Improvement of climate predictions and reduction of their uncertainties using learning algorithms
Atmos. Chem. Phys., 15, 8631-8641, doi:10.5194/acp-15-8631-2015, 2015
On the use of satellite-derived CH4 : CO2 columns in a joint inversion of CH4 and CO2 fluxes
Summary: This study attempts to determine the feasibility of a new assimilation method of satellite measurements of CH4 and CO2 for optimization of their surface fluxes in a synthetic environment. Instead of their absolute concentrations, we assimilate the ratios of their concentrations (CH4/CO2) in our inversion. Doing so helps us to reduce the effect of atmospheric scattering on the measurements in our system. However, assimilation of the ratios makes the inversion non-linear.
Atmos. Chem. Phys., 15, 8615-8629, doi:10.5194/acp-15-8615-2015, 2015
Effects of urban land expansion on the regional meteorology and air quality of eastern China
Summary: We examine the responses of a range of meteorological and air quality indicators to the expansion of urban land using WRF/Chem. Sensitivity studies indicate that the responses of pollutant concentrations to the spatial extent of urbanization are linear near the surface but nonlinear at higher altitudes. The results of process analysis demonstrate that urban heat island circulation and a deeper boundary layer with stronger turbulent intensities play a significant role in relocating pollutants.
Atmos. Chem. Phys., 15, 8597-8614, doi:10.5194/acp-15-8597-2015, 2015
Uncertainties in global aerosols and climate effects due to biofuel emissions
Summary: We examine sensitivities in aerosol concentration and climate effects from biofuel combustion emissions. We find a strong sensitivity in the overall sign and magnitude of the direct radiative effect and cloud-albedo indirect effect due to uncertainties regarding emissions size distribution, composition, mass, and optical mixing state. This uncertainty limits our ability to evaluate black carbon mitigation strategies to counter warming effects from greenhouse gases.
Atmos. Chem. Phys., 15, 8577-8596, doi:10.5194/acp-15-8577-2015, 2015
Relationships between photosynthesis and formaldehyde as a probe of isoprene emission
Summary: We apply two global observational data sets, gross primary productivity (GPP) and tropospheric formaldehyde column variability (HCHOv), to probe isoprene emission variability on large spatiotemporal scales. GPP and HCHOv are decoupled or weakly anticorrelated in regions and seasons when isoprene emission is high. Isoprene emission models that include soil moisture dependence demonstrate greater skill in reproducing observed seasonal GPP-HCHOv correlations in the southeast US and the Amazon.
Atmos. Chem. Phys., 15, 8559-8576, doi:10.5194/acp-15-8559-2015, 2015
Using SEVIRI fire observations to drive smoke plumes in the CMAQ air quality model: a case study over Antalya in 2008
Summary: We investigate the quality of fire emission estimates derived from SEVIRI FRP for air quality simulations with the Community Multiscale Air Quality (CMAQ) model, by comparing them with available MODIS FRP-based ones. We demonstrate that geostationary observations allow for refining biomass burning emissions, which can subsequently be used in regional scale air quality models in order to improve the prediction of chemical composition of the atmosphere in presence of large fire episodes.
Atmos. Chem. Phys., 15, 8539-8558, doi:10.5194/acp-15-8539-2015, 2015
Two decades of water vapor measurements with the FISH fluorescence hygrometer: a review
Atmos. Chem. Phys., 15, 8521-8538, doi:10.5194/acp-15-8521-2015, 2015
Advances in understanding mineral dust and boundary layer processes over the Sahara from Fennec aircraft observations
Summary: Measurements of the Saharan atmosphere and of atmospheric mineral dust are lacking but are vital to our understanding of the climate of this region and their impacts further afield. Novel observations were made by the Fennec climate programme during June 2011 and 2012 using ground-based, remote sensing and airborne platforms. Here we describe the airborne observations and the contributions they have made to furthering our understanding of the Saharan climate system.
Atmos. Chem. Phys., 15, 8479-8520, doi:10.5194/acp-15-8479-2015, 2015
Global distributions of overlapping gravity waves in HIRDLS data
Summary: Data from the HIRDLS instrument are used to study the numerical variability of gravity waves. Observed distributions are dominated by long-vertical-short-horizontal-wavelength waves, with a similar spectral form at all locations. We further divide our data into subspecies by wavelength, and investigate variation in these subspecies in time and space. We show that the variations associated with particular phenomena arise due to changes in specific parts of the spectrum.
Atmos. Chem. Phys., 15, 8459-8477, doi:10.5194/acp-15-8459-2015, 2015
X-ray computed microtomography of sea ice – comment on "A review of air–ice chemical and physical interactions (AICI): liquids, quasi-liquids, and solids in snow" by Bartels-Rausch et al. (2014)
Summary: This paper, "X-ray computed microtomography of sea ice" is a comment on a recent paper, "A review of air–ice chemical and physical interactions (AICI): liquids, quasi-liquids, and solids in snow (Atmos. Chem. Phys., 14, 1587–1633, 2014)". Our paper corrects a part of the review paper, which was inaccurate regarding the capabilities of X-ray computed microtomography to reveal liquid brine inclusions in sea ice.
Atmos. Chem. Phys., 15, 8457-8458, doi:10.5194/acp-15-8457-2015, 2015
Corrigendum to "In situ vertical profiles of aerosol extinction, mass, and composition over the southeast United States during SENEX and SEAC4RS: observations of a modest aerosol enhancement aloft" published in Atmos. Chem. Phys., 15, 7085–7102, 2015
Atmos. Chem. Phys., 15, 8455-8455, doi:10.5194/acp-15-8455-2015, 2015
Observations of relative humidity effects on aerosol light scattering in the Yangtze River Delta of China
Summary: The aerosol hygroscopic properties at a rural background site in the Yangtze River delta of China was discussed. The results show the scattering coefficient and backscattering coefficient increased by 58 and 25% as relative humidity (RH) increased from 40 to 85%, while the hemispheric backscatter fraction decreased by 21%. Aerosol hygroscopic growth caused a 47% increase in calculated aerosol direct radiative forcing at 85% RH compared to the forcing at 40% RH. Nitrate played a vital role.
Atmos. Chem. Phys., 15, 8439-8454, doi:10.5194/acp-15-8439-2015, 2015
On the ability of a global atmospheric inversion to constrain variations of CO2 fluxes over Amazonia
Atmos. Chem. Phys., 15, 8423-8438, doi:10.5194/acp-15-8423-2015, 2015
Aerosol chemistry above an extended archipelago of the eastern Mediterranean basin during strong northern winds
Summary: A model system is evaluated versus ground and airborne aerosol measurements, towards the identification of its competencies and deficiencies over the eastern Mediterranean (EM) during summer. Secondary organic aerosol (OA) formation is investigated towards improving OA behaviour. Biomass burning is a significant particle source, largely explaining OA underestimation (ca. 50%). More than 70% of the aerosol mass over the EM is related to trans-boundary transport during strong northeastern winds.
Atmos. Chem. Phys., 15, 8401-8421, doi:10.5194/acp-15-8401-2015, 2015
Temporal variations of flux and altitude of sulfur dioxide emissions during volcanic eruptions: implications for long-range dispersal of volcanic clouds
Summary: IASI spaceborne imagery is used to reconstruct temporal variations of flux and altitude of volcanic emissions via an inversion procedure. Ground-based UV measurements underestimate the SO2 flux by 1 order of magnitude due to ash-induced plume opacity. Assimilation of SO2 altitude, retrieved directly from IASI, should render the inversion scheme independent of the wind shear prerequisite. CALIOP LiDAR observations support the coexistence of SO2 and sulfate aerosols in the volcanic cloud.
Atmos. Chem. Phys., 15, 8381-8400, doi:10.5194/acp-15-8381-2015, 2015
The impact of speciated VOCs on regional ozone increment derived from measurements at the UK EMEP supersites between 1999 and 2012
Summary: In this study the regional component of ground level ozone is linked to the chemical loss of 27 measured VOCs at two UK monitoring sites and integrated with gridded European VOC emissions. The relative VOC chemical loss indicates that emission controls of a large number of VOCs and targeting VOCs with highest chemical loss are both required to reduce regional ozone. The benefit resulting from the disaggregation of VOC source sectors to the identification of high VOC-emitting sources is shown.
Atmos. Chem. Phys., 15, 8361-8380, doi:10.5194/acp-15-8361-2015, 2015
Black carbon emissions from Russian diesel sources: case study of Murmansk
Summary: We estimated BC emissions from diesel sources in Murmansk Region and Murmansk City, the largest city in the Arctic. We developed a detailed inventory including on-road vehicles, off-road transport (mining, locomotives, construction and agriculture), fishing and diesel generators. We conducted several surveys to understand the vehicle fleet and driving patterns. BC emissions in Murmansk Region were 0.40 Gg in 2012. Total BC emissions from diesel sources in Russia estimated at 50.8 Gg in 2010.
Atmos. Chem. Phys., 15, 8349-8359, doi:10.5194/acp-15-8349-2015, 2015
A tropospheric chemistry reanalysis for the years 2005–2012 based on an assimilation of OMI, MLS, TES, and MOPITT satellite data
Summary: This paper reports on an 8-year reanalysis of tropospheric chemistry based on an assimilation of multiple satellite-derived data sets. The reanalysis performed well on regional and global scales and for seasonal and interannual variations. The simultaneous assimilation of multiple-species data, involving the optimisation of both concentration and emission fields, provides unique information on year-to-year variations in the atmospheric environment.
Atmos. Chem. Phys., 15, 8315-8348, doi:10.5194/acp-15-8315-2015, 2015
Formation and aging of secondary organic aerosol from toluene: changes in chemical composition, volatility, and hygroscopicity
Summary: Secondary organic aerosol (SOA) is transformed after its initial formation. We explored the effects of this chemical aging on the composition, mass yield, volatility, and hygroscopicity of SOA formed from the photo-oxidation of small aromatic volatile organic compounds. Higher exposure to the hydroxyl radical resulted in different SOA composition, average carbon oxidation state, and mass yield. The vapor pressure of SOA formed under different conditions varied by as much as a factor of 30.
Atmos. Chem. Phys., 15, 8301-8313, doi:10.5194/acp-15-8301-2015, 2015
Particulate matter, air quality and climate: lessons learned and future needs
Summary: Particulate matter (PM) constitutes one of the most challenging problems both for air quality and climate change policies. This paper reviews the most recent scientific results on the issue and the policy needs that have driven much of the increase in monitoring and mechanistic research over the last 2 decades. The synthesis reveals many new processes and developments in the science underpinning climate-PM interactions and the effects of PM on human health and the environment.
Atmos. Chem. Phys., 15, 8217-8299, doi:10.5194/acp-15-8217-2015, 2015
Climate responses to anthropogenic emissions of short-lived climate pollutants
Summary: We investigate the impact of removing land-based anthropogenic emissions of three aerosol species, using four fully-coupled atmosphere-ocean global climate models. Removing SO2 emissions leads to warming globally, strongest in the Northern Hemisphere (NH), and an increase in NH precipitation. Organic and black carbon (OC, BC) have a weaker impact, and less certainty on the response; OC (BC) removal shows a weak overall warming (cooling), and both show small increases in precipitation globally.
Atmos. Chem. Phys., 15, 8201-8216, doi:10.5194/acp-15-8201-2015, 2015
Night-time measurements of HOx during the RONOCO project and analysis of the sources of HO2
Atmos. Chem. Phys., 15, 8179-8200, doi:10.5194/acp-15-8179-2015, 2015
Characteristics and formation mechanism of continuous hazes in China: a case study during the autumn of 2014 in the North China Plain
Atmos. Chem. Phys., 15, 8165-8178, doi:10.5194/acp-15-8165-2015, 2015
Airborne observations and simulations of three-dimensional radiative interactions between Arctic boundary layer clouds and ice floes
Atmos. Chem. Phys., 15, 8147-8163, doi:10.5194/acp-15-8147-2015, 2015
Water soluble aerosols and gases at a UK background site – Part 1: Controls of PM2.5 and PM10 aerosol composition
Summary: Hourly inorganic composition of UK background particulate matter (PM10 and PM2.5) has been studied for a 6.5-year period at Auchencorth Moss, Scotland. Long-range transport of both anthropogenic secondary and natural primary PM is observed, driven primarily by meteorology. The importance of nitrate, sulfate and ammonium during pollution events in the UK is demonstrated.
Atmos. Chem. Phys., 15, 8131-8145, doi:10.5194/acp-15-8131-2015, 2015
MACC regional multi-model ensemble simulations of birch pollen dispersion in Europe
Summary: The paper presents the first ensemble modelling experiment for forecasting the atmospheric dispersion of birch pollen in Europe. The study included 7 models of MACC-ENS tested over the season of 2010 and applied for 2013 in forecasting and reanalysis modes. The results were compared with observations in 11 countries, members of European Aeroallergen Network. The models successfully reproduced the timing of the unusually late season of 2013 but had more difficulties with absolute concentration.
Atmos. Chem. Phys., 15, 8115-8130, doi:10.5194/acp-15-8115-2015, 2015
Peroxynitric acid (HO2NO2) measurements during the UBWOS 2013 and 2014 studies using iodide ion chemical ionization mass spectrometry
Summary: In this paper laboratory work is documented establishing iodide ion chemical ionization mass spectrometry (I- CIMS) as a sensitive method for the unambiguous detection of peroxynitric acid (HO2NO2; PNA). A dynamic calibration source for HO2NO2, HO2, and HONO was developed and calibrated using a novel total NOy detector (NOy CaRDS). The ambient observations of HO2NO2 using I- CIMS made during the 2013 and 2014 Uintah Basin Wintertime Ozone Study (UBWOS) are presented.
Atmos. Chem. Phys., 15, 8101-8114, doi:10.5194/acp-15-8101-2015, 2015
Mapping gas-phase organic reactivity and concomitant secondary organic aerosol formation: chemometric dimension reduction techniques for the deconvolution of complex atmospheric data sets
Summary: This paper describes a new ensemble methodology for the statistical analysis of atmospheric gas- & particle-phase composition data sets. The methodology reduces the huge amount of data derived from many chamber experiments to show that organic reactivity & resultant particle formation can be mapped into unique clusters in statistical space. The model generated is used to map more realistic plant mesocosm oxidation data, the projection of which gives insight into reactive pathways & precursors.
Atmos. Chem. Phys., 15, 8077-8100, doi:10.5194/acp-15-8077-2015, 2015
Partitioning and budget of inorganic and organic chlorine species observed by MIPAS-B and TELIS in the Arctic in March 2011
Atmos. Chem. Phys., 15, 8065-8076, doi:10.5194/acp-15-8065-2015, 2015
Increasing Arabian dust activity and the Indian summer monsoon
Summary: Using observations and a regional climate model, we suggest that (i) dust radiative forcing over west Asia induces complex regional feedbacks on the Indian monsoon system, notably a possible enhancement of moisture convergence over southern India; and (ii) an observed AOD positive trend attributed to an increasing Arabian dust activity during 2000-2009 could be associated with, and contributing to, the observed enhancement of southern Indian summer precipitation during this decade.
Atmos. Chem. Phys., 15, 8051-8064, doi:10.5194/acp-15-8051-2015, 2015
Tropospheric ozone variability in the tropics from ENSO to MJO and shorter timescales
Summary: Aura OMI and MLS measurements are combined to produce daily maps of tropospheric ozone beginning October 2004. We show that El Niño Southern Oscillation (ENSO) related inter-annual change in tropospheric ozone in the tropics is small compared to combined intra-seasonal/Madden-Julian Oscillation (MJO) and shorter timescale variability. Outgoing Longwave Radiation indicates that deep convection is the primary driver of the observed ozone variability on all timescales.
Atmos. Chem. Phys., 15, 8037-8049, doi:10.5194/acp-15-8037-2015, 2015
Source contributions to 2012 summertime aerosols in the Euro-Mediterranean region
Atmos. Chem. Phys., 15, 8013-8036, doi:10.5194/acp-15-8013-2015, 2015
Laboratory photochemical processing of aqueous aerosols: formation and degradation of dicarboxylic acids, oxocarboxylic acids and α-dicarbonyls
Atmos. Chem. Phys., 15, 7999-8012, doi:10.5194/acp-15-7999-2015, 2015
Uncertainties in isoprene photochemistry and emissions: implications for the oxidative capacity of past and present atmospheres and for climate forcing agents
Summary: The atmosphere’s oxidative capacity determines the lifetime of many trace gases important to climate, chemistry, and human health. Yet uncertainties remain about its past variations, its controlling factors, and the radiative forcing of short-lived species it influences. To reduce these uncertainties, we must better quantify the natural emissions and chemical reaction mechanisms of organic compounds in the atmosphere, which play a role in governing the oxidative capacity.
Atmos. Chem. Phys., 15, 7977-7998, doi:10.5194/acp-15-7977-2015, 2015
Primary marine aerosol emissions from the Mediterranean Sea during pre-bloom and oligotrophic conditions: correlations to seawater chlorophyll a from a mesocosm study
Summary: The effect of ocean acidification and changing water conditions on primary (and secondary) marine aerosol emissions is not well understood on a regional or a global scale. To investigate this effect, we deployed mesocosms in the Mediterranean Sea for several weeks during both winter pre-bloom and summer oligotrophic conditions and subjected them to various levels of CO2. We observed larger effects due to the differences between a pre-bloom and oligotrophic environment than due to CO2 levels.
Atmos. Chem. Phys., 15, 7961-7976, doi:10.5194/acp-15-7961-2015, 2015
Characterization of ambient volatile organic compounds and their sources in Beijing, before, during, and after Asia-Pacific Economic Cooperation China 2014
Summary: Ambient VOCs were measured at an urban site in Beijing before, during, and after APEC China 2014, when air quality control measures were implemented. PMF was applied to identify the major VOCs sources and their temporal variations. SOAP approach was used to estimate variations of precursor source contributions to SOA . Our results indicate that the stringent air quality restrictions have been successful, and controls on vehicles were the most important measures to VOCs.
Atmos. Chem. Phys., 15, 7945-7959, doi:10.5194/acp-15-7945-2015, 2015
Smoke aerosol properties and ageing effects for northern temperate and boreal regions derived from AERONET source and age attribution
Summary: The study found significant differences in smoke plumes attributed to different vegetation type fires in northern temperate and boreal regions. Plume particle sizes and optical properties varied not only when comparing grass and forest emissions, but also plumes from different forest types. Particles were found to increase in size in ageing plumes. Determined growth rates were significant and consistent between the emissions of different origin.
Atmos. Chem. Phys., 15, 7929-7943, doi:10.5194/acp-15-7929-2015, 2015
The impact of parameterising light penetration into snow on the photochemical production of NOx and OH radicals in snow
Atmos. Chem. Phys., 15, 7913-7927, doi:10.5194/acp-15-7913-2015, 2015
Aerosol forecast over the Mediterranean area during July 2013 (ADRIMED/CHARMEX)
Summary: The atmospheric composition was extensively studied in the European Mediterranean region and during summer 2013 within the framework of the ADRIMED project. During the campaign experiment, the WRF and CHIMERE models were used in forecast mode in order to help scientists to decide whether intensive observation periods should be triggered or not. This study quantifies the origin of the forecast error by comparing several forecast leads to the corresponding measurements.
Atmos. Chem. Phys., 15, 7897-7911, doi:10.5194/acp-15-7897-2015, 2015
Overview of receptor-based source apportionment studies for speciated atmospheric mercury
Summary: Current knowledge of receptor-based studies using speciated atmospheric mercury is reviewed and recommendations for future research needs are provided.
Atmos. Chem. Phys., 15, 7877-7895, doi:10.5194/acp-15-7877-2015, 2015
Atmospheric nitrogen oxides (NO and NO2) at Dome C, East Antarctica, during the OPALE campaign
Summary: Surprisingly large concentrations and flux of atmospheric nitrogen oxides were measured at Dome C, East Antarctica. It was found that the surface snow holds a significant reservoir of photochemically produced NOx and is a sink of gas-phase ozone. Main drivers of NOx snow emissions were large snow nitrate concentrations, with contributions of increased UV from decreases in stratospheric ozone. Observed halogen and hydroxyl radical concentrations were too low to explain large NO2:NO ratios.
Atmos. Chem. Phys., 15, 7859-7875, doi:10.5194/acp-15-7859-2015, 2015
Brown carbon aerosol in the North American continental troposphere: sources, abundance, and radiative forcing
Summary: Brown carbon (BrC) is found throughout the US continental troposphere during a summer of extensive biomass burning and its prevalence relative to black carbon (BC) increases with altitude. A radiative transfer model based on direct measurements of aerosol scattering and absorption by BC and BrC shows BrC reduces top-of-atmosphere forcing by 20%. A method to estimate BrC radiative forcing efficiencies from surface-based measurements is provided.
Atmos. Chem. Phys., 15, 7841-7858, doi:10.5194/acp-15-7841-2015, 2015
Formation of hydroxyl radicals from photolysis of secondary organic aerosol material
Summary: This is the first paper to demonstrate that SOA material forms OH radicals upon UV illumination. We quantify the OH formation rates in solution and show species other than H2O2, mostly probably ROOH molecules, are the likely source of the OH. The importance of an OH source from SOA is that photochemical processing within both cloudwater and aerosol particles may arise subsequent to the formation of these radicals.
Atmos. Chem. Phys., 15, 7831-7840, doi:10.5194/acp-15-7831-2015, 2015
Changing shapes and implied viscosities of suspended submicron particles
Summary: The present work estimates the viscosity of submicron organic particles while they are still suspended as an aerosol without further post-processing techniques that can possibly alter the properties of semi-volatile materials. Results imply that atmospheric particles, at least those similar to the ones of this study and for low- to middle-RH regimes, can reach equilibrium or react rather slowly with the surrounding gas phase on time scales even longer than the residence time in the atmosphere.
Atmos. Chem. Phys., 15, 7819-7829, doi:10.5194/acp-15-7819-2015, 2015
The southern stratospheric gravity wave hot spot: individual waves and their momentum fluxes measured by COSMIC GPS-RO
Summary: In nearly all GCMs, unresolved gravity wave (GW) drag may cause the southern stratospheric winter polar vortex to break down too late. Here, we characterise GWs in this region of the atmosphere using GPS radio occultation. We find GWs may propagate into the region from other latitudes. We develop a new quantitative wave identification method to learn about regional wave populations. We also find intense GW momentum fluxes over the southern Andes and Antarctic Peninsula GW hot spot.
Atmos. Chem. Phys., 15, 7797-7818, doi:10.5194/acp-15-7797-2015, 2015
Seasonal and diurnal trends in concentrations and fluxes of volatile organic compounds in central London
Summary: Concentrations and fluxes of selected volatile organic compounds were measured over a 5-month period in central London as part of the ClearfLo project using a proton transfer reaction mass spectrometer. Emission sources within the city were inferred from spatio-temporal patterns and showed a detectable biogenic source during warmer months, which was modelled using the Guenther 95 algorithm. Comparisons were made with the local emissions inventories showing mostly underestimated emissions.
Atmos. Chem. Phys., 15, 7777-7796, doi:10.5194/acp-15-7777-2015, 2015
Phase partitioning and volatility of secondary organic aerosol components formed from α-pinene ozonolysis and OH oxidation: the importance of accretion products and other low volatility compounds
Summary: We measured a large suite organic compounds using a recently developed Filter Inlet for Gases and AEROsols (FIGAERO) coupled to a (HR-ToF-CIMS). The instrument was deployed on environmental simulation chambers to study monoterpene oxidation as a secondary organic aerosol (SOA) source. We find that approximately 50% of the detected particle phase mass is associated with compounds having effective vapor pressures 4, or more, orders of magnitude lower than commonly measured products.
Atmos. Chem. Phys., 15, 7765-7776, doi:10.5194/acp-15-7765-2015, 2015
Water vapour profiles from Raman lidar automatically calibrated by microwave radiometer data during HOPE
Summary: We present a method to derive water vapour profiles from Raman lidar measurements calibrated by the integrated water vapour from a collocated microwave radiometer. These simultaneous observations provide an operational and continuous measurement of water vapour profiles. The stability of the calibration factor allows for the calibration of the lidar even in the presence of clouds. Based on this approach, water vapour profiles can be retrieved during all non-precipitating conditions.
Atmos. Chem. Phys., 15, 7753-7763, doi:10.5194/acp-15-7753-2015, 2015
Particle size-resolved source apportionment of primary and secondary organic tracer compounds at urban and rural locations in Spain
Summary: Molecular organic tracer compounds were analyzed in six particle sizes in an urban background site (Barcelona) and in a rural site in Spain. The results improve considerably our current understanding on the composition and particle-size distribution of organic air pollution in traffic intensive urban areas and rural sites where combustion of biomass plays an important role on the local and regional air quality, either by emissions from open fires or from domestic heating.
Atmos. Chem. Phys., 15, 7735-7752, doi:10.5194/acp-15-7735-2015, 2015
Deriving polarization properties of desert-reflected solar spectra with PARASOL data
Atmos. Chem. Phys., 15, 7725-7734, doi:10.5194/acp-15-7725-2015, 2015
Climate-forced air-quality modeling at the urban scale: sensitivity to model resolution, emissions and meteorology
Summary: The efficacy of emission policies is explored by coarse resolution modeling applications. These were shown to be biased, overestimating that efficacy indicated in simulations with refined resolution. In order to improve our assessments, we need to quantify those biases. In this study we show that the ozone bias of the coarse run is reduced by 40% by adopting higher resolution emissions. For PM2.5, the coarse run cannot selectively incorporate local scale features in order to reduce model error.
Atmos. Chem. Phys., 15, 7703-7723, doi:10.5194/acp-15-7703-2015, 2015
Estimates of black carbon emissions in the western United States using the GEOS-Chem adjoint model
Atmos. Chem. Phys., 15, 7685-7702, doi:10.5194/acp-15-7685-2015, 2015
Aircraft measurements of gravity waves in the upper troposphere and lower stratosphere during the START08 field experiment
Summary: Based on spectral and wavelet analyses, along with a diagnosis of the polarization relations, this study analyzes in situ airborne measurements from the 2008 Stratosphere-Troposphere Analyses of Regional Transport (START08) experiment to characterize gravity waves in the extratropical upper troposphere and lower stratosphere (ExUTLS) region. The focus is on the second research flight (RF02), which was dedicated to probing gravity waves associated with strong upper-tropospheric jet-front systems.
Atmos. Chem. Phys., 15, 7667-7684, doi:10.5194/acp-15-7667-2015, 2015
An objective determination of optimal site locations for detecting expected trends in upper-air temperature and total column ozone
Summary: This manuscript aims to answer the following question: which of the existing sites engaged in upper-air temperature measurements are best located to detect expected future trends within the shortest time possible? To do so, we explore one objective method for selecting the optimal locations for detecting projected 21st century trends and then demonstrate a similar technique for objectively selecting optimal locations for detecting expected future trends in total column ozone.
Atmos. Chem. Phys., 15, 7653-7665, doi:10.5194/acp-15-7653-2015, 2015
Ground-based aerosol climatology of China: aerosol optical depths from the China Aerosol Remote Sensing Network (CARSNET) 2002–2013
Summary: This work studied more than 10 years of measurements of aerosol optical depths (AODs) made for 50 sites of CARSNET compiled into a climatology of aerosol optical properties for China. It lets us see a detailed full-scale description of AOD observations over China. The results would benefit us a lot in comprehending the temporal and special distribution aerosol optical property over China. Also the data would be valuable to communities of aerosol satellite retrieval, modelling, etc.
Atmos. Chem. Phys., 15, 7619-7652, doi:10.5194/acp-15-7619-2015, 2015
A comprehensive investigation on afternoon transition of the atmospheric boundary layer over a tropical rural site
Summary: The afternoon-evening transition (AET) in the atmospheric boundary layer has been studied in an integrated approach using 3 years of tower, sodar and wind profiler measurements. Such a long-term data set has been used for the first time to understand the behavior of AET. It allowed us to study the seasonal variation. In contrast to the common belief that the transition evolves from bottom to top, the present study clearly showed that the start time of transition follows top-to-bottom evolution.
Atmos. Chem. Phys., 15, 7605-7617, doi:10.5194/acp-15-7605-2015, 2015
The relationship between cloud condensation nuclei (CCN) concentration and light extinction of dried particles: indications of underlying aerosol processes and implications for satellite-based CCN estimates
Atmos. Chem. Phys., 15, 7585-7604, doi:10.5194/acp-15-7585-2015, 2015
Reassessing the ratio of glyoxal to formaldehyde as an indicator of hydrocarbon precursor speciation
Atmos. Chem. Phys., 15, 7571-7583, doi:10.5194/acp-15-7571-2015, 2015
Wet scavenging limits the detection of aerosol effects on precipitation
Summary: Wet scavenging generates differences between the aerosol properties in clear-sky scenes (observed by satellites) and cloudy scenes, leading to different aerosol-precipitation relationships in satellite data and global models. Convective systems usually draw in air from clear-sky regions, but global models have difficulty separating this aerosol from the aerosol in cloudy scenes within a model gridbox. This may prevent models from reproducing the observed aerosol-precipitation relationships.
Atmos. Chem. Phys., 15, 7557-7570, doi:10.5194/acp-15-7557-2015, 2015
Technical Note: Using DEG-CPCs at upper tropospheric temperatures
Atmos. Chem. Phys., 15, 7547-7555, doi:10.5194/acp-15-7547-2015, 2015
The role of blowing snow in the activation of bromine over first-year Antarctic sea ice
Summary: This work analyzes the chemical composition of blowing snow collected over first-year Antarctic sea ice to assess its role in bromine activation during the polar sunrise. We found lofted snow to be depleted in Br- relative to Cl- by proportionally increasing amounts with height. This is the first study to use field data to substantiate modeling results implicating blowing snow as the location for initial halogen activation. We also found lofted snow to be depleted in SO4 and enriched in NO3.
Atmos. Chem. Phys., 15, 7537-7545, doi:10.5194/acp-15-7537-2015, 2015
Deposition and immersion-mode nucleation of ice by three distinct samples of volcanic ash
Summary: Fine volcanic ash can influence cloud glaciation and, therefore, global climate. In this work we examined the heterogeneous ice nucleation properties of three distinct types of volcanic ash. We find that, in contrast to previous studies, these volcanic ash samples have different ice nucleation properties in the immersion mode. In the deposition mode, however, they nucleate ice with similar efficiency. We show that this behavior may be due to their mineralogy.
Atmos. Chem. Phys., 15, 7523-7536, doi:10.5194/acp-15-7523-2015, 2015
Secondary organic aerosol formation from the β-pinene+NO3 system: effect of humidity and peroxy radical fate
Summary: Laboratory chamber studies were conducted to investigate the formation of secondary organic aerosol from β-pinene oxidation by nitrate radicals. These experiments probed the effects of peroxy radical fate and relative humidity on the mass and chemical composition of secondary organic aerosol formed from nighttime chemistry. Results from this study were used to evaluate the contributions of NO3+monoterpene reaction to ambient organic aerosol recently measured in the southeastern United States.
Atmos. Chem. Phys., 15, 7497-7522, doi:10.5194/acp-15-7497-2015, 2015
A modified micrometeorological gradient method for estimating O3 dry depositions over a forest canopy
Summary: In this study, we have developed a modified micrometeorological gradient method (MGM), although based on existing micrometeorological theory, to estimate O3 dry deposition fluxes over a forest canopy using concentration gradients between a level above and a level below the canopy top. The new method provides an alternative approach in monitoring/estimating long-term deposition fluxes of similar pollutants over tall canopies and is expected to be useful for the scientific community.
Atmos. Chem. Phys., 15, 7487-7496, doi:10.5194/acp-15-7487-2015, 2015
Modulation of Saharan dust export by the North African dipole
Summary: Long-term 28-year variability of Saharan dust export to the Atlantic is correlated with large-scale meteorology in North Africa, particularly with the intensity of the Saharan high to tropical low dipole-like pattern, the so-called North African Dipole. Variability in the dipole intensity is connected with winds, monsoon rain band and latitudinal shifts of the Saharan air layer. Variability in the dipole intensity suggests connections with ENSO and the Sahel drought.
Atmos. Chem. Phys., 15, 7471-7486, doi:10.5194/acp-15-7471-2015, 2015
Stably stratified canopy flow in complex terrain
Atmos. Chem. Phys., 15, 7457-7470, doi:10.5194/acp-15-7457-2015, 2015
Technical Note: A novel parameterization of the transmissivity due to ozone absorption in the k-distribution method and correlated-k approximation of Kato et al. (1999) over the UV band
Summary: A novel model of the absorption of radiation by ozone in the UV bands [283, 307]nm and [307, 328]nm yields improvements in the modeling of the transmissivity in these bands. This model is faster than detailed spectral calculations and is as accurate with maximum errors of respectively 0.0006 and 0.0143. How to practically implement this new parameterization in a radiative transfer model is discussed for the case of libRadtran.
Atmos. Chem. Phys., 15, 7449-7456, doi:10.5194/acp-15-7449-2015, 2015
Sensitivities of Lagrangian modelling of mid-latitude cirrus clouds to trajectory data quality
Summary: Sensitivities of Lagrangian cirrus modelling on input data uncertainties have been examined. We found a strong dependence on the temporal resolution of the trajectories and underlying numerical weather prediction (NWP) data as well as on the specific moisture content. Furthermore, we found a large day-to-day variability in the vertical wind spectrum, demonstrating the necessity to apply NWP models with high spatial and temporal resolution for Lagrangian cirrus modelling.
Atmos. Chem. Phys., 15, 7429-7447, doi:10.5194/acp-15-7429-2015, 2015
An ecosystem-scale perspective of the net land methanol flux: synthesis of micrometeorological flux measurements
Summary: Methanol is the second most abundant volatile organic compound in the troposphere and plays a significant role in atmospheric chemistry. While there is consensus about the dominant role of plants as the major source and the reaction with OH as the major sink, global methanol budgets diverge considerably in terms of source/sink estimates. Here we present micrometeorological methanol flux data from eight sites in order to provide a first cross-site synthesis of the terrestrial methanol exchange.
Atmos. Chem. Phys., 15, 7413-7427, doi:10.5194/acp-15-7413-2015, 2015
Comparison of OMI UV observations with ground-based measurements at high northern latitudes
Summary: Surface erythemal UV data from the Ozone Monitoring Instrument (OMI) are validated for high northern latitudes (Arctic and Scandinavia) using ground-based measurements. The bias in OMI data caused by incorrect assumptions of the surface albedo are quantified and the mechanism that causes this bias is discussed. Methods to improve the accuracy of OMI data products are presented.
Atmos. Chem. Phys., 15, 7391-7412, doi:10.5194/acp-15-7391-2015, 2015
Large-eddy simulation of contrail evolution in the vortex phase and its interaction with atmospheric turbulence
Atmos. Chem. Phys., 15, 7369-7389, doi:10.5194/acp-15-7369-2015, 2015
On the reversibility of transitions between closed and open cellular convection
Summary: Most research on the relationship between aerosol and closed/open cell transitions tends to focus on the closed to open transition. Here we address the two-way transition between closed and open cellular states using a cloud resolving model. We find inherent asymmetry in the transitions and explain the source of the asymmetry. Results are supported by a dynamical system analogue to the full system.
Atmos. Chem. Phys., 15, 7351-7367, doi:10.5194/acp-15-7351-2015, 2015
Characterisation of J(O1D) at Cape Grim 2000–2005
Summary: Measurements of the photolysis rates which drive production of OH from ozone are reported for Cape Grim, a "clean-air" site in the southern midlatitudes. This remote maritime site sits in the Southern Ocean, a region of the globe which is little studied. From the 6 years of data the dependence of this photolysis on solar zenith angle and stratospheric ozone is determined. Included with the reported values is an estimate of the uncertainties in these measurements.
Atmos. Chem. Phys., 15, 7337-7349, doi:10.5194/acp-15-7337-2015, 2015
Aerosol characterization over the southeastern United States using high-resolution aerosol mass spectrometry: spatial and seasonal variation of aerosol composition and sources with a focus on organic nitrates
Summary: Year-long comprehensive characterization of ambient aerosol was performed in both rural and urban sites in the southeastern US as part of Southeastern Center of Air Pollution and Epidemiology (SCAPE) study and Southeastern Oxidant and Aerosol Study (SOAS). Three independent methods were applied to estimate the concentration of particle-phase organic nitrates. The spatial distribution of organic aerosol is investigated by comparing simultaneous HR-ToF-AMS and ACSM measurements at different sites.
Atmos. Chem. Phys., 15, 7307-7336, doi:10.5194/acp-15-7307-2015, 2015
On the scaling of the solar incident flux
Summary: Varotsos et al. (Theor. Appl. Climatol., 114, 725–727, 2013) found that the solar ultraviolet (UV) wavelengths exhibit 1/f-type power-law correlations. In this study, we show that the residues of the spectral solar incident flux with respect to the Planck law over a wider range of wavelengths (i.e. UV-visible) have a scaling regime too.
Atmos. Chem. Phys., 15, 7301-7306, doi:10.5194/acp-15-7301-2015, 2015
800-year ice-core record of nitrogen deposition in Svalbard linked to ocean productivity and biogenic emissions
Summary: Nitrate and ammonium ice core records from Lomonosovfonna, Svalbard, indicated anthropogenic pollution from Eurasia as major source during the 20th century. In pre-industrial times nitrate is correlated with methane sulfonate, which we explain with a fertilising effect, presumably triggered by enhanced atmospheric nitrogen input to the ocean. Eurasia was likely the main source area also of pre-industrial nitrate, but for ammonium, biogenic emissions from Siberian boreal forests were dominant.
Atmos. Chem. Phys., 15, 7287-7300, doi:10.5194/acp-15-7287-2015, 2015