bluuebunny/crossref_metadata_2025 huggingface dataset:
13C/12C ratio in methane from the flooded Amazon forest
Authors: Tyler Stanley C. , Blake Donald R. , Rowland F. Sherwood
Published: February 2008

Analyses for C1‐C4 hydrocarbon concentrations and the 13C/12C ratio in CH4 were performed on two air samples collected in the Amazon jungle (3.5°S, 59°W) after the nearby release of biogenic gas bubbles. The CH4 concentrations of each sample were greatly enhanced (4100 and 310 ppmv) over the background concentration (1.6 ppmv) for remote locations at that latitude and time. The 13/12C ratio in this biogenic methane is depleted in 13C (−64‰) relative to atmospheric CH4 (−47‰), as is CH4 from almost all other biogenic sources. Because laboratory measurements to date indicate only a very small 13C/12C isotope effect in the reaction of CH4 with HO, an apparent discrepancy remains between the 13C/12C ratios of the known CH4 sources and that of atmospheric CH4. Five other hydrocarbons (C2H6, C2H4, C3H8, i‐C4H10, n‐C4H10) were also found at the 1 to 35 ppbv level in the air sample with 4100 ppmv CH4. These concentrations are not large enough to indicate any major importance for this source in C2‐C4 hydrocarbon budgets on either a global or regional basis.
Theoretical study of the initial products of the atmospheric oxidation of hydrocarbons
Authors: Calvert Jack G. , Madronich Sasha
Published: February 2008

The initial products of the tropospheric oxidation of a representative mixture of hydrocarbons have been studied theoretically, using a detailed chemical mechanism involving 26 alkanes (C1–C8), alkenes (ethylene, propylene), aromatic hydrocarbons (benzene, toluene, o‐, m‐, and p‐xylenes), and two terpenes (isoprene, α‐pinene). For an NOx‐rich atmosphere the oxidation of the alkanes in the mixture leads to three main classes of initial products: aldehydes (34%), ketones (45%), and alkyl nitrates (21%). Both the γ‐hydroxy‐aldehydes (19%) and the γ‐hydroxy‐ketones (19% of all alkane initial products) are major products. For NOx‐free conditions the major products of the alkane oxidation are expected to be the alkyl hydroperoxides. For NOx‐rich conditions the aldehydes dominate the alkene oxidation products (80%), with smaller amounts of α‐hydroxy‐carbonyl compounds (9%) and organic acids (4%). The major products of the aromatic hydrocarbons in the mixture are α‐dicarbonyls (24%), unsaturated γ‐ dicarbonyls (22%), phenols (<49%), aromatic aldehydes (3%), and aromatic nitrates (2%). The expected product distribution and lifetime data suggest that each class of hydrocarbon has certain unique products which should serve as useful indicators of the history of an aged air mass. It is concluded that the alkyl nitrates and the γ‐hydroxy‐alkyl nitrates may contribute to the large, and as yet unidentified, fraction of the active nitrogen species noted in NOy determinations in the troposphere by Fahey et al. (1986).
A study of the radiative effects of enhanced atmospheric CO2 and CH4 on early Earth surface temperatures
Authors: Kiehl J. T. , Dickinson R. E.
Published: February 2008

Large concentrations of atmospheric CO2 in the atmosphere of the early earth have been proposed as a possible explanation of the apparent absence of frozen earth in spite of a faint early sun. However, the most thorough treatments of this question, by Owen et al. (1979) and Kasting et al. (1984), apparently disagree as to the warming effects of large amounts of CO2. We recalculate the evolution of surface temperature over the last 4.25 billion year time period, using the same scenario for CO2 partial pressures and solar constant as employed by the previous authors. We find good agreement with Kasting et al. (1984) and also explain why the results of Owen et al. are at variance with our findings and those of Kasting et al. Using the concept of direct radiative forcing, we present analytic relations between the solar luminosity and CO2 mixing ratio required to maintain the troposphere close to its present thermal structure. As a by‐product, we present new broadband parameterizations for the 961 and 1064 cm−1 CO2 bands that can be used in climate models. We also consider the direct radiative forcing of large amounts of CH4, or changes in model clouds, and discuss how these might reduce the CO2 mixing ratio required to balance the faint early sun.
The NOAA/GMCC continuous CO2 record at the South Pole, 1975–1982
Authors: Gillette Dale A. , Komhyr Walter D. , Waterman Lee S. , Steele L. Paul , Gammon Richard H.
Published: February 2008

Hourly carbon dioxide concentrations at the south pole were obtained by nondispersive infrared analyzers for the years 1975–1978 and 1980–1982. A spectral analysis of the ambient CO2 variability showed very little power for periods shorter than 5 days. Our data showed good agreement with other data sets for the range of the annual fluctuation from 1977 to 1982 and disagreements for 1976. The estimated annual CO2 increase (about 0.6 to 2 ppm yr−1) and ranges of seasonal fluctuation were insensitive to the data selection methods used. After 1979, seasonal fluctuations apparently decreased.
The stratosphere: Climatologies of the radiative heating and cooling rates and the diabatically diagnosed net circulation fields
Authors: Callis Linwood B. , Boughner Robert E. , Lambeth James D.
Published: February 2008

Contemporary solar and infrared radiative codes have been used with satellite derived distributions of ozone, water vapor, and temperature to calculate the stratospheric solar, infrared, and net radiative heating on a monthly basis. Heating/cooling rates have been Calculated from pole to pole and from 13 to 61 km for each of 12 months. Vertical resolution is 1.5 km. Results are interpolated to surfaces of constant potential temperature, and divergence‐free, zonally averaged, advective fields are diagnosed using the calculated diabatic heating (net radiative heating). Associated stream functions are also derived. Based upon these advective fields, trajectory studies have been carried out in the meridional plane and used to elucidate further the stratospheric transport of inert tracers. Analysis of the presently diagnosed advective fields suggests the following: (1) Entry into the mid to upper stratosphere of tropospheric air is principally from a latitude region of ±10° at the equatorial tropopause. Smaller contributions to the stratosphere come from the polar mesosphere. (2) At latitudes poleward of ±15°, tracers transported from the troposphere into the stratosphere are subsequently transported toward the pole (with little ascending motion) and then downward and out of the stratosphere at the higher latitudes. (3) The nearly continuous presence of cells of net cooling in the lower stratospheric polar regions are important in establishing these regions as continuous vents for polar stratospheric air. (4) Based upon these advective fields, residence times for stratospheric air with given entry points are as follows: for equatorial entry, 3–4 years; for entry from the polar mesosphere, 1–1.5 years; and for entry from the troposphere at extratropical latitudes, ≈1 year. Using heating and advection fields derived from Limb Infrared Monitor of the Stratosphere (LIMS) data, an approximate measure of the interannual variability of the diabatic circulation is obtained. Ramifications of these findings are discussed. The heating rates, the derived advective fields, and the data base used in their calculation are available from the authors upon request.
Rate coefficient for the gas phase reaction of NaOH with CO2
Authors: Ager Joel W. , Howard Carleton J.
Published: February 2008

The third‐order rate constants for NaOH + CO2 + M were measured in a flow tube at 298 K. The rate constants for N2 and N2O buffer gases are (1.3±0.3) × 10−28 and (2.9±0.6) × 10−28 cm6 molecule−2 s−1, respectively. We expect the product of this reaction, NaHCO3, to be relatively stable with respect to 0 atom reaction and photolysis and to be a dominant reservoir species for Na in the mesosphere. The association reaction of NaOH with CO2 is at least 40 times faster than NaOH + HCl at all altitudes below the Na layer. Na species will not affect stratospheric ClOx and O3 chemistry.
On Taylor's hypothesis and dissipation in rainfall
Authors: Gupta Vijay K. , Waymire Ed
Published: February 2008

The role of dissipation in the cutoff in Taylor's hypothesis for rainfall correlations in space‐time is generalized to a wide class of possible stochastic rainfall models. Some important implications of this generalization are discussed for the development of statistical rainfall theories, particularly as they pertain to scaling.
Photodissociation in the atmosphere: 1. Actinic flux and the effects of ground reflections and clouds
Authors: Madronich Sasha
Published: February 2008

The actinic flux must be distinguished from other radiometric quantities such as the irradiance. This distinction shows that (1) a fraction of the recent atmospheric chemistry literature contains improperly calculated rates of photodissociation, and (2) photodissociation rate coefficients inside clouds, and particularly inside cloud droplets, can frequently exceed the clear‐sky values, in contrast to current usage in cloud chemistry models. Both of these findings are traceable to the ∼2 cos θ factor incurred in the actinic flux (but not in the irradiance) when the solar beam is scattered and diffused into nearly isotropic light.
Gaseous deposition to snow: 2. Physical‐chemical model for SO2 deposition
Authors: Bales Roger C. , Valdez Marc P. , Dawson George A.
Published: February 2008

A diffusion/reaction model of SO2 uptake by snow containing liquid water is used to examine the snowpack processes controlling accumulation of dissolved S(IV) and S(VI). Surface deposition velocity vd (defined as overall accumulation rate divided by surface SO2 concentration) depends on the amount of liquid water in the snow, the time scale considered, the rate of S(IV) to S(VI) conversion in the aqueous phase, and the SO2 concentration. In the absence of any oxidation, vd for dense snow (specific gravity 0.4) with a moderate liquid water mass fraction (Xm = 0.01) and SO2 concentration of 20 ppbv (parts per billion by volume) is calculated to be 0.026 cm s−1 after 6 hours. Deposition velocity increases by a factor of 3.2 for each tenfold increase in Xm and by a factor of 2.5–3.2 for each tenfold decrease in time. SO2 penetration into the snowpack is about 5 cm for the 6‐hour case. In the presence of air containing 30 ppbv ozone and otherwise identical conditions, 80% of the accumulated sulfur is as S(VI), and the calculated vd is 0.036 cm−1. A further tenfold increase in ozone concentration gives only a 70% increase in vd. A similar dependence is calculated for oxygen (catalyzed by Fe(III)) as oxidant, but that for hydrogen peroxide is much stronger and almost linear. A tenfold increase in SO2 concentration (with ozone at 30 ppb) results in a 2.3‐fold decrease in vd. Wet snow with a liquid water mass fraction of about 0.1 gives a deposition velocity at 20 ppb SO2 of 0.12 cm s−1, with a penetration of only 2 cm. Calculated and observed uptakes of SO2 by snow are in good agreement.
Equivalent displacement height and vertical eddy diffusion in the stratosphere
Authors: Ehhalt D. H.
Published: February 2008

It is argued that the equivalent displacement height, Δ, is related to the one‐dimensional vertical eddy diffusion coefficient via Kz = Δ2/τ. The required relaxation time, τ, is shown to be about 17 days. The resulting expression for Kz is compared to the ones derived by Mahlman et al. (1986) and Holton (1986).
Atmospheric selenium: Geographical distribution and ocean to atmosphere flux in the Pacific
Authors: Mosher Byard W. , Duce Robert A. , Prospero Joseph M. , Savoie Dennis L.
Published: February 2008

Approximately 700 weekly aerosol samples from seven island sites in the North Pacific have been analyzed for their selenium content. A much more limited set of selenium aerosol analysis is also presented for two South Pacific island sites. Selenium concentrations (0.25±0.16 ng m−3) in the high‐latitude North Pacific atmosphere were a factor of 2 greater and much more variable than those found at mid‐North Pacific basin sites. Aerosol concentrations at five sites in the mid‐ and southwestern North Pacific were uniformly low, with mean concentrations of 0.10–0.13 ng Se m−3. Seasonal trends in the data were not evident at these locations. Near the equator, in the productive upwelling regime of the central North Pacific, mean particulate selenium concentrations were a factor of 3–4 greater than those observed in oligotrophic midocean regions. Effects of the 1982–1983 El Niño Southern Oscillation were also apparent in the aerosol record in this region. Consideration of aerosol selenium, nitrate, and non‐sea‐salt sulfate data from the Pacific suggests that source functions of aerosol selenium and excess sulfate may be similar, while removal mechanisms of selenium and nitrate may be analogous. The geographical distribution of aerosol selenium appears to be more closely related to primary productivity of the surrounding waters rather than to transport of continentally derived material into the central ocean basin. We estimate an ocean‐to‐atmosphere vapor phase selenium flux of 5–8×109 g Se yr−1. The anomalous enrichment of aerosol selenium which is observed in the marine atmosphere may be explained by the gas‐to‐particle conversion of this naturally produced vapor phase.
A doubled CO2 climate sensitivity experiment with a global climate model including a simple ocean
Authors: Wilson C. A. , Mitchell J. F. B.
Published: February 2008

The sensitivity of a global climate model to increased atmospheric CO2 concentrations is presented, assessed, and compared with earlier studies. The ocean is represented by a 50‐m slab in which the heat convergence due to oceanic dynamics is prescribed, producing an accurate simulation of sea surface temperatures, sea‐ice extents, and associated features in the control simulation. Changes in surface temperature are qualitatively similar to those found in earlier studies using models with similar or lower horizontal resolution, although the global warming is slightly larger. The simulated changes in hydrology agree broadly with those in studies made with higher horizontal resolution and prescribed changes in sea surface temperatures and include a drying over the northern mid‐latitude continents. Many of the discrepancies in the responses of different models can be traced to differences in the simulations of present‐day climate. The choice of convective parametrization appears to influence the sensitivity of the simulated response in the tropics.
Global atmospheric mass, surface pressure, and water vapor variations
Authors: Trenberth Kevin E. , Christy Johan R. , Olson Jerry G.
Published: February 2008

Variations in the hydrological cycle and the water vapor content of the atmosphere form a vital part of the “greenhouse” feedback mechanism that can substantially enhance perturbations in the atmosphere arising from changes in forcing, such as those associated with increases in the carbon dioxide content of the atmosphere. An analysis is therefore made of the mean annual cycle, interannual variability and trends in global‐scale water vapor content of the atmosphere for December 1978 through December 1985, using global analyses from the European Centre for Medium Range Weather Forecasts. Since the variations in total atmospheric mass are almost entirely due to water vapor, two entirely independent global measures of the water vapor content can be compared. These are the total surface pressure due to water vapor from humidity analyses and the total surface pressure itself. For the mean annual cycle these show excellent agreement, and the analyses are therefore compatible with the constraint that the total mass of dry air is conserved. However, it appears that both the interannual variability and trends in water vapor are sufficiently small that they are lost in the noise level of the data. A new estimate of the total mass of the atmosphere is 5.1361×1018 kg for the annual mean, corresponding to a mean surface pressure of 984.43 mbar. It ranges from 5.1352×1018 kg in January to 5.1371×1018 kg in July, owing to the annual cycle in global water vapor which has an amplitude of 1.0×1015 kg (0.2 mbar). The total mass of dry air is estimated to be 5.123×1018 kg (or 981.9 mbar). Also presented is the partitioning of the mass for both the total and the water vapor into the contributions from each hemisphere and as a function of latitude. Mean annual surface pressures in the northern and southern hemispheres are found to be 981.92 and 986.93 mbar, respectively. Monthly mean hemispheric fluctuations in surface pressures of ±1 mbar are not uncommon and tend to be reflected by opposite anomalies in the other hemisphere (consistent with conservation of mass), but the residual in the global monthly mean is of the order of 0.1 mbar. Since this is greater than the magnitude of the possible signal in water vapor surface pressure, the available evidence indicates that the analyzed global monthly anomalies are mostly noise.
Tropospheric nitric oxide measurements over the Amazon Basin
Authors: Torres A. L. , Buchan H.
Published: February 2008

Horizontal and vertical distributions of nitric oxide (NO) were measured over the Amazon Basin during NASA's Global Tropospheric Experiment (GTE) Amazon Boundary Layer Experiment (ABLE 2A) mission in July–August 1985. During transit flights between the Virginia coast and Manaus, Brazil, NO mixing ratios were 12–15 parts per trillion by volume (pptv) at 5 km altitude. Values up to 200 pptv were observed in electrically active clouds. During longitudinal surveys over the Amazon region, NO mixing ratios in the lower planetary boundary layer decreased from 25–60 pptv over the central basin to 10–12 pptv in coastal regions. In the convective cloud layer or free troposphere, NO mixing ratios averaged 13 pptv in regions not influenced by biomass burning. No longitudinal trend above the mixed layer could be detected. A steep negative gradient with increasing altitude was noted within the mixed layer before midday. Mixing ratios decreased from 60 pptv at 0.2 km to about 15 pptv at the top of the mixed layer (1 km). No further change in mixing ratio with altitude through the convective cloud layer and lower edge of the free troposphere could be detected at this time. By midday, growth of the mixed layer height and enhanced mixing reduced the gradient, and evidence for mixing of NO into the convective cloud layer was noted.
Composition and sources of aerosols from the Amazon Basin
Authors: Artaxo Paulo , Storms Hedwig , Bruynseels Frank , Van Grieken René , Maenhaut Willy
Published: February 2008

Aerosols were sampled in the Amazon Basin, as part of the Global Tropospheric Experiment (GTE), during the Amazon Boundary Layer Experiment (ABLE 2A) in July–August 1985. Fine‐ and coarse‐particle fractions were analyzed for 22 elements by particle‐induced X ray emission. Gravimetric mass, black carbon, sulfate, and nitrate concentrations were also determined. Morphological and trace element measurements of individual particles were carried out by automated electron probe X ray microanalysis. Various receptor models, including multivariate methods and a chemical mass balance model, were employed in the interpretation of the bulk trace element concentrations. Three factors explained over 85% of the variability of fine‐ and coarse‐mode variables. On the basis of the elemental composition of the factors, two could be identified as plant related, and the third was a soil dust component. Of the coarse‐mode aerosol mass concentration (of 7.6±1.6 μg/m3), 62% could be attributed to aerosols released by the vegetation and 11% to soil dust. In the fine mode, soil dust accounted for less than 10% of the measured mass concentration (of 6.8±3.9 μg/m3). The variables related to the plant component were K, P, S, Ca, Mg, Cl, Rb, and the gravimetric mass. The elemental profile of the plant component resembled the bulk plant composition. By single‐particle analysis coupled with hierarchical cluster analysis, six to nine different biogenic‐related particle groups could be identified in the fine‐ and coarse‐aerosol modes. Almost all particle types consisted predominantly of carbonaceous material, with trace amounts of K, S, Ca, P, Cl, and Na. Only one group, comprising less than 11% of the total number of particles, consisted of soil dust–related aerosol.
Two years of continuous measurements of turbulence parameters in the upper mesosphere and lower thermosphere made with a 2‐MHz radar
Authors: Hocking W. K.
Published: February 2008

Since February 1985, the 2‐MHz narrow beam radar near Adelaide, Australia, has been used to measure the short‐term root‐mean‐square fluctuating velocities of radio wave scatterers in the altitude range 80–100 km. Data have been recorded about every 2 to 3 hours. This is in addition to the routine measurement of winds in the region between 60 and 100 km altitude. Under certain assumptions, these fluctuating velocities can then be converted to turbulent energy dissipation rates and eddy diffusion coefficients. These measurements are presented, and their interpretation as turbulence is discussed. The possibility of contamination from high frequency, short wavelength gravity waves is considered and a correction procedure to allow for such contamination is developed. It is concluded that the corrected measurements represent a good indication of turbulence activity. Between 84 and 92 km, the turbulence intensities were approximately constant with increasing height, but between 80 and 84 km turbulence was relatively weak. Seasonal variations are discussed, and important interannual differences between 1985 and 1986 are noted.
Mean winds and tides in the 85‐ to 110‐km region over central Europe in 1983–1986
Authors: Schminder Rudolf , Kuerschner Dierk
Published: February 2008

On the basis of low‐frequency D1 wind measurements, height‐time cross sections for mean winds and semidiurnal tidal motions were constructed as averages for the years 1983–1986. Very good agreement was found with the results of other authors, some of which were available in a similar type of representation. The method discussed is of sufficient accuracy and reliability, with a favorable cost‐benefit ratio. It is suitable for continuous low‐cost monitoring of wind fields in the upper mesosphere/lower thermosphere region at medium latitudes.
Measurements of atmospheric methyl bromide and bromoform
Authors: Cicerone Ralph J. , Heidt Leroy E. , Pollock Walter H.
Published: February 2008

We have measured gaseous methyl bromide (CH3Br) and bromoform (CHBr3) in air samples that were gathered approximately weekly from five ground‐level sites: Point Barrow, Alaska; Mauna Loa Observatory and Cape Kumukahi, Hawaii; Matatula, Samoa; and Kaitorete Spit, New Zealand. Approximately 750 samples have been analyzed for CH3Br between January 1985 and October 1987 and 990 samples have been analyzed for CHBr3 between early 1984 and September 1987, all by gas chromatography/mass spectrometry. Methyl bromide concentrations are typically 10–11 parts per trillion (ppt) by volume; there are no clear indications of temporal increases. Bromoform concentrations are typically 2–3 ppt, but large seasonal variations are seen at Point Barrow.
An experimental test of the “transmission‐line model” of electromagnetic radiation from triggered lightning return strokes
Authors: Willett J. C. , Idone V. P. , Orville R. E. , Leteinturier C. , Eybert‐Berard A. , Barret L. , Krider E. P.
Published: February 2008

The “transmission‐line” model of return‐stroke radiation, proposed by Uman and McLain (1970) and invoked frequently thereafter to deduce peak currents from remote fields or to estimate propagation velocities from measured fields and currents, has never received a thorough experimental test. During the summer of 1985 at the Kennedy Space Center in Florida, we were able to measure peak currents (with a coaxial shunt), two‐dimensional average propagation speeds (with a high‐speed streak camera), and electric field waveforms (at 5.15‐km range) for a number of subsequent return strokes in rocket‐triggered lightning flashes. Because of the temporal ambiguity on the streak‐camera films, it has not been possible to identify individual velocity measurements with particular strokes for which current and field data are available. Three multistroke flashes, however, each yielded a tight cluster of velocity measurements and a group of peak field to peak current ratios, though not necessarily for the same strokes. A further six flashes provided more current and field measurements for which no velocity information was obtained, and velocity measurements only are available for still other flashes. It is shown that these data indicate reasonable agreement between the propagation speeds measured with the streak camera and those deduced from the transmission‐line model. The previously observed difference between current and radiation‐field waveforms suggests a modification of the model, involving two wave fronts traveling upward and downward away from a junction point a short distance above the ground, which substantially improves the agreement between measured and inferred propagation speeds.
New tropospheric OH measurements
Authors: Platt U. , Rateike M. , Junkermann W. , Rudolph J. , Ehhalt D. H.
Published: February 2008

New field measurements of atmospheric OH radicals by laser long‐path absorption spectroscopy are reported: In the Black Forest, diurnal profiles of OH radical concentrations ranging up to 8.7×106 cm−3 have been observed during June 1984. Simultaneous measurements of other trace gases, photolysis frequencies, and meteorologic parameters were also made to allow comparison of observed OH levels with model calculations.
Atmospheric ozone at South Pole, Antarctica, in 1986
Authors: Komhyr W. D. , Oltmans S. J. , Grass R. D.
Published: February 2008

Vertical‐profile ozone distributions and variations, as well as the annual course of total ozone, are described for South Pole, Antarctica, from observations made throughout 1986 with electrochemical concentration cell (ECC) ozonesondes and a Dobson spectrophotometer. Ozone decrease in the stratosphere in September and October months was the highlight of the measurements. From mid‐August to October 7, total ozone decreased by about 40%, with the bulk of the decrease occurring between 12 and 21 km. Within this region the maximum rate of ozone decrease, with an exponential decay half‐life of 11 days, was observed between September 20 and October 15, when column ozone and ozone volume mixing ratio at 16±1 km decreased by 78% and column ozone between 12 and 21 km decreased by 50%. This time interval was characterized by virtual cessation of ozone flux into the stratosphere above South Pole that might have resulted either from movement of the polar vortex or from ozone advection from lower latitudes. In contrast, ECC ozonesonde data obtained in 1971 show ozone to have arrived at South Pole above 30 mbar in mid‐September and above 100 mbar in late September, 6 and 3 weeks, respectively, earlier than it did in 1986. Supporting evidence for a temporal change in the timing of ozone transport to Antarctica by atmospheric circulation comes from 1974–1986 surface ozone observations at South Pole, which show a negative surface ozone growth rate during summer months, a positive growth rate during winter months, and an increase in the amplitude of the annual cycle by a factor of 2. A correspondence is shown between El Niño‐related highs in sea surface temperature anomalies in the equatorial Pacific Ocean and lows in October–December total ozone averages that were observed at South Pole in the 1960s and 1970s. Such ozone lows occurred during years of increased circumpolar vortex stability, late stratospheric warming, and late ozone arrival in Antarctica. It is suggested that the 1982–1983 El Niño, which was of unprecedented intensity, similarly affected the transport of ozone to Antarctica, thereby contributing to the observed springtime ozone decrease. The transport of air parcels from 50°–60°S latitude into the tropopause and low stratosphere region of Antarctica, as suggested by 10‐day, isobaric back trajectory analyses, may also contribute to the Antarctica springtime ozone decrease and warrants further investigation.
The doubled CO2 climate and the sensitivity of the modeled hydrologic cycle
Authors: Rind D.
Published: February 2008

Four doubled CO2 experiments with the GISS general circulation model are compared to investigate the consistency of changes in water availability over the United States. The experiments compare the influence of model sensitivity, model resolution, and the sea surface temperature gradient. The results show that the general mid‐latitude drying over land is dependent upon the degree of mid‐latitude eddy energy decrease, and thus the degree of high‐latitude temperature change amplification. There is a general tendency in the experiments for the northern and western United States to become wetter, while the southern and eastern portions dry. However, there is much variability from run to run, with different regions showing different degrees of sensitivity to the parameters tested. The results for the western United States depend most on model resolution; those for the central United States on the sea surface temperature gradient and the degree of mid‐latitude ocean warming; and those for the eastern United States on model sensitivity. The changes in particular seasons depend on changes in other seasons, and will therefore be sensitive to the realism of the ground hydrology parameterization.
Two‐dimensional distribution of light hydrocarbons: Results from the STRATOZ III experiment
Authors: Rudolph J.
Published: February 2008

During the STRATOZ III flights in June 1984, about 120 whole‐air samples were collected and analyzed later on in the laboratory for several atmospheric trace components, including light hydro‐carbons. The STRATOZ III mission consisted of 21 flight segments and covered a latitude range from 70°N to 60°S and altitudes up to 12 km. The results of these measurements were used to construct latitude‐altitude profiles in the form of isolines for ethane, ethene, acetylene, propane, propene, n‐butane, isobutane, n‐pentane, and isopentane. These results are compared with the latitudinal cross sections obtained during a previous, very similar flight mission (STRATOZ II) in May–June 1980. Also, the few published latitudinal or vertical profiles for these nonmethane hydrocarbons (NMHCs) are used for a comparison. The two‐dimensional distributions for the longer‐lived NMHCs, especially ethane and to some extent also propane and acetylene, are reasonably representative, even on a global scale. The high variability of the short‐lived NMHCs, the C4 and C5 alkanes, and the light alkenes, prevents the determination of representative two‐dimensional distributions for these species. The distributions of these short‐lived compounds give at best an extremely rough idea on the distributions and should in general be considered as descriptions of a given momentary situation. These latitude‐altitude profiles indicate the existence of fast mechanisms for vertical mixing in the troposphere. The observation of high mixing ratios of short‐lived hydrocarbons in the middle and upper troposphere proves the existence of vertical mixing processes with a time scale comparable to, or even shorter than, the atmospheric lifetime of these reactive NMHCs. As a consequence, there exist several regions, even above the boundary layer, with NMHC mixing ratios high enough to make them important participants in the atmospheric photochemical reaction cycles.
Shape and optical properties of aerosols formed by photolysis of acetylene, ethylene, and hydrogen cyanide
Authors: Bar‐Nun A. , Kleinfeld I. , Ganor E.
Published: February 2008

The shapes and sizes of photochemically produced aerosol particles of polyacetylene, polyethylene, and polyhydrogen cyanide were studied experimentally. All of the single particles were found to be perfectly spherical and semiliquid. However, they aggregate readily, with a sticking coefficient near unity, to form nonspherical particles, which could give rise to the observed polarization from Titan's and Jupiter's upper haze layers. The absorbance of polyacetylene was remeasured and corrected, and it is now much closer to that of polyethylene. The measured real and imaginary indices of refraction of the two materials make them both suitable material for Titan's and Jupiter's upper haze layers. However, the larger abundance and higher rate of polymerization of acetylene would make it the dominant aerosol‐forming material in both atmospheres.
Smoke optical depths: Magnitude, variability, and wavelength dependence
Authors: Pueschel R. F. , Livingston J. M. , Russell P. B. , Colburn D. A. , Ackerman T. P. , Allen D. A. , Zak B. D. , Einfeld W.
Published: February 2008

The Ames airborne, autotracking sunphotometer has been operated aboard a Sandia Laboratories research aircraft to measure magnitudes, temporal/spatial variabilities, and wavelength dependence of optical depths in the near‐ultraviolet to near‐infrared spectrum of smoke from two forest fires and one jet fuel fire and of background air. The results were corrected for Rayleigh scattering and for estimated absorption by ozone and nitrogen dioxide. Characteristic differences in the aerosol optical depths of background atmospheres and of different types of smokes are the following: (1) the magnitude and wavelength dependence of “background” optical depths vary with the geographic location at which the measurements are performed; (2) the wavelength dependence of smoke optical depths depends on the fuels that feed the fires and on the residence time of the smoke cloud in the atmosphere. In general, the jet fuel smoke optical depths tended to be less wavelength dependent (near‐ultraviolet to near‐infrared) than background aerosol optical depths. Forest fire smoke optical depths showed a wide range of wavelength dependences, including incidents of wavelength‐independent extinction.
Trends in atmospheric ozone: Conflicts between models and SBUV data
Authors: Rusch D. W. , Clancy R. T.
Published: February 2008

Model calculations of ozone trends in the 1982–1986 time period show that interannual stratospheric temperature variations over that period dominate over changes in minor constituents, including Clx, in producing trends in ozone. Estimates for upper limits to changes in solar flux over the declining part of the solar cycle and estimates for maximum increases in Clx lead to similar model decreases in upper stratospheric ozone, although the calculated trends from each are less than 1%/yr. Model calculations suggest that long‐term increases in Clx may produce decreases in the relative amplitude of the annual variation of ozone near 1.0 mbar that are nearly twice the secular decreases in ozone. However, trends in temperature over the period 1982–1986 lead to predicted decreases in the seasonal amplitude of ozone of up to 10%/yr, based upon National Meteorological Center (NMC) observations of upper stratospheric temperatures. The secular and seasonal ozone trends derived from SBUV data for the 1982–1986 time period exhibit poor agreement with model predictions. SBUV data indicate secular trends in ozone which are are negative and larger, in an absolute sense, than the largest model trends by a factor of 2 or more, indicating problems with the SBUV data or the model ozone chemistry. SBUV data also exhibit significantly smaller changes in the amplitude of the annual variation of ozone than the models which include NMC temperatures. At least part of this disagreement may be related to temperature‐correlated variations in photochemistry which are not included in the model, such as changes in water vapor or other minor constituent densities. Future efforts to determine ozone trends from satellite measurements should include monitoring of ozone, temperature, and possibly water vapor in the atmospheric pressure region from 10 to 0.1 mbar.
Radiation transfer in plant canopies: Scattering of solar radiation and canopy reflectance
Authors: Verstraete Michel M.
Published: February 2008

The one‐dimensional vertical model of radiation transfer in a plant canopy described by Verstraete (1987) is extended to account for the transfer of diffuse radiation. This improved model computes the absorption and scattering of both visible and near‐infrared radiation in a multilayer canopy as a function of solar position and leaf orientation distribution. Multiple scattering is allowed, and the spectral reflectance of the vegetation stand is predicted. The results of the model are compared to those of other models and actual observations.
Atmospheric heat budgets of the polar regions
Authors: Nakamura Noboru , Oort Abraham H.
Published: February 2008

The energy budget and its annual variation are studied for the polar regions of the atmosphere. Composite satellite and rawinsonde data are used to compute the rate of storage of energy in the atmosphere, the net radiation flux at the top of the atmosphere, and the energy fluxes across 70°N and 70°S, while the energy flux across the Earth's surface is estimated as a residual. Data produced by a general circulation model are used to obtain plausible estimates of the energy flux across 70°S, where direct estimates tend to be poor. We find that the heat exchange between the atmosphere and the ocean‐cryosphere system plays a much larger role in the Arctic than in the Antarctic polar cap. When the polar caps are extended from 70° to 60° latitude, both the land‐sea distributions and the different terms balancing the energy budgets become more comparable between the two regions.
Uptake of COS by growing vegetation: A major tropospheric sink
Authors: Goldan Paul D. , Fall Ray , Kuster William C. , Fehsenfeld Fred C.
Published: February 2008

Laboratory measurements of the uptake of COS by soybeans, corn, wheat, and alfalfa under conditions of controlled illumination, temperature, and CO2 concentration, and at COS concentrations spanning those typically found in the troposphere (∼500 parts per trillion by volume), indicate that the major uptake pathway is through open stomata. Similarities between the uptake resistances observed for COS and CO2 provide a means of estimating global COS uptake from estimates of global terrestrial primary plant productivity. With an estimated annual plant uptake of 0.2–0.6 Tg COS (Tg = 1012 g), this appears to be the largest global sink for this major tropospheric sulfur reservoir species. With this vegetative sink included, estimated known sources and sinks appear to be in approximate balance.
Viewing zenith angle dependence of cloudiness determined from coincident GOES East and GOES West data
Authors: Minnis Patrick
Published: February 2008

The dependence of observed cloudiness on the satellite or viewing zenith angle (VZA) is examined, using a combination of two cloud amount data sets derived from nearly simultaneous, collocated Geostationary Operational Environmental Satellite (GOES) West and GOES East radiances over the Pacific Ocean during May 1979 and July 1983. A third data set, GOES Prime, is used to estimate the amount of cloud variation due to changes in sensor resolution with VZA. The data are analyzed for single‐layer and total cloudiness, as derived with a hybrid bispectral threshold method. The frequencies of occurrence for low, middle, and high clouds, 96%, 47%, and 28%, respectively, are typical of oceanic cloud populations. Cloud fractions increased with increasing VZA for almost all cases. Low clouds showed the greatest increases for small cloud amounts around 0.1, while the greatest increases for high clouds were found for cloud amounts around 0.5. Midlevel clouds showed only a slight dependence on VZA. Total cloudiness increased the most, reflecting its predominantly low‐cloud composition. Uncertainties in retrieved cloud fraction also increase with the VZA. Resolution changes with VZA were estimated to cause up to 28% of the increase in cloudiness for certain low‐cloud amounts. Very little of the high‐cloud increases were the result of resolution changes. Simple geometrical formulas were used to model the results. A single‐layer cumulus model was found to be the best fit to the layer cloud data. A formulation combining the single‐layer models was used to describe the variation of total cloud cover with VZA. The regression fit of these data to the multilayer model reduced the mean bias errors due to VZA effects from ≈0.058 to ≈0.004. It is concluded that the effects of the VZA should be incorporated in the construction of satellite‐derived climatologies and other Earth‐observing applications.
Climatology of nitric oxide in the upper stratosphere, mesosphere, and thermosphere: 1979 through 1986
Authors: McPeters R. D.
Published: February 2008

Spectral scan data from the solar backscattered ultraviolet (SBUV) instrument on Nimbus 7 for the wavelength range 200–400 nm have been analyzed to determine the strengths of several of the nitric oxide (NO) gamma band fluorescence features as a function of time and of latitude. The integrated column amount of nitric oxide above an altitude of approximately 45–50 km is inferred from analysis of the strengths of the (10), (01), and (02) nitric oxide gamma bands. Analysis shows that there are about 5 – 6 × 1014 molecules cm−2 of nitric oxide cumulative above 48 km over a wide range of latitudes, increasing sharply near the winter terminator by about a factor of 3 to 12 – 15 × 1014 molecules cm−2. Between 1979 and 1986, column NO near the equator decreased by about a factor of 2, from 6.4 × 1014 molecules cm−2 to 3.3 × 1014 molecules cm−2. The time dependence of the decrease correlates well with solar activity, following the decline in solar activity from solar maximum in 1979 to solar minimum in 1985–1986. At middle and high latitudes, NO appears to have reached a maximum in 1982–1983, a few years after the solar cycle maximum, and has decreased since, but the magnitude of the trend is smaller.
European validation of SAGE II ozone profiles
Authors: Attmannspacher W. , de la Noé J. , de Muer D. , Lenoble J. , Mégie G. , Pelon J. , Pruvost P. , Reiter R.
Published: February 2008

During The European Correlative Experiment Program for SAGE II data validation, described by Lenoble (this issue), ozonesonde profiles from several stations were compared with SAGE II profiles. The agreement is always within 10% or better between 20 and 30 km, and it remains acceptable down to 12 km, especially when the two profile locations are close. For higher altitudes, microwave profiles were used, and they showed an agreement between 5 and 10% with SAGE II data between 35 and 60 km.
Atmospheric carbon dioxide at Mauna Loa Observatory: 1. NOAA global monitoring for climatic change measurements with a nondispersive infrared analyzer, 1974–1985
Authors: Komhyr W. D. , Harris T. B. , Waterman L. S. , Chin J. F. S. , Thoning K. W.
Published: February 2008

Atmospheric CO2 measurements made with a nondispersive infrared analyzer during 1974–1985 at Mauna Loa Observatory, Hawaii, are described, with emphasis on the measurement methodology, calibrations, and data accuracy. Monthly mean CO2 data, representative of global background conditions, are presented for the period of record. The monthly means were derived from an all‐data base of CO2 hourly averages archived at the National Oceanic and Atmospheric Administration (NOAA) Geophysical Monitoring for Climatic Change (GMCC) facility in Boulder, Colorado; at the Carbon Dioxide Information Analysis Center (CDIAC) in Oak Ridge, Tennessee; and in the microfiche version of this paper. Flags in the all‐data base identify CO2 hourly averages that have been deemed unreliable because of sampling and analysis problems or that are unrepresentative of clean background air because of influences of the local environment, for example, CO2 uptake by nearby vegetation or contamination and pollution effects. The select NOAA GMCC monthly mean data are compared with similar data obtained independently at Mauna Loa Observatory by the Scripps Institution of Oceanography. The average difference of corresponding monthly mean CO2 values for the two data sets is 0.15±0.18 ppm, where the indicated variability is the standard deviation. Careful scrutiny of the NOAA GMCC measurement, calibration, and data processing procedures that might have caused the small bias in the data has revealed no unusual errors.
Meteorological analysis of long range transport of mineral aerosols over the North Pacific
Authors: Merrill John T. , Uematsu Mitsuo , Bleck Rainer
Published: February 2008

Meteorological data are used to investigate the importance of source, transport, and removal factors in the temporal and areal variation of mineral dust concentrations observed in the SEAREX (Sea/Air Exchange Program) Network of aerosol sampling stations over the open Pacific Ocean. Earlier studies established that Asian desert dust is carried out over the ocean by the mid‐latitude westerlies and may be present over the entire North Pacific area. A 6‐year climatology of routine surface meteorological reports of dust in Asia is used to examine the broad maximum in mineral dust concentrations in the months February‐May observed at all the North Pacific sites. The gross features of this seasonal variation are controlled by the occurrence and areal extent of dust outbreaks. Secondary peaks in the frequency of dust storms, in October‐December, correspond to isolated peaks in the dust concentration at the sites closest to the mid‐latitudes. Isentropic trajectory analyses are presented for individual events of peak concentrations supporting earlier indications that the dust transport begins at high elevations over the arid regions and gradually subsides for those parcels which move toward the south. The average transport path for high concentration periods, obtained by superposing trajectory patterns for events over a 6‐year period, is shown to explain the latitudinal variation in the concentrations. Removal by local orographic showers at Oahu is shown to be unimportant, while removal by the intense tropical rainfall near Fanning Island is shown to be a dominant influence on the seasonal variation of concentrations there. Rainfall data at the remote Pacific sites indicate that the 1981–1986 period was generally representative, despite the strong El Niño/Southern Oscillation event which occurred in 1982–1983.
Atmospheric NO3: 1. Measurement technique and the annual cycle at 40°N
Authors: Solomon S. , Miller H. L. , Smith J. P. , Sanders R. W. , Mount G. H. , Schmeltekopf A. L. , Noxon J. F.
Published: February 2008

The nitrate radical abundance is often measured by making use of its strong absorption of visible radiation in a band near 662 nm. We show that this NO3 absorption feature has strong negative correlation with water vapor, which requires that water vapor absorption be explicitly considered in attempts to measure NO3 from the ground. Concurrent observation of a second, weaker NO3 feature near 623 nm provides an independent means of confirming and quantifying the accuracy of the measurement. These considerations are included in the analysis of a full year of nighttime stratospheric NO3 data at 40°N. The observations are in good general agreement with theoretical predictions and do not support the existence of a stratospheric scavenger for NO3.