Recent  

This study discusses the morning and afternoon distribution of NO₂ emissions in large cities and industrial areas in South Korea, one of the largest NO₂ emitters around the world, using GeoTASO, an airborne remote sensing instrument developed to support geostationary satellite missions. NO₂ measurements from GeoTASO were compared with those from ground-based remote sensing instruments including Pandora and in situ sensors.

In this work, we analyze polarized cloudbow observations by the airborne camera system specMACS to retrieve the cloud droplet size distribution defined by the effective radius (r_eff) and the effective variance (v_eff). Two case studies of trade-wind cumulus clouds observed during the EUREC⁴A field campaign are presented. The results are combined into maps of r_eff and v_eff with a very high spatial resolution (100 m × 100 m) that allow new insights into cloud microphysics.

Methane and carbon monoxide are important constituents of the atmosphere in the context of climate change and air pollution. We present the latest advances in the TROPOMI/WFMD algorithm to simultaneously retrieve atmospheric methane and carbon monoxide abundances from space. The changes in the latest product version are described in detail, and the resulting improvements are demonstrated. An overview of the products is provided including a discussion of annual increases and validation results.

SMILE (a spectral misalignment in which a shift in the center wavelength appears as a distortion in the spectral image) was detected during our recent work. To evaluate how it affects the cloud retrieval products, we did a simulation of EarthCARE-MSI forward radiation, evaluating the error in simulated scenes from a global cloud system-resolving model and a satellite simulator. Our results indicated that the error from SMILE was generally small and negligible for oceanic scenes.

We evaluate the theoretical ability of the upcoming MicroCarb satellite to estimate urban CO₂ emissions over Paris and London. We explore the relative performance of alternative two-sweep and three-sweep city observing modes and take into account the impacts of cloud cover and urban biological CO₂ fluxes. Our results find both the two-sweep and three-sweep observing modes are able to reduce prior flux errors by 20 %–40 % depending on the prevailing wind direction and cloud coverage.

Accurate knowledge of the planetary boundary layer height (PBLH) is essential to study air pollution. However, PBLH observations are sparse in space and time, and PBLHs used in atmospheric models are often inaccurate. Using PBLH observations from the Aircraft Meteorological DAta Relay (AMDAR), we present a machine learning framework to produce a spatially complete PBLH product over the contiguous US that shows a better agreement with reference PBLH observations than commonly used PBLH products.

Storm activity is sometimes associated with the generation of ionizing radiation. Our motivation for performing this research was to understand its origin. Using measuring cars fitted with new instruments, it was found that the duration of lightning is longer than generally thought. In most cases, lightning occurs only inside the cloud; however, rarely, it is also visible outside the cloud. In such cases, the course of emission over time can be used to assume what it looks like inside the cloud.

During a 5-week comparison campaign, we tested two set-ups to measure half hourly ammonia fluxes. The eddy covariance and flux gradient systems showed very similar results when the upwind terrain was both homogeneous and free of obstacles. We discuss the technical performance and practical limitations of both systems. Measurements from these instruments can facilitate the study of processes behind ammonia deposition, an important contributor to eutrophication and acidificationin natural areas.

An increased social environmental awareness requires the monitoring of greenhouse gases (GHGs). We report on the development of two sampling devices (which can be mounted to a drone) and the subsequent measurement setup to analyse these gases. The functionality of the presented system was tested in the field, and the results emphasised the functionality of the sampling and measurement setup, demonstrating that it is a viable tool for monitoring GHGs and identifying their emission sources.

Profile observations of the atmospheric boundary layer now allow for layer heights and characteristics to be derived at high temporal and vertical resolution. With novel high-density ground-based remote-sensing measurement networks emerging, horizontal information content is also increasing. This review summarises the capabilities and limitations of various sensors and retrieval algorithms which need to be considered during the harmonisation of data products for high-impact applications.

Nitrogen dioxide (NO₂) is an important trace gas for both air quality and climate. NO₂ affects satellite ocean color products. A new ocean color instrument – OCI (Ocean Color Instrument) – will be launched in 2024 on a NASA satellite. We show that it will be possible to measure NO₂ from OCI even though it was not designed for this. The techniques developed here, based on machine learning, can also be applied to instruments already in space to speed up algorithms and reduce the effects of noise.

Vertical observation of volatile organic compounds (VOCs) is essential to study the spatial distribution and evolution patterns of VOCs in the planetary boundary layer (PBL). This paper describes multi-channel whole-air sampling equipment onboard an unmanned aerial vehicle (UAV) for near-continuous VOC vertical observation. Vertical profiles of VOCs and trace gases during the evolution of the PBL in south-western China have been successfully obtained by deploying the newly developed UAV system.

The T-matrix theory was used to compute the backscatter and depolarization of mixed-phase PSC, assuming that particles are solid (NAT or possibly ice) above a threshold radius R and liquid (STS) below, and a single shape is common to all solid particles. We used a dataset of coincident lidar and balloon-borne backscattersonde and OPC measurements. The agreement between modelled and measured backscatter is reasonable and allows us to constrain the parameters R and AR.

We report in situ measurements of air pollutant concentrations within the planetary boundary layer on board a Zeppelin NT in Germany. We highlight the in-flight evaluation of electrochemical sensors that were installed inside a hatch box located on the bottom of the Zeppelin. Results from this work emphasize the potential of these sensors for other in situ airborne applications, e.g., on board unmanned aerial vehicles (UAVs).

Measurements of atmospheric O₂ can help constrain the carbon cycle processes and quantify fossil fuel CO₂ emissions; however, measurement of atmospheric O₂ is very challenging, and existing analysers are complex systems to build and maintain. We have tested a new O₂ analyser (Picarro Inc. G2207-i) in the laboratory and at Weybourne Atmospheric Observatory. We have found that the G2207-i does not perform as well as an existing O₂ analyser from Sable Systems Inc.

Influenced by the representativeness of ice crystal scattering models, the existing terahertz ice cloud remote sensing inversion algorithms still have significant uncertainties. We developed an ice cloud remote sensing retrieval algorithm of the ice water path and particle size from aircraft-based terahertz radiation measurements based on the Voronoi model. Validation revealed that the Voronoi model performs better than the sphere and hexagonal column models.

The depolarization ratio of hematite, silica, Arizona and Asian dust is evaluated in a lab with a π-polarimeter operating at lidar 180 ° and at (355, 532) nm wavelengths. The hematite depolarization equals (10±1) % at 355 nm for coarser particles, while that of silica is (33±1) %. This huge difference is explained by accounting for the high imaginary part of the hematite complex refractive index, thus revealing the key role played by light absorption in mineral dust lidar depolarization.

We present a new method to extract the gases from ice cores and measure their greenhouse gas composition. The ice is sublimated continuously with a near-infrared laser, releasing the gases, which are then analyzed on a laser absorption spectrometer. The main advantage over previous efforts is a low effective resolution of 1–2 cm. This capability is crucial for the analysis of highly thinned ice, as expected from ongoing drilling efforts to extend ice core history further back in time.

Strateole-2 is an French–US initiative designed to study atmospheric events in the tropical upper troposphere–lower stratosphere. In this work, data from several superpressure balloons, capable of staying aloft at an altitude of 18–20 km for over 3 months, were used. The present article describes methods to detect the occurrence of atmospheric turbulence – one efficient process impacting the properties of the atmosphere composition via stirring and mixing.

Weather radar data are the backbone of a lot of meteorological products. In order to obtain a better low-level coverage with radar data, additional systems have to be included. The frequency range in which radars are allowed to operate is limited. A potential radar-to-radar interference has to be avoided. The paper derives guidelines on how additional radars can be included into a C-band weather radar network and how interferences can be avoided.

The ground-based FTIR measurements at Xianghe provide carbon monoxide (CO), acetylene (C₂H₂), ethane (C₂H₆), formaldehyde (H₂CO), and hydrogen cyanide (HCN) total columns between June 2018 and November 2021. The retrieval strategies, information, and uncertainties of these five important trace gases are presented and discussed. This study provides insight into the time series, variations, and correlations of these five species in northern China.

Atmospheric networks are used for monitoring air quality and greenhouse gases and can provide essential information about the sources and sinks. The design of the network, specifically where to place the observations, is a critical question in order to maximize the information provided while minimizing the cost. Here, a novel method of designing atmospheric networks is presented with two examples, one on monitoring sources of methane and the second on monitoring fossil fuel emissions of CO₂.

We present a new, highly sensitive technique for measuring atmospheric ammonia, an important trace gas that is emitted mainly by agriculture. We deployed the instrument on an aircraft during research flights over rural Oklahoma. Due to its fast response, we could analyze correlations with turbulent winds and calculate ammonia emissions from nearby areas at 1 to 2 km resolution. We observed high spatial variability and point sources that are not resolved in the US National Emissions Inventory.

Optical receivers for solar spectral actinic radiation are designed for angle-independent sensitivities within a hemisphere. Remaining imperfections can be compensated for by receiver-specific corrections based on laboratory characterizations and radiative transfer calculations of spectral radiance distributions. The corrections cover a wide range of realistic atmospheric conditions and were applied to ground-based and airborne measurements in a wavelength range 280–660 nm.

This study describes a new technique to measure total gaseous chlorine, which is the sum of gas-phase chlorine-containing chemicals. The method converts any chlorine-containing molecule to hydrogen chloride that can be detected in real time using a cavity ring-down spectrometer. The new method was validated through laboratory experiments, as well as by making measurements of ambient outdoor air and indoor air during cleaning with a chlorine-based cleaner.

Variations in brightness in radiance measurements cause errors that can be mitigated with hardware that scrambles the pattern of the incoming light. GeoCarb took this route to minimize this source of errors, but lab testing determined that the solution chosen was too sensitive to the the polarization of the incoming light. Modeling found that this was a predictable result of using gold coatings in the design, which is typical of spaceflight optical instruments.

This study aims to verify that a partly defective hyperspectral measurement can be successfully reproduced with concise machine learning models coupled with principal component analysis. Evaluation of the approach is performed with radiances and retrieval results of ozone and cloud properties. Considering that GEMS is the first geostationary UV–VIS hyperspectral spectrometer, we expect our findings can be introduced further to similar geostationary environmental instruments to be launched soon.

We assessed five pairs of co-located reference and low-cost sensor data sets (PM_2.5, O₃, NO₂, NO, and CO) to make recommendations for best practices regarding the field calibration of low-cost air quality sensors. We found diminishing improvements for calibration periods longer than about 6 weeks for all sensors and that co-location can be minimized if the period is strategically selected and monitored so that the calibration period is representative of the desired measurement setting.

Atmospheric concentrations and source apportionment (SA) of black carbon (BC) and CO₂ were determined in an urban environment during a heating season. BC particles were attributed to two major sources: traffic and heating. The BC SA was implemented by an Aethalometer model used for the SA of CO₂ supposing that the source-specific CO₂ components are correlated with the corresponding BC. Source-specific emission factors were determined as a ratio of corresponding BC and CO₂ components.

A small percentage of data from the Orbiting Carbon Observatory-3 (OCO-3) instrument has been shown to have a geometry-related bias in the earliest public data release. This work shows that the bias is due to a complex interplay of aerosols and viewing geometry and is largely mitigated in the latest data version through improved bias correction and quality filtering.

Photochemically induced changes in mesospheric O₃ concentration at twilight can cause asymmetry in the distribution along the line of sight of solar occultation observations that must be considered in the retrieval algorithm. Correction factors developed from diurnal photochemical model simulations were used to modify the archived SAGE III/ISS mesospheric O₃ concentrations. For June 2021 the bias caused by the neglect of diurnal variations is over 30% at 64 km altitude and low latitudes.

We present a methane flux rate retrieval methodology using the Sentinel-2 mission, validating the algorithm for different scenes and plumes. The detection limit is 1000–2000 kg h⁻¹ for homogeneous scenes and temporally invariant surfaces and above 5000 kg h⁻¹ for heterogeneous ones. Dominant quantification errors are wind-related or plume mask-related. For heterogeneous scenes, the surface structure underlying the methane plume can become a dominant source of uncertainty.

In this work, 2.5 years of TROPOMI/S5P Total Column Water Vapor (TCWV) observations retrieved from the blue wavelength band are validated against co-located precipitable water measurements from NASA AERONET, which uses Cimel Sun photometers globally. Overall, the TCWV product agrees well on a global scale with the ground-based dataset (Pearson correl. coefficient 0.909) and has a mean relative bias of −2.7 ± 4.9 % with respect to the AERONET observations for moderate albedo and cloudiness.

The true eddy accumulation (TEA) method enables measuring atmospheric exchange with slow-response gas analyzers. TEA is formulated assuming ideal conditions with a zero mean vertical wind velocity during the averaging interval. This core assumption is rarely valid under field conditions. Here, we extend the TEA equation to accommodate nonideal conditions. The new equation allows constraining the systematic error term in the measured fluxes and the possibility to minimize or remove it.

A new micrometeorological method to measure atmospheric exchange is proposed, and a prototype sampler is evaluated. The new method, called short-time eddy accumulation, is a variant of the eddy accumulation method, which is suited for use with slow gas analyzers. The new method enables adaptive time-varying accumulation intervals, which brings many advantages to flux measurements such as an improved dynamic range and the ability to run eddy accumulation in a continuous flow-through mode.

This work examined the phase partitioning behaviors of organic compounds at hourly resolution in ambient conditions with the use of the CHemical Analysis of aeRosols ONline (CHARON) inlet coupled to a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS). Properly accounting for the neutral losses of small moieties during the molecular feature extraction from PTR mass spectra could significantly reduce uncertainties associated with the gas–particle partitioning measurements.