For volatile organic compound (VOC) observations, zero gases free of VOC traces are essential for the characterisation of the measurement devices and procedures, for instrument operation as well as for calibrations. Three gas purifiers were tested for their removal efficiency of VOCs following a standardised procedure. Results show that not all purification methods removed VOCs from the zero gas and that a gas purifier needs to be tested before its intended application in the field.

Satellite-measured radiance from an Earth scene comprises light scattered and absorbed by gases, clouds and aerosols in the atmosphere and by the Earth surface. To retrieve aerosol information, the signal from clouds, gases and the surface must be separated from the aerosol signal. This paper highlights the gas absorption correction method used by the MODIS dark-target aerosol retrieval algorithm and demonstrates that aerosol retrieval accuracy depends on accurate gas absorption correction.

Snow, frost formation and ice cubes in our drinks are part of our daily life. But what about our technical innovations like aviation, electrical power transmission and wind-energy production, can they cope with icing? Icing Wind Tunnels are an ideal laboratory environment to answer that question. In this paper, we show how the icing wind tunnel in Braunschweig (Germany) was built and how we can use it for engineering and climate research.

Chemical ionization mass spectrometry has emerged as a versatile tool for the study of reactive gases. Robust calibration is required to assess the sensitivity of these instruments and their dependence on external factors such as specific humidity. Here, we report the sensitivity of benzene cluster cation chemical ionization for an array of terpene compounds. This work permits a more universal understanding of the sensitivity of this technique to a host of isobaric compounds.

An approach to estimate the height of aerosol plumes over land from satellite measurements of the oxygen A band is proposed. The method, termed dynamic scaling, forces the retrieval to use spectral points that contain more height information. The method is tested in a synthetic environment as well as with GOME-2A and GOME-2B measurements of wildfire plumes over Europe, with very encouraging results. This method can be easily applied to other aerosol height algorithms using least squares.

This paper presents an innovative retrieval method that translates the CALIOP land surface laser pulse returns into the surface bidirectional reflectance. The surface bidirectional reflectances retrieved from CALIOP measurements contribute complementary data for existing MODIS standard data products and could be used to detect and monitor seasonal surface reflectance changes in high latitude regions where passive MODIS measurements are limited.

This work reports airborne wind lidar observations performed in a recent field campaign. The deployed lidar system serves as a demonstrator for the satellite instrument ALADIN on board Aeolus, which is scheduled for launch in 2018 and will become the first wind lidar in space. After presenting the measurement principle, operation procedures and wind retrieval algorithm, the obtained wind results are validated and discussed, providing valuable information in preparation for the satellite mission.

The Brewer spectrophotometer has been used for decades as reference instrument to retrieve total ozone column (TOC) and for validation of satellite based measurements. This spectrophotometer has a thermal sensitivity already known, which is usually characterized using two different retrieval procedures. In this work, we report on a comparative study of the temperature coefficients retrieval procedures, obtaining differences less that 0.08 % in TOC when using any of the procedures.

A new data set of vertical column densities of the water vapour isotopologues H₂O and HDO retrieved from short-wave infrared measurements (2339 nm to 2383 nm) by the SCIAMACHY satellite instrument for the whole of the mission period from 2003 to 2012 is presented. The data are validated against ground-based Fourier transform infrared measurements. High-altitude stations observe different air columns; thus in this case collocated scenes with clouds around station height are needed for agreement.

We present new primary calibration scales for five halogenated greenhouse gases. The preparation method, newly applied to halocarbons, is dynamic and gravimetric and allows the generation of reference gas mixtures at near-ambient levels (pmol mol⁻¹). Each prepared molar fraction is traceable to the realisation of SI units (International System of Units) and is assigned an uncertainty estimate following international guidelines.

This paper presents a new cloud detection and classification framework, CC4CL. It applies a sophisticated optimal estimation method to derive cloud variables from satellite data of various polar-orbiting platforms and sensors (AVHRR, MODIS, AATSR). CC4CL provides explicit uncertainty quantification and long-term consistency for decadal timeseries at various spatial resolutions. We analysed 5 case studies to show that cloud height estimates are very realistic unless optically thin clouds overlap.

Satellites are vital for measuring cloud properties necessary for climate prediction studies. We present a method to retrieve cloud properties from satellite based radiometric measurements. The methodology employed is known as optimal estimation and belongs in the class of statistical inversion methods based on Bayes' theorem. We show, through theoretical retrieval simulations, that the solution is stable and accurate to within 10–20% depending on cloud thickness.

This paper compares aerosol extinction records from two limb scattering instruments, OSIRIS and SCIAMACHY, to that from the occultation instrument SAGE II. Differences are investigated through modelling and retrieval studies and important sources of systematic errors are quantified. It is found that the largest biases come from uncertainties in the aerosol size distribution and the aerosol particle concentration at altitudes above 30 km.

This research was conducted to determine the impact of multiple a priori ozone (O₃) profile products on Tropospheric Emissions: Monitoring of Pollution (TEMPO) satellite retrievals. It was determined that non-climatological model predictions, in particular those from a chemical transport model, when applied as the a priori profile improved the accuracy of TEMPO tropospheric O₃ retrievals in comparison to the TB-Clim product that is currently suggested for use in the TEMPO retrieval algorithm.

We have adopted a new technique for measuring glass-forming properties of atmospherically relevant organic aerosols at submicron sizes and relatively low mass concentrations. Aerosol particles are deposited in the form of a thin film with interdigitated electrodes using electrostatic precipitation. Broadband dielectric spectroscopy is used to measure the kinetically controlled glass transition temperatures of glycerol and citric acid aerosols with three atmospheric relevant cooling rates.

We describe the operating principle, design and performance of the Nucleation Mode Aerosol Size Spectrometer (NMASS), an instrument composed of 5 condensation particle counters measuring size selected particle concentrations between 3 and 60 nm. An inversion to recover size distributions from the data is evaluated. Calibrations of a 2-NMASS system for measuring size distributions on the NASA Atmospheric Tomography Mission, and examples of its in-flight performance are presented.

This paper analyzed the collocated GPS radio occultation profiles near the convective systems identified from ISCCP over two orographic regions of the Alps and Andes. Gravity wave (GW) analysis over both selected regions was also carried out. The gravity wave signature from the two case studies were investigated using mesoscale WRF simulations, ERA-Interim reanalysis data, and measured RO temperature profiles. The absence of fronts or jets during both case studies reveals similar relevant GWs.

Measuring the chemical composition of airborne particulates can provide valuable information on the concentration of regulated toxic metals and their sources and assist in the identification and validation of abatement techniques. Undertaking these measurements at a high time resolution enables computer modelling techniques to be more robustly linked to emission processes. This study describes a comprehensive laboratory and field evaluation of a high time resolution metal monitoring instrument.

Ultra-fast response engine exhaust emissions analyzers have been adapted for on-board vehicle use combined with GPS data. We present, for the first time, how high spatio-temporal resolution data products allow transient features associated with internal combustion engines to be examined in detail during on-road driving, revealing the detailed causes behind emissions hot spots. In particular, NOx pollution was assessed in detail for a number of road network features (e.g. speed bumps).

Low-cost air quality sensors and air quality sensor systems have the potential to open up new ways of measuring pollutants. In this paper, we explored ways to use low-cost sensors (approximately USD 10 per sensor) to estimate methane – a pollutant important for its contributions to climate change. We found that while these sensors will likely never replace traditional air quality monitoring methods, they can provide useful supplementary information on local pollution sources and regional trends.

In this work, we introduce a Monte Carlo uncertainty analysis that takes into account possible systematic spectral deviations in the atmospheric full spectrum ozone retrieval method. Accounting for possible systematic spectral deviations in the spectral data is important since they produce larger total ozone column uncertainties than uncorrelated noise-like variations that traditional uncertainty estimations predict.

Version 6 of the Nimbus 7 LIMS stratospheric data set contains improved profiles of NO₂. The variations of V6 HNO₃ and NO₂ at 31.6 hPa are reassessed for their consistency in the region of the Aleutian High (AH) from 14 to 28 January 1979. Photochemical model calculations initialized with the V6 data and including effects of heterogeneous reactions mimic the observed decreases of NO₂ and increases in HNO₃ over a period of 10 days along trajectories terminating in the AH region on 28 January.

Simulations of total and polarized cloud reflectance angular signatures such as the ones measured by the multi-angular and polarized radiometer POLDER3/PARASOL are used to evaluate cloud heterogeneity effects on cloud parameter retrievals. Effects on optical thickness, albedo of the cloudy scenes, effective radius and variance of the cloud droplet size distribution, cloud top pressure and aerosol above cloud are analyzed.

Laboratory and in-flight evaluations of uncertainties of measurements from a cloud droplet probe are presented. This study extends results of earlier studies by examining instrument response over a greater range of droplet sizes throughout the entire sample volume. Errors in droplet sizing based on the laboratory measurements tend to be less than 10 %, significantly less than typically quoted sizing accuracy for this class of instrument.

The electrochemical concentration cell ozonesonde is a balloon-borne instrument that measures ozone to an altitude of ~30 km. This work summarizes the National Oceanic and Atmospheric Administration's 50+ year, eight-site ozonesonde network history, the processing techniques utilized to account for instrumental changes, and the uncertainty of the measurement. The ozonesonde measurements were compared to satellite measurements and agreed well. This important data set is more useful and robust.

Prior satellite comparisons of bispectral and polarimetric cloud droplet size retrievals exhibited systematic biases. However, similar airborne instrument retrievals have been found to be quite similar to one another. This study explains this discrepancy in terms of differing sensitivity to vertical profile, as well as spatial and angular resolution. This is accomplished by using a satellite retrieval simulator – an LES cloud model coupled to radiative transfer and cloud retrieval algorithms.

Low cost sensors for monitoring atmospheric pollution are growing in popularity worldwide. Nonetheless, the expectations from these devices were seldom met, thus urging for more research. This study focuses on sensor performance within the realistic framework of an initial calibration next to a reference instrument and the subsequent distant deployment. Within this framework, we assessed the uncertainty of these sensors and their suitability to map intra-urban gradients of NO/NO₂.

The need for in situ nitrogen oxide measurements on a global scale is crucial to improve the chemistry in global chemistry models and evaluate satellite retrievals. Here we present the characterization of the new IAGOS NO_x instrument installed on passenger aircraft, which will provide statistical robust measurements from the surface up to 13 km.

We present the wavelength calibration of the travelling reference Brewer spectrometer of the Regional Brewer Calibration Center for Europe at PTB in Braunschweig. We compare these results to those of the standard procedure for the wavelength calibration of the Brewer. The results of the laser-based calibrations reproduce those obtained by the standard operational methodology and show that there is a underestimation of 0.8 %, due the use of the parametrized slit functions.

This work, performed at the Royal Belgian Institute for Space Aeronomy and the second in a series of four Ozone_cci papers, reports for the first time on data content studies, information content studies, and comparisons with co-located ground-based reference observations for all 13 nadir ozone profile data products that are part of the Climate Research Data Package (CRDP) on atmospheric ozone of the European Space Agency's Climate Change Initiative.

Wind turbines extract energy from the flow which manifests in a region of lower wind speeds and increased turbulence downstream of the rotor, the so-called wake. Understanding the characteristics of the wake is a key challenge for wind-energy research. A new strategy for measuring the wind in the wake with three synchronized lidar instruments is presented. The measurement points are automatically adapted to the prevailing wind direction to achieve continuous monitoring of wake properties.

Atmospheric methane abundances as function of altitude derived from the thermal infrared band of the Japanese GOSAT satellite show a systematic bias. It has been shown that simple correction schemes can lead to undesired consequences. This paper discusses a more elaborate approach, resulting in methane profiles that fall within 2 % of independent reference measurements and models. This is true for different scenes around the globe and over the full altitude range.

Aircraft-based laser remote sensing measurements of atmospheric aerosol and ozone were conducted to study air pollution from the oil sands extraction industry in northern Alberta. The ozone mixing ratio measured in the polluted boundary layer air was equal to or less than the background ozone mixing ratio. The lidar measurements detected a layer of forest fire smoke above the surface boundary layer in which the measured ozone mixing ratio was substantially greater than the background amount.

A new technique to estimate vertical velocities from Parsivel-measured drop and velocity spectra is developed. The estimated vertical velocities (w) were compared with w components of winds measured from the anemometer at the same site. They showed good agreement with each other, suggesting that this technique is reliable and applicable to rainfall studies. With these w values, rainfall characteristics related to up-/downdraft were investigated on the windward and leeward sides of a mountain.