Aerosols from open fires could significantly perturb the global radiation balance and induce climate change. In this study, the CAM5 global climate model is used to investigate the spatial and seasonal characteristics of radiative effects due to fire aerosol–radiation interactions, fire aerosol-cloud interactions and fire aerosol-surface albedo interactions, including radiative effects from all fire aerosols, fire black carbon and fire particulate organic matter. Hide

Volatile organic compounds (VOCs) were monitored in urban backgrounds sites, in Athens and Patras in Greece. In summer most of the measured VOCs were due to biogenic and traffic emissions. Winter measurements in Athens revealed that biomass burning used for residential heating was the dominant VOC source. The biomass burning VOC emission ratios and emission factors were estimated. Hide

Recently, the winter haze pollution over the north central North China Plain has become severe. By treating the year-to-year increment as the predictand, two new statistical schemes were established using the multiple linear regression and the generalized additive model approaches. After cross validation, both of these models could capture the interannual and interdecadal trends and the extremums successfully. Independent tests for 2014 and 2015 also confirmed the good predictive skill. Hide

A reaction scheme representing the tropospheric ozone depletion events (ODEs) and the halogen chemistry in the Arctic spring was processed with two different mechanism reduction approaches. In the concentration sensitivity analysis, 11 reactions were removed while an additional 9 reactions were eliminated according to the principal component analysis. The results computed by applying the reduced reaction mechanisms derived after the analyses agree well with those when using the original scheme. Hide

The regional distributions and impacts of N₂O₅ and ClNO₂ remain poorly understood. To address the problem, we developed a chemical transport model further and conducted the first high-resolution simulation of the distributions of the two species. Our research demonstrated the significant impacts of the two gases on the lifetime of nitrogen oxides, secondary nitrate production and ozone formation in southern China and highlighted the necessity of considering this chemistry in air quality models. Hide

Methane is an important greenhouse gas. Methane emissions from Arctic wetlands are poorly quantified and may increase in a warming climate. Using a global atmospheric model and atmospheric observations of methane and its isotopologues, we find that isotopologue data are useful in constraining Arctic wetland emissions. Our results suggest that the seasonal cycle of these emissions may be incorrectly simulated in land process models, with implications for our understanding of future emissions. Hide

The role that soil, foliage, and atmospheric dynamics have on surface OCS exchange in a Mediterranean forest ecosystem in southern France (O3HP) was investigated in June of 2012 and 2013 with essentially a top-down approach. Atmospheric data suggest that the site is appropriate for estimating GPP directly from eddy covariance measurements of OCS fluxes, but it is less adequate for scaling NEE to GPP from observations of vertical gradients of OCS relative to CO₂ during the daytime. Hide

The study shows that the conventional steering calculated over a certain radius from the tropical cyclone center in the horizontal and a deep pressure layer in the vertical is not literally the steering or the advection of the symmetric potential vorticity component associated with a tropical cyclone by the asymmetric flow. The trochoidal motion around the mean tropical cyclone track cannot be accounted for by the effect of the conventional steering. Hide

This study deployed an AMS field study in Lanzhou, a city in northwestern China, evaluating the chemical composition, sources, and processes of urban aerosols during wintertime. In comparison with the results during summer in Lanzhou, the air pollution during winter was more severe and the sources were more complex. In addition, this paper estimates the contributions of fossil and non-fossil sources of organic carbon to primary and secondary organic carbon using the carbon isotopic method. Hide

This work addresses the unclear global significance of chlorine activation processes in the troposphere. The first high-quality measurement data set of ClNO₂ in northern China revealed strong ClNO₂ production in the residual layers, and demonstrated its significant effects on radical budget and ozone production. Our findings imply the widespread effects of ClNO₂ over the polluted regions of northern China, which may increase photochemical and haze pollution. Hide

Due to a lack of physical measurements at appropriate spatial and temporal scales, all current global maps of fossil fuel carbon dioxide (FFCO₂) emissions use one or more proxies to distribute those emissions. These proxies and distribution schemes introduce additional uncertainty into the maps. This paper examines the uncertainty associated with the magnitude of gridded FFCO₂ emissions and includes uncertainty contributions from the spatial, temporal, proxy, and magnitude components. Hide

Humans have altered the surface of the Earth since preindustrial times. These changes (largely expansion of croplands and pasturelands) have modified biosphere–atmosphere fluxes. In this study we use a global model to assess the impact of these changes on the formation of secondary particulate matter and troposphere ozone. We find that there are significant air quality and climate impacts associated with these changes. Hide

In this paper, we present our new findings on (1) the spatial and temporal characteristics of AH emissions in South China, (2) how to implement the inhomogeneous AH data into the air quality model WRF/Chem, (3) the impacts of AH fluxes on meteorological fields, and (4) the impacts of meteorology changes on the air quality in different cities in South China. Our results show that the meteorology and air pollution predictions in and around big cities are highly sensitive to AH. Hide

The analysis of temperatures in the mesopause region between 1988 to 2015 shows, besides the known correlation with the 11-year solar activity cycle, a trend reversal in 2008 that can be described by a long-term oscillation. Understanding such long periodic oscillations in the atmosphere is of prime importance for climate modelling and predictions of future trends. Hide

The atmospheric ozone layer is changing, thus the UV radiation at the surface is changing. Due to both beneficial and adverse effects of UV on the biosphere, monitoring of UV is essential. Satellite sensors provide estimates of UV at the surface with a global coverage. Validation of satellite-sensor UV is therefore needed and this can be done by comparison with ground-based measurements. The present validation in three sites (midlatitude, tropical) shows that OMI and GOME-2 provide reliable UV. Hide

We compare the immersion freezing behavior of four airborne to 11 surface-collected dust samples to investigate the role of different minerals for atmospheric ice nucleation on desert dust. We find that present K-feldspars dominate at T > 253 K, while quartz does at colder temperatures, and surface-collected dust samples are not necessarily representative for airborne dust. For improved ice cloud prediction, modeling of quartz and feldspar emission and transport are key. Hide

Mineral dust aerosol affects climate through interaction with radiation and clouds, human health through contribution to particulate matter, and ecosystem health through nutrient transport and deposition. In this study, we use satellite and in situ retrievals to derive an observational estimate of the global dust AOD with which evaluate modeled dust AOD. Differences in the seasonality and regional distribution of dust AOD between observations and models are highlighted. Hide

A better understanding of the discrepancies in multi-scale emission inventories could provide indications for their limitations and further improvements. We develop a bottom-up inventory of Hg emissions for Jiangsu, China. Compared to the national and global inventories, the largest total Hg emissions and fraction of Hg²⁺ are estimated. The crucial parameters responsible for the differences include Hg contents in coals/materials, abatement rates of emission control devices, and activity levels. Hide

Noctilucent clouds (NLCs) are ice clouds that form at the polar summer mesopause and are very sensitive to temperature. They may therefore provide a way to monitor this remote region as our atmosphere changes. We show that temperature variations in the mesosphere are crucial for the growth of ice particles and that average fields are not enough to describe the process of NLC development. The paper also emphasises the difficulties in retrieving ice particle properties from optical observations. Hide

Ozone (O₃) and carbon monoxide (CO) are two compounds of major importance in the atmosphere. In this paper we investigated their variability and trends at Frankfurt based on the MOZAIC–IAGOS dataset, a unique dataset of about 21 300 vertical profiles recorded by commercial aircraft. The CO concentrations have been decreasing since 2002, while no strong tendency is observed for O₃ since 1994. However, the O₃ seasonal variations are changing, with the spring maximum occurring earlier and earlier. Hide

We present an analysis of bioaerosol measurements using two real-time fluorescence instruments in combination with molecular tracer techniques for quantifying airborne fungal spores in a semi-arid forest. Both techniques provide fungal spore concentrations of the order of 10⁴ m⁻³ and up to 30 % of particle mass. Rainy periods exhibited higher concentrations and stronger correlations between fluorescent bioparticle and molecular tracer measurements. Fungal culture results are also presented. Hide

We characterize the aerosol physical and optical properties of biomass burning smoke observed at Mt. Bachelor Observatory in central Oregon during August 2015. We found differences in the light absorption properties of biomass burning aerosol depending on where the fire originated from and how long it was transported to the sampling site. We found that aerosol size distribution was not dependent on transport time but affected the light scattering properties of the aerosol. Hide

Understanding terrestrial carbon processes is a major challenge in climate science. We define the satellite system required to understand greenhouse gas biogeochemistry: our study is focused on Amazon wetland CH₄ emissions. We find that future geostationary satellites will provide the CH₄ measurements required to understand wetland CH₄ processes. Low-earth orbit satellites will be unable to resolve wetland CH₄ processes due to a low number of cloud-free CH₄ measurements over the Amazon basin. Hide

Satellite measurements of the atmosphere provide global information on pollutants that play an important role in air quality. These measurements require assumed knowledge about the vertical profile of these pollutants, which are often simulated at coarse resolution in space and time. We find that simulating these inputs with better spatial and temporal resolution alters individual measurements by up to 40 % and the average measurement by up to 13 %, and increases derived emissions by up to 100 %. Hide

This paper provides empirical evidence that the year-to-year variability of summertime ozone over Houston is linked to the Bermuda High (BH) large-scale circulation patterns. It identifies two BH indices that can explain up to 70 % of the interannual variability of summertime ozone in Houston and illustrates the mechanism underlying the BH and ozone linkage. Such a mechanism is tested for applicability to other coastal urban regions along the US Gulf Coast. Hide

The characteristics of ambient aerosol during two seasons (spring/autumn) and at two locations (suburban/urban) in Rome were investigated. We distinguished regionally advected and locally produced organic aerosols, including from cooking, traffic and biomass burning, but also from locally emitted cigarette smoke, for which we propose a new marker peak for identification in aerosol mass spectra. The impact of Saharan dust advection events on local aerosol concentration was studied. Hide

The identification of transport pathways from the Asian monsoon anticyclone into the lower stratosphere is unclear. Global simulations with the CLaMS model demonstrate that source regions in Asia and in the Pacific Ocean have a significant impact on the chemical composition of the lower stratosphere of the Northern Hemisphere by flooding the extratropical lower stratosphere with young moist air masses. Two main horizontal transport pathways from the Asian monsoon anticyclone are identified. Hide

Gas-particle partitioning is an important process that determines the fate and long-range transport potential of persistent organic pollutants. This work is the first effort to evaluate the behaviour of parameterizations within a regional air quality system adapted for Europe. Results corroborate the significance of the chosen implementation in predicting ambient levels and transport patterns. Implications point to improvements on the side of the emission inventories and aerosol module. Hide

Surface ozone concentrations in Mexico City frequently exceed the Mexican standard and have proven difficult to forecast due to changes in meteorological conditions at its tropical location. The Madden–Julian Oscillation (MJO) is largely responsible for intraseasonal variability in the tropics. Surface ozone in Mexico City is modulated by the MJO through its circulation pattern in the upper troposphere and its associated cloudiness, thus modulating solar radiation reaching the boundary layer. Hide

The 2015/16 Arctic winter stratosphere was the coldest on record through late February, raising the possibility of extensive chemical ozone loss. However, a major final sudden stratospheric warming in early March curtailed ozone destruction. We used Aura MLS satellite trace gas data and MERRA-2 meteorological data to show the details of transport, mixing, and dispersal of chemically processed air during the major final warming, and how these processes limited Arctic chemical ozone loss. Hide

We have investigated for the first time the heterogeneous hydrolysis of ClONO₂ on TiO₂ and SiO₂ aerosol particles at room temperature and at different relative humidities (RHs), using an aerosol flow tube. The kinetic data reported in our current and previous studies have been included in the UKCA chemistry–climate model to assess the impact of TiO₂ injection on stratospheric chemistry and stratospheric ozone in particular. Hide

This study identifies a fundamental flaw of a GCM in aerosol–cloud–precipitation interactions. The model predicts a monotonic increase in the LWP in response to increased aerosols, which is in stark contrast to satellite retrievals that show a regional variation in the sign of the LWP response. The model also fails to represent the observed dependency of the LWP response on macrophysical regimes. The model biases are attributed to the autoconversion process, with a lack of buffering mechanisms. Hide

This study provides new insight into the hydrolysis reaction mechanism, which was elucidated for atmospherically relevant organic nitrates using kinetic measurements, product identification, and theoretical calculations. The results help broaden our knowledge of the organic chemistry that impacts the fate of NO_x, ozone production, aerosol phase processing, and aerosol composition. Hide