We examine the utility of tree ring ¹⁴C archives for detecting long-term changes in fossil CO₂ emissions from a point source using six years of observations from two trees near the Kapuni Gas Treatment Plant in New Zealand. Pairing these observations with an atmospheric transport model, we quantify the minimum amount of change in annual emissions that it would be possible to detect in new samples representing averages over one, two, and four years.

This paper presents a comprehensive summary of roadside measurements using a mobile laboratory, equipped with state-of-the-art instrumentation. Pollution gradients were observed for particle number, black carbon, organics, some metals, and gases at four different highway environments. Flow dynamics appeared to be an important factor, however, at the most open site, condensation of semi-volatile organics was observed. The fleet average NO₂ emission factor increased over the last decade.

In early spring the Baltic region is frequently affected by high pollution events due to biomass burning in that area. Here we present a comprehensive study to investigate the impact of biomass/grass burning (BB) on the evolution and composition of aerosol in Preila, Lithuania, during springtime open fires.

In this study, we mixed a pure mineral dust sample with ice active biological material and quantified the immersion freezing behavior of the resulting particles utilizing the Leipzig Aerosol Cloud Interaction Simulator (LACIS). Furthermore, we used different methods to investigate the mixing state of our generated aerosol. We found that internally mixed particles, containing ice active biological material, follow the ice nucleation behavior observed for the pure biological particles.

Single-particle measurements from a soot-particle aerosol mass spectrometer were performed to examine the mixing state of aerosol particles in an air mass influenced by aged biomass burning. Our observations indicate non-uniform mixing of particles within a biomass burning plume in terms of molecular weight and potassium content, and illustrate that high molecular weight organic compounds can be a key contributor to low-volatility BrC observed in biomass burning organic aerosols.

The response of the Weather Research and Forecasting model with Chemistry to forcings by biomass burning aerosol were investigated in high-resolution nested domains over Brazil. The aerosol-layer was found to have a negative direct effect at the top of the atmosphere, but this was largely cancelled by a semi-direct effect which inhibited afternoon cloud formation. The cloud response to the aerosol was found to be highly sensitive to model resolution and the use of convective parameterisation.

Here we report on a detailed study of the photochemistry and fate of a nitrooxy enal that is produced from the reaction of NO₃ with isoprene. We synthesized the 4,1-nitrooxy enal, purified it, and measured the O₃ and OH reaction rate constants, and determined the atmospheric photodissociation rate constant for specified radiation conditions. The determined fast photolysis rate and high reactivity toward OH lead to a lifetime of less than 1 hour, with photolysis being a dominant daytime sink.

Gravity-wave-induced oscillations have been characterized over Kolhapur (16.8°N and 74.2°E), India, using the adiabatic variations in OH airglow intensity and temperature data. The results show that there exist large deviations from one investigation to the other. We also use a full-wave model to simulate the response of OH emission to the wave motion and compare the results with observed values. This report discusses the observed wave characteristics and cause of the noted difference.

This study evaluates the distribution and variation of carbon monoxide (CO) in the upper troposphere and lower stratosphere (UTLS) during 2004–2012 on global and regional scales as simulated by two chemical transport models (GMI and GEOS-Chem), using the latest version (V4) of Aura Microwave Limb Sounder (MLS) observations. The impacts of surface emissions and convection on CO concentrations in the UTLS over different regions are investigated, using both model simulations and MLS observations.

We present a dual tracer atmospheric inversion technique to separately estimate biospheric and fossil fuel CO₂ fluxes from atmospheric measurements of CO₂ and ¹⁴CO₂. In addition to estimating monthly regional fossil fuel fluxes of CO₂, this system can also reduce biases in biospheric fluxes that arise in a traditional CO₂ inversion from prescribing a fixed but inaccurate fossil fuel flux.

Wildfires are generally expected to increase in frequency and severity due to climate change. For Europe this could mean increased air pollution levels during the summer. Until 2050, predicted changes are moderate, but under a scenario of strong climate change, these may increase considerably during the later part of the current century. In Portugal and several parts of the Mediterranean, emissions may become relevant for meeting WHO concentration targets.

The ESA-funded SACS-2 and SMASH projects developed and improved dedicated satellite-derived ash plume and sulfur dioxide level assessments. These estimates were validated using ground-based and aircraft lidar measurements. The validation results are promising for most satellite products and are within the estimated uncertainties of each of the comparative data sets. The IASI data show a better consistency concerning the ash optical depth and ash layer height.

In this paper, we assess how daily ozone measurements from the Infrared Atmospheric Sounding Interferometer (IASI/MetOp) can contribute to the analyses of the processes driving O₃ variability in the troposphere and the stratosphere with a set of parameterized geophysical variables, and we demonstrate the added value of IASI exceptional frequency sampling for monitoring medium- to long-term changes in global ozone concentrations in the future.

Coastal seas are sources of methane in the atmosphere and can fluctuate from emitting to absorbing carbon dioxide. Direct air–sea transport measurements of these two greenhouse gases in near shore regions remain scarce. From a recently established coastal atmospheric station on the south-west coast of the UK, we observed that the oceanic absorption of carbon dioxide peaked during the phytoplankton bloom, while methane emission varied with the tidal cycle, likely due to an estuary influence.

The study presents a comprehensive tool for accurate calculation of solar flux as part of a novel algorithm GRASP (Generalized Retrieval of Aerosol and Surface Properties). We show that simplification of details in directional properties of atmospheric aerosol scattering and reflectance of underlying surface causes systematic biases in evaluation of aerosol radiative effect. Presented application for satellite data is one more step in the measurement-based estimate of aerosol effect on climate.

This is the first study looking at the amount of aerosols above cloud to see whether the amount is greater or less than in nearby clear skies at the same heights. We find that the aerosol amount over cloud differs a lot from that in nearby clear skies over some areas. These results give an indication, for the first time, that clouds might affect the amount of overlying aerosols.

In this study, we present observational evidence to show that two distinct types of cirrus clouds exist – in situ origin and liquid origin cirrus. These two types differ by their formation mechanism and other properties. Airborne, in-cloud measurements of cloud ice water content (IWC), ice crystal concentration (Nice), and ice crystal size from the 2014 ML-CIRRUS campaign provide cloud samples that have been divided and analyzed according to their origin type.

Observed and projected trends in large-scale wind speed over the oceans prompt the question: how do marine clouds respond to changes in wind speed? This work presents an investigation of the dynamical response of marine low clouds to different wind speeds over 1 day.

We examine the impact of buildings on surface solar fluxes in Beijing by accounting for their 3-D structures. We find that inclusion of buildings changes surface solar fluxes by within ±1 W m⁻², ±1–10 W m⁻², and up to ±100 W m⁻² at grid resolutions of 4 km, 800 m, and 90 m, respectively. We can resolve pairs of positive-negative flux deviations on different sides of buildings at ≤ 800 m resolutions. We should treat building-effect on solar fluxes differently in models with different resolutions.

Two global models were used to investigate the impact of galactic cosmic ray (GCRs) on the atmosphere over the 1960-2010 time period. The primary impact of the naturally occurring GCRs on ozone was found to be due to their production of NO_x and this impact varies with the atmospheric chlorine loading, sulfate aerosol loading, and solar cycle variation. GCR-caused decreases of annual average global total ozone were computed to be 0.2 % or less.

In chemical transport models, NO_x emitted by lightning (LNO_x) is instantaneously diluted into the grid. A plume-in-grid parameterization to account for the sub-grid chemistry of LNO_x is presented. This approach was implemented into the GEOS-Chem model and leads to a relative increase of NO_x and O₃ (18 % and 2 %, respectively, in July) on a large scale downwind of lightning emissions and a relative decrease (25 % and 8 %, respectively, over central Africa in July) over the regions of emissions.

With a new 4-year satellite-based data set, the cloud-free marine boundary layer (MBL) structure characteristics over the eastern Pacific region were presented and analyzed together with the stratiform cloud top as the cloudy MBL top. Results showed that the behavior of MBL decouple structure and drizzling and non-drizzling stratiform cloud tops was mainly controlled by the inversion near the MBL top. Results in this paper will be valuable to evaluate and improve model simulation.

The direct shortwave (SW) radiative effect of aerosols under clear-sky conditions in the ALADIN-HIRLAM numerical weather prediction system was investigated using three SW radiation schemes in diagnostic single-column experiments. Each scheme accurately simulates the direct SW effect when observed aerosols are used, particularly for heavy pollution scenarios.

This paper documents a new package for the Weather Research and Forecasting--Advanced Research WRF (WRF-ARW) model that can simulate any partial, total or hybrid solar eclipse for the period 1950–2050 and is also extensible to a longer period. First, a description of the implementation together with a validation for the period 1950–2050 of all solar eclipse trajectories is presented. Second, the model response is analyzed in four total solar eclipse episodes. Global horizontal irradiance (GHI) outcomes are validated with respect to ground-based measurements.

We use new airborne and ground-based observations from two summer 2013 campaigns in the southeastern US, interpreted with a chemical transport model, to understand the impact of isoprene and monoterpene chemistry on the atmospheric NO_x budget via production of organic nitrates (RONO₂). We find that a diversity of species contribute to observed RONO₂. Our work implies that the NO_x sink to RONO₂ production is only sensitive to NO_x emissions in regions where they are already low.

The secondary organic aerosol (SOA) produced by the photooxidation of isoprene with and without inorganic seed is simulated using the Unified Partitioning Aerosol Phase Reaction (UNIPAR) model, assuming a single homogenously mixed organic–inorganic phase. UNIPAR is used to determine the sensitivity of isoprene SOA formation to NO_x, aerosol acidity and aerosol liquid water content. Isoprene SOA is found to be most sensitive to aerosol acidity but dynamically related to all three parameters.