bluuebunny/crossref_metadata_2025 huggingface dataset:
An optimal approach to overlapping bands with correlated k distribution method and its application to radiative calculations
Authors: Zhang Hua , Nakajima Teruyuki , Shi Guangyu , Suzuki Tsuneaki , Imasu Ryoichi
Published: October 2003

It is found that the possibly achieved higher accuracy cannot be obtained for all overlapping bands if only one scheme is used to treat them in atmospheric absorption calculations. The commonly used multiplication transmittance scheme is not acceptable when correlation existing in the practical absorption spectra becomes strong. Therefore an optimized scheme to obtain k distribution parameters for overlapping bands is developed in this paper based on the completely uncorrelated, perfectly correlated, and partly correlated schemes. Two partial correlation formulae are given in the paper. Calculations of radiative flux and atmospheric heating (or cooling) rate are validated in detail using a line‐by‐line model described in the paper for six model atmospheres. The optimized scheme developed here has an accuracy in longwave clear skies of 0.07 K d−1 in the entire troposphere and 0.35 K d−1 above the tropopause; the accuracy of upward, downward, and net fluxes is 0.76 W m−2 at all altitudes. In shortwave region, the absolute errors of the heating rate are less than 0.05 K d−1 in the troposphere and less than 0.25 K d−1 above the tropopause; net flux errors are less than 0.9 W m−2 at all altitudes. For an ensemble of 42 diverse atmospheres, the new scheme guarantees an average maximum error of longwave heating rate of 0.068 K d−1 in troposphere, 0.22 K d−1 above tropopause, and an accuracy of 1.1 W m−2 of radiative net flux for all the levels. For a case of doubled CO2 concentration, radiative forcing calculations have an accuracy of 0.04 W m−2.
System phase calibration of VHF spaced antennas using the echoes of aircraft and incorporating the frequency domain interferometry technique
Authors: Chen Jenn‐Shyong , Röttger Jürgen , Chu Yen‐Hsyang
Published: October 2003

Using multiple‐receiver arrays, the techniques of spaced antennas and spatial domain interferometry have been widely utilized in mesosphere‐stratosphere‐troposphere (MST) VHF and meteor radars. As these techniques are applied, the phase imbalance between the receiving channels will cause a biased result if it is not considered in the use of phase angles of the radar returns received in different receiving channels. In view of this, many methods have been employed for the phase calibration of receiving channels. In this paper, we propose one more method/procedure for the calibration, in which the commercial airplane flying routinely is used as a radar target. We measure the zenith and azimuth angles of the airplane with a video camera and estimate the range and height of the airplane from observation using the frequency domain interferometry (FDI) technique. Consequently, the track of the airplane in the vicinity of the radar site can be determined. The phase difference between the two radar echoes received by a pair of receiving channels is then predicted in accordance with the track of the airplane. Comparing the predicted phase difference with that observed, the phase imbalance between a pair of receiving channels could be obtained. Tens of cases show consistent results and so verify the reliability of the method. Also shown is the drift of system phase imbalance from season to season, which might be caused by the temperature dependence of antenna system components.
Tectonic inversion in the Santa Barbara System of the central Andean foreland thrust belt, northwestern Argentina
Authors: Kley Jonas , Monaldi César R.
Published: October 2003

The Santa Barbara System (SBS) of northern Argentina is a 400 km long segment of the Subandean foreland thrust belt. It is characterized by predominantly west verging, relatively high‐angle thrust faults. Many of these faults are reactivated normal faults from one branch of a complex Cretaceous to Paleogene rift system. Heteroaxial folding in parts of the SBS is probably due to a slight component of range‐parallel dextral strike‐slip motion acting on preexisting faults striking north and NE during inversion. Regional balanced cross sections along two transects across the northern SBS indicate that the major faults flatten into a detachment in the basement at about 10 km depth. Neogene E‐W contraction in the SBS is of the order of 21–26 km. Rift extension is not very well constrained but was probably less than 10 km. The structural style of the SBS differs from the thin‐skinned Subandean thrust belt to the north and from the large‐wavelength Sierras Pampeanas basement uplifts to the south. The changes between the different styles are sharp and coincide with the northern and southern boundaries of the rift in the foreland, suggesting that crustal or lithospheric heterogeneities exert an overriding control on foreland structural style.
Facies reconstruction of a hydrothermally altered dacite extrusive sequence: Evidence from geophysical downhole logging data (ODP Leg 193)
Authors: Bartetzko Anne , Paulick Holger , Iturrino Gerardo , Arnold Juliane
Published: October 2003

ODP Leg 193 drilled into the PACMANUS hydrothermal field (Papua New Guinea), which is an active hydrothermal vent field associated with felsic magmatism in a convergent geodynamic setting. The PACMANUS hydrothermal field is part of the eastern Manus Basin and is located near the crest of Pual Ridge, a 500 to 700 meters high felsic neo‐volcanic ridge. Two sites, Snowcap (Site 1188) and Roman Ruins (Site 1189), were drilled approximately 800 m apart. Although low core recovery limited the examination of the subsurface geology, geophysical downhole measurements provided continuous records of in‐situ physical properties with depth and were used to reconstruct lithostratigraphic profiles. Downhole logging operations included standard wire line logging and Logging While Drilling (LWD) measurements. Electrical resistivity images of the borehole wall were examined to find characteristic textures and three different volcanic facies were distinguished: coherent dacite, volcaniclastic dacite and brecciated dacite. In addition, intervals with sulfide mineralization were identified based on characteristic responses of the photoelectric factor log. A comparison of the reconstructed profiles from both sites shows considerable differences in the proportions of facies and the thickness of individual layers. Thick units of coherent facies are predominant at Snowcap and indicate a proximal position of the site within the volcanic system of Pual Ridge. At Roman Ruins, thin individual layers with rapid changes in volcanic facies and a higher proportion of volcaniclastic and brecciated dacite suggest a medial position. These differences in volcanic facies show that the volcanic architecture at Pual Ridge is characterized by small‐scale facies changes, emplacement of small‐volume individual lava flows and complex geometries of individual emplacement units. Geophysical logging data suggest that subseafloor hydrothermal activity is focused to the area around one hole at Roman Ruins. Downhole logs from this hole show characteristic cyclic patterns in the electrical resistivity and photoelectric factor logs indicating that hydrothermal sulfide mineralization is concentrated at the tops of individual lava flows representing paleo‐seafloor positions.
Remote continental forcing of phytoplankton biogeochemistry: Observations across the “Caribbean‐Atlantic front”
Authors: Corredor Jorge , Morell Julio , López José , Armstrong Roy , Dieppa Angel , Cabanillas Carla , Cabrera Alvaro , Hensley Val
Published: October 2003

A persistent front, in large part generated by the confluence of western tropical North Atlantic (WTNA) surface waters with the massive freshwater plumes of the Orinoco and Amazon Rivers, separates waters of the Caribbean Sea from those of the adjacent WTNA. We characterized physical and biogeochemical properties across this front in order to elucidate the processes leading to enhanced near surface phytoplankton biomass within the front. Although chlorophyll content of the water column to either side of the front is similar, phytoplankton in waters within this “Caribbean‐Atlantic front” resides for the most part above the pycnocline and sustains large production rates in comparison with the lower rates of deep, sub‐pycnocline WTNA phytoplankton. Nitrogen budgets indicate that a substantial fraction of the production within the front may arise from biological nutrient recycling while the deeper WTNA communities rely to a greater extent on nutrients from below the nutricline.
Color reflectance of Chinese loess and its implications for climate gradient changes during the last two glacial‐interglacial cycles
Authors: Yang S. L. , Ding Z. L.
Published: October 2003

To examine the relationship between color changes of loess deposits and paleoclimate conditions, a north‐south transect consisting of twelve loess sections were studied. Color reflectance was measured on loess‐paleosol samples from the loess transect which accumulated over the last two glacial‐interglacial cycles. The redness value, a*, shows an overall southward increase for both loess and soil units, coinciding with the pattern of a southerly increase in pedogenic development and the present north‐south climatic gradient. The redness of loess deposits is linearly correlated with latitude values, implying that this parameter is an efficient proxy for the weathering intensity of loess deposits. The gradient of weathering intensity is much steeper during interglacials than in glacials, by comparison of color records for different time interval.
Peroxy radical behavior during the Transport and Chemical Evolution over the Pacific (TRACE‐P) campaign as measured aboard the NASA P‐3B aircraft
Authors: Cantrell Christopher A. , Edwards G. D. , Stephens S. , Mauldin R. L. , Zondlo M. A. , Kosciuch E. , Eisele F. L. , Shetter R. E. , Lefer B. L. , Hall S. , Flocke F. , Weinheimer A. , Fried A. , Apel E. , Kondo Y. , Blake D. R. , Blake N. J. , Simpson I. J. , Bandy A. R. , Thornton D. C. , Heikes B. G. , Singh H. B. , Brune W. H. , Harder H. , Martinez M. , Jacob D. J. , Avery M. A. , Barrick J. D. , Sachse G. W. , Olson J. R. , Crawford J. H. , Clarke A. D.
Published: October 2003

Peroxy radical concentrations were measured aboard the NASA P‐3B aircraft during the Transport and Chemical Evolution over the Pacific (TRACE‐P) campaign in the spring of 2001 and varied in ways that depended on radical production rates and reactive nitrogen concentrations. Measurements of HO2, HO2 + RO2, and OH during this study allowed calculation of radical ratios, examination of functional relationships of these ratios on controlling variables, and comparison with numerical model estimations. Radical production terms show changes in relative contributions at low, middle, and high total production rates that are understandable in terms of systematic variations in the controlling components (trace gas concentrations and photolysis rate coefficients). Ozone tendency calculations indicate net ozone production in the western Pacific basin because the concentrations of critical precursor trace gases (e.g., NOx, hydrocarbons) are highest there. The dependence of ozone tendency follows the concentration of NO systematically. Peroxy radical levels on the two aircraft (HO2 + RO2 on the P‐3B and HO2 on the DC‐8) during two relatively short prescribed intercomparison periods were in good agreement in one instance and poorer in another given reasonable assumptions about the apportioning of radicals between HO2 and RO2. Recommended changes to CH2O photolysis quantum yields, HO2 self reaction, and O(1D) quenching kinetics lead to small changes (<5%) in calculated peroxy radical levels for TRACE‐P conditions. There is evidence from this campaign that peroxy radicals are lost by interaction with aerosols and cloud droplets.
The Legal Status of Religious Minorities: Imāmī Shī'ī Law and Iran's Constitutional Revolution
Authors: Tsadik Daniel
Published: October 2003

This study investigates the extent to which the laws of Iran's Constitutional Revolution mark a break with Islam with regard to the legal status of religious minorities as reflected in the writings of some eighteenth- and nineteenth-century Imāmī Shī ī ulamā . Whereas Shī ī law usually treated religious minorities and Shī īs differentially, some—but not all—of the Revolutionary enactments treat religious minorities as the equals of Muslims. I conclude that the legal status of some religious minorities improved only somewhat during the Revolution as compared to their status under Shī ī law. The two-faced nature of the Revolution's enactments echoes the rival forces at work. The controversy over whether religious minorities should be treated as equals was legal in nature, but no less a dispute over the orientation of Iranian society.
X‐irradiation of adult spinal cord increases its capacity to support neurite regeneration in vitro
Authors: Pinjuh Danny , Bedi Kuldip S.
Published: October 2003

Previous in vitro studies have shown that X‐irradiation during early postnatal life can change the environment of CNS tissue in later adult life such that it becomes more supportive of neurite regeneration from adult dorsal root ganglion (DRG) neurons than non‐irradiated tissue. The question arises whether or not x‐irradiation during adult life can alter the CNS environment such that it also becomes more supportive of neurite regeneration. This was investigated by exposing portions of the spinal cord of adult rats to 10, 20 or 40 Gray of X‐irradiation and later using this tissue to prepare cryosections suitable for use as a substrate in a cryoculture assay. Fixed cryocultures were immunolabelled using anti‐glial fibrillary acidic protein (GFAP) to visualise the tissue sections and anti‐growth associated protein (GAP‐43) to visualise the regenerating neurites. Tissue sections from sham‐irradiated animals and from those irradiated with 10 Gray did not support the regeneration of neurites. However, sections of spinal cords from rats treated with either 20 or 40 Gray of X‐irradiation 4 or 32 days prior to sampling were found to support a certain degree of neurite regeneration. It is concluded that X‐irradiation of adult CNS tissue can alter its environment such that it becomes more supportive of neurite regeneration and it is speculated that this change may be the result of alterations in the glial cell populations in the post‐irradiated tissues.
A quantitative method to measure maximal workspace of the trapeziometacarpal joint—normal model development
Authors: Kuo Li‐Chieh , Cooney William P. , Kaufman Kenton R. , Chen Qing‐Shan , Su Fong‐Chin , An Kai‐Nan
Published: October 2003

Introduction: A reliable and quantitative method for measuring motion of the thumb is lacking. In particular, review of the previous methods of motion analysis of the thumb joints shows that there is no objective method for clinicians to assess the impairment of the thumb trapeziometacarpal (TMC) joint. Based on the concept of the three‐dimensional (3‐D) space within which the first metacarpal can move relative to the trapezium (a concept of defining and measuring the workspace of the TMC motion), we present a quantitative method for measuring motion and impairment (loss of function) of the TMC joint.

Methods: Twenty normal subjects were recruited in this study. An electromagnetic device was placed over the thumb metacarpal and long finger metacarpal, the 3‐D relationship between them previously established. We measured the position and orientation of the TMC motion in space. Maximum movements of the thumb TMC joint in circumduction, flexion–extension and abduction–adduction were used to construct the 3‐D maximal workspace of the TMC joint. Mathematical methods were used to verify the model and calculate the maximal workspace.

Results: The results of this study demonstrate accurate and repeatable measurement of 3‐D TMC motion with high statistical reliability and low variability of the maximal TMC workspace. A statistically significant linear correlation between the maximal surface area and the square of the first metacarpal length was obtained.

Conclusion: We conclude that a quantitatively comparative measurement of the range of motion of the TMC joint can be obtained with potential to measure motion in joints affected by arthritis or trauma and measured in both dynamic and static positions of the thumb. © 2003 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.
Enhanced marine CH4 emissions to the atmosphere off Oregon caused by coastal upwelling
Authors: Rehder G. , Collier R. W. , Heeschen K. , Kosro P. M. , Barth J. , Suess E.
Published: October 2003

Methane in surface waters and marine air off Oregon (44°24′N–44°54′N, 124°36′W–125°24′W) was continuously surveyed in July 1999. During a high‐resolution survey after a period of steady winds from the north, CH4 concentrations were high in the northeastern region, near the shelf edge. The highest CH4 concentrations were 2.5 times higher than equilibrium with the atmospheric partial pressure. In contrast, concentrations were near equilibrium in the western part of the survey area, the Hydrate Ridge. The increase in CH4 from southwest to northeast correlates with a drop in sea surface temperature (SST), from 16.5°C to <13.5°C, toward the shelf edge. The observed SST pattern was caused by summer upwelling off Oregon. The results suggest that CH4 derived from bottom sources near the shelf/slope break and methane found in connection with shallow (100–300 m) turbidity layers is transported to the surface by coastal upwelling, which causes an enhanced net flux of CH4 to the atmosphere. Vertical profiles of the methane distribution on the shelf in October demonstrate the accumulation of methane introduced by shelf sources. Surface concentrations at these stations in October (during nonupwelling conditions) were lower than in July (during upwelling) and were only slightly oversaturated with respect to the atmosphere. An acoustic Doppler current profiler survey indicates that the observed trend cannot be attributed to a surface flow reversal in the area. The low‐salinity waters in the core of the Columbia River plume (S < 31) showed no enhanced CH4 concentrations. The trend of higher CH4 concentrations at lower temperatures existed over the whole 17‐day survey, but large spatial and temporal variations existed. The presence of methane sources in regions of coastal upwelling worldwide, such as shallow seeps, gas hydrates, and intermediate nepheloid layers, suggests that the enhancement of CH4 fluxes to the atmosphere by coastal upwelling occurs on a global scale.
Canonical transform method for processing radio occultation data in the lower troposphere
Authors: Gorbunov M. E.
Published: October 2003

The methods of processing radio occultation data in multipath zones which were used up to now have very strong restrictions of the applicability. In this paper, we introduce a new approach to the problem of deciphering the ray structure of wave fields in multipath zones using the short‐wave asymptotic solution of the wave problem. In geometric optics a canonical transform resolves multipath by introducing new coordinate and momentum in such a way that different rays are distinguished by their coordinates. The wave field is processed by a Fourier integral operator associated with the canonical transform. The transformed wave function can then be written in the single‐ray approximation, which allows for the determination of refraction angles from the derivative of the eikonal. The new method retains all the advantages of the back propagation such as the removal of effects of diffraction in free space and the enhancement of the vertical resolution in retrieved profiles, but it has much wider applicability limits. The method is convenient for operational applications. We discuss a fast numerical implementation of the method and present the results of numerical simulations confirming the applicability of the method.
Plant community composition mediates both large transient decline and predicted long‐term recovery of soil carbon under climate warming
Authors: Saleska Scott R. , Shaw M. Rebecca , Fischer Marc L. , Dunne Jennifer A. , Still Christopher J. , Holman Melisa L. , Harte John
Published: October 2003

We integrated two methods, experimental heating and observations across natural climate gradients, to elucidate both short‐ and long‐term climatic controls on ecosystem carbon storage and to investigate carbon‐cycle feedbacks to climate in montane meadows. A 10‐year heating experiment warmed and dried heated plot soils and substantially decreased (by ∼200 ± 150 g C m−2) the amount of carbon stored in soil organic matter, a positive feedback to warming. In situ CO2 flux measurements, laboratory soil incubations, and a heating‐induced shift in vegetation community composition from high‐ to low‐productivity species indicate that a decline in community productivity and resultant decrease in soil inputs from plant litter caused most of the soil carbon decrease. An alternative widely hypothesized mechanism for soil carbon decrease under warming is stimulation of soil respiration, but we observed no increase in seasonally integrated soil respiration in our experiment (soil drying inhibited microbial decomposition even as soil warming stimulated it). To extend our analysis from the short‐term transient response represented by the heating experiment to the presumed long‐term approximate steady state represented by natural climate gradients, we tested a hypothesized relation between vegetation community composition (which controls both litter input rate and average litter quality) and soil carbon along the climate gradient. The gradient analysis implies that the experimentally induced decline in soil carbon is transient and will eventually reverse as lower quality litter inputs from the increasingly dominant low‐productivity species reduce soil respiration losses. This work shows that ecological processes can control both short‐ and long‐term responses to climate change, confirming some model‐based predictions about the importance of vegetation shifts, but challenging the widely held hypothesis that the effect of temperature change on respiration will dominate soil carbon changes.
Carbon cycle, vegetation, and climate dynamics in the Holocene: Experiments with the CLIMBER‐2 model
Authors: Brovkin Victor , Bendtsen Jørgen , Claussen Martin , Ganopolski Andrey , Kubatzki Claudia , Petoukhov Vladimir , Andreev Andrei
Published: October 2003

Multiple proxy data reveal that the early to middle Holocene (ca. 8–6 kyr B.P.) was warmer than the preindustrial period in most regions of the Northern Hemisphere. This warming is presumably explained by the higher summer insolation in the Northern Hemisphere, owing to changes in the orbital parameters. Subsequent cooling in the late Holocene was accompanied by significant changes in vegetation cover and an increase in atmospheric CO2 concentration. The essential question is whether it is possible to explain these changes in a consistent way, accounting for the orbital parameters as the main external forcing for the climate system. We investigate this problem using the computationally efficient model of climate system, CLIMBER‐2, which includes models for oceanic and terrestrial biogeochemistry. We found that changes in climate and vegetation cover in the northern subtropical and circumpolar regions can be attributed to the changes in the orbital forcing. Explanation of the atmospheric CO2 record requires an additional assumption of excessive CaCO3 sedimentation in the ocean. The modeled decrease in the carbonate ion concentration in the deep ocean is similar to that inferred from CaCO3 sediment data [Broecker et al., 1999]. For 8 kyr B.P., the model estimates the terrestrial carbon pool ca. 90 Pg higher than its preindustrial value. Simulated atmospheric δ13C declines during the course of the Holocene, similar to δ13C data from the Taylor Dome ice core [Indermühle et al., 1999]. Amplitude of simulated changes in δ13C is smaller than in the data, while a difference between the model and the data is comparable with the range of data uncertainty.
Quantitative measurement of the microphysical and optical properties of cirrus clouds with four different in situ probes: Evidence of small ice crystals
Authors: Gayet Jean‐François , Auriol Frédérique , Minikin Andreas , Ström Johan , Seifert Marco , Krejci Radovan , Petzold Andreas , Febvre Guy , Schumann Ulrich
Published: October 2003

Original microphysical and optical measurements were obtained in cirrus clouds on the Southern and Northern hemispheres during the INCA experiments using four independent techniques: (1) the Counterflow Virtual Impactor, (2) the PMS FSSP‐300, (3) the PMS 2D‐C and (4) the Polar Nephelometer probes. The combination of these four techniques provides a description of particles within a diameter range varying from a few micrometers (typically 3 μm) to 800 μm. Because of the presence of small ice crystals in cirrus clouds, it is particularly important to overcome the limited accuracy of the sensors used in the experiments for the cloud microphysical measurements. Representative examples of combined results suggest that the available measurements are reliable and can be used for the ongoing comparison between the results from the SH and NH campaigns. The results give the definite picture that the observations of numerous (5 to 10 cm−3) small ice crystals in cirrus clouds are a relatively common microphysical feature.
Characterizing global CO2 interannual variability with empirical orthogonal function/principal component (EOF/PC) analysis
Authors: Lintner Benjamin R.
Published: October 2003

EOF/PC analysis is applied to low‐pass filtered deseasonalized CO2 growth rates from a global observational network, and two statistically‐significant modes of interannual variability are identified. The spatial structure of the 1st mode is characterized by an interhemispheric gradient, while the 2nd mode is characterized by a land‐ocean dipole in the Northern Hemisphere midlatitudes. The gravest PC reflects ENSO‐like variability, although the phase relationship to ENSO appears to change around 1990. However, the leading PC exhibits a statistically‐significant, stationary phase relative to an index of the Pacific Decadal Oscillation (PDO) throughout the sampling period. The next‐to‐leading PC, on the other hand, shows little relation to any of the climate indices examined here. These relationships intimate that, while ENSO may play a substantial role in interannual CO2 growth rate variability, the ENSO‐growth rate relationship is not stationary, and additional modes of interannual variability may significantly influence year‐to‐year changes in CO2.
Impact of high Saharan dust inputs on dissolved iron concentrations in the Mediterranean Sea
Authors: Guieu C. , Bozec Y. , Blain S. , Ridame C. , Sarthou G. , Leblond N.
Published: October 2003

During the PROSOPE cruise (Sept. 1999) in the Mediterranean Sea, dissolved iron concentrations in seawater and iron and aluminium concentrations in aerosols collected on board were investigated. Concentrations in aerosols were about two times higher in the Tyrrhenian Sea than in the west (Alboran Sea). This was in good agreement with the observed increase in dissolved iron concentrations in the surface waters from West to East. Depth profiles were characterised by a maximum in the surface mixed layer. Using an in vitro experiment, iron released from Saharan dust during the season characterized by a stratified water column and a low primary productivity was estimated: it resulted in an accumulation of 0.5–0.8 nM dissolved iron, in good agreement with the observed iron enrichment in the surface water (0.8 nM). This study confirms the significance of atmospheric input of Saharan origin on the iron cycle in the Mediterranean Sea.
Observations and analysis of polar stratospheric clouds detected by POAM III during the 1999/2000 Northern Hemisphere winter
Authors: Bevilacqua R. M. , Fromm M. D. , Alfred J. M. , Hornstein J. S. , Nedoluha G. E. , Hoppel K. W. , Lumpe J. D. , Randall C. E. , Shettle E. P. , Browell E. V. , Butler C. , Dörnbrack A. , Strawa A. W.
Published: October 2003

We present an overview of polar stratospheric cloud (PSC) measurements obtained by POAM III in the 1999/2000 Northern Hemisphere winter. PSCs were observed at POAM latitudes from mid‐November to 15 March. PSCs in the early season generally occurred between 17 and 25 km. The central altitude of the PSC observations, roughly 21 km, is unchanged between November and late January. PSCs were not observed between 7 and 27 February. When they reappeared, they formed at distinctly lower altitudes, centered roughly at 16 km. We also present both qualitative and quantitative comparisons with airborne lidar and in situ balloon measurements of PSCs obtained over the Norwegian Sea and Scandinavia over the 25–27 January time period. We find that the large‐scale PSC altitude features and morphology are well reproduced in the POAM measurements. Finally, we use PSC occurrence probabilities, analyzed as a function of ambient temperature relative to the NAT saturation point, to infer irreversible denitrification. This denitrification is observed to maximize in late February at levels of at least 75% in the 19–21 km region, with similar values in the 16–18 km region. No denitrification was inferred above 21 km or below 16 km.
Variation in composition of fine particulate emissions from heavy‐duty diesel vehicles
Authors: Fraser Matthew P. , Lakshmanan Kalyan , Fritz Steven G. , Ubanwa Basil
Published: October 2003

Samples of fine particle emissions from four heavy‐duty diesel vehicles were analyzed for chemical and molecular composition. Significant variation was found for the composition of particle emissions from vehicles under load, with the fraction of carbonaceous particles emitted as elemental carbon (i.e., soot) varying between 19 and 94%. The emissions from vehicles idling shows little compositional variation with low soot formation and elemental carbon representing between 12 and 21% of total carbon emitted. This variation is important to consider when performing source apportionment calculations as the difference in fraction carbon emitted as elemental carbon is used to separate diesel emissions from gasoline‐powered vehicle emissions and other sources. The molecular composition of the organic particulate matter was quantified for samples collected from each of the four vehicles under load plus a composite sample of all four vehicles while idling. The variation of the molecular composition of organic particulate matter was highest for polycyclic aromatic hydrocarbons and least for petroleum biomarkers, supporting the use of petroleum biomarkers as tracers for diesel vehicle emissions when the compositional information from sources is based on a limited sample set.
Influence of phytoplankton on the global radiation budget
Authors: Frouin R. , Iacobellis S. F.
Published: October 2003

Oceanic phytoplankton may exert a warming influence on the planet by decreasing surface albedo. Compared with the case of pure seawater, the globally and annually averaged outgoing radiative flux is decreased by a probable value of 0.25 Wm−2. This value corresponds to about 20% of the combined radiative forcing by greenhouse gases and anthropogenic aerosols since preindustrial times, including indirect effects. The relative importance of phytoplankton is greater on regional and seasonal scales, with forcing values reaching −1.5 Wm−2 in coastal zones and high‐latitude regions during summer. The annual amplitude of radiative forcing by phytoplankton is large in subpolar regions, owing to the conjugate action of cloud amount and biomass level. Spatial and temporal variability of the forcing is affected by phytoplankton type, some reflective species increasing the outgoing radiative flux. The effects of space‐ and time‐varying phytoplankton on surface albedo should be taken into account explicitly in the numerical modeling of climate change.
Stable isotope compositions of waters in the Great Basin, United States 2. Modern precipitation
Authors: Friedman Irving , Smith George I. , Johnson Craig A. , Moscati Richard J.
Published: October 2003

Precipitation was collected between 1991 and 1997 at 41 locations within and adjacent to parts of the Great Basin lying in California, Oregon, Nevada, and Utah. These samples were analyzed for their deuterium (δD) and oxygen‐18 (δ18O) contents. Separate collections were made of summer and winter season precipitation at stations ranging in elevation from –65 m to 3246 m. The δD per mil values of stations that were closely spaced but at different elevations showed an average δD decrease of approximately 10‰/km rise in elevation. Data for all samples representing winter precipitation, when plotted on a δD versus δ18O plot, fall close to the Meteoric Water Line (δD = 8 δ18O + 10); samples representing summer precipitation define a line of slightly lower slope due to evaporation of the raindrops during their passage from cloud to ground. Comparison of our 1991–1997 δD data with those from the same three stations reported by an earlier study in the southeastern California shows seasonal differences ranging from 0 per mil to 19‰ (average: 15) and annual differences ranging from 0 to 13 per mil (average: 2), illustrating the degree of annual and seasonal variability in this region. When contoured, the δD values display gradients indicating a north to northwest decrease in deuterium, with values ranging from −60 to −125‰ in winter precipitation and from −40 to −110‰ in summer precipitation. These gradient trends can be explained by the predominance of air mass trajectories originating in the tropical Pacific, the Gulf of California, and (in summer) the Gulf of Mexico.
Physical and chemical properties of aerosols in the wet and dry seasons in Rondônia, Amazonia
Authors: Artaxo Paulo , Martins José Vanderlei , Yamasoe Marcia A. , Procópio Aline S. , Pauliquevis Theotonio M. , Andreae Meinrat O. , Guyon Pascal , Gatti Luciana V. , Leal Ana Maria Cordova
Published: October 2003

As part of the Large‐Scale Biosphere‐Atmosphere Experiment in Amazonia (LBA), a large study of aerosol and trace gas properties was conducted in Amazonia during the dry and wet seasons and for pasture and primary forest sites. Aerosol mass and elemental composition were measured on filters for both fine (dp < 2.0 μm) and coarse (2.0 < dp < 10 μm) modes using polycarbonate filters mounted in stacked filter units (SFU). Measurements with real‐time aerosol and trace gas monitors were made, parallel to the collection of filter samples to obtain high time resolution (1–30 min). Black carbon equivalent (BCE) was determined with a multiwavelength Aethalometer as well as by reflectance in the fine‐mode SFU samples. Elemental carbon as well as total and organic carbon was measured using an R&P 5400 real‐time carbon monitor. PM10 aerosol mass concentrations were determined with a Tapered Element Oscillating Monitor (TEOM) monitor every 5 min. CO, O3, NO, and NO2 were analyzed with Thermo Environment monitors with trace level capabilities for NOx. A TSI 3010 particle counter measured the total particle number concentration (dp > 10 nm) every minute. A 55‐m tower in a primary forest in Rondônia and a facility built on a pasture site were used to operate the instrumentation for 4 months in the wet season and 3 months in the dry season of 1999. Particle‐Induced X‐Ray Emission (PIXE) was used to measure the concentration of 22 trace elements for fine‐ and coarse‐mode aerosol. During the wet season, very clean atmospheric conditions were observed at both sites. Particle concentration averaged 900 cm−3, black carbon averaged 250 ng m−3, and mean fine‐mode mass concentration was 2.9 μg m−3. In sharp contrast, very high concentrations were observed in the dry season for all the parameters at both sampling sites. Aerosol mass concentrations up to 250 μg m−3 and particle number concentrations of more than 40,000 cm−3 were observed, while the CO peaked at 8 ppm and NO2 reached 16 ppb. High correlation was observed between BCE, NO2, CO, aerosol particle number, mass, aerosol optical thickness, and other properties linked to biomass‐burning emissions. Relatively large concentrations of phosphorus in the coarse‐mode particles were observed, especially at nighttime. The emission of biogenic particulate P could have an effect in the nutrient cycling of this essential and key nutrient, which is present almost exclusively in the form of aerosol particles. Phosphorus is exchanged in the aerosol phase and mostly for coarse‐mode particles and during nighttime.
Low frequency variability of tropical cyclone potential intensity 1. Interannual to interdecadal variability
Authors: Bister Marja , Emanuel Kerry A.
Published: October 2003

Recent research suggests that anthropogenic global warming would be associated with an increase in the intensity of tropical cyclones. A recent statistical analysis of observed tropical cyclone intensity shows that its variability with location and season is strongly tied to the variability of the thermodynamic potential intensity (PI) of tropical cyclones, as calculated using a theory described in an earlier work by the authors. Thus it is of interest to look for possible trends in global measures of PI, which are far more stable than those of actual storm intensity. We estimate global trends of PI from 1958 to 1996, averaged over the region where it exceeds 40 m s−1, using the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis and the NCEP Empirical Orthogonal Function (EOF) sea surface temperature (SST) analysis. We adjust the Reanalysis temperatures for a large, spurious temperature increase that occurred around 1979. We do this by subtracting from the Reanalysis the atmospheric temperature difference between pairs of years with similar tropical SST before and after 1979. The value of the global mean PI is very large for the SST of the corresponding region in the mid‐1990s. Supported by a recent study on the effects of ozone decrease on tropospheric temperatures, we suggest that the ozone decrease might be one of the factors contributing to increase of PI during the 1990s.
Photochemical ozone budget during the BIBLE A and B campaigns
Authors: Ko Malcolm , Hu Wenjie , Rodríguez José M. , Kondo Yutaka , Koike Makoto , Kita Kazuyuki , Kawakami Shuji , Blake Donald , Liu Shaw , Ogawa Toshihiro
Published: October 2003

Using the measured concentrations of NO, O3, H2O, CO, CH4, and NMHCs along the flight tracks, a photochemical box model is used to calculate the concentrations of the Ox radicals, the HOx radicals, and the nitrogen species at the sampling points. The calculations make use of the measurements from radiometers to scale clear sky photolysis rates to account for cloud cover and ground albedo at the sampling time/point. The concentrations of the nitrogen species in each of the sampled air parcels are computed assuming they are in instantaneous equilibrium with the measured NO and O3. The diurnally varying species concentrations are next calculated using the box model and used to estimate the diurnally averaged production and removal rates of ozone for the sampled air parcels. Clear sky photolysis rates are used in the diurnal calculations. The campaign also provided measured concentration of NOy. The observed NO/NOy ratio is usually larger than the model calculated equilibrium value. There are several possible explanations. It could be a result of recent injection of NO into the air parcel, recent removal of HNO3 from the parcel, recent rapid transport of an air parcel from another location, or a combination of all processes. Our analyses suggest that the local production rate of O3 can be used as another indicator of recent NO injection. However, more direct studies using air trajectory analyses and other collaborative evidences are needed to ascertain the roles played by individual process.
Photochemical ozone production at a subtropical island of Okinawa, Japan: Implications from simultaneous observations of HO2 radical and NOx
Authors: Kanaya Yugo , Matsumoto Jun , Akimoto Hajime
Published: October 2003

During the Observations at a Remote Island of Okinawa (ORION99) field campaign, HO2 radical and NOx concentrations were simultaneously measured with other important parameters relevant to photochemistry. The observed HO2 concentration levels, the relationship between HO2 and NOx, and the balance between NO and NO2 were well reproduced by model calculations based on the current photochemistry theory, indicating that the photochemistry taking place at the island was understandable within known chemistry. Thus the photochemical ozone production rate estimated from the calculated peroxy radical concentrations would be reliable. The isoprene peroxy radical + NO reaction contributed to ozone production by the similar degree to the HO2 + NO reaction because of high isoprene concentrations at ground level. The net ozone production rate during daytime was calculated to be +0.2–3.4 ppbv h−1 due to moderate NO concentrations (36–244 parts per trillion by volume (pptv)) there which were higher than the NO compensation point of ∼30 pptv. Sensitivity studies showed that the ozone production rate was calculated within NOx‐limited regime. Thus the ozone production rate would be relatively uniform throughout the boundary layer even if isoprene concentration had a steep vertical gradient. Up to ∼20 ppbv of ozone would be photochemically produced in a day, suggesting that clear diurnal variations of ozone with daytime buildup of 16 ppbv observed for the air mass traveled over the island in 1996 could be explained by photochemistry.
Tracer‐based determination of vortex descent in the 1999/2000 Arctic winter
Authors: Greenblatt Jeffery B. , Jost Hans‐Jürg , Loewenstein Max , Podolske James R. , Hurst Dale F. , Elkins James W. , Schauffler Sue M. , Atlas Elliot L. , Herman Robert L. , Webster Christopher R. , Bui T. Paul , Moore Fred L. , Ray Eric A. , Oltmans Samuel , Vömel Holger , Blavier Jean‐François , Sen Bhaswar , Stachnik Robert A. , Toon Geoffrey C. , Engel Andreas , Müller Melanie , Schmidt Ulrich , Bremer Holger , Pierce R. Bradley , Sinnhuber Björn‐Martin , Chipperfield Martyn , Lefèvre Franck
Published: October 2003

A detailed analysis of available in situ and remotely sensed N2O and CH4 data measured in the 1999/2000 winter Arctic vortex has been performed in order to quantify the temporal evolution of vortex descent. Differences in potential temperature (θ) among balloon and aircraft vertical profiles (an average of 19–23 K on a given N2O or CH4 isopleth) indicated significant vortex inhomogeneity in late fall as compared with late winter profiles. A composite fall vortex profile was constructed for 26 November 1999, whose error bars encompassed the observed variability. High‐latitude extravortex profiles measured in different years and seasons revealed substantial variability in N2O and CH4 on θ surfaces, but all were clearly distinguishable from the first vortex profiles measured in late fall 1999. From these extravortex‐vortex differences we inferred descent prior to 26 November: as much as 397 ± 15 K (1σ) at 30 ppbv N2O and 640 ppbv CH4, and falling to 28 ± 13 K above 200 ppbv N2O and 1280 ppbv CH4. Changes in θ were determined on five N2O and CH4 isopleths from 26 November through 12 March, and descent rates were calculated on each N2O isopleth for several time intervals. The maximum descent rates were seen between 26 November and 27 January: 0.82 ± 0.20 K/day averaged over 50–250 ppbv N2O. By late winter (26 February to 12 March), the average rate had decreased to 0.10 ± 0.25 K/day. Descent rates also decreased with increasing N2O; the winter average (26 November to 5 March) descent rate varied from 0.75 ± 0.10 K/day at 50 ppbv to 0.40 ± 0.11 K/day at 250 ppbv. Comparison of these results with observations and models of descent in prior years showed very good overall agreement. Two models of the 1999/2000 vortex descent, SLIMCAT and REPROBUS, despite θ offsets with respect to observed profiles of up to 20 K on most tracer isopleths, produced descent rates that agreed very favorably with the inferred rates from observation.
Neutralization of soil aerosol and its impact on the distribution of acid rain over east Asia: Observations and model results
Authors: Wang Zifa , Akimoto Hajime , Uno Itsushi
Published: October 2003

A comprehensive Air Quality Prediction Modeling System is applied to simulate the pH values in precipitation and to investigate neutralization by soil aerosols and their influence on the distribution of acid rain over east Asia. A modified deflation module is designed to provide explicit information on the soil aerosol loading. Numerical simulation was performed for 1 year, from 15 December 1998 to 31 December 1999. Wet deposition monitoring data at 17 sites of the Acid Deposition Monitoring Network in east Asia in addition to State Environmental Protection Agency data were used to evaluate the model, and a reasonable agreement was obtained. Observed evidence clearly shows that in northern China acid deposition is heavily influenced and buffered by natural soil dust from desert and semiarid areas. The observed mean rainwater pH value in northern China is the highest, between 6.0 and 7.2, while in southern China, where many areas severely impacted by acid precipitation are located, the pH value is much lower, between 3.5 and 5. In Japan the mean pH value is 4.7, significantly higher than that in southern China, while in South Korea the pH value is intermediate between those in northern China and Japan. The model is capable of reproducing this geographical distribution of rainwater pH over east Asia. The simulation results for 1999 demonstrated strong neutralization of precipitation by soil aerosols over northeast Asia, and the distribution pattern of acid rain was also altered. The annual mean pH values in northern China and Korea show a remarkable increase of 0.8–2.5, while the increase in mean pH values over southern China and Japan are less than 0.1. The neutralization effects vary by season, with the greatest influence in spring, when pH values increased by 0.1–0.4 in Japan, 0.5–1.5 in Korea, and more than 2 in northern China.
GPS radio occultations with CHAMP: A radio holographic analysis of GPS signal propagation in the troposphere and surface reflections
Authors: Beyerle G. , Hocke K. , Wickert J. , Schmidt T. , Marquardt C. , Reigber C.
Published: October 2003

Within the first nine months following the activation of the GPS radio occultation experiment aboard the low Earth orbiting satellite CHAMP, more than 25,000 occultation events have been observed. A radio holographic analysis of 3783 occultation events, recorded between 14 May 2001 and 10 June 2001, reveals that in about 20–30% of these events the received signal contains contributions from components reflected at Earth's surface. On the basis of geometrical ray tracing and multiple phase screen calculations, characteristic frequency shifts in the radio holograms' power spectral densities are analyzed quantitatively. These frequency shifts are found to be dominated by surface elevation at the reflection point location and ground‐level refractivity. Using temperature and pressure profiles from European Centre for Medium‐Range Weather Forecasting (ECMWF) analyses, ground‐level specific humidities are derived in good agreement with ECMWF values. Complex patterns found in radio hologram spectra within a subset of observations at low latitudes are interpreted in terms of multipath propagation caused by layered structures in the refractivity field.