hjorth P. G.
Published: February 2008

Observations of unusual surface level oscillations on the sediment‐laden Yellow River of China, have led to the suggestion that the oscillations arise from a free surface instability peculiar to fluids having the constitutive relation of a Bingham plastic (i.e., possessing a finite yield stress). A model has been proposed in which free surface flows of Bingham plastics appear unstable at conditions for which the corresponding flow of clear water would be stable. We argue here that gravity driven Bingham plastics are, in fact, stable to free surface oscillations and that consequently the Yellow River oscillations most likely do not stem from a simple surface instability.
Evolution of a gravity wave spectrum through a current gradient
Authors: Trulsen Gerd N. , Dysthe Kristian B. , Trulsen Jan
Published: February 2008

Transformation of a wind wave spectrum through a region of nonuniform current is investigated. It is shown how an evolution equation for the spectral action can be arrived at by the scaling arguments introduced by Phillips (1985). A numerical model based on this equation is applied to two different current systems (a head‐on current and a shear current). The model also contains an indicator of excess wave breaking activity. It is pointed out that the short wave part of the spectrum (less than 10 cm, say) is not expected to be well predicted by models like the one presented here. This is probably because excess wave breaking of the longer waves is expected to generate short waves or short‐scale surface roughness, an effect not accounted for in these models.
Climate sensitivity, energy balance models, and oscillatory climate models
Authors: Ghil M.
Published: February 2008

Three general questions of climate theory are addressed. First, it is shown that climate sensitivity cannot be determined directly from available data, and hence its computation depends on model assumptions. Second, the relationship between energy‐balance models (EBMs), oscillatory climate models, and ice‐sheet models (ISMs) is discussed, and it is shown how EBMs can be obtained as a singular limit of certain oscillatory models. Finally, the physical and mathematical aspects of the oscillations are discussed in further detail and related to the stability question for EBMs and for ISMs.
Groundlevel OH radical concentration: New measurements by optical absorption
Authors: Hübler G. , Perner D. , Platt U. , Tönnissen A. , Ehhalt D. H.
Published: February 2008

Tropospheric OH radical concentrations were observed at two locations in Germany by long‐path UV absorption spectroscopy. During the summer months, noontime concentrations at sunny days averaged to 1.6×106 OH cm−3. The highest concentrations observed so far did not exceed 2.5×106 OH cm−3.The highest concentrations observed so far did not exceed 2.5×106 OH cm−3. A number of possible spectral interferences by atmospheric trace gases (SO2, CH2O, CS2) were identified, and OH concentrations, as derived after correction for those interferences (if necessary) are reported for 1979 through 1981.
Radiative heating rates near the stratospheric fountain
Authors: Doherty G. Mark , Newell Reginald E. , Danielsen Edwin F.
Published: February 2008

Radiative heating rates are computed for various sets of conditions thought to be appropriate to the stratospheric fountain region: with and without a layer of cirrus cloud between 100 and 150 mbar; with standard ozone and with decreased ozone in the lower stratosphere, again with and without the cirrus cloud; and with different temperatures in the tropopause region. The presence of the cloud decreases the radiative cooling below the cloud in the upper troposphere and increases the cooling above it in the lower stratosphere. The cloud is heated at the base and cooled at the top and thus radiatively destablized; overall it gains energy by radiation. Decreasing ozone above the cloud also tends to cool the lower stratosphere. The net effect is a tendency for vertical convergence and horizontal divergence in the cloud region. High resolution profiles of temperature, ozone, and cloudiness within the fountain region are required in order to assess the final balance of the various processes.
Reduction of thunderstorm electric field intensity produced by corona from a nearby object
Authors: Vonnegut B.
Published: February 2008

Measurements with an electric field mill beneath a thundercloud show that space charge produced by corona from a surrounding, horizontal, fine‐wire antenna that is connected to the earth greatly reduces the electric field intensity.
Bayesian probability calculations for stratospheric ozone modifications
Authors: Bishop Lane , Hill William J.
Published: February 2008

A methodology is described for combining current information on ozone perturbations estimated from chemical model calculations and ozone trend analyses. This approach, known as Bayes analysis, yields probabilities for different amounts of change in total column ozone and ozone in Umkehr layer 8 (near 40 km). An examination is made of the sensitivity of the results to two different chemical models, and uncertainties involved in chemical model and trend analysis estimates.
The NIMBUS 7 CZCS Experiment in the Benguela Current Region off southern Africa, February 1980: 2. Interpretation of imagery and oceanographic implications
Authors: Shannon L. V. , Schlittenhardt P. , Mostert S. A.
Published: February 2008

Three NIMBUS 7 CZCS chlorophyll images of the southern Benguela Current region off the west coast of South Africa on February 9, 13, and 15, 1980, during a surface truth experiment in the area are evaluated in the light of a time series of airborne radiation thermometry and wind data for this period, and the validity of CZCS chlorophyll estimates for the region is discussed. There was good agreement between upwelling and relaxation in the system and changes in the distribution of chlorophyll. The development of upwelling tongues with the subsequent increase in chlorophyll concentrations and the intensification of the oceanic front off capes was evident. An S‐shaped band of high chlorophyll was present well offshore of the Orange River mouth and lends support to the existence of a divergence zone at the shelf break in the area, there being fair agreement between satellite buoy tracks, topography, and the position of the oceanic color front. Areas of elevated chlorophyll were evident in two bays on the south coast on February 13, 1980, and these are ascribed to an earlier upwelling event in the region. Implications for future work in the area are discussed.
Stratospheric water vapor, nitrogen dioxide, nitric acid and ozone measurements deduced from spectroscopic observations
Authors: Girard André , Louisnard Nicole
Published: February 2008

Solar infrared absorption spectra concerning H2O, NO2, HNO3, and O3 have been recorded during the LIMS (Limb Infrared Monitor of the Stratosphere) lifetime: (1) Mixing ratio profiles are deduced from a balloon experiment at 40 km on April 24, 1979, at 31°N. (2) Latitudinal variations of the column densities are deduced from an aircraft, near 11.5 km, during a set of seven flights in October–November 1978 over a wide range of latitude. For H2O the vertical profile deduced from balloon observations exhibits an increasing mixing ratio from (3.5±0.5) ppm at 23 km to (6.5±1.5) ppm to 40 km. The strong latitudinal variation in the total column of HNO3 is clearly observed in the aircraft results, while the balloon profile at 31°N exhibits a maximum value (9±2) ppbv located near 22 km. The NO2 vertical column density is maximum at high latitude in the spring hemisphere. The NO2 mixing ratio profile observed at sunset is maximum around 33 km (8±1) ppbv.
Vertical distribution of aerosol strong acid and sulfate in the atmosphere
Authors: Tanner Roger L. , Kumar Romesh , Johnson Stanley
Published: February 2008

Vertical profiles are reported for sulfate, for strong acid‐to‐sulfate molar ratios, and for related species. Data were obtained in the northeastern United States by airborne filter‐pack sampling at multiple altitudes with some concurrent ground measurements and by impactor measurements on the ground and aloft, using semiquantitative FTIR spectroscopic analyses. Filter‐pack and impactor approaches were compared during one experimental period. Vertical profile data demonstrate that acid‐to‐sulfate ratios in ambient aerosols usually increase with altitude (Z) in the lower troposphere, occasionally remain constant with Z, and almost never decrease with Z. The sum of nitrate and nitric acid decreases with Z, but the fraction as nitric acid increases with Z, consistent with the aerosol acidity data. Urban effects on the acid‐to‐sulfate ratios in aerosols are demonstrated. The results strongly suggest that reequilibration of the aerosol nitric acid‐ammonia system must be occurring rapidly and that strong acids (in aerosols and gases) may be available for long‐distance transport in the lower troposphere.
Chemical composition of radiation fog water at Albany, New York, and its relationship to fog microphysics
Authors: Fuzzi Sandro , Castillo Raymond A. , Jiusto James E. , Lala G. Garland
Published: February 2008

Radiation fog water samples collected at the Albany (NY) County airport show quite low acid content compared with previously published data on fog acidity: the pH ranges from 4.3 to 6.4. This fog water ionic concentration is indicative of low pollution in this area. The leading mechanism responsible for the variability in aqueous concentration of nonvolatile ionic constituents of these fogs is the growth and evaporation of droplets, as reflected by the variation of LWC during the fog evolution. For these reasons the origin and composition of aerosol on which fog droplet condensation takes place is of major importance. Droplet size spectra analysis show that there is a need for improving the collection methods of fog water in order to better describe the chemistry involved, especially to maximize the drop capture efficiency of the collectors and reduce the sampling time for better resolution.
Baroclinic generation of planetary transient and stationary waves from forced stationary waves
Authors: Neelin J. David , Lin Charles A.
Published: February 2008

The linear instability of forced stationary waves in a baroclinic zonal flow is examined with a two‐level quasi‐geostrophic beta plane model. Realistic zonal topography and diabatic forcings produce a steady state solution of planetary‐scale stationary waves. Baroclinic instability of the forced waves gives rise to transient perturbation modes of planetary zonal scale and a preferred meridional scale of about twice the radius of deformation. One of the dominant planetary modes is stationary and resembles the observed stationary wave pattern. In the steady state model this form can be obtained only for certain values of the meridional scale of the forcings. It is suggested that this stationary mode could contribute to the time average stationary wave distribution. Applications to blocking are also considered. Interference of stationary and quasi‐stationary modes can apparently produce regional as well as global blocking patterns.
Solar ultraviolet variation between 1977 and 1983
Authors: Hall L. A. , Anderson G. P.
Published: February 2008

A fifth measurement of the solar ultraviolet irradiance at 40 km in the stratosphere has been added to four earlier ones. It confirms the previously published conclusion that photospheric solar irradiance in the range 2350–2870 Å has been essentially constant during the current solar activity cycle. Chromospheric emissions seen in the Mg II line cores increased during rising activity and decreased again as the activity declined.
Some aspects of the interannual variation of mean monthly sea level pressure on the Southern Hemisphere
Authors: Mo Kingtse C. , Van Loon Harry
Published: February 2008

We calculate the seasonal changes that are largely associated with the half‐yearly wave, auto‐correlation functions, and the mean planetary waves in the monthly mean sea level pressure from two data sources. One covers the period from 1951 to 1958 (from the South African Weather Bureau) and the other the period from 1972 to 1980 (from the Australian Bureau of Meteorology). Thirty years of data from stations over the southern hemisphere are used to assess the reliability of the differences between the two periods that the grid‐point data show. These differences are especially large over the Atlantic Ocean and the Pacific Ocean. The station data confirm the changes between the two periods and thus the observed differences in the mean waves, which are especially large for wave number 3.
NOxmeasurements in clean continental air and analysis of the contributing meteorology
Authors: Bollinger M. J. , Hahn C. J. , Parrish D. D. , Murphy P. C. , Albritton D. L. , Fehsenfeld F. C.
Published: February 2008

Measurements have been made of NOx(NO+NO2) at a site located in the Colorado mountains. These measurements revealed periods of exceptionally low NOxmixing ratios. During these episodes, the NOxmixing ratio dropped below 20 parts per trillion by volume for extended periods. These episodes are characterized by synoptic meteorological conditions in which air transported to this site is isolated from contamination by ground‐level sources of NOx.
Unusual structures of high‐latitude stratospheric electric fields
Authors: D'Angelo N. , Iversen I. B. , Madsen M. M.
Published: February 2008

A possible explanation is discussed of three unusual stratospheric electric field structures reported by Madsen et al. (1983). It is proposed that stratospheric vertical electric current structures may arise as extensions into the stratosphere of tropospheric currents generated by convective charge transport.
Small‐particle dry deposition on natural waters: Modeling uncertainty
Authors: Sievering Herman
Published: February 2008

Several recent articles have used modeling results to calculate sea salt or sulfur exchange between the atmosphere and oceans. In all cases, modeling uncertainty for small‐particle dry deposition is grossly underestimated. This short note discusses the magnitude of uncertainty that presently pervades these modeling results. The conclusion, based on a review of models and the limited experimental data available, is that the uncertainty in small‐particle (diameter D<1 μm) dry deposition to water surfaces is about two orders of magnitude. It is suggested that future calculations of small‐particle atmosphereocean exchange account for this ±1 order of magnitude uncertainty and that direct open‐ocean measurements are needed before any reduced uncertainty may be expected.
A comparison of U.S. and USSR rocketsondes using LIMS satellite temperature sounding as a transfer standard
Authors: Gille John C. , Bailey Paul L. , Beck Sharon A.
Published: February 2008

Temperature soundings from rocketsondes used by the USSR have been compared to temperature retrievals obtained in low, middle, and high latitudes by the LIMS instrument on Nimbus 7. The rocket and satellite temperatures agree at low altitudes, but the rocket temperatures are about 10 K cooler near the stratopause. There is a tendency for the agreement to become better in the mesosphere, but there appear to be significant differences between day and night comparisons. A day‐night correction curve is derived, and the USSR comparisons are converted to day conditions. A comparison between LIMS and U.S. rocketsondes in the same latitude bands shows generally good agreement up to the stratopause, but above that the U.S. rocket temperatures are warmer. Then, using the LIMS as a transfer standard, rocketsondes from the United States and the Soviet Union are intercompared. The differences are similar in all three latitude bands but larger than those found in the previous (1977) intercomparison. The differences determined in this study should be more representative, since they represent a variety of locations and seasons as well as standard operational procedures.
Rates of Dry Deposition Determined Using Wet/Dry Collectors
Authors: Feely H. W. , Bogen D. C. , Nagourney S. J. , Torquato C. C.
Published: February 2008

Daily samples of dryfall were collected during the June 1982 Dry Deposition Measurement Intercomparison Study at Champaign, Illinois, using six Aerochem Metrics wet/dry collectors. Upon completion of the field experiment, these samples were analyzed at the Environmental Measurements Laboratory for pH and for their concentrations of major inorganic constituents. Contamination by rain and bird droppings rendered a number of dryfall samples unusuable. When data for these samples were removed, the remaining data displayed acceptable precision for sulfate, calcium, and magnesium. The measured deposition rates varied between 7 and 73 ng/m2/s for sulfate, between 7 and 44 for calcium, and between 0.8 and 8.1 for magnesium. The precision of the data for ammonium, nitrate, and phosphate was poor, so we have not calculated deposition rates for these constituents. The measurements of the atmospheric concentrations of sulfate reported by the Illinois State Water Survey have been used to calculate deposition velocities for particulate sulfate for 18 daily samples, even though the aerosol sampler and the dry bucket of the wet/dry collector may not sample the same size population of particulates. These velocities ranged from 0.1 to 1.2 cm/s, with a median value of 0.4 cm/s and a mean of 0.45±0.31 cm/s.
Transient climate response to external forcing on 100–104 year time scales: 2. Sensitivity experiments with a seasonal, hemispherically averaged, coupled atmosphere, land, and ocean energy balance model
Authors: Harvey L. D. Danny , Schneider Stephen H.
Published: February 2008

We present a hemispherically averaged, seasonal model with land‐sea and surface‐air resolution that we use to compare the transient temperature response of different model components to changes in the radiative forcing. Horizontal heat transport coefficients were obtained by tuning the model to reproduce the present seasonal climate as closely as possible. Cross‐sensitivity experiments with a step function solar constant increase and a variety of ocean parameter feedback processes essentially duplicate the results obtained in part 1 (Harvey and Schneider, 1985) with a globally averaged model. We intercompare the global and hemispheric model surface and deep‐ocean transient response and show how both the global mean surface and mixed‐layer only transient response of the hemispheric model can be reproduced by using the globally averaged model. For a time‐dependent CO2 increase scenario we find that the mixed‐layer warming lags moderately behind the atmosphere wanning but that the atmosphere over land and atmosphere over sea warmings are rather tightly coupled. Implementation of a number of ocean parameter feedbacks to a time‐dependent CO2 increase has a similar qualitative effect on the transient temperature response as when implemented for a step function solar constant increase but causes less variation in the transient response than uncertainties about the equilibrium climate sensitivity. During the first year following a small negative perturbation to the solar constant, in order to mimic a volcanic dust veil, we find that the air temperature response over land is about twice that of the ocean mixed‐layer temperature. This suggests that one should distinguish between temperature responses over land and over ocean in any studies attempting to compare model‐generated volcanic signals with empirical surface temperature data. For complex short‐ and long‐term mixed forcing changes, such as volcanic and CO2, the lag between atmosphere and mixed‐layer temperature changes does not become large until the long‐term forcing change becomes dominant, although the land‐sea lags associated with short‐term perturbations may still be significant for regional climatic anomalies associated with these perturbations.
On the correspondence between Standard Umkehr, Short Umkehr, and solar backscattered ultraviolet vertical ozone profiles
Authors: DeLuisi John J. , Mateer Carlton L. , Bhartia P. K.
Published: February 2008

A series of concurrent surface‐based Standard Umkehr, Short Umkehr, and satellite solar backscattered ultraviolet observations of vertical ozone profile over Boulder, Colorado, is used to evaluate their mutual performance as a co‐observing system. An understanding of the evaluation results is facilitated with use of theoretically predicted performance characteristics derived in a previous study of the Umkehr methods. Patterns of observed ozone profile bias, variance, and correlation were found to agree reasonably well with theoretically predicted patterns; however, there are some exceptional departures in the lowest and uppermost levels of the profiles. These departures are thought to be due mainly to measurement inversion algorithm inadequacies, namely, the omission of temperature‐dependent ozone absorption information. Other possible causes are also mentioned.
The origin of the 100,000 year cycle in a simple ice age model
Authors: Snieder Roelof K.
Published: February 2008

A one‐dimensional nonlinear ice age model developed by J. Imbrie and J. Z. Imbrie was used to investigate the 100,000 year cycle in climate records. It was already known that the model could mimic the 100,000 year cycle in the climate response, but it was not clear how this strong response was created. It is shown in this paper that the interference between the spectral components in the solar heating of 19,000 years and 23,000 years gives rise to an amplitude modulation, and how this modulation is converted by the nonlinearity to a 100,000 year cycle in the climate response.
The reservoir of ozone in the boundary layer of the eastern United States and its potential impact on the global tropospheric ozone budget
Authors: Vukovich Fred M. , Fishman Jack , Browell Edward V.
Published: February 2008

An analysis of available ozone data in the eastern two‐thirds of the United States indicates that a substantial reservoir of ozone is present in the summertime. Five‐year mean concentrations range from 40 to 65 ppbv. The reservoir covered an area of several million square kilometers and extends vertically from the surface to 1 to 2 km. The vertical distribution of ozone in the reservoir during midday supports a transport of additional ozone from the boundary layer to the free troposphere. Data are presented demonstrating the potential effect of transport by convective clouds and by the sea breeze circulation—mechanisms by which ozone may be transported out of the boundary layer into the free troposphere. The potential impact of this reservoir on the tropospheric ozone budget is discussed. It is shown that if less than half of the ozone mass in this reservoir is transported to the free troposphere, then the amount of ozone transported out of the boundary layer approximates the amount of ozone transported down‐ward during a tropopause fold event.
Scavenging ratios, wet deposition, and in‐cloud oxidation: An application to the oxides of sulphur and nitrogen
Authors: Barrie L. A.
Published: February 2008

With special regard to the class of substances in precipitation that potentially originate from both gaseous and particulate precursors, the process of precipitation scavenging is discussed. A model relating daily average ground level scavenging ratios (W) to nucleation scavenging and in‐cloud chemical transformation is introduced and is used as guidance in the regression analysis of 3 years of SO4= and NO3− scavenging‐ratio observations made at six locations in eastern Canada. It was found that W of SO4=‐, NO3−‐, and SO4=‐bearing particles is inversely proportional to the one‐third power of the precipitation amount in the event. The best regression model explained 41% of the variance in log W for SO4=. It included the effects of location, precipitation amount, precipitation type, and in‐cloud SO2 oxidation. The last effect accounted for 50% of the variance explained. The analysis predicts that, on average, in‐cloud SO2 oxidation accounts for 42–79% of the SO4= observed in rain and with the exception of one site, less than 20% of the SO4= observed in snow. These results are consistent with a mechanism of SO2 oxidation involving photochemically produced H2O2. A similar analysis for NO3− supports the hypothesis that throughout the year much of the NO3− in precipitation originates from in‐cloud NO2 oxidation. It suggests that, depending on location, oxidation of 0.5–1.2 ppbv of NO2 is sufficient to explain observations. One possible mechanism of oxidation is the reaction with O3 to form NO3 and hence soluble N2O5. These results, combined with observations in the eastern United States, indicate that in eastern North America SO2 oxidation within a rain storm becomes an increasingly important source of rain SO4= as latitude increases. Scavenging ratios are useful tools for investigating in‐cloud conversion and for parameterizing precipitation removal. However, they are limited to describing the average characteristic of an ensemble of storms. They cannot be used with confidence to analyze individual events.
An inverse problem occurring in remote sensing in the thermal infrared bands and its solutions
Authors: Raffy Marcel , Becker François
Published: February 2008

Several methods are proposed in order to obtain agrometeorological and geological parameters, such as thermal inertia and evapotranspiration flux, over large regions of our planet from both visible and thermal infrared data obtained from satellites. These methods are based on minimization techniques which depend on a linear operator that maps the fluxes at the surface to the surface temperature. The methods can be adaptated to the various experimental situations encountered, i.e., for a given set of available input data, they lead to the corresponding set of unknown parameters. For example, they give the thermal inertia and the evapotranspiration flux without a priori knowledge of the heat transfer resistances. To take into account the error of measurements, we propose a stabilization procedure that improves the accuracy of the method.
Theory of electric conductivity measurements by an electrostatic probe in an atmospheric low‐density continuum ionized gas
Authors: Chang Jen‐Shih , Kodera Kuniko
Published: February 2008

A method has been developed and used to obtain theoretical predictions of the electric conductivity measured by an electrostatic probe in an atmospheric ionized gas, i.e., with mean free path very much less than probe radius. Three different methods for conductivity measurements have been analyzed: (1) attracting potential method; (2) transient response method; (3) space potential method.
On the presence and generation of AC and DC electric fields and small ions in closed rooms as a function of building materials, utilization, and electrical installation
Authors: Reiter R.
Published: February 2008

In the discussion on possible biological effects of natural atmospheric electric fields or electromagnetic radiation it is frequently overlooked that man, under normal living and working conditions in closed rooms, is also exposed to considerable fields of various types and strengths. Therefore an extensive “inventory” has been made of such ac and dc fields as they occur in rooms of different construction, utilization, and electrical equipment. Results are presented and discussed, also with respect to biological conditions, including some typical examples from the relevant literature.
The charging of ice by differences in contact potential
Authors: Caranti J. M. , Illingworth A. J. , Marsh S. J.
Published: February 2008

Laboratory experiments measuring the charge transferred when individual 100‐μm ice spheres impact upon various metal targets show that the charge transferred depends upon the work function of the metal. If ice is assigned a “work function” of 4.3 eV, then the contact potential difference between the ice and the metal accounts for the observed charging. It may be possible to explain the generation of charge within thunderstorms in terms of a contact potential difference between colliding vapor‐grown crystals and riming hailstones. Although many experiments measuring the charging of ice from collisions can be explained in terms of contact potentials, we report one that cannot. A layer of ice estimated to be 1 μm thick deposited from the vapor (“frost”) on the target is sufficient to cause it to charge positively, and conversely, if a similar thickness is allowed to evaporate, the target reverts to negative charging.
An objective technique for the delineation and extrapolation of thunderstorms from GOES satellite data
Authors: Cherna E. , Bellon A. , Austin G. L. , Kilambi A.
Published: February 2008

An empirical relationship between radar reflectivity levels exceeding 32 and 40 dBZ at a height of 6 km and sferics data is used to generate maps that indicate regions of thunderstorms. These radar maps serve as ground truth when compared with colocated GOES visible and infrared imagery. A threshold computed to equalize the radar and satellite thunderstorm areas delineates the region in visible‐IR space that is most probably associated with electrical activity. The locations of satellite‐delineated storms beyond radar range, on the synoptic scale, show good agreement with sources of lightning determined from sferics detectors. The skill of the extrapolation of these areas for short‐range forecasting is discussed.