bluuebunny/crossref_metadata_2025 huggingface dataset:
Climatic signals of the Antarctic Ocean
Authors: Fletcher J. O. , Radok U. , Slutz R.
Published: February 2008

A preliminary examination of the winds and sea surface temperatures in the 120‐year record of ocean climate produced by the Historical Sea Surface Temperature Project has provided evidence of two distinct ocean‐wide modes of variability. One of these has a typical time scale of a few years and is closely related to the EI Niño phenomenon. The other has a time scale of the order of 30–100 years and has exhibited sharp changes in higher southern latitudes. However, the uneven distribution of the marine observations in space and time is a potential source of spurious anomaly changes. A comparison of average ship winds for different‐sized areas with winds derived for the same areas from weather charts is presented to illustrate the limited significance that can be attached to the local anomalies; this points up a need for the joint interpretation of anomaly changes over wider areas as resulting from changes in the characteristic behavior of synoptic pressure systems. A tentative explanation of the nearly simultaneous changes in the winds and sea surface temperatures of the latitude belt 40°S to 50°S is derived from Wyrtki's (1960, 1961) circulation model for the Southern Ocean. That region apparently plays a leading role in the long‐term fluctuations of ocean climate through the Antarctic Intermediate Water and Sub‐Antarctic Mode Water. These water masses acquire their characteristics from the surface energy balance and sea ice processes in high southern latitudes and occupy a deep layer extending up to just below the thermocline in the tropical ocean; it is suggested that they could be a pathway for climatic signals from the Antarctic Ocean to the rest of the globe.
The transport of heat, water vapor and particulate material to the south polar plateau
Authors: Hogan A. , Barnard S. , Samson J. , Winters W.
Published: February 2008

A systematic series of aerosol observations was begun at South Pole in 1974. These observations were coordinated with surface meteorological observations and soundings. Concurrent ozone observations began shortly after, and water vapor measurements, using an electrolytic cell, were begun in 1976. During 1977 and 1978 airborne aerosol and meteorological observations from an instrumented LC 130R were used to construct vertical profiles over the polar plateau, the Ross Sea, and Ross Ice Shelf, and to make constant altitude transects from the periphery to the interior of the continent. Analysis of the airborne aerosol observation shows that the most moist and aerosol‐laden air over the interior of the continent is found in, and just above, the inversion, a few hundred meters above the surface. Aerosol concentrations decrease above this layer, to and through the tropopause. The surface aerosol, water vapor, and temperature record has been stratified by 20° sectors of wind direction occurring concurrent with the observations. This analysis supports a simple meteorological model of transport to the South Polar Plateau. When the polar high is centered over the center of the Antarctic ice mass, the normal condition katabatically reinforced weak gradient wind occurs, and South Pole receives surface winds from the grid northeast. When this high is centered on the Greenwich meridian, warm, moist, aerosol‐laden air can flow along a short path from the Weddell Sea to the pole. When this high is centered along the dateline, the air has a long trajectory over ice and arrives at the pole along 090° depleted of heat, water vapor, and aerosol. Combining the surface and airborne aerosol observations for analysis indicates that the preferred levels for transport of particulate matter to the pole occurred in the lower troposphere.
Cloud cover from high‐resolution scanner data: Detecting and allowing for partially filled fields of view
Authors: Coakley James A. , Bretherton Francis P.
Published: February 2008

We present a new technique for obtaining cloud cover and determining clear sky radiances using high‐resolution infrared scanner data. The technique, which can be automated, uses the spatial structure of the IR radiance field to identify radiances associated with fields of view that are either free of clouds or completely covered by clouds drawn from one or more distinct layers. As the method uses only infrared radiances, it should provide equally good results for both daytime and nighttime observations. The approach is particularly suited for determining clear sky radiances over oceans from which sea surface temperature might be derived. In addition, for single‐layered systems, the cloud cover fraction for a given region may be obtained from the clear sky radiance, the completely cloud covered radiance, and the mean radiance for the region. For such systems the separation of completely covered from partially covered fields of view allows an estimate of the errors associated with commonly used threshold techniques for determining cloud cover. These errors are, in general, shown to be highly sensitive to the applied threshold and to depend on the cloud‐areal size distribution. In addition, unlike the spatial coherence method described here, histograms and correlations of visible and IR radiances as proposed for archiving information on cloud cover may fail to reveal the layered structure of cloud systems. Furthermore, the high local structure observed for the visible radiances of regions that appear to be completely cloud covered makes it impossible to obtain reliable estimates of the cover from visible radiances alone.
Microwave spectra of terrestrial mesospheric CO
Authors: Clancy R. Todd , Muhleman Duane O. , Berge Glenn L.
Published: February 2008

The earth's mesospheric carbon monoxide was observed in absorption against the moon in early December 1979 at a wavelength of 1.3 mm and in early December 1980 at a wavelength of 2.6 mm. These wavelengths correspond to the respective rotational transitions of CO, J = 1 → 2 and J = 0 → 1. No significant change in the column density of CO above ∼65 km is found between the 1979 and 1980 observations. Inversion of the spectra did not provide unique CO mixing ratio profiles for a direct quantitative comparision of December 1979 and 1980 profiles, due to limited signal‐to‐noise ratios. Comparison with other published spectra of mesospheric CO suggests a large seasonal variation (about a factor of 2–3) in the column density of CO above 65 km, with a maximum in winter and a minimum in summer.
Dynamic response of thin‐wire wave gauges
Authors: Liu H.‐T. , Katsaros K. B. , Weissman M. A.
Published: February 2008

A series of experiments was conducted in a wind‐wave tank to determine the dynamic response of thin‐wire wave gauges as a function of probe diameter in terms of their spatial resolution and frequency response. Two resistance thin‐wire gauges with probe diameters of 0.13 and 0.4 mm were used in the experiments. They were calibrated against a nonintrusive, optical device (the laser displacement gauge, or LDG). The two thin wires were mounted side by side in close proximity to the laser beam at a fetch of 4 m. The outputs from the LDG and thin‐wire gauges were recorded alternately as well as simultaneously by using two separate recording systems. The spectral density measured with the LDG proves to be consistently higher than that measured with either thin wire, especially for frequencies higher than the dominant frequency. Only a slight difference is observed between the two spectra of the thin‐wire data. From the experimental results, an empirical correction for the meniscus‐induced bias in the variance spectrum of capillary waves is derived.
Bedload and wave thrust computations of alongshore sand transport
Authors: Hallermeier Robert J.
Published: February 2008

First‐order approximations permit an analytical integration of alongshore bedload transport by waves within the littoral zone. This analysis treats shallow‐water linear waves with refraction and reflection along an idealized slope, and the equation giving alongshore bedload rate is fairly consistent with the alongshore sediment transport rate due to wave thrust. By importance, there are dependences on wave height, angle, and frequency; sediment characteristics and nearshore slope also occur in the bedload result. Among available laboratory measurements of total alongshore sand transport, 57 tests from 7 studies have satisfactory situation and documentation for evaluation of the bedload analysis. These data are correlated somewhat better by the wave thrust than by the bedload computations, but there is an unexplained dependence of transport rate on surf character. Both this effect and the bedloadlike dependences of the wave thrust result appear important to prediction of extreme alongshore transport rates.
Atmospheric CO volume mixing ratio profiles determined from dround‐based measurements of the J = 1 → O and J = 2 → 1 emission lines
Authors: Kunzi K. F. , Carlson E. R.
Published: February 2008

We report measurements of the J = 1 → 0 and J = 2 → 1 emission lines of mesospheric CO at 115 and 230 GHz, respectively, and the first use of these emission lines to obtain CO volume mixing ratio profiles. The radiative transfer equation that connects the observed transition line shape and the volume mixing ratio profile is presented, and the process for inverting the line shape to obtain a profile is discussed. The profiles resulting from our measurements are similar to but not identical with other experimental and theoretical results, and they show lower CO at altitudes below 50 km than expected from in situ measurements.
Stratospheric negative‐ion reaction rates with H2SO4
Authors: Viggiano A. A. , Perry R. A. , Albritton D. L. , Ferguson E. E. , Fehsenfeld F. C.
Published: February 2008

A recently measured value of the dipole moment of H2SO4 necessitates a recalculation of stratospheric negative ion reaction rate constants with H2SO4. The measured reaction rate constants were normalized to a theoretical limit which depends on this dipole moment. The revised values are increased by the factor 2.7. Deduced values of stratospheric vapor phase sulfuric acid from ion composition measurements are inversely proportional to the reaction rate constants.
The subtidal circulation in Delaware Bay and adjacent shelf waters
Authors: Pape Edwin H. , Garvine Richard W.
Published: February 2008

Surface and seabed drifters were used to study the subtidal circulation in Delaware Bay and over the adjacent continental shelf of the Middle Atlantic Bight. Over 7000 drifters were released in eight experiments during the year‐long study period. Velocity vector maps representing the study period mean fields for the surface and bottom confirmed the pattern of classical, two‐layer, estuarine flow, with surface water moving seaward from the Bay onto the shelf and bottom water landward over the shelf from at least as far as 40 km seaward of the Bay mouth. Within the Bay, bottom water moved laterally toward the nearest shore, diverging horizontally along a line roughly marking the deep channels. The surface speeds were about an order of magnitude larger than the bottom. Significant variations from this mean pattern were seen between the eight experiments. Return percentages for surface and bottom drifters correlated inversely over the eight experiments. Correlations with wind stress were above the level of significance, and winds explained about two‐thirds of the total variance. The strong coupling found between the subtidal circulation in the estuary and over the shelf is consistent with recent observational and modelling studies.
Sporadic transport and deposition of continental aerosols to the Pacific Ocean
Authors: Tsunogai Shizuo , Kondo Tadahiro
Published: February 2008

Aerosol samples were collected in the surface air over the North Pacific on board a vessel in May and June 1980 and were analyzed for Na, Al, Fe, Mn, and 210Pb. The results of the analysis of duplicate samples show good agreement. The concentration ratios of Fe/Al and Mn/Al are similar to those of crustal material. The concentration of Al in the maritime surface air was usually observed to be 30–50 ng/m3. On June 9, however, an extremely high concentration of 670 ng/m3 of Al was observed at 30°N, 161°E. The Al concentration is still insufficient to explain the accumulation rate of aluminosilicate in the pelagic sediment if the deposition velocity is 1 cm/s, but the nature of the ‘Kosa’ particles is possible to explain it, even though the dust particles are sporadically transported. Although both Al and 210Pb are of continental origin, the behavior of 210Pb is somewhat different from that of Al.
The quasi‐biennial oscillation in atmospheric ozone
Authors: Oltmans Samuel J. , London Julius
Published: February 2008

Analysis of various characteristic of the statistical spectra of total ozone covering a 15 year period (1964–1978), and of ozone in the stratosphere over a period of about 7 years, indicates that the strong QBO in the zonal winds of the tropical stratosphere is associated with a detectable, although often weak, signal in total ozone and the ozone concentration in the lower and middle stratosphere. The region of strongest relationship between tropical stratospheric zonal winds and total ozone (e.g., maximum ozone associated with strong west winds) is in the tropics, mid‐latitudes of the southern hemisphere, and, apparently, at high latitudes of the northern hemisphere. The observed period of the ozone QBO decreases from 27 months at the equator to about 24 months in mid‐latitudes possibly due to local modification of the QBO, as it propagates poleward. In the tropics the ozone variation appears to be nearly in phase with the tropical wind QBO while at middle and high latitudes of the northern hemisphere and mid‐latitudes of the southern hemisphere the ozone oscillation seems to lag the wind oscillation by about 12–14 months. The out‐of‐phase relationship at middle and high latitudes suggests a possible interaction between the tropical stratosphere QBO in zonal winds and the annual variation in poleward transport of ozone by quasi‐horizontal eddies.
Sea surface temperature estimation using the NOAA 6 satellite advanced very high resolution radiometer
Authors: Bernstein R. L.
Published: February 2008

A procedure for estimating sea surface temperature was developed by using the near and thermal infrared data available from full resolution (1.1 km field of view) daytime passes of the NOAA 6 satellite Advanced Very High Resolution Radiometer. It is demonstrated that spatially unresolved clouds and variable amounts of water vapor in the atmosphere are the major error sources. The procedure therefore incorporates a means of identifying radiometer fields of view which are virtually cloud‐free, by comparing measured solar radiation at 1 μm, backscattered from the atmosphere, against that expected from a simple scattering model. A set of 82 cloud‐free fields of view is then assembled, spatially and temporally nearly coincident with research quality (±0.2°C) in situ ship and buoy sea surface temperature reports collected during 1979 and 1980. The set is then used to develop and evaluate a simple model to reduce variable water vapor effects by relating in situ sea surface temperature to the infrared brightness temperatures measured by the radiometer at 3.7 and 11 μm. Residual disagreement between satellite estimates and in situ measurements of sea surface temperature is about 0.6°C for the data set which extends from the equator to 50°N in the northeast Pacific. The procedure is then applied to 10 satellite passes in the northeast Pacific during April 1981 to obtain monthly mean sea surface temperature and temperature anomaly (departure from climatological norm) maps. These maps are compared against similar ones produced from routine ship reports, mostly consisting of engine injection temperature data, typically good to no better than 1°C. The maps agree to ±0.8°C (1 sigma), with the level of agreement clearly limited by the poor accuracy of the ship reports. It now appears that the radiometer data, when properly handled, can be used as a more accurate substitute for routine ship reports of sea surface temperature in applications such as climate variability studies requiring 0.5–1.0°C accuracy.
Oceanographic aspects of the Emperor Seamounts region
Authors: Roden Gunnar I. , Taft Bruce A. , Ebbesmeyer Curtis C.
Published: February 2008

Effects of the Emperor Seamount Chain on the thermohaline structure and baroclinic flow are investigated on the basis of historical hydrographi data. The amplitudes of dynamic height perturbations are 3 to 5 times larger west than east of the chain. The intensity of the thermal fronts is stronger west than east of the seamounts; near the crest of the southern seamounts, strong east‐west thermohaline fronts and a strong northward baroclinic flow are observed. The Kuroshio Extension west of the seamount chain is a well‐defined meandering current, the axis of which generally lies between 33° and 36°N. The available data indicate that the Kuroshio Extension turns northward and then flows eastward through the gaps of the seamount chain. East of the seamounts, the Kuroshio Extension widens threefold and appears to be poorly defined.
Balloon‐borne observations of stratospheric aerosol and condensation nuclei during the year following the Mt. St. Helens eruption
Authors: Hofmann D. J. , Rosen J. M.
Published: February 2008

Thirty‐six balloon flights, carrying various particle counters, are used to study the stratospheric aerosol layer during the year following the Mt. St. Helens volcanic eruption which occurred on May 18, 1980. Aerosol enhancements were observed to altitudes as high as 26 km. For the first time, stratospheric condensation nuclei (r ≥ 0.01 μ m) were observed in conjunction with a volcanic eruption. Time variation of these small particles suggests their continuous nucleation for at least 1½ months after the eruption. Particles formed in the stratosphere following this eruption were generally smaller than those observed following the eruption of Fuego in 1974. This may be related to a relative excess in condensation sites at the time of the Mt. St. Helens eruption, thus resulting in smaller particles due to increased competition for the available sulfurous vapors involved in the nucleation process. The excess mass concentration of volatile material which remained in the stratosphere about 6 months after the eruption was of the order 10−7g cm−2 (column) and if assumed to be uniform over the northern hemisphere, would amount to about 0.25 Tg. This is about 3 times the background level but only one half that injected by the eruption of Fuego in 1974.
Characterization of trace gases in 1980 volcanic plumes of Mt. St. Helens
Authors: Cronn Dagmar R. , Nutmagul Winai
Published: February 2008

Over 50 whole‐air gas samples were collected in Mt. St. Helens volcanic plumes beginning with the original steam and ash plumes in March 1980 and continuing through June 1980. Four research aircraft were used to collect the samples, which were analyzed by five different analytical techniques for 14 separate trace gases. COS, CS2, CH3Cl, CO2, CO, N2O, C2H6 and C2H2 were found in elevated amounts in the volcanic plume gases. Order‐of‐magnitude estimates of COS, CS2, CH3Cl, CO2 and CO fluxes have been made for several types of eruptive phases. COS was a substantial fraction of the sulfur‐carrying gases during the May 18 eruptions, although SO2 and H2S still predominated.
Maxwell currents under thunderstorms
Authors: Krider E. Philip , Musser James A.
Published: February 2008

We point out that recent observations of the time variations in thunderstorm electric fields, both aloft and at the ground, can be interpreted in terms of a total Maxwell current density that varies slowly with time in the intervals between lightning discharges. We utilize this quasi‐static behavior to estimate and map the Maxwell current densities under a small Florida thunderstorm using data provided by a large field mill network. An area integral of these current densities gives a total Maxwell current just above the ground of about 0.5 A, a value which is a reasonable lower limit for the total Maxwell current produced by the cloud, and an upper limit for the rate of charge transport to ground between lightning flashes. Using the quasi‐static behavior of the Maxwell current density, we derive an expression for the field‐dependent current density under a thunderstorm during the field recovery following a lightning discharge, and we infer values of air conductivity under the small storm which range from 2 to 6×10 −13 mho/m. Finally, we present data that indicate that the area‐average Maxwell current is not usually affected by lightning, but instead varies slowly throughout the evolution of the storm. Therefore, we suggest that cloud electrification processes probably do not depend on the cloud electric field, which exhibits large and rapid time variations, as much as they do on more slowly varying quantities, such as the meteorological structure of the storm and/or the storm dynamics.
Long‐range propagation of sound through oceanic mesoscale structures
Authors: Mercer J. A. , Booker J. R.
Published: February 2008

Assumptions related to the feasibility of ocean acoustic tomography are investigated utilizing range‐dependent sound‐speed profiles. The models include a warm midocean eddy and a cold core Gulf Stream ring superposed on a latitudinal geographic variation covering 1000 km. The results show that changes in the acoustic travel times produced by mesoscale features can be nonlinear, that the ray paths are substantially displaced by a mesoscale eddy, and that information from a single source and receiver can be used to infer the distance to a mesoscale disturbance.
Three‐dimensional tracer model study of atmospheric CO2: Response to seasonal exchanges with the terrestrial biosphere
Authors: Fung I. , Prentice K. , Matthews E. , Lerner J. , Russell G.
Published: February 2008

A three‐dimensional tracer transport model is used to investigate the annual cycle of atmospheric CO2 concentration produced by seasonal exchanges with the terrestrial biosphere. The tracer model uses winds generated by a global general circulation model to advect and convect CO2; no explicit diffusion coefficients are employed. A biospheric exchange function constructed from a map of net primary productivity, and Azevedo's (1982) seasonality of CO2 uptake and release closely simulates the annual cycles at coastal stations. The results show that zonal homogeneity in surface CO2 concentrations can never be achieved at mid‐latitudes where the time scale for zonal mixing is longer than the time scale for biospheric exchange. Analysis of the zonal mean balance in the lower troposphere reveals that atmospheric transport processes may alter the CO2 response to local biospheric exchanges by 50% or more. Hence year‐to‐year variation of the annual CO2 cycle may result from the natural variability of the atmospheric circulation as well as from changes in the sources and sinks.
A numerical model of the zonally averaged dynamical and chemical structure of the middle atmosphere
Authors: Garcia Rolando R. , Solomon Susan
Published: February 2008

A two‐dimensional, time‐dependent model has been constructed to study the zonally averaged structure of the middle atmosphere (16–116 km) allowing interaction among dynamics, radiation and photochemistry. The zonally averaged dynamics are governed by a stream function equation for the residual Eulerian meridional circulation wherein the effects of wave transience and dissipation have been neglected. The resulting circulation is thus driven by diabatic heating and cooling, with Rayleigh friction introduced to balance the momentum budget. The temperature structure is computed from the zonal mean thermodynamic equation, while the appropriate continuity equations are solved to determine the distribution of the various chemical species and families. In the chemical continuity equations, two types of eddy transport processes are present in addition to the transport by the residual Eulerian circulation. Small‐scale disturbances are assumed to produce turbulent mixing which is modeled in terms of horizontal and vertical diffusion coefficients, while steady state planetary waves give rise to fluxes which are expressed in terms of observed wave structure and the photochemical lifetime of the species transported. The circulation, temperature structure, and distribution of chemical constituents obtained with the model are for the most part in satisfactory agreement with observations. In particular, the direct, equator‐to‐pole circulation computed for the stratosphere seems to be capable of explaining the major features of the distribution of trace constituents there, although the effect of the Fickian diffusion included in the model is important in determining the magnitude of gradients.
Slope‐induced errors in radar altimetry over continental ice sheets
Authors: Brenner A. C. , Blndschadler R. A. , Thomas R. H. , Zwally H. J.
Published: February 2008

Ranges obtained by radar altimetry from a satellite to a sloping surface on the earth are not measurements of the surface elevation at the subsatellite point. Instead, the reflecting point is displaced upslope from the subsatellite point causing a 'slope‐induced error' between the true range to the subsatellite point and the indicated range. For the SEASAT 1 altimeter, this range error is nearly 80 m for a 0.8 degree slope. Ice sheet surface slopes are frequently large enough to cause errors of 10 m or more. In addition, undulations in the surface about a mean slope cause pronounced variations in these errors. Altimeter measurements of ranges to modeled irregular surfaces are simulated and two correction schemes are used to reconstruct the modeled surfaces from the simulated data. The results illustrate the fundamental limitations inherent in single‐beam radar altimetry for mapping irregular surfaces. In the simpler two‐dimensional case, for which cross‐track slopes are neglected, a relocation scheme, which constructs a surface consistent with the altimeter ranges, removes 85% of the rms error. The mean error along profiles of about 75 km or longer is usually reduced more than the rms error. An alternate slope correction scheme, which uses the local slope to calculate the expected error, is less effective in the two‐dimensional case. However, over a simulated three‐dimensional surface, where groundtracks are widely spaced and cross‐track slopes are significant, the slope‐correction method must be used in at least the cross‐track direction. The effectiveness of the three‐dimensional correction depends on the relative size of the errors caused by the local slope on surface undulations in comparison to the regional slope.
Monte Carlo simulations for studying the relationship between ocean wave and synthetic aperture radar image spectra
Authors: Alpers Werner
Published: February 2008

A theoretical model previously developed for describing the imaging of monochromatic ocean waves by synthetic aperture radar (SAR) is extended to relate ocean wave spectra to SAR image spectra. Since the SAR response to the moving ocean surface is nonlinear for a large range of ocean wave parameters, this relationship can, in general, not be described by a linear mapping transfer function. SAR image spectra are calculated from given ocean wave spectra by applying Monte Carlo simulation techniques. The computer simulations are performed with varying SAR parameters and for a unidirectional wave field propagating in azimuth direction. Though the model calculations are only one dimensional, they reveal the following basic features of the SAR imaging mechanism: (1) If the nonlinearity of the imaging is sufficiently strong, then the peak of the SAR image spectrum is shifted towards lower azimuthal wave numbers. (2) One parameter suitable for characterizing the degree of nonlinearity is the average velocity bunching parameter
, which for SEASAT‐SAR is given by
, where λm is the dominant wavelength and Hs the significant waveheight in meters, and ϕ the azimuth angle (ϕ = O for azimuthally traveling waves). (3) The amount of the azimuthal shift of the spectral peak depends on c, SAR integration time, and on the width of the ocean wave spectrum. It increases with integration time and spectral width. (4) In case of a fully developed wind sea, shifts of spectral peaks toward lower azimuthal wave numbers become significant for SEASAT‐SAR if
. For
, the relative azimuthal wavenumber shift is of the order of 1/2. If
, the peak of the image spectrum is located near zero wave number and no wave information can be extracted from the SEASAT‐SAR image spectrum.
Large‐and small‐scale spatial evolution of digitally processed ocean wave spectra from SEASAT synthetic aperture radar
Authors: Beal R. C. , Tilley D. G. , Monaldo F. M.
Published: February 2008

Precision digitally processed and corrected synthetic aperture radar (SAR) image spectra along a large portion of SEASAT orbit 1339 (September 28, 1978) have revealed a number of unique potentials, but also some substantial limitations of spaceborne SAR for global ocean wave monitoring. SAR appears to be capable of monitoring the spatially evolving ocean wave number spectrum with high statistical reliability. The large‐scale (few hundred kilometer) spatial evolution of the spectrum is generally consistent with the location (in time and space) of wave‐generating sources, even when multiple wave systems are present. On a more local scale of just a few tens of kilometers, the nearshore wave number spectrum responds to local depth changes but is too noisy to respond reliably to local current changes. The SEASAT SAR was severely restricted in its ability to sense azimuthtraveling (along‐track) waves in high sea states. Azimuth waves corresponding to ocean wavelengths shorter than about 200 m were either undetected or severely attenuated in the higher sea states (Hs≥2 m); azimuth waves shorter than 100 m are not detectable in even the lowest sea states. Moreover, there is a tendency for attenuated wave systems to be shifted toward the range direction. This effect will significantly impede studies of spatial evolution of SEASAT SAR spectra without some additional correction strategy.
The influence of the Antarctic Peninsula on the wind field over the western Weddell Sea
Authors: Parish Thomas R.
Published: February 2008

The Antarctic Peninsula is a formidable barrier to the easterly flow of stable air over the Weddell Sea. The damming up of cold stable air against the peninsula mountains creates a pressure field which provides the necessary dynamic support for strong, mountain‐parallel winds often observed along the east side. Numerical experiments, using a two‐dimensional (x, z) primitive equation model incorporating a cross section of the terrain of the Antarctic Peninsula, are carried out in attempt to simulate the principle features of these barrier winds. Implications of the wind field are discussed.
Uptake of excess CO2 by an outcrop‐diffusion model of the ocean
Authors: Siegenthaler Ulrich
Published: February 2008

A carbon cycle model is presented in which direct ventilation of intermediate and deep ocean waters in high latitudes is taken into account. The 1½‐dimensional ocean model is an extension of a box‐diffusion model including a deep‐sea outcrop at the surface. If both are calibrated in a consistent way, the outcrop‐diffusion ocean takes up more excess CO2 than the box‐diffusion ocean because the outcropping deep water is essentially virgin as to fossil CO2. Two calibration methods are compared, using the distribution either of natural or of bomb‐produced 14C. The latter leads to a higher oceanic uptake of excess CO2 than the former and to a better agreement with the observed atmospheric increase. Long‐term model responses are also discussed.
A general circulation model study of atmospheric carbon monoxide
Authors: Pinto Joseph P. , Yung Yuk L. , Rind David , Russell Gary L. , Lerner Jean A. , Hansen James E. , Hameed Sultan
Published: February 2008

The carbon monoxide cycle is studied by incorporating the known and hypothetical sources and sinks in a tracer model that uses the winds generated by a general circulation model. Photochemical production and loss terms, which depend on OH radical concentrations, are calculated in an interactive fashion. The computed global distribution and seasonal variations of CO are compared with observations to obtain constraints on the distribution and magnitude of the sources and sinks of CO, and on the tropospheric abundance of OH. The simplest model that accounts for available observations requires a low latitude plant source of about 1.3×1015 g yr−1, in addition to sources from incomplete combustion of fossil fuels and oxidation of methane. The globally averaged OH concentration calculated in the model is 7×105 cm−3. Models that calculate globally averaged OH concentrations much lower than our nominal value are not consistent with the observed variability of CO. Such models are also inconsistent with measurements of CO isotopic abundances, which imply the existence of plant sources.
Lidar‐ and balloon‐borne particle counter comparisons following recent volcanic eruptions
Authors: Hofmann D. J. , Rosen J. M. , Reiter R. , Jäger H.
Published: February 2008

Balloon‐borne particle counter measurements at Laramie, Wyoming (41°N) are used to calculate the expected lidar backscatter at 0.694 μm wavelength from July 1979 to February 1982, a period which included at least four detectable perturbations of the stratospheric aerosol layer due to volcanic eruptions. These calculations are compared with lidar measurements conducted at Garmisch‐Partenkirchen (47.5°N) during the same period. While the agreement is generally good using only the main mode in the particle size distribution (radius ∼0.07 μm) during approximately the first 6 months following a major volcanic eruption, a measured secondary mode near 1 μm radius, when included, improves the agreement. Calculations of the expected backscatter at 25–30 km reveal that substantial number of particles diffuse into this high altitude region about 7 months after a major eruption, and these particles should be taken into account when normalizing lidar at these altitudes.
Spectroscopic measurements of carbon monoxide in the stratosphere
Authors: Louisnard N. , Lado‐Bordowsky O.
Published: February 2008

Results obtained from two experiments concerning the repartition of carbon monoxide in the stratosphere are presented and compared to model predictions. Infrared solar absorption spectra were recorded during a balloon flight from Aire‐sur‐Adour, France (about 44°N Latitude), in September 1980. The height profile of the mixing ratio presents a minimum of 8±1 ppb around 22–25 km; it reaches 14±1 ppb at 35 km. A similar experiment was performed in April–May 1980 from an aircraft (Stratoz II mission) between 64°N and 62°S. The integrated vertical amount above 11.5 km is deduced. There is an important variation of this amount with a maximum (4.45×1017 mol cm−2) at low latitude and a minimum (0.90×1017 mol cm−2) at high latitude related to the height of the tropopause. An asymmetric distribution of CO in the two hemispheres can also be observed.
An aerosol and gas sampling apparatus for remote observatory use
Authors: Komhyr W. D.
Published: February 2008

An air sampling apparatus is described which standardizes sampling height at a field station at 10 m or more above ground level and which minimizes loss of particles and destruction and contamination of sampled trace atmospheric gases as air is conducted through the apparatus to various monitoring instruments. Basic design features render the apparatus useful for air sampling under widely varying climate conditions, and at station altitudes ranging from sea level to more than 4 km. Four systems have been built, and have been used sucessfully since 1977 at the NOAA Geophysical Monitoring for Climatic Change program baseline stations at Point Barrow, Alaska; Mauna Loa, Hawaii; American Samoa, South Pacific; and South Pole, Antarctica.
A numerical model of gravity wave breaking and stress in the mesosphere
Authors: Schoeberl Mark R. , Strobel Darrell F. , Apruzese John P.
Published: February 2008

The stresses generated by breaking gravity waves in the mesosphere are calculated with a numerical model of steady vertically propagating gravity waves that includes wavelength dependent radiative dissipation and turbulent viscosity and conduction. The principal findings are (1) waves do not break for |ū ‐c| values ≲20 m s−1as radiative damping prevents wave amplitude growth with altitude for short vertical wavelengths; (2) the downward heat flux due to turbulence of breaking waves and turbulent heating through loss of wave energy could severely affect the global radiative energy balance; and (3) predicted zonal deceleration for steady breaking waves is stronger than required by Apruzese et al. (1982) for the mean circulation. Gravity wave breaking may be an intermittent process; otherwise, gravity wave stresses would produce an adiabatic mesosphere with a zonal mean velocity close to the phase speed of the breaking wave. Diffusive transport of constituents and potential temperature by breaking gravity wave turbulence is shown to be important. In the cases of nitric oxide and atomic oxygen the vertical eddy diffusion coefficients are shown to be sensitive functions of their respective chemical loss rates in the mesosphere and lower thermosphere.
Chlorine nitrate: The sole product of the ClO + NO2 + M recombination
Authors: Margitan James J.
Published: February 2008

A laser operating at 266 nm was used to photolyze the product of the ClO + NO2 + M reaction, and the yield of Cl atoms, measured by resonance fluorescence, was found to be identical to that from equivalent concentrations of ClONO2, strongly suggesting that no other isomers are formed in the recombination reaction. Evidence for isomers is reviewed, and the apparent forward‐and‐reverse‐rate constant discrepancy explained as a probable uncertainty in the thermochemistry.
Simple energy balance model resolving the seasons and the continents: Application to the astronomical theory of the ice ages
Authors: North G. R. , Mengel J. G. , Short D. A.
Published: February 2008

A one‐level seasonal energy balance climate model which has explicit two‐dimensional land‐sea geography is introduced and its properties analyzed. The model distinguishes land from sea surface strictly by the local thermal inertia employed. The transport is governed by a smooth latitude dependent diffusion mechanism. The model's seasonal cycle is solved for, with and without ice feedback. In each case, good agreement with real data is accomplished with minimal tuning of the adjustable parameters. The model sensitivity for small solar constant changes is in agreement with that of other accepted models. However, when the solar constant is lower a few percent, the ice cap grows discontinuously from covering Greenland and vicinity to a size three times larger and mostly into Northern Canada. A similar discontinuous growth occurs when the orbital elements are changed to favor cool summers in the Northern Hemisphere. This discontinuous sensitivity is discussed in the context of the Milankovitch theory of the ice ages, and the associated branch structure is shown to be analogous to the so called ‘small ice cap’ instability known from simpler models. Although the discontinuity in sensitivity is some‐what conjectural, both linear and nonlinear models have their largest sensitivity to orbital parameter changes in the northern portions of the large continents; in the western hemisphere this also corresponds to the ice sheet boundary, suggesting that the land‐sea configuration is crucial to large glacier growth irrespective of moisture budgets. Other experiments and implications are also discussed.
General circulation model experiments on the climatic effects due to a doubling and quadrupling of carbon dioxide concentration
Authors: Washington Warren M. , Meehl Gerald A.
Published: February 2008

A global, spectral atmospheric general circulation model (GCM) with an energy balance ocean formulation, sometimes referred to as a swamp ocean, and realistic geography is run for doubled and quadrupled the present amount of atmospheric carbon dioxide, CO2, with fixed and computed clouds. All experiments are compared to control runs with the present amount of CO2. The experiments use annually averaged solar forcing; thus, there is not a seasonal cycle. It is found that globally averaged surface air temperature in the doubled CO2 experiments increases 1.3°C for the fixed cloud formulation and 1.3°C for the computed cloud case. In the quadrupled CO2 experiment with fixed clouds the surface air temperature increase is 2.7°C, and, in the computed cloud it increases 3.4°C. Warming throughout the troposphere is of the order of 1°–2°C for the doubled CO2 cases, and the stratosphere at 30 km cools up to 6°C. In the quadrupled experiment the maximum tropospheric warming is 4°C, and the model stratospheric cooling is 11°C. An analysis of geographic areas of persistent change in snow cover and soil moisture due to a doubling of CO2 for the fixed cloud case shows a general retreat of the snow line and drying of the soil in tropics and mid‐latitudes with increases of snow depth in the polar regions. These results indicate warming due to increased CO2 is smaller than that found in other studies with swamp‐ocean models coupled to atmospheric GCMs. One possible explanation may be attributed to large differences in the various models used, especially with regard to snow‐sea ice albedo parameterizations.
A two‐dimensional photochemical model of the atmosphere: 1. Chlorocarbon emissions and their effect on stratospheric ozone
Authors: Gidel Louis T. , Crutzen Paul J. , Fishman Jack
Published: February 2008

A two‐dimensional photochemical model is used to examine changes to the ozone layer caused by emissions of CFCl3, CF2Cl2, CH3CCl3 and CCl4. The influence of a possible secular increase in tropospheric methane up to 2% per year was found to be small, although it acts to mask decreases in total ozone caused by the chlorocarbons. Increasing NOx emissions caused by industrialization also tend to mask decreases in total ozone and may have caused total ozone to increase by ∼1%. The model calculated ozone decreases are estimated to be about 3% by 1980. This estimate is higher than estimates by similar models, although we note that CCl4 and CH3CCl3 emissions are included in the model in addition to CFCl3 and CF2Cl2. This is significant because the model indicates that CCl4 has dominated the ozone depletions so far, and knowledge of the historical emission rate of CCl4 to the atmosphere is incomplete. There remain sufficient significant disagreements between theoretical and observed concentrations and variabilities, particularly for odd nitrogen and ClO, to caution against assigning too much confidence in the calculated ozone depletion.
Photochemical reactions of water and carbon monoxide in Earth's primitive atmosphere
Authors: Bar‐Nun Akiva , Chang Sherwood
Published: February 2008

The gas‐phase photolysis of H2O at 1849 Å in the presence of CO yields mainly CO2 and H2 and a variety of organic compounds, including C1−C3 hydrocarbons, alcohols, aldehydes, acetone, and acetic acid. The overall quantum yield for conversion of CO to organic compounds varies between 0.23 and 0.03 as a function of the CO abundance. These results indicate that even if primitive earth's atmosphere initially contained no molecular hydrogen and contained carbon only in the form of CO or a mixture of CO and CO2, the prebiotic environment would have become enriched with a variety of organic compounds produced by photochemical processes.
The isolation of stratospheric temperature change due to the El Chichón volcanic eruption from nonvolcanic signals
Authors: Quiroz Roderick S.
Published: February 2008

To isolate the stratospheric temperature signal caused by the eruption of El Chichón, Mexico (March 28–April 4, 1982) requires consideration of temperature changes of dynamic origin, changes related to the warming of the east equatorial Pacific ocean surface in 1982 (an El Niño event), and changes caused by the quasibiennial oscillation (QBO). Dynamically produced changes in low latitudes associated with sudden warming episodes in the high‐latitude stratosphere from January to April are accounted for, clearing the way for the diagnosis of temperature changes after April. From composites of stratospheric temperature anomalies during past El Niño events, it was determined that temperature variation related to major sea surface temperature (SST) changes would be negligible in summer 1982 but important thereafter. For summer 1982 the remaining diagnostic problem involved estimating the temperature anomaly that should be caused by the QBO and calculating the residual ascribable to the eruption. From a reconstructin of past QBO cycles and detailed inspection of the most recent cycles, as exhibited in station data near the equator and in zonally averaged temperatures at 15°–45°N (30 mbar), estimates are obtained for QBO phase with latitude in 1982 and for temperature anomalies caused by the QBO. Residual anomalies ascribed to the eruption amount to approximately 1.0°–3.0°C between the equator and 35°N. This may be contrasted with total observed 30‐mbar anomaly up to approximately 6°C at stations such as Singapore (1°N). Further work for other altitudes and latitudes is needed, with proper accounting of nonvolcanic signals.
Backscatter and extinction in water clouds
Authors: Pinnick R. G. , Jennings S. G. , Chýlek Petr , Ham Chris , Grandy W. T.
Published: February 2008

An approximate relation between the volume extinction coefficient σe and backscatter coefficient σb of atmospheric cloud at visible and near‐infrared wavelengths is derived. The relation is only weakly dependent on the size distribution of droplets and has the form σe/ σb = (8π/g){1 + k−2/3(〈r4/3〉/〈r2) ‐ δ[k2(〈r4〉/〈r2〉) + k4/3(〈r4/3;〉〈r4〉/〈r2〉〈r2〉)]} where the extinction efficiency is approximated by a complex‐angular‐momentum‐theory result and the parameters g and δ are determined by approximating a running mean of the backscatter gain by G(x) = g(1 + δx2) (x is droplet size parameter and δ ≪ 1), k is the wave number, and 〈rn is the nth moment of the droplet size distribution. To zero order the relation is linear and independent of the droplet size distribution σe = [8π/g(λ)]σb, where g(λ) is a slowly varying function of wavelength. At a wavelength λ = 1.06 μm the relation is σe (km−1) = 18.2 σb (km−1 sr−1). Predictions made with this simple zero‐order approximation are in good agreement (within 50%) with Mie calculations of extinction and backscatter coefficients based on 156 measurements of cloud droplet spectra in cumulus and stratus type clouds. The linear σe ‐ σb; relation is also in agreement with extinction and backscatter measurements made on laboratory‐generated fog droplet distributions. The relation suggests that visible or near‐infrared extinction coefficients in cloud of unknown type could be inferred from lidar backscatter measurements alone, without knowledge of the cloud droplet size spectra, barring complications arising from multiple scattering contributions to the lidar return.
Attenuation of solar irradiance in the stratosphere: Spectrometer measurements between 191 and 207 nm
Authors: Anderson G. P. , Hall L. A.
Published: February 2008

Measurements made by a balloon‐borne, single dispersion spectrometer have been used to investigate the attenuation of solar irradiance in the wavelength region of the O2 Schumann‐Runge bands and the Herzberg continuum. The data cover the altitude range from 28 to 39 km. The fine spectral resolution (0.012 nm) allows transmittance windows in the Schumann‐Runge system to be resolved, facilitating the comparison of their characteristic absorption to model calculations. An atmospherically derived O2 cross section developed in this analysis is significantly lower than the Herzberg continuum values most used in photochemical models.