We present several changes to the setup of long-path differential optical absorption spectroscopy (LP-DOAS) instruments, including the application of a laser-driven light source, a modified coupling of the measurement signal between components, improved stray-light suppression, and better signal homogenization measures. These changes reduce detection limits of typical trace-gas species by a factor of 3–4 compared to previous setups and enable automated long-term observations in Antarctica.

A novel imaging-DOAS instrument (IMPACT) is presented for measurements of nitrogen dioxide (NO₂) in the atmosphere. The instrument combines full-azimuthal pointing (360°) with a large vertical coverage (40°). Complete panoramic scans and vertical NO₂ profiles around the measurement site are acquired at a temporal resolution of 15 min. In addition, information about the aerosol phase function is retrieved from O₄ slant columns along multiple almucantar scans measured simultaneously by IMPACT.

Atmospheric measurements on rising balloons can be compromised by the balloon's wake. The aim of this study is to provide a tool for assessing the likelihood of encountering the balloon's wake at the position of the gondola. This includes an uncertainty analysis of the calculation and a retrieval of vertical winds. We find an average wake encounter probability of 28 % for a standard radiosonde. Additionally, we evaluate the influence of wake from smaller objects on turbulence measurements.

Low-cost air quality sensors are enabling people to collect data to better understand their local environment and potential exposures. However, there is some concern regarding how reliable the calibrations of these sensors are in new and different environments. To explore this issue, our team colocated sensors at three different sites with high-quality monitoring instruments to compare to. We explored the transferability of calibration models as well as approaches to improve reliability.

How cirroform clouds affect the radiation balance of the atmosphere depends on their properties, including ice particle types such as crystals, pellets, and fragments. Ice halos form if ice particles in these clouds are in a smooth hexagonal crystalline form. This paper introduces a method to search long-term records of sky images for ice halos, as gathered by total sky imagers (TSIs). Such an analysis will allow one to explore geographical and seasonal variations in cirrus cloud particle types.

In this paper, we present a comparative analysis of the use of lidar-backscattered signals at three wavelengths (355, 532 and 1064 nm) to study the ABL by investigating high-order moments, which gives us information about the ABL height (derived using the variance method), aerosol layer movements (skewness) and mixing conditions (kurtosis) at several heights.

Aerosol–cloud interactions contribute the greatest uncertainty to cloud formation. Aerosol composition is complex and can change quickly in the atmosphere. In this work, we recreate a transition in aerosol mixing state in the laboratory, which (to date) has only been observed in the ambient state. We then report the subsequent changes on cloud condensation nuclei (CCN) activation.

Accuracy assessment of the satellite-retrieved aerosol properties is an important exercise to validate and track the changes in the retrieval algorithm. Here, for the first time, three standard aerosol products derived from MODIS Aqua are compared against the ground-based AERONET dataset over the North American region. The present validation analysis provides guidance in the development of inversion schemes to derive aerosol properties from existing and future MODIS-like sensors.

A comprehensive comparison of more than 70 000 synchronous 1 min aerosol optical depth (AOD) data from 3 Global Atmosphere Watch precision filter radiometers (GAW-PFR) and 15 Aerosol Robotic Network Cimel radiometers (AERONET-Cimel) was performed for the four near wavelengths (380, 440, 500 and 870 nm) in the period 2005–2015. The goal of this study is to assess whether their long term AOD data are comparable and consistent.

Raman spectra and soot primary particle size change with the impactor sampling stage even though the soot source is a steady laboratory flame. This is of potential interest to atmospheric researchers because past work on aerodynamically separated samples was interpreted in terms of distinct particle sources producing particles of different sizes and chemical structures.

The morphology and effective density of externally mixed black carbon (extBC) aerosols were studied using a tandem technique coupling a DMA with a SP2. The study extended the mass–mobility relationship to large extBC with a mobility diameter larger than 350 nm, a size range seldom included in previous tandem measurements of BC aggregates. On this basis, quantities such as the mass–mobility scaling exponent were revealed for extBC in urban Beijing.

A method is described to classify cloud mixtures of cloud top types, termed cloud scenes, using cloud type classification derived from the CloudSat radar. The scale dependence of the cloud scenes is quantified. The cloud scenes are used to assess the characteristics of spatially collocated Atmospheric Infrared Sounder (AIRS) thermodynamic-phase and ice cloud property retrievals within scenes of varying cloud type complexity.

This work discusses the most frequent methods for the harmonization of vertically resolved atmospheric state observations in a conceptually and terminologically aligned framework. Ten matching operations have been identified and expressed by common matrix algebra. The effect of these manipulations on the information content of the original data and on the uncertainty budget of data comparisons has been examined and discussed.

We present the emerging flux measurement method true eddy accumulation (TEA), able to quantify the land–atmosphere exchange of a large number of trace gases which are important for air quality and atmospheric composition. Our innovative implementation provides proof of concept of TEA and compared well to the established reference, outperforming previous works on TEA. Key to the success was the innovative high-speed air sampling and fully digital real-time data processing system.

Today, few lidar are capable of triple-wavelength particle linear depolarization ratio (PLDR) measurements. This study is the first systematic investigation of the effect of different choices of PLDR input on the inversion of lidar measurements of mineral dust and dusty mixtures using light scattering by randomly oriented spheroids. We provide recommendations of the most suitable input parameters for use with the applied methodology, based on a relational assessment of the inversion output.

Incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) has been proven to be a reliable method for measuring glyoxal and methylglyoxal in the atmosphere. However, the commonly overlying strong spectral absorption of nitrogen dioxide hampers the accurate and sensitive resolve of the weak absorption features of glyoxal and methylglyoxal. Here, we report a custom-built IBBCEAS system that could overcome this problem by quantitatively removing nitrogen dioxide from the sample air.

A new method was developed to identify persistent temperature inversion events in a subalpine basin using a radon-based method (RBM). By comparing with an existing pseudo-vertical temperature gradient method, the RBM was shown to be more reliable and seasonally independent. The RBM has the potential to increase the understanding of meteorological controls on air pollution episodes in complex terrain beyond the capability of contemporary atmospheric stability classification tools.

We present a method for identifying individual exhaust plumes of air pollution emitted from shipping, by linking these to specific ships using identification information which all ships transmit. We also quantify the contribution of these plumes to local particle levels, which has relevance for health effects. Ships emit a lot of nanometre-sized particles, which proved to be a good indicator of plumes at a distance of about 10 km downwind of a shipping lane in the Baltic Sea.

Under the UK GAUGE project, two new greenhouse gas observation sites were established in the 2013/2014 winter at two telecommunications towers. A combination of spectroscopic and chromatographic instrumentation was used to measure CO₂, CH₄, CO, N₂O and SF₆. The advantages and disadvantages of two CRDS sample drying strategies, Nafion(R) and empirical water correction, were also examined.

We present the design and operation of a newly built continuous-flow reactor (CFR), which can be used as a tool to gain considerable insights into the composition and physical state of secondary organic aerosol (SOA). The CFR was used to generate large quantities of SOA mass, allowing the use of highly accurate techniques that are not usually accessible. We demonstrate how this unique approach can be used to investigate the relationship between SOA formation and physiochemical properties.

This study compared 10 years of carbonaceous aerosol measurements collected at Egbert by three North American long-term monitoring networks. The study evaluated how differences in sample collection and analysis affected the concentrations of total carbon (TC), organic carbon (OC), and elemental carbon (EC). Various carbonaceous fractions measured by the three networks were consistent and comparable over the period. Elevated OC and EC were observed when ambient temperature exceeded 10 °C.

The MOPITT (Measurements of Pollution in the Troposphere) satellite instrument has been making nearly continuous observations of atmospheric carbon monoxide (CO) since 2000. MOPITT CO retrievals are routinely used to analyze emissions from fossil fuels and biomass burning, as well as the atmospheric transport of those emissions. This paper describes recent enhancements to the MOPITT retrieval algorithm. New validation results illustrate clear improvements in the fidelity of the MOPITT product.

NASA Compact Airborne Formadehyde Experiment (CAFE) is a nonresonant laser-induced fluorescence instrument for airborne in situ measurement of formaldehyde (HCHO). The instrument is described here with highlighted improvements from the predecessor instrument, COmpact Formaldehyde FluorescencE Experiment (COFFEE).

In a cloud, different particles like liquid water droplets and ice particles can exist simultaneously. To study the evolution of cloud particles from cloud top to bottom one has to find out how many different types of particles with different fall velocities are present. This can be done by analyzing the number of peaks in upward-looking cloud radar Doppler spectra. A new machine-learning algorithm (named PEAKO) that determines the number of peaks is introduced and compared to existing methods.

Satellite-based aerosol optical depth (AOD) products have been improved continuously and available from multiple low Earth orbit sensors, such as MODIS, MISR, and VIIRS, and geostationary sensors, such as GOCI and AHI, over East Asia. These multi-satellite AOD products are validated, intercompared, analyzed, and integrated to understand different characteristics, such as quality and spatio-temporal coverage, focused on several aerosol transportation cases during the 2016 KORUS-AQ campaign.

This study validates the performance of a personal air quality monitor that integrates miniaturised sensors that measure physical and chemical parameters. Overall, the air pollution sensors showed excellent agreement with standard instrumentation in outdoor, indoor and commuting environments across seasons and different geographical settings. Hence, novel sensing technologies like the ones demonstrated here can revolutionise health studies by providing highly resolved reliable exposure metrics.