In 2015, a CO₂/CH₄/CO CRDS was installed at Izaña station (Tenerife). We present the acceptance tests, the processing of raw data applied, the ambient measurements performed, and their comparison with other continuous in situ measurements. We determine linear relationships between flow rate, CRDS inlet pressure, and CRDS outlet valve aperture; a slight CO₂ correction that takes into account changes in the inlet pressure/flow rate and its origin; and the H₂O correction for CO in a novel way.

This paper presents the retrieval algorithm for the operational OMBRO data product and shows comparisons with correlative measurements and retrieval results. We highlight the physics of the retrieval. We compare the OMBRO products with other satellite and in situ measurements of BrO and illustrate the quality of the product on a global scale. We study OMBRO enhancements in volcanic plumes and over salt lakes. We also discuss the shortcomings and future updates of the OMBRO product.

This study describes aircraft measurements of methane from dairy farms in central California. A small deliberate release of a tracer gas is done on the ground and measured from the air and the ratio of methane to tracer used to quantify emissions. Farm-scale methane emissions are determined as well as the fraction of those emissions coming from animal activity versus liquid manure management. These findings were within the uncertainty of two established methods.

This paper presents a new application of the optimal estimation method (OEM) for the retrieval of ozone density profiles from DIAL measurements. The OEM results show excellent agreement with coincident ozonesonde measurements, with improved resolution over the traditional technique. The method also provides averaging kernels (facilitating comparison with other instruments), the vertical resolution of the retrieval, and a complete random and systematic uncertainty budget.

New systems to study the mesosphere are introduced. They result from the reengineering of previous systems, by making use of MIMO, spread-spectrum and compressed-sensing techniques that are widely used in telecommunications. The interferometer configuration is now implemented in transmission, making the location of meteor echoes possible with just one antenna on reception. Our novel concept makes the study of a mesosphere volume from different viewing points on the ground feasible and easy.

Are regional and seasonal averages from only a few satellite measurements, all aligned along a specific path, representative? Probably not. We present a method to adjust for the so-called sampling bias and investigate its influence on derived long-term trends. The method is illustrated and validated for a long-lived trace gas (carbonyl sulfide), and it is shown that the influence of the sampling bias is too small to change scientific conclusions on long-term trends.

This paper presents measurements of changes in mesospheric aerosol populations on different length scales, as detected by the DUSTY and MUDD probes on the MAXIDUSTY-1B rocket on 8 July 2016. Identical probes recorded very different currents, which we attribute to adverse flow effects. We find a general anti-correlation for charged aerosols and electrons, but not consistently on all length scales. We conclude that there is no simple relationship between aerosols and PMSE (radar echoes).

Multi-axis differential optical absorption spectroscopy (MAX-DOAS) is a widely used measurement technique for the detection of a variety of atmospheric trace gases. It enables the retrieval of aerosol and trace gas vertical profiles in the atmospheric boundary layer using appropriate retrieval algorithms. In this study, the ability of eight profile retrieval algorithms to reconstruct vertical profiles is assessed on the basis of synthetic measurements.

Vertical profiles of the particle backscattering coefficient at 355, 532 and 1064 nm measured by the Raman lidar system BASIL are compared with simulated particle backscatter profiles obtained through the application of a Mie scattering code and the use of simultaneous and co-located measurements by an optical particle counter on board the French research aircraft ATR42 operated by SAFIRE in the framework of the Hydrological Cycle in the Mediterranean Experiment – Special Observation Period 1.

We present 1 year of a new CALIOP-based aerosol extinction coefficient and lidar ratio over the ocean, with the goal of providing a flexible dataset for climate research as well as independent retrievals that can be helpful for refining CALIPSO Science Team algorithms. The retrievals are derived by constraining the lidar equation with an aerosol optical depth estimated from cross-calibrated CALIOP and CloudSat surface echos.

Based on single-particle mass spectra from field measurements in the upper Rhine valley, we identified characteristic particle classes and estimated their mass contributions without the need of a reference instrument in the field. Our study provides a good example for quantitative interpretation of single-particle data. Together with the complimentary results from bulk measurements, we have shown how a better understanding of the mixing state of ambient aerosol particles can be achieved.

We use a fuzzy k-means (FKM) classifier to assess the ability of the CALIPSO cloud–aerosol discrimination (CAD) algorithm to correctly distinguish between clouds and aerosols detected in the CALIPSO lidar backscatter signals. FKM is an unsupervised learning algorithm, so the classifications it derives are wholly independent from those reported by the CAD scheme. For a full month of measurements, the two techniques agree in ~ 95 % of all cases, providing strong evidence for CAD correctness.

We compare state-of-the-art models for predicting functional group composition in atmospheric particulate matter across urban and rural samples collected in a US monitoring network. While trends across models are consistent, absolute abundances can be sensitive to selection of calibration standards, spectral processing procedures, and calibration algorithms. Recommendations for further method development for reducing uncertainties are outlined.

The infrared spectra of atmospheric particles are rich in chemical information but require sophisticated statistical methods to extract information on account of their complex absorption profiles. We present an open software suite which makes current algorithms used for analysis of such spectra available to the community, with a browser-based interface for general users and modular architecture that facilitates addition of new methods by developers.

In this paper we take the first steps towards generating a multi-decadal record of the deuterium content of water vapor, useful for evaluating the moisture sources and processes affecting water vapor, by estimating the deuterium content from thermal IR radiances from the AIRS instrument. We find the AIRS-based measurements are sensitive to the deuterium content of water vapor in the middle and lower troposphere with a single measurement uncertainty of ~ 3 % and an accuracy of ~ 0.7 %.

NASA's Orbiting Carbon Observatory-3 (OCO-3) is scheduled for a 2019 launch to the International Space Station (ISS). It is expected to continue the record of column carbon dioxide (XCO₂) and solar-induced chlorophyll fluorescence (SIF) measurements from space used to study and constrain the Earth's carbon cycle. This work highlights the measurement objectives and uses simulated data to show that the expected instrument performance is on par with that of OCO-2.

Photoacoustic spectroscopy provides measurements of absorption coefficient for aerosol and gas samples but requires careful calibration, and researchers often use concentrations of ozone. Recent work has shown that the bath gas composition impacts the accuracy of this calibration at visible wavelengths. We explore further the role of bath gas, demonstrating that the calibration accuracy is optimal for a bath gas composed of 20 % oxygen and 80 % nitrogen at wavelengths of 405, 514 and 658 nm.

The paper details the design and characterization of a novel instrument for the measurement of particle reactivity and potential bioactivity, the PINQ. It continuously collects particles, regardless of size or composition, directly into a very small amount of liquid with a collection efficiency of > 0.97 and a cut-off size of 20 nm. PINQ has the highest time resolution, of only 1 min, and is very sensitive to various reactive species from the air.

The impact of aerosol particles on climate and air quality remains poorly understood due to multiple factors. One of the current limitations is the incomplete understanding of the contribution of oxygenated species, formed from the oxidation of volatile organic compounds (VOCs) to aerosol formation. Taking advantage of recent mass spectrometric developments, we have evaluated and compared the capability of multiple state-of-the-art mass spectrometers to detect a wide variety of oxygenated VOCs.

The aim of this study is the merging of stratospheric ozone profiles from three satellite data sets. The merged time series is used to compute long-term changes as a function of altitude, latitude and longitude to study the evolution of the ozone layer over 1985–2018. During the last 16 years we found positive trends in the upper stratosphere at mid latitudes, a large variability of the ozone changes as a function of longitude and a fluctuation in the tropical middle stratospheric trend.

This paper describes the measurement of atomic oxygen in the upper atmosphere onboard sounding rockets using solid electrolyte sensors. Calibration of the sensors in the laboratory is explained in detail. Results from the WADIS-2 rocket campaign show profiles of atomic oxygen density with a high spatial resolution.

Ozone is one of the most widely monitored trace gases in the atmosphere. It can be measured via its strong absorption bands in the ultraviolet (UV), visible (Vis) and infrared (IR) portions of the spectrum. Using multiple ground-based measurements and modeled data, this work provides a measurement-based evaluation of the impact of clouds on UV-visible total column ozone measurements in the high Arctic.

The FRESCO algorithm is a simple, fast and robust algorithm used to retrieve cloud information during operational satellite data processing. FRESCO retrieves effective cloud fraction and cloud pressure from measurements in the oxygen A band around 761 nm. In this paper, we propose a new version of the algorithm, called FRESCO-B, which is based on measurements in the oxygen B band around 687 nm. Such a method leads to more accurate retrievals for vegetated surfaces.

A home-built instrument of an incoherent broadband cavity-enhanced absorption spectrometer is reported for sensitive detection of CHOCHO and NO₂ in China's highly polluted environment. An NO₂ spectral profile measured using the same spectrometer is applied as a reference spectral profile in the subsequent atmospheric spectral analysis and retrieval of NO₂ and CHOCHO. This will provide an idea for solving the problem of cross-interference of strongly absorbing gases in weakly absorbing gases.

We report here how we managed to improve the performance of an aerosol particle counter model TSI3010. Our device is based on a secondhand unit and reuses its core elements (saturator, condenser, optics). We redesigned the electronics and thermal management. Laboratory experiments show that the cutoff diameter was decreased from 10 to 2.5 nm, bringing the B3010 close to more complex and expensive products. These results may help designers and users improve the performance of their devices.

We present a new numerical code to retrieve NO₂ vertical column densities (VCDs) and concentrations from previously retrieved slanted columns from spectroscopic measurements in the visible and ultraviolet spectral ranges in different vertical viewing directions. We use this code on 1.5 years of data from a measurement station located in the south of Mexico City and compare daily and monthly averages to averages of in situ measurements. We show daily NO₂ VCD time series for a few example days.

Imaging spectrometers provide valuable remote measurements of Earth's surface and atmosphere. These measurements rely on computationally expensive radiative transfer models (RTMs). Spectrometers produce too much data to process with RTMs directly, requiring approximations that trade accuracy for speed. We demonstrate that neural networks can quickly emulate RTM calculations more accurately than current approaches, enabling the application of more sophisticated RTMs than current methods permit.

We describe the potential impact of a new, low-cost, portable ground instrument (the mini-LHR) that measures methane and carbon dioxide in the atmospheric column. This region is key in quantifying the global carbon budget but has geographical gaps in measurements left by ground-based networks and space-based observations. A deployment of 50 mini-LHRs would add new data products in the Amazon, the Arctic, and southern Asia and significantly improve knowledge of regional and global carbon budgets.