The UVA spectrometer is the latest instrumental addition to the spectrometric fluorescence and Raman lidar RAMSES. The redesigned receiver and the data analysis of the fluorescence measurement are described. Furthermore, the effect of aerosol fluorescence on humidity measurements is studied. It turns out that Raman lidars equipped with a spectrometer show superior performance over those with one discrete fluorescence detection channel only. The cause is variability in the fluorescence spectrum.

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.

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.

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.

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.

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.

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.

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.

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.