Regional climate model assessment of the urban land-surface forcing over central Europe
Summary: The impact of cities and urban surfaces on climate of central Europe is examined using a regional climate model coupled to a single-layer urban canopy model. Results show a significant impact on temperature (up to 1.5K increase in summer), the boundary layer height, surface wind with a winter decrease and precipitation (a summer decrease). Applying the urban canopy model, the regional climate model exhibits a decreased model bias when compared to observations.
Measurements of OH and RO2 radicals at Dome C, East Antarctica
Summary: Concentrations of OH radicals and the sum of peroxy radicals, RO2, were measured in the boundary layer for the first time on the East Antarctic Plateau at the Concordia Station during the austral summer 2011/2012. The concentrations of radicals were comparable to those observed at the South Pole, confirming that the elevated oxidative capacity of the Antarctic atmospheric boundary layer found at the South Pole is not restricted to the South Pole but common over the high Antarctic plateau.
Mesoscopic surface roughness of ice crystals pervasive across a wide range of ice crystal conditions
Summary: High-resolution images of ice crystals acquired by environmental scanning electron microscope reveal a wide array of surface complexities at scales from 100 nm to greater than 10 microns. These observations include ice crystals grown in the low-pressure microscope chamber and crystals grown externally under cirrus cloud conditions and then transferred for imaging. The results suggest that accounting for microscale complexity is critical for understanding cirrus interactions with radiation.
CCN activity of size-selected aerosol at a Pacific coastal location
Summary: As one aspect of the NETwork on Climate and Aerosols: addressing key uncertainties in Remote Canadian Environments, measurements of the cloud condensation nucleation properties of 50 nm and 100 nm aerosol particles were conducted at Ucluelet on the west coast of Vancouver Island in August 2013. The most efficient cloud condensation nuclei arose when the organic to sulfate ratio of the aerosol was lowest and when winds arrived from the west after transport through the marine boundary layer.
J. D. Yakobi-Hancock, L. A. Ladino, A. K. Bertram, J. A. Huffman, K. Jones, W. R. Leaitch, R. H. Mason, C. L. Schiller, D. Toom-Sauntry, J. P. S. Wong, and J. P. D. Abbatt Atmos. Chem. Phys., 14, 12307-12317, 2014 AbstractFinal Revised Paper (PDF, 1940 KB)Supplement (810 KB)Discussion Paper (ACPD)
24 Nov 2014
Modeling of HCHO and CHOCHO at a semi-rural site in southern China during the PRIDE-PRD2006 campaign
Chemical composition and mass size distribution of PM1 at an elevated site in central east China
Summary: An AMS was employed to measure the mass and size distributions of PM1 at an elevated site. Features of PM1 at four seasons, during different kinds of episodes including NPF, polluted, PBL, LFT and in-cloud, were discussed. The characterizations of PM1 at seven clusters of air masses were also analyzed. BBOA, CCOA and oxidized organic aerosols were resolved by AMS-PMF (positive matrix function). Almost half of OA were oxidized, and BBOA is 34% of OA in summer; CCOA is 22% of OA in winter as well.
Missing SO2 oxidant in the coastal atmosphere? – observations from high-resolution measurements of OH and atmospheric sulfur compounds
Summary: Sulfuric acid plays a major role in the formation of aerosol particles and clouds. Measurements at the west coast of Ireland reveal that oxidation of SO2 by OH explains only 20%, on average, of H2SO4 formation in coastal marine air. Additional sources may be (a) oxidation by Criegee intermediates produced photolytically and/or (b) formation from SO3 instead of SO2 in the oxidation of dimethyl sulfide, suggesting an important role of marine emissions in the self-cleaning power of the atmosphere.
Atmospheric amines and ammonia measured with a chemical ionization mass spectrometer (CIMS)
Summary: Amiens play important roles in atmospheric secondary aerosol formation and human health, but the fast response measurements of amines are lacking. Here we show measurements in a southeastern US forest and a moderately polluted midwestern site. Our results show that gas to particle conversion is an important process that controls ambient amine concentrations and that biomass burning is an important source of amines.
Y. You, V. P. Kanawade, J. A. de Gouw, A. B. Guenther, S. Madronich, M. R. Sierra-Hernández, M. Lawler, J. N. Smith, S. Takahama, G. Ruggeri, A. Koss, K. Olson, K. Baumann, R. J. Weber, A. Nenes, H. Guo, E. S. Edgerton, L. Porcelli, W. H. Brune, A. H. Goldstein, and S.-H. Lee Atmos. Chem. Phys., 14, 12181-12194, 2014 AbstractFinal Revised Paper (PDF, 7741 KB)Supplement (1264 KB)Discussion Paper (ACPD)
19 Nov 2014
Aerosol indirect effects on continental low-level clouds over Sweden and Finland
Reactivity of stabilized Criegee intermediates (sCIs) from isoprene and monoterpene ozonolysis toward SO2 and organic acids
M. Sipilä, T. Jokinen, T. Berndt, S. Richters, R. Makkonen, N. M. Donahue, R. L. Mauldin III, T. Kurtén, P. Paasonen, N. Sarnela, M. Ehn, H. Junninen, M. P. Rissanen, J. Thornton, F. Stratmann, H. Herrmann, D. R. Worsnop, M. Kulmala, V.-M. Kerminen, and T. Petäjä Atmos. Chem. Phys., 14, 12143-12153, 2014 AbstractFinal Revised Paper (PDF, 1568 KB)Discussion Paper (ACPD)
19 Nov 2014
Characteristics and sources of gravity waves observed in noctilucent cloud over Norway
Summary: Summertime gravity waves detected in noctilucent clouds (NLCs) between 64◦ and 74◦N are found to have a similar climatology to those observed between 60◦ and 64◦N, and their direction of propagation is to the north and northeast as observed south of 64◦N. However, a unique population of fast, short wavelength waves propagating towards the SW is observed in the NLC. The sources of the prominent wave structures observed in the NLC are likely to be from waves propagating from near the tropopause.
Measurements of the aerosol chemical composition and mixing state in the Po Valley using multiple spectroscopic techniques
Summary: We made use of multiple spectrometric techniques for characterizing the aerosol chemical composition and mixing in the Po Valley in the summer.
The oxygenated organic aerosol (OOA) concentrations were correlated with simple tracers for recirculated planetary boundary layer air.
A full internal mixing between black carbon (BC) and the non-refractory aerosol components was never observed. Local sources in the Po Valley were responsible for the production of organic particles unmixed with BC.
S. Decesari, J. Allan, C. Plass-Duelmer, B. J. Williams, M. Paglione, M. C. Facchini, C. O'Dowd, R. M. Harrison, J. K. Gietl, H. Coe, L. Giulianelli, G. P. Gobbi, C. Lanconelli, C. Carbone, D. Worsnop, A. T. Lambe, A. T. Ahern, F. Moretti, E. Tagliavini, T. Elste, S. Gilge, Y. Zhang, and M. Dall'Osto Atmos. Chem. Phys., 14, 12109-12132, 2014 AbstractFinal Revised Paper (PDF, 4424 KB)Supplement (1755 KB)Discussion Paper (ACPD)
18 Nov 2014
Lidar observation of the 2011 Puyehue-Cordón Caulle volcanic aerosols at Lauder, New Zealand
Spatial and temporal variability of sources of ambient fine particulate matter (PM2.5) in California
Summary: Ambient PM2.5 in California originates from a large number of diverse sources. These sources show distinct spatial and temporal variability throughout the state. Secondary aerosols are generally the most abundant contributor to ambient PM2.5 mass, while vehicular emissions and biomass burning are the main primary sources of ambient PM2.5 in California.
Ground-based aerosol characterization during the South American Biomass Burning Analysis (SAMBBA) field experiment
Summary: This paper details the physical--chemical characteristics of aerosols in a region strongly impacted by biomass burning in the western part of the Brazilian Amazon region. For such, a large suite of state-of-the-art instruments for realtime analysis was deployed at a ground site. Among the key findings, we observe the strong prevalence of organic aerosols associated to fire emissions, with important climate effects, and indications of its very fast processing in the atmosphere.
Assimilation of lidar signals: application to aerosol forecasting in the western Mediterranean basin
Y. Wang, K. N. Sartelet, M. Bocquet, P. Chazette, M. Sicard, G. D'Amico, J. F. Léon, L. Alados-Arboledas, A. Amodeo, P. Augustin, J. Bach, L. Belegante, I. Binietoglou, X. Bush, A. Comerón, H. Delbarre, D. García-Vízcaino, J. L. Guerrero-Rascado, M. Hervo, M. Iarlori, P. Kokkalis, D. Lange, F. Molero, N. Montoux, A. Muñoz, C. Muñoz, D. Nicolae, A. Papayannis, G. Pappalardo, J. Preissler, V. Rizi, F. Rocadenbosch, K. Sellegri, F. Wagner, and F. Dulac Atmos. Chem. Phys., 14, 12031-12053, 2014 AbstractFinal Revised Paper (PDF, 3824 KB)Discussion Paper (ACPD)Special Issue
17 Nov 2014
Methane sulfonic acid-enhanced formation of molecular clusters of sulfuric acid and dimethyl amine
Impact of the representation of marine stratocumulus clouds on the anthropogenic aerosol effect
Summary: Several biases in the representation of clouds in the stratocumulus regime in the ECHAM6-HAM2 global climate model were found by evaluating the model in the stratocumulus cloud regime. Simulations with changes in model resolution and physics to better represent clouds and aerosol in the stratocumulus regime show that the human influence on clouds and thus climate by emission of aerosol particles is sensitive to the representation of (stratocumulus) clouds.
Forest canopy interactions with nucleation mode particles
Summary: What role do forests play in determining the concentration (and composition) of climate-relevant aerosol particles? This study seeks to address two aspects of this question. Firstly, we document high in-canopy removal of recently formed particles. Then we show evidence that growth rates of particles are a function of soil water availability via a reduction in canopy emissions of gases responsible for particle growth to climate-relevant sizes during drought conditions.
Summary: This paper presents a new operational CO2 forecast product as part of the Copernicus Atmospheric Services suite of atmospheric composition products, using the state-of-the-art numerical weather prediction model from the European Centre of Medium-Range Weather Forecasts.
The evaluation with independent observations shows that the forecast has skill in predicting the synoptic variability of CO2. The online simulation of CO2 fluxes from vegetation contributes to this skill.
A. Agustí-Panareda, S. Massart, F. Chevallier, S. Boussetta, G. Balsamo, A. Beljaars, P. Ciais, N. M. Deutscher, R. Engelen, L. Jones, R. Kivi, J.-D. Paris, V.-H. Peuch, V. Sherlock, A. T. Vermeulen, P. O. Wennberg, and D. Wunch Atmos. Chem. Phys., 14, 11959-11983, 2014 AbstractFinal Revised Paper (PDF, 7688 KB)Discussion Paper (ACPD)Special Issue
14 Nov 2014
The distribution and trends of fog and haze in the North China Plain over the past 30 years
The effects of aerosols on water cloud microphysics and macrophysics based on satellite-retrieved data over East Asia and the North Pacific
Summary: This study examines the characteristics of the microphysics and macrophysics of water clouds from East Asia to the North Pacific, using data from CloudSat and MODIS retrievals. We demonstrate regional and seasonal characteristics of the cloud vertical structure and found a difference in the “contoured frequency by optical-depth diagram” (CFODD) between the pristine oceanic area and the polluted land area, implying aerosol-–cloud interaction.
Chemical climatology of the southeastern United States, 1999–2013
Summary: This paper reviews aerometric measurements from Centreville, Alabama. The measurements show annual trends with air pollution emissions from 1999 to 2013. They provide a context for observations from 1 June to 15 July 2013 supporting the Southern Oxidant and Aerosol Study. An important goal of this experiment was to advance knowledge of aerosols produced in the atmosphere from precursors. The observations were in moist and warm conditions with the lowest gas and particle concentrations recorded.
Biogenic SOA formation through gas-phase oxidation and gas-to-particle partitioning – a comparison between process models of varying complexity
Summary: Secondary organic aerosols (SOA), produced through oxidation processes, constitute a large part of the global organic aerosol load and affect the climate. We found that the modeled mass of SOA was highly dependent on how the oxidation processes were explained in models. The results indicated that it was especially important to get the volatility distribution of the products from the first oxidation step right and that fragmentation during the oxidation process played an important role.
HO2NO2 and HNO3 in the coastal Antarctic winter night: a "lab-in-the-field" experiment
Summary: We report observations of nitric acid and peroxynitric acid, in coastal Antarctica during winter. During winter, it is dark 24h per day, so there is no influence of sunlight on atmospheric composition. We show that observed variability in concentrations is highly correlated with changes in temperature. We derive enthalpies of adsorption and show they are consistent with those derived in laboratory studies. The Antarctic, during winter, is an ideal natural laboratory to study air-snow exchange.
A meta-analysis of particle water uptake reconciliation studies
Summary: Water uptake of ambient particles was measured by 2 independent techniques at a wide range of locations between 2007 and 2013. The agreement between the techniques was mixed and hence the number of potential cloud seeds calculated from the measurements frequently showed discrepancies. Whilst there is sensitivity to how well we measure the size of the particles, much of the difference depends on how the particles behave when exposed to moisture in the different techniques (and in the atmosphere).
Aerosol characterization at the Saharan AERONET site Tamanrasset
Summary: Tamanrasset, in the heart of the Sahara, is a key site for aerosol research. The analysis of more than 2 years (2006-2009) of AERONET and KCICLO-corrected sun photometer measurements shows that atmospheric aerosols at Tamanrasset are modulated by the Convective Boundary Layer leading to pure Saharan dust conditions (April-September) and very clear sky conditions (November-February). Dust potential sources and anthropogenic fine aerosols arriving at Tamanrasset are also identified.
C. Guirado, E. Cuevas, V. E. Cachorro, C. Toledano, S. Alonso-Pérez, J. J. Bustos, S. Basart, P. M. Romero, C. Camino, M. Mimouni, L. Zeudmi, P. Goloub, J. M. Baldasano, and A. M. de Frutos Atmos. Chem. Phys., 14, 11753-11773, 2014 AbstractFinal Revised Paper (PDF, 5608 KB)Discussion Paper (ACPD)
11 Nov 2014
Global modelling of direct and indirect effects of sea spray aerosol using a source function encapsulating wave state
Summary: New parameterizations for the sea spray aerosol source flux and its organic fraction were incorporated into a global aerosol-climate model. The emissions of sea salt were considerably less than previous estimates. This study demonstrates that sea spray aerosol may actually decrease the number of cloud droplets, which has a warming effect on climate. Overall, sea spray aerosol was predicted to have a global cooling effect due to the scattering of solar radiation from sea spray aerosol particles.
A.-I. Partanen, E. M. Dunne, T. Bergman, A. Laakso, H. Kokkola, J. Ovadnevaite, L. Sogacheva, D. Baisnée, J. Sciare, A. Manders, C. O'Dowd, G. de Leeuw, and H. Korhonen Atmos. Chem. Phys., 14, 11731-11752, 2014 AbstractFinal Revised Paper (PDF, 4476 KB)Supplement (284 KB)Discussion Paper (ACPD)
07 Nov 2014
Analysis of nucleation events in the European boundary layer using the regional aerosol–climate model REMO-HAM with a solar radiation-driven OH-proxy
Biases in modeled surface snow BC mixing ratios in prescribed-aerosol climate model runs
Summary: Black carbon in snow lowers its albedo, increasing the absorption of sunlight, leading to positive radiative forcing, climate warming and earlier snow-melt. A series of recent studies have used prescribed rates of black carbon deposition to snow to assess the climate effects of black carbon in snow. Here we show that the use of prescribed deposition fluxes in these model studies leads to high biases in snow BC concentrations, caused by the decoupling of BC and snow deposition to the surface.
Summary: The complexity of the physical and chemical processes effectively turns global aerosol models into black boxes. In an attempt to lift the veil, we present a detailed budget of process contributions (emissions, nucleation, sulfate condensation, coagulation, aging, deposition) in ECHAM5.5-HAM2 across varying length- and timescales. We show a clear hierarchy exists in process importance, that can be used in improving and simplifying the model and for understanding discrepancies with observation.
Observations of rapid aerosol optical depth enhancements in the vicinity of polluted cumulus clouds
T. F. Eck, B. N. Holben, J. S. Reid, A. Arola, R. A. Ferrare, C. A. Hostetler, S. N. Crumeyrolle, T. A. Berkoff, E. J. Welton, S. Lolli, A. Lyapustin, Y. Wang, J. S. Schafer, D. M. Giles, B. E. Anderson, K. L. Thornhill, P. Minnis, K. E. Pickering, C. P. Loughner, A. Smirnov, and A. Sinyuk Atmos. Chem. Phys., 14, 11633-11656, 2014 AbstractFinal Revised Paper (PDF, 10228 KB)Discussion Paper (ACPD)Special Issue
06 Nov 2014
On direct passive microwave remote sensing of sea spray aerosol production
Evaluation of OMI operational standard NO2 column retrievals using in situ and surface-based NO2 observations
L. N. Lamsal, N. A. Krotkov, E. A. Celarier, W. H. Swartz, K. E. Pickering, E. J. Bucsela, J. F. Gleason, R. V. Martin, S. Philip, H. Irie, A. Cede, J. Herman, A. Weinheimer, J. J. Szykman, and T. N. Knepp Atmos. Chem. Phys., 14, 11587-11609, 2014 AbstractFinal Revised Paper (PDF, 2061 KB)Discussion Paper (ACPD)
05 Nov 2014
Evolution of aerosol chemistry in Xi'an, inland China, during the dust storm period of 2013 – Part 1: Sources, chemical forms and formation mechanisms of nitrate and sulfate
Summary: This work describes the chemical and physical characterization of very small (< 100 nm diameter) particles in the marine atmosphere. We show that sea salt is present even at very small sizes and present evidence that organic species are important contributors to apparent new particle formation events over the ocean.
Impact of the Asian monsoon anticyclone on the variability of mid-to-upper tropospheric methane above the Mediterranean Basin
P. Ricaud, B. Sič, L. El Amraoui, J.-L. Attié, R. Zbinden, P. Huszar, S. Szopa, J. Parmentier, N. Jaidan, M. Michou, R. Abida, F. Carminati, D. Hauglustaine, T. August, J. Warner, R. Imasu, N. Saitoh, and V.-H. Peuch Atmos. Chem. Phys., 14, 11427-11446, 2014 AbstractFinal Revised Paper (PDF, 6589 KB)Discussion Paper (ACPD)Special Issue
29 Oct 2014
The effect of low solubility organic acids on the hygroscopicity of sodium halide aerosols
Impacts of new particle formation on aerosol cloud condensation nuclei (CCN) activity in Shanghai: case study
C. Leng, Q. Zhang, J. Tao, H. Zhang, D. Zhang, C. Xu, X. Li, L. Kong, T. Cheng, R. Zhang, X. Yang, J. Chen, L. Qiao, S. Lou, H. Wang, and C. Chen Atmos. Chem. Phys., 14, 11353-11365, 2014 AbstractFinal Revised Paper (PDF, 5492 KB)Discussion Paper (ACPD)
29 Oct 2014
New emission factors for Australian vegetation fires measured using open-path Fourier transform infrared spectroscopy – Part 2: Australian tropical savanna fires
An important mechanism sustaining the atmospheric "water tower" over the Tibetan Plateau
Summary: The Tibetan Plateau (TP) with its thermal structure leads to dynamic processes of vapor transport, similar to the CISK mechanism of tropical cyclones.
Two CISK-like processes, contiguous horizontally but staggered vertically, in two ladders over the southern slopes and main platform of the TP relay the moist air over the TP. An integration of mechanical and thermal TP forcing is revealed in relation to the Asian summer monsoon circulation transporting water vapor from tropical oceans to the TP.