bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of on-road vehicle emissions in the Mexico City Metropolitan Area using a mobile laboratory in chase and fleet average measurement modes during the MCMA-2003 field campaign
Authors: Zavala M. , Herndon S. C. , Slott R. S. , Dunlea E. J. , Marr L. C. , Shorter J. H. , Zahniser M. , Knighton W. B. , Rogers T. M. , Kolb C. E. , Molina L. T. , Molina M. J. 
Published: April 2010

Abstract. A mobile laboratory was used to measure on-road vehicle emission ratios during the MCMA-2003 field campaign held during the spring of 2003 in the Mexico City Metropolitan Area (MCMA). The measured emission ratios represent a sample of emissions of in-use vehicles under real world driving conditions for the MCMA. From the relative amounts of NOx and selected VOC's sampled, the results indicate that the technique is capable of differentiating among vehicle categories and fuel type in real world driving conditions. Emission ratios for NOx, NOy, NH3, H2CO, CH3CHO, and other selected volatile organic compounds (VOCs) are presented for chase sampled vehicles in the form of frequency distributions as well as estimates for the fleet averaged emissions. Our measurements of emission ratios for both CNG and gasoline powered "colectivos" (public transportation buses that are intensively used in the MCMA) indicate that – in a mole per mole basis – have significantly larger NOx and aldehydes emissions ratios as compared to other sampled vehicles in the MCMA. Similarly, ratios of selected VOCs and NOy showed a strong dependence on traffic mode. These results are compared with the vehicle emissions inventory for the MCMA, other vehicle emissions measurements in the MCMA, and measurements of on-road emissions in U.S. cities. We estimate NOx emissions as 100 600±29 200 metric tons per year for light duty gasoline vehicles in the MCMA for 2003. According to these results, annual NOx emissions estimated in the emissions inventory for this category are within the range of our estimated NOx annual emissions. Our estimates for motor vehicle emissions of benzene, toluene, formaldehyde, and acetaldehyde in the MCMA indicate these species are present in concentrations higher than previously reported. The high motor vehicle aldehyde emissions may have an impact on the photochemistry of urban areas.
A model of HDO in the tropical tropopause layer
Authors: Dessler A. E. , Sherwood S. C. 
Published: April 2010

Abstract. Any theory of water vapor in the tropical tropopause layer (TTL) must explain both the abundance and isotopic composition of water there. In a previous paper, we presented a model of the TTL that simulated the abundance of water vapor as well as the details of the vertical profile. That model included the effects of "overshooting" convection, which injects dry air directly into the TTL. Here, we present results for the model after modifying it to include water's stable isotopologue HDO (where D represents deuterium, 2H). We find that the model predicts a nearly uniform HDO depletion throughout the TTL, in agreement with recent measurements. This occurs because the model dehydrates by dilution, which does not fractionate, instead of by condensation. Our model shows that this dehydration by dilution is consistent with other physical constraints on the system. We also show the key role that lofted ice plays in determining the abundance of HDO in the TTL. Such lofted ice requires a complementary source of dry air in the TTL; without that, the TTL will rapidly saturate and the lofted ice will not evaporate.
Effects of the physical state of tropospheric ammonium-sulfate-nitrate particles on global aerosol direct radiative forcing
Authors: Martin S. T. , Hung H.-M. , Park R. J. , Jacob D. J. , Spurr R. J. D. , Chance K. V. , Chin V. 
Published: April 2010

Abstract. The effect of aqueous versus crystalline sulfate-nitrate-ammonium tropospheric particles on global aerosol direct radiative forcing is assessed. A global three-dimensional chemical transport model predicts sulfate, nitrate, and ammonium aerosol mass. An aerosol thermodynamics model is called twice, once for the upper side (US) and once for lower side (LS) of the hysteresis loop of particle phase. On the LS, the sulfate mass budget is 40% solid ammonium sulfate, 12% letovicite, 11% ammonium bisulfate, and 37% aqueous. The LS nitrate mass budget is 26% solid ammonium nitrate, 7% aqueous, and 67% gas-phase nitric acid release due to increased volatility upon crystallization. The LS ammonium budget is 45% solid ammonium sulfate, 10% letovicite, 6% ammonium bisulfate, 4% ammonium nitrate, 7% ammonia release due to increased volatility, and 28% aqueous. LS aerosol water mass partitions as 22% effloresced to the gas-phase and 78% remaining as aerosol mass. The predicted US/LS global fields of aerosol mass are employed in a Mie scattering model to generate global US/LS aerosol optical properties, including scattering efficiency, single scattering albedo, and asymmetry parameter. Global annual average LS optical depth and mass scattering efficiency are, respectively, 0.023 and 10.7 m2 (g SO42−)−1, which compare to US values of 0.030 and 13.9 m2 (g SO42−)−1. Radiative transport is computed, first for a base case having no aerosol and then for the two global fields corresponding to the US and LS of the hysteresis loop. Regional, global, seasonal, and annual averages of top-of-the-atmosphere aerosol radiative forcing on the LS and US (FL and FU, respectively, in W m2−) are calculated. Including both anthropogenic and natural emissions, we obtain global annual averages of FL = −0.750, FU = −0.930, and ΔFU,L = 24% for full sky calculations without clouds and FL = −0.485, FU = −0.605, and ΔFU,L = 25% when clouds are included. Regionally, ΔFU,L = 48% over the USA, 55% over Europe, and 34% over East Asia. Seasonally, ΔFU,L varies from 18% in DJF to 75% in SON over the USA. The global annual average contribution from anthropogenic aerosol is FL = −0.314 and FU = −0.404, which yield normalized direct radiative forcings (G) of GL = −205 W (g SO42−)−1 and GU = −264 W (g SO42−)−1.
Problems regarding the tropospheric O&lt;sub&gt;3&lt;/sub&gt; residual method and its interpretation in Fishman et al. (2003)
Authors: de Laat A. D. J. , Aben I. 
Published: April 2010

Abstract. In this article we will show that the Total Ozone Residuals (TOR) method as presented by Fishman et al. (2003) contains an erroneous assumption, due to which the TOR as presented in this article reflects mainly a tropospheric O3 climatology (Logan, 1999), scaled to the layer between the surface and the tropopause height, rather than a satellite measured TOR. We will show that it is possible to obtain a tropospheric O3 column that is very similar to what is being presented in Fishman et al. (2003), solely based on the Logan (1999) tropospheric O3 climatology and an estimate for the tropopause heights without using satellite data. Furthermore, we will show that one of the interpretations of observed O3 variability (high TOR values over Southeast Asia) is not the result of pollution, but primarily of tropopause height variations. We suggest adjusting the method in such a way that the final retrieved TOR product becomes independent of the actual values of the Logan (1999) O3 climatology. The proposed adjustments are also more in line with the original methodology suggested by Fishman and Balok (1999) in a previous paper. We furthermore show that the assumption that the stratospheric O3 column is nearly constant within a 5-day period is not always valid. This can introduce errors in the final TOR product, although we recognize that these errors may become small when averaging the TOR product over longer periods of time. However, we feel that a detailed study on this assumption is also needed.
Sulphuric acid closure and contribution to nucleation mode particle growth
Authors: Boy M. , Kulmala M. , Ruuskanen T. M. , Pihlatie M. , Reissell A. , Aalto P. P. , Keronen P. , Dal Maso M. , Hellen H. , Hakola H. , Jansson R. , Hanke M. , Arnold F. 
Published: April 2010

Abstract. Sulphuric acid concentrations were measured and calculated based on pseudo steady state model with corresponding measurements of CO, NOx, O3, SO2, methane and non-methane hydrocarbon (NMHC) concentrations as well as solar spectral irradiance and particle number concentrations with size distributions. The measurements were performed as a part of the EU project QUEST (Quantification of Aerosol Nucleation in the European Boundary layer) during an intensive field campaign, which was conducted in Hyytiälä, Finland in March–April 2003. In this paper, the closure between measured and calculated H2SO4 concentrations is investigated. Besides that, also the contribution of sulphuric acid to nucleation mode particle growth rates is studied. Hydroxyl and hydroperoxy radical concentrations were determined using a pseudo steady state box model including photo stationary states. The maximum midday OH concentrations ranged between 4.1×105 to 1.8×106molecules cm−3 and the corresponding values for HO2 were 1.0×107 to 1.5×108molecules cm−3. The dominant source term for hydroxyl radicals is the reaction of NO with HO2 (56%) and the reaction of CO with OH covers around 41% of the sinks. The sulphuric acid source term is the reaction SO2 with OH and the sink term is condensation of sulphuric acid. The closure between measured and calculated sulphuric acid concentrations is achieved with a high agreement to the measured values. In sensitivity studies, we used different values for the non-methane hydrocarbons, the peroxy radicals and nitrogen dioxide. The best fits between calculated and measured values were found by decreasing the NO2 concentration when it exceeded values of 1.5 ppb and doubling the non-methane hydrocarbon concentrations. The ratio, standard deviation and correlation coefficient between measured and calculated sulphuric acid concentrations are 0.99, 0.412 and 0.645, respectively. The maximum midday sulphuric acid concentrations varied between 3×105 to 1.9×107molecules cm−3 for the measurements and 3×105 to 1.4×107molecules cm−3 for the calculations, respectively. An average participation of sulphuric acid to the nucleation mode particle growth rates is 8.8%. Classifying the days into two groups – "polluted" days with air masses originated over Central Europe or UK, and "cleaner" days with air masses originated over the Northern Atlantic or the Polar regions – reflects an equal sulphuric acid contribution to the aerosol growth in both air mass classes.
Temperature and light dependence of the VOC emissions of Scots pine
Authors: Tarvainen V. , Hakola H. , Hellén H. , Bäck J. , Hari P. , Kulmala M. 
Published: April 2010

Abstract. The volatile organic compound (VOC) emission rates of Scots pine (Pinus sylvestris L.) were measured from trees growing in a natural forest environment at two locations in Finland. The emission rate measurements were carried out using a dynamic flow through technique with samples collected on adsorbent tubes and analyzed using thermodesorption followed by a gas chromatograph with a mass-selective detector (GC-MS). The standard emission potentials (at 303.15 K and 1000 µmol photons m−2 s−1) were calculated for the measured compounds using nonlinear regression to fit the experimental data to temperature and light dependent emission algorithms. The observed total VOC emission rates varied between 21 and 874 ng/g(dw)*h and 268 and 1670 ng/g(dw)*h in southern and northern Finland, respectively. A clear seasonal cycle was detected with high emission rates in early spring, a decrease of the emissions in late spring and early summer, high emissions again in late summer, and a gradual decrease in autumn. The main emitted compounds were Δ3-carene (southern Finland) and α- and β-pinene (northern Finland), with approximate relative contributions of 60–70% and 60–85% of the total observed monoterpene emission rates, respectively. Sesquiterpene (β-caryophyllene) and 2-methyl-3-buten-2-ol (MBO) emissions were initiated in early summer at both sites. The observed MBO emission rates were between 1 and 3.5% of the total monoterpene emission rates. The sesquiterpene emission rates varied between 2 and 5% of the total monoterpene emission rates in southern Finland, but were high (40%) in northern Finland in spring. Most of the measured emission rates were found to be well described by the temperature dependent emission algorithm. The calculated standard emission potentials were high in spring and early summer, decreased somewhat in late summer, and were high again towards autumn. The experimental coefficient β ranged from 0.025 to 0.19 (average 0.10) in southern Finland, with strongest temperature dependence in spring and weakest in late summer. Only the emission rates of 1,8-cineole were found to be both light and temperature dependent. However, there were irregularities with the performance of the exponential temperature algorithm, and our results suggest that especially during the spring recovery period of the vegetation there may be several different processes contributing to the VOC emissions of Scots pine.
Column ozone and aerosol optical properties retrieved from direct solar irradiance measurements during SOLVE II
Authors: Swartz W. H. , Yee J.-H. , Shetter R. E. , Hall S. R. , Lefer B. L. , Livingston J. M. , Russell P. B. , Browell E. V. , Avery M. A. 
Published: April 2010

Abstract. Direct observation of the Sun at large solar zenith angles during the second SAGE III Ozone Loss and Validation Experiment (SOLVE II)/Validation of International Satellites and study of Ozone Loss (VINTERSOL) campaign by several instruments provided a rich dataset for the retrieval and analysis of line-of-sight column composition, intercomparison, and measurement validation. A flexible, multi-species spectral fitting technique is presented and applied to spectral solar irradiance measurements made by the NCAR Direct beam Irradiance Atmospheric Spectrometer (DIAS) on-board the NASA DC-8. The approach allows for the independent retrieval of O3, O2·O2, and aerosol optical properties, by constraining Rayleigh extinction. We examine the 19 January 2003 and 6 February 2003 flights and find very good agreement of O3 and O2·O2 retrievals with forward-modeling calculations, even at large solar zenith angles, where refraction is important. Intercomparisons of retrieved ozone and aerosol optical thickness with results from the Ames Airborne Tracking Sunphotometer (AATS-14) are summarized.
Implementation issues in chemistry and transport models
Authors: Strahan S. E. , Polansky B. C. 
Published: April 2010

Abstract. Offline chemistry and transport models (CTMs) are versatile tools for studying composition and climate issues requiring multi-decadal simulations. They are computationally fast compared to coupled chemistry climate models, making them well-suited for integrating sensitivity experiments necessary for understanding model performance and interpreting results. The archived meteorological fields used by CTMs can be implemented with lower horizontal or vertical resolution than the original meteorological fields in order to shorten integration time, but the effects of these shortcuts on transport processes must be understood if the CTM is to have credibility. In this paper we present a series of CTM experiments, each differing from another by a single feature of the implementation. Transport effects arising from changes in resolution and model lid height are evaluated using process-oriented diagnostics that intercompare CH4, O3, and age tracer carried in the simulations. Some of the diagnostics used are derived from observations and are shown as a reality check for the model. Processes evaluated include the tropical ascent, tropical-midlatitude exchange, the poleward circulation in the upper stratosphere, and the development of the Antarctic vortex. We find that faithful representation of stratospheric transport in this CTM using Lin and Rood advection is possible with a full mesosphere, ~1 km resolution in the lower stratosphere, and relatively low vertical resolution (>4 km spacing) in the middle stratosphere and above, but lowering the lid from the upper to lower mesosphere leads to less realistic constituent distributions in the upper stratosphere. Ultimately, this affects the polar lower stratosphere, but the effects are greater for the Antarctic than the Arctic. The fidelity of lower stratospheric transport requires realistic tropical and high latitude mixing barriers which are produced at 2°×2.5°, but not lower resolution. At 2°×2.5° resolution, the CTM produces a vortex capable of isolating perturbed chemistry (e.g. high Cly and low NOy) required for simulating polar ozone loss.
Large eddy simulation of urban features for Copenhagen metropolitan area
Authors: Mahura A. , Leroyer S. , Mestayer P. , Calmet I. , Dupont S. , Long N. , Baklanov A. , Petersen C. , Sattler K. , Nielsen N. W. 
Published: April 2010

Abstract. The large eddy simulations employing the SUBMESO model with the urban soil layer model SM2-U were performed for the model domain covering the Danish Island of Sealand and including the Copenhagen metropolitan area. Monthly and diurnal cycle variability were studied for the net radiation, sensible and storage heat fluxes, surface's temperatures, and others. These were evaluated for selected urban vs. non urban related types of covers/surfaces and urban districts such as city center, high buildings, industrial, and residential. Results showed strong effects of urban features on temporal and spatial variability. They are useful and applicable for verification of numerical weather prediction models and development of urban canopy parameterizations.
Aerosol light absorption in the North Atlantic: trends and seasonal characteristics during the period 1989 to 2003
Authors: Junker C. , Jennings S. G. , Cachier H. 
Published: April 2010

Abstract. Aerosol light attenuation on quartz fibre filters has been measured since February 1989 at the Mace Head Atmospheric Research station near Carna, Co. Galway, Ireland, using an Aethalometer. The frequency of occurrence of the hourly averaged aerosol absorption data is found to be bimodally distributed. The two modes result from clean marine air and anthropogenically polluted continental air both being advected to the station dependent on the prevailing wind direction. The hourly averages of the marine portion of the aerosol light absorption are found to follow closely a lognormal distribution with a geometric mean of 0.310 Mm−1. The hourly averages of continental sector aerosol absorption are neither normally nor lognormally distributed and have an arithmetic mean of 6.36 Mm−1, indicating the presence of anthropogenic sources for BC east of the Mace Head station. The time series of the monthly averaged attenuation coefficient σatt of both marine and continental sector aerosol shows an increase from 1989 to 1997 and a levelling off thereafter. The monthly maximum of marine sector σatt is found in May. Trend and seasonal characteristics of the clean marine aerosol attenuation coefficients observed at Mace Head appear to be driven by meteorological factors, as indicated by rainfall data and by trends in the North Atlantic Oscillation (NAO) indices.
Evolution of aerosol optical thickness over Europe during the August 2003 heat wave as seen from CHIMERE model simulations and POLDER data
Authors: Hodzic A. , Vautard R. , Chepfer H. , Goloub P. , Menut L. , Chazette P. , Deuzé J. L. , Apituley A. , Couvert P. 
Published: April 2010

Abstract. This study describes the atmospheric aerosol load encountered during the large-scale pollution episode that occurred in August 2003, by means of the aerosol optical thicknesses (AOTs) measured at 865 nm by the Polarization and Directionality of the Earth's Reflectances (POLDER) sensor and the simulation by the CHIMERE chemistry-transport model. During this period many processes (stagnation, photochemistry, forest fires) led to unusually high particle concentrations and optical thicknesses. The observed/simulated AOT comparison helps understanding the ability of the model to reproduce most of the gross AOT features observed in satellite data, with a general agreement within a factor 2 and correlations in the 0.4–0.6 range. However some important aerosol features are missed by the simulation using regular sources. Additional simulations including emissions and high-altitude transport of smoke from wildfires that occurred in Portugal indicate that these processes could dominate the signal. This study also highlights the difficulties of comparing simulated and POLDER-derived AOTs due to large uncertainties in both cases. Observed AOT values are significantly lower than the simulated ones (30–50%). The simultaneous comparison with the ground-based Sun photometer Aerosol Robotic Network (AERONET) measurements suggests, for the European sites considered here, an underestimation of POLDER-derived aerosol levels with a factor between 1 and 2. AERONET AOTs compare better with simulations (no particular bias) than POLDER AOTs do.
Screening the ESA ATSR-2 World Fire Atlas (1997–2002)
Authors: Mota B. W. , Pereira J. M. C. , Oom D. , Vasconcelos M. J. P. , Schultz M. 
Published: April 2010

Abstract. The European Space Agency (ESA) World Fire Atlas (WFA), for the period 1997–2002, is built using night time data from the Along Track Scanning Radiometer (ATSR) onboard the Second European Remote-Sensing Satellite (ERS-2). The spatial resolution of the data is 1 km and the satellite revisiting period is 3 days at the equator. The WFA is the first and longest archive of global fire observations and has been used in numerous biomass burning studies. Known limitations of the WFA are the inclusion of warm surfaces, gas flares, and city lights, and an underestimation of actual global fire activity, due to the time of satellite overpass. Nevertheless, it has been considered that the WFA contains a relatively small proportion of observations that do not correspond to vegetation fires. We used ancillary land cover, night-lights and volcanic activity datasets, combined with statistical techniques to detect the occurrence of space-time clusters, to screen the algorithm 2 (308°K threshold) WFA data for the period 1997–2002. During the study period, the annual percentage of false alarms and non-vegetation fires varied from a minimum value of 20.6% in 1997 to a maximum of 27.9% in 1998. Gas flares and hot bare soils are the major sources of false alarms and non-vegetation fires.
Seasonal and diurnal characteristics of water soluble inorganic compounds in the gas and aerosol phase in the Zurich area
Authors: Fisseha R. , Dommen J. , Gutzwiller L. , Weingartner E. , Gysel M. , Emmenegger C. , Kalberer M. , Baltensperger U. 
Published: April 2010

Abstract. Gas and aerosol samples were taken using a wet effluent diffusion denuder/aerosol collector (WEDD/AC) coupled to ion chromatography (IC) in the city of Zurich, Switzerland from August to September 2002 and in March 2003. Major water soluble inorganic ions; nitrate, sulfate, and nitrite were analyzed online with a time resolution of two hours for the gas and aerosol phase. The fraction of water soluble inorganic anions in PM10 varied from 15% in August to about 38% in March. Seasonal and diurnal variations of nitrate in the gas and aerosol phase were observed with more than 50% of the total nitrate in the gas phase during August and more than 80% of nitrate in the aerosol phase during March exceeding the concentration of sulfate by a factor of 2. Aerosol sulfate, on the other hand, did not show significant variability with season. However, in the gas phase, the SO2 concentration was 6.5 times higher in winter than in summer. Nitrous acid (HONO) also showed a diurnal variation in both the gas and aerosol phase with the lowest concentration (0.2–0.6 µg/m3) in the afternoon. The primary pollutants, NO, CO and SO2 mixing ratios were often at their highest between 04:00–10:00 local time due to the build up of fresh vehicle emission under a nocturnal inversion.