We compare two different data assimilation systems for estimating sources and sinks of CO_2 from concentration measurements. The systems are CarbonTracker and TM5-4DVar, which have both been used in a number of scientific studies. We analyze the differences between both models as well as the sensitivity of the estimated sources and sinks to the observation coverage. The results provide a lower limit for the uncertainty of surface carbon fluxes with the current measurement network. Hide

We present 5-year flask measurements (2007–2011) of greenhouse gases (GHGs) at three atmospheric stations in India. The results suggest significant sources of CO2, CH4, N2O, CO, and H2 over S and NE India, while SF6 sources are weak. The seasonal cycles for each species reflect the seasonality of sources/sinks and influences of the Indian monsoon circulations. The data show potential to infer regional patterns of GHG fluxes and atmospheric transport over this under-documented region. Hide

A merged data set of HALOE and MIPAS lower stratospheric water vapour has been constructed. Multivariate linear regression shows that the merged time series can best be explained if a proxy for the 11-year solar cycle is considered. The amplitude of the solar cycle signal in water vapour is slightly higher than that which can be explained by the known solar cycle variation of cold-point temperatures. Hide

The lower tropospheric ozone distribution maps were first obtained from the recent retrieval products of the Ozone Monitoring Instrument (OMI) onboard the Earth Observing System (EOS) Aura satellite. We found significant enhancement of ozone in the lower troposphere over central and eastern China (CEC), with Shandong Province as its center, and most notable in June in any given year. Similar seasonal variations were observed throughout the 9-year OMI measurement period of 2005 to 2013. Hide

Satellite data show that Indian summer monsoon (ISM) rainfall is closely associated with Middle East dust aerosols. Numerical modeling shows that the increased ISM rainfall is related to the enhanced southwesterly flow and moisture transport from the Arabian Sea to the Indian subcontinent, associated with the development of an anomalous low-pressure system over the Iranian Plateau and the Arabian Sea due to dust-induced atmospheric heating. Hide

The quasi 2-day wave (QTDW), one of the most striking features in the mesosphere/lower thermosphere, is analyzed using meteor radar measurements at Collm (51°N, 13°E) during 2004-2014. The QTDW has periods lasting between 43 and 52h during strong summer bursts, and weaker enhancements are found during winter. A correlation between QTDW amplitudes and wind shear suggests baroclinic instability to be a likely forcing mechanism. Hide

The ergodic theorem of stationary random processes is introduced to analyse and verify the ergodicity of atmospheric turbulence measured using the eddy-covariance technique with two sets of field observational data. The results show that the ergodicity of atmospheric turbulence in atmospheric boundary layer is relative not only to the atmospheric stratification but also to the eddy scale of atmospheric turbulence. Hide

Employing the well-established "Match" technique, we quantify polar stratospheric ozone loss during multiple Arctic and Antarctic winters, based on observations from the spaceborne Aura Microwave Limb Sounder (MLS) instrument. The dense MLS spatial coverage enables many more matches than is possible for balloon-based observations. Applying the same technique to MLS observations of the long-lived N2O molecule gives an measure of the impact of transport errors on our ozone loss estimates. Hide

Trends in the vertical distribution of ozone are reported for new and recently revised data sets. The amount of ozone-depleting compounds in the stratosphere peaked in the second half of the 1990s. We examine the trends before and after that peak to see if any change in trend is discernible. The previously reported decreases are confirmed. Furthermore, the downward trend in upper stratospheric ozone has not continued. The possible significance of any increase is discussed in detail. Hide

Technological shifts between fuel sources have had unexpected impacts on atmospheric composition and these significant changes can go undetected if source-specific monitoring infrastructure is not in place. We present chemically comprehensive, continuous measurements of organic compounds in a developed megacity (London), that show diesel-related hydrocarbons can dominate reactive carbon and ozone formation potential, highlighting a serious underestimation of this source in emission inventories. Hide

The ability of a coupled meteorology-chemistry model (WRF-CMAQ) to reproduce the historical trend in AOD and clear-sky SWR over the N. Hemisphere has been evaluated through a comparison of 21-year simulated results with observation-derived records from 1990 to 2010. Questions of how well the model represents the regional and temporal variability of aerosol burden and DRE, and whether the model is able to capture past trends in aerosol loading and associated radiation effects, will be addressed. Hide

In this study, the impact of O3 observations on the tropical cyclone (TC) structure is examined using the WRF-Chem with an ensemble-based data assimilation (DA) system. For a TC case that occurred over East Asia, the ensemble forecast is reasonable and the O3 assimilation affects both chemical and atmospheric variables near the TC area. All measures indicate a positive impact of DA on the analysis – the cost function and root mean square error have decreased by 16.9% and 8.87%, respectively. Hide

Based on simulated meteorology from 13 GCMs, we projected future wildfire activity in Alaskan and Canadian ecoregions by the mid-century. The most robust change is the increase of 150-390% in area burned over Alaska and western Canada. The models also predict an increase of 45-90% in the central and southern Canadian ecoregions, but a decrease of up to 50% in northern Canada. We further quantify how the changes in wildfire emissions may affect ozone concentrations in North America. Hide

We have measured atmospheric aerosol composition by using a Single Particle Soot Photometer (SP2) in the Finnish Arctic during winter 2011-2012. SP2 can give detailed information about mass distributions and mixing state of refractory black carbon (rBC). The measurements showed varying rBC mass concentrations, but relatively constant rBC core size distributions and mixing state parameters. On average, 24% of all particles contain rBC and the observed rBC cores are always thickly coated. Hide

A case study of the BLLAST experiment is considered to explore the decay of turbulence that occurs in the convective boundary layer over land during the afternoon. Based on observations and on a large-eddy simulation, the analysis reveals two phases in the afternoon: a first quasi-stationary phase when the turbulent kinetic energy slowly decays without significant change in the turbulence structure and a second phase of more rapid decay with a change in spectral turbulence characteristics. Hide

On 1 January 2015, the International Maritime Organisation tightened the regulations for sulfur content of shipping fuels in Sulfur Emission Control Areas. Here we present data from a station near Hamburg harbour in the North Sea SECA, which uses in situ measurements of atmospheric trace gases to deduce the sulphur fuel content of passing ships. We compare data from 2014 before the regulation change and from January 2015 and show how this method can be used for compliance monitoring. Hide

Historical land cover and land use change alone between 1980 and 2010 could lead to reduced summertime surface ozone by up to 4ppbv in East Asia. Climate change alone could lead to an increase in summertime ozone by 2-10ppbv in most of East Asia. Land cover change could offset part of the climate effect and lead to a previously unknown public health benefit. The sensitivity of surface ozone to land cover change is more dependent on dry deposition than isoprene emission in most of East Asia. Hide

Particles in the air of London have been assessed both by weight and by number. They have also been subject to chemical analysis. The data from 2 years of sampling have been used to investigate the sources contributing to the measured concentrations both in terms of the weight of the particles and the number of particles. Hide

For the first time, with S-shaped curves, the best available representation of time-varying emission factors of 12 heavy metals (Hg, As, Se, Pb, Cd, Cr, Ni, Sb, Mn, Co, Cu and Zn) from primary anthropogenic sources of China are determined on account of economic transitions and pollution control technology improvement. The temporal and spatial variation characteristics of these heavy metals emissions during the period of 1949−2012 are calculated and evaluated with uncertainty analysis. Hide

We conducted the first long-term real-time measurement of submicron aerosol composition in Beijing using an ACSM for 1 year. The seasonal variations of mass concentrations and chemical composition of submicron aerosol were investigated in detail, and the meteorological effects on aerosol chemistry, particularly temperature and relative humidity, were elucidated. Finally, the potential source areas of aerosol species during four seasons were identified. Hide

Based on summer measurements of δ18O and δD in the atmospheric vapour of a Mediterranean coastal wetland exposed to high evaporation, this paper explores the main drivers of isotopic signal variability. After having classified the data according to the main regional air mass trajectories, average diurnal cycles are discussed with regards to the contribution of local evaporation to the ground level atmospheric vapour. Hide

Aerosol particles undergo chemical modification during atmospheric transport due to reactions with trace gas species such as OH radicals affecting cloud formation and, thus, prediction of climate. Here, the cloud formation potential of surrogate biomass burning aerosol (BBA) is studied as a function of particle composition and OH exposure. We find that OH oxidation can alter the cloud formation potential of BBA, but its significance depends on the available water-soluble particulate material. Hide

In the present paper we report airborne measurements of new particle formation (NPF) above the Mediterranean Sea (HYMEX campaign). We show that NPF occurs over large areas above the sea, but the process is clearly promoted at high altitude, above 1000m, i.e. frequently in the free troposphere. NPF also seems to be mainly influenced by local processes occurring above the sea. After their formation, particles slowly grow at high altitude while not being greatly depleted or affected by coagulation. Hide

Aerosol size distribution measurements from three ground sites, two mobile laboratories, and one airplane are combined to investigate the spatial and temporal variability of ultrafine particles in and around Paris during the summer and winter MEGAPOLI campaigns. The role of nucleation as a particle source and the influence of Paris emissions on their surroundings are examined. Hide