bluuebunny/crossref_metadata_2025 huggingface dataset:
Annual and El Niño‐Southern Oscillation variations in observations of in situ stratospheric ozone over Peninsular Malaysia
Authors: Yonemura Seiichiro , Tsuruta Haruo , Sudo Shigeto , Peng Leong Chow , Fook Lim Sze , Johar Zubaidi
Published: October 2002

We present stratospheric ozone profiles over Peninsular Malaysia in equatorial Southeast Asia measured twice a month for the 8 years from 1992 to 1999. For correlation analyses we used data after July 1993, to exclude the period just after the eruption of Mount Pinatubo. In the bottom of the stratosphere (the layer from the tropopause (16.5 ± 0.7 km) up to 20 km), ozone concentrations oscillated annually, showing minimum values around February–April in the northern winter and maximum values around July–September in the northern summer. The amplitude of the annual oscillation of ozone in the bottom of the stratosphere seemed to be several dozen percent larger than the amplitudes of the oscillations over Natal in Brazil and Samoa in the Pacific Ocean. Ozone concentrations of individual soundings closely correlated with temperature (R = 0.833 at 17.5 km; R = 0.854 at 19.5 km) and varied inversely with tropopause heights (R = −0.615 at 17.5 km; R = −0.390 at 19.5 km), indicating the influence of seasonal variations in convection and Brewer‐Dobson circulation induced by extratropical wave driving. The ozone anomaly from monthly mean values in the bottom of the stratosphere was positively correlated (R = 0.570 at 17.5 km) with the Southern Oscillation Index (SOI) through changes in tropopause heights; this was unexpectedly different from the negative correlation between ozone and SOI in the western Pacific. This east‐west difference might be attributable to the different circulation systems in the western Pacific and Peninsular Malaysia.
Export of NOy from the North American boundary layer during 1996 and 1997 North Atlantic Regional Experiments
Authors: Stohl Andreas , Trainer Michael , Ryerson Tom B. , Holloway John S. , Parrish David D.
Published: October 2002

This paper studies the removal timescales of the NOy originating from surface emissions of nitrogen oxides (NOx) and studies what fraction of the emissions reaches the free troposphere. These are important questions because NOx, which limits ozone production in the free troposphere, can be recycled from NOy after the primary NOx has been exhausted. We present an analysis of aircraft measurement data of odd nitrogen (NOy) and carbon monoxide (CO) taken during the North Atlantic Regional Experiment (NARE) in spring 1996 and fall 1997. Because CO has a relatively long chemical lifetime in the atmosphere and because it has similar emission patterns to NOx, CO concentrations can serve as a reference against which NOy removal can be studied. Correlating NOy and CO for different heights, we show that for the NARE 1997 (and NARE 1996) measurement campaigns, 78–91% (33–76%) of the surface NOy emissions were lost within the boundary layer or during transport from it, and only 3% (5%) of the emissions reached altitudes above 3 km. This accounted for ∼35% (∼41%) of the total NOy present above 3 km, the remainder coming from in situ emissions. In order to establish the timescales over which NOy is removed from the atmosphere, we determine the time elapsed between emission and measurement using a Lagrangian tracer transport model. We obtain approximate, effective mean e‐folding lifetimes of NOy of 1.7 (1.8) days for the two intensives. On average, only 4% (9%) of the NOy remains in the atmosphere after 4–5 days. After 5–6 days, NOy from anthropogenic surface sources has been further depleted and accounts for <50% of the observed NOy. The rest of the observed NOy must come from in situ emissions, not from anthropogenic surface emissions.
Eddy covariance measurements of nitric oxide flux within an Amazonian rain forest
Authors: Rummel, U. , Ammann, C. , Gut, A. , Meixner, F. X. , Andreae M. O.
Published: October 2002

NO flux measurements by the eddy covariance technique were performed within a tropical rain forest 1 m and 11 m above the forest floor. A fast‐response chemiluminescence NO analyzer with a sampling tube of 25 m length was used for the gas measurements. Nighttime similarity between the cospectra of sensible heat and the NO flux offered the possibility to quantify the high‐frequency attenuation of the NO eddy covariance by spectral analysis. Integrated flux correction factors of about 21% for the system at 1 m and 5% for the one at 11 m above ground were calculated by transfer functions adopted from the literature and confirmed experimentally. For an independent validation the results of the eddy covariance system were compared with the NO soil emissions obtained by dynamic chambers. For nighttime averages, good agreement within 10% was found. The obtained NO fluxes were 3.5 ± 0.14 and 4.8 ± 0.39 ng N m−2 s−1 for the two investigated periods at 1 and 11 m heights, respectively. During the day, chemical reaction with ozone entrained from aloft reduced the fraction of the soil‐emitted NO that reached the measuring height of the eddy covariance system. The average flux showed a reduction of 48% at 1 m and 92% at 11 m height compared to the corresponding soil emission measured by the chamber system.
NO emission from an Amazonian rain forest soil: Continuous measurements of NO flux and soil concentration
Authors: Gut A. , van Dijk S. M. , Scheibe M. , Rummel U. , Welling M. , Ammann C. , Meixner F. X. , Kirkman G. A. , Andreae M. O. , Lehmann B. E.
Published: October 2002

The net nitric oxide (NO) flux from the soil of a tropical rain forest site in Reserva Biologica Jaru (Rondônia, Brazil) was continuously measured in May and during September–November 1999 using dynamic chambers. The median net NO flux was 4.7 ng N m−2 s−1 in May (1000 individual measurements) and 4.0 ng N m−2 s−1 in September–November (4200 individual measurements). The daily variation of the net NO flux was positively correlated to the daily variations of soil temperature. Minor rain events (<10 mm) had no significant influence on the 24‐hour mean net NO flux. Following larger amounts of rain, a 40% reduction of the 24‐hour mean net NO flux up to a 150% increase was observed. During the September–November experiment the soil NO concentration and the soil NO bulk diffusion coefficient were measured to calculate the net NO flux using an indirect method. The soil NO concentration was continuously measured at 0.03‐m depth. It ranged from 20 to 460 ppb and was positively correlated with soil moisture and soil temperature. The soil bulk diffusion coefficient determined from 222Rn flux and soil‐air activity gradient measurements ranged from 2.7 × 10−7 to 9.1 × 10−7 m2 s−1 and was parameterized with soil air‐filled pore space. The median net NO flux calculated by the indirect method was 3.9 ng N m−2 s−1 (1600 individual measurements).
Biogeochemical cycling of carbon, water, energy, trace gases, and aerosols in Amazonia: The LBA‐EUSTACH experiments
Authors: Andreae M. O. , Artaxo P. , Brandão C. , Carswell F. E. , Ciccioli P. , da Costa A. L. , Culf A. D. , Esteves J. L. , Gash J. H. C. , Grace J. , Kabat P. , Lelieveld J. , Malhi Y. , Manzi A. O. , Meixner F. X. , Nobre A. D. , Nobre C. , Ruivo M. d. L. P. , Silva‐Dias M. A. , Stefani P. , Valentini R. , von Jouanne J. , Waterloo M. J.
Published: October 2002

The biogeochemical cycling of carbon, water, energy, aerosols, and trace gases in the Amazon Basin was investigated in the project European Studies on Trace Gases and Atmospheric Chemistry as a Contribution to the Large‐Scale Biosphere‐Atmosphere Experiment in Amazonia (LBA‐EUSTACH). We present an overview of the design of the project, the measurement sites and methods, and the meteorological conditions during the experiment. The main results from LBA‐EUSTACH are: Eddy correlation studies in three regions of the Amazon Basin consistently show a large net carbon sink in the undisturbed rain forest. Nitrogen emitted by forest soils is subject to chemical cycling within the canopy space, which results in re‐uptake of a large fraction of soil‐derived NOx by the vegetation. The forest vegetation is both a sink and a source of volatile organic compounds, with net deposition being particularly important for partially oxidized organics. Concentrations of aerosol and cloud condensation nuclei (CCN) are highly seasonal, with a pronounced maximum in the dry (burning) season. High CCN concentrations from biomass burning have a pronounced impact on cloud microphysics, rainfall production mechanisms, and probably on large‐scale climate dynamics.
Sulphur and oxygen isotope ratios in spruce needles as a tracer of atmospheric pollution
Authors: Jędrysek Mariusz Orion , Kalużny Adam , Hoefs Jochen
Published: October 2002

The biospheric part of the anthropogenic sulphur cycle was investigated in a heavily polluted area at the northern slope of the Karkonosze Mountains, SW Poland. Norway spruce (Picea abies) needles, from a 900 m vertical transect (400 to 1300 m above sea level), were collected on two consecutive days of spring 1998 and one day of winter 1999. Concentrations of sulphate sulphur (SO42−), and organic sulphur (Sorg)n and isotope ratios of organic sulphur and sulphate from spruce needles have been analyzed. (SO42−)n and (Sorg)n were rather constant and δ34S(SO42−)n and δ34S(Sorg)n values increased with higher altitude. This is attributed to an increase in atmospheric SO2 concentration and light intensity, which enhance emission of 34S‐depleted hydrogen sulphide (H2S) from needles. The δ18O(SO42−)n decreases with altitude due to the altitudinal 18O‐depletion of atmospheric precipitation and increased formation of needle sulphate from atmospheric SO2. The isotope effect related to a reduction process during spring can also be seen at higher altitudes by a negative correlation between δ18O(SO42−)n versus (SO42−)n and δ34S(SO42−)n versus (SO42−)n of spring needles. Winter needles show an opposite trend of potential oxidation of the SO2 assimilated. The Δ34S(SO42− − Sorg)n value shows a very good correlation to the abundance of dust on needles. Higher abundances of dust may limit foliar gas exchange and thus higher Δ34S(SO42− − Sorg)n values reflect conditions which are closer to sulphur isotope equilibrium in the sulphate‐organic sulphur system, whereas lower Δ34S(SO42− − Sorg)n values characterize a higher gas exchange rate and more dynamic conditions for the sulphur system in needles. Hydrogen sulphide emission is the most likely mechanism to control variations in the observed δ‐values, and dust abundance may control variations in the Δ‐values.
Plant physiological influences on the fluxes of oxygenated volatile organic compounds from ponderosa pine trees
Authors: Schade Gunnar W. , Goldstein Allen H.
Published: October 2002

Fluxes of oxygenated volatile organic compounds were measured above a ponderosa pine plantation, adjacent to the Blodgett Forest Research Station (38°53′42.9″N, 120°37′57.9″W, 1315 m elevation), with a fully automated relaxed eddy accumulation system coupled to a dual gas chromatograph‐flame ionization detector (GC‐FID) system. These measurements were initially reported by Schade and Goldstein [2001]. Here we further analyze these data to explore the physiological controls on emissions of 2‐methyl‐3‐buten‐2‐ol (MBO), ethanol, and acetaldehyde. Measured MBO fluxes were compared to fluxes predicted by a detailed leaf‐level emission model. Although the match was very good in general, the model failed to predict a declined emission potential on cooler days following a very cold night. It also consistently overpredicted fluxes in the morning, while underpredicting fluxes in the afternoon, particularly on warm days. We conclude that the ponderosa pine MBO emission potential changes in response to recent environmental temperatures on diurnal and daily timescales, similar to changes reported for isoprene emissions. Though ambient temperature appeared to be the most important driver of ethanol and acetaldehyde fluxes, vapor pressure deficit strongly influenced ethanol emissions from ponderosa pine, suggesting that stomatal opening impacts emissions. Ethanol emissions were also found to increase after high ozone deposition fluxes, which supports the theory that ozone‐induced stress may trigger fermentation processes in the leaves.
Chemical depletion of Arctic ozone in winter 1999/2000
Authors: Rex M. , Salawitch R. J. , Harris N. R. P. , von der Gathen P. , Braathen G. O. , Schulz A. , Deckelmann H. , Chipperfield M. , Sinnhuber B.‐M. , Reimer E. , Alfier R. , Bevilacqua R. , Hoppel K. , Fromm M. , Lumpe J. , Küllmann H. , Kleinböhl A. , Bremer H. , von König M. , Künzi K. , Toohey D. , Vömel H. , Richard E. , Aikin K. , Jost H. , Greenblatt J. B. , Loewenstein M. , Podolske J. R. , Webster C. R. , Flesch G. J. , Scott D. C. , Herman R. L. , Elkins J. W. , Ray E. A. , Moore F. L. , Hurst D. F. , Romashkin P. , Toon G. C. , Sen B. , Margitan J. J. , Wennberg P. , Neuber R. , Allart M. , Bojkov B. R. , Claude H. , Davies J. , Davies W. , De Backer H. , Dier H. , Dorokhov V. , Fast H. , Kondo Y. , Kyrö E. , Litynska Z. , Mikkelsen I. S. , Molyneux M. J. , Moran E. , Nagai T. , Nakane H. , Parrondo C. , Ravegnani F. , Skrivankova P. , Viatte P. , Yushkov V.
Published: October 2002

During Arctic winters with a cold, stable stratospheric circulation, reactions on the surface of polar stratospheric clouds (PSCs) lead to elevated abundances of chlorine monoxide (ClO) that, in the presence of sunlight, destroy ozone. Here we show that PSCs were more widespread during the 1999/2000 Arctic winter than for any other Arctic winter in the past two decades. We have used three fundamentally different approaches to derive the degree of chemical ozone loss from ozonesonde, balloon, aircraft, and satellite instruments. We show that the ozone losses derived from these different instruments and approaches agree very well, resulting in a high level of confidence in the results. Chemical processes led to a 70% reduction of ozone for a region ∼1 km thick of the lower stratosphere, the largest degree of local loss ever reported for the Arctic. The Match analysis of ozonesonde data shows that the accumulated chemical loss of ozone inside the Arctic vortex totaled 117 ± 14 Dobson units (DU) by the end of winter. This loss, combined with dynamical redistribution of air parcels, resulted in a 88 ± 13 DU reduction in total column ozone compared to the amount that would have been present in the absence of any chemical loss. The chemical loss of ozone throughout the winter was nearly balanced by dynamical resupply of ozone to the vortex, resulting in a relatively constant value of total ozone of 340 ± 50 DU between early January and late March. This observation of nearly constant total ozone in the Arctic vortex is in contrast to the increase of total column ozone between January and March that is observed during most years.
Continuous day and night aerosol optical depth observations in the Arctic between 1991 and 1999
Authors: Herber Andreas , Thomason Larry W. , Gernandt Hartwig , Leiterer Ulrich , Nagel Dagmar , Schulz Karl‐Heinz , Kaptur Jasmine , Albrecht Torsten , Notholt Justus
Published: October 2002

Ground‐based measurements of total aerosol optical depth (AOD), e.g., tropospheric and stratospheric aerosol, have been established at the Koldewey station in Ny‐Ålesund, Spitzbergen (Norway, 78.95°N, 11.93°E), since 1991. The basic instrumentation is a multichannel photometer using sunlight. New instruments have been developed to extend the measurement period to polar night. The new instruments are a Sun and Moon photometer (1995) and a star photometer (1996). The instruments and applied methods for aerosol optical depth retrieval for Sun, Moon, and star measurements are briefly discussed. The year‐round measurements made it possible to study in detail the interannual and seasonal variations of total AOD in the Arctic. The seasonal variation and the long‐term trend of tropospheric aerosol optical depth are discussed, taking into account the stratospheric AOD measured by the Stratospheric Aerosol and Gas Experiment (SAGE II). The lowest tropospheric aerosol optical depth values occur in late summer and fall. Each year, strong Arctic haze events were recorded not only during spring but also in late winter as the first star photometer measurements clearly show. Five‐day backward trajectories were used to analyze possible sources for high tropospheric AOD. Elevated tropospheric aerosol optical depth appears for northeasterly, easterly, or westerly winds. Finally, the long‐term changes of tropospheric AOD have been assessed. A small positive trend of the tropospheric aerosol optical depth is found for the vicinity of Spitzbergen during the measurement period.
Diagnosing ozone loss in the extratropical lower stratosphere
Authors: Lee Adrian M. , Jones Roderic L. , Kilbane‐Dawe Iarla , Pyle John A.
Published: October 2002

Chemical ozone loss in the Southern Hemisphere lower stratosphere during winter and spring 1996 is investigated using a three‐dimensional chemical transport model. Model diagnostic quantities are developed to determine the underlying chemical mechanisms controlling the distribution of ozone. These diagnostic tracers quantify the ozone change due to individual catalytic cycles or reaction mechanisms that form or destroy ozone. Results from these tracers confirm the importance of halogens not only in the development of the ozone hole but also in midlatitude ozone depletion of which almost 50% is due to cycles involving halogens. The dominant chemical ozone loss mechanism in the middle latitudes is due to the cycle whose rate determining step involves the bimolecular collision between HO2 and O3. Observational evidence from ozonesonde measurements shows substantial ozone depletion in the polar subvortex region (altitudes below ∼14 km). These measurements also indicate that this ozone depletion must be due, at least in part, to in situ chemical ozone loss. Model results show that over a quarter of the ozone depletion associated with the ozone hole resides at subvortex altitudes. Diagnostic tracers designed to quantify ozone loss occurring above and below the subvortex transition altitude show that the majority of this ozone depletion is in situ ozone loss. Furthermore, at altitudes below the subvortex transition, polar ozone loss is efficiently transported to middle latitudes, where it contributes to midlatitude ozone decline.
Observations of the quasi‐2‐day wave in the mesosphere and lower thermosphere over Yamagawa and Wakkanai
Authors: Namboothiri S. P. , Kishore P. , Igarashi K.
Published: October 2002

Mesospheric/lower thermospheric (MLT) winds observed at Yamagawa (31.2°N, 130.6°E) and Wakkanai (45.4°N, 141.7°E), using the spaced‐antenna technique, have been analyzed to study features of the quasi‐2‐day oscillations. We have used 4–5 years (1996–2000) of near‐continuous data for the analysis. Our results are consistent with the reports at other midlatitude sites. The analysis reveals that the wave features observed at these two stations are similar. The occurrence of the wave event (probably the same) is seen at both stations during the same days. The wave is found every year with the maximum amplitude in the summer months. The meridional component has larger amplitudes than the zonal component. Comparing the amplitudes at the two stations, we find that the values observed at Yamagawa are larger than those at Wakkanai. The amplitude appears to attain its maximum value at around 90 km at both stations. Substantial year‐to‐year variations are observed in the 2‐day wave amplitude. The average wave period observed at Yamagawa and Wakkanai is approximately 48 hours. The study also explores the dependence of the 2‐day wave on the background atmospheric circulation. However, further analysis on wave events is needed to obtain a better understanding of this aspect. The results of the present study are also compared with the earlier meteor radar observations in Kyoto, Japan, and some other midlatitude observations. Further coordinated studies are suggested to investigate horizontal structure and generating mechanism of the 2‐day wave.
Secondary organic aerosol 1. Atmospheric chemical mechanism for production of molecular constituents
Authors: Griffin Robert J. , Dabdub Donald , Seinfeld John H.
Published: October 2002

This series of three papers addresses the representation of secondary organic aerosol (SOA) in atmospheric models. SOA forms when gas‐phase organic species undergo oxidation, leading to products of sufficiently low vapor pressure that can partition between the gas and aerosol phases. The present paper, part 1, is devoted to the development of a gas‐phase atmospheric chemical mechanism designed to represent ozone chemistry as well as formation of individual organic oxidation products that are capable of forming SOA. The ozone chemistry in the mechanism draws upon the recent work of Stockwell et al. [1997] and Jenkin et al. [1997] and SAPRC‐97 and SAPRC‐99 (available from W.P.L. Carter at http://helium.ucr.edu/~carter/). The mechanism is evaluated in the three‐dimensional California Institute of Technology (CIT) model [Meng et al., 1998] by simulating gas‐phase concentrations in the South Coast Air Basin (SoCAB) of California over the period 27–29 August 1987. Total predicted concentrations of gas‐phase SOA compounds are compared with levels of SOA that have been inferred on the basis of ambient organic aerosol measurements during this period. These predicted concentrations indicate that the total gas‐phase potential of SOA‐forming compounds can account for observed aerosol concentrations. Part 2 develops a thermodynamic gas–aerosol partitioning module, and part 3 presents a full three‐dimensional simulation of gas and aerosol levels in the SoCAB during a 1993 episode.
Secondary organic aerosol 3. Urban/regional scale model of size‐ and composition‐resolved aerosols
Authors: Griffin Robert J. , Dabdub Donald , Kleeman Michael J. , Fraser Matthew P. , Cass Glen R. , Seinfeld John H.
Published: October 2002

The California Institute of Technology (CIT) three‐dimensional urban/regional atmospheric model is used to perform comprehensive gas‐ and aerosol‐phase simulations of the 8 September 1993 smog episode in the South Coast Air Basin of California (SoCAB) using the atmospheric chemical mechanism of part 1 [Griffin et al., 2002] and the thermodynamic module of part 2 [Pun et al., 2002]. This paper focuses primarily on simulations of secondary organic aerosol (SOA) and determination of the species and processes that lead to this SOA. Meteorological data and a gas and particulate emissions inventory for this episode were supplied directly by the South Coast Air Quality Management District. A summer 1993 atmospheric sampling campaign provides data against which the performance of the model is evaluated. Predictions indicate that SOA formation in the SoCAB is dominated by partitioning of hydrophobic secondary products of the oxidation of anthropogenic organics. The biogenic contribution to total SOA increases in the more rural eastern portions of the region, as does the fraction of hydrophilic SOA, the latter reflecting the increasing degree of oxidation of SOA species with atmospheric residence time.
Ozone depletion observed by the Airborne Submillimeter Radiometer (ASUR) during the Arctic winter 1999/2000
Authors: Bremer Holger , von König M. , Kleinböhl A. , Küllmann H. , Künzi K. , Bramstedt K. , Burrows J. P. , Eichmann K.‐U. , Weber M. , Goede A. P. H.
Published: October 2002

In the winter 1999/2000 the Airborne Submillimeter Radiometer (ASUR) participated in the Stratospheric Aerosol and Gas Experiment III Ozone Loss and Validation Experiment/Third European Stratospheric Experiment on Ozone project on board the NASA research aircraft DC‐8. During three deployments in early December 1999, late January, and early March 2000, the ASUR instrument took various measurements of ozone and key species related to stratospheric ozone chemistry. After the sunlight reached the vortex region in January 2000 peak values of about 1.8 ppb ClO were measured by ASUR. There was nearly no ozone destruction observed during the period between mid December 1999 and late January 2000. As expected from ASUR observation of high chlorine activation and continuously low temperatures until mid March, significant ozone depletion was observed between late January and mid March 2000. In order to determine ozone loss it is important to separate dynamical and chemical effects. Since N2O is a good tracer due to its chemical stability in the lower stratosphere for determining ozone changes due to descent of air, ozone loss can be estimated from simultaneous measurements of ozone and N2O by ASUR. Between mid December 1999 and mid March 2000 a chemical ozone loss of about 30% (eq 1.1 ppm) in the altitude range between 19.0 and 22.2 km and of about 40% (eq 1.15 ppm) between 16.0 and 18.1 km was observed. The air masses subsided 2.1–3.2 km in the lower stratosphere due to diabatic descent in the period from mid December 1999 to mid March 2000 as derived from ASUR N2O measurements. Vortex‐averaged ASUR measurements of ozone are systematical greater than results from the Global Ozone Monitoring Experiment (GOME) which has a similar vertical resolution than ASUR. This, however, has little impact on the determination of delta ozone and chemical loss estimates.
Studies of Peroxyacetyl nitrate (PAN) and its interaction with the snowpack at Summit, Greenland
Authors: Ford Kevin M. , Campbell Bradley M. , Shepson Paul B. , Bertman Steven B. , Honrath Richard E. , Peterson Matt , Dibb Jack E.
Published: October 2002

Peroxyacetyl nitrate (PAN) was measured in ambient and snowpack interstitial air at Summit, Greenland, in June and July of 1998 and 1999 and at a rural/forest site in the Keewenaw Peninsula of Michigan in January of 1999. At Summit, we found that PAN typically represented between 30 and 60% of NOy. In the summer of 1999, a significant diel variation in both PAN/NOy and NOx/NOy was observed, but this was much less pronounced in 1998. Experiments during SNOW99 near Houghton, Michigan, indicated that PAN undergoes weak uptake onto snow grain surfaces. At Summit, we found that PAN concentrations in the snowpack interstitial air were significantly elevated (by as much as 2–5 times) relative to ambient levels, implying a flux of PAN out of the snowpack during the study period. We also observed evidence that PAN can be photochemically produced in snow that is exposed to polluted air. These observations indicate that interactions with the snowpack can have a significant impact on PAN concentrations in the boundary layer and point to potential difficulties associated with investigation of long‐term changes in PAN uptake into ice cores because of the impact of postdepositional processes.
Organic compounds in urban aerosols from Gent, Belgium: Characterization, sources, and seasonal differences
Authors: Kubátová Alena , Vermeylen Reinhilde , Claeys Magda , Cafmeyer Jan , Maenhaut Willy
Published: October 2002

About 100 individual organic compounds were determined in urban aerosols collected at Gent, Belgium. The compounds were identified by gas chromatography–mass spectrometry, and quantitative data were obtained by gas chromatography–flame ionization detection. Measurements of the particulate mass and of organic and elemental carbon mass were also made. Aerosol samples from a winter and a summer campaign were analyzed in order to examine seasonal differences. The major part of the extractable and elutable organic carbon in both winter and summer aerosols was found to correspond to an unresolved complex mixture that is typical for car exhaust. The prevailing resolved organic compounds in both seasons were n‐alkanes and fatty acids, but the distribution patterns of individual components within each class showed seasonal differences. The n‐alkane pattern for summer aerosols was clearly affected by emissions from the vegetation, while that of fatty acids revealed a lower relative abundance of unsaturated fatty acids in summer than winter that can be related to more extensive atmospheric oxidation of unsaturated fatty acids during summer. Concentrations of dicarboxylic acids and related products that are believed to be oxidation products of hydrocarbons and fatty acids were highest in summer aerosols. Some individual compounds in the latter class could only be detected in summer samples and showed the highest concentrations on hot summer days that were characterized by maximum temperatures above 25°C and increased ozone concentrations. The latter compounds included novel, recently identified glutaric acid derivatives, namely, 3‐isopropyl and 3‐acetyl pentanedioic acid, likely originating from atmospheric oxidation of reactive monoterpene or sesquiterpene precursors that still need to be identified. Several compounds were found that are markers of wood combustion, including diterpenoic acids, lignin pyrolysis products, and levoglucosan. The quantitative results obtained for diterpenoic acids and lignin pyrolysis products indicated that contributions from wood combustion are more important in winter than in summer. Evidence is presented that both softwood and hardwood burning contribute to the organic aerosol, but that hardwood burning prevails during winter. Polyaromatic hydrocarbons were also more prevalent in winter than in summer.
Solar influences on cosmic rays and cloud formation: A reassessment
Authors: Sun Bomin , Bradley Raymond S.
Published: October 2002

Svensmark and Friis‐Christensen [1997] proposed a “cosmic ray‐cloud cover” hypothesis that cosmic ray flux, modulated by solar activity, may modify global cloud cover and thus global surface temperature by increasing the number of ions in the atmosphere, leading to enhanced condensation of water vapor and cloud droplet formation. We evaluate this idea by extending their period of study and examining long‐term surface‐based cloud data (from national weather services and the Global Telecommunication System) as well as newer satellite data (International Satellite Cloud Climatology Project (ISCCP) D2, 1983–1993). No meaningful relationship is found between cosmic ray intensity and cloud cover over tropical and extratropical land areas back to the 1950s. The high cosmic ray‐cloud cover correlation in the period 1983–1991 over the Atlantic Ocean, the only large ocean area over which the correlation is statistically significant, is greatly weakened when the extended satellite data set (1983–1993) is used. Cloud cover data from ship observations over the North Atlantic, where measurements are denser, did not show any relationship with solar activity over the period 1953–1995, though a large discrepancy exists between ISCCP D2 data and surface marine observations. Our analysis also suggests that there is not a solid relationship between cosmic ray flux and low cloudiness as proposed by Marsh and Svensmark [2000].
NOx versus VOC limitation of O3 production in the Po valley: Local and integrated view based on observations
Authors: Spirig Christoph , Neftel Albrecht , Kleinman Lawrence I. , Hjorth Jens
Published: October 2002

We characterize the local O3 production at an urban and a rural site in the northern part of the Po valley (Italy) during the Pianura Padana Produzione di Ozono experiment (PIPAPO). A steady state calculation based on observations is performed to determine the local O3 production rate, P(O3), and its sensitivity to precursor concentrations. The urban site exhibited a strongly VOC sensitive O3 production rate, while both VOC and NOx sensitive conditions were observed at the rural site. In addition to the local steady state analysis, we performed one‐dimensional Lagrangian model calculations that simulate conditions in the Po valley. These calculations show that the P(O3) at the surface tends to be more VOC sensitive than the average in the mixed layer. The Lagrangian calculations are also used to determine the response of O3 concentration to an emissions change. We compare emission control information with information on sensitivities from the local analysis. It is concluded that a local analysis of P(O3) within the mixing layer offers useful qualitative information but tends to overestimate VOC sensitivity as judged by a comparison with an emissions‐based Lagrangian model.
Comparison and evaluation of in situ and filter carbon measurements at the Fresno Supersite
Authors: Watson John G. , Chow Judith C.
Published: October 2002

The Fresno Supersite in Fresno, California, USA, acquires in situ 5‐ to 60‐min average PM2.5 organic carbon (OC), elemental carbon (EC), and total carbon (TC) measurements by the following methods: (1) thermal evolution carbon analyzer for organic, elemental, and total carbon; (2) single‐wavelength and seven‐color aethalometer for black carbon (BC); and (3) photoionization for particle‐bound polycyclic aromatic hydrocarbons. Twenty‐four‐hour average PM2.5 filter‐based measurements include (1) nondenuded quartz filters with no backup filter in a PM2.5 Federal Reference Method (FRM) sampler; (2) quartz filters behind an organic carbon denuder with a quartz backup filter in a Reference Ambient Aerosol Sampler (RAAS); (3) nondenuded quartz filters with backup filter in a RAAS; and (4) nondenuded quartz filters with no backup filter in a sequential filter sampler. Filter samples are analyzed after sampling by the Interagency Monitoring of Protected Visual Environments (IMPROVE) thermal/optical reflectance carbon analysis protocol. Collocated measurements are examined for year 2000. Measurement equivalence is found for PM2.5 mass, light transmission, and TC between the FRM and RAAS speciation samplers. The average ratios of front filter carbon between the denuded and nondenuded channels in the RAAS sampler are 0.83 ± 0.19 for TC, 0.81 ± 0.20 for OC, and 1.01 ± 0.33 for EC. The average differences for TC and OC are low (1.2 to 1.4 μg m‐3) and are comparable to the measurement uncertainties. Continuous thermal evolution carbon measurements are not comparable to filter measurements. Aethalometer BC and filter EC are highly correlated, but filter EC is consistently 20–25% higher than continuous aethalometer BC. Pairwise comparisons show filter EC measurements acquired in this study are predictable from aethalometer BC measurements.
Defining the polar vortex edge from an N2O:potential temperature correlation
Authors: Greenblatt Jeffery B. , Jost Hans‐Jürg , Loewenstein Max , Podolske James R. , Bui T. Paul , Hurst Dale F. , Elkins James W. , Herman Robert L. , Webster Christopher R. , Schauffler Sue M. , Atlas Elliot L. , Newman Paul A. , Lait Leslie R. , Müller Melanie , Engel Andreas , Schmidt Ulrich
Published: October 2002

A prerequisite to studying phenomena in the winter stratospheric polar vortex is the separation of measurements inside and outside the dynamical barrier of the vortex edge. We describe a technique to accurately determine the inner edge of the vortex boundary region from measurements of potential temperature and a trace gas, such as N2O, and apply it to in situ aircraft and balloon measurements from the SOLVE/THESEO 2000 Arctic campaign. The method may be used to refine the Nash algorithm, which, due to the inherently coarser resolution of potential vorticity on which it is dependent, may misidentify the inner edge by more than 400 km and omit the identification of small, extravortex filaments within the vortex.
Organic trace gas measurements by PTR‐MS during INDOEX 1999
Authors: Wisthaler Armin , Hansel Armin , Dickerson Russell R. , Crutzen Paul J.
Published: October 2002

A proton‐transfer‐reaction mass spectrometer (PTR‐MS) was used for fast‐response measurements of volatile organic compounds (VOCs) onboard the NOAA research vessel Ronald H. Brown during leg 2 (4 March–23 March) of the INDOEX 1999 cruise. In this paper, we present a first overview of the distribution of acetonitrile, methanol, acetone, and acetaldehyde over a broad spatial extent of the Indian Ocean (19°N–13°S, 67°E–75°E). The prevailing atmospheric circulation during the winter monsoon transported polluted air from India and the Middle East over the Indian Ocean to meet pristine southern hemispheric air at the intertropical convergence zone (ITCZ). The chemical composition of air parcels changed according to their geographic origin, which was traced by backtrajectory analysis. The relative abundance of acetonitrile, a selective tracer for biomass burning, to that of carbon monoxide, a general tracer for incomplete combustion, reflected the signature of biomass burning or fossil fuel combustion. This indicated a strong biomass burning impact in W‐India, mixed pollution sources in NE‐India, and the dominance of fossil fuel combustion in the Middle East. Biomass burning impacted air was rich in methanol (0.70–1.60 ppbv), while acetone (0.80–2.40 ppbv) and acetaldehyde (0.25–0.50 ppbv) were elevated in all continental air masses. Pollution levels decreased toward the ITCZ resulting in minima for methanol, acetone, and acetaldehyde of 0.50, 0.45, and 0.12 ppbv, respectively. The observed abundances suggest that there are unidentified sources of acetone and acetaldehyde in biomass burning impacted air masses and in remote marine air.
Middle atmosphere Kelvin waves observed in Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) 1 and 2 temperature and trace species
Authors: Smith A. K. , Preusse P. , Oberheide J.
Published: October 2002

A number of tropical perturbations that have all the characteristics of Kelvin waves are identified in temperature measurements from the two flights of the Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) instrument. The background wind conditions during the two flights were quite different due to the different phases of the quasi‐biennial oscillation (QBO), and there were differences in the Kelvin waves observed. During each flight, there were several different zonal wave numbers and/or frequencies present simultaneously. The observed waves conform well to theory. In particular, lower‐frequency waves are confined to the lower stratosphere, while higher‐frequency waves appear in the upper stratosphere and mesosphere; the waves are centered on the equator; and the frequency and structure satisfy the dispersion relation. Wave signals also appear in several stratospheric trace species: O3, CFC‐11 (CFCl3), HNO3, N2O, and CH4. The sense of the correlation of these trace species perturbations with temperature (negative for CFC‐11, N2O, and CH4; positive for lower stratospheric HNO3 and O3) confirms that vertical velocity is responsible for the perturbations. There is a shift in the relative phases as photochemical processes become more important with increasing altitude. Upper stratospheric ozone correlates negatively with temperature due to temperature‐dependent reaction rates that destroy ozone.
Validation of ILAS v5.2 data with FIRS‐2 balloon observations
Authors: Jucks K. W. , Johnson D. G. , Chance K. V. , Traub W. A. , Margitan J. M. , Stachnik R. , Sasano Y. , Yokota T. , Kanzawa H. , Shibasaki K. , Suzuki M. , Ogawa T.
Published: October 2002

Comparisons of remote sensing stratospheric mixing ratio profiles for O3, H2O, N2O, HNO3, and NO2 are shown between data (version 5.2) obtained by the Improved Limb Atmospheric Spectrometer (ILAS) on board the Japanese Advanced Earth Observing Satellite (ADEOS) and the Smithsonian Astrophysical Observatory far‐infrared spectrometer (FIRS)‐2 balloon‐borne spectrometer from a flight on 30 April 1997 originating in Fairbanks, Alaska. Submillimeter wave remote sensing and UV in situ observations of mixing ratios of O3 from Jet Propulsion Laboratory (JPL) instruments obtained on board the same balloon gondola are also used for comparison with ILAS mixing ratios of O3. The remote sensing balloon observations occurred roughly 5° latitude, and the in situ 2° latitude, north of the nearest ILAS observations and were taken between 0700 and 1300 local solar time (LST), while the ILAS data were taken at the previous local sunset (near 2100 LST). Back trajectories from the locations and times of balloon data sets to the prior local sunset were within 2° latitude and 10° longitude of the nearest ILAS occultation; the validation therefore effectively occurred in very nearly the same air mass as was observed with ILAS, and well within a 1‐day time interval. The mixing ratio profiles of all of the compared molecules (O3, HNO3, N2O, H2O, and NO2) agree to within the combined uncertainties with only minor systematic offsets.
Biogenic iodine emissions and identification of end‐products in coastal ultrafine particles during nucleation bursts
Authors: Mäkelä J. M. , Hoffmann T. , Holzke C. , Väkevä M. , Suni T. , Mattila T. , Aalto P. P. , Tapper U. , Kauppinen E. I. , O'Dowd C. D.
Published: October 2002

Ultrafine particles sampled during new particle formation bursts observed in the coastal zone were studied with transmission electron microscopy (TEM) and elemental analysis using energy‐dispersive X ray (EDX). It was observed that both iodine and sulphur were present in the new particles with diameter below 10 mn. Gaseous emissions of halogen compounds from seaweeds were also measured at the same location during low‐tide particle nucleation episodes. Based on the presence of iodine in the particle phase during low‐tide nucleation bursts, and the significant emission of iodine compounds from the seaweeds during these periods, it is apparent that part of the biogenic iodine species emitted from the seaweeds end up in the ultrafine particulate phase. It was not possible to quantitatively determine the iodine content in the particles; however, in most cases the relative contribution from iodine and sulphate was similar, while some cases indicated no sulphate. On larger sized particles the contribution of sulphate was significantly higher than iodine. It appears that the condensable species leading to the appearance of new particles in the coastal atmosphere is an iodine species. Whether or not this iodine species also participates in the nucleation of new stable clusters could not be completely verified.
Sensitivity of CCN spectra on chemical and physical properties of aerosol: A case study from the Amazon Basin
Authors: Roberts Gregory C. , Artaxo Paulo , Zhou Jingchuan , Swietlicki Erik , Andreae Meinrat O.
Published: October 2002

Organic material, about half of which is water soluble, constitutes nearly 80% of the wet‐season aerosol mass in the Amazon Basin, while soluble inorganic salts (predominantly ammonium bisulfate) represent about 15%. A detailed analysis of number distributions and the size‐dependent chemical composition of the aerosol indicates that, in principle, the sulfate fraction could account for most of the cloud condensation nuclei (CCN) activity. Uncertainty about the chemical speciation of the water‐soluble organic component precludes a rigorous analysis of its contribution to nucleation activity. Within reasonable assumptions, we can, however, predict a similar contribution of the organic component to CCN activity as that from sulfate. Because of the nonlinear dependence of droplet nucleation behavior on solute amount, the nucleation activity cannot be attributed uniquely to the inorganic or organic fractions. The role of water‐soluble organic compounds as surfactants, however, may be significant (especially in the case of biomass‐burning aerosol) and more field measurements are needed to quantify their effects on the surface tension of ambient aerosols. The parametric dependence of the CCN spectra on the physical and chemical properties of the aerosol show that the number distribution, soluble content of the aerosol, and surface tension effects all play an important role in determining CCN spectra.
Temporal development of total chlorine in the high‐latitude stratosphere based on reference distributions of mean age derived from CO2 and SF6
Authors: Engel Andreas , Strunk Martin , Müller Melanie , Haase Hans‐Peter , Poss Christian , Levin Ingeborg , Schmidt Ulrich
Published: October 2002

We present balloon‐borne observations of CO2 and SF6 and derived vertical profiles of mean age for polar winter (inside vortex) and for midlatitude (nonwinter) conditions. For SF6‐derived mean ages above 5 years a mesospheric SF6 sink may lead to an overestimation of mean age, while for younger mean ages (below 2 years) the seasonal cycle of CO2 may influence the mean age determination based on CO2. We suggest that SF6 be used as an age tracer in the lower part of the stratosphere (i.e., for low mean age), whereas CO2 will be the better age tracer for older air. The mean age distributions together with an estimate of the width of the age spectrum are used to estimate the stratospheric chlorine loading. On the basis of an emission scenario and the lifetimes of chlorine‐containing compounds we estimate the future stratospheric chlorine loading. Inside the polar vortex, at an altitude of 20 km, we expect total chlorine to return to the values present in this region in 1980, when the ozone hole first appeared, around the year 2060. This estimate is based on the assumption that the general transport characteristics will not change over the period of the analysis and can thus be regarded as a best estimate based on stationary transport, the assumed set of lifetimes and emissions, and the mean age distribution derived from our measurements. As other factors influencing ozone may undergo temporal changes, this does not mean that ozone will necessarily recover at this time. While total chlorine is probably a good proxy for inorganic chlorine at altitudes above 20 km inside the polar vortex, the changing halocarbon mix may actually lead to an earlier return of inorganic chlorine to pre‐ozone‐hole values at lower altitudes.
Potential for estimating cloud liquid water path over sea ice from airborne passive microwave measurements
Authors: Haggerty Julie A. , Curry Judith A. , Liu Guosheng
Published: October 2002

In this paper we investigate the feasibility of determining cloud liquid water path from passive microwave measurements over sea ice. Simulations using a 32‐stream plane‐parallel microwave radiative transfer model indicate a consistent increase in brightness temperature attributable to cloud liquid water for conditions observed in the Arctic during the Surface Heat Budget of the Arctic (SHEBA) experiment. Uncertainties in brightness temperature simulations due to variations in surface emissivity, surface temperature, cloud temperature, and atmospheric water vapor are investigated. Surface emissivity variations are found to cause the largest uncertainties in top‐of‐atmosphere brightness temperature over the range of liquid water paths examined. An algorithm previously developed for estimating liquid water path over oceans from SSM/I data is adapted for retrievals over sea ice. The algorithm is applied to brightness temperature measurements from airborne microwave radiometers. Mean retrieved liquid water path (LWP) is compared to in situ measurements from airborne cloud microphysical probes. The correlation coefficient for the two data sets is found to be 0.989 with an RMS error of 14 g m−2, although the retrieved LWP values show a high degree of variability. Accuracy is highest when LWP values are 100 g m−2 and above. Poorest accuracies are obtained for small LWP (<50 g m−2) where errors in the specification of surface emissivity have a large effect. These case studies provide evidence that liquid water clouds over sea ice produce detectable changes in microwave brightness temperature and suggest that interpretation of sea ice properties using certain microwave frequencies may be affected by the presence of liquid water clouds.