bluuebunny/crossref_metadata_2025 huggingface dataset:
On the wind‐induced sea level changes on the Scotian shelf
Authors: Sandstrom H.
Published: February 2008

An analysis of coastal tide gage records and coincident weather data shows that at synoptic time scales the sea level changes are highly correlated with variations in the alongshore component of wind (better than with wind stress). Regression analysis indicates that there are systematic seasonal differences in how the sea responds to given wind stress. A study based on a simple barotropic model, which agrees with the main observed features, shows that bottom friction becomes important at synoptic time scales. Use of a quadratic friction law yields the solution in which sea level is correlated with wind. The observed phase lags also agree with those predicted by the model.
The active and passive microwave response to snow parameters: 1. Wetness
Authors: Stiles William H. , Ulaby Fawwaz T.
Published: February 2008

Diurnal observations of the variation of the radar backscattering coefficient σ° and microwave apparent radiometric temperature Tap with snow wetness mv are presented. The results show that σ° decreases and Tap increases with mv and that the magnitude of the sensitivity to mv increases with microwave frequency for both active and passive microwave parameters. Moreover, while the sensitivity of σ° to snow wetness variations increases with angle of incidence, the sensitivity of Tap to snow wetness is approximately angle of incidence independent.
Equatorial waves in the satellite‐observed cloud velocity field over the Pacific
Authors: Rothstein Lewis M. , Groves Gordon W.
Published: February 2008

A space‐time spectral analysis is applied to the 900‐mbar meridional wind component over the equatorial Pacific Ocean. Cloud drift vectors, in the form of movie loops derived manually from cloud‐tracking satellites, constitute the data base for this investigation. The major conclusions are as follows: (1) The maximum energy density levels of the wind occur at low wave numbers over a broad range of frequencies. These disturbances appear to manifest themselves as fluctuations occurring simultaneously over a large span of longitude. (2) Investigation of the high frequency‐high wave number structure is difficult because of the general shortage of reliable data and the uneven satellite sampling intervals. Selection of spectral parameters becomes a compromise between the problems of high aliasing and low reliability. A high frequency‐low wave number (time lag of 5 hours and space separation of 2.1° longitude) study was selected. (3) There was no indication of a distinct 4‐day signal in our spectra. (4) There appears to be less high‐frequency energy in the equatorial band (1.05°S to 1.05°N) than in the other two more southerly bands (5.25°S to 3.15°S and 3.15°S to 1.05°S).
Longshore pressure gradients caused by offshore wind
Authors: Csanady G. T.
Published: February 2008

Observations of currents 12 km south of the Long Island coast show that strong offshore winds could generate considerable longshore nontidal flow well below any surface Ekman drift. A momentum balance calculation in the longshore direction shows a surface level gradient of order 10−6 to be the proximate cause of the longshore flow. A very simple model of the observed phenomena is a sloping plane beach acted upon by cross‐shore wind, varying sinusoidally in the longshore direction. With bottom friction parameterized by a linear law, a parabolic equation is found to govern steady state flow, expressing a balance of vorticity tendencies due to cross‐isobath flow, curl of bottom stress, and any forcing. Calculated solutions for variable cross‐shore wind show a trapped pressure field on the inner shelf which controls the transition between an essentially frictionless momentum balance on the outer shelf to frictionally dominated flow at the shore. Realistic estimates of the parameters entering the theory suggest that the longshore gradients associated with the trapped inner shelf field are of the correct order of magnitude to explain the generation of longshore flow by a system of cross‐shore winds.
Crystal alignments in the fast ice of Arctic Alaska
Authors: Weeks W. F. , Gow A. J.
Published: February 2008

Field observations at 60 sites located in the fast or near‐fast ice along a 1200‐km stretch of the north coast of Alaska between the Bering Strait and Barter Island have shown that the great majority of the ice samples (95%) exhibit striking c axis alignments within the horizontal plane. In all cases the degree of preferred orientation increased with depth in the ice. Representative standard deviations around a mean direction in the horizontal plane are commonly less than ±10° for samples collected near the bottom of the ice. At a given site the mean c axis direction
0 may vary as much as 20° with vertical location in the ice sheet. The c axis allignments in the nearshore region generally parallel the coast, with strong alignments occurring in the lagoon systems between the barrier islands and the coast and seaward of the barrier islands. In passes between islands and in entrances such as the opening to Kotzebue Sound the alignment is parallel to the channel. Only limited observations are available farther seaward over the inner (10‐ to 50‐m isobaths) and outer (50‐m isobath to shelf break) shelf regions. These indicate NE‐SW and E‐W alignments, respectively, in the Beaufort Sea north of Prudhoe Bay. The general patterns of the alignments support the correlation between the preferred c axis direction and the current direction at the ice/water interface suggested by Weeks and Gow (1978). A comparison between c axis alignments and instantaneous current measurements made at 42 locations shows that the most frequent current direction coincides with
0. At the one site where we were able to determine the current direction (52°T) over a longer period (7 hours), the agreement with
0. (48°T) was excellent. Similarly, if only
0. values determined in the nearshore region are considered, the most frequent deviation is 10° or less between
0. and the trend of the adjacent shoreline, which is presumably parallel to the prevailing longshore currents. The c axis alignments are believed to be the result of geometric selection, with the most favored orientation being that in which the current flows normal to the (0001) plates of ice that comprise the dendritic sea ice/seawater interface. The instantaneous current observations suggest SW nearshore currents along the Chukchi coast between SW of Point Lay and SW of the Rogers‐Post Monument. In the vicinity of Barrow all currents measured along the Chukchi coast were toward the NE. Current directions along the Beaufort coast in the nearshore region were generally parallel to the coast, with 45% of the observations indicating currents toward the E and 55% currents toward the W.
Heterogeneous atmospheric reactions: 2. Atom and radical reactions with sulfuric acid
Authors: Baldwin Alan C. , Golden David M.
Published: February 2008

The collisional reaction probabilities of oxygen and nitrogen atoms and hydroxyl radicals with concentrated sulfuric acid were found to be <1.0×10−6, <1.0×10−6, and 4.9±0.5×10−4, respectively. These results indicate that heterogeneous loss is not an important process for these species in the atmosphere.
High‐frequency internal waves at ocean station P
Authors: Dillon Tom M. , Caldwell Douglas R.
Published: February 2008

Slow perturbations of the drop speed of a nearly freely falling, winged, microstructure probe in the upper 200 m at station P are interpreted as vertical velocity fluctuations of an internal wave field. The frequencies of these fluctuations lie in the 2.5‐ to 4‐cph band, near the buoyancy‐frequency cutoff. A typical rms value is 1.3 cm/s. Indications of the vertical structure of the wave field and the partition of energy among modes are obtained by statistical comparison with discrete mode solutions of the internal wave equation. It is found that the first and second modes carry most of the internal wave energy and that the partition of energy between them may change in 3 days.
Satellite observations of a nutrient upwelling off the coast of California
Authors: Traganza E. D. , Nestor D. A. , McDonald A. K.
Published: February 2008

Satellite thermal imagery is combined with automated chemical analysis of surface waters off central California to detect and better understand a ‘nutrient upwelling’ entering the California Current system. While thermal surface water features have been mapped successfully from satellites for a number of years, the relationship of satellite thermal imagery to nutrients, such as nitrates and phosphates, has not been established. As a result of such efforts, satellite remote sensors may help to explain the relationship between chemical mesoscale and pelagic ecosystems of the ocean.
Sulfate aerosol production and growth in coal‐operated power plant plumes
Authors: Dittenhoefer Allen C. , De Pena Rosa G.
Published: February 2008

The oxidation of SO2 and the resultant aerosol growth kinetics are inferred from airborne measurements of the number concentrations and size distributions of pure sulfate and mixed particles within the coal‐fired Keystone power plant plume in western Pennsylvania. Measurements of aerosol concentrations in nine distinct size ranges between 0.01–2.0 μm diameter were coupled with impactor sampling and quantitative sulfate analysis of individual particles at various plume travel times. Cross‐sectional plume mappings of the horizontal and vertical concentration profiles of SO2 and sulfate mass provided a means of calculating SO2 conversion rates. Thirteen flights encompassing a wide range of meteorological conditions and plume behavior were compared in an attempt to isolate the various gas‐to‐particle conversion mechanisms. Both gas and droplet phase reactions involving SO2 have been identified, and their importance for atmospheric sulfate formation are assessed. Total sulfate particle concentration was found to be related directly to solar radiative flux. Sulfate particles in the plume achieved maximum size at very high relative humidities during plume merger with cloud and fog layers.
Observation by HF radar of the Phillips resonance mechanism for generation of wind waves
Authors: Trizna D. B. , Bogle R. W. , Moore J. C. , Howe C. M.
Published: February 2008

Measurements are reported of directional ocean wave spectra made over 80° of viewing angle by an HF radar, operating in the surface wave mode in an area 22.5 km north of San Clemente Island, California. Ten azimuths from 280° to 360° true bearing were simultaneously measured for 10 wave frequencies ranging from 0.14 Hz (75 m waves) to 0.35 Hz (13 m waves). A Waverider buoy was used to measure omnidirectional energy in the region, and first‐order radar Bragg lines were used to determine the spreading of wave energy with angle. Data are presented in which a bimodal spectrum was present: an attenuated spectrum with wave components to 0.10 Hz from a storm at sea at 270° bearing; plus a transient local wind spectrum, stronger in amplitude at the higher frequencies, with wave cutoff near 0.14 Hz, and running from 315° bearing. Just after the onset of local winds, the westerly spectrum fitted a cosine squared spread at the lowest measured frequencies. With the development of local wind, which blew at a 12–14 kn (6–7 m s−1) speed for a period of 12 hours, the wave spectrum spread about the wind direction as cosine thirty‐second at the lowest frequencies measured, 0.14 Hz, and cosine sixty‐fourth at the highest frequencies measured, 0.35 Hz. For 0.28 Hz waves the Phillips resonance mechanism for wave generation is proposed to explain the twin peaks in amplitude observed, equally spaced either side of the wind direction. These were dominant for the earliest measurement period and still were major contributions for later measurement periods. This mechanism was found to contribute also at the higher wave frequencies, as predicted by theory. Coherence times are derived from the angular widths of the Phillips resonances based on predictions of Stewart and Manton and are found to agree quite well with theory.
Comparison of surface wind stress measurements: Airborne radar scatterometer versus sonic anemometer
Authors: Brucks John T. , Jones W. Linwood , Leming Thomas D.
Published: February 2008

Sea surface wind stress measurements recorded by a sonic anemometer are correlated with airborne scatterometer measurements of ocean roughness (cross section of radar backscatter) to establish the accuracy of remotely sensed data and assist in the definition of geophysical algorithms for the scatterometer sensor aboard Seasat A. Results of this investigation are as follows: (1) Comparison of scatterometer and sonic anemometer wind stress (u*) measurements are good for the majority of cases; however, a tendency exists for scatterometer u* to be somewhat high for higher wind conditions experienced in this experiment (6–9 m/s). (2) The scatterometer wind speed algorithm tends to overcompute the higher wind speeds by approximately 0.5 m/s. This is a direct result of the scatterometer overestimate of u*, from which wind speeds are derived. (3) Algorithmic derivations of wind speed and direction are, in most comparisons, within accuracies defined by Seasat A scatterometer sensor specifications.
Comparisons between wave directional spectra from SAR and pressure sensor arrays
Authors: Pawka S. S. , Hsiao S. V. , Shemdin O. H. , Inman D. L.
Published: February 2008

Simultaneous directional wave measurements were made at Torrey Pines Beach, California, by a synthetic aperture radar (SAR) and a linear array of pressure sensors. The measurements were conducted during the West Coast Experiment in March 1977. Quantitative comparisons of the normalized directional spectra from the two systems were made for wave periods of 6.9–17.0 s. The comparison results were variable but generally snowed good agreement of the primary mode of the normalized directional energy. An attempt was made to quantify the physical criteria for good wave imaging in the SAR. A frequency band analysis of wave parameters such as band energy, slope, and orbital velocity did not show good correlation with the directional comparisons. It is noted that absolute values of the wave height spectrum cannot be derived from the SAR images yet and, consequently, no comparisons of absolute energy levels with corresponding array measurements were intended.
The relation between atmospheric trace species variabilities and solar UV variability
Authors: Penner Joyce E. , Chang Julius S.
Published: February 2008

It has been suggested (Hudson, [1977]) that monitoring O3 levels in the upper stratosphere may provide an early warning signal for detection of changes in ozone owing to the effects of increasing chlorine burden. Penner and Chang [1978] suggested that the possible influence of changing solar UV flux may hinder this effort. Their study is extended here to investigate whether measurement of other trace species may yield more definitive information. Present study suggests that the long‐term trend in upper stratospheric N2O may provide more suitable data, though indirect, on the supposed solar UV variations, hence better quantification of one potential mechanism of long‐term natural variations in ozone.
Response of the global climate to changes in atmospheric chemical composition due to fossil fuel burning
Authors: Hameed Sultan , Cess Robert D. , Hogan Joseph S.
Published: February 2008

Recent modeling of atmospheric chemical processes (Logan et al., 1978; Hameed et al., 1979) suggests that tropospheric ozone and methane might significantly increase in the future as the result of increasing anthropogenic emissions of CO, NOx, and CH4 due to fossil fuel burning. Since O3 and CH4 are both greenhouse gases, increases in their concentrations could augment global warming due to larger future amounts of atmospheric CO2. To test the possible climatic impact of changes in tropospheric chemical composition, a zonal energy‐balance climate model has been combined with a vertically averaged tropospheric chemical model. The latter model includes all relevant chemical reactions which affect species derived from H2O, O2, CH4, and NOx. The climate model correspondingly incorporates changes in the infrared heating of the surface‐troposphere system resulting from chemically induced changes in tropospheric ozone and methane. This coupled climate‐chemical model indicates that global climate is sensitive to changes in emissions of CO, NOx, and CH4, and that future increases in these emissions could augment global warming due to increasing atmospheric CO2.
The effect of ocean heat capacity upon global warming due to increasing atmospheric carbon dioxide
Authors: Cess Robert D. , Goldenberg Steven D.
Published: February 2008

Time‐dependent global warming due to increasing levels of atmospheric carbon dioxide has been estimated by employing an ocean‐land global climate model. Ocean heat capacity is incorporated by means of a global ocean model having a 70 m deep mixed layer, with heat being transported from the mixed layer to deeper waters by eddy diffusion. The time‐dependent increase in atmospheric CO2, from 1860 to 2025, is taken from carbon‐cycle models. The model results suggest that ocean heat capacity will produce a lag in CO2‐induced global warming of about 2 decades. For example, without inclusion of ocean heat capacity the model predicts that an increase in global surface temperature of 1°C, relative to 1860, will occur by 1988. But when ocean heat capacity is included, the 1°C warming is delayed until 2006–2012, this range of times corresponding to no land‐ocean advective coupling (2006) and complete land‐ocean coupling (2012). By 2025, when the assumed atmospheric CO2 content is twice the 1860 value, the model predicts global warming of 1.5°–1.8°C, in contrast to 3.1°C when ocean heat capacity is neglected.
The role of double diffusion in a Gulf Stream frontal intrusion
Authors: Williams Albert J.
Published: February 2008

Double diffusive convection is possible where large vertical gradients in temperature and salinity tend to compensate in density. Frontal intrusions have these large gradients and can provide the possibility for a salt finger interface at one boundary and a diffusive interface at the other. But large vertical gradients of velocity are present at the boundaries of intrusions, which cause mechanical stirring and turbulent mixing as well. In the exceptionally active intrusions at the Gulf Stream Front near 38°N 69°W, a convective process resulting from incomplete mechanical mixing was observed photographically on both intrusive boundaries.
Emission of iodine from the sea surface in the presence of ozone
Authors: Garland J. A. , Curtis Hilary
Published: February 2008

Iodine‐132 was used as a tracer to demonstrate that ozone causes iodine vapor to be released from the sea surface. This rate of release was porportional to ozone concentration in the range 0–100 ppb and depended on mixing of the water phase. At the mean ozone concentration existing at the sea surface the rate of iodine release was equivalent to an annual contribution of 6 to 12 × 1010 g to the atmosphere. This estimate is subject to uncertainties arising from inadequate knowledge of the mean concentration of iodide at the sea surface and the effect of mixing of the surface sea water on the rate of release of iodine. The significance of such a contribution to the iodine budget of the atmosphere is discussed.
Measurement of the microwave properties of sea ice at 90 GHz and lower frequencies
Authors: Troy B. E. , Hollinger J. P. , Lerner R. M. , Wisler M. M.
Published: February 2008

Passive microwave measurements of sea ice were made at 14, 19, 31, and 90 GHz in a series of aircraft flights over the Greenland Sea in April 1977. Brightness temperatures and emissivities are computed for four types of ice: multiyear (MY), first year (FY), young, and new. The results show that (1) emissivity, defined as the ratio of the measured brightness temperature to the physical temperature of the ice surface, is a more fundamental ice parameter and exhibits less sample to sample variation than the brightness temperature; (2) the emissivity of MY ice decreases between 14 and 31 GHz, but changes little or may even increase between 31 and 90 GHz; (3) the emissivity of FY ice is generally 0.95 or greater at all frequencies, except for an occasional decrease at 90 GHz, which may be due to weathering of the FY ice; and (4) the emissivities of young ice and new ice are less than the emissivity of FY ice.
Model of gravity wave growth due to fluctuations in the air‐sea coupling parameter
Authors: West Bruce J. , Seshadri Venkita
Published: February 2008

The linear Miles‐Phillips model of the coupling between water waves and a turbulent wind field is generalized to include fluctuations in the air‐sea coupling parameter in the dynamic equations. The model is solved exactly, assuming the fluctuations to be delta correlated in time. The energy spectrum of the water wave field is shown to grow exponentially at rates higher then those predicted by the linear Miles‐Phillips model. These increased initial growth rates are consistent with those observed in open ocean measurements.
Microwave radiometer measurement of tidally induced salinity changes off the Georgia coast
Authors: Kendall Bruce M. , Blanton J. O.
Published: February 2008

A quasi‐synoptic survey of tidally induced salinity changes off the Georgia coast was performed by using a L band microwave radiometer onboard a NASA aircraft. Salinity maps were obtained for ebb and flood conditions in order to define the salinity distributions near rivers and sounds and major changes that occur from ebb flow to flood flow. The Savannah River plume dominated the salinity regime and extended out from the Savannah River mouth about 12 km during ebb tidal conditions. The plume merged into a band of low salinity water extending along the Georgia‐South Carolina coast which was produced by the many river sources of freshwater entering the coastal waters. The changes in salinity observed offshore of the river plume area were consistent with estimates of the changes that would occur over a typical tidal excursion perpendicular to the observed gradient.
The temporal and spatial distribution of tropospheric nitrous oxide
Authors: Weiss R. F.
Published: February 2008

The concentration of nitrous oxide has been measured in air samples collected between 1976 and 1980 at several monitoring stations and aboard Oceanographic vessels in the major world oceans. These measurements demonstrate that the tropospheric nitrous oxide concentration is increasing at ∼0.2% per year, thus confirming earlier observations of the increase based on stored samples. The measurements also show that the concentration of nitrous oxide in the northern hemisphere is higher than in the southern hemisphere, the average difference during the sampling interval having been about 0.8 parts per billion (ppb), compared to a January 1, 1978 northern hemisphere dry air mole fraction of 300.2 ppb. The data are well represented by a simple box model which relates the tropospheric rate of increase to an exponentially increasing source function. The observed increase may be explained by combustion of fossil fuels and agricultural activity, with a total source strength of ∼11 × 1010 mol/yr as of January 1, 1978. A substantial fraction of this production is explained by combustion, and agricultural production is therefore considerably less than has been previously estimated. The concentration of nitrous oxide in the preindustrial unperturbed troposphere is estimated to have been between 281 and 291 ppb, depending upon the rate of increase of the mean anthropogenic source function, and the preindustrial latitudinal distribution is estimated to have been nearly uniform. According to the model projections, the concentration of tropospheric nitrous oxide in the year 2000 will be 5 to 7% above present values. The observed rate of tropospheric increase directly affects the production of stratospheric nitric oxide, and plays a significant role in the earth's radiation balance, conservatively estimated as 10–15% of the effect due to increasing carbon dioxide.
In situ observations of ClO in the stratosphere: A review of recent results
Authors: Weinstock E. M. , Phillips M. J. , Anderson J. G.
Published: February 2008

A summary of the results of 10 balloon‐borne in situ measurements of C1O in the stratosphere is presented. All observations were carried out close to local noon at 32°N latitude with solar zenith angles between 24° and 55°. The mean of nine of the observations, which for the most part fall within a well‐defined envelope, is compared with a recently calculated [C1O] distribution between 25 and 42 km at the appropriate latitude and time of day. It is found that while reasonable agreement exists in the 35‐ to 40‐km region, the ratio of calculated to observed [C1O] increases monotonically with decreasing altitude below 35 km, reaching approximately three at 25 km. The tenth observation exhibits a mixing ratio nearly an order of magnitude greater than the mean. An analysis of the relevant chemistry below 30 km is presented which indicates that the discrepancy between the observed mean and the calculated [C1O] distribution can be linked to uncertainties in the [OH]/[NO] ratio in the lower stratosphere. A comparison is made between the in situ resonance fluorescence observation reported here and the remote laser heterodyne radiometer measurements of Menzies. Finally, the fractional destruction of Ox = O3 + O(3P) by C1Ox = Cl + C1O, based on the observed mean of the in situ [C1O] and [O(3P)] midday observations, is presented for the altitude interval 27–41 km.
Spatial and temporal variations of monthly mean total columnar ozone derived from 7 years of BUV data
Authors: Tolson Robert H.
Published: February 2008

The monthly mean total columnar ozone fields are represented by ninth degree spherical harmonic models. Spatial spectra are defined in terms of simple analytic expressions which represent the rms value of each spherical harmonic coefficient. These spectra are combined with estimation theory techniques to develop a realistic error analysis that accounts for errors due to nonglobal coverage. Over the 7‐year data set, systematic variations are represented by an annual, semiannual, and biennial model, along with secular trends where required. The annual component of zonal mean ozone compares favorably with previous results based on Dobson data. The semiannual term is shown to be the dominant variation near the South Pole. In the tropics, the results support the theory that enhanced Hadley cell circulation is responsible for the biennial variation in zonal mean ozone. Amplitude and phase variations for longitudinal waves 1, 2, and 3 are presented. In the northern hemisphere, these waves reinforce in space and time during the period of high poleward transport of ozone. In the southern hemisphere, the wave 2 and 3 components are much smaller, and wave 1 maximum amplitude occurs in September and October.
Seasonal variations in aerosols and atmospheric transmission at Mauna Loa Observatory
Authors: Bodhaine B. A. , Mendonca B. G. , Harris J. M. , Miller J. M.
Published: February 2008

Aerosol light scattering and atmospheric transmission data taken at Mauna Loa Observatory show seasonal variations that are strongly correlated and in phase. Total ozone above Mauna Loa is also in phase but accounts for only about 20% of the seasonal variation in atmospheric transmission while aerosols account for the other 80%. Total precipitable water vapor above Mauna Loa is out of phase with atmospheric transmission and cannot account for its seasonal variation. Long‐range atmospheric trajectory analyses indicate that tropospheric transport of aerosols from the direction of the Asian continent is most likely responsible for the seasonal variations in atmospheric transmission and aerosol optical properties.
Linear and nonlinear aspects of snow albedo feedbacks in atmospheric models
Authors: Roads John O.
Published: February 2008

Namias' hypothesis, that anomalous snowcover on the eastern side of the North American continent can generate an anomalous east coast low pressure system and an anomalous inland high pressure system, is consistent with the time‐averaged anomalous response from a nonlinear, primitive equation channel model with an idealized, flat land‐sea arrangement. An attempt to understand and describe this anomalous response in the nonlinear model as a linear response to anomalous diabatic heating was largely unsuccessful, primarily because the anomalous eddy fluxes were also important. This unsuccessful attempt to describe the nonlinear model's time averages by linear theory then motivated several comparisons between linear and nonlinear severely truncated quasi‐geostrophic models. It was also found in these models that the eddy fluxes were extremely important for forcing or dissipating the stationary eddies.
Stratospheric aerosols and the tropospheric energy budget: Theory versus observations
Authors: Coakley James A.
Published: February 2008

Changes in the diffuse and direct solar radiative fluxes observed at the surface can serve as a direct indication of how efficiently a stratospheric aerosol layer removes solar energy from the troposphere and thereby causes tropospheric cooling. Observed changes after the eruption of Agung in 1963 are compared with estimates derived from published results of theoretical calculations for the impact of stratospheric aerosols on the earth's energy budget. The comparison reveals that the aerosol layer that formed after Agung could have caused two to three times the tropospheric cooling obtained with the theoretical calculations. The discrepancy is, however, mitigated by the large uncertainties associated with the observations. Because of the large uncertainties, the theoretical results cannot be regarded as unrealistic. To reduce the observational uncertainties, it is recommended that (1) the change in diffuse to change in direct flux ratio be derived from observations of the diffuse to direct ratio obtained with a single instrument, so that errors associated with photometric calibration are eliminated, (2) auxiliary observations be made so that changes caused by a stratospheric aerosol layer may be isolated from other changes in the atmosphere, and (3) observations be made at sites where background changes are minimal.
Atmospheric methane (CH4): Trends and seasonal cycles
Authors: Rasmussen R. A. , Khalil M. A. K.
Published: February 2008

On the basis of 22 months of almost continuous, automated, GC/FID measurements of atmospheric CH4 at Cape Meares (45°N), we show that the concentration of CH4 is increasing at about 2% per yr (±0.5% yr−1). The data also revealed stable seasonal cycles with peak concentrations in October and minimum concentrations in July. The magnitude of the seasonal variations during these months is about ±20 ppbv from the average (∼±1.2%). If the current trend continues, the increased CH4 concentration may result in a 0.2°K to 0.4°K average increase in earth's surface temperature over the next 40 years or so (based on calculations of Wang et al. (1976)). The coupling of CH4 to tropospheric and stratospheric chemical processes is discussed.
Evaluation of the rate of uptake of nitrogen dioxide by atmospheric and surface liquid water
Authors: Lee Yin‐Nan , Schwartz Stephen E.
Published: February 2008

The rate of uptake of NO2by liquid water according to (R1), 2NO2(g) + H2O(1) → 2H++ NO3−+ NO2−, is shown to be unaffected by O2(0.2 atm). Hence the rate constant and Henry's law solubility constant of NO2previously obtained may be employed to evaluate the rates of aqueous phase reactions of NO2in the ambient atmosphere. Reactions (R1) and (R2), NO2(g) + NO(g) + H2O(1) → 2H++ 2NO2−, are quite slow at representative atmospheric partial pressures and cloud liquid water content; the characteristic times range upward from 103–104hours at 10−7atm, increasing with decreasing partial pressures of the gases. Direct acidification of cloud liquid water by (R1) or (R2) is also unimportant. Catalytic enhancement of (R1) is potentially important for catalyst concentrations of order 10−7M, assuming sufficiently fast rate constants (∼108M−ls−1). Iron‐catalyzed reaction in particular, however, is found to be unimportant. Reaction of NO2with dissolved S(IV) is potentially mportant, based upon an assumed upper limit rate constant of 2.5×107M−1s−1. Deposition of NO2to surface (ocean or lake) water is shown to be controlled by aqueous phase mass transport and/or reaction and is much slower than heretofore assumed.
An advective model for two‐dimensional transport of stratospheric trace species
Authors: Holton James R.
Published: February 2008

A parameterization of two‐dimensional transport is developed for application to photochemical models of stratospheric trace species. It is shown that in a first approximation tracer transport in the meridional plane may be treated as an advective, rather than a diffusive, process. The mean meridional motion used in this advective model is a modified Eulerian mean which is a good approximation to the Lagrangian mean motion. The potential of the proposed parameterization is demonstrated by a simple numerical experiment in which the equilibrium distribution is computed for a tracer with a uniform tropospheric source and a stratospheric sink proportional to the local mixing ratio. The resulting distribution is qualitatively in accord with the oberved stratospheric distribution of trace species whose sources are in the troposphere, e.g., N2O.
The influence of radon diffusion on the 210Pb distribution in sediments
Authors: Imboden Dieter M. , Stiller Mariana
Published: February 2008

A mathematical model is presented which describes the distribution of radon 222 in sediments having a constant or variable depth distribution of radium 226. The model is extended to the distribution of lead 210, taking into account the mobility of radon (the precursor of 210Pb) within the sediment column. The 210Pb model is compared, at constant radium activity, with the conventional approach which disregards the radon diffusion when estimating sedimentation rates by the 210Pb method. The ratio between apparent and real sedimentation rate, s′/s, expressed as a function of three dimensionless parameters, demonstrates the importance of the radon diffusion effect. This effect is particularly important for sediments with small initial excess 210Pb activity, small sedimentation rate, large radon diffusivity, or a combination of these factors. Applied to Lake Geneva, the sedimentation is estimated to be larger by 30–50% than the original value by Krishnaswami et al. (1971). In sediments which are mixed at the surface (physical mixing or bioturbation), the 210Pb activity in the mixed layer is diminished compared to that in the settling sediment material (Robbins et al, 1977), and radon diffusion makes the activity difference even larger, especially for low initial excess 210Pb activity, small sedimentation rate, and large mixing intensity. This result may be of importance for the balance of 210Pb in an aquatic system if the calculations are based on activities measured in the sediment.
The volcanic explosivity index (VEI) an estimate of explosive magnitude for historical volcanism
Authors: Newhall Christopher G. , Self Stephen
Published: February 2008

Knowledge of the frequencies of highly explosive, moderately explosive, and nonexplosive eruptions would be useful in a variety of volcano studies. Historical records are generally incomplete, however, and contain very little quantitative data from which explosive magnitude can be estimated. Only the largest eruptions have a complete record back to the early 19th Century; other important explosive events went unrecorded prior to about 1960. Only a handful of the very biggest eruptions are represented in the geologic record, so it will be impossible to augment historical records post facto. A composite estimate of the magnitude of past explosive eruptions, termed the Volcanic Explosivity Index (VEI), is proposed as a semiquantitative compromise between poor data and the need in various disciplines to evaluate the record of past volcanism. The VEI has been assigned to over 8000 historic and prehistoric eruptions, and a complete list is available in a companion document.
Space/time statistics of short‐term climatic variability in the western North Pacific
Authors: White W. B. , Meyers G. , Hasunuma K.
Published: February 2008

Temperature observations routinely taken over a period of years are analyzed for information on the space/time statistical structure of the short‐term, climate‐related variability in the western North Pacific. Observations were taken by the RV Ryofu Maru, making winter hydrographic transects along/ 137°E from Japan to the equator each year from 1967–1974, and by the Japanese Far Seas Fisheries Agency, making 120 quasi‐meridional bathythermograph sections between 125°E and 180° from Japan to the equator during 1968–1972. Meridional wave number spectra of subsurface temperature over the depth range 100–300 m are calculated from the sections. Spectra vary significantly between the tropical region south of 17.5°N and the subtropical region north of 17.5°N. In both regions, wave number spectra increase in spectral energy density as the inverse square of the wave number from wavelengths of 200–1200 km; this indicates that the spectra derive from a first‐order, autoregressive process. Decorrelation scales associated with the first‐order process are very different for the two regions. Evaluation of these parameters is obtained by fitting the observed wave number spectra with a model spectrum that is composed of a first‐order autoregressive process and a white noise process. The best‐fit decorrelation scale of the first‐order process is 600 km in the tropics (south of 17.5°N) and 300 km in the subtropics (north of 17.5°N). The model permits the partition of temperature variance into climate‐related signal variance, and noise variance that cannot be resolved by routine monitoring. The ratio of noise to signal variance is 0.3 in the tropics and 1.0 in the subtropics. Estimates of the time and zonal space decorrelation scales are determined from autocorrelation analysis of the Japanese Far Seas Fisheries Agency temperature data. Both north and south of 17.5°N, the decorrelation time scale in the subsurface temperature is approximately 6 months. The zonal decorrelation length scale in the subsurface temperature is approximately 10° longitude for the tropical region south of 17.5°N, but only about 2.5° longitude for the subtropical region north of 17.5°N. For equal time scales, it is shown that the spectral shapes and the latitudinal differences in zonal space scale are consistent with the representation of upper ocean thermal variability in terms of nondispersive baroclinic long waves (i.e., Rossby waves). Discussed are implications of this space/time statistical information on the design of monitoring networks used to detect shor‐term climate‐related variability in thermal structure.
Measurements of electric field and vertical distribution of space charge close to the ground during the solar eclipse of February 16, 1980
Authors: Kamra A. K. , Teotia J. K. S. , Sathe A. B.
Published: February 2008

Atmospheric electric field at ground level and space charge at 0.1, 1, and 2 m above the ground have been measured at Poona during the solar eclipse of February 16, 1980. Electric field was measured with a radioactive probe and the space charge by direct filteration technique. About 57 min after the first contact, the space charge at the 2‐m level showed a remarkable increase in its fluctuations with no parallel changes at 0.1 and l m levels. About 41 min after the maximum phase of the eclipse, the space charge at all three levels experienced negative pulses and remained negative at 0.1 and l m levels, even a few minutes after the end of the eclipse. During this time the electric field decreased for some time to almost its zero value. Influence of the space charge observed at these levels in decreasing the electric field has been examined. Possible role of eddies motion in causing the space charge variations close to the ground is discussed.
Atmospheric chemistry of ethane and ethylene
Authors: Aikin A. C. , Herman J. R. , Maier E. J. , McQuillan C. J.
Published: February 2008

A detailed study of ethane and ethylene photochemistry is presented for the troposphere and stratosphere. It is demonstrated that the loss of ethane is controlled by OH in the troposphere and Cl in the stratosphere. Observations of ethane show a stratospheric behavior indicative of a free chlorine concentration below 30 km that is only 10% of the predicted value given by both our photochemical model calculations and those done by others. The inferred lower amount of chlorine cannot be explained by heterogeneous processes for concentrations of aerosols representing average background conditions, nor does current stratospheric photochemistry show agreement. Chemical destruction of ethane and ethylene within the atmosphere leads to the production of carbon monoxide, formaldehyde, and other products. Tropospheric concentrations of formaldehyde are enhanced by nearly a factor of 3 for an ethylene mixing ratio of 2 ppb. Simultaneous monitoring of formaldehyde and carbon monoxide, as well as other products, will greatly aid in determining the relative importance of different tropospheric CO sources. Peroxyacetyl nitrate (PAN) acts as a reservoir for odd‐nitrogen at the expense of HNO3, HO2NO2, NO, and NO2.
Observation of the lateral fluctuation of the laser beam passing through the atmosphere
Authors: Yokoi Takehisa
Published: February 2008

Lateral fluctuation of the laser spot formed after passing through a distance of 2.26 km above the sea surface was observed together with the air, the surface water temperatures, and the relative humidity. Our main phenomenalistic findings were as follows: (1) a maximum value of the vertical displacement of the beam spot and that of its time rate were 2.1 m and 0.5 m/min, respectively; (2) the ‘large fluctuation,’ the displacement larger than 10 cm, was likely to occur just before the sunrise and, more remarkably, just after the sunset; (3) in each run of observation the frequency of such a large fluctuation seemed to be correlated with the changes in the air temperature and the relative humidity, and (4) an increment of the temperature gradient corresponding to the maximum displacement of 2.1 m was estimated to be 0.77 deg/m.
Evaluation of the SEASAT altimeter time tag bias
Authors: Schutz B. E. , Tapley B. D. , Shum C.
Published: February 2008

Because of the variable effect on the altimeter height processing produced by a constant error in the altimeter time tag, the accuracy of the time tag is an important factor in the applications of the 10‐cm SEASAT altimeter data. An assessment of the internal delays inherent in the altimeter microprocessor suggested that −79.4 ms should be added to the time tags transmitted to the ground receiving stations. To ensure the validity of this value, analyses were undertaken with the altimeter data. Two methods were used in these analyses which benefited from a global data distribution in the oceanic areas. These methods were (1) the crossover method which used altimeter data differenced at points where the SEASAT ground track intersected with itself and (2) the direct use of the altimeter data. The former method is independent of errors in the geoid model; hence it is considered to produce the most reliable results. Using the crossover method and several different ephemerides, various values of the time tag bias were estimated. For all crossover results the adopted value of −79.4 ms is within the bounds of the standard deviation associated with the estimates. In particular, the estimate of −78.1±2.0 ms is considered to best represent the set of estimated values.
The variation of sea surface temperature in 1976 and 1977 1: The data analysis
Authors: Miyakoda K. , Rosati A.
Published: February 2008

To study the spatial distribution of the sea surface temperature (SST) for the years of 1976 and 1977, ship and satellite data at 1° quadrangles were collected. Two points were investigated: (1) the difference of monthly mean SST data between the two sources, and (2) map analyses over the globe. The study shows that without satellite data, an adequate coverage of world ocean is not possible and that there is a large difference in values between the ship and satellite data. The standard deviation of the difference between the satellite and merchant ship SST data for monthly and 1° quadrangle mean was ±1.49°C, where the sampling errors were not subtracted. Using these data, analyses were created and compared with independent analyses. The comparisons included large‐scale analyses and two small‐scale analyses. Attention was focussed specially on (1) the utility of the satellite SST data and (2) the data quality control. The large‐scale analyses agreed well with the independent analyses. However, both of the small‐scale analyses did not compare well.
The faint young sun‐climate paradox: Continental influences
Authors: Endal Andrew S. , Schatten Kenneth H.
Published: February 2008

We examine the various mechanisms which have been proposed to compensate for the climatic effects of a 30% increase in the solar luminosity over the past 4½ billion years. Although atmospheric greenhouse effects have received most attention, other mechanisms may have played a role of comparable importance. In particular, we note that the development of continents during the past 2½ billion years could have had a significant secular effect on the atmosphere‐ocean heat transport system. As a result, past climates may have been less susceptible to complete freeze‐over. A simple energy balance model is used to demonstrate the magnitude of this effect. Because the CO2 greenhouse effect is not the only means of compensating for solar evolution, the faint‐young‐sun problem should not be used to infer past levels of atmospheric CO2.
Observations of salt fingers in the central waters of the eastern North Pacific
Authors: Gargett A. E. , Schmitt R. W.
Published: February 2008

This paper presents direct measurements of the temperature signature of salt fingers, observed by a horizontally towed temperature sensor at a station in the middle of the subtropical gyre in the eastern North Pacific. The observed spectral shape compares favourably with predictions from the spectral model of Schmitt (1979a), in which a wide range of finger wave numbers grow. The buoyancy flux due to temperature across the fingering interface is estimated by three methods: a ‘direct’ determination from the observed temperature gradient variance and predictions from two laboratory flux laws. The order‐of‐magnitude agreement among these estimates is an encouraging start to the problem of parameterizing the heat, salt, and buoyancy fluxes associated with salt fingering in the Central Waters of the subtropical gyres, a very real problem in view of the widespread occurrence of salt‐fingering signatures in the towed temperature records.
Nonsteady state simulations of the global mercury cycle
Authors: Millward G. E.
Published: February 2008

A time‐dependent global cycling model consisting of five reservoirs has been developed to examine the effects of the anthropogenic mobilization of mercury. An unpolluted steady state was perturbed by allowing the mercury efflux from the land to the atmosphere to increase with time, in line with trends implied from mercury in Greenland ice cores and present day fluxes. The results showed that with a variety of initial conditions the atmospheric content increased by a factor of about 6 with a maximum concentration occurring some 700 years after the perturbation. The ocean surface increased by about 50% over the same time scale and both these biologically important reservoirs relaxed to new steady states in about 4000 years. The sensitivity of the model to changes in some of the important rates was investigated.