Carbon tetrachloride is an ozone-depleting greenhouse gas banned under the Montreal Protocol. Measurements of atmospheric levels combined with global transport models indicate that it is still being emitted, in contrast to what is reported. In order to help solve the "mystery of carbon tetrachloride", we estimated European emissions during 2006–2014 using atmospheric observations and models. We identified emission hot spots and showed inconsistencies in national emission declarations. Hide

Atmospheric particulate matter (PM) levels and resulting impacts on human health are in the Po Valley (Italy) among the highest in Europe. This study discusses submicron PM chemical composition, sources and atmospheric processes in this region, using state-of-the-art measurement techniques and receptor models. Based on these results, effective PM abatement strategies are suggested in the upper Po Valley. Hide

Understanding of spatial and temporal variations of atmospheric speciated mercury can advance our knowledge of mercury cycling in various environments. This review summarized spatiotemporal variations of TGM/GEM, GOM, and PBM in environments including oceans, continents, high elevation, the free troposphere, and low to high latitudes. Remaining questions/issues and recommendations were provided for future research. Hide

The spatial structure of the solar cycle signals on the Earth's surface is analysed to identify the mechanisms. Both tropical and extratropical solar surface signals can result from circulation changes in the upper stratosphere through (i) a downward migration of wave zonal mean flow interactions and (ii) changes in the stratospheric mean meridional circulation. Amplification of the solar signal also occurs through interaction with the ocean. Hide

We develop a novel two-dimensional space to probe the molecular composition of atmospheric organic aerosols. Hide

The aerosol is modelled during the summer 2013 with the WRF and CHIMERE models and over a large area encompassing Africa, Mediterranean sea and west Europe. The modelled aerosol is compared to available measurements such as the AERONET and EMEP networks. The model ability to estimate the aerosol speciation and size distribution is quantified. Hide

Uncertainties in both climate forcing and sensitivity limit the extent to which climate projections can meet society's needs for actionable climate science. Advances in observing and modeling atmospheric vertical velocities provide a potential breakthrough in understanding climate forcing and sensitivity, with concurrent reductions in uncertainty. Hide

Using an online coupled system of a regional climate model and chemistry transport model we investigated the radiative/climate impact of short-lived pollutants directly emitted by urban areas and those secondarily formed, focusing on the area of central Europe. We found that the direct/indirect effects of aerosols dominate, causing small but statistically significant cooling in summer and winter (up to −0.04 K). The radiative impact of ozone changes remains negligible. Hide

We present 10 years of bromine monoxide (BrO) satellite observations by the Ozone Monitoring Instrument (OMI) over the Rann of Kutch salt marsh. The measurements reveal a typical seasonal cycle of BrO with maximum concentrations during April/May. The results indicate that the Rann of Kutch is probably one of the strongest natural point sources of reactive bromine compounds outside the polar regions and is thought to have a significant impact on local and regional ozone chemistry. Hide

Chemical oxidation in the atmosphere removes pollutants and greenhouse gases but generates undesirable products such as secondary organic aerosol. Radicals are key intermediates in oxidation, but how they interact with aerosols is still not well understood. Here we use a laser to measure the loss of radicals onto oxidised aerosols generated in a smog chamber. The loss of radicals was controlled by the thickness or viscosity of the aerosols, confirmed by using sugar aerosols of known thickness. Hide

Since populated valleys suffer often from poor air quality, it is of interest to better understand the various mechanisms relevant to remove pollutants from the valley atmosphere. One mechanism is the transport by along-slope flows, which are generated during fair-weather days. In this study we quantify the amount of tracer that is removed from a valley atmosphere and the amount that is re-circulated within the valleys. For this study we are using the numerical weather model WRF. Hide

Water vapour in the stratosphere plays an important role in atmospheric chemistry and the Earth's radiative balance. We have analysed trends in stratospheric water vapour through the 21st century as simulated by a coupled chemistry–climate model following a range of greenhouse gas emission scenarios. We have also quantified the contribution that methane oxidation in the stratosphere makes to projected water vapour trends. Hide

Multi-model comparison of four offline dispersion models driven by the global climate projection climate show that the major driver for the sea salt flux changes will be the seawater temperature, but there are substantial differences between the model predictions. The impact on regional radiative budget due to sea spray is considerable in the Mediterranean area, due to warmer temperatures and longer days during the winter. Hide

We have quantified environmentally persistent free radicals and reactive oxygen species (ROS) in size-segregated atmospheric aerosol particles. We suggest that ROS were formed by decomposition of secondary organic aerosols interacting with transition metal ions and quinones contained in humic-like substances. The results have significant implications for aqueous-phase and cloud processing of organic aerosols as well as adverse health effects upon respiratory deposition of aerosol particles. Hide

Methane is the second most important greenhouse gas and a target of new emissions regulations in the United States. Despite its importance, its emissions are poorly understood. In this study, we used a remote sensing instrument located on Mount Wilson to estimate the monthly and annual methane emissions from Los Angeles. Derived methane emissions from Los Angeles showed consistent peaks in late summer/early fall and winter during the study period from 2011 to 2015. Hide

The current study provides the first quantitative budget analysis of radiocesium re-suspended from ground surface contaminated by the Fukushima nuclear accident. It provides useful information to society since our simulation can be used for the long-term assessment of internal exposure to residents in Japan. It also discussed that the re-suspension from forest ecosystems could be a dominant source of suspended radiocesium in the warm season in Japan. Hide

The amplified Arctic warming has seen a rapid decline in sea ice with serious implications for global climate. The loss of heat from the ocean to the atmosphere is considered important for the recovery of the diminishing sea ice. Yet there is little observational evidence regarding the efficiency of this process. In our study, we explore and quantify the ability of the open ocean to lose heat through sensible heat fluxes. It is found to depend on the prevailing cloud and wind regime. Hide

About 66 million years ago, a large fraction of the planet's species, including the non-avian dinosaurs, vanished when an asteroid hit the Yucatan Peninsula, likely triggering the largest short-term climate change in geologic history. Yet there have been no modern simulations of this climate change. We outline the initial conditions needed for such global climate simulations. There is much unknown about the aftermath of the impact. We discuss uncertainties and suggest new observations. Hide

An Aerodyne high-resolution time-of-flight AMS was deployed at a suburban site in the Sichuan Basin, southwestern China, under high emission intensity, and unique geographical and adverse meteorological conditions. OA was the most abundant component (36 %) in PM₁, characterized by a relatively high oxidation state. The contributions of BBOA and BC to PM₁ were high in primary emission episodes, highlighting the critical influence of biomass burning. Hide

We use trace gas measurements (N₂O₅, ClNO₂, NO₃) and particle properties (surface area, nitrate content etc.) to derive uptake coefficients (the probability of removal from the gas-phase on a per-collision basis) for the interaction of N₂O₅ with ambient aerosol and also the efficiency of formation of ClNO₂. The uptake coefficients show high variability but are reasonably well captured by parameterisations based on laboratory measurements. Hide

Real-time measurements of OA aging and SOA formation from logwood combustion were conducted under dark and UV oxidation. Substantial SOA formation was observed in all experiments, leading to twice the initial OA mass emphasizing the importance of the burning conditions for the aging processes. The results prove that emissions are subject to intensive chemical processing in the atmosphere; e.g. the most of the POA was found to become oxidized after the ozone addition, forming aged POA. Hide

Measurements of size-resolved aerosols (0.25–18 μm) were conducted at three sites (urban, suburban and background sites) in southern China during monsoon season (May–June) in 2010 aqueous-phase reaction was the main formation pathway of droplet mode sulfate. New particle formation, chemical aging, and long-range transport from upwind urban or biomass burning regions were also found to be important in at least some of the sights on some of the sampling days. Hide

We developed proxies for estimating the concentrations of monoterpenes and their oxidation products at a boreal forest site in Hyytiälä, Finland. The proxies for the monoterpene concentration include temperature-controlled emissions, dilution and different oxidation processes. The proxies were observed to capture the seasonal and diurnal variation of the monoterpene concentration reasonably well. Our proxies can be used in the analysis of new particle formation and growth in boreal environments. Hide

The large-scale PBL climatology from sounding observations is still lacking in China. This work investigated the BLH characterization at diurnal, monthly and seasonal timescales throughout China, showing large geographic and meteorological dependences. BLH is, on average, negatively (positively) associated with the surface pressure and lower tropospheric stability (wind speed and temperature). Cloud tends to suppress the development of the PBL, which has implications for air quality forecasts. Hide

In the study, humic-like substances (HULIS) in smoke PM_2.5 emitted from the combustion of biomass materials and fossil fuels are studied. The results indicate that both biomass burning and coal combustion are important primary sources of atmospheric HULIS. Moreover, the primary HULIS and atmospheric HULIS are similar in many properties, but some distinct features are also apparent. These results are helpful to understand the contribution and chemical nature of HULIS in combustion emissions. Hide

An integrated analysis of all the ozone observations (lidar, sondes, and airborne in situ measurements) conducted during the 2008 IPY campaigns is performed and the processes that determine summer ozone concentrations over Greenland and Canada are discussed. Combined with a regional model simulation (WRFChem), the analysis of ozone, CO, and PV latitudinal and vertical variability allows the determination of the influence of stratospheric sources and biomass burning and anthropogenic emissions. Hide

A particle's surface is treated as a continuum of ice nucleation sites with a Gaussian distribution of freezing ability to predict particle-induced freezing of cloud droplets. This does not require prescribing the size or number of active sites. Analysis of droplet freezing spectra revealed a critical total surface area threshold, above which the variability of active site ability saturates. Below this threshold an apparently higher ice active site density (n_s) is retrieved for the same system. Hide