Submicron aerosol source apportionment of wintertime pollution in Paris, France by double positive matrix factorization (PMF2) using an aerosol chemical speciation monitor (ACSM) and a multi-wavelength Aethalometer
Size-dependent wet removal of black carbon in Canadian biomass burning plumes
Summary: We present a case study of BC wet removal by examining aerosol properties in three biomass burning plumes, one of which passed through a precipitating cloud. Nucleation scavenging preferentially removed the largest and most coated BC-containing particles. Calculated single-scattering albedo (SSA) showed little variation, as a large number of non-BC particles were also present in the precipitation-affected plume.
J. W. Taylor, J. D. Allan, G. Allen, H. Coe, P. I. Williams, M. J. Flynn, M. Le Breton, J. B. A. Muller, C. J. Percival, D. Oram, G. Forster, J. D. Lee, A. R. Rickard, M. Parrington, and P. I. Palmer Atmos. Chem. Phys., 14, 13755-13771, 2014 AbstractFinal Revised Paper (PDF, 3478 KB)Supplement (131 KB)Discussion Paper (ACPD)Special Issue
22 Dec 2014
Satellite-inferred European carbon sink larger than expected
Summary: Current knowledge about the European terrestrial biospheric carbon sink relies upon bottom-up and global surface flux inverse model estimates using in situ measurements. Our analysis of five satellite data sets comprises a regional inversion designed to be insensitive to potential retrieval biases and transport errors. We show that the satellite-derived sink is larger (1.0±0.3GtC/a) than previous estimates (0.4±0.4GtC/a).
M. Reuter, M. Buchwitz, M. Hilker, J. Heymann, O. Schneising, D. Pillai, H. Bovensmann, J. P. Burrows, H. Bösch, R. Parker, A. Butz, O. Hasekamp, C. W. O'Dell, Y. Yoshida, C. Gerbig, T. Nehrkorn, N. M. Deutscher, T. Warneke, J. Notholt, F. Hase, R. Kivi, R. Sussmann, T. Machida, H. Matsueda, and Y. Sawa Atmos. Chem. Phys., 14, 13739-13753, 2014 AbstractFinal Revised Paper (PDF, 3801 KB)Discussion Paper (ACPD)
22 Dec 2014
A two-habit model for the microphysical and optical properties of ice clouds
Summary: An ice cloud model is developed by assuming an ice cloud to be an ensemble of columns and aggregates with specific habit fractions at each particle size bin. The microphysical and optical properties of this two-habit model (THM) are compared with both laboratory and in situ measurements. When the THM is applied to ice cloud property retrieval, excellent spectral consistency is achieved. A comparison between observed and theoretical polarized reflectivities illustrates the applicability of THM.
The contribution of plume-scale nucleation to global and regional aerosol and CCN concentrations: evaluation and sensitivity to emissions changes
Summary: We implement a parameterization of sub-grid new-particle formation in sulfur-rich plumes (P6) for the first time into a global chemical-transport model with online aerosol microphysics. Compared with previous treatments of sub-grid particle formation, use of the P6 parameterization limits sub-grid particle formation in polluted or low-sunlight regions. We also test the sensitivity of sub-grid particle formation to changes in SO2 or NOx emissions due to emissions controls.
A global process-based study of marine CCN trends and variability
Summary: Marine clouds have a strong effect on the Earth's radiative balance. One proposed climate feedback is that, in a warming climate, marine aerosol emissions will change due to changing wind speeds. We have examined the processes that affect aerosol emissions and removal over 15 years, and high-temporal-resolution output over 2 months. We conclude that wind trends are unlikely to cause a strong feedback in marine regions, but changes in removal processes or transport from continental regions may.
A physically based framework for modeling the organic fractionation of sea spray aerosol from bubble film Langmuir equilibria
Summary: The air over the ocean is full of sea spray particles ejected by bubbles that burst in the wake of breaking waves. The smallest of such particles, less than a micrometer in diameter, include organic matter derived from ocean biota. This paper introduces a method to calculate the chemical composition of spray particles. Ocean organic matter is divided into several classes using a global model. Basic chemistry relationships predict the amount of organic material in emitted spray.
Recent advances in understanding the Arctic climate system state and change from a sea ice perspective: a review
Summary: The article reviews progress in understanding of the Arctic sea ice decline. Processes are revisited from an atmospheric, ocean and sea ice perspective. There is strong evidence for decisive atmospheric drivers of sea ice change. Large-scale ocean influences on the Arctic Ocean hydrology and circulation are highly evident. Ocean heat fluxes are clearly impacting the ice margins. Little indication exists for a direct decisive influence of the warming ocean on the central Arctic sea ice cover.
Radiocarbon analysis of elemental and organic carbon in Switzerland during winter-smog episodes from 2008 to 2012 – Part 1: Source apportionment and spatial variability
P. Zotter, V. G. Ciobanu, Y. L. Zhang, I. El-Haddad, M. Macchia, K. R. Daellenbach, G. A. Salazar, R.-J. Huang, L. Wacker, C. Hueglin, A. Piazzalunga, P. Fermo, M. Schwikowski, U. Baltensperger, S. Szidat, and A. S. H. Prévôt Atmos. Chem. Phys., 14, 13551-13570, 2014 AbstractFinal Revised Paper (PDF, 6829 KB)Supplement (624 KB)Discussion Paper (ACPD)
19 Dec 2014
Overview of the Focused Isoprene eXperiment at the California Institute of Technology (FIXCIT): mechanistic chamber studies on the oxidation of biogenic compounds
T. B. Nguyen, J. D. Crounse, R. H. Schwantes, A. P. Teng, K. H. Bates, X. Zhang, J. M. St. Clair, W. H. Brune, G. S. Tyndall, F. N. Keutsch, J. H. Seinfeld, and P. O. Wennberg Atmos. Chem. Phys., 14, 13531-13549, 2014 AbstractFinal Revised Paper (PDF, 2608 KB)Discussion Paper (ACPD)
19 Dec 2014
Influence of CO2 observations on the optimized CO2 flux in an ensemble Kalman filter
Aerosol radiative effects in the ultraviolet, visible, and near-infrared spectral ranges using long-term aerosol data series over the Iberian Peninsula
Summary: A long-term analysis of aerosol radiative effects over the Iberian Peninsula is carried out. A reduction of aerosol effects on solar radiation at the surface is observed in the 2000s. Aerosol forcing efficiency is stronger for small and absorbing particles. The contributions of the ultraviolet, visible, and near-infrared spectral intervals to the total shortwave efficiency vary with the aerosol types, producing the visible range the dominant contribution for all aerosol types.
D. Mateos, M. Antón, C. Toledano, V. E. Cachorro, L. Alados-Arboledas, M. Sorribas, M. J. Costa, and J. M. Baldasano Atmos. Chem. Phys., 14, 13497-13514, 2014 AbstractFinal Revised Paper (PDF, 5173 KB)Discussion Paper (ACPD)
19 Dec 2014
Atmospheric submicron aerosol composition and particulate organic nitrate formation in a boreal forestland–urban mixed region
Summary: Positive matrix factorization (PMF) was applied to the unified high-resolution mass spectra organic species with NO+ and NO2+ ions from the measurement in a mixed region between the boreal forestland and the urban area. The PMF analysis succeeded in separating the mixed spectra into three distinct organic factors and one inorganic factor. The particulate organic nitrate was distinguished by PMF for the first time, with a contribution of one-third of the total nitrate mass.
L. Q. Hao, A. Kortelainen, S. Romakkaniemi, H. Portin, A. Jaatinen, A. Leskinen, M. Komppula, P. Miettinen, D. Sueper, A. Pajunoja, J. N. Smith, K. E. J. Lehtinen, D. R. Worsnop, A. Laaksonen, and A. Virtanen Atmos. Chem. Phys., 14, 13483-13495, 2014 AbstractFinal Revised Paper (PDF, 2149 KB)Supplement (1500 KB)Discussion Paper (ACPD)
18 Dec 2014
Dynamical analysis of sea-breeze hodograph rotation in Sardinia
Aerosol hygroscopicity and cloud condensation nuclei activity during the AC3Exp campaign: implications for cloud condensation nuclei parameterization
Summary: Atmospheric aerosol particles acting as CCN are pivotal elements of the hydrological cycle and climate change. In this study, we measured and characterized NCCN in relatively clean and polluted air during the AC3Exp campaign conducted at Xianghe, China, in summer 2013. We found that aerosol particle hygroscopicity and activation are more complex for heavy pollution particles because of the diversity in particle composition and mixing state. We have also shown the possibility of using bulk κc.
Long-term variability of dust events in Iceland (1949–2011)
Summary: Iceland is an active dust source in the high-latitude cold region. Dust day frequency in Iceland is comparable to dust studies from the active parts of China, Mongolia, and Iran. About 50% of annual dust events in the southern part of Iceland take place at sub-zero temperatures or in winter, when dust may be mixed with snow. The Arctic dust events (NE Iceland) are warm, occurring during summer/autumn while the sub-Arctic dust events (S Iceland) are mainly cold, occurring during winter/spring.
Bromine partitioning in the tropical tropopause layer: implications for stratospheric injection
Summary: We propose the existence of a daytime “tropical ring of atomic bromine” surrounding the tropics at a height between 15 and 19km. Our simulations show that VSL bromocarbons produce increases of 3pptv for inorganic bromine and 2pptv for organic bromine in the tropical TTL on an annual average, resulting in a total stratospheric bromine injection of 5pptv. This result suggests that the inorganic bromine injected into the stratosphere may be larger than that from VSL bromocarbons.
Daily global fire radiative power fields estimation from one or two MODIS instruments
Summary: This paper describes a method to correct the bias in daily fire radiative power (FRP) observations from any low Earth orbit satellite, so that that the budget of daily smoke emissions remains independent of the number of satellites from which FRP observations are taken into account. This ensures the possibility of running a system assimilating observations from several sensors, e.g. the Global Fire Assimilation System (GFAS), in case of failure of one of the MODIS instruments.
On the origin of the occasional spring nitrate peak in Greenland snow
Summary: Examinations on snowpit and firn core results from Summit, Greenland suggest that there are two mechanisms leading to the observed double nitrate peaks in some years in the industrial era: 1) long-rang transport of nitrate and 2) enhanced local photochemical production of nitrate. Both of these mechanisms are related to pollution transport, as the additional nitrate from either direct transport or enhanced local photochemistry requires enhanced nitrogen sources from anthropogenic emissions.
On the importance of cascading moisture recycling in South America
D. C. Zemp, C.-F. Schleussner, H. M. J. Barbosa, R. J. van der Ent, J. F. Donges, J. Heinke, G. Sampaio, and A. Rammig Atmos. Chem. Phys., 14, 13337-13359, 2014 AbstractFinal Revised Paper (PDF, 5884 KB)Discussion Paper (ACPD)
15 Dec 2014
Emission of iodine-containing volatiles by selected microalgae species
Summary: Phytoplankton suspensions were treated with high and low ozone levels, and volatile iodine (I2)-containing compounds were measured. Iodocarbon emissions were independent of the ozone level. I2 emission showed a strong dependency on the ozone level in the air as well as on the iodide concentration in the sample suspension. The experiments show that microalgae suspensions are capable of emitting I2 by the reaction of ozone with dissolved iodide at the air-water interface under natural conditions.
A joint data assimilation system (Tan-Tracker) to simultaneously estimate surface CO2 fluxes and 3-D atmospheric CO2 concentrations from observations
Summary: A new carbon cycle data assimilation system (Tan-Tracker) is developed based on an advanced hybrid assimilation approach, as a part of the preparation for the launch of the Chinese carbon dioxide observation satellite (TanSat). Tan-Tracker adopts a joint data assimilation framework to simultaneously estimate CO2 concentrations and CFs and thus gradually reduce the uncertainty in the CO2 concentration evolution through continuously fitting model CO2 concentration simulations to the observations.
Comparison of the HadGEM2 climate-chemistry model against in situ and SCIAMACHY atmospheric methane data
Summary: Globally, wetlands are a major source of methane, which is the second most important greenhouse gas. We find the JULES wetland methane scheme to perform well in general, although there is a tendency for it to overpredict emissions in the tropics and underpredict them in northern latitudes. Our study highlights novel uses of satellite data as a major tool to constrain land-atmosphere methane flux models in a warming world.
Technical Note: Reanalysis of upper troposphere humidity data from the MOZAIC programme for the period 1994 to 2009
Summary: Long-term water vapour measurements from the MOZAIC programme are a unique source for upper troposphere humidity data. However, due to an error in the calibration procedure, RH data from MOZAIC were biased towards higher values for the period starting in year 2000. Here we report the procedures followed to reanalyse the calibrations and to reprocess the entire MOZAIC RH data. This study serves as the reference publication for the reanalysed MOZAIC RH data base for the period 1994 to 2009.
Tropical deep convective life cycle: Cb-anvil cloud microphysics from high-altitude aircraft observations
Summary: This study presents in situ cloud microphysical observations obtained during a double flight in a Hector thunderstorm during the SCOUT-O3 campaign from Darwin, Northern Australia, in 2005. The measurements show a change of the micophysics with the storm's evolution. The clouds in the dissipating stage possess a high potential for affecting the humidity in the tropical tropopause layer.
W. Frey, S. Borrmann, F. Fierli, R. Weigel, V. Mitev, R. Matthey, F. Ravegnani, N. M. Sitnikov, A. Ulanovsky, and F. Cairo Atmos. Chem. Phys., 14, 13223-13240, 2014 AbstractFinal Revised Paper (PDF, 1227 KB)Discussion Paper (ACPD)
11 Dec 2014
Determination and climatology of the planetary boundary layer height above the Swiss plateau by in situ and remote sensing measurements as well as by the COSMO-2 model
Summary: An operational planetary boundary layer height detection method with several remote sensing instruments (wind profiler, Raman lidar, microwave radiometer) and algorithms (Parcel and bulk Richardson number methods, surface-based temperature inversion, aerosol and humidity gradient analysis) was validated against radio sounding. A comparison with the numerical weather prediction model COSMO-2 and the seasonal cycles of the day- and nighttime PBL for two stations on the Swiss plateau are presented.
Novel methods for predicting gas–particle partitioning during the formation of secondary organic aerosol
Summary: A description of the formation of secondary organic aerosol requires the prediction of the partitioning equilibrium of organic compounds with multiple functional groups between gas and organic particle phase. While this is typically done by predicting both the saturation vapour pressure and the activity coefficient in the organic particle phase, we demonstrate here that it is feasible to predict the partitioning equilibrium directly. This direct approach has greater precision.
Methane and carbon dioxide fluxes and their regional scalability for the European Arctic wetlands during the MAMM project in summer 2012
Summary: This paper presents airborne measurements of greenhouse gases collected in the European Arctic. Regional scale flux estimates for the northern Scandinavian wetlands are derived. These fluxes are found to be in excellent agreement with coincident surface measurements within the aircraft's sampling domain. This has allowed a significant low bias to be identified in two commonly used process-based land surface models.
S. J. O'Shea, G. Allen, M. W. Gallagher, K. Bower, S. M. Illingworth, J. B. A. Muller, B. T. Jones, C. J. Percival, S. J-B. Bauguitte, M. Cain, N. Warwick, A. Quiquet, U. Skiba, J. Drewer, K. Dinsmore, E. G. Nisbet, D. Lowry, R. E. Fisher, J. L. France, M. Aurela, A. Lohila, G. Hayman, C. George, D. B. Clark, A. J. Manning, A. D. Friend, and J. Pyle Atmos. Chem. Phys., 14, 13159-13174, 2014 AbstractFinal Revised Paper (PDF, 2389 KB)Discussion Paper (ACPD)
10 Dec 2014
A comprehensive parameterization of heterogeneous ice nucleation of dust surrogate: laboratory study with hematite particles and its application to atmospheric models
Summary: A new heterogeneous ice nucleation parameterization is developed and implemented in cloud models. The results of our simulations suggest stronger influence of dust particles lifted to the upper troposphere on heterogeneous nucleation and more ice nucleation at temperature and humidity conditions relevant to both mixed-phase and cirrus clouds when compared to the existing parametrical frameworks.
Iodine chemistry in the troposphere and its effect on ozone
A. Saiz-Lopez, R. P. Fernandez, C. Ordóñez, D. E. Kinnison, J. C. Gómez Martín, J.-F. Lamarque, and S. Tilmes Atmos. Chem. Phys., 14, 13119-13143, 2014 AbstractFinal Revised Paper (PDF, 8758 KB)Discussion Paper (ACPD)
10 Dec 2014
Development of a 10-year (2001–2010) 0.1° data set of land-surface energy balance for mainland China
A model study on changes of European and Swiss particulate matter, ozone and nitrogen deposition between 1990 and 2020 due to the revised Gothenburg protocol
Summary: We report a study of changes in the European air quality due to emission reductions, using the chemical transport model CAMx. The model simulations were performed with emissions for 1990, 2005, 2006 and 2020 using three emission scenarios prepared by IIASA/GAINS. Model evaluation was carried out for 2006. We calculated the changes between 1990 and 2005, and between 2005 and 2020. Changes in ozone, particulate matter and nitrogen deposition are the central theme of this study.
The impact of volcanic aerosol on the Northern Hemisphere stratospheric polar vortex: mechanisms and sensitivity to forcing structure
Summary: Earth system model simulations are used to investigate the impact of volcanic aerosol forcing on stratospheric dynamics, e.g. the Northern Hemisphere (NH) polar vortex. We find that mechanisms linking aerosol heating and high-latitude dynamics are not as direct as often assumed; high-latitude effects result from changes in stratospheric circulation and related vertical motions. The simulated responses also show evidence of being sensitive to the structure of the volcanic forcing used.
An improved dust emission model – Part 1: Model description and comparison against measurements
Summary: We developed an improved model for the emission of dust particulates ("aerosols") emitted by wind erosion from the world's deserts. The implementation of our improved dust emission model into a climate model improves its agreement against measurements. We furthermore find that dust emissions are substantially more sensitive to the soil state than most current climate models account for.
J. F. Kok, N. M. Mahowald, G. Fratini, J. A. Gillies, M. Ishizuka, J. F. Leys, M. Mikami, M.-S. Park, S.-U. Park, R. S. Van Pelt, and T. M. Zobeck Atmos. Chem. Phys., 14, 13023-13041, 2014 AbstractFinal Revised Paper (PDF, 2373 KB)Supplement (3571 KB)Discussion Paper
09 Dec 2014
Rare temperature histories and cirrus ice number density in a parcel and a one-dimensional model
Summary: The properties of cirrus clouds depend on the rate at which air cools as the cloud forms. Small-scale motions in the atmosphere have high rates of cooling. This usually leads to very small ice crystals. However, a few random cooling fluctuations will produce only a few ice crystals. This paper shows that these events are important even if they are rare: they lead to particles that sediment and influence a lot of air. The results show dehydration is less sensitive to details of ice nucleation.
Effect of different emission inventories on modeled ozone and carbon monoxide in Southeast Asia
T. Amnuaylojaroen, M. C. Barth, L. K. Emmons, G. R. Carmichael, J. Kreasuwun, S. Prasitwattanaseree, and S. Chantara Atmos. Chem. Phys., 14, 12983-13012, 2014 AbstractFinal Revised Paper (PDF, 8503 KB)Discussion Paper (ACPD)
08 Dec 2014
Stratospheric ozone depletion from future nitrous oxide increases
Mechanistic study of secondary organic aerosol components formed from nucleophilic addition reactions of methacrylic acid epoxide
Summary: We investigated how an important naturally emitted chemical, isoprene, can contribute to the formation of aerosol particles, which are a key component of air pollution that can also influence climate. Specifically, we found that a particular relative of isoprene, methacrylic acid epoxide, is capable of transforming into a number of different chemical components via reaction on existing aerosol particles. These results will help to make isoprene air quality model predictions more accurate.
Reactive oxygen species associated with water-soluble PM2.5 in the southeastern United States: spatiotemporal trends and source apportionment
Summary: The major emission sources of the reactive oxygen species (ROS) associated with ambient particulate matter in the southeastern United States were identified. The study shows biomass burning and secondary aerosol formation as the major sources contributing to the ROS-generating capability of ambient particles. The ubiquitous nature of these two sources suggests widespread population exposures to the toxic aerosol components.
A regional CO2 observing system simulation experiment for the ASCENDS satellite mission
Summary: Our simulations suggest that CO2 measurements by the planned ASCENDS satellite could improve estimates of emissions and uptake by up to 50% at the weekly 1° by 1° scale, 40-75% at the annual biome scale, and 65-85% for the whole of North America. The results depend on the laser wavelength used and the assumed precision of the measurements. The resulting biome flux uncertainties, 0.01-0.06 billion tons of C per year, would satisfy one definition of mission success.
J. S. Wang, S. R. Kawa, J. Eluszkiewicz, D. F. Baker, M. Mountain, J. Henderson, T. Nehrkorn, and T. S. Zaccheo Atmos. Chem. Phys., 14, 12897-12914, 2014 AbstractFinal Revised Paper (PDF, 6975 KB)Discussion Paper (ACPD)
08 Dec 2014
Estimating regional fluxes of CO2 and CH4 using space-borne observations of XCH4: XCO2
Summary: Satellite measurements of CO2 and CH4 can be subject to regional systematic errors that can consequently compromise their ability to infer robust flux estimates of these two gases. We develop a method to use retrieved ratios of CH4 and CO2 that are less affected by systematic error. We show that additional in situ data are needed to anchor these observed ratios so they can simultaneously infer fluxes of CO2 and CH4. We argue the ratio data will provide a more faithful description of true fluxes.
A. Fraser, P. I. Palmer, L. Feng, H. Bösch, R. Parker, E. J. Dlugokencky, P. B. Krummel, and R. L. Langenfelds Atmos. Chem. Phys., 14, 12883-12895, 2014 AbstractFinal Revised Paper (PDF, 3169 KB)Discussion Paper (ACPD)
08 Dec 2014
Atmospheric measurements of ratios between CO2 and co-emitted species from traffic: a tunnel study in the Paris megacity
Summary: We present the first study of CO2, VOCs and NOx measured all together in a road tunnel around the Paris megacity with the aim to quantify the ratios of these species co-emitted within traffic emissions. It allows us to independently assess some of the ratios provided in the latest Paris emission inventory. It also reveals a large variability of the ratios to CO2, implying that traffic does not have a unique imprint in the urban plume, but rather leaves various signatures.
Nitrous oxide emissions from a commercial cornfield (Zea mays) measured using the eddy covariance technique
Summary: An EC system was assembled with a sonic anemometer and a new fast-response N2O analyzer and applied in a cornfield during a growing season. This N2O EC system provided reliable N2O flux measurements. The average flux was about 63% higher during the daytime than during the nighttime. Seasonal fluxes were highly dependent on soil moisture rather than soil temperature.
Summary: Aqueous phase occurs in the atmosphere as cloud droplets and aqueous aerosol.
The Henry's law constant regulates the water-gas partitioning of a molecule, but experimental data on polyols are limited.
New values are derived for molecules with 2-6 hydroxyl groups, by combining other thermophysical data (e.g. vapour pressure, water activity, solubility).
It is analysed which molecules will stay mostly in the gas phase, and which will preferably partition to droplet or aqueous aerosol.
On the hiatus in the acceleration of tropical upwelling since the beginning of the 21st century
Summary: This study compares observations and simulation results of ozone in the lower tropical stratosphere. It shows that ozone in this region decreased from 1985 up to about 2002, which is consistent with an increase in tropical upwelling predicted by climate models. However, the decrease effectively stops after 2002, indicating that significant changes in tropical upwelling have occurred. The most important factor appears to be that the vertical ascent in the tropics is no longer accelerating.
Emissions of biogenic volatile organic compounds and subsequent photochemical production of secondary organic aerosol in mesocosm studies of temperate and tropical plant species
K. P. Wyche, A. C. Ryan, C. N. Hewitt, M. R. Alfarra, G. McFiggans, T. Carr, P. S. Monks, K. L. Smallbone, G. Capes, J. F. Hamilton, T. A. M. Pugh, and A. R. MacKenzie Atmos. Chem. Phys., 14, 12781-12801, 2014 AbstractFinal Revised Paper (PDF, 6791 KB)Supplement (182 KB)Discussion Paper (ACPD)
05 Dec 2014
Surface-to-mountaintop transport characterised by radon observations at the Jungfraujoch
Summary: Radon detectors at Bern and Jungfraujoch were used to monitor the transport of radon-rich boundary layer air from the Swiss Plateau to the Alpine ridge. Radon was successfully used to discriminate between different types of vertical transport, using the shape of the diurnal cycle to identify days with upslope mountain winds. For many air-mass properties, however, the total land-surface influence (indicated by the radon concentration) was more decisive than the type of vertical transport.
A. D. Griffiths, F. Conen, E. Weingartner, L. Zimmermann, S. D. Chambers, A. G. Williams, and M. Steinbacher Atmos. Chem. Phys., 14, 12763-12779, 2014 AbstractFinal Revised Paper (PDF, 2072 KB)Discussion Paper (ACPD)
05 Dec 2014
Fast transport from Southeast Asia boundary layer sources to northern Europe: rapid uplift in typhoons and eastward eddy shedding of the Asian monsoon anticyclone
Summary: Enhanced tropospheric trace gases (e.g. pollutants) were measured in situ in
the lowermost stratosphere over Northern Europe on 26 September 2012
during the TACTS aircraft campaign. We found that the combination of rapid uplift by a typhoon and eastward eddy shedding from the Asian monsoon anticyclone is a novel fast transport pathway
that may carry boundary emissions from Southeast
Asia/western Pacific within approximately 5 weeks to the lowermost
stratosphere in Northern Europe.
Trends in peroxyacetyl nitrate (PAN) in the upper troposphere and lower stratosphere over southern Asia during the summer monsoon season: regional impacts
Summary: The Asian summer monsoon transports pollutants from local emission sources to the upper troposphere and lower stratosphere (UTLS). The increasing trend of these pollutants may have climatic impact. This study addresses the impact of convectively lifted Indian and Chinese emissions on the ULTS. Sensitivity experiments with emission changes in particular regions show that Chinese emissions have a greater impact on the concentrations of NOY species than Indian emissions.
Potential climate forcing of land use and land cover change
Summary: While climate change mitigation policy often focuses on the energy sector, we find that 40% of the historical human-caused change in the Earth’s radiative balance can be attributed to land use activities, such as deforestation and agriculture. Since pressure on land resources is expected to increase, we compute a theoretical upper bound on the radiative balance impacts from future land use which suggests that both energy policy and land policy are necessary to minimize future climate change.
Atmospheric black carbon and warming effects influenced by the source and absorption enhancement in central Europe
S. Nordmann, Y. F. Cheng, G. R. Carmichael, M. Yu, H. A. C. Denier van der Gon, Q. Zhang, P. E. Saide, U. Pöschl, H. Su, W. Birmili, and A. Wiedensohler Atmos. Chem. Phys., 14, 12683-12699, 2014 AbstractFinal Revised Paper (PDF, 4243 KB)Supplement (458 KB)Discussion Paper (ACPD)
02 Dec 2014
Using cloud ice flux to parametrise large-scale lightning
Summary: Lightning is important in atmospheric chemistry models as a source of
nitrogen oxides which affect the greenhouse gases ozone and methane. We
present a new approach to modelling lightning using the upward movement of
ice in clouds, an essential part of the charging mechanism in thunderstorms.
The new approach performs well compared to those already in use and provides
a novel, physically based scheme that has the potential to improve the
robustness of simulated flash rates and emissions.
Tropospheric carbon monoxide over the Pacific during HIPPO: two-way coupled simulation of GEOS-Chem and its multiple nested models
Summary: Limited by coarse resolutions, global chemical transport models cannot well capture small-scale nonlinear processes. To alleviate the problem, we develop a two-way coupled system to integrate the global GEOS-Chem model and its three high-resolution nested models covering Asia, Europe and North America. Confirmed by comparisons with observations, the coupled system improves upon the global model with a 10% increase in global tropospheric CO, a 4% decrease in OH and a 4% increase in MCF lifetime.
Overview and sample applications of SMILES and Odin-SMR retrievals of upper tropospheric humidity and cloud ice mass
Summary: The sub-millimetre wavelength region has been identified as very useful for measurements of cloud ice mass. The only satellite sensors operating in this wavelength region are so far limb sounders, and results from two such instruments are presented and sample applications are demonstrated. The results have high intrinsic value, but serve also as a practical preparation for planned dedicated sub-millimetre cloud missions.
The thermodynamic structure of summer Arctic stratocumulus and the dynamic coupling to the surface
Summary: During ASCOS, clouds are more frequently decoupled from the surface than coupled to it; when coupling occurs it is primary driven by the cloud. Decoupled clouds have a bimodal structure; they are either weakly or strongly decoupled from the surface; the enhancement of the decoupling is possibly due to sublimation of precipitation. Stable clouds (no cloud-driven mixing) are also observed; those are optically thin, often single-phase liquid, with no or negligible precipitation (e.g. fog).
Analysis of elevated springtime levels of Peroxyacetyl nitrate (PAN) at the high Alpine research sites Jungfraujoch and Zugspitze
Summary: Mixing ratios of Peroxyacetyl nitrate (PAN) at Jungfraujoch (Switzerland) and Zugspitze (Germany) show a seasonal variation with maxima in spring, typical for remote sites in the lower atmosphere in northern mid-latitudes. The detailed analysis of PAN measurements of May 2008 indicates that PAN at these high mountain sites is dominated by photochemical formation in the relatively cold polluted European planetary boundary layer rather than formation in the free troposphere.
Air quality simulations of wildfires in the Pacific Northwest evaluated with surface and satellite observations during the summers of 2007 and 2008
Summary: Wildfire season simulations from an air quality forecast system for the Pacific Northwest were compared to surface monitor observations across the region and NASA Earth Observing System satellite retrievals of plume top, nitrogen dioxide, aerosol optical depth, and carbon monoxide. This study discusses why the Community Multi-scale Air Quality model predictions under-predicted secondary organic aerosol (SOA) production for events when fire emissions were transported large distances.
F. L. Herron-Thorpe, G. H. Mount, L. K. Emmons, B. K. Lamb, D. A. Jaffe, N. L. Wigder, S. H. Chung, R. Zhang, M. D. Woelfle, and J. K. Vaughan Atmos. Chem. Phys., 14, 12533-12551, 2014 AbstractFinal Revised Paper (PDF, 2840 KB)Supplement (7301 KB)Discussion Paper (ACPD)
27 Nov 2014
Competition between water uptake and ice nucleation by glassy organic aerosol particles
Summary: Glassy organic particles can serve as ice nuclei at low temperatures. We provide a rationale for these findings using a numerical aerosol diffusion model that describes particle phase state and its kinetics during simulated atmospheric updrafts dependent upon composition, size, updraft velocity, temperature and humidity. Our simulations suggest that aerosols from anthropogenic aromatic organics can be particularly relevant for ice cloud formation.
Variations of cloud condensation nuclei (CCN) and aerosol activity during fog–haze episode: a case study from Shanghai
C. Leng, Q. Zhang, D. Zhang, C. Xu, T. Cheng, R. Zhang, J. Tao, J. Chen, S. Zha, Y. Zhang, X. Li, L. Kong, and W. Gao Atmos. Chem. Phys., 14, 12499-12512, 2014 AbstractFinal Revised Paper (PDF, 6488 KB)Discussion Paper (ACPD)
27 Nov 2014
Stratospheric lifetime ratio of CFC-11 and CFC-12 from satellite and model climatologies
Summary: Stratospheric lifetimes determine the global warming and ozone depletion potentials of chlorofluorocarbons. We present new estimates of the CFC-11/CFC-12 lifetime ratio from satellite and model data (ACE-FTS, HIRDLS, MIPAS, and EMAC/CLaMS). Our estimates of 0.46+/-0.04 (satellites) and 0.48+/-0.07 (model) are in excellent agreement with the recent SPARC reassessment. Having smaller uncertainties than other studies, our results can help to better constrain future CFC lifetime recommendations.
L. Hoffmann, C. M. Hoppe, R. Müller, G. S. Dutton, J. C. Gille, S. Griessbach, A. Jones, C. I. Meyer, R. Spang, C. M. Volk, and K. A. Walker Atmos. Chem. Phys., 14, 12479-12497, 2014 AbstractFinal Revised Paper (PDF, 4292 KB)Supplement (36 KB)Discussion Paper (ACPD)
27 Nov 2014
Modelled black carbon radiative forcing and atmospheric lifetime in AeroCom Phase II constrained by aircraft observations
Summary: Far from black carbon (BC) emission sources, present climate models are unable to reproduce flight measurements. By comparing recent models with data, we find that the atmospheric lifetime of BC may be overestimated in models. By adjusting modeled BC concentrations to measurements in remote regions - over oceans and at high altitudes - we arrive at a reduced estimate for BC radiative forcing over the industrial era.
B. H. Samset, G. Myhre, A. Herber, Y. Kondo, S.-M. Li, N. Moteki, M. Koike, N. Oshima, J. P. Schwarz, Y. Balkanski, S. E. Bauer, N. Bellouin, T. K. Berntsen, H. Bian, M. Chin, T. Diehl, R. C. Easter, S. J. Ghan, T. Iversen, A. Kirkevåg, J.-F. Lamarque, G. Lin, X. Liu, J. E. Penner, M. Schulz, Ø. Seland, R. B. Skeie, P. Stier, T. Takemura, K. Tsigaridis, and K. Zhang Atmos. Chem. Phys., 14, 12465-12477, 2014 AbstractFinal Revised Paper (PDF, 986 KB)Discussion Paper (ACPD)
27 Nov 2014
Modeling of gaseous methylamines in the global atmosphere: impacts of oxidation and aerosol uptake
Summary: Global lifetimes and concentrations of gaseous methylamines (MMA, DMA, and TMA) have been simulated.
Oxidation and aerosol uptakes are dominant sinks for these methylamines. The oxidation alone leads to their lifetimes of 5-10h in most parts of low and middle latitude regions. The uptake by secondary species can shorten their lifetime to as low as 1-2h over central Europe, eastern Asia, and the eastern US.
The modeled concentrations are substantially lower than observed values available.
Low temperatures enhance organic nitrate formation: evidence from observations in the 2012 Uintah Basin Winter Ozone Study
Summary: Alkyl nitrate formation is known to be an important sink of NOx in a wide range of environments. In a study in the Uintah basin in 2012, we find that formation of these compounds represents a more rapid NOx (NO + NO2) sink than does nitric acid formation. This rapid formation is in large part due to the low mean temperature (~0°C) during the study and is consistent with laboratory observations.
Chemistry and mineralogy of clay minerals in Asian and Saharan dusts and the implications for iron supply to the oceans
Summary: Mineral dust supplies iron to remote oceans, stimulating phytoplankton growth and carbon dioxide decrease. Iron-bearing clay minerals are the dominant phase in mineral dust. However, their mineralogical properties are largely unknown. We first determined microstructures and chemical compositions of the clay minerals in individual dust particles by transmission electron microscopy. Nanocrystalline illite-smectite series clay minerals and iron-rich chlorite are probably important sources of iron.
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)