Volatile organic compounds (VOCs) like scents can appear and disappear quickly. For example, when a bug starts on a tree, the tree releases VOCs that warn the trees around him. Thus, one needs instruments measuring their concentration in real time and identify which VOC is measured. In our study, we compared two instruments doing that, PTR-MS and SIFT-MS. Both work similarly, but we found that the PTR-MS can measure lower concentrations, but the SIFT-MS can identify VOCs better.

We analyse temporal trends in carbon monoxide (CO) detected by the MOPITT satellite instrument over the coastal city of Halifax, Canada. We show that trends in surface level CO differ significantly depending on the data product used (Level 2 or Level 3). This is linked to the different sensitivity with which MOPITT can detect CO at the surface over land and water as well as the differing degree to which the data can be filtered to account for this in the different products.

A thermal desorption–gas chromatography–mass spectrometry method following sorbent tube sampling was developed for the determination of terpenes in gas-phase samples. The main focus was on the analysis of diterpenes, which have been limited in study in gas-phase samples. The analytical figures of merit were fit for purpose (e.g. quantitation limits <10 pptv and reproducibility <10 % for terpenes). Diterpenes could be detected and identified in emissions from spruce and pine samples.

After the Sentinel-5 Precursor satellite launch on 13 October 2017, its single payload, the TROPOspheric Monitoring Instrument (TROPOMI), was tested and calibrated extensively. Changes due to ageing of the instrument and new insights have led to updates to the L1b processor and its calibration key data, leading to improvements of the data quality. Regularly scheduled calibration measurements are used in the nominal operations phase (since 30 April 2018) to correct instrument degradation.

In this paper we quantify (using a statistical model) the probability of decomposition of a representative class of HOM clusters in an APi-TOF mass spectrometer. This is important because it quantifies the systematic error of measurements in a APi-TOF MS due to cluster decomposition. The results (specific for our selected clusters) show that decomposition is negligible, provided their bonding energy is large enough to allow formation in the atmosphere in the first place.

The accurate measurement of greenhouse gases and their vertical distribution in the atmosphere is significant to the study of climate change and satellite remote sensing. Carbon dioxide and methane between 0.6 and 7 km were measured by the aircraft King Air 350ER in Jiansanjiang, northeast China, on 7–11 August 2018. The profiles show strong variation with the altitude and time, so the vertical structure of gases should be taken into account in the current satellite retrieval algorithm.

Three-dimensional (3D) wind motions play a major role in driving the life cycle of clouds. In this pilot study we have developed a technique to measure the 3D winds in clouds, using a shipborne Doppler cloud radar on a stabilized platform. The stabilized platform is driven to point in a series of predefined directions to collect the required measurements. Comparisons with radiosondes demonstrate that accurate 1 min resolution 3D wind motions can be obtained from this instrumental setup.

Radiosondes are one of the primary sources of upper-air data for weather and climate monitoring. In the last two decades, technological progress made available automated radiosonde launchers (ARLs), which are able to replace measurements typically performed manually. This work presents a comparative analysis of the technical performance of the ARLs currently available on the market and contribute to define a strategy to achieve the full traceability of the ARL products.

A novel constant-pressure-inlet design for use in airborne aerosol particle mass spectrometry – an aerodynamic lens focuses aerosol particles into a vacuum chamber – is presented. The pressure of a few hectopascals at the lens is precisely controlled over a large flight altitude range up to 21 km. The constant pressure is achieved by changing the inner diameter of a properly scaled flexible O-ring acting as a critical orifice. Particle transmission at various inlet pressures is characterized.

Polar stratospheric clouds (PSCs) play a key role in polar ozone depletion in the stratosphere. In this paper, we explore the potential of applying machine learning (ML) methods to classify PSC observations of infrared spectra to classify PSC types. ML methods have proved to reach results in line with those obtained using well-established approaches. Among the considered ML methods, random forest (RF) seems to be the most promising one, being able to produce explainable classification results.

A common way of measuring trace gases in the atmosphere is chemical ionization mass spectrometry. One large drawback of these instruments is that they require radioactive ion sources. In this work we demonstrate a simple ion source that uses a small krypton lamp that can be used to replace a radioactive source.

In the Arctic, in situ measurements are sparse and standard remote sensing retrieval methods have problems. We present advances in a retrieval algorithm for vertically integrated water vapour tuned for polar regions. In addition to the initial sensor used (AMSU-B), we can now also use data from the successor instrument (MHS). Additionally, certain artefacts are now filtered out. Comparison with radiosondes shows the overall good performance of the updated algorithm.

A gas flow system coupled with a microreactor for X-ray microspectroscopy is presented. Its core objective is to mimic the atmospheric processing of aerosol particles under laboratory conditions in a controlled gas-phase environment and allow in situ observations with high spatial and chemical resolution. We here emphasize its analytical capabilities and show initial results from hydration–dehydration experiments and the observation of water ice at low temperature and high relative humidity.

We validate the TROPOMI HCHO product with ground-based FTIR (Fourier-transform infrared) measurements from 25 stations. We find that TROPOMI overestimates HCHO under clean conditions, while it underestimates it at high HCHO levels. Both TROPOMI precision and accuracy reach the pre-launch requirements, and its precision can even be 2 times better. The observed TROPOMI seasonal variability is in agreement with the FTIR data. The TROPOMI random uncertainty and data filtering should be refined.

This paper is submitted as part of my thesis project. It highlights the importance of ground-based measurements for future satellite validations. This paper represents the characteristics of a new prototype called CHRIS, which is the MIR version of the EM27/SUN. Our primary concern is the exploitation of the data of the MAGIC campaign, which is a French initiative in collaboration with the CoMet project, to monitor greenhouse gases.

In this paper we show that chemical similarities between the seed particle material and the working fluid have an impact on the detection efficiency of commonly used CPCs. A remarkable set of CPCs, including the newly developed V-WCPC 3789, was tested. Among others, reproducibly generated organic seeds based on beta-caryophyllene were used. Theoretical simulations of supersaturation profiles were successfully linked to measured data.

Atmospheric mineral dust influences Earth's radiative budget, has adverse health effects, and affects regulatory PM₁₀ concentrations. We present a highly time resolved online technique for quantification of mineral dust concentration in ambient air. The technique uses a virtual impactor to concentrate coarse particles, where absorption is then measured using a filter photometer. The method was tested in the field at a regional background site on Cyprus.

Commercial microwave link (CML) networks can be used to estimate path-averaged rain rates. This study evaluates the ability of convolutional neural networks to distinguish between wet and dry periods in CML time series data and the ability to transfer this detection skill to sensors not used for training. Our data set consists of several months of data from 3904 CMLs covering all of Germany. Compared to a previously used detection method, we could show a significant increase in performance.

It is well known that the atmospheric boundary layer is under-sampled in the vertical dimension. Recently, weather-sensing uncrewed aerial systems (WxUAS) have created new opportunities to sample this region of the atmosphere. This study compares a WxUAS developed at the University of Oklahoma to ground-based remote sensing and radiosondes. We find that overall the systems generally agreed well both thermodynamically and kinematically. However, there is still room to improve each system.

Most air quality information comes from accurate but expensive instruments. These can be supplemented by lower-cost sensors to increase the density of ground data and expand monitoring into less well-instrumented areas, like sub-Saharan Africa. In this paper, we look at how low-cost sensor data can be combined with satellite information on air quality (which requires ground data to properly calibrate measurements) and assess the benefits these low-cost sensors provide in this context.

One of the main limitations for long-term space-based measurements is instrument degradation. We present an optimisation of the degradation correction approach (Krijger et al. 2014) for SCIAMACHY on-board Envisat, focusing on the improvement of the solar spectral irradiance data. The main achievement of this study is the successful integration of SCIAMACHY’s internal white light source (WLS) into the existing degradation model and the characterisation of WLS ageing in space.

Clouds reflect sunlight unevenly, which makes it difficult to quantify the portion reflected back to space via satellite observation. To improve quantification, we propose a new statistical model that incorporates more satellite-inferred cloud and atmospheric properties than state-of-the-art models. We use concepts from radiative transfer theory that we statistically optimize to fit observations. The new model often explains past satellite observations better and predicts reflection plausibly.

We present some results about ammonia pollution because NH₃, mainly emitted by agricultural activities, is a precursor of fine particles. This study is based on the first multiyear time series (2009–2017) of atmospheric NH₃ ground-based measurements over the Paris megacity. This pollutant varies seasonally by 2 orders of magnitude, especially in spring. We highlight that this kind of instrument could be easily installed and is very useful for analyzing NH₃ in other megacities or source regions.

Biosphere–atmosphere gas exchange (flux) measurements of carbonyl sulfide (COS) are becoming popular for estimating biospheric photosynthesis. To compare COS flux measurements across different measurement sites, we need standardized protocols for data processing. We analyze how various data processing steps affect the calculated COS flux and how they differ from carbon dioxide (CO₂) flux processing steps, and we aim to settle on a set of recommended protocols for COS flux calculation.

We present a procedure for both the geometric and absolute radiometric characterization of the weather-proof RGB camera HaloCam_RAW, which is part of our automated halo observation system HaloCam, designed for the quantitative analysis of halo displays. By comparing the calibrated HaloCam_RAW radiances of a 22° halo scene with radiative transfer simulations, we demonstrate the potential of developing a retrieval method for ice crystal properties, such as size, shape, and surface roughness.

MAX-DOAS is a technique that can be used to measure pollutant concentrations and vertical profiles in the atmosphere via remote sensing of sky-scattered light with a telescope. Measuring SO₂ is particularly challenging because of low light intensities in regions where SO₂ absorbs solar radiation. Here, we performed experiments that document inaccuracies in these measurements as a function of spectral fitting windows. We provide recommendations for measuring SO₂ with greater accuracy.

This paper assesses the performance of observed XCO₂ from the GOSAT and OCO-2 satellites in capturing simulated XCO₂ from the NOAA Carbon Tracker model over Africa. These satellite observations and Carbon Tracker mixing ratios near the surface are also compared to available in situ CO₂ flask data from Assekrem, Algeria; Mt. Kenya; Gobabeb, Namibia; and Cape Town; as well as to data off the coast at Seychelles, Ascension Island, and at Izana, Tenerife.

Use of VIIRS+CrIS fusion products, which provide VIIRS with MODIS-like IR sounding channels, improves cloud mask, cloud phase, and cloud top height retrievals when compared to those using VIIRS data only. NOAA CLAVR-x cloud retrievals for both S-NPP and NOAA-20 data are evaluated through comparisons to the CALIPSO v4 and MODIS Collection 6.1 cloud products. Cloud height retrievals show significant improvement for semitransparent ice clouds, with a reduction in retrieval uncertainties.

For reliable measurements of CO₂ mole fractions and its stable isotope composition in air samples, one needs to carefully dry them during collection. Here we describe evaluation of a portable, consumable-free and power-free Nafion-based drying system that is currently being used for sample collection over the Amazon. Laboratory tests indicate that this Nafion-based system does not influence the mole fraction measurements of CH₄, CO, N₂O, SF₆, and CO₂ and the stable isotope composition of CO₂.

Soil emissions of nitrous oxide (N₂O), a potent greenhouse gas, are highly variable over space and time. Existing approaches for automated N₂O emission measurements are costly and often incompatible with flooded soils. We describe and validate a robust and low-cost apparatus for replicated measurement of soil N₂O emissions at subdaily resolution over large spatial gradients (> 100 m). High-frequency measurements are critical for constraining and mitigating the soil N₂O source.

The retrieved CH₄ and N₂O VMR and column amounts from Addis Ababa, tropical site, are found to exhibit very good agreement with all coincident satellite observations (MIPAS, MLS, and AIRS). Furthermore, the bias obtained from the comparison is comparable to the precision of FTIR measurement, which allows the use of data in further scientific studies as it represents a unique environment of tropical Africa, a region poorly investigated in the past.