The nocturnal boundary layer (NBL) budget method enables the quantification of gas fluxes between ecosystems and the atmosphere under nocturnal stable stratification, a condition under which standard approaches struggle. However, up to now the application of the NBL method has been limited by difficulties in obtaining the required measurements. We show how an unmanned aircraft system (UAS) equipped with a carbon dioxide analyser can make this method more accessible.

The study evaluated the performance of a low-cost PM sensor in ambient conditions and calibrated its readings using simple linear regression (SLR), multiple linear regression (MLR), and two more powerful machine-learning algorithms with random search techniques for the best model architectures. The two machine-learning algorithms are XGBoost and a feedforward neural network (NN).

Lightning NO_x has a strong impact on ozone and the hydroxyl radical production. However, the production efficiency of lightning NO_x is still quite uncertain. This work develops the algorithm of estimating lightning NO_x for both clean and polluted regions and evaluates the sensitivity of estimates to the model setting of lightning NO. Results reveal that our method reduces the sensitivity to the background NO₂ and includes much of the below-cloud LNO₂.

We present a new method to derive NO₂ concentrations from satellite observations that uses up to 30 times less spectral information than traditional methods. We tested the method using data from existing instruments OMI and TROPOMI and found our results agree with the reference data to 5 % and 11 %, respectively. Our method could allow for simpler instrument designs that can be used in low-cost constellations of small satellites for air quality monitoring at high spatial and temporal resolution.

In the changing Arctic, quantifying the resulting variability of incoming solar radiation is important to better elucidate the net radiative effect of clouds. As part of a multidisciplinary expedition in the central Arctic held in early summer 2017, a novel network of pyranometers was deployed over an ice floe to investigate the spatiotemporal variability of solar radiation under different sky conditions. This study presents the collected data and an analysis of the spatiotemporal variability.

Clouds play a large role in the way our Earth system distributes energy. The measurement of cloud droplet size distribution (DSD) is one way to connect small-scale cloud processes to scattered radiation. Our small satellite instrument, the Airborne Hyper-Angular Rainbow Polarimeter, is the first to infer DSDs over a wide spatial cloud field using polarized light. This study improves the way we interpret cloud properties and shows that high-quality science does not require a large taxpayer cost.

We present a method of using collocated microwave link instruments to estimate the average size distribution of raindrops along a path of several kilometers. Our method is validated using simulated fields as well as five laser disdrometers installed along a path. We also present preliminary results from an experimental setup measuring at 26 and 38 GHz along a 2.2 km path. We show that a retrieval on the basis of microwave links can be highly accurate, provided the base power level is stable.

The 1.27 μm O₂ dayglow is well-suited for remote sensing in near-space. The main goal of this paper is to discuss the effect of OH radiance on the wind and temperature measurements derived from limb-viewing observations of the O₂ dayglow. It is apparent from the simulations that the presence of OH radiance as an interfering species decreases the wind and temperature accuracy at all altitudes, but this effect can be reduced considerably by improving OH radiance knowledge.

This study is the first assessment and validation of AIRS HDO / H₂O retrieved by optimal estimation. Initial comparisons with in situ measurements from NASA ORACLES are promising: the small bias and consistent rms of AIRS suggest that AIRS has well-characterized HDO / H₂O. This analysis opens the possibility of a new 17-year long-term data record of global tropospheric HDO / H₂O measured from space.

We present a new aerosol profile retrieval algorithm for MAX-DOAS measurements at high-altitude sites and applied to the MAX-DOAS measurements at UFS. The retrieval algorithm is based on a O₄ DSCD lookup table which is dedicated to high-altitude MAX-DOAS measurements. The comparison of retrieved aerosol optical depths (AODs) to sun photometer observations shows good agreement with a correlation coefficient (R) of 0.733 and 0.798 at 360 and 477 nm, respectively.

Black carbon (BC) is an important atmospheric pollutant and can be monitored by instruments called aethalometers. A pragmatic data processing technique called the aethalometer model can be used to apportion aethalometer observations into traffic and woodburning components. We present an exploratory data analysis evaluating the aethalometer model and use the outputs for BC trend analysis across Switzerland. The aethalometer model's robustness and utility for such analyses is discussed.

We present the development and successful field deployment of a new chemical ionization mass spectrometry method capable of fast and high-sensitivity measurements of ozone and nitrogen dioxide in the atmosphere. The sensitivity, precision, and time resolution of the instrument were demonstrated to be sufficient for making deposition flux measurements of ozone from a coastal ocean field site. We propose this instrument will also be well suited for sampling from mobile platforms.

Stratospheric sulfate aerosols increase the Earth's planetary albedo and can lead to significant surface cooling, for example in the aftermath of volcanic eruptions. Their particle size distribution, important for physical and chemical effects of these aerosols, is still not fully understood. The present paper proposes an explanation for systematic differences in aerosol particle size retrieved from measurements made in different measurement geometries and reported in earlier studies.

A new elastic lidar inversion equation is presented. It is based on the backscattering signal from a surface reference target rather than that from a volumetric layer of reference as is usually done. The method presented can be used in the case of airborne elastic lidar measurements or when the lidar–target line is horizontal. Also, a new algorithm is described to retrieve the lidar ratio and the backscattering coefficient of an aerosol plume without any a priori assumptions about the plume.

Methane has high climate warming potential. Sources of methane can be distinguished by the isotopic composition. To investigate the origin of methane, an airborne sampling system has been developed that can take air samples worldwide and at various altitudes. The article shows the performance of the overall system, from taking samples to laboratory analyses. As known methane source, a rewetted peatland site, was studied, and the vertical distribution of the isotopic composition is investigated.

This study investigates how the airflow around wing-mounted instruments on fast-flying aircraft affects aerosol and cloud measurements. It combines airborne data with numerical simulations and shows that particle speed, particle concentration, and shape of water droplets are modified by the airflow. The proposed correction strategy for optical particle counters and optical array probes considers airflow effects and significantly reduces errors of derived ambient aerosol and cloud properties.

Vertical ascent rate Vb of meteorological balloons is sometimes used for retrieving vertical air velocity, an important parameter for meteorological applications. Comparisons with concurrent radar and unmanned aerial vehicle (UAV) measurements of atmospheric turbulence showed that Vb can be increased in turbulent layers due to the probable decrease in the drag coefficient of the balloon. We conclude that Vb can also potentially be used for the detection of atmospheric turbulence.

Gas quantification using the open-path Fourier transform infrared spectrometer (OP-FTIR) is subject to interferences of environmental variables, leading to errors in gas concentration calculations. This study investigated the effects of ambient water vapour content, temperature, path lengths, and wind speed on the quantification of N₂O and CO₂ concentrations, which can help the OP-FTIR users to avoid these errors and improve the precision and accuracy of the atmospheric gas quantification.

In this paper, we present the new moist-air wind tunnel LACIS-T (Turbulent Leipzig Aerosol Cloud Interaction Simulator). It is used to study cloud physical processes in general and interactions between turbulence and cloud microphysical processes in particular. The operating principle of LACIS-T is explained, and the first results are depicted from deliquescence and droplet formation experiments observing clear indications on the effect of turbulence on these microphysical processes.

Here we present the high-humidity tandem differential hygroscopicity analyzer (HHTDMA) and a new method to measure the hygroscopic growth of aerosol particles with in situ restructuring to minimize the influence of particle shape. Our results demonstrate that the HHTDMA system described in this work allows us to determine the thermodynamic characteristics of aqueous solutions with an accuracy close to that obtained by bulk methods.

Direct mercury (Hg) flux studies are crucial to improve our understanding of terrestrial Hg cycling and human Hg exposure. We tested a new system to measure Hg fluxes using the eddy covariance technique. Our Eddy Mercury system revealed a net Hg re-emission flux from a grassland. We concluded that the prevailing dry conditions resulted in low uptake of CO₂ and Hg. Eddy Mercury has the potential to address some of the largest uncertainties in global Hg cycling through long-term flux measurements.

This work reports on the first airborne validation campaign of ESA’s Earth Explorer mission Aeolus, conducted in central Europe during the commissioning phase in November 2018. After presenting the methodology used to compare the data sets from the satellite, the airborne wind lidar and the ECWMF model, the wind results from the underflights performed are analyzed and discussed, providing a first assessment of the accuracy and precision of the preliminary Aeolus wind data.

Discrepancies in hourly shallow cumuli cover estimates can be substantial. Instrument detection differences contribute to long-term bias in shallow cumuli cover estimates, whereas narrow field-of-view configurations impact measurement uncertainty as averaging time decreases. A new tool is introduced to visually assess both impacts on sub-hourly cloud cover estimates. Accurate shallow cumuli cover estimation is needed for model–observation comparisons and studying cloud-surface interactions.

We performed an error analysis of SMILES observations for acetonitrile and a validation using the MLS observations by extracting the coincident points between SMILES and MLS data. The major error sources for the SMILES observations were quantitatively estimated. At upper pressure levels the difference between the two datasets increased because of an uncertainty in MLS observations. The results showed that SMILES has an advantage in measuring acetonitrile in the upper stratosphere and mesosphere.

Pandora NO₂ measurements made at three sites located in the Toronto area are used to evaluate the TROPOspheric Monitoring Instrument (TROPOMI) NO₂ data products, including standard NO₂ and research data developed using a high-resolution regional air quality forecast model. TROPOMI pixels located upwind and downwind from the Pandora sites were analyzed by a new wind-based validation method, which revealed the spatial patterns of local and transported emissions and regional air quality changes.